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

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.