Aldol Reactions with α-Trimethylsilyl Ketones. Dual Roles of the Trimethylsilyl Group for Regiospecific Generation of Enolate Equivalents

Article abstract of DOI:10.1021/jo00198a017

Aldol reactions of α-trimethylsilyl ketones, R¹CH(SiMe3)COCH2R², with aldehydes or acetals have been examined under Lewis acidic and basic conditions.In the presence of stannic chloride or boron trifluoride etherate, α-trimethylsilyl ketones react with aldehydes or acetals on the carbon bearing the silyl group exclusively to afford the corresponding addition products.On the other hand, lithium diisopropylamide usually deprotonates the opposite carbon atom to generate enolates, R¹CH(SiMe3)C(OLi)=CHR², selectively, which yield another type of aldol product after removal of the silyl group.Thus, two types of aldols can be prepared regioselectively from common α-trimethylsilyl ketones.