Samarium‐Catalyzed Diastereoselective Double Addition of Phenylphosphine to Imines and Mechanistic Studies by DFT Calculations

Catalytic hydrophosphination of imines represents the most straigtforward and atom-economic strategy for the preparation of α-aminophosphines, which are useful as biologically active molecules and ligands for catalysis. The first catalytic protocol for the rapid and high-yield hydrophosphination of common imines enabled by an ene-diamido samarium methoxide as catalyst has been developed. The reaction allowed the efficient and diastereoselective synthesis of various bis(α-amino)phosphines via the double addition of PhPH2 to common imines. The catalytic reaction features a relatively wide range of substrate scope, high diastereoselectivities (up to 99:1 dr for meso-products) and high yields (up to 97%). The DFT calculations disclosed the inner-sphere mechanism involving the unprecedent activation of a Sm-O bond by a phosphine and the stabilization of the addition intermediates by the metal center.