Enantioselective Conjugate Additions of Enolates and other Stabilized Carbon Nucleophiles

4 Enantioselective Conjugate Additions of Enolates and other Stabilized Carbon Nucleophiles 

Early experiments in the area of enantioselective conjugate additions of stabilized anions employed chiral amines as catalysts [105]. A milestone result was Wynberg s utilization of cinchona alkaloids including quinine (109) as promoter for the addition of indanone 108 to methyl vinyl ketone (Equation 20) [106]. In the experiment, adduct 110 was obtained in 76% ee and 99% yield. Moreover, Wynberg also found thiophenols to be suitable nucleophiles for the quinine-catalyzed enantioselective addition to unsaturated ketones [107]. 

Oniy diastereomer Yamamoto s asymmetric addition of amide cuprate [6] 

Deng s formation of adjacent quaternary and tertiary stereocenters [15] 

In 1993, Yamaguchi reported an important milestone in the use of chiral amines as catalysts for enantioselective conjugate addition reactions (Equation 22) [114, 115]. The rubidium salt of proline (120) proved particularly ef ficient by comparison to proline or to its other metal salts. In the course of studies aimed at optimizing the process, beneficial effects were observed in the presence of CsF as an additive. This procedure led to the production of Michael adduct 121 from enone 118 in 88% ee [115]. 

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