Highly Diastereo- and Enantioselective Direct Aldol Reactions Promoted by Water-Compatible Organocatalysts Bearing Central and Axial Chiral Elements

Two novel bifunctional primary amine catalysts 1 (R-A,S,S) and 2 (R-A,R,R), which bear both central and axial chiral elements, have been developed to promote highly diastereoselective and enantioselective aldol reactions of arylaldehydes with cyclic and acyclic ketones in the presence of water at room temperature. The catalyst 2 (RA,R,R) afforded the desired products with high levels of anti diastereoselectivity (up to 99:1) and enantioselectivity (up to 98%), showing that the two chiral elements of catalyst 2 (R-A,R,R) are matched, and enhance the stereochemical control. In addition, the catalyst 2 (R-A,R,R) was found to catalyze the direct aldol reaction of 4-nitrobenzaldehyde with 2-cyclohexanone under neat reaction conditions at room temperature with the high anti diastereoselectivity (98:2) and enantioselectivity (98%).