Conjugate catalytic, stabilized carbanions

Since the previous review in this comprehensive book [1], the asymmetric catalytic conjugate additions of stabilized carbanions have made considerable advances. Publications between 1996 and early 2002 are summarized in this supplementary according to the same categorization as before. Several reviews have also appeared on this subject [2-4]. 

Use of proline as a catalyst has become an important methodology in the catalytic asymmetric addition of stabilized carbanions to conjugated carbonyl compounds. Hannessian employed L-proline (S)-l in the addition of nitroalkanes to enones (Scheme 1) [5]. In the presence of 3-7 mol % of (S)-l and an excess of trans-2,5-dimethylpiperazine in chloroform, comparable or higher enantiose-lectivities were attained compared to the Yamaguchi s method using L-proline... 

Suppl. to Chapter 31.2 Catalytic Conjugate Addition of Stabilized Carbanions... 

The Birch reductions of C C double bonds with alkali metals in liquid ammonia or amines obey other rules than do the catalytic hydrogenations (D. Caine, 1976). In these reactions regio- and stereoselectivities are mainly determined by the stabilities of the intermediate carbanions. If one reduces, for example, the a, -unsaturated decalone below with lithium, a dianion is formed, whereof three different conformations (A), (B), and (C) are conceivable. Conformation (A) is the most stable, because repulsion disfavors the cis-decalin system (B) and in (C) the conjugation of the dianion is interrupted. Thus, protonation yields the trans-decalone system (G. Stork, 1964B). 

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