A comparison of the asymmetric hydrogenation catalyzed by rhodium complexes containing chiral ligands with a binaphthyl unit and those with a 5,5′,6,6′,7,7′,8,8′-octahydro-binaphthyl unit

Article abstract of DOI:10.1016/S0957-4166(01)00399-8

The chiral ligands H₈-BINAPO and H₈-BDPAB were synthesized by reacting chlorodiphenylphosphine with H₈-BINOL and H₈-BINAM, respectively. Applications of these ligands in the Rh-catalyzed enantioselective hydrogenation of a variety of (Z)-acetamido-3-arylacrylic acid methyl esters provided chiral amino acid derivatives with good to excellent enantioselectivities (H₈-BINAPO: up to 84.0% e.e.; H₈-BDPAB: up to 97.1% e.e.). In the hydrogenation of acetamidoacrylic acid, 99% e.e. was obtained when a [Rh(H₈-BDPAB)]⁺ catalyst was used. The catalytic activities and enantioselectivities of [Rh(H₈-BINAPO)]⁺ and [Rh(H₈-BDPAB]⁺ are substantially better than those obtained with the corresponding rhodium catalysts containing BINAPO (up to 64% e.e.) and BDPAB (up to 92.6% e.e.).