L-Proline derived arylmethanamine ligands and their application in the copper-catalyzed asymmetric Henry reaction: a rare example of a Cu-complex with a dicopper tetraacetate core

Abstract

A series of novel epimeric arylmethanamine ligands were synthesized from l-proline. Both epimers were subsequently examined in the copper(II)-catalyzed asymmetric Henry reaction. Product yield and stereoselectivity up to 92% ee indicated that the (S,S)-epimer was superior to the diamine with an (S,R)-configuration. An enhancement of enantioselectivity driven by the formation of a Cu(II) complex with a dicopper tetraacetate core was discovered. Two types of crystalline Cu(II) complexes were isolated, and their structures were established by X-ray analyses.