Asymmetric Nucleophilic Addition Reactions of Aldehydes with Optically Active Dithioacetals and Their Application to Optically Active a-Hydroxy Ketone Synthesis

Optically active dithioacetals were prepared by the reaction of acetals with dithiol (1) having a chiral binaphthyl skeleton. Asymmetric addition reactions of various aldehydes with lithiated dithioacetals smoothly proceeded to provide the corresponding chiral alcohols (4) and (5) in fair diastereomeric excess. Moreover, preparation of optically pure α-hydroxy ketone by removal of the chiral auxiliary of 4a was achieved without racemization.