Chiral Phosphoric Acid-Catalyzed Enantioselective Reductive Amination of 2‑Pyridyl Ketones: Construction of Structurally Chiral Pyridine-Based Ligands

A chiral phosphoric acid-catalyzed
one-pot enantioselective reductive
amination of 2-pyridyl ketones was realized to provide chiral pyridine-based
ligands in excellent yields with high enantioselectivities (up to
98% yield, 94% ee). Computational studies on the key intermediate
imine and transition state of the hydride transfer process revealed
that the nitrogen atom of the pyridyl ring might be an important factor
to significantly promote both the reaction activity and enantioselectivity.