Proline-catalyzed asymmetric aldol reactions of tetrahydro-4H-thiopyran-4-one with aldehydes

Proline-catalyzed enantioselective direct intermolecular aldol reactions of tetrahydro-4H-thiopyran-4-one with various aldehydes give anti adducts with high diastereo- and enantioselectivities in moderate to excellent yields. With the aromatic aldehydes best results were obtained in wet DMF whereas dry DMSO generally was superior with the aliphatic aldehydes. Desulfurization of the adducts with Raney Ni provides products equivalent to aldols from 3-pentanone with potential applications in polypropionate synthesis.