Addition of carbon nucleophiles to hemiaminals promoted by a Lewis acidic polyoxotungstate

Abstract

A Lewis acidic hafnium(IV) ion incorporated in a polyoxotungstate (POM/Hf) was successfully employed as recoverable catalyst in the nucleophilic addition of carbon nucleophiles, such as silyl enol ethers, silyl ketene acetals, β-diketones and β-diketoesters, to unprotected hydroxy aminal at room temperature. The corresponding α-substituted heterocycles were obtained in good yields and the recovered POM catalyst could be reused up to three times without significant loss of activity.