Direct enantioseparation of diarylmethylamines with an ortho-hydroxy group via diastereomeric salt formation and their application to the enantioselective addition reaction of diethylzinc

Abstract

Two chiral diarylmethylamines with a phenolic hydroxy group at their ortho positions (1c and 1d) were synthesized, and their direct enantioseparation via diastereomeric salt formation was investigated. Crystallographic analyses of the diastereomeric salts involving 1c were conducted: water molecules incorporated in the space played an important role in chiral recognition. Enantiopure 1 were applied for the enantioselective addition of diethylzinc to benzaldehyde. Ligand (R)-1d afforded the product in very high yield (96%) and enantiopurity (92% ee). Not only the phenyl group on the stereogenic center of (R)-1d but also its bulky tert-butyl group is important for chiral induction.