Dimethylsilyl ketene acetal as a nucleophile in asymmetric Michael reaction: Enhanced enantioselectivity in oxazaborolidinone-catalyzed reaction

Dimethylsilanyl [Me2Si(H)] ketene SO-acetal 6b is an effective nucleophile that retards the undesirable Si+-catalyzed racemic pathway in the oxazaborolidinone-catalyzed asymmetric Michael reaction. Through the further suppression of the Si+-catalyzed pathway by carrying out the reaction in the presence of 2,6-diisopropylphenol and t-BuOMe as additives, enantioselectivity up to 98% ee could be achieved for a variety of acyclic enones.