ASYMMETRIC ORGANOCATALYSIS - Catalytic Asymmetric Synthesis - page 55

Representative
utility

Representative
transformations

Amine Photoredox

cat al ysis catalysis

H 2 O Lig ht

Aldol

H 2 production

Friedel-crafts O Me

N

N

N
N

N
N

Vinylation

O 2 production

Ru 2+
N

N
H

Allylation

CH 4 production

Enolation

Enal reduction
Diels-alder

Energy storage

New organic
transformations

Figure 2A.4. New reactivity platforms: merging organocatalysis with photoredox catalysis.

O Me

O O

20 mol % cat.*

n -Hex N

O

Catalyst =

CO 2 t Bu O

n -Hex Me t -Bu

H

H

Ru(bpy) 3 Cl 2 (0.5 mol %)
2,6-lutidine, DMF, 23°C
fluorescent light

Br

CO 2 t Bu

•TfOH

70% yield
5:1 dr
99% ee

Scheme 2A.28. α -Alkylation of aldehydes via photoredox organocatalysis.

synthesis, was brought to fruition. The combination of Ru(bpy) 3 Cl 2 and an imidazolidi-
none organocatalyst renders this important alkylation reaction highly enantioselective
and operationally trivial (Scheme 2A.28 ) [42] .
This dual catalysis strategy has provided a new foundation for the design and inven-
tion of a number of new transformations of importance to the practitioners of asym-
metric chemical synthesis.

REFERENCES

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Organocatalysis: From Biomimetic Concepts to Application in Asymmetric Synthesis . Weinheim :
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