124-21 photocycloadditions of 6 -unsaturated...
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124-21 PHOTOCYCLOADDITIONS OF a, 6 -UNSATURATED LACTONES WITH ACRYLONITRILE AND ITS a-CHLORO AND a-ACETOXY DERIVATIVES
J e a n P i e r r e L a f o n t a i n e
B.Sc, , B i s h o p s U n i v e r s i t y , 1 9 8 1
A T H E S I S SUBMITTED I N P A R T I A L FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER O F S C I E N C E
@ Jean
SIMON
t h e Department
o f
C h e m i s t r y
P i e r r e L a f o n t a i n e 1 9 8 7 FRASER U N I V E R S I T Y
June 1 9 8 7
A l l r i g h t s r e s e r v e d . T h i s work may n o t be reproduced i n w h o l e o r i n p a r t , by p h o t o c o p y
o r by o t h e r means, w i t h o u t p e r m i s s i o n of t h e a u t h o r ,
-ii-
APPROVAL
Name : J,P. Lafontaine
Degree: Master of Science
T i t l e of Thesis: [ 2 + 2 ] ~hotocycloadditions of cr , ,8 -Unsaturated Lactones w i t h
Acrylonitri le and i ts a-Chloro and tr-Acetoxy Derivatives
Examining Committee:
Chairman: Dr. T. Bell
D r . A.C. -OehlschJ#ger, Senior Supervisor
\ - Dr. K.N. \Slesso$
-
1
Dr. R . i i ~ ~ ' b % ~ o y - '
~r*. ~ n i a u , Internal Examiner
4
Date Approved: k/ 2 7, /ff7
PART l AL COPYRIGHT LICENSE
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l i b r a r y o f any o ther un ive rs i t y , o r o the r educational I n s t i t u t i o n , on
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f o r m u l t i p l e copying o f t h i s work f o r scho la r l y purposes may be granted
by me o r the Dean o f Graduate Studies. I t i s understood t h a t copying-
o r p u b l i c a t i o n o f t h i s work f o r f i n a n c i a l ga in sha l l not be allowed
wi thout my w r i t t e n permission.
Author:
A B S r n C T
The [ 2 + 2 ] p h o t o c y c l o a d d i t i o n s of s e v e r a l
a , $ -unsa tu ra t ed Y and 6 l a c t o n e s w i t h a c r y l o n i t r i l e
and i ts a -acetoxy and a - c h l o r o d e r i v a t i v e s were
i n v e s t i g a t e d . I t was found t h a t t h e r e a c t i o n s were b e s t
performed i n a c e t o n i t r i l e and t h a t i r r a d i a t i o n through a
Vycor o r Q u a r t z f i l t e r was r e q u i r e d .
S e v e r a l t r i p l e t s t a t e s e n s i t i z e r s were i n v e s t i g a t e d
and found t o r e a c t more q u i c k l y t h a n t h e 6 l a c t o n e s wi th
t h e o l e f i n s s t u d i e d . T h i s p r e c l u d e d t h e i r u se t o promote
t h e [ 2 + 2 1 c y c l o a d d i t i o n .
The 6 l a c t o n e s s t u d i e d underwent c y c l o a d d i t i o n wi th
a c r y l o n i t r i l e and its a - c h l o r o and a -ace toxy d e r i v a t i v e s
t o g i v e m i x t u r e s of t h e two d i a s t e r e o m e r i c 6 adduc t s i n
moderate y i e l d s . These a d d u c t s were shown t o be
p h o t o s t a b l e b u t were r e a d i l y ep imer ized w i t h a lkox ides .
The Y l a c t o n e s s t u d i e d underwent c y c l o a d d i t i o n wi th
a c r y l o n i t r i l e t o g i v e m i x t u r e s of f o u r 1:l adduc t s which
were on ly p a r t i a l l y r e s o l v a b l e by chromatography. These
a d d u c t s were shown t o be p h o t o s t a b l e b u t were decomposed
by a l k o x i d e s . The Y l a c t o n e s d i d n o t undergo
p h o t o a d d i t i o n w i t h a - c h l o r o o r a -ace toxy a c r y l o n i t r i l e .
Molecular mechanics ( M M - 2 ) c a l c u l a t i o n s were
petformed on s e v e r a l sys tems t o de t e rmine t h e r e l a t i v e
s t r a i n e n e r g y be tween d i f f e r e n t i s o m e r s of t h e a d d u c t s .
E q u i l i b r i u m c o n c e n t r a t i o n s were c a l c u l a t e d f rom t h e MM-2
c a l c u l a t e d e n e r g i e s and found t o b e i n good ag reemen t w i t h
t h o s e o b t a i n e d i n base e q u i l i b r i a t i o n e x p e r i m e n t s .
V i c i n a l h y d r o g e n c o u p l i n g c o n s t a n t s (nmr) d e r i v e d from
MM-2 c a l c u l a t e d d i h e d r a l a n g l e s were found
t o be i n good a g r e e m e n t w i t h e x p e r i m e n t a l l y d e t e r m i n e d
v a l u e s .
ACKNOWLEDGEHENTS
I would l i k e t o acknowledge t he help and support
provided by t he following people. Dr. A.C. Oehlschlager,
Dr. B.D. Johnston, Dr. H.D. P ierce , Dr. J , Mil lar , Dr. E.
Czyzewska and Dr. B.M. Pinto.
I would e spec i a l l y l i k e t o thank
D r . A.C. Oehlschlager f o r the enthusiasm, ideas and
pat ience he provided. I would a l s o l i k e t o thank
M. Tracey and G . Owens f o r the exce l l en t spectroscopic
se rv ices , and M.K. Yang f o r the elemental analys is .
TABLE OF CONTENTS
Abstract
Acknowledgements
List of Tables
List of Schemes and Figures
Introduction
Results and Discussion
Experimental
References
iii
v
vii
viii
L I S T OF TABLES
Table 1
Paqe
Summary of Reactions of 6 -Lactones
Table 2 Summary of M M 2 Calculat ions f o r 6-Lactones 18
Table 3 Calculated Equilibrium Populations
Table 4 - Table 5 -
Summary of Experimental NMR Chemical
Summary of React ions of Y -Lactones
S h i f t s
Table 6 Summary of M M 2 Calculat ions f o r Y-Lactones 28 - Table 7 U.V. Spec t ra l Parameters
Figure 1
Scheme 1
Scheme 2
Scheme 3
Scheme 4
Scheme 5
Fiqure 2
Figure 3
Fiqure 4
Scheme 6
Scheme 7
Scheme 8
Scheme 9
Fiqure 5
Scheme 10
Scheme 11
LIST OF SCHEMES AND FIGURES
Structure of Lineatin (1) - Silverstein's Synthesis of Lineatin
Mori's Synthesis of Lineatin
Mori's Synthesis of Lineatin
White's Synthesis of Lineatin
Weiler Is Synthesis of Lineatin
Mechanism of [2+2] Photocycloaddition
Mechanism of Regiochemical Control
Polarity of Olef ins
Photoaddition of Acrylonitrile to 2-Cyclohexenone
Photoaddition of Acrylonitrile to 2-Cyclohexenone
Photoaddition of Acrylonitrile to 2-Acetoxy-3-methyl-2-cyclopentenone
Retrosynthetic Analysis of Lineatin
Structure of Lactones 6-9 - - Photoaddition of Acrylonitrile to Anhydromevalonolactone (6) - Base Isomerization of 10 and 11 - -
Page
1
L i s t of Schemes and F i g u r e s (cont'd)
Scheme 12
Scheme 13
Fiqure 6
Scheme 14
Scheme 15
Scheme 16
Figure 7
Photoaddition of a-Chloro and a-Acetoxyacrylonitrile to Anhydromevalonolactone (5)
Photoaddition of Acrylonitrile and its a-Chloro and a -Acetoxy Derivatives to 2-Pentenolide (1)
Bicyclic Numbering System
Photoaddition of Acrylonitrile to 2-Butenolide (8)
Photoaddition of Acrylonitrile to 2,3,3-Trimethyl-2-buten-1,4-olide (2)
Synthesis of 2,3,3-Trimethlyl-2-buten- l,4-olide (2) Photolysis Apparatus
-1-
INTRODUCTION
The [ 2 + 2 ] p h o t o c y c l o a d d i t i o n of a , B - u n s a t u r a t e d
k e t o n e s w i t h o l e f i n s is a v a l u a b l e s y n t h e t i c r o u t e t o a
v a r i e t y of b i c y c l o [ n . 2 . 0 ] f u s e d r i n g s y s t e m s . Many of
t h e s e r e a c t i o n s h a v e been a p p l i e d t o t h e t o t a l s y n t h e s i s
of n a t u r a l p r o d u c t s l - Our i n t e r e s t i n d e v e l o p i n g a n
e f f i c i e n t s y n t h e t i c r o u t e t o ( + ) l i n e a t i n ( A ) , t h e
a g g r e g a t i o n pheromone o f t h e a m b r o s i a b e e t l e Trypodendron
l i n e a t u r n ( 0 l i v i e r ) 2 r 3 , l e d u s t o i n v e s t i g a t e t h e p o t e n t i a l
of t h i s r e a c t i o n i n t h e e l a b o r a t i o n o f t h e c a r b o n s k e l e t o n
of t h i s pheromone.
Figure 1 : Lineatin(L)
The u n u s u a l t r i c y c l i c acetal s t r u c t u r e of l i n e a t i n
h a s evoked c o n s i d e r a b l e s y n t h e t i c i n t e r e s t and t h e r e have
been a number o f r o u t e s reported3'11, i n c l u d i n g s e v e r a l
u t i l i z i n g a [ 2 + 2 ] p h o t o a d d i t i o n t o c o n s t r u c t t h e
c y c l o b u t a n e r i n g 3 t 4 , 6 ~ 8 .
The f i r s t p h o t o c h e m i c a l r o u t e t o r acemic l i n e a t i n was
r e p o r t e d by S i l v e r s t e i n and c o w o r k e r s 3 and is d e p i c t e d i n
Scheme 1. T h i s r o u t e p r o d u c e d o n l y microgram amounts of
impure l i n e a t i n , p a r t l y due t o t h e poor r e g i o s e l e c t i v i t y
i n the photoaddit ion of v inyl a c e t a t e t o
anhydromevalonolactone ( 6 ) . -
Scheme 1:
Two o the r photochemical r ou t e s were subsequently
developed by ~ o r i 4 and a r e depic ted i n Schemes 2 and 3 .
The route ou t l i ned i n Scheme 2 is twelve s t e p s and has
only produced milligram amounts of 1. One of the
p r o h i b i t i v e f e a t u r e s of t h i s scheme was t he poor
r e g i o s e l e c t i v i t y i n the photoaddi t ion of vinyl a c e t a t e t o
- t he s u b s t i t u t e d cyclopentene. The mixture of isomeric
a c e t a t e s obtained proved t o be inseparab le u n t i l a f t e r
k e t a l i z a t i o n and oxidat ion t o t h e cyclobutanone. T h i s
route gave a 2.5% y i e l d of t h e bicyclo[3.2.0lbutanone
which had the r equ i red regiochemis t ry f o r e l abora t ion
t o - 1.
Scheme 2:
isomers
I n an a t t empt t o circumvent t h e problem of poor
r e g i o s e l e c t i v i t y t h e Japanese workers developed the route
shown i n Scheme 3 . The 3:2 mixture of isomeric a c e t a t e s
. t h a t was produced v i a t h i s rou te a l s o proved t o be
inseparable . The problem was unexpectedly solved when the
undesired 6-regioadduct underwent a r e t r o a l d o l r eac t ion
dur ing t h e subsequent n i t rosa t ion- reduc t ion . T h i s
e n a b l e d t h e i n v e s t i g a t o r s t o o b t a i n t h e d e s i r e d p r o d u c t i n
4 .8% y i e l d which was e l a b o r a t e d t o i n 0.8% o v e r a l l
y i e l d .
Scheme 3:
A d i f f e r e n t s t r a t e g y was used by Whi te and coworkers6
and is summarized i n Scheme 4 . Whi te , e t a 1 hoped t o
c i rcumvent t h e p rob lems o f p o o r r e g i o c h e m i c a l c o n t r o l
d u r i n g t h e p h o t o a d d i t i o n of a k e t e n e e q u i v a l e n t by u s i n g
a c e t y l e n e and i n t r o d u c i n g a f u n c t i o n a l i t y a t C 7
r e g i o s p e c i f i c a l l y by u s e of h i n d e r e d o rganoboranes . I t
was found, however, t h a t t h e c y c l o b u t e n e r e s i s t e d
h y d r o b o r a t i o n by d i s i a m y l b o r a n e and o t h e r h i n d e r e d
b o r a n e s . Use of d i b o r a n e i t se l f g a v e a 3 : l m i x t u r e of t h e
r e g i o i s o m e r i c a l c o h o l s . F o r t u n a t e l y , it was u n n e c e s s a r y
t o s e p a r a t e t h e m i x t u r e as t h e l ess s t e r i c a l l y h i n d e r e d
a l c o h o l underwent r e a c t i o n w i t h t o s y l c h l o r i d e much f a s t e r
t h a n t h e more h i n d e r e d i somer and t h e r e s u l t i n g t o s y l a t e
was e a s i l y s e p a r a t e d from u n r e a c t e d a l c o h o l . T h i s r o u t e
r e s u l t e d i n a s e v e n s t e p s e q u e n c e w i t h a n o v e r a l l y i e l d
o f 14%.
Scheme 4:
The l a t e s t s y n t h e s i s of l i n e a t i n i n v o l v i n g a [ 2 + 2 ]
p h o t o a d d i t i o n was r e p o r t e d by w e i l e r 8 e t a 1 i n 1981 and is
. . -6- . -
depicted in scheme- 5. This five step route to lineatin
provided gram quantities of *lineatin in an overall yield
of 10% from anhydromevalonolactone. This route, as the
previous ones, suffered from low regioselectivity in the
photoaddition step. Changes in solvent, temperature and
steric requirements of the allene did not improve the
regioselectivity. All sets of isomeric photoadducts
proved inseparable and.the synthesis was continued to
eventually provide a mixture of lineatin(l1 and - isolineatin(2). These two compounds were readily - separable by column chromatography but the high volatility
of the products led to significant loss of material,
considerably-reducing the efficiency of this route. -
Scheme 5; I
-7-
Clear ly , the photochemical r ou t e s t o l i n e a t i n have
a l l su f fe red from e i t h e r poor r e g i o s e l e c t i v i t y i n the
photoaddit ion s t e p o r , a s i n White's case , poor
r e g i o s e l e c t i v i t y i n the ox ida t ion of t he cyclobutene. We
f e l t t h a t [ 2 + 2 ] photoaddit ion s t i l l held promise f o r an
e f f i c i e n t syn thes i s of l i n e a t i n bu t a ketene equivalent
w i t h a high r e g i o s e l e c t i v i t y favor ing a B adduct was
required.
The genera l ly accepted mechanism f o r the [2+2]
photoaddit ion between a,B-unsaturated ketones and o l e f i n s
a s proposed by corey12 and de ~ a ~ o * ~ is depicted
schematical ly i n Figure 2.
Figure 2: l~*+ 0 -----c s~*+ o - ['Eo]'
BIR
Products
E= Enone O=Olefin BlR =Blradlcal Intermediate
The absorpt ion of a photon by t he enone causes
a n-lr* t r a n s i t i o n producing a s i n g l e t exci ted s t a t e
species . T h i s undergoes in tersys tem cross ing t o a t r i p l e t
exci ted s t a t e spec ies which forms an exci ted s t a t e complex
or exciplex w i t h the ground s t a t e o le f in . The exciplex
can then col lapse t o a 1,4-biradical which can close t o
form the cyclobutane. The reg iose lec t iv i ty of the
reaction is thought t o be controlled by the or ien ta t ion
of the d ipoles i n the exciplex. Carey ~ o s t u l a t e d l 2 tha t
polar izat ion of the excited s t a t e enone was reverse t o
t h a t of the ground s t a t e system. Since the preferred
or ien ta t ion of the dipoles i n the exciplex is t h a t i n
which the d ipoles a r e opposed then subst i tu ted o le f ins
polarized by e l ec t ion withdrawing groups should
p re fe ren t i a l ly give r i s e t o B subs t i tu ted regioadducts
a s depicted i n Figure 3.
Ab i n i t i o calculat ions of the charge d i s t r ibu t ion i n
excited s t a t e planar a, B -unsaturated ketonesl3.14 give
conf l ic t ing r e s u l t s b u t the experimental
results12,15,16,17 are e n t i r e l y cons is ten t w i t h t h i s
postula te .
The po la r i ty required f o r the p re fe ren t i a l formation
of the B adduct is s a t i s f i e d by a c r y l o n i t r i l e and its
a-chloro and a-acetoxy der iva t ives . (Figure 4 ) .
Figure 4: Folarity of Some Ground State Olef ins
OAc
To the best of our knowledge, there have been no
reports on the successful photoaddition of a-chloro or
a-acetoxyacrylonitr i le w i t h a , @ -unsaturated ketones or
lactones. The photoaddit ion of acryloni t r i l e w i t h
unsaturated ketones has been reported12t17f1* however.
corey12 found t h a t a c r y l o n i t r i l e added t o 2-cyclohexenone
t o give 4 products, of which the major products were the
c i s fused isomeric B -regioadducts (Scheme 6 ) . -
Scheme 6:
cantre1117 a l s o found tha t the - c i s fused
6-regioadducts were the pr incipal products i n the reaction
between 3-methyl-2-cyclohexenone and a c r y l o n i t r i l e (Scheme
7 ) . I n cont ras t t o Corey's work Cantrel l reported tha t
ac ry lon i t r i l e added much f a s t e r t o a , B -unsaturated
ketones than o le f ins subs t i tu ted w i t h e lectron r ich
heteroatom or a lky l groups.
Scheme 7:
~ u r u s a k i l 8 a l s o found tha t the - c i s fused
B-regioadduct was the major product between a f i v e
membered cyc l i c enone, 2-acetoxy-3-methyl-2-cyclopentenone
and a c r y l o n i t r i l e (Scheme 8 ) . The s t ruc tu re of the major
product was determined by x-ray crystal lographic analysis .
Scheme 8:
+ 2 other isomers
T h u s w i t h both f ive and s i x membered cyc l ic enones
a c r y l o n i t r i l e was found t o p re fe ren t i a l ly give r i s e t o
the B-regioadduct as predicted by the simple dipole
in te rac t ion model.
Our re t rosynthe t ic ana lys i s of a photochemical route
t o l i n e a t i n , which was s imi la r t o Weiler's, is depicted
i n Scheme 9 and is predicated on a c r y l o n i t r i l e adding t o
anhydromevalonolactone t o give the - c i s fused
Scheme 9: Retrosynthesis of Lineatin
The 2+2 photoaddition of olef i n s t o a , B -unsaturated
lactones has been reported19,20 t o proceed i n a manner
s imilar t o t h a t of a , B -unsaturated ketones, w i t h several
notable dif ferences . Ether was found t o be a poor solvent
fo r the reaction as hydrogen abs t rac t ion from the solvent
competed w i t h cycloaddition, The second major difference
was the report20 t h a t a c r y l o n i t r i l e d i d not undergo
photoaddition t o a var ie ty of subst i tu ted a , B -unsaturated
lactones, including anhydromevalonolactone. T h i s resu l t
was surpr is ing i n view of preliminary work done i n our
laboratory21 i n which it was found tha t ac ry lon i t r i l e
added t o anhydromevalonolactone i n an e f f i c i e n t although
stereochemically undefined manner.
The present study was undertaken w i t h several goals
i n mind: (1) t o inves t iga te the conditions necessary f o r
e f f i c i e n t [ 2 + 2 ] photocycloaddition of a,B -unsaturated
lactones - - 6-9 w i t h a c r y l o n i t r i l e as well a s i ts a-chloro
and a-acetoxy der iva t ives ; ( 2 ) t o e lucidate the s t ruc ture
and stereochemistry of the products obtained, ( 3 ) t o
apply the cycloaddit isn react ion t o t h e synthes is s f
l i nea t in .
Figure 5:
RESULTS AND DISCUSSION
I n i t i a l l y we investigated the photoaddition of
acryloni t r i l e and anhydromevalonolactone ( 6 ) - i n a var ie ty
of solvents (experiments ~ 1 - A 7 ) . The reports19 by
previous workers indicated t h e i r standard conditions
employed acetone a s the solvent. The use of acetone as a
t r i p l e t s t a t e s e n s i t i z e r and solvent f o r photoreactions
is well known20,22* I t is e f f i c i e n t f o r promoting the
cycloaddition of ethylene and acetylene t o
a , $-unsaturated lactoneslg. Our own attempts t o employ
acetone a s the solvent led only t o production of complex
mixtures of low boi l ing products and recovery of the
s t a r t i n g lactones. Acetone has a UV cutoff around
330 nm23 and a r e l a t ive ly s t ab le t r i p l e t s t a t e . I t ac t s
e f f ec t ive ly a s a f i l t e r and the cycloaddition can only
proceed i f the enone is sens i t ized by the t r i p l e t s t a t e
acetone.
We considered the poss ib i l i t y the t r i p l e t s t a t e
a r i s i n g from sens i t ized ac t iva t ion would be d i f fe ren t
. from tha t a r i s i n g from d i r e c t ac t iva t ion l5 .
The p o s s i b i l i t y of an excited s t a t e enone, a r i s ing
from t r i p l e t s t a t e sens i t i za t ion by acetone (Et=330
~~ / rno le )4O, being unable t o react w i t h ac ry lon i t r i l e
was c o n s i d e r e d u n l i k e l y i n v i ew of t h e e f f i c i e n t
s e n s i t i z e d r e a c t i o n o f e n o n e - 6 w i t h e t h y l e n e and
a c e t y l e n e . T h i s r e a c t i o n a l s o p r o c e e d e d e f f i c i e n t l y when
d i r e c t a c t i v a t i o n was used6 .
To a i d u s i n s e l e c t i o n o f p h o t o c y l o a d d i t i o n
c o n d i t i o n s w e i n v e s t i g a t e d t h e i n t e r a c t i o n between t h e
o l e f i n s of i n t e r e s t and a c e t o n e . I t was found t h a t
s o l u t i o n s of a c r y l o n i t r i l e and i t s a - c h l o r o and a -ace toxy
d e r i v a t i v e s were t h e r m a l l y s t a b l e b u t r a p i d l y formed
complex m i x t u r e s o n i r r a d i a t i o n i n t h i s s o l v e n t .
S o l u t i o n s o f o l e • ’ i n and l a c t o n e 5 i n a c e t o n e produced
similar p r o d u c t m i x t u r e s when i r r a d i a t e d . Only t r a c e
amounts of t h e 1:l a d d u c t s were d e t e c t e d by GLC.
We were u n a b l e t o c o n v e n i e n t l y m o n i t o r t h e
c o n c e n t r a t i o n o f a c r y l o n i t r i l e and a - c h l o r o a c r y l o n i t r i l e
by GLC b u t t h e a - a c e t o x y a c r y l o n i t r i l e peak was
s u f f i c i e n t l y s e p a r a t e d f r o m t h e s o l v e n t peak t o permit
r e l i a b l e q u a n t i f i c a t i o n . I t was f o u n d t h a t t h e
c o n c e n t r a t i o n of t h i s o l e f i n was c o n s t a n t i n t h e d a r k and
d e c r e a s e d r a p i d l y upon i r r a d i a t i o n . We conc luded from
t h e s e e x p e r i m e n t s t h a t a c e t o n e r e a c t e d w i t h t h e o l e f i n s
- f a s t e r t h a n t h e o l e f i n s were r e a c t i n g w i t h 6. - Next we s t u d i e d t h e i n t e r a c t i o n of o t h e r t r i p l e t
s e n s i t i z e r s w i t h t h e o l e f i n s i n a c e t o n i t r i l e s o l u t i o n s
(UV c u t o f f 1 9 0 nm)23. A Corex f i l t e r was used i n t h e s e
experiments t o permit ac t iva t ion of only the sens i t izers ,
acetophenone ( E t = 3 1 0 ~d /mole ) lo and hexamethylbenzene
(Et=330 ~ ~ / m o l e ) ~ O . We found t h a t a l l combinations of
o l e f i n and sens i t i ze r led t o complex mixtures upon
i r r a d i a t i o n . However, a c e t o n i t r i l e solut ions of the
s e n s i t i z e r and a hydrocarbon i n t e r n a l standard were
photostable, indicating t h a t s e n s i t i z e r was reacting w i t h
o l e f i n and not w i t h solvent. It was a l s o found tha t i n
the presence of the s e n s i t i z e r s tes ted the photoaddition
of - 6 w i t h ac ry lon i t r i l e and its a-chloro and a-acetoxy
der iva t ives d i d not proceed.
We did not investigate the nature of the photo-
react ion between the s e n s i t i z e r and the o le f ins as they
appeared t o be of l i t t l e syn the t i c value. Other workers
have reported25,26,27 tha t acetone adds t o carbonyls and
other polarized n-systems t o form oxetanes. These
primary photoproducts can undergo complex secondary
thermal or photochemical reactions.
Use of other UV t ransparent solvents , such as
methanol, isopropanol and e ther , led t o the formation of
complex mixtures. The desired 1:l photoadducts were only
- detected a s minor components. Generally i n these
solvents consumption of the lactone - 6 ceased a f t e r
several hours of i r r ad ia t ion leaving 40-80% unreacted.
Use of these solvents led t o production of much polymeric
mater ia l t h a t i n t e r f e r e d w i t h the t ransmission of l i g h t
and was l i k e l y responsib le f o r t he s luggishness of the
react ion. In add i t i on t o the p r o l i f i c production of t a r s
and polymers, t he se so lven t s have a l s o been r e ~ o r t e d l g t o
r eac t with photo-act ivated enones by abs t r ac t i on of a
hydrogen atom.
The photochemical r eac t ions of lac tones 7-9 w i t h - - a c r y l o n i t r i l e and i ts a-chloro and a-acetoxy de r iva t i ve s
were ca r r i ed ou t i n acetone, e t h e r and methanol w i t h
e s s e n t i a l l y t he same r e s u l t s a s above.
In summary, w e have found t h a t a c r y l o n i t r i l e and its
a-chloro and a-acetoxy de r iva t i ve s r e a c t w i t h acetone
f a s t e r than w i t h any of the l ac tones s tudied . These
o l e f i n s a l s o reacted w i t h o the r t r i p l e t s t a t e s e n s i t i z e r s
under condi t ions i n which only t h e s e n s i t i z e r s were
absorbing.
I r r a d i a t i o n of - 6 w i t h a c r y l o n i t r i l e using
a c e t o n i t r i l e a s t he solvent led t o t he formation of
cycloaddi t ion products - 1 0 and - 11 which were separable by
f l a s h chromatography.
Scheme 10:
These photoadducts (Table 1) exhibited the expected
molecular ion peaks by MS. GC/MS samples were usually
analysed in CI mode as the molecular ion peak was weak
and sometimes absent when EI was used. The possibility
that the adducts were the isomeric oxetanes or exocyclic
olefins was eliminated upon examination of their 13c nmr
spectra. The expected signals due to carbonyl carbons
were evident and no signals due to olefinic carbons were
observed in the isolated mixtures.
For this [2+2] photocycloaddition there are eight
possible isomeric bicyclic[4.2.0] structures differing at
the ring-junction stereochemistry (cis and trans fused), nitrile regiochemistry (13 - and - Y regioisomers) and the nitrile stereochemistry (endo and = I .
We first turned our attention to the ring-junction
stereochemistry of - 10 and - 11.
There were previous reports12r28,29 of trans-f used
bicyclo[4.2.0]octanones arising from photochemical
cycloaddition of electron rich olefins to
2-cyclohexenones. The trans-fused [4.2.01 compounds
were characterized by their rapid and complete
isomerization to the less strained - cis fused compounds
with acid, base or heat12r29. MM2 (1985 Force ~ i e l d ) ~ ~
calculations of the relative strain energies showed that
the AE (JE=Etrans-Ecis) was ca. 40 ~ ~ m - l for the f4.2.01 - 7
series (Table 2) and - ca. 105 K J ~ ' ~ for the [3.2.01
Table 1: Summary of Reactions o f d-Lactones
- Yield % - 77 64 54 62 5 6 64 65 60 - 2 9 - n -
endo-CN Product % R,
H H CI C I
OAc OAc H H
C I CI
OAc OAc
Ixperiment A1 A 2 81 82 C1 C2 D 1 D2 E 1 E2 F1 F2
Table 2: Summary o f MM2 Calculations for &-Lactones
cis trans
a . Coupling Constant J Calculated from Dihedral Angle Oby ICarplus3' Equation i n the form;
R .
H
H
CH,
CH,
R,
H
CN
H
CN
Table 3: J= A $. BCOSO + C C O S ~ @
R,
CN
H
CN
H
Isomer Pair
17:18
10:11 17~31
~~ui l ibr iurn '
cis Isomer
17
18 10
AE KJ
2.2 4.1
40.0
Population
71:29 84:16
100:O
K at 2S•‹C
2.43
5.20
10'
where A=7, B=-1, C=5.
Stra in
%r?Y 143.8 146.0 144.2
11 1 148.3
@ti,-H
115 2.9
135
1.5
a J ~ I - ~
4.2 11.0 7.7 11.0
trans Isomer
31
32
33
Strain Energy KJm-
169.9
173.0 184.2
34 192.1
ser ies . T h e s e s t r a i n e n e r g i e s a re i n k e e p i n g w i t h
reports t h a t i s o m e r i z a t i o n o f t h e t r a n s f u s e d t o cis - f u s e d b i c y c l o [ 4 . 2 . 0 l o c t a n e s is e s s e n t i a l l y comp le t e30 .
E x p e r i m e n t a l l y it was f o u n d t h a t t r e a t m e n t o f t h e
p h o t o a d d u c t s - 1 0 a n d - 11 w i t h a l u m i n a d i d n o t a f f e c t a n y
c h a n g e s i n e i t h e r t h e p u r e compounds o r m i x t u r e s o f
p h o t o a d d u c t s . T h e s e are c o n d i t i o n s w h i c h s h o u l d h a v e
r e s u l t e d i n t r a n s -cis - i s o m e r i z a t i o n l 2 . I t was
t h e r e f o r e c o n c l u d e d t h a t p h o t o a d d u c t s - 1 0 a n d - 11 p o s s e s s e d
t h e - c i s r i n g f u s i o n .
We n e x t t u r n e d a t t e n t i o n t o t h e r e g i o c h e m i s t r y o f
t h e n i t r i l e i n - 1 0 a n d - 11. The B - r e g i o c h e m i s t r y o f t h e
n i t r i l e was e v i d e n t from t h e c o u p l i n g p a t t e r n e x h i b i t e d
by t h e p r o t o n a t C 1 . Thus w e o b s e r v e d d o u b l e t s i n b o t h
1 0 a n d 11 as would be e x p e c t e d of B - r e g i o i s o m e r s . - - H a v i n g a s s i g n e d t h e s t e r e o c h e m i s t r y of t h e r i n g
f u s i o n a n d d e d u c e d t h e r e g i o c h e m i s t r y of t h e n i t r i l e
s u b s t i t u e n t we n e x t examined t h e s t e r e o c h e m i s t r y of t h e
n i t r i l e c o n f i g u r a t i o n i n - 1 0 a n d - 11. We u s e d MM2
c a l c u l a t i o n s t o estimate t h e d i h e d r a l a n g l e s a n d r e l a t i v e
s t r a i n e n e r g i e s of - e n d o a n d e x o n i t r i l e i s o m e r s 1 1 : l O . - -- T h e s e c a l c u l a t i o n s are summar i zed i n Table 2. The
e x p e r i m e n t a l l y o b s e r v e d c o u p l i n g c o n s t a n t s be tween H 1 a n d
H g o f 7 a n d 11 Hz were i n good a g r e e m e n t w i t h t h e
p r e d i c t e d 3 8 c o u p l i n g c o n s t a n t s o f 7 .7 a n d 1 1 . 0 Hz f o r
-20-
photoadducts - 10 and - 11 respectively. O n t h i s basis we
assigned - exo-CN stereochemistry t o the major product - 10
and - endo-CN stereochemistry t o 2. Both the experimental
and MM2-derived coupling constants were i n good agreement
w i t h the l i t e r a t u r e ~ a l u e s 2 9 , 3 ~ of Jcis = 10.4 - 9.0 Hz - and Jtrans = 6.6 - 3.2 Hz fo r s imi la r fused cyclobutane
systems.
MM2 ca lcula t ions were a lso used i n another fashion.
Mixtures of epimers tha t are equi l ibrated through common
intermediates give mixtures, the compositions of which
re f l ec t the r e l a t i v e product en.erg$es30132. If the
r e l a t ive energies of the products a re known then
equilibrium .populations can be calculated30. Accordingly
we calculated ( M M 2 ) the re la t ive energies of a l l possible
bicycloI4.2.0]octanone photoadducts. The pert inent
calculations a re summarized i n Table 3.
The pure adducts - 1 0 and - 11 were t reated w i t h sodium
ethoxide i n ethanol29 and found t o rzipidly equi l ibra te t o
80:20 mixtures of -- 10 : l l a t room temperatures. T h i s was
i n good agreement w i t h the predicted r a t i o of 84:16
exo:endo supporting our i n i t i a l assignment of the C8 - stereochemistry.
Table 7: Spectral Parameters E 8 - lm%d
11000
Jmox Compound nm
212 9900
205 12000
208 13500
I I 199 12000
I
d I 1: )
5 9600
10 1
13
275 1800
6 210
A question arose a t t h i s point a s t o whether the
mixtures generated above were i n f a c t equilibrium
mixtures or whether base abs t rac t ion of the C-8 proton
was merely slow. The observation of ident ical product
mixtures being formed w i t h i n 30 minutes when e i t h e r 1 0 or - 11 were used as the s t a r t i n g mater ia l confirmed tha t - abstract ion was rapid and complete. We repeated these
experiments on - 1 0 and 2 using E t O D a s the solvent and
examining the products by GC/MS. We had expected t o f ind
only the complete exchange of one proton b u t found tha t
i n addition t o t h i s - ca. 30% had exchanged a second proton
f o r deuterium. The only other act ivated methylene group
was the bridgehead posi t ion C 1 , a t o the carbonyl. We
were not able t o Find a c i d i t i e s of s imi la r systems i n the
l i t e r a t u r e but i t is kn0wn~313~ t h a t the a c i d i t i e s of
methylenes a t o n i t r i l e s a re comparable t o those a t o
carbonyls i n a l i p h a t i c compounds. I t has a lso been
reported t h a t act ivated methylenes a t bridgehead
posit ions have lower a c i d i t i e s than analogous
non-bridgehead methylenes because of hindrance t o
resonance s t a b i l i z a t i o n of the carbanion.
11 abstract ion of the proton a t C 1 was occurring upon
treatment w i t h sodium ethoxide, a l b e i t a t a slower ra te
than the abs t rac t ion a t C g . The lack of formation of new
c~mpounds on t rea tment w i t h sodium ethoxide a l so
supported our o r i g i n a l assignment of c i s fused r i ng - geometry f o r the adducts 10, and 11.
I r r a d i a t i o n of a - ch lo roac ry lon i t r i l e w i t h 6 i n - a c e t o n i t r i l e gave two adducts f o r which s t r u c t u r e s 1 2 and - 1 3 a r e suggested. I r r a d i a t i o n of a - ace toxyac ry lon i t r i l e - w i t h 6 i n a c e t o n i t r i l e gave two adducts f o r which - s t r u c t u r e 15 and 16 a r e suggested.
Scheme 12:
The a-chloro and a-acetoxy a c r y l o n i t r i l e adducts
(12,13f15f16) ---- were inseparable and IH and 13c NMR
analyses were done on mixtures. In a l l cases the s i g n a l s
due t o t h e proton a t C 1 appeared e i t h e r a s s i n g l e t s o r
mu l t i p l e t s w i t h small coupling constants i nd i ca t i ve of
lone range i n t e r a c t i o n s and incons i s ten t w i t h v i s c ina l C8
hydrogens. These s p e c t r a l c h a r a c t e r i s t i c s indica ted
B-regiochemistry f o r --- 12,13,15 and 16.
I t was n o t p o s s i b l e t o a s s i g n t h e geometry of t h e
r i n g f u s i o n by b a s e i s o m e r i z a t i o n e x p e r i m e n t s s i n c e m i l d
b a s e caused e x t e n s i v e d e c o m p o s i t i o n of these a d d u c t s .
Given t h e predominance o f - cis f u s e d b i c y c l o [ 4 . 2 . 0 l o c t y l
d e r i v a t i v e s from p h o t o a d d i t i o n s o f c y c l i c
a , B - u n s a t u r a t e d c a r b o n y l s and e l e c t r o n d e f i c i e n t
o l e f i n s l 2 r 4 l is it s u g g e s t e d t h a t a d d u c t s , --- 12,13,15 and
1 6 are c i s f u s e d . - - We were a b l e t o a s s i g n t h e s t e r e o c h e m i s t r y i n
12 ,13,15 and 1 6 by ana logy w i t h p r e v i o u s work i n t h e --- - s t e r o i d f i e l d 3 5 i n which t h e e f f e c t s o f s u b s t i t u e n t s i n
1 , 3 - d i a x i a l c o n f i g u r a t i o n s on t h e IH NMR chemical s h i f t s
of methyl r e s o n a n c e s were measured. I t was found t h a t
d e s h i e l d i n g of t h e methyl g r o u p and hence t h e magni tude
of t h e d o w n f i e l d s h i f t of t h e methy l r e s o n a n c e was i n t h e
o r d e r of Cl>CN>OAc>H.
We a l s o compared t h e 1 3 ~ c h e m i c a l s h i f t s of t h e
n i t r i l e i n t h e d i a s t e r e o m e r s -- 12:13 and 15:16.
Examinat ion of models s u g g e s t e d t h a t n i t r i l e s i n t h e endo
c o n f i g u r a t i o n were i n t h e s h i e l d i n g z o n e s of
t h e l a c t o n e c a r b o n y l s . Hence t h e 1 3 ~ ~ r e s o n a n c e s of
a d d u c t s p o s s e s s i n g t h e endo n i t r i l e c o n f i g u r a t i o n would
be e x p e c t e d a t h i g h e r f i e l d s r e l a t i v e t o t h o s e w i t h
n i t r i l e s i n t h e - e x o c o n f i g u r a t i o n s . S i m i l a r e f f e c t s have
been p r e v i o u s l y used t o a s s i g n s t e r e o ~ h e m i s t r ~ ~ ~ . The
experimentally observed chemical s h i f t s and subsequent
s t ruc tu re assignment a re l i s t e d i n Table 4 . The
stereochemical ass ignments conducted on t h i s basis were
e n t i r e l y consis tent w i t h assignments- made by
considerat ion of v i c ina l coupling constants and base
equi l ib ra t ion experiments.
. I r rad ia t ion of a c r y l o n i t r i l e , a-chloroacrylonit r i l e
and a-acetoxyacrylonitr i le w i t h - 7 each gave s e t s of two
adducts (lJ:_18; =:20; 2:z respectively) which were
inseparable except by c a p i l l a r y gas chromatography.
GC/MS spec t ra l ana lys i s were consis tent w i t h formation of
[ 2 + 2 ] cycloadducts i n each reaction. Both
6-regiochemistry and - c i s r ing fusion were assumed f o r
these adducts . The n i t r i l e stereochemistry assigned was
deduced fqom the arguments given above pertaining t o
Table 4 .
Scheme 13:
Table 4 : 'H and NMR Chemical Shif tg
Compound
Structure
Ra - CN
H
CI
CN
CN
OAc
CN
H
CN
CI
0 Ac
CN -
It RI - ti
CN
CN
CI
DAc
CN
H CN
CI
CN
CN
OAc -
Figure 6: Bicyclic Numbering System
-27- --
The mix tu res of the 2 photoadducts - 17 and -I 18 from
t h e pho toadd i t ions of 2-pentenolide (2) t o a c r y l o n i t r i l e
were a l s o s u b j e c t e d t o base e q u i l i b r a t i o n with NaOEt.
This mixture was found t o r a p i d l y i somer ize t o a 75:25
mixture of -- 17:18 a t 25%. This r a t i o was a l s o i n good
agreemdnt w i t h t h e p red ic ted (Table 3 ) r a t i o of 71:29
exo:endo whaich suggested t h a t 17 possessed the exo-CN -- - s t e r e o c h e m i s t r g whi le - 18 was - endo-CN.
Some o b s e r v a t i o n s on t h e s t e r e o s e l e c t i v i t y of t h e
photocycloaddi t ion reac t ions of t h e 6- lactones - 6 and - 7
can be made. The r a t i o s of the - exo-CN t o - endo-CN,
6-regioisomers, 10:11, 13:12, 15:16, 17:18, 19:20 and -7 -- -7 -- --
22:21, produced were found t o be i n s e n s i t i v e t o t h e -- -
temperature (Tab le 1). T h i s r a t i o was a l s o r e l a t i v e l y
i n s e n s i t i v e t o s u b s t i t u t i o n a t C-6 (CH3 vs HI. The
adducts were found t o be pho tos tab le and t h e r a t i o s
observed a r e n o t due t o photoisomerizat ion.
We next turned our a t t e n t i o n ts photocycloaddi t ion
of t h e Y -1actone - 8 and found s e v e r a l notable d i f f e r e n c e s .
We found t h a t i r r a d i a t i o n of w i t h a c r y l o n i t r i l e i n
a c e t o n i t r i l e produced four isomeric 1 : l* adducts, - 23, - 2 4 ,
25 and 26 (Table 5 ) . - - Scheme 14:
- Table 5 : Summary of Reactions of I'-Lactones
endo-CN Undetermined TProdust % Products
38 24,26 22,17 42 24,26 19,15
15 27,29 27,32 20 27.29 19,25
exo-CN yield% Product %
29 23 23 40 - 23 23
- - - 78 28 26 81 . 28 35 - - - -
Experimenl GI G2 HI H2 .
- I1 I2 J 1 52 K1 K2 L1 L2
H H C I CI
OAc OAc H H C1 C1 3Ac 3Ac -
Table 6: Summary of MM2 Calculations f o r )?-Lactones
trans
Strain - Strain trans Energy
Isomer K J ~ -
40 228.0
41 217.5 42 227.9
43 225.0
44 163.0
45 268.3
46 272.4
47 269.8
a. Coupling Constant J Calculated from ~ i h e d t a l 'Angle (-1 by ~ a r ~ l u s ~ ' Equation i n the form; J= A + ~ ~ o s f l + CcosZH
where A=7, B=-1 , CIS. . .
T h i s m i x t u r e was p a r t i a l l y s e p a r a t e d i n t o two f r a c t i o n s
e a c h c o n t a i n i n g a pa i r of p r o d u c t s . W e de te rmined t h a t
t h e s e p r o d u c t s were n o t t h e i s o m e r i c o x e t a n e s nor
e x o c y c l i c o l e f i n s by GC/MS and 13c NMR a n a l y s i s . We a l s o
d e t e r m i n e d t h a t t h e i s o l a t e d p h o t o a d d u c t s -- 23-26 and were
n o t a f f e c t e d by t r e a t m e n t w i t h a lumina . From t h e s e
e x p e r i m e n t s we deduced t h a t p h o t o a d d u c t s 23-2 and
p o s s e s s e d t h e more s t a b l e cis r i n g f u s i o n . The
p o s s i b i l i t y of i s o l a t i n g t r a n s f u s e d [ 2 + 2 ]
p h o t o c y c l o a d d u c t s from t h e i r r a d i a t i o n of Y - 1 a c t o n e s
w i t h a c r y l o n i t r i l e was c o n s i d e r e d u n l i k e l y i n view of t h e
l a c k of any l i t e r a t u r e p r e c e d e n t .
We c o n c l u d e d p r o d u c t s 23-26 were a m i x t u r e of t h e
exo-CN and endo-CN, B and Y - r e g i o i s s m e r s . T h i s was not - e n t i r e l y u n e x p e c t e d as p r e v i o u s workers had r e p o r t e d t h a t
5-membered c y c l i c e n o n e s and l a c t o n e s were more p rone t o
g i v e m i x t u r e s of r e g i o i s o m e r s t h a n t h e i r 6-membered r i n g
ana logs12 ,20 . S i n g l e c r y s t a l s of 23 and 25 were i s o l a t e d
from t h e m i x t u r e s and unambiguously i d e n t i f i e d by X-ray
c r y s t a l a n a l y s i s a s t h e - cis f u s e d , 6 , - exo-CN isomer and
c i s f u s e d , B , endo-CN i somer r e s p e c t i v e l y 3 g . We assumed - t h a t a d d u c t s - 24 and - 26 were t h e Y- reg io i somers ( d e p i c t e d
a s - 35 and - 36 i n T a b l e 6 ) b u t c o u l d n o t show t h i s by
e i t h e r 1~ o r 1 3 ~ NMR a n a l y s i s because of o v e r l a p p i n g
s i g n a l s .
Treatment of t h e p h o t o l y s i s mixture (23-26) w i t h -- sodium e thox ide a s before r e s u l t e d i n conversion t o
h igh ly p o l a r compounds, presumably by t r a n s e s t e r i f i c a t i o n
of t h e l a c t o n e . The r a t i o of photoadducts 23-26 was -- found t o be s l i g h t l y s e n s i t i v e t o t h e temperature of t h e
pho to reac t ion and the i s o l a t e d adduc t s were found t o be
pho tos tab le (Table 5 ) .
I r r a d i a t i o n of a-chloro o r a -ace toxyacry lon i t r i l e
w i t h - 8 i n a c e t o n i t r i l e gave no photoadducts. Presence of
e i t h e r of t h e s e two o l e f i n s i n t h e r e a c t i o n mixture a l s o
prevented r e a c t i o n between t h e - 8 and a c r y l o n i t r i l e . T h i s
is probably due t o over lap of t h e absorp t ion bands of t h e
Y-lactones w i t h t h e heteroatom-subst i tuted
a c r y l o n i t r i l e s (Table 7 ) . S ince t h e o le f i n s were p resen t
i n t en fo ld excess these would block absorbance by t h e
l ac tone . In an at tempt t o circumvent t h i s problem we
slowly added t h e a c r y l o n i t r i l e d e r i v a t i v e s t o the
s o l u t i o n of l a c t o n e - 8 during t h e i r r a d i a t i o n . We
reasoned t h a t i f t he concen t ra t ion of t h e o l e f i n was kept
low then it would not i n t e r f e r e w i t h t h e t ransmission of
l i g h t i n t h e s o l u t i o n . T h i s technique was not
s a t i s f a c t o r y and only produced t r a c e amounts of t h e
d e s i r e d 1:l photoadducts which were t e n t a t i v e l y
i d e n t i f i e d by t h e i r MS.
Because we were t r y i n g t o extend the s y n t h e t i c
u t i ' l i t y of t h e s e r eac t ions we considered the production
of mixtures of regioisomers t o be unacceptable and
attempted t o a l t e r t h e r e g i o s e l e c t i v i t y of t h e reac t ion .
We reasoned t h a t the i nc lu s ion of methyl groups a t C3 and
Cq i n a Y- lac tone would impede t he formation of
Y-regioisomers. Accordingly we undertook the syn thes i s
of the methyl s u b s t i t u t e d Y -1actone 9 by the route shown
i n Scheme 16 and i nves t i ga t ed its photochemistry.
I r r a d i a t i o n of - 9 w i t h a c r y l o n i t r i l e i n a c e t o n i t r i l e
produced four isomeric 1:l photoadducts, - 27 , - 28 , - 29 and
30. These compounds were unaffected by treatment w i t h 7
alumina i nd i ca t i ng t h a t they a l l possessed a r ing
fus ion. Repeated chromatography on s i l i c a ge l eventual ly
separa ted the minor component - 30 from t h e mixture.
Scheme 15:
The B -regiochemistry of the n i t r i l e i n a was
evident from t h e s p l i t t i n g p a t t e r n of the s i g n a l due t o
H i i n the 18 nmr spectrum of t h i s compound. We
t e n t a t i v e l y assigned t he - endo stereochemistry t o the
n i t r i l e of - 30 a f t e r comparison of the experimental ly
observed coupling constant of H i - H 7 (8 .5 Hz) t o e a r l i e r
$=heme 16: synthes i s of 3,4,4-trimethyl-2-butenolide
r e p o r t s of c o u p l i n g c o n s t a n t s i n s i m i l a r - c i s - f u s e d
b i c y c l o t 3 . 2 . 0 1 h e ~ t a n o n e s ~ ~ . Kosugi had r e p o r t e d t h a t f o r
s u c h f u s e d s y s t e m s t h e - cis H i - H q c o u p l i n g was 9.0 H z and
t h e t r a n s H i - H 7 c o u p l i n g was 5 .1 H z . T h i s is i n
modera te ly good agreement w i t h o u r M M 2 d e r i v e d c o u p l i n g
c o n s t a n t s 3 8 of Jcis = 10.9 H z and Jtrans = 3.2 H Z f o r - 30
and - 37 r e s p e c t i v e l y .
The o t h e r t h r e e components o f t h e m i x t u r e were
i n s e p a r a b l e by chromatography and s p e c t r a l a n a l y s e s were
performed on t h e m i x t u r e . Due t o t h e complex i ty of t h e
1~ nmr spectra of t h i s m i x t u r e w e were u n a b l e t o a s s i g n
t h e r e g i o o r s t e r e o c h e m i s t r y of -- 27-29. W e assumed t h e
m i x t u r e c o n s i s t e d of t h e - exo-CN 0 - r e g i o a d d u c t and t h e
e x o and endo-CN Y - r e g i o a d d u c t s i l l u s t r a t e d as 37, 38, and - - - 39 r e s p e c t i v e l y i n Tab le 6. -
Thus w e were u n a b l e t o make any d e f i n i t i v e
s t a t e m e n t s c o n c e r n i n g t h e e f f e c t s o f me thy l v s hydrogren
s u b s t i t u t i o n a t C 3 and C4 i n t h e p a r e n t l a c t o n e s on t h e
r e g i o s e l e c t i v i t y of t h e p h o t o a d d i t i o n . I t was a p p a r e n t ,
however, t h a t t h e r e was no s i g n i f i c a n t improvement i n t h e
r e g i o s e l e c t i v i t y of p h o t o a d d i t i o n upon methyl
s u b s t i t u t i o n .
The e f f ec t of t e m p e r a t u r e on t h e p r o d u c t
d i s t r i b u t i o n was a l s o examined f o r t h e r e a c t i o n of - 9 w i t h
a c r y l o n i t r i l e ( T a b l e 5 ) . The r a t i o of -- 27-30 was found t o
be s l i g h t l y a f f e c t e d by t h e t e m p e r a t u r e a t which t h e
i r r a d i a t i o n was c o n d u c t e d . D e c r e a s i n g t h e t e m p e r a t u r e
from a m b i e n t t o -200C i n c r e a s e d t h e r e l a t i v e amount of 30 - by 5%. The r e l a t i v e amounts o f 2-2 a l s o changed by
709%. While t h i s change is small it was t h e la rges t
change i n p r o d u c t d i s t r i b u t i o n d u e t o t e m p e r a t u r e
obse rved i n t h i s work.
I t s h o u l d b e n o t e d t h a t a lesser change i n t h e
p r o d u c t d i s t r i b u t i o n of t h e 1:l c y c l o a d d u c t s d u e t o
t e m p e r a t u r e was a l s o o b s e r v e d i n t h e p h o t o a d d i t i o n of
a c r y l o n i t r i l e t o t h e hydrogen s u b s t i t u t e d Y -1ac tone 8. - I n t h e s e p h o t o a d d i t i o n s ( e x p e r i m e n t s G 1 and G 2 , Table 5 )
it was f o u n d t h a t t h e r e l a t i v e amount o f t h e e n d o - n i t r i l e 6 - r e g i o i s o m e r , - 25, i n c r e a s e d by 4% and t h e e x o - n i t r i l e 8 - r e g i o i s o m e r , 23, d i d n o t change when t h e
t e m p e r a t u r e was lowered f rom a m b i e n t t o - 2 0 0 ~ . The
r e l a t i v e amounts o f t h e two Y - r e g i o a d d u c t s - 24 and - 26
( i l l u s t r a t e d as 35 and 36 i n T a b l e 5 ) d e c r e a s e d by
2-3% when t h e t e m p e r a t u r e was lowered f rom ambien t t o
-20•‹C. T h i s e f fec t was c o n s i s t e n t w i t h t h e simple d i p o l e
i n t e r a c t i o n model p roposed by c o r e y 1 2 , which would f a v o u r
. \ t h e f o r m a t i o n o f t h e 8 - r e g i o a d d u c t s a t l o w e r
t e m p e r a t u r e s . T h i s r a t i o n a l i z a t i o n is p r e d i c a t e d on t h e
c h a r g e d i s t r i b u t i o n i n t h e e x c i t e d s t a t e Y - l a c t o n e b e i n g
r e v e r s e d t o t h a t o f t h e ground s t a t e l a c t o n e .
We u t i l i z e d t h e p r e f e r e n t i a l f o r m a t i o n of t h e
B-regiosomers a t l o w e r t e m p e r a t u r e s t o a s s i g n t h e
r e g i o c h e m i s t r y of a d d u c t s 27-z ( e x p e r i m e n t s J1 and 3 2 ,
T a b l e 5 ) . T h i s l i n e of r e a s o n i n g s u g g e s t e d t h a t 28 was
t h e - e x o n i t r i l e B - r e g i o a d d u c t (37, T a b l e 6 ) as t h e
r e l a t i v e amount i n c r e a s e d by 9% o n r e d u c t i o n of t h e
t e m p e r a t u r e from a m b i e n t t o -20•‹c. The r e l a t i v e amounts
of - 27 and - 29 d e c r e a s e d by 7% e a c h a t lower t e m p e r a t u r e s
s u g g e s t i n g t h a t t h e s e two a d d u c t s were t h e
Y - r e g i o i s o m e r s ( i l l u s t r a t e d as - 38 and 2 i n T a b l e 6 ) .
I n summary it was f o u n d t h a t a c e t o n i t r i l e s o l u t i o n s
of t h e 6 - 1 a c t o n e s - 6 and - 7 underwent [2+21
p h o t o c y c l o a d d i t i o n w i t h a c r y l o n i t r i l e and i ts a - c h l o r o
and a - a c e t o x y d e r i v a t i v e s i n a h i g h l y r e g i o s e l e c t i v e
manner t o g i v e m i x t u r e s of - e n d o - n i t r i l e and - e x o - n i t r i l e
B- reg ioadduc t s . The y i e l d s of t h e s e r e a c t i o n s ranged
f rom good t o m o d e r a t e and none o f t h e Y - r e g i o i s o m e r s were
i s o l a t e d . The B - r e g i o a d d u c t s were o f t e n i s o l a t e d i n a
c r y s t a l l i n e fo rm which a l l o w e d r e c r y s t a l l i z a t i o n t o a
h i g h d e g r e e o f p u r i t y .
The s t e r e o c h e m i s t r y a t C8 i n t h e p h o t o a d d u c t s was
found t o be i n s e n s i t i v e t o e i t h e r t h e s u b s t i t u t i o n a t
C 3 (CH3 v s H) i n t h e p a r e n t l a c t o n e s o r t h e t e m p e r a t u r e
a t which t h e i r r a d i a t i o n was c o n d u c t e d . D e s p i t e t h e l a c k
o f c o n t r o l of t h e C 8 s t e r e o c h e m i s t r y t h e h i g h r e g i o -
s e l e c t i v i t y of t h e s e r e a c t i o n s s h o u l d be of some
s y n t h e t i c u t i l i t y .
The Y- lac tones - 8 and - 9 d i d n o t undergo photo-
a d d i t i o n w i t h a - ch lo ro o r a - a c e t o x y a c ~ y l o n i t r i l e ,
presumably due t o o v e r l a p of t h e a b s o r p t i o n bands of t h e
o l e f i n s and t h e l a c t o n e s .
The Y- lac tones - 8 and - 9 d i d undergo photoaddi t ion
w i t h a c r y l o n i t r i l e i n a c e t o n i t r i l e s o l u t i o n s i n an
e f f i c i e n t manner, bu t w i t h poor r e g i o s e l e c t i v i t y . The
hydrogen s u b s t i t u t e d Y -1actone - 8 produced a 3:2 mixture
of B : Y - reg io i somers a t ambient t empera tu re and a
m a r g i n a l l y h i g h e r p r o p o r t i o n of 6-regioadducts a t -20•‹C.
The methyl s u b s t i t u t e d Y -1actone - 9 produced a 2: 3 mixture
of B : Y - reg ioadduc ts a t ambient t empera ture and a
s l i g h t l y h i g h e r p r o p o r t i o n of t h e d e s i r e d
B-regioadduct a t -20%.
The poor r e g i o s e l e c t i v i t y e x h i b i t e d by the
Y- lac tones 8 and 9 and t h e d i f f i c u l t y of s e p a r a t i n g t h e
B and Y r eg ioadduc t s produced, c u r t a i l t h e s y n t h e t i c
u t i l i t y of t h e s e r e a c t i o n s c o n s i d e r a b l y .
EXPERIMENTAL
Infrared spectra were recorded on a Perkin-Elmer 5958
spectrophotometer a s l iqu id f i l m s between NaCl p la tes or
as KBr p e l l e t s . Ul t rav io le t spectra were recorded on a
Unicam SP 800 spectrophotometer. Nuclear magnetic
resonance spectra were recorded on a Bruker 400 WM NMR
spectrometer using C D C 1 3 a s a solvent and the residual
CHC13 as an in t e rna l standard. The chemical s h i f t s a re
reported i n 6 u n i t s , the s p l i t t i n g pa t te rns as
s ( s i n g l e t ) , d (double t ) , t r ( t r i p l e t ) , q ( q u a r t e t ) ,
dd (double doublet) , m (mul t ip le t ) . coupling constants
(J) are reported i n Hz (cycles /sec) . I n l 3 ~ analysis the
m u l t i p l i c i t i e s were determined by 9 modulated spin echo
experiments (mulipl ic i ty s o r t i n g ) . Low resolution mass
spectra were obtained on a Hewlett-Packard 59858 coupled
gas chromatograph/mass spectrometer u s i n g an e lectron
impact ionization voltage of 70 eV. Melting points were
' determined on e i t h e r a Fisher-Johns hot p la te or a
Gallenkamp melting point apparatus and are uncorrected.
Boiling points a re not corrected. GLC analyses were
obtained on a Hewlett-Packard 5880A gas chromatograph
equipped w i t h a flame ionizat ion detector and u s i n g a
0.2 mm I D x 15 m O V - 1 0 1 o r a DB-1 cap i l la ry column.
Elemental analyses were performed by M . K . Yang a t the
Department of Biological Sciences, S.F.U.
A l l photolyses, except f o r those experiments
concerned w i t h solvent e f f e c t s were run i n HPLC grade
a c e t o n i t r i l e obtained from Caledon Laboratories.
( d l ) Mevalonalactone was obtained from Sigma,
a c r y l o n i t r i l e , a -chloroacryloni t r i le and
5-hydroxy-2-pentenoiclactone (1) from Aldrich Chemical
Co, , and a -acetoxyacrylonit r i l e from Alpha Chemical Co.
General Procedure of Photoaddition
The lactones and o le f ins were d i s t i l l e d before use.
HPLC grade a c e t o n i t r i l e was used without pur i f icat ion. I n
a typical experiment a so lu t ion of the lactone (ca. - 40 mmol), o l e f i n (5-10 eq) and an in t e rna l standard ( a
sa turated hydrocarbon such a s decane) i n z. 200 mL
a c e t o n i t r i l e was placed i n a Pyrex, quartz or Vycor
photolysis apparatus equipped w i t h a reflux condenser
( F i g . 7 ) . The so lu t ion was deoxygenated by purging w i t h
N2 f o r 30 minutes before ac t iva t ing the lamp. For low
temperature experiments the apparatus was cooled i n an
acetone/C02 bath i n a Dewar f lask . A 450 W Hanovia 6790A
medium pressure mercury lamp enclosed by a quartz water
cooled lamp jacket was used fo r the i r rad ia t ions , 1
The reactions were followed by periodically removing
al iquots during the i r r ad ia t ion and subjecting them t o GLC
analysis . I r r ad ia t ion was stopped when there was no
Figure 7 : Photolysis Apparatus
Condensor Adapter
Lamp Well
Solution Compartment
Immersion Well
Torus Reactor
f u r t h e r change of t h e c o n c e n t r a t i o n s o f e i t h e r t h e
s t a r t i n g l a c t o n e o r p r o d u c t s r e l a t i v e t o t h e i n t e r n a l
s t a n d a r d . The i n i t i a l (T=O) s a m p l e was k e p t i n t h e d a r k
as a c o n t r o l and a n a l y z e d a g a i n a t t h e end of t h e p h o t o
e x p e r i m e n t . None o f t h e c o n t r o l s o l u t i o n s showed s i g n s o f
t h e r m a l r e a c t i o n . I s o l a t i o n of t h e p r o d u c t s i n v o l v e d
t r e a t m e n t o f t h e s o l u t i o n w i t h a c t i v a t e d c h a r c o a l and
b o i l i n g f o r 1 0 min. f o l l o w e d by g r a v i t y f i l t r a t i o n . A f t e r
c o o l i n g t h e s o l u t i o n was c o n c e n t r a t e d i n vacuo and t h e
r e s u l t i n g v i s c o u s o i l was t r e a t e d w i t h - c a . 50 mL MeOH and
f i l t e r e d t h r o u g h C e l i t e t o remove p o l y m e r i c b y p r o d u c t s .
T h i s s o l u t i o n was c o n c e n t r a t e d i n vacuo and t h e r e s i d u e
was d i s t i l l e d i n a K u g e l r o h r a p p a r a t u s t o y i e l d t h e c r u d e
p h o t o a d d u c t s . A n a l y t i c a l s a m p l e s were p u r i f i e d by f l a s h
chromatography o n s i l i c a g e l and c r y s t a l l i n e compounds
were r e c r y s t a l l i z e d f rom a s u i t a b l e s o l v e n t .
P r e p a r a t i o n o f Anhydromeva lono lac tone ( 6 )
( d l ) Meva lon ic l a c t o n e was d e h y d r a t e d and i s o m e r i z e d
by t h e method of sum8 t o g i v e a 78% y i e l d of d i s t i l l e d
a n h y d r o m e v a l o n o l a c t o n e , b o p . 85 -86O~/2 t o r r it* b o p .
7 4 - 7 6 0 ~ / . 9 t o r r ) , which was 99% p u r e by GLC; i r ( f i 1 m ) :
1 7 2 0 ( s ) , 1 6 4 0 ( m ) , 1400(m) , 1380(m) , 1310(m) , 1270(m) ,
1 2 2 5 ( s ) , 1 1 5 5 ( w ) , lOgO(w), 1 0 7 0 ( m ) , 1 0 0 0 ( w ) , 855(m) cm-1;
l H nmr(CDCl3)g: 1 . 8 7 ( 3 H , s ) , 2.25(2H, t r , 517 Hz), 4 .23(2Ht
tr, 5x7 Hz), 5.62(1Hf br s); uv(CH3CN):Xmax = 212 nm, =
9900 lm'lcm-1; ms(E1): 112(54, Mt), 82(100), 72(10),
Lactone - 6 was also prepared in 65% yield from
4-hydroxy-2-butanone by the procedure of White et a16 and
gave identical spectral data.
Preparation of 2-butenolide (8)
Lactone - 8 was prepared by a published method37 to give a 31% yield of - 8 which was 96% pure by GLC, bop. 95-980~/15 torr ( ~ i t 3 7 b.p. 10g0c/24 torr); ir(fi1m) :
1750(s), 1600(w), 1450(m), 1350(m), 1330(m), 1160(s),
1095(m), 1035(m), 890(m), 815(m) cm-l; IH nmr ( c D c ~ ~ ) ~ :
4.82(2Hf dd, J=2Hzf ~Hz), 6.02(1Hf dt, J=6Hzf 2Hz),
7.75(1Hf dt, J=6Hz, 3Hz); U V ( C H ~ C N ) : X ~ ~ X = 205 nm,
E = 12000 lm-1 cm-1; ms(C1, isobutane): 85(100, Mtl)
Preparation of 3,4,4-trimethyl-2-buten-1,4-olide (9)
a) 2,3-epoxy-2-methylbutane:
To a solution of 20.1 g(117 mmol, 1.0 eq) mCPBA in
200 mL freshly distilled diphenyl ether (bop. 121-122•‹C/10
Corr) was added dropwise 9.7 g(138 mmol, 1.2 eq) 2-methyl-
2-butene over 1 hr maintaining the temperature at 25-30•‹c
with an ice/water bath. After the addition the cold bath
was removed and the mixture stirred at room temperature
f o r 1 h r and t h e n a C02/acetone c o l d t r a p was a t t a c h e d t o
t h e f l a s k and t h e v o l a t i l e s drawn o u t o f t h e m i x t u r e w i t h
a n a s p i r a t o r vacuum (s. 20 t o r r ) f o r 1 h r . T h i s was
f o l l o w e d by mechan ica l pump e v a c u a t i o n ( c a . 5 t o r r ) f o r 1 2 - h r . The c o l d t r a p p e d v o l a t i l e s c o n t a i n i n g t h e u n r e a c t e d
s t a r t i n g material and t h e d e s i r e d e p o x i d e were t h e n
c a r e f u l l y f r a c t i o n a t e d t h r o u g h a 1 5 cm Vigreaux column a t
a t m o s p h e r i c p r e s s u r e . The f r a c t i o n b o i l i n g a t 70-73% was
c o l l e c t e d y i e l d i n g 5.65 g ( 5 6 % ) o f 2,3-epoxy-2-methylbutane
which was 95% p u r e by GLC; IH nmr(CDC13, 60 M H z ) S :
1.1(9H, b r m ) , 2.8(1Hr q , J=6 Hz).
b) 3,4,4-trimethylbutan-1,4-olide:
To 50 mL anhyd. e t h a n o l ( d i s t i l l e d from Mg) under
a r g o n a tmosphere was added 1 .29g(56 .3 mmol, 1.1 e q ) of
sodium metal. When t h e e v o l u t i o n of H2 ceased 8.59g(53.7
m m o l , 1 . 0 eq) d i e t h y l m a l o n a t e was added i n one p o r t i o n and
t h e m i x t u r e h e a t e d t o r e f l u x f o r 1 0 min. A s o l u t i o n o f
4 .40 g ( 5 1 . 1 mmol, 1 .0 e q ) o f 2,3-epoxy-2-methylbutane i n 5
mL anhyd. e t h a n o l was added t o t h e r e f l u x i n g m i x t u r e o v e r
1 h r and t h e r e s u l t i n g m i x t u r e was r e f l u x e d f o r 64 h r a t
which p o i n t GLC a n a l y s i s r e v e a l e d no f u r t h e r change i n t h e
- r e l a t i v e amount of s t a r t i n g m a t e r i a l . Heat ing was
d i s c o n t i n u e d and 2.15 g ( 5 3 . 7 mmol, 1 .05 e q ) NaOH i n 70 mL
Hz0 was added. The condense r was reset f o r downward
d i s t i l l a t i o n and t h e t h e o r e t i c a l amount of e t h a n o l removed
by d i s t i l l a t i o n . The r e s i d u e was c o o l e d t o 5% and
c a r e f u l l y a c i d i f i e d t o pH 2 w i t h c o n c e n t r a t e d HC1. T h i s
m i x t u r e was t h e n e x t r a c t e d w i t h 5 x 50 mL CH2C12. The
combined o r g a n i c ex t rac ts were d r i e d o v e r anhyd. MgS04,
f i l t e r e d and c o n c e n t r a t e d i n vacuo l e a v i n g 6.11 g . of a
w h i t e c r y s t a l l i n e mass, mop. 95-100•‹C. T h i s material was
h e a t e d i n a n o i l b a t h a t 130% t o i n d u c e d e c a r b o x y l a t i o n .
When t h e e v o l u t i o n o f C02 had c e a s e d t h e r e s i d u e was
c o o l e d and t h e n d i s t i l l e d t o y i e l d 4.22 g ( 6 5 % ) o f t h e
t i t l e compound, b o p . 1 2 4 - 1 2 6 0 ~ / 2 0 t o r r which was 98% p u r e
To a s o l u t i o n o f 30.8 mmol( l .2 e q ) LDA i n 200 mL
anhyd. THF ( p r e p a r e d i n t h e u s u a l way f rom 3.12 g
d i i s o p r o p y l a m i n e and 13 .9 mL 2.3 M n-BuLi) under Argon
a tmosphere a t -78% was added 3.29 g ( 2 5 . 7 m m o l , 1 .0 e q )
2,3-dimethylbutan-l,4-olide i n 70 mL THF over 20 min. The
r e s u l t i n g y e l l o w s o l u t i o n was s t i r r e d a t -78% f o r 1 h r
and t h e n a s o l u t i o n o f 6.39 g ( 3 3 . 4 mmol, 1 . 3 e q ) f8SeC1 and
5.06 g (28 .2 mmol, 1.1 e q ) HMPA i n 70 mL THF was added t o
t h e s t i r r e d e n o l a t e s o l u t i o n o v e r 1 0 min. The f8SeC1
s o l u t i o n was d e c o l o r i z e d immedia te ly on mixing . T h i s
s o l u t i o n was s t i r r e d a t -78% f o r 1 h r , t h e n warmed t o
room t e m p e r a t u r e and poured i n t o a c o l d aqueous s o l u t i o n
of NH4C1 and e x t r a c t e d w i t h 3 x 50 mL E t O A c . Combined
o r g a n i c ex t rac ts were washed w i t h 30 mL s a t . NaHC03, d r i e d
o v e r anhyd. MgS04 and f i l t e r e d . The clear y e l l o w f i l t r a t e
was t r e a t e d w i t h 6.7 mL(51.4 mmol, 2.0 e q ) 40% p e r a c e t i c
a c i d and t h e r e s u l t i n g t u r b i d w h i t e m i x t u r e was s t i r r e d a t
room t e m p e r a t u r e f o r 2 h r , t h e n p o u r e d i n t o 1 0 0 mL o f ice
water. The l a y e r s were s e p a r a t e d a n d t h e o r g a n i c l a y e r
was washed w i t h 30 mL 1 0 % NaHC03, 30 mL 1 0 % NaHS03,50 mL
s a t . NaC1, d r i e d o v e r anhyd. MgS04, f i l t e r e d and
c o n c e n t r a t e d i n vacuo . The r e s i d u e was d i s t i l l e d t o y i e l d
2.33 g ( 7 2 % ) of 2, b o p . 9 2 - 9 5 0 ~ / 1 0 t o r r which was 98% p u r e
by GLC; i r ( f i 1 m ) : l 7 5 O ( s ) , 1650(m) , 1 4 4 0 ( w ) , 1 3 9 0 ( w ) ,
1 3 2 0 ( w ) , 1 2 5 0 ( m ) , 1 1 8 0 ( m ) , 1 0 9 0 ( w ) , 9 7 5 ( m ) t 945(m) t
875(w)cm-1: 1~ nmr(CDCl3) 6 : 1.42(6H, s), 2 . 0 3 0 8 , d ,
13500 lm' lcm' l ; m s ( E 1 ) : 1 2 6 ( 5 , M t ) , 1 1 1 ( 2 0 ) , 8 3 ( 2 3 ) ,
6 8 ( l 2 ) , 5 5 ( 8 ) , 43 (1001 .
Anal . C a l c d . f o r C7H1002: C, 66.64; H , 7.99.
Found: C, 66.70; H , 8.01.
A. P h o t o a d d i t i o n of Anhydromeva lono lac tone ( 6 ) t o
A c r y l o n i t r i l e
1. Ambient T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.447 g ( 3 . 9 8 mmol, 1 .0 e q ) 5 , 2.10
mL(31.8 mmol, 8.0 e q ) a c r y l o n i t r i l e and 0.107 g undecane
( i n t e r n a l s t a n d a r d ) i n 200 mL a c e t o n i t r i l e was p l a c e d i n a
Pyrex immersion w e l l . T h i s s o l u t i o n was i r r a d i a t e d
t h r o u g h a Vycor f i l t e r and t h e r e a c t i o n fo l lowed by GLC
a n a l y s i s of a l i q u o t s removed a t r e g u l a r i n t e r v a l s . The
t e m p e r a t u r e of t h e s o l u t i o n was moni to red and it
s t a b i l i z e d a t 35-40% a f t e r 0.5 h r of i r r a d i a t i o n . GLC
a n a l y s i s r e v e a l e d a l l t h e s t a r t i n g l a c t o n e had been
consumed a f t e r 1 . 5 h r and two h i g h e r b o i l i n g p r o d u c t s were
p r e s e n t . The i n i t i a l (time=O) sample k e p t i n t h e d a r k
showed o n l y t h e s t a r t i n g m a t e r i a l and i n t e r n a l s t a n d a r d
p r e s e n t by GLC. The u s u a l workup f o l l o w e d by s h o r t p a t h
d i s t i l l a t i o n a t a n oven t e m p e r a t u r e of 90-1100~/0 .1 t o r r ,
y i e l d e d 0.534 g ( 7 7 % ) of a c o l o r l e s s o i l which GLC a n a l y s i s
showed t o be m a i n l y t h e two h i g h e r b o i l i n g p h o t o a d d u c t s - 1 0
and - 11 i n t h e r a t i o of 57:43 i n o r d e r of i n c r e a s i n g
r e t e n t i o n time. The r a t i o between t h e two p r o d u c t s was
obse rved t o be c o n s t a n t t h r o u g h o u t t h e i r r a d i a t i o n . A
p o r t i o n o f t h e m i x t u r e (0.412 g ) was s e p a r a t e d by repeated'
f l a s h chromatography on s i l i c a g e l ( 4 0 g ) u s i n g 4 : l
E t 2 O : E t O A c a s t h e e l u a n t . F r a c t i o n s c o n t a i n i n g main ly t h e /
f a s t e r e l u t i n g component were i s o l a t e d a s a n o i l which
c r y s t a l l i z e d on s t a n d i n g . ~ e c r y s t a l l i z a t i o n twice from
E t O H gave 0.178 g ( 2 7 % ) of a w h i t e c r y s t a l l i n e compound,
m.p. 77.5-79.50C which was shown t o be t h e minor , s l o w e r
e l u t i n g component 11 by GLC. The major component - 1 0 was
i s o l a t e d a s a n o i l , 0.224 g ( 3 3 % ) , which d i d n o t
crystallize. The material was 93% pure by GLC, the
remainder being predominantly - 11. The regio and
stereochemistry of the photoadducts were assigned from
analysis of 1~ nmr spectra and base isomerization
experiments as described in the results.
exo-8-~yano-6-methyl-3-oxabicyclo[4.2.0]octan-2-one - (10); - ir (KBr pellet): 2240(w), 1730(~), 1400(m) 1380(~),
1280(m), 1220(m), 1070(m), 900(m) cm-l; 1~ nmr(CDC1316:
4.52(2H, Cq, m); 1% nmr 6: 168.82(C=O), 119.15(CN),
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.402 g ( 3 . 5 8 m m o l , 1 . 0 e q ) 6,
1 .53 g ( 2 8 . 8 m m o l , 8 .0 e q ) a c r y l o n i t r i l e and 0.082 g
undecane i n 1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immersion well and t h e e n t i r e a p p a r a t u s p l a c e d i n a Dewar
f l a s k and c o o l e d t o - 4 0 0 ~ w i t h a n ace tone/C02 b a t h . Upon
i r r a d i a t i o n t h r o u g h a Vycor f i l t e r t h e t e m p e r a t u r e
s t a b i l i z e d a t - 2 0 0 ~ . GLC a n a l y s i s o f a l i q u o t s wi thdrawn
d u r i n g t h e c o u r s e of t h e i r r a d i a t i o n showed t h e l a c t o n e
had been consumed w i t h i n 2 h r . The u s u a l workup and
d i s t i l l a t i o n y i e l d e d 0.465 g ( 6 4 % ) o f a v i s c o u s y e l l o w o i l
which GLC a n a l y s i s r e v e a l e d t o b e m a i n l y ( 8 5 % )
p h o t o a d d u c t s - 1 0 + - 11. GLC and 1~ nmr a n a l y s i s showed
1 0 : l l t o be p r e s e n t i n t h e r a t i o o f 57:43. The r a t i o of 7 -
1 0 : l l was f o u n d by GLC t o b e c o n s t a n t t h r o u g h o u t t h e -- i r r a d i a t i o n .
3. S o l v e n t S t u d i e s - I r r a d i a t i o n o f 6 and A c r y l o n i t r i l e
i n E t h e r
A s o l u t i o n o f 0.218 g ( 1 . 9 4 rnmol, 1 .0 e q ) 6, 0.823 g
(15.5 m m o l , 8 .0 e q ) a c r y l o n i t r i l e and 0.082 g undecane i n
1 0 0 mL anhyd. e t h e r was p l a c e d i n a q u a r t z t o r u s reactor
and i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t ambien t
t e m p e r a t u r e . GLC a n a l y s i s of a l i q u o t s r e v e a l e d f o r m a t i o n
of a complex m i x t u r e , of which compounds - 1 0 and 11
a c c o u n t e d f o r o n l y 5% by GLC. T h e i r p r e s e n c e was
c o n f i r m e d by a mixed s a m p l e GLC e x p e r i m e n t . The d e c r e a s e
i n t h e amount of t h e s t a r t i n g l a c t o n e 5 r e l a t i v e t o
i n t e r n a l s t a n d a r d s t o p p e d a f t e r 2 h r o f i r r a d i a t i o n and
less t h a n 30% of - 6 was consumed. T h i s may have been d u e
t o t h e f o r m a t i o n of a p o l y m e r i c c o a t i n g o n t h e walls o f
t h e reactor.
4 . S o l v e n t S t u d i e s - I r r a d i a t i o n o f 6 and A c r y l o n i t r i l e
i n Ace tone
A s o l u t i o n of 0.239 g ( 2 . 1 3 m m o l , 1 . 0 eq) 5, 0.902 g
( 1 7 . 0 mmol, 8.0 e q ) a c r y l o n i t r i l e and 0.075 g undecane i n
1 0 0 mL s p e c . g r a d e acetone was p l a c e d i n a qua . r tz torus
reactor ( F i g . 5 ) and i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t
a m b i e n t t e m p e r a t u r e . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d
t h e f o r m a t i o n of a complex m i x t u r e i n which compounds 10 a n d - 11 a c c o u n t e d f o r less t h a n 3% by GLC. The consumpt ion
o f t h e l a c t o n e - 6 s t o p p e d a f t e r 1 . 5 h r o f i r r a d i a t i o n
l e a v i n g - ca. 60% of - 6 u n r e a c t e d a n d a d e n s e p o l y m e r i c
c o a t i n g on t h e r e a c t o r walls.
5. S o l v e n t S t u d i e s - I r r a d i a t i o n o f 6 and
A c r y l o n i t r i l e i n I s o p r o p a n o l
A s o l u t i o n o f 0.320 g ( 2 . 8 5 mmol, 1 . 0 e q ) - 6, 1 .21 g
( 2 2 . 8 mmol, 8.0 eq) a c r y l o n i t r i l e and 0.062 g undecane i n
1 0 0 mL HPLC g r a d e i s o p r o p a n o l was p l a c e d i n a q u a r t z
t o r u s r e a c t o r and i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t
ambien t t e m p e r a t u r e . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d
t h e f o r m a t i o n of a complex m i x t u r e i n which compounds 1 0 - and 11 were n o t d e t e c t e d . The consumpt ion of t h e l a c t o n e - 6 s t o p p e d a f t e r 3 h r of i r r a d i a t i o n l e a v i n g c a . 40% - 7
u n r e a c t e d and a d e n s e p o l y m e r i c c o a t i n g on t h e lamp
jacket. Mixed sample GLC e x p e r i m e n t showed p h o t o a d d u c t s
1 0 + 11 were p r e s e n t as minor components (<.I%) i n t h e - - c r u d e m i x t u r e a f t e r workup.
6. F i l t e r E x p e r i m e n t s - Use of a Corex F i l t e r i n
I r r a d i a t i o n o f 6 and A c r y l o n i t r i l e
A s o l u t i o n o f 0.254 g (2 .26 mmol, 1 . 0 eq) - 6, 0.960 g
( 1 8 . 1 mmol, 8 eq) a c r y l o n i t r i l e and 0.092 g undecane i n
1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex immersion well
and i r r a d i a t e d t h r o u g h a Corex f i l t e r (50% t r a n s m i s s i o n @
. 290 nm). GLC a n a l y s i s o f a l i q u o t s r e v e a l e d no consumpt ion
o f s t a r t i n g material. After 2 h r o f i r r a d i a t i o n t h e
s o l u t i o n was t r e a t e d w i t h c h a r c o a l , f i l t e r e d and
c o n c e n t r a t e d i n vacua . The l a c t o n e 6 was r e c o v e r e d - q u a n t i t a t i v e l y .
7. F i l t e r E x p e r i m e n t s - Use o f a P y r e x F i l t e r i n
I r r a d i a t i o n o f 6 w i t h , A e r y l o n i t r i l e
Us ing a p r o c e d u r e i d e n t i c a l t o t h e p r e v i o u s case a
s o l u t i o n o f 5, a c r y l o n i t r i l e and i n t e r n a l s t a n d a r d was
i r r a d i a t e d t h r o u g h a Pyrex f i l t e r (50% t r a n s m i s s i o n
@ 305 nm) f o r 2 h r . GLC a n a l y s i s r e v e a l e d no r e a c t i o n .
I d e n t i c a l workup q u a n t i t a t i v e l y y i e l d e d t h e s t a r t i n g
l a c t o n e .
8. A t t empted P h o t o i s o m e r i z a t i o n o f 1 0
A s o l u t i o n o f 0.033 g - 1 0 i n 1 0 mL a c e t o n i t r i l e was
p l a c e d i n a q u a r t z t e s t t u b e e q u i p p e d w i t h a n i t r o g e n
b u b b l e r and t a p e d t o t h e s i d e o f t h e lamp jacket. T h i s
s o l u t i o n was i r r a d i a t e d f o r 1 h r t h r o u g h a Vycor f i l t e r .
GLC a n a l y s i s r e v e a l e d o n l y - 1 0 p r e s e n t . Removal o f t h e
s o l v e n t i n v a c u o r e s u l t e d i n q u a n t i t a t i v e r e c o v e r y o f 2.
9. At t empted P h o t o i s o m e r i z a t i o n o f 11
A s o l u t i o n of 0.027 g o f ll, which was 95:5 1 0 : l l
by GLC, i n 1 0 mL of a c e t o n i t r i l e was p l a c e d i n a q u a r t z
t es t t u b e e q u i p p e d w i t h a n i t r o g e n b u b b l e r and t a p e d t o
t h e s i d e o f t h e lamp j a c k e t . T h i s s o l u t i o n was i r r a d i a t e d
f o r 1 h r t h r o u g h a Vycor f i l t e r . GLC a n a l y s i s r e v e a l e d
t h e r a t i o of -- 1 0 : l l t o be unchanged. Removal of t h e
s o l v e n t i n vacuo r e s u l t e d i n q u a n t i t a t i v e r e c o v e r y of
1 0 and 11 i n t h e i n i t i a l r a t i o . - -
1 0 . Base I s o m e r i z a t i o n o f 1 0 and 11
To a s o l u t i o n o f 0.015 g - 1 0 and 0.011 g undecane i n
1 0 mL anhyd. e t h a n o l was added 2 mL 1 . 2 M N a O E t . The
r e s u l t i n g s o l u t i o n was s t i r r e d a t room t e m p e r a t u r e under
N2 w h i l e 0.1 mL a l i q u o t s were removed a t i n t e r v a l s and
e a c h quenched by a d d i t i o n t o 2 mL o f 5% HC1. T h i s m i x t u r e
was e x t r a c t e d w i t h Et2O and t h e o r g a n i c extract was washed
w i t h s a t . NaHC03, d r i e d o v e r anhyd. Na2S04 and f i l t e r e d .
The r e s u l t i n g s o l u t i o n was a n a l y s e d by GLC which r e v e a l e d
t h a t a m i x t u r e o f -- 1 0 : l l i n t h e r a t i o o f 80:20 had been
formed w i t h i n 1 5 min. The r a t i o d i d n o t change o v e r 2
h r . The r e a c t i o n components were i d e n t i f i e d as - 1 0 and 2
by mixed s a m p l e GLC e x p e r i m e n t s .
A sample o f - 11 t r e a t e d i n a n i d e n t i c a l manner was
found t o i s o m e r i z e t o a m i x t u r e o f 1 0 : l l i n t h e r a t i o of -- 80:20 w i t h i n 30 min. Mixed sample GLC e x p e r i m e n t s
c o n f i r m e d t h e i d e n t i t y o f t h e 2 components p r e s e n t as 10 and 11. -
T h i s e x p e r i m e n t was r e p e a t e d o n a sample o f - 1 0 u s i n g
e t h a n o l D6 as a s o l v e n t a n d a n a l y s i s o f t h e e q u i l i b r i a t e d
11. Attempted Alumina C a t a l y s e d I s o m e r i z a t i o n of 1 0
A 0.025 g sample o f - 1 0 was p l a c e d o n column of
2.0 g n e u t r a l Alumina ( a c t i v i t y I ) and e l u t e d w i t h
CHC13 ( 1 5 mL). Removal o f t h e s o l v e n t gave 0.020 g of
material which mixed sample GLC e x p e r i m e n t s showed t o be
e x c l u s i v e l y compound - 1 0 . A 0.050 g sample of compound - 11
was t r e a t e d i n a s imi l a r manner and was r e c o v e r e d ( 8 0 % )
unchanged. The 1~ nmr s p e c t r a of t h e s e s a m p l e s were
i d e n t i c a l t o t h e m a t e r i a l s b e f o r e a lumina t r e a t m e n t .
B. P h o t o a d d i t i o n of a - c h l o r o a c r y l o n i t r i l e to
1. Ambient Tempera ture P h o t o l y s i s
A s o l u t i o n of 0.322 g (2 .87 m m o l , 1 .0 e q ) 6 , 2.01 g
( 2 3 . 0 mmol, 8.0 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.087 g
undecane i n 200 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immersion w e l l and i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t
ambien t t e m p e r a t u r e . The t e m p e r a t u r e of t h e s o l u t i o n
s t a b i l i z e d a t 40•‹C a f t e r 0.5 h r o f i r r a d i a t i o n . GLC
a n a l y s i s of a l i q u o t s r e v e a l e d t h a t t h e s t a r t i n g
l a c t o n e - 6 had been consumed a f t e r 4 h r . The u s u a l workup
g a v e a v i s c o u s brown o i l which c r y s t a l l i z e d o n s t a n d i n g
and was r e c r y s t a l l i z e d twice from e t h a n o l t o y i e l d
0.310 g ( 5 4 % ) of l i g h t y e l l o w n e e d l e s , m.p. 94-96%. GLC
a n a l y s i s of t h i s m a t e r i a l r e v e a l e d o n l y two compounds,
1 2 + 1 3 , i n t h e r a t i o o f 58:42 i n o r d e r o f i n c r e a s i n g - - r e t e n t i o n t i m e . The r a t i o o f t h e two compounds was found
t o be c o n s t a n t t h r o u g h o u t t h e c o u r s e o f t h e i r r a d i a t i o n .
The two p h o t o a d d u c t s were u n r e s o l v e d by TLC and f l a s h
ch romatography . The IH a n d 13c s p e c t r a were a s s i g n e d o n
t h e b a s i s o f r e l a t i v e i n t e n s i t i e s o f t h e s i g n a l s , which
were i n a g r e e m e n t w i t h t h e r e l a t ive p r o p o r t i o n s found by
GLC. The 1 3 ~ nmr a s s i g n m e n t s m u s t be viewed w i t h c a u t i o n
s i n c e t h e isomer r a t i o (12 :13 ) -- is n e a r l y u n i t y . Due t o
N u c l e a r O v e r h a u s e r e f f e c t s t h e i n t e n s i t i e s o f 1 3 ~ s i g n a l s
are n o t a d i r e c t measu re o f t h e r e l a t i v e abundance o f a
p a r t i c u l a r c a r b o n i n a m i x t u r e . I r ( K B r p e l l e t ) : 2240(w) ,
Major isomer - 12 : 1~ nrnr(CDC13) 6 : 1 .48(3H, CH3, s ) ,
1.8-2.2(2Hf Cg, m ) , 2.70(1Hf C7, dd , 5 ~ 1 3 . 8 H Z f 0 .8 HZ)
3.07(1Hf c 7 , d d , J=13 .8 Hz, 1 . 2 Hz), 3 . 4 6 ( 1 ~ , C 1 , b r s ) ,
1 1 2 ( 2 8 ) , 9 3 ( 2 8 ) , 8 2 ( 1 0 0 ) *
Minor isomer - 13 : IH n m r ( C ~ C 1 3 ) 6 : 1 .44(3Hf CH3, s ) ,
1.9-2.1(2Hf C5, m ) , 2.78(1Hf C7, dd , 5-14.4 Hz, 1 .4 H z ) ,
3.02(1HI C7, d d , 5 ~ 1 4 . 4 H Z f 1 .2 H Z ) , 3.68(1Hf C 1 , dd ,
1 1 2 ( 2 4 ) , 1 0 4 ( 4 1 ) , 8 2 ( 7 8 ) , 6 5 ( 2 2 ) .
MS o f m i x t u r e ( C 1 , i s o b u t a n e , d i r e c t p r o b e ) : 2 0 2 ( 3 2 ,
M+3), 2 0 0 ( 1 0 0 , M+1), 1 6 6 ( 8 ) , 1 6 4 ( 6 ) .
Ana l . (of m i x t u r e ) C a l c d . f o r CgHloNO2Cl: C, 54 .15 ;
H , 5 .05; N , 7 .02. Found: C , 54 .12 ; H , 4.98; N , 6.84.
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.249 g ( 2 . 3 1 m m o l , 1 . 0 eq) - 6 , 1 .62 g
( 1 8 . 5 mmol, 8 .0 eq) a - c h l o r o a c r y l o n i t r i l e and 0 .067 g
u n d e c a n e i n 200 mL a c e t o n i t r i l e was p l a c e d i n a P y r e x
i m m e r s i o n w e l l a n d c o o l e d t o -40•‹c i n a n ace tone /C02
b a t h . T h i s s o l u t i o n was i r r a d i a t e d t h r o u g h a Vycor f i l t e r
a n d t h e t e m p e r a t u r e o f t h e s o l u t i o n s t a b i l i z e d a t -20•‹C
a f t e r 30 min. GLC a n a l y s i s o f a l i q u o t s r e v e a l e d t h a t t h e
l a c t o n e - 6 h a d b e e n consumed a f t e r 3.5 h r . The u s u a l
workup g a v e a v i s c o u s y e l l o w o i l wh ich c r y s t a l l i z e d o n
s t a n d i n g . R e c r y s t a l l i z a t i o n f r o m t o l u e n e y i e l d e d 0.284
g ( 6 2 % ) o f l i g h t y e l l o w n e e d l e s , mop. 94 .5 -96O~ . GLC a n d
1~ nmr a n a l y s i s showed t h i s material t o b e a m i x t u r e of
t h e d i a s t e r e o m e r i c p h o t o a d d u c t s 12 and - 1 3 i n t h e r a t i o o f
57:43. The r a t i o o f t h e two a d d u c t s was f o u n d t o b e
c o n s t a n t i n a l l t h e a l i q u o t s t a k e n d u r i n g t h e i r r a d i a t i o n .
3. F i l t e r S t u d i e s - Use of a P y r e x F i l t e r i n I r r a d i a t i o n
of 6 and a - c h l o r o a c r y l o n i t r i l e
A s o l u t i o n o f 0.575 g ( 5 . 1 3 mmol, 1 .0 e q ) 6 , 3.32 g
(38 .0 mmol, 7.4 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.102 g
undecane i n 200 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immersion well and i r r a d i a t e d t h r o u g h a Pyrex f i l t e r a t
ambien t t e m p e r a t u r e f o r 2 h r . GLC a n a l y s i s of a l i q u o t s
r e v e a l e d many minor p r o d u c t s formed b u t t h a t - ca. 95% o f
t h e l a c t o n e remained u n r e a c t e d . The Pyrex f i l t e r was
r e p l a c e d w i t h a Corex f i l t e r and t h e s o l u t i o n i r r a d i a t e d
f o r an a d d i t i o n a l 2 h r . GLC a n a l y s i s r e v e a l e d t h a t - ca.
90% of t h e l a c t o n e - 6 remained u n r e a c t e d . T rea tmen t o f t h e
y e l l o w s o l u t i o n w i t h c h a r c o a l , c o n c e n t r a t i o n i n vacuo and
b u l b t o b u l b d i s t i l l a t i o n gave 0.471 g ( 8 2 % ) of l a c t o n e 5 which was 93% p u r e by GLC.
4 . S o l v e n t S t u d i e s - I r r a d i a t i o n o f 6 and
a - c h l o r o a c r y l o n i t r i l e i n Ace tone
A s o l u t i o n o f 0.578 g ( 5 . 1 6 mmol, 1 .0 e q ) 5, 4.51 g
(51.6 mmol, 1 0 e q ) a - c h l o r o a c r y l o n i t t i l e and 0.113 g
undecane i n 200 mL s p e c . g r a d e a c e t o n e was p l a c e d i n a
Pyrex immers ion well and i r r a d i a t e d t h r o u g h a Pyrex f i l t e r
a t ambient t e m p e r a t u r e f o r 2 h r . GLC a n a l y s i s o f a l i q u o t s
r e v e a l e d t h e f o r m a t i o n o f a complex m i x t u r e of p r o d u c t s
and E. 90% o f - 6 u n r e a c t e d . The Pyrex f i l t e r was r e p l a c e d
w i t h a Vycor f i l t e r and t h e s o l u t i o n i r r a d i a t e d f o r a n
a d d i t i o n a l 3 h r . GLC a n a l y s i s showed a complex m i x t u r e o f
p r o d u c t s w i t h - ca. 80% of - 6 u n r e a c t e d . GLC a n a l y s i s of t h e
i n i t i a l ( t i m e = O ) s ample k e p t i n t h e d a r k r e v e a l e d o n l y
u n r e a c t e d s t a r t i n g m a t e r i a l s .
5. S o l v e n t S t u d i e s - E t h e r
A s o l u t i o n o f 0.446 g ( 3 . 9 8 m m o l , 1 .0 e q ) 5, 2.60 g
(29 .8 mmol, 7 .5 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.092 g
undecane i n 200 mL anhyd. e t h e r was p l a c e d i n a Pyrex
immers ion well and i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t
ambien t t e m p e r a t u r e f o r 3 h r . GLC a n a l y s i s r e v e a l e d t h e
f o r m a t i o n o f a complex m i x t u r e of a p r o d u c t s and - ca. 60%
of u n r e a c t e d - 6. GLC a n a l y s i s o f t h e i n i t i a l ( t i m e = O )
s a m p l e k e p t i n t h e d a r k r e v e a l e d o n l y u n r e a c t e d s t a r t i n g
material.
6. S o l v e n t S t u d i e s - I r r a d i a t i o n o f 6 and
a - c h l o r o a c r y l o n i t r i l e i n Methanol
A s o l u t i o n o f 0.307 g (2 .74 mmol, 1 . 0 e q ) - 6, 1 .80 g
( 2 0 . 5 mmol, 7 .5 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.083 g
undecane i n 200 mL HPLC g r a d e me thano l was p l a c e d i n a
Pyrex immersion well and i r r a d i a t e d t h r o u g h a Vycor f i l t e r
a t ambien t t e m p e r a t u r e f o r 4 h r . GLC a n a l y s i s r e v e a l e d
t h e f o r m a t i o n of a complex m i x t u r e of p r o d u c t s and z. 70%
of unreacted - 6. GLC ana ly s i s of the i n i t i a l (time=O)
sample kept i n t he dark showed only unreacted s t a r t i n g
mate r ia l s .
C. Photoaddit ion of a -ace toxyacry lon i t r i l e t o
1. Ambient Temperature Photolys is
A s o l u t i o n of 0.902 g(8.05 mmol, 1.0 eq ) - 6, 5.0 g
(45 mmol, 5.6 eq ) a - ace toxyac ry lon i t r i l e and 0.085 g
t r idecane i n 200 mL a c e t o n i t r i l e was placed i n a Pyrex
immersion w e l l and i r r a d i a t e d through a Vycor f i l t e r f o r
24 hr a t ambient temperature. The temperature of the
so lu t i on s t a b i l i z e d a t 40% a f t e r 1 hour of i r r ad i a t i on .
The usual workup and shor tpa th d i s t i l l a t i o n (bulb temp
125-1400~/.3 t o r r ) yielded 1.05 g(56%) of a viscous yellow
o i l which GLC ana ly s i s revealed t o be a m i x t u r e of three
compounds, - - - 1 4 , 15, 16 i n t h e r a t i o of 3.4:3.8:1. This
mixture gave only one spo t on TLC and was unresolved by
f l a s h chromatography a s well as reverse phase HPLC.
Reduction of t he temperature of t h e i n j e c t i o n po r t from
275% t o 225% before a GLC ana ly s i s r e su l t ed i n the
e l iminat ion of t he f a s t e s t e l u t i n g compound - 1 4 from the
GLC t r a c e and t h e r a t i o of the two remaining adducts - 15
and - 1 6 was found t o be 3: 2 i n order of increas ing
r e t en t i on time. T h i s was cons i s ten t with 1~ and 1 3 ~ nmr
a n a l y s i s o f t h e m i x t u r e . P r e p a r a t i v e GLC o f t h e m i x t u r e
r e s u l t e d i n t h e i s o l a t i o n o f t h e f a s t e s t e l u t i n g compound,
1 4 , which was i d e n t i f i e d b y 1 H nmr spec t ra l a n a l y s i s 7
( b e l o w ) as t h e r i n g opened e l i m i n a t i o n p r o d u c t ,
4-Cyano-6-methyloxacycloocta-3,5-diene-2-one.
B e c a u s e o f t h e p r e d o m i n a n c e o f t h e f a s t e r e l u t i n g
a d d u c t - 1 5 it was p o s s i b l e t o a s s i g n t h e IH and 1% nmr
spectra o f t h e m i x t u r e by u s i n g ( w i t h c a u t i o n i n t h e case
o f 1%) t h e r e l a t i v e i n t e n s i t i e s . The s t e r e o c h e m i s t r y a t
C7 was a s s i g n e d b y c o m p a r i s o n o f c h e m i c a l s h i f t o f t h e
m e t h y l r e s o n a n c e s as d e s c r i b e d i n t h e R e s u l t s and
D i s c u s s i o n .
4-Cyano-6-methyloxacycloocta-3,5-diene-2-one 1 4 - 1 ; 1 H
n m r ( C ~ C 1 3 ) d : 2.12(3H, CH3, s ) , 2.57(2H, C3, t r , J = 7 H Z ) ,
4 .40(2H, C2, t r , J = 7 Hz) , 6 .02(1H, Cg, s ) , 6.37(1H, C7,
s ) t ms(c1, I s o b u t a n e ) : 1 6 5 ( 1 1 , M+2), 1 6 4 ( 1 0 0 , M t l ) .
CH3, s), 1 . 7 - 1 .8 (2H, Cg, m ) , 2 . 15 (38 , CH3, $ 1 , 2 .53(18 ,
3.55(1H, C 1 , t r , J = 1 . 6 H z ) , 4.3-4.4(2H, Cq, m ) ; 1%
66.30(C8, s,), 66.11(C4, tr), 51.85(C1, dl, 43.61(C7, tr),
33.12(C5, tr), 32.64(C6, s), 27.58(CH3, q), 20.33(CH3, q);
ms(C1, Isobutane): 225(13, M+2), 224(100, M+l), 182(8).
endo-8-Acetoxy-8-cyano-6-methyl-3-oxabicyclo - [4.2.O]octan-2-one(l6); - 1~ nmr (CDCl3) 6 : 1.36(3H,
CH3, s), 1.8-1.9(2H, Cg, m), 2.13(3H, CH3, s), 2.34(1H,
C7, dd, J= 14 Hz, 0.8 Hz), 2.97(1H, C7, dd, 53 14 HZ, 1
tr), 31.91(C6, s), 27.18(CH3, q), 20.31(CH3, q); ms(C1,
Isobutane): 225(14,Mt2), 224(100, Mtl), l66(8), l64(16).
Anal. (of mixture) Calcd. for CllH13N04: C, 59.19; H,
5.87; N, 6.28. Found: C, 59.09; H, 5.85; N, 6.06.
2. Low temperature Photolysis
A solution of 0.224 g(2.00 mmol, 1.0 eq) - 6, 1.33 g
(12 mmol, 6.0 eq) a-acetoxyacrylonitrile and 0.056 g
undecane in 200 mL acetonitrile was placed in a Pyrex
immersion well and cooled to -40•‹c with an acetone/C02
bath and irradiated through a Vycor filter for 8 hr. The
temperature of the solution stabilized at -2S0c after 0.5
hr. GLC analysis of aliquots was performed with the
injection port temperature at 2250~. The usual workup and
shortpath distillation yielded 0.285 g(64%) of a viscous
y e l l o w o i l which b o t h GLC and 1~ nmr a n a l y s i s r e v e a l e d t o
be a m i x t u r e of - 1 5 and - 1 6 i n t h e r a t i o of - c a . 3:2. W i t h i n
e x p e r i m e n t a l e r ro r t h i s r a t i o was found t o be f a i r l y
c o n s t a n t d u r i n g t h e i r r a d i a t i o n .
P h o t o a d d i t i o n of a c r y l o n i t r i l e t o 2 - p e n t e n o l i d e ( 7 )
1. Ambient Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.369 g (3 .76 mmol, 1 . 0 e q )
2 - p e n t e n o l i d e ( Z ) , 1 .670 g ( 3 1 . 5 mmol, 8.4 e q ) a c r y l o n i t r i l e
and 0.108 g undecane i n 150 mL a c e t o n i t r i l e was p l a c e d i n
a Vycor t o r u s r e a c t o r and i r r a d i a t e d a t ambient
t e m p e r a t u r e f o r 5 .5 h r . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d
t h e g r a d u a l f o r m a t i o n of two p r o d u c t s , 17 and - 1 8 i n t h e
r a t i o of 53:47 i n o r d e r of i n c r e a s i n g r e t e n t i o n time. The
r a t i o between t h e two p r o d u c t s was found t o be c o n s t a n t
t h r o u g h o u t t h e i r r a d i a t i o n . GLC a n a l y s i s of t h e i n i t i a l
( t i m e = O ) sample k e p t i n t h e d a r k r e v e a l e d o n l y u n r e a c t e d
s t a r t i n g materials. The u s u a l workup and s h o r t p a t h
d i s t i l l a t i o n y i e l d e d 0.568 g ( 6 5 % ) of a v i s c o u s y e l l o w o i l
which was p r e d o m i n a n t l y compounds - 1 7 and - 1 8 i n t h e r a t i o
of 55:45 by GLC. T h i s m i x t u r e e x h i b i t e d one s p o t on TLC
and was u n r e s o l v e d by f l a s h chromatography and HPLC. The
s i g n a l s i n t h e 1~ nmr spec t rum of t h e m i x t u r e were
u n a s s i g n a b l e d u e t o o v e r l a p of s i g n a l s b u t t h e s i g n a l s i n
t h e 1% nmr s p e c t r a were a s s i g n e d by compar ison of t h e
s p e c t r a a f t e r b a s e e q u i l i b r i a t i o n ; i r ( f i l m ) : 2250(w) ,
28.20(C7, t r ) , 24.62(C6, d ) ; ms(C1, i s o b u t a n e ) :
27.51(C7, t r ) , 23.54(C6, d ) ; m s ( C 1 , i s o b u t a n e ) : 1 5 3 ( 8 ,
M+2), 1 5 2 ( 1 0 0 , M+1).
Anal . o f m i x t u r e , C a l c d . f o r CgHgN02: C , 63.56; H I
6.00; N , 9.27. Found: C, 63.32; H, 5.83; N , 9.08.
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.350 g ( 3 . 5 7 m m o l , 1 . 0 e q )
2 - p e n t e n o l i d e , 1 .518 g ( 2 8 . 6 m m o l , 8.0 e q ) a c r y l o n i t r i l e
and 0.111 g undecane i n 200 mL a c r y l o n i t r i l e was p l a c e d i n
a Pyrex immersion well a n d c o o l e d t o - 4 0 0 ~ w i t h an
ace tone/C02 b a t h and i r r a d i a t e d t h r o u g h a Vycor f i l t e r f o r
2 h r . The u s u a l workup and s h o r t p a t h d i s t i l l a t i o n y i e l d e d
a v i s c o u s y e l l o w o i l which c r y s t a l l i z e d on s t a n d i n g .
R e c r y s t a l l i z a t i o n from i s o p r o p a n o l y i e l d e d 0.327 g ( 6 0 % ) o f
l i g h t y e l l o w n e e d l e s , m.p. 1 2 4 - 1 2 7 0 ~ . GLC a n a l y s i s o f
t h i s m a t e r i a l r e v e a l e d it t o be 17:I.J i n t h e r a t i o o f
60:40. T h i s r a t i o was found t o b e c o n s t a n t t h r o u g h o u t t h e
i r r a d i a t i o n .
3. Base I s o m e r i z a t i o n of 1 7 and 1 8
To a s o l u t i o n of 0.102 g o f t h e c r y s t a l l i n e m i x t u r e
of -- 17:18 (60 :40) i n 30 mL anhyd. e t h a n o l was added 1 0 mL
1 .2 M N a O E t and t h e r e s u l t i n g s o l u t i o n s t i r r e d a t ambient
t e m p e r a t u r e . 0 .1 mL a l i q u o t s were t a k e n a t i n t e r v a l s ,
worked u p and a n a l y s e d as b e f o r e t o r e v e a l t h a t a m i x t u r e
o f -- 17:18 i n t h e r a t i o o f 75:25 had been formed w i t h i n 30
min. T h i s r a t i o d i d n o t change o v e r 2 h r . A f t e r 2 h r a t
ambient t e m p e r a t u r e , t h e r e m a i n i n g b a s i c s o l u t i o n was
c a r e f u l l y n e u t r a l i z e d w i t h 2 N HC1 and t h e s o l v e n t removed
under vacuum. The r e s i d u e was d i s s o l v e d i n 30 mL E t a 0 and
washed w i t h 2x10 mL H20 and 1 5 mL s a t . NaHC03. The
o r g a n i c e x t r a c t was d r i e d o v e r anhyd. MgS04, f i l t e r e d and
c o n c e n t r a t e d i n vacuo . The r e s i d u e was p u r i f i e d by
s h o r t p a t h d i s t i l l a t i o n t o y i e l d 0.085 g ( 8 3 % ) of a v i s c o u s
y e l l o w o i l which mixed s a m p l e GLC a n a l y s i s r e v e a l e d t o be
a m i x t u r e o f -- 17:18 i n t h e r a t i o o f 73:27.
4 . At tempted P h o t o i s o m e r i z a t i o n o f 1 7 and 1 8
A s o l u t i o n o f 0.055 g o f t h e m i x t u r e of -- 15:18 i n t h e
r a t i o of 73:27, a n d 0.15 g undecane i n 1 0 mL a c e t o n i t r i l e
was p l a c e d i n a q u a r t z t e s t t u b e and t a p e d t o t h e s i d e o f
t h e lamp j a c k e t . T h i s s o l u t i o n was i r r a d i a t e d t h r o u g h a
Vycor f i l t e r f o r o n e h o u r . GLC a n a l y s i s of t h e s o l u t i o n
r e v e a l e d no c h a n g e i n t h e r e l a t i v e amounts of - 1 7 and - 1 8
d u r i n g t h e c o u r s e o f t h e i r r a d i a t i o n . The sample was
r e c o v e r e d by t r e a t i n g t h e s o l u t i o n w i t h c a . 1 g a c t i v a t e d - c h a r c o a l , f i l t e r i n g and c o n c e n t r a t i o n i n vacuo t o y i e l d
0.058 g of a v i s c o u s y e l l o w o i l .
E. P h o t o a d d i t i o n of a - c h l o r o a c r y l o n i t r i l e t o
1. Ambient Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.220 g (2 .24 m m o l , 1 .0 e q )
2 - p e n t e n o l i d e , 0.976 g (11 .2 m m o l , 5 .0 e q )
a - c h l o r o a c r y l o n i t r i l e and 0.107 g undecane i n 150 mL
a c e t o n i t r i l e was p l a c e d i n a Vycor t o r u s reactor and
i r r a d i a t e d a t a m b i e n t t e m p e r a t u r e . GLC a n a l y s i s of
a l i q u o t s showed t h a t t h e consumpt ion o f t h e l a c t o n e 2 c e a s e d a f t e r 2 h r o f i r r a d i a t i o n l e a v i n g ca. 70% - u n r e a c t e d . A s w e l l a complex m i x t u r e dominated by two
p r o d u c t s was p roduced . Extended i r r a d i a t i o n i n c r e a s e d
t h e c o m p l e x i t y o f t h e m i x t u r e . The r a t i o o f t h e two
p r i n c i p a l p r o d u c t s -- 19:20 was found t o be 40:60 and
c o n s t a n t t h r o u g h o u t t h e i r r a d i a t i o n . GLC a n a l y s i s of t h e
i n i t i a l ( t i m e = O ) s ample k e p t i n t h e d a r k r e v e a l e d o n l y
u n r e a c t e d s t a r t i n g materials.
2. Low Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.205 g (2 .09 mmol, 1 .0 e q )
2 - p e n t e n o l i d e , 0.727 g ( 8 . 3 0 mmol, 4 .0 e q )
a - c h l o r o a c r y l o n i t r i l e a n d 0.066 g undecane i n 150 mL
a c e t o n i t r i l e was p l a c e d i n a P y r e x immersion well, c o o l e d
t o -30% a n d i r r a d i a t e d t h r o u g h a Vycor f i l t e r . The
t e m p e r a t u r e of t h e s o l u t i o n s t a b i l i z e d a t -20% a f t e r
0.5 h r o f i r r a d i a t i o n . GLC a n a l y s i s of a l i q u o t s r e v e a l e d
t h e consumpt ion of t h e l a c t o n e c e a s e d a f t e r 4.5 h r of
i r r a d i a t i o n l e a v i n g E. 30% u n r e a c t e d . A s well a complex
m i x t u r e of p r o d u c t s d o m i n a t e d by 2 and - 20 was produced .
The r a t i o of t h e s e two p r o d u c t s was c o n s t a n t t h r o u g h o u t
t h e i r r a d i a t i o n a n d found t o be 35:65. The u s u a l workup
and s h o r t p a t h d i s t i l l a t i o n y i e l d e d 0.127 g of a y e l l o w o i l
which was a complex m i x t u r e o f t h e s t a r t i n g l a c t o n e and
p h o t o p r o d u c t s by GLC. The p r o d u c t s - 1 9 and 20 were - s e p a r a t e d from t h e s t a r t i n g l a c t o n e by f l a s h
ch romatography o n s i l i c a g e l t o y i e l d , a f t e r s h o r t p a t h
d i s t i l l a t i o n , a v i s c o u s y e l l o w o i l which weighed 0.0931
g ( 2 9 % ) . GLC a n a l y s i s r e v e a l e d t h e o i l t o be a m i x t u r e of
1 9 and 20 i n t h e r a t i o o f 40:60. Repea ted f l a s h - - chromatography o n S i l i c a G e l u s i n g a c e t o n i t r i l e : t o l u e n e
1:9 as t h e e l u a n t p a r t i a l l y r e s o l v e d t h e m i x t u r e i n t o two
f r a c t i o n s , o n e c o n t a i n i n g a 20:80 m i x t u r e o f -- 19:20 and t h e
o t h e r a 70:30 m i x t u r e o f -- 19:20. T h i s d e g r e e o f e n r i c h m e n t
i n e a c h component a l l o w e d t h e s i g n a l s i n t h e 1 3 ~ nmr
s p e c t r a o f e a c h component t o be a s s i g n e d ; i r ( f i 1 m ) of
c r u d e m i x t u r e : 2250(w) , 1 7 3 0 ( s ) , 1 4 9 0 ( w ) , 1 4 4 0 ( w ) ,
3. At t empted P h o t o i s o m e r i z a t i o n of 1 9 and 20
A s o l u t i o n o f 0.024 g o f t h e c h r o m a t o g r a p h i c f r a c t i o n
c o n t a i n i n g -- 19:20 i n t h e r a t i o o f 70:30 and 0.015 g
undecane i n 1 0 mL a c e t o n i t r i l e was p l a c e d i n a q u a r t z t e s t
t u b e e q u i p p e d w i t h a N2 b u b b l e r and t a p e d t o t h e s i d e o f
t h e lamp j a c k e t . T h i s s o l u t i o n was i r r a d i a t e d th rough a
Vycor f i l t e r f o r 2 h r a t a m b i e n t t e m p e r a t u r e . GLC
a n a l y s i s showed a h o s t of minor p r o d u c t s n o t p r e s e n t i n
t h e o r i g i n a l sample and t h a t t h e r a t i o o f 19 t o 20 had
changed t o 67:33. Comparison of t h e areas t o t h e i n t e r n a l
s t a n d a r d r e v e a l e d t h a t E. 5% o f e a c h i somer had
decomposed d u r i n g t h e i r r a d i a t i o n .
F. P h o t o a d d i t i o n of a - a c e t o x y a c r y l o n i t r i l e t o
2 - p e n t e n o l i d e ( 7 )
1. Ambient T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.210 g ( 2 . 1 4 m m o l , 1 .0 e q )
2 - p e n t e n o l i d e , 1 .189 g ( 1 0 . 7 mmol, 5.0 e q )
a - a c e t o x y a c r y l o n i t r i l e and 0.075 g undecane i n 150 mL
a c e t o n i t r i l e was p l a c e d i n a Vycor t o r u s reactor and
i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t a m b i e n t t e m p e r a t u r e .
GLC a n a l y s i s o f a l i q u o t s r e v e a l e d t h a t t h e consumpt ion of
t h e l a c t o n e - 7 c e a s e d a f t e r 3 h r l e a v i n g - ca. 50% u n r e a c t e d .
A s w e l l a complex m i x t u r e o f p r o d u c t s dominated by two
p r o d u c t s , - 2 1 a n d 22, was p roduced i n t h e r a t i o of 44:56
which was c o n s t a n t t h r o u g h o u t t h e i r r a d i a t i o n . Extended
i r r a d i a t i o n i n c r e a s e d t h e c o m p l e x i t y o f t h e m i x t u r e . GLC
a n a l y s i s o f t h e i n i t i a l ( t i m e - 0 ) s a m p l e k e p t i n t h e d a r k
r e v e a l e d o n l y u n r e a c t e d s t a r t i n g materials .
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.369 g ( 3 . 7 6 m m o l , 1 .0 e q )
2 - p e n t e n o l i d e 1 .670 g (15 .0 mmol, 4.0 e q )
a - a c e t o x y a c r y l o n i t r i l e and 0.108 undecane i n 1 5 0 mL
a c e t o n i t r i l e was p l a c e d i n a Pyrex immers ion well, c o o l e d
t o - 3 0 0 ~ and i r r a d i a t e d t h r o u g h a Vycor f i l t e r . The
t e m p e r a t u r e o f t h i s s o l u t i o n s t a b i l i z e d a t -25% a f t e r 0 . 5
h r of i r r a d i a t i o n . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d t h a t
t h e consumpt ion o f t h e l a c t o n e Z ceased a f t e r 4 h r of
i r r a d i a t i o n l e a v i n g - ca. 20% u n r e a c t e d .
The i r r a d i a t i o n was stopped a f t e r 5.5 h r and GLC
a n a l y s i s showed a complex m i x t u r e o f p r o d u c t s domina ted by
two p r o d u c t s , - 21 and - 22 i n t h e r a t i o o f 46:54, which was
f o u n d t o be c o n s t a n t t h r o u g h o u t t h e i r r a d i a t i o n . The
u s u a l workup and s h o r t p a t h d i s t i l l a t i o n y i e l d e d a n o i l
c o n t a i n i n g m a i n l y - 2 1 and - 22 c o n t a m i n a t e d w i t h t h e s t a r t i n g
l a c t o n e . F l a s h chromatography on s i l i c a gel y i e l d e d 0.215
g ( 2 7 % ) of a v i s c o u s y e l l o w o i l which GLC a n a l y s i s r e v e a l e d
t o be compr i sed of o n l y - 2 1 and - 22 i n a r a t i o o f 42:58.
T h i s m i x t u r e e x h i b i t e d o n l y o n e s p o t o n TLC u s i n g a
v a r i e t y of e l u a n t s . The s l i g h t predominance of one i s o m e r
38.17(C7, t r ) , 2 6 . 2 0 ( ~ 5 , t r ) , 26.07(C6, d ) 20.47(CH3, q);
ms(C1, i s o b u t a n e ) : 211(12 , M+2), 210(100 , M + 1 ) , 1 5 0 ( 5 4 ) .
Anal . ( o f m i x t u r e ) C a l c d . f o r CloH11N04:C, 57.41;
H , 5.30; N , 6.70. Found: C , 57.25; H , 5.36; N , 6.62.
G. P h o t o a d d i t i o n of acrylonitr i le t o 2 - b u t e n o l i d e ( 8 )
1. Ambient T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.309 g ( 3 . 6 8 m m o l , 1.0 e q ) ,f 8
1 .56 g ( 2 9 . 4 m m o l , 8 .0 eq) a c r y l o n i t r i l e and 0.055 g
undecane i n 1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a v y c o r
t o r u s reactor and i r r a d i a t e d a t a m b i e n t t e m p e r a t u r e . GLC
a n a l y s i s showed t h a t t h e l a c t o n e was consumed a f t e r 6.5
h r . A complex m i x t u r e of p r o d u c t s dominated by f o u r
p r o d u c t s 23, 24, - 25, - 26 i n t h e r a t i o o f 23:22:38:17 was
formed. The r a t i o o f t h e s e p r o d u c t s was c o n s t a n t
t h r o u g h o u t t h e i r r a d i a t i o n . GLC a n a l y s i s of t h e i n i t i a l
( t i m e l o ) s a m p l e k e p t i n t h e d a r k showed o n l y u n r e a c t e d
s t a r t i n g materials by GLC. The u s u a l workup and s h o r t p a t h
d i s t i l l a t i o n y i e l d e d 0.232 g of a v i s c o u s o i l which
e x h i b i t e d two s p o t s on TLC. F l a s h chromatography on
S i l i c a G e l u s i n g 1:l EtOAc/Hexane s e p a r a t e d t h e m i x t u r e
i n t o two f r a c t i o n s , e a c h o f which c r y s t a l l i z e d o n s t a n d i n g
and were r e c r y s t a l l i z e d f rom EtOH. F r a c t i o n 1, 0.098
g ( 1 9 % ) , mop. 79-92% was a 68:32 m i x t u r e o f - 23 and - 24.
F r a c t i o n 2, 0 .103 g ( 1 0 % ) , m.p. 80-84OC was a 55:45 m i x t u r e
of - 25 and - 26 by GLC analysis. Single crystals of each
mixture were grown from an EtOAc/Hexane solution and
analysed by X-Ray crystallography39. GLC analysis of the
crystals subsequently identified 23 as
cis-exo-7-cyano-3-oxabicyclo [3.2.0]heptan-2-one and 25 as -- - cis-endo-7-cyano-3- oxabicyclo [3.2.0lheptan-2-one. --
Ir(KBr pellet) of mixture of 23 and 24: 2240(w),
1760(~), 1470(~), 1440(w), 1380(m), 1260(m), 1180(s),
1120(w), lO6O(m), 98O(m), 96O(w), 800(w) cm-l.
Anal. (of mixture) Calcd. for C7H7N02: C, 61.31; H,
5.14; N, 10.22. Found: C, 61.21; H,5.31; N,10.07.
Ir(KBr pellet 1 of mixture of - 25 and - 26: 2240(w)
Anal. ( o f m i x t u r e ) C a l c d . f o r C7H7N02: C, 61.31; H ,
5.14; N , 10 .22 . Found: C , 61.35; H I 5.35; N , 10.06.
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.318 g ( 3 . 7 8 mmol, 1 . 0 e q ) - 8 , 1 .611 g
(30 .4 mmol, 8 .0 e q ) a c r y l o n i t r i l e and 0,075 g undecane
i n 150 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex immersion
well, c o o l e d t o -30% and i r r a d i a t e d t h r o u g h a Vycor
f i l t e r . The t e m p e r a t u r e s t a b i l i z i e d a t -20•‹c a f t e r
0.5 h r of i r r a d i a t i o n . GLC a n a l y s i s of a l i q u o t s r e v e a l e d
t h a t t h e l a c t o n e - 8 was consumed i n 1 . 5 h r and t h a t a
complex m i x t u r e o f p r o d u c t s domina ted by t h e same f o u r
p r o d u c t s (24-26) -- o b s e r v e d a b o v e was formed, The r a t i o o f
t h e f o u r p r o d u c t s was 23:19:42:15 and t h i s r a t i o was
c o n s t a n t t h r o u g h o u t t h e i r r a d i a t i o n . The u s u a l workup
and s h o r t p a t h d i s t i l l a t i o n g a v e a c r u d e y e l l o w o i l which
was p r e d o m i n a n t l y composed o f t h e f o u r p h o t o a d d u c t s .
F l a s h ch romatography o n s i l i c a g e l as b e f o r e s e p a r a t e d
t h e f o u r p r o d u c t s f rom t h e h o s t o f b y p r o d u c t s t o g i v e ,
a f t e r s h o r t p a t h d i s t i l l a t i o n , a v i s c o u s y e l l o w o i l which
weighed 0.206 g ( 4 0 % ) .
3. S o l v e n t S t u d i e s - I r r a d i a t i o n o f 8 and
A c r y l o n i t r i l e i n E t h e r a t Ambient Tempera ture
A s o l u t i o n of 0.237 g ( 2 . 8 2 mmol, 1 .0 e q ) - 8, 1.199 g
(22 .6 mmol, 8.0 eq) a c r y l o n i t r i l e and 0.074 g undecane i n
1 5 0 mL anhyd. e t h e r was p l a c e d i n a Vycor t o r u s r e a c t o r
and i r r a d i a t e d a t a m b i e n t t e m p e r a t u r e . GLC a n a l y s i s o f
a l i q u o t s r e v e a l e d t h a t t h e l a c t o n e 2 was consumed a f t e r
3.5 h r o f i r r a d i a t i o n and t h a t a complex m i x t u r e of
p r o d u c t s was formed. Mixed sample GLC e x p e r i m e n t s showed
t h a t compounds - 2 3 and - 25 were p r e s e n t as minor components
o f t h e m i x t u r e and t h a t compounds 24 and 26 were a b s e n t .
GLC a n a l y s i s of t h e i n i t i a l ( t i m e = O ) sample k e p t i n t h e
d a r k r e v e a l e d o n l y u n r e a c t i n g s t a r t i n g materials.
4 . S o l v e n t S t u d i e s - I r r a d i a t i o n o f 8 and
A c r y l o n i t r i l e i n E t h e r a t Low Tempera ture
A s o l u t i o n o f 0.221 g ( 2 . 6 3 mmol, 1 . 0 e q ) - 8, 1 .113 g
( 2 1 . 1 mmol, 8.0 e q ) a c r y l o n i t r i l e and 0.063 g undecane i n
1 5 0 mL anhyd. e t h e r was p l a c e d i n a Pyrex immersion w e l l ,
c o o l e d t o -30% and i r r a d i a t e d t h r o u g h a Vycor f i l t e r .
GLC a n a l y s i s of a l i q u o t s r e v e a l e d t h a t t h e l a c t o n e - 8 was
consumed w i t h i n 3 h r and a complex m i x t u r e was formed.
Mixed sample GLC r e v e a l e d t h a t - 2 3 and 2 were p r e s e n t as
minor components o f t h e m i x t u r e and t h a t 24 and - 2 6 were
p r e s e n t as t r a c e components .
5. At tempted Base I s o m e r i z a t i o n o f 2 3 and 24 w i t h N a O E t
To a s o l u t i o n o f 0.12 g of t h e ch romatography
f r a c t i o n 1, o b t a i n e d i n t h e f i r s t e x p e r i m e n t i n t h i s
ser ies , S e c t i o n G 1 above , c o n t a i n i n g compounds - 23 and - 24
i n t h e r a t i o o f 68:32 and 0.009g u n d e c a n e i n 1 0 mL anhyd.
e t h a n o l was added 1 . 5 mL 1.2 M NaOEt. The r e s u l t i n g
s o l u t i o n s t i r r e d a t ambien t t e m p e r a t u r e f o r 1 h r . The
u s u a l workup and GLC a n a l y s i s r e v e a l e d t h e d i s a p p e a r a n c e
of 23 and 24 and t h e f o r m a t i o n o f a h o s t o f h i g h e r b o i l i n g
compounds. A sample of t h e c h r o m a t o g r a p h y f r a c t i o n 2 was
t r e a t e d i n a s imi lar manner and a l s o r e s u l t e d i n loss of
t h e sample as well as f o r m a t i o n of a h o s t of h i g h e r
b o i l i n g compounds.
6. At tempted Base I s o m e r i z a t i o n o f 2 3 and 24 w i t h KOtBu
To a s o l u t i o n o f 0.015 g of t h e ch romatography
f r a c t i o n 1, c o n t a i n i n g compounds - 23 and - 24 i n t h e r a t i o o f
68:32, 0.020 g undecane and 0.15 mL HMPA i n 1 0 mL d r y
t -Bu tano l was added 0.106 g p o t a s s i u m t - b u t o x i d e and t h i s
m i x t u r e s t i r r e d a t room t e m p e r a t u r e f o r 2 h r . The u s u a l
workup and GLC a n a l y s i s r e v e a l e d no change or
d e c o m p o s i t i o n o f f r a c t i o n 1. T h i s p r o c e d u r e was r e p e a t e d
w i t h a sample o f t h e chromatography f r a c t i o n 2 w i t h
i d e n t i c a l r e s u l t s .
7. Attempted Alumina I s o m e r i z a t i o n o f 23 and 24
A 0.10 g sample of t h e ch romatography f r a c t i o n 1 was
e l u t e d t h r o u g h a 2.0 g column o f n e u t r a l Alumina w i t h
30 mL CHC13 as b e f o r e and r e c o v e r e d unchanged. A sample
o f t h e ch romatography f r a c t i o n 2 was t r e a t e d i n a n
i d e n t i c a l manner and s i m i l a r l y r e c o v e r e d unchanged. The
1~ nmr s p e c t r a o f t h e m i x t u r e s was i d e n t i c a l t o spectra
o b t a i n e d b e f o r e t r e a t m e n t .
H. P h o t o a d d i t i o n of a - c h l o r o a c r y l o n i t r i l e t o
2 - b u t e n o l i d e ( 8 )
1. Ambient Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.465 g ( 5 . 5 5 mmol, 1 . 0 eq)
2 - b u t e n o l i d e , 4.94 g (56 .5 mmol, 1 0 e q )
a - c h l o r o a c r y l o n i t r i l e and 0.105 g undecane i n 200 mL .
a c e t o n i t r i l e was p l a c e d i n a Pyrex immersion well and
i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t ambien t t e m p e r a t u r e .
GLC a n a l y s i s o f a l i q u o t s r e v e a l e d t h a t t h e consumpt ion o f
t h e l a c t o n e - 8 c e a s e d a f t e r 2 h r o f i r r a d i a t i o n l e a v i n g H. 80% u n r e a c t e d . T h i s was accompanied by f o r m a t i o n o f a
complex m i x t u r e o f p r o d u c t s . Extended i r r a d i a t i o n
i n c r e a s e d t h e c o m p l e x i t y o f t h e m i x t u r e b u t d i d n o t r e s u l t
i n f u r t h e r consumpt ion of t h e l a c t o n e . GLC a n a l y s i s o f
t h e i n i t i a l ( t i m e = O ) sample kept i n t h e d a r k r e v e a l e d o n l y
u n r e a c t e d s t a r t i n g m a t e r i a l s . A f t e r 8 h r of i r r a d i a t i o n
the usual workup followed by shortpath distillation, bulb
temperature 105-1200/25 torr, yielded 0.302 g( 65%) of
2-butenolide which was 93% pure by GLC.
2. Low Temperature Photolysis
A solution of 0.535 g(6.35 mmol, 1.0 eq)
2-butenolide, 4.42 g(50.5 mmol, 8.0 eq)
a-chloroacrylonitrile and 0.092 g undecane in 200 mL
acetonitrile was placed in a Pyrex immersion well, cooled
to -400C and irradiated through a Vycor filter. The
temperature of the solution stabilized at -25% after 1
hr. GLC analysis of aliquots revealed the consumption of
the lactone - 8 ceased after 3 hr of irradiation leaving ca. - 70% unreacted accompanied by formation of a complex
mixture of products. After 4 hr of irradiation the usual
workup followed by shortpath distillation, bulb
temperature 105-1150C/24 torr, gave 0.284 g(53%) of
2-butenolide, which was 94% pure by GLC.
I. Photoaddition of a-acetoxyacrylonitrile to
2-butenolide ( 8)
1. Ambient Temperature Photolysis
A solution of 0.550 g(6.54 mmol, 1.0 eq)
2-butenolide, 3.61 g(22.5 mmol, 5.0 eq)
a-acetoxyacrylonitrile and 0.112 g undecane in 150 mL
a c e t o n i t r i l e was p l a c e d i n a Vycor t o r u s r e a c t o r and
i r r a d i a t e d a t a m b i e n t t e m p e r a t u r e . GLC a n a l y s i s r e v e a l e d
t h a t consumpt ion of t h e l a c t o n e - 8 c e a s e d a f t e r 3 h r ,
l e a v i n g - ca. 70% u n r e a c t e d accompanied by f o r m a t i o n of a
complex m i x t u r e o f p r o d u c t s . Ex tended i r r a d i a t i o n
i n c r e a s e d t h e c o m p l e x i t y o f t h e m i x t u r e . The u s u a l workup
and s h o r t p a t h d i s t i l l a t i o n a f t e r 6 h r o f i r r a d i a t i o n gave
0.247 g ( 4 5 % ) o f l a c t o n e which was 93% p u r e by GLC.
GLC a n a l y s i s o f t h e i n i t i a l ( t i m e = O ) s ample k e p t i n t h e
d a r k r e v e a l e d o n l y u n r e a c t e d s t a r t i n g materials.
2. Low TemDerature P h o t o l v s i s
A s o l u t i o n of 0.445 g ( 5 . 3 1 m m o l , 1 . 0 e q )
2 - b u t e n o l i d e , 2.95 g ( 2 6 . 5 mmol, 5.0 e q )
a - a c e t o x y a c r y l o n i t r i l e and 0.097 g undecane i n 20 mL
a c e t o n i t r i l e was p l a c e d i n a P y r e x immers ion well, c o o l e d
t o -30•‹C and i r r a d i a t e d t h r o u g h a Vycor f i l t e r . The
t e m p e r a t u r e o f t h e s o l u t i o n s t a b i l i z e d a t -200C a f t e r one
h o u r of i r r a d i a t i o n . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d
t h a t t h e consumpt ion o f t h e l a c t o n e - 8 c e a s e d a f t e r 2.5 h r
l e a v i n g - c a . 70% u n r e a c t e d . T h i s was accompanied by
f o r m a t i o n o f a complex m i x t u r e o f p r o d u c t s . A f t e r f o u r
h o u r s of i r r a d i a t i o n t h e u s u a l workup and s h o r t p a t h
d i s t i l l a t i o n gave 0.227 g ( 5 1 % ) o f l a c t o n e - 8 which was 94%
p u r e by GLC.
J. P h o t o a d d i t i o n of A c r y l o n i t r i l e t o
3,4,4-trimethyl-2-buten-1,4-olide ( 9 )
1. Ambient Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.112 g ( . 8 8 7 mmol, 1 .0 e q ) 9, 0.387 g
(7 .18 mrnol, 8.0 e q ) a c r y l o n i t r i l e and 0.038 g undecane i n
1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a Vycor t o r u s r e a c t o r
and i r r a d i a t e d a t ambien t t e m p e r a t u r e . GLC a n a l y s i s o f
a l i q u o t s r e v e a l e d t h a t t h e l a c t o n e was consumed a f t e r
1 . 5 h r o f i r r a d i a t i o n and t h a t a complex m i x t u r e dominated
by f o u r p r o d u c t s 27, - 28, - 29 and - 30, i n t h e r a t i o o f
27: 26: 32: 1 5 , was formed. T h i s r a t i o was c o n s t a n t
t h r o u g h o u t t h e i r r a d i a t i o n . A f t e r 2 h r o f i r r a d i a t i o n t h e
u s u a l workup and s h o r t p a t h d i s t i l l a t i o n gave 0.124 g ( 7 8 % )
o f a v i s c o u s y e l l o w o i l which GLC a n a l y s i s r e v e a l e d t o b e
a 92% p u r e m i x t u r e of t h e f o u r p r o d u c t s -- 27-30.
2. Low Tempera tu re P h o t o l y s i s
A s o l u t i o n of 1 .85 g(1 .47 mmol, 1 . 0 e q ) 9, 0.630 g
(11.9 mmol, 8 . 1 e q ) a c r y l o n i t r i l e and 0.063 g undecane i n
1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex immers ion w e l l ,
c o o l e d t o - 3 0 0 ~ and i r r a d i a t e d t h r o u g h a Vycor f i l t e r .
The t e m p e r a t u r e o f t h e s o l u t i o n s t a b i l i z e d a t -20% a f t e r
0 .5 h r of i r r a d i a t i o n . GLC a n a l y s i s of a l i q u o t s r e v e a l e d
t h a t t h e l a c t o n e was consumed a f t e r 2 h r of i r r a d i a t i o n
and a complex m i x t u r e domina ted by -- 27-30 was formed.
The r a t i o of t h e f o u r p r o d u c t s was found t o be 19:39:27:20
and t h i s r a t i o was found t o b e c o n s t a n t t h r o u g h o u t t h e
i r r a d i a t i o n . After 2.5 h r of i r r a d i a t i o n t h e u s u a l workup
and s h o r t p a t h d i s t i l l a t i o n g a v e 0.232 g ( 8 1 % ) of a v i s c o u s
y e l l o w o i l which GLC a n a l y s i s r e v e a l e d t o be a 92% p u r e
m i x t u r e o f -- 27-30 i n t h e r a t i o o f 19:35:25:20. T h i s
material e x h i b i t e d two s p o t s on TLC u s i n g EtOAc/toluene
1:l and r e p e a t e d f l a s h ch romatography o n s i l i c a g e l
s e p a r a t e d o n l y 0.029 g ( 1 0 % ) of - 30 f rom t h e m i x t u r e . T h i s
material was i s o l a t e d as a n o i l which c r y s t a l l i z e d o n
s t a n d i n g , mop. 97-100•‹C and was 97% p u r e by GLC. The
t h r e e o t h e r components g a v e a s i n g l e spot by TLC b u t
s e v e r a l c h r o m a t o g r a p h i c f r a c t i o n s c o n t a i n e d d i f f e r e n t
relative amounts of each product present , making
a s s i g n m e n t o f t h e s i g n a l s i n t h e 1% nmr s p e c t r a
p o s s i b l e . The s i g n a l s i n t h e 1~ nmr s p e c t r a of t h e
m i x t u r e were n o t amenable t o a n a l y s i s d u e t o o v e r l a p p i n g
s i g n a l s .
24.2(CH3), 1 9 . 8 ( C ~ ~ ) , 14.4(CH3); rns(~1, i s o b u t a n e ) :
1 8 0 ( 1 0 0 , M+l) , 9 5 ( 7 ) .
Anal . o f m i x t u r e . Ca lcd . f o r CloH18NO: C, 67.02;
3. A t t empted Alumina I s o m e r i z a t i o n o f 27-30
A 0.012 g s a m p l e of t h e d i s t i l l e d m i x t u r e c o n t a i n i n g
27-30 i n t h e r a t i o o f 19:35:26:20 by GLC was e l u t e d -- t h r o u g h a 2 g co lumn o f n e u t r a l Alumina as b e f o r e .
Removal o f t h e s o l v e n t l e f t 0.011 g of material which
GLC a n a l y s i s r e v e a l e d t o be -- 27-30 i n t h e same r a t i o as
b e f o r e t r e a t m e n t . A 0.006 g sample of 2 was t r e a t e d
i n t h e same manner and r e c o v e r e d unchanged a s w e l l .
4. At t empted ~ h o t o i s o m e r i z a t i o n 27-30
A s o l u t i o n of 0.017 g of a c h r o m a t o g r a p h i c f r a c t i o n
c o n t a i n i n g -- 27-30 i n t h e r a t i o of 21:25:40:14 by GLC and
0.009 g undecane i n 1 0 mL a c e t o n i t r i l e was p l a c e d i n a
q u a r t z t es t t u b e , t a p e d t o t h e s i d e o f t h e lamp j a c k e t and
i r r a d i a t e d t h r o u g h a Vycor f i l t e r a t ambien t t e m p e r a t u r e
f o r 2 h r . GLC a n a l y s i s o f t h e s o l u t i o n a f t e r i r r a d i a t i o n
r e v e a l e d n o change i n t h e r e l a t i v e amounts of t h e f o u r
p r o d u c t s .
K. P h o t o a d d i t i o n of a - c h l o r o a c r y l o n i t r i l e t o
1. Ambient Tempera tu re P h o t o l y s i s
A s o l u t i o n o f 0.122 g ( . 9 6 7 m m o l , 1 . 0 e q ) 2, 0.630 g
(7 .2 mmol, 7.4 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.051 g
undecane i n 1 5 0 mL a c e t o n i t r i l e was p l a c e d i n a Vycor
t o r u s r e a c t o r and i r r a d i a t e d a t a m b i e n t t e m p e r a t u r e . GLC
a n a l y s i s o f a l i q u o t s r e v e a l e d t h e consumpt ion of t h e
l a c t o n e - 9 c e a s e d a f t e r two h r l e a v i n g G. 90% u n r e a c t e d .
T h i s was accompanied by f o r m a t i o n o f a complex m i x t u r e of
h i g h e r b o i l i n g p r o d u c t s . Extended i r r a d i a t i o n d i d n o t
r e s u l t i n f u r t h e r consumpt ion of t h e s t a r t i n g l a c t o n e ,
o n l y an i n c r e a s e i n t h e c o m p l e x i t y o f t h e m i x t u r e . GLC
a n a l y s i s of t h e i n i t i a l ( t i m e = O ) s a m p l e k e p t i n t h e d a r k
c o n t a i n e d o n l y u n r e a c t e d s t a r t i n g m a t e r i a l s . The u s u a l
work up and s h o r t p a t h d i s t i l l a t i o n , b u l b t e m p e r a t u r e
9 0 - 1 0 5 0 ~ / 1 0 t o r r , g a v e 0.098 g ( 7 8 % ) o f 9 which was 97%
p u r e by GLC.
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.116 g(0 .919 mmol, 1 . 0 e q ) 2, 0.483 g
(5 .52 mmol, 5 .0 e q ) a - c h l o r o a c r y l o n i t r i l e and 0.075 g
undecane i n 200 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immers ion well, c o o l e d t o -30% and i r r a d i a t e d t h r o u g h a
Vycor f i l t e r . The t e m p e r a t u r e of t h e s o l u t i o n s t a b i l i z e d
a t -20% a f t e r 0 .5 h r i r r a d i a t i o n . GLC a n a l y s i s o f
a l i q u o t s r e v e a l e d t h a t t h e consumpt ion o f t h e l a c t o n e - 9
c e a s e d a f t e r 2 .5 h r o f i r r a d i a t i o n l e a v i n g - ca. 85%
u n r e a c t e d accompanied by t h e f o r m a t i o n o f a complex
m i x t u r e o f h i g h e r b o i l i n g p r o d u c t s . A f t e r 3 h r o f
i r r a d i a t i o n t h e u s u a l workup and s h o r t p a t h d i s t i l l a t i o n
gave 0.083 g ( 7 2 % ) o f - 9 which was 96% p u r e by GLC.
L. Photoaddition of a-acetoxyacrylonitrile to 9
1. Ambient T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.098 g ( . 7 8 mmol, 1 .0 e q ) 2, 0.431 g
(3 .88 mmol, 5 .0 e q ) a - a c e t o x y a c r y l o n i t r i l e and 0.062 g
undecane i n 200 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immersion w e l l and i r r a d i a t e d th rough a Vycor f i l t e r a t
a m b i e n t t e m p e r a t u r e . GLC a n a l y s i s o f a l i q u o t s r e v e a l e d
consumpt ion of l a c t o n e 9 c e a s e d a f t e r 1 . 5 h r l e a v i n g ca. - - 90% u n r e a c t e d . T h i s was accompanied by f o r m a t i o n of
complex m i x t u r e o f h i g h e r b o i l i n g p r o d u c t s . GLC a n a l y s i s
o f t h e i n i t i a l ( t i m e = O ) s ample k e p t i n t h e d a r k showed
o n l y u n r e a c t e d s t a r t i n g materials. The u s u a l workup and
s h o r t p a t h d i s t i l l a t i o n g a v e 0.077 g ( 7 9 % ) 9 which was 94%
p u r e by GLC.
2. Low T e m p e r a t u r e P h o t o l y s i s
A s o l u t i o n o f 0.093 g ( . 7 4 mmol, 1 . 0 eq) 9, 0.383 g - (3 .54 mmol, 4.8 eq) a - a c e t o x y a c r y l o n i t r i l e and 0.061 g
undecane i n 200 mL a c e t o n i t r i l e was p l a c e d i n a Pyrex
immersion well, c o o l e d t o -30•‹c a n d i r r a d i a t e d t h r o u g h a
Vycor f i l t e r . The t e m p e r a t u r e o f t h e s o l u t i o n s t a b i l i z e d
a t -200C a f t e r 0 .5 h r i r r a d i a t i o n . GLC a n a l y s i s o f
a l i q u o t s r e v e a l e d c o n s u m p t i o n o f l a c t o n e 9 ceased a f t e r
2.0 h r o f i r r a d i a t i o n l e a v i n g ca. 80% u n r e a c t e d . T h i s was - accompanied by t h e f o r m a t i o n o f a complex m i x t u r e of
p r o d u c t s . A f t e r 3 h r of i r r a d i a t i o n t h e u s u a l workup and
s h o r t p a t h d i s t i l l a t i o n g a v e by 0 .63 g ( 6 8 % ) - 9 which was 94%
p u r e by GLC.
S e n s i t i z e r Experiments
n. I r r a d i a t i o n of A c r y l o n i t r i l e and its a-chloro
and a-acetoxy d e r i v a t i v e s i n Acetone
1. A so lu t i on of 1 .116 g(21.0 mmol) a c r y l o n i t r i l e i n
150 mL spec. grade acetone was placed i n a Vycor to rus
r eac to r and i r r a d i a t e d through a Corex f i l t e r a t ambient
temperature.
The s o l u t i o n turned yellow wi th in 0.5 hr . GLC
ana ly s i s of a l i q u o t s withdrawn a t regular i n t e r v a l s
revealed t h e formation of a complex mixture of low bo i l ing
products . GLC ana ly s i s of t he i n i t i a l (time=O) sample
kept i n t he dark d i d not show any of these products.
2. A so lu t i on of 1.005 g(11.5 mmol)
a -ch lo roacry lon i t r i l e i n 150 mL spec. grade acetone was
placed i n a Vycor t o r u s r eac to r and i r r a d i a t e d through a
Corex f i l t e r a t ambient temperature. The s o l u t i o n began
d i sco lour ing wi th in 15 min. and GLC ana lys i s revealed c
formation of a complex mixture of low bo i l ing products.
GLC ana ly s i s of t h e i n i t i a l (time=O) sample kept i n the
dark d i d not contain any of these products.
3. A so lu t i on of 1.156 g(10.4 mmol)
a-acetoxyacryloni t r i le and 0.104 g decane i n 150 mL spec.
grade acetone was placed i n a Vycor t o ru s reac tor and
i r r a d i a t e d through a Corex f i l t e r a t ambient temperature.
T h i s s o l u t i o n began d i sco lour ing immediately on
i r r a d i a t i o n and GLC ana ly s i s revealed a decrease i n the
r e l a t i v e amount of a -ace toxyacry lon i t r i l e accompanied
by formation of a complex mixture of products. A l l
t h e o l e f i n was consumed wi th in 2 h r of i n i t i a t i o n of
i r r a d i a t i o n . GLC ana ly s i s of t he i n i t i a l (time=O)
sample kept i n t he dark showed only unreacted s t a r t i n g
mate r ia l s .
I r r a d i a t i o n of Ac ry lon i t r i l e , a - ch lo roac ry lon i t r i l e
and a -ace toxyacry lon i t r i l e i n t h e presence of - Acetophenone
1. A so lu t i on of 1.060 g(8.86 mmol, 1 . 0 eq )
acetophenone, 2.350 g(44.3 mmol, 5.0 eq) a c r y l o n i t r i l e and
0.101 g undecane i n 150 mL a c e t o n i t r i l e was placed i n a
Vycor t o ru s reac to r and i r r a d i a t e d through a Corex f i l t e r
a t ambient temperature. T h i s s o l u t i o n began d i sco lour ing
immediately and GLC ana ly s i s of a l i q u o t s withdrawn a t
regular i n t e r v a l s revealed a decrease i n t he amount of
acetophenone accompanied by formation of a complex mixture
of products. The consumption of t h e acetophenone ceased
a f t e r 2.5 hr of i r r a d i a t i o n leaving - ca. 40% unreacted.
GLC ana lys i s of the i n i t i a l (time=O) sample kept i n t he
dark showed only unreacted s t a r t i n g mate r ia l s .
2. A so lu t ion of 1 . 2 1 2 g (10 .1 mmol, 1 . 0 eq)
acetophenone, 4 . 4 1 g (50.4 mmol, 5.0 eq)
a-chloroacryloni t r i le and 0.098 g undecane i n 150 mL
a c e t o n i t r i l e was placed i n a Vycor torus reactor and
i r radiated through a Corex f i l t e r a t ambient temperature.
The solution began discolouring immediately on i r rad ia t ion
and GLC analysis of a l iquots showed a decrease i n the
amount of acetophenone accompanied by formation of a
complex mixture of products. The consumption of the
acetophenone ceased a f t e r 2 hr of i r r ad ia t ion leaving ca. - 50% unreacted. GLC analysis of the i n i t i a l (time-0)
sample kept i n the dark showed only unreacted s t a r t i n g
materials .
3 . A so lu t ion of 1.175 g(9.78 mmol, 1.0 eq)
acetophenone, 5.32 g(47.9 mmol, 4.9 eq)
a-acetoxyacrylonitr i le and 0.097 g undecane i n 150 mL
a c e t o n i t r i l e was placed i n a Vycor torus reactor and
i r radiated through a Corex f i l t e r a t ambient temperature.
The solution began discolouring immediately on i r r ad ia t ion
and GLC analysis of a l iquots revealed a decrease i n both
the amounts of acetophenone and a-acetoxyacrylonitrile
accompanied by formation of a complex mixture of
products. The decrease i n the r e l a t ive amounts of
a-acetoxyacrylonitr i le and acetophenone ceased a f t e r
1.5 hr of i r r ad ia t ion leaving ca. 60% and 40% unreacted -
and a-acetoxyacrylonitrile in the presence of
Hexamethylbenzene
1. A solution of 1.135 g(6.9 mmol, 1.0 eq)
hexamethylbenzene, 1.891 g(35.7 mmol, 5.1 eq)
acrylonitrile and 0.078 g undecane in 150 mL acetonitrile
was placed in a Vycor torus reactor and irradiated through
a Corex filter at ambient temperature. The solution began
discolouring immediately on irradiation and GLC analysis
of aliquots revealed a decrease in the amount of
hexamethylbenzene accompanied by formation of complex
mixture of products. The consumption of the
hexamethylbenzene ceased after 1.5 hr of irradiation
leaving - ca. 60% unreacted. GLC analysis of the initial . (time=O) sample kept in the dark revealed only unreacted
starting materials.
2. A solution of 1.032 g(6.36 mmol, 1.0 eq)
hexamethylbenzene, 2.783 g(31.8 mmol, 5.0 eq)
a-Chlor~acrylonitrile and 0.082 g undecane in 150 mL
acetonitrile was placed in a Vycor torus reactor and
irradiated through a Corex filter at ambient temperature. .
The solution began I discolouring immediately on irradiation
and GLC analysis revealed a decrease in the amount of
hexamethylbenzene and the formation of a complex mixture
of products. The consumption of the hexamethylbenzene
ceased after 2 hr of irradiation leaving - ca. 70%
unreacted. GLC analysis of the initial (time=O) sample
kept in the dark contained only unreacted starting
materials.
3. A solution of 1.020g(6.06 mmol, 1.0 eq)
hexamethylbenzene, 3.301 g(29.7 mmol, 4.9 eq)
a-acetoxyacrylonitrile and 0.076 g undecane in 150 mL
acetonitrile was placed in a Vycor torus reactor and
irradiated through a Corex filter at ambient temperature.
The solution began discolouring immediately on irradiation
and GLC analysis of aliquots revealed a decrease in both
the amounts of a-acetoxyacrylonitrile and
hexamethylbenzene as well as formation of a complex
mixture of products. The consumption of the c
a-acetoxyacrylonitrile and hexamethylbenzene ceased after
2 hr of irradiation leaving - ca. 70% and 50% respectivelY
of these components unreacted. GLC analysis of the
initial (time=O) sample kept in the dark revealed only
unreacted starting materials.
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