Catalytic enantioselective construction of all-carbon quaternary stereocenters: Synthetic and mechanistic studies of the C-acylation of silyl ketene acetals

With the aid of an appropriate chiral catalyst, acyclic silyl ketene acetals react with anhydrides to furnish 1,3-dicarbonyl compounds that bear all-carbon quaternary stereocenters in good ee and yield. Mechanistic studies provide strong support for a catalytic cycle that involves activation of both the electrophile (anhydride -> acylpyridinium) and the nucleophile (silyl ketene acetal -> enolate).