A chiral (alkoxy)methyl-substituted silicon group as an auxiliary for the stereoselective cuprate addition to $\alpha,\beta$-unsaturated ketones: synthesis of (−)-(R)-phenyl 2-phenylpropyl ketone

Abstract

The [(benzyloxy)methyl](tert-butyl)methylsilyl group was used as the chiral auxiliary to effect highly diastereoselective conjugate additions of organocuprates to enones. Thus, reaction of several R2CuLi with ct-silylated cx,13-unsaturated ketones afforded the respective addition products with rr-face selectivities of up to 99%. Starting with an optically active substrate, enantiomerically enriched (-)-(R)-phenyl 2-phenylpropyl ketone was prepared with virtually no loss of chiral information in a reaction sequence involving cuprate addition, hydrolysis, and removal of the silicon group.