Highly enantioselective direct aldol reaction catalyzed by organic molecules.

We have demonstrated that a new class of l-proline-based organic compounds catalyzed the direct aldol reaction between aldehydes and acetone to provide beta-hydroxy ketones in good yields. The reaction is efficient, and 5-10 mol % of the catalyst and excellent enantioselectivities (97-99% ee) were obtained in both aromatic and aliphatic aldehydes. The presence of a gem-diphenyl group at the beta-carbon is necessary for high enantioselectivity.