anion radical coupling
DESCRIPTION
Anion radical coupling. Anita Kożuch 19 IV 2011. Plan. methods for the formation of aryl-aryl bonds anionic cyclohydrogenation history mechanism applications. Selective formation of aryl-aryl bonds between reaction partners (no functionality other than C-H bonds at the carbon atom): - PowerPoint PPT PresentationTRANSCRIPT
Anion radical coupling
Plan
methods for the formation of aryl-aryl bonds
anionic cyclohydrogenation
history
mechanism
applications
Selective formation of aryl-aryl bonds between reaction partners (no functionality other than C-H bonds at the
carbon atom):
transition metal catalyzed cross-coupling reactions
oxidative dimerization of electron-rich arenes (Scholl,
Kovacic and others)
intramolecular oxidative dimerization (Müllen)
oxidative photocyclization of stilbenes to phenanthrenes
(Mallory reaction)
thermal cyclodehydrogenations by flash vacuum pyrolysis
anionic cyclodehydrogenation of aromatic hydrocarbons
Classic example of anionic cyclodehydrogenation:
Oxidative cyclization of 1,10-binaphthyl (1) to perylene (2)
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
Anion radical coupling as an unique method
the highest efficiency in conversion 1,1’-binaphthyl to perylene
alkali metals are used to induce oxidation
Classic example of anionic cyclodehydrogenation:
Oxidative cyclization of 1,10-binaphthyl (1) to perylene (2)
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
History
• first isolated by Miller
• mechanism discovered by accident in 1967 by Solodovnikov et al.
Br
+ Li
3%
H.Gilman, C.G.Brennen, J. Am. Chem. Soc. 1949, 71, 657
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
Definition
Aromatic radical anion
Ar + e- → Ar●-
Ar●- + e- → Ar2-
N. L. Holy, Chem. Rev. 1974, 74, 243
General types of anion reactions
Ar + C C + Ar
D
Ar2- + C C + Ar
D
General types of anion reactions
Ar + + Ar H
Ar2-
HB B-
+ HB B- + Ar H
Reactivity of a radical anion
Compound Electron affinity[eV]
NaphthaleneTriphenylene
PhenantrhreneAnthracene
0,152 ± 0,0160,284 ± 0,0200,308 ± 0,0240,552 ± 0,061
N. L. Holy, Chem. Rev. 1974, 74, 243
Mechanism
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
The equilibrium constatnt depends on:
nature of the metal hydrocarbon solvent temperature
M + Ar → Ar●- + M+
K, DME
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
-
H Hpath A
-
e- e-
path B
-
-
H H
2-
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
2- 2*-
[O] [O]
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
Examined conditions
K (in an excess), THF, at 80 ºC gave 73% yield
Other conditions examined (metal, solvent, temperature) gave yelds of 10% or less:
a) K, 1,2-dimethoxyethane, 80 ºC
b) K, diglyme, 80 ºC
c) K, toluene, 80 ºC
d) Na, THF, 66 ºC
e) Na, diglyme, 80 ºC
f) Na, TMEDA, 120 ºC
g) Na, toluene, 110 ºC
M. Rickhaus, A.P. Belanger, H. A. Wegner, L.T. Scott, J.Org.Chem. 2010, 75, 7358
Oxidative agent
exposure to oxygene (small scale)
elemental iodine
Na2S2O5
SO2
S.H.Bossmann, H.Durr, M.R. Pokhrel, Synthesis 2005, 6, 907
SO2 as an oxidative agent
N Na/THF
N-
N-
HH
Na+
Na+
SO2
N
N
49%
S. Hunig, I. Wehner, Synthesis 1989, 552
Applications
P. Schlichting, U. Rohr, K. Müllen, J. Mater. Chem. 1998, 8, 2651
R
R
R
R
K, DME
R= C5H11
C6H13
C8H17
C12H25
Applications
Applications
Reductive ring closure of helicenes
K, THF
A. Ayalon, M. Rabinovitz, Tetrahedron Lett. 1992, 33, 17, 2395
Applications
Terrylene synthesis
K, DME
U.Scherf, K. Müllen, Synthesis 1992, 23
Summary
• formation of aryl-aryl bonds• efficiency• unique method• oxidazing agent• obscure mechanism
Thank you !!!
Questions ???