Rhodium-Catalyzed Asymmetric Hydrogenation of 3-Benzoylaminocoumarins for the Synthesis of Chiral 3-Amino Dihydrocoumarins

An asymmetric hydrogenation of 3-benzoylaminocoumarins was achieved for the first time using our BridgePhos-Rh catalytic system, providing chiral 3-amino dihydrocoumarins in high yields (up to 98 %) and with excellent enantioselectivities (up to 99.7 % ee). The relationship between the enantioselectivities of the hydrogenations and the dihedral angles and the resulting pi-pi stacking effects of the BridgePhos-Rh complexes, which were determined by X-ray diffraction analysis, are discussed. The corresponding hydrogenated products allow for many transformations, providing several chiral skeletons with important physiological and pharmacological activities.