Reaction of Silylketenes with Carbanions : Simple Preparation of α-Silylketones Using Organocerium Reagents

Abstract

Preparation of α-silylketones 1 by the reaction of three kinds of silylketenes 3a-c with various organometallic reagents 4 was studied. Although the use of n-BuLi, MeMgBr, Me₂CuLi, Et₃Al, and Et₂Zn resulted in complicated reactions, organocerium reagents 4 (M=CeCl₂) added selectively to the carbonyl carbon of 3 to generate enolate anions A, which were treated with aqueous NH₄Cl or alkyl halides 5 to give 1. Seventeen α-silylketones 1a-q were prepared in 31-99% yields from three components, 3, alkyl- or arylcerium reagents 4, and proton or alkyl halides 5. This method was applied to a regiocontrolled preparation of two isomeric α-silylketones 1r, s.