Catalytic Enantioselective Addition of Organometallic Reagents to N-Formylimines Using Monodentate Phosphoramidite Ligands

The asymmetric synthesis of protected amines via the copper/phosphoramidite-catalyzed addition of organozinc and organoaluminum reagents to N-acylimines, generated in situ from aromatic and aliphatic alpha-amidosulfones, is reported. High yields of optically active N-formyl-protected amines and enantioselectivities up to 99% were obtained. Under the reaction conditions, partial oxidation of the phosphoramidite ligand to the corresponding phosphoric amide was detected. A preliminary study on the origin and the effect on the catalytic addition reaction is presented.