Asymmetric syntheses. Part 2. Reduction of ketones with chiral sodium borohydride-lactic acid derivative systems
Asymmetric reduction of acetophenone, propiophenone, and 2-acetylnaphthalene using chirally modified reagents prepared from sodium borohydride and optically active (S)-lactic acid derivatives produced the corresponding optically active (R) alcohols with enantiomeric excesses as high as 38.3%. The extent of asymmetric synthesis was dependent on the catalyst, the solvent, and the reaction conditions. 1H and 13C N.m.r. data for sodium borohydride chiral species are reported.