Chiral auxiliaries for asymmetric synthesis: enantioselective addition of dialkylzincs to aldehydes catalyzed by chiral 1,2-disubstituted ferrocenyl amino alcohols

Abstract

Chiral 1,2-disubstituted ferrocenyl amino alcohols derived from (R)- and (S)-N,N-dimethyl-1-ferrocenylethylamines catalyze the enantioselective addition of dialkylzincs to aldehydes to afford optically active S and R secondary alcohols. The degree of enantioselectivity increases with increased bulk of substituents near the C-O and C-N bonds of the catalyst. Catalysts with R chirality at the carbon bearing the amino group and planar S chirality at the ferrocene nucleus afford S alcohols, regardless of the chirality of the carbon bearing the hydroxy group