Synthesis and application of ligands for the asymmetric addition of organolithium reagents to imines

Abstract

Amino acid derived ligands 4d,e are prepared from (S)-valine and (S)-proline respectively, and can be used as chiral ligands during the asymmetric addition of organolithium reagents to N-arylimines. Ligand 4e, which is prepared by two independent routes, is found to induce addition of organolithium reagents to the si-face of the imines, whilst ligand 4d in common with the previously reported catalysts 4a–c induces addition to the re-face of the imines.