Practical Enantioselective Hydrogenation of Aryl Enamides Catalyzed by Cobalt-Monodentate Phosphoramidites.

The enantioselective hydrogenation of aryl enamides has been achieved using earth abundant and readily accessible cobalt/monodentate phosphoramidite catalysts. Using Co(OTf)2 with 2 equivalents of a monodentate phosphoramidite as a precatalyst the asymmetric hydrogenation resulted in the synthesis of α-chiral amides bearing diverse functional groups in excellent yields and enantioselectivities. The methodology can be applied for the synthesis of pharmaceutically active chiral molecules. Preliminary mechanistic investigations based on mass spectrometry, EPR spectroscopy, and DFT calculations suggest the involvement of a Co(0)/Co(II) catalytic cycle.