抄録
The Claisen condensation is recognized as a fundamental and useful C-C bond forming reaction to obtain β-keto esters in organic syntheses. However, α,α-dialkylated esters could not undergo this type of the condensation, because these esters lack the ability to force the formation of a stable enolate. Now, we developed a new practical, efficient and powerful crossed Claisen condensation of α,α-dialkylated esters between ketene silyl acetals and various electrophiles (acid chlorides, carboxylic acids, esters). Taking into account the fact that the Claisen condensation ofα,α-dialkylated esters is very difficult, the present method will provide a new avenue for the preparation of inaccessible β-ketoesters. The present method could be successfully applied to a facile synthesis of pyrazolone derivatives.
