Development of P- and N-Chirogenic Ligands Based on Chiral Induction from a Phosphorus Donor to a Nitrogen Donor in Palladium Complexes

Abstract

We herein designed and synthesized amino-phosphine ligands 1a–c, which bear a P-chirogenic group, (R)-PtBuMe, and an N-group (NHR) on the pyridylene backbone, as a novel class of chiral ligands possessing chirogenic donors. Ligand 1a (R = Me) stereoselectively coordinated with PdCl2 to predominantly afford the P- and N-chirogenic metal complex 4a having an RN,SP configuration. In contrast, ligands 1b (R = iPr) and 1c (R = tBu) produced a mixture of diastereomers derived from two possible N-centered configurations. In complex 4a, the N-centered configuration was efficiently controlled by the P-chirogenic center via through-space attractive interactions between P-tBu and N-Me. Buried volume analysis indicated that this novel ligand creates a unique C1-symmetric chiral environment derived from both steric and electronic asymmetry.