CHIRAL N,N-DIALKYLNOREPHEDRINES AS CATALYSTS OF THE HIGHLY ENANTIOSELECTIVE ADDITION OF DIALKYLZINCS TO ALIPHATIC AND AROMATIC-ALDEHYDES - THE ASYMMETRIC-SYNTHESIS OF SECONDARY ALIPHATIC AND AROMATIC ALCOHOLS OF HIGH OPTICAL PURITY

The chiral N,N-dialkylnorephedrine-catalyzed addition of dialkylzincs to aliphatic and aromatic aldehydes afforded secondary alcohols of high optical purity (to > 95% ee). Among the N,N-di(primary alkyl)norephedrines, N,N-di-n-butylnorephedrine (DBNE, 3d) was found to be the most effective catalyst. 1-Phenyl-2-(1-pyrrolidinyl)propan-1-ol (3i) and N,N-diallylnorephedrine (3j) were also highly effective catalysts. The method described provides optically active secondary aliphatic alcohols of high optical purity which cannot be prepared by conventional methods.