Highly selective direct aldol reaction organocatalyzed by (S)-BINAM-L-prolinamide and benzoic acid using α-chalcogen-substituted ketones as donors

Abstract

Recoverable (S)-BINAM-L-prolinamide in combination with benzoic acid catalyzes and accelerates the direct aldol reaction between several α-chalcogen-substituted ketones and p-nitrobenzaldehyde in different solvents, including water. Choosing conveniently the aldol donor, solvent and conditions, it is possible to obtain mainly one of the two possible regioisomers with good diastero- and enantioselectivity. Thus, α-hydroxy and α-alkoxyacetones give mainly syn/anti regioisomers, whereas α-(methylsulphanyl)acetone affords the iso-aldol in 93% ee. In the case of α-hydroxy and α-methoxyacetone the anti diasteromer is obtained with up to 84% ee. However, α-benzyloxyacetone yields mainly the syn-diasteroisomer in 85% ee. ©ARKAT USA, Inc.