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TRANSCRIPT
Prof. Simon AldridgeOxford UniversityPostdoc
w. Thomas Fehlner (U Notre Dame)
w. Michael Mingos (Imperial Col. London)
Ph.D. in 1996
w. Anthony Downs@Oxford U
Graduated Oxford U
TOC
C–C
Al
C–C
Abstract: The activation of C–C bonds is of fundamental interest in the
construction of complex molecules from petrochemical feedstocks. In the case
of the archetypal aromatic hydrocarbon benzene, C–C cleavage is
thermodynamically disfavored, and is brought about only by transient highly
reactive species generated in situ. Here we show that the oxidative addition of
the C–C bond in benzene by an isolated metal complex is not only possible,
but occurs at room temperature and reversibly at a single aluminium center in
[(NON)Al]− (where NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-
dimethylxanthene). Selectivity over C–H bond activation is achieved kinetically
and allows for the generation of functionalized acyclic products from benzene.
Abstract
C–C
Al C–C
C–H C–C
6
Hicks, J.; Vasko, P.; Goicoechea, J. M.; Aldridge, S.
Reversible, Room-Temperature C–C Bond Activation of Benzene by an Isolable Metal Complex.J. Am. Chem. Soc. 2019, 141, 11000-11003.
Prof. Jose GoicoecheaOxford UniversityPostdoc
w. Slavi C. Sevov (U Notre Dame)
Ph.D. in 2003
w. Michael K. Whittlesey@U of Bath
Graduated U de Zaragoza
Introduction: C-H(1) abstract(2) (review)
Ref 1Ref 2Ref 3 aromatic
Ref 4 1-3
Ref 5:
Ref 6: πRef 7:
Ref 8
Cp2WC-H
Ref 9: C-H
Introduction 2: C-CRef 10 Ref 14
Ref 11: Ref 10 (Nature )Ref 12
C-C
W
PMe3
Me3P
Me3P
PMe3
NC
CN
W
PMe3
CH2
PMe2Me3P
Me3P
PMe3
HN
N
QoxH
Ref 13
C-C
Si(II) C-C
Ref 15
P(I) C-C
Ref 16
Ru p-cymene C-C
Introduction 3: C-CRef 17
Cp′
Cp′
Cp′Ti
Ti
Ti
HH
HH
HH
H
1
40 °C, 36 h–H2
H
H
H
H H
H
2, quantitative
Ti TiTi
H H
H
H
CH3
H
H
H
H
Cp′
Cp′
Cp′
Ti(III)2Ti(IV) C-C
Ref 18
Pd(II)C-C
Ref 19
Ir(I) C-C
Ref 20
C-C( )
R
NjCH COjAlkI Aik DA)
2
Ref 21a
C-C (Rh(II) )
Ref 21b
C-C ( )
Ref 22
Si(II)C-C
Ref 23
Si(II)C-C= Buchner ring expansion
Introduction 4: Al
(i) K[N(SiMe3)2](ii) AlI3
KC8 (excess)
(NON)H2 [Al(NON)]2
[K{Al(NON)}]2
KC8 (1 equiv.)
(NON)AlI
O
tBu
tBu
NH
Dipp
NH
Dipp
O
tBu
tBu
N
Dipp
N
Dipp
Al I
O
tBu
tBu
N
Dipp
N
Dipp
Al O
tBu
tBu
N
Dipp
N
Dipp
Al
O
tBu
tBu
N
Dipp
N
Dipp
Al O
tBu
tBu
N
Dipp
N
Dipp
Al
K
K
Ref 24
(NON)AlMe
[K{Al(NON)}] 2
MeOTf or MeI
(NON)AlH
(Nacnac)MesMgAl(NON)
(NON)Al Al(NON)
(NON)AlI
HX / –KX
[K{H2Al(NON)}]2 (R = H)
H2 or C6H6
[K{Ph(H)Al(NON)}]2 (R = Ph)
(Nacnac)MesMgI(OEt2)
–KOTf or KI
O
tBu
tBu
N
Dipp
N
Dipp
Al H
O
tBu
tBu
N
Dipp
N
Dipp
Al O
tBu
tBu
N
Dipp
N
Dipp
Al
K
K
O
tBu
tBu
N
Dipp
N
Dipp
Al Me
O
tBu
tBu
N
Dipp
N
Dipp
Al MgH H
R
R
N
N
Mes
Mes
[e.g. (NON)H2
–K2(NON)]
Al
Ref 25
O
tBu
tBu
N
N
Dipp
Dipp
Al O
tBu
tBu
N
N
Dipp
Al
Dipp
K
K
O
tBu
tBu
N
N
Dipp
Dipp
Al Au PtBu3
1 3
tBu3PAuI– KI
� �
O
tBu
tBu
N
N
Dipp
Dipp
AlE
E
iPrNCNiPror CO2
Au PtBu3
E = iPrN, 4E = O, 5
� �
Al CO2
AlAl-I
Al–Al
SN2
C–H, H–H
This Work 1: Al
Al–N 2.022(1) Å2.049(1) Å
Al–O 2.175(1) Å
Scheme 1. Sequestration of the Potassium Cations fromDimeric 1 To Generate Monomeric Aluminyl Compound[K(2.2.2-crypt)][(NON)Al], 2
Scheme 2. Room Temperature CC Bond Activation ofBenzene by 2 To Give Metallacycle 3; Facile Exchange ofthe C6H6 Fragment of 3 in the Presence of C6D6
Al–N 1.963(2) Å1.956(2) Å
Al–O 2.279(2) Å
Cf. 1 60 ℃, 96Al(H)(Ph)
dH 7.21, 7.00, 5.97 ppm Crystal structure of 3
Crystal structure of 2
Al–C 1.980(2) ÅC–C 1.343(2) Å
1.442(3) Å1.352(3) Å1.451(3) Å1.352(3) Å
Al
Temperature(°C) Rateconstant(k)
60 2.31x10–5
65 4.53x10–5
70 8.73x10–5
75 1.639x10–4
80 2.759x10–4
Al···Al Al···K(>7 Å)
3 C6D6 3Al1H NMR
Scheme 3. Reactions of 2 and 3 with Naphthalene at 80 °CTo Give a Mixture of CH Activation Products Resultingfrom Attack at the 1 and 2 Positions29
2 34a,4b →3
This Work 2:
Figure 2. DFT-calculated (DFT-D3, PBE0, Def-TZVP) pathways for benzene CC and CH bond activation by 2′. For computationalefficiency the backbone tBu groups of the NON ligand were replaced by methyl groups in all calculations. The “cut-down” versions of compounds2, 3 and 5 so modeled are labeled 2′, 3′ and 5′.
tBu Me
C–C 3’C–H 5’3’ TS 23 kJ/mol
3’
3’ 5’ 137 kJ/mol
→ 3 80 ℃5NON
DFT 2’ 3’ IntInt 2’ (1+2)→ 2
6 (C–C 1.598(2) Å)
6
5
Int 3’ 6π
Scheme 4. Generation of an Acyclic Product Containing acis, cis, cis Triene Fragment by the Reaction of 3 with a TinElectrophile
cis,cis,cis
Other Experiments and Next Approach
→
(= A E )
s- p- 2018(
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