Reductive Amination of Carboxylic Acids via Nickel(II) Catalysis: A Ligand-Tuned Strategy for C–N Bond Formation

A nickel(II)-catalyzed reductive amination of carboxylic acids with amines is described, employing phenylsilane as the reductant. The reaction proceeds via an iminium ion/imine intermediate and does not require prior carboxylic acid activation. A comprehensive evaluation of ligands identified bulky trialkyl monophosphines as optimal, with tricyclohexylphosphine providing the highest yield. This ligand-controlled protocol provides direct access to diverse secondary and tertiary amines from readily available carboxylic acids, illustrating a practical approach to C-N bond formation.