Catalytic enantioselective synthesis of quaternary stereocenters via intermolecular C-acylation of silyl ketene acetals: dual activation of the electrophile and the nucleophile.

A nucleophile-catalyzed asymmetric intermolecular C-acylation of silyl ketene acetals by anhydrides has been developed, furnishing quaternary stereocenters with high enantioselectivity. Mechanistic studies support the hypothesis that the reaction involves activation both of the silyl ketene acetal (generation of an enolate) and of the anhydride (formation of an acylpyridinium ion).