Asymmetric Organocatalytic Protonation of Silyl Enolates Catalyzed by Simple and Original Betaines Derived from Cinchona Alkaloids

摘要

The asymmetric protonation of silyl enolates derived from tetralone, benzosuberone, and cyclohexanone has been successfully achieved by using simple and original betaine catalysts derived from Cinchona alkaloids (quinine and quinidine series) to afford the desired α-substituted ketones in high yields and moderate enantioselectivities. The ease of implementation of this approach along with the easy accessibility of the betaine catalyst (four steps from cheap and commercially available quinine or quinidine) make this approach very appealing for the preparation of enantioenriched α- monosubstituted carbonyl compounds.