Mechanistic investigations of the Mukaiyama aldol reaction as a two part enantioselective reaction

Herein, we report a mechanistic investigation of an enantioselective tandem Mukaiyama aldol reaction, consisting of a carbon-carbon bond-forming reaction and a silylation protection step in which the enantioselectivity results exclusively from the silylation step. The reaction is carried out in the presence of a Lewis base paired with a chiral quarternary ammonium salt. Mechanistic studies indicate that the enantioselectivity of the silylation step is a kinetic resolution of the aldolate intermediate. The effects of sterics and electronics oil the aldehyde starting material are also presented. (C) 2008 Elsevier Ltd. All rights reserved.