Chiral bisphosphanes. 8. Enantioselective hydrogenation of alpha-acetamidocinnamic acid by cationic rhodium(I) complexes with optically pure (1S,2S)-cyclopentane-1,2-diyl-bis(phosphonous acid diester) ligands and (1S,2S)-cyclopentane-1,2-diyl-bis(pho

摘要

Treatment of [(1,5-COD)(2)Rh]O3SCF3 with optically active P-2 ligands of the type (1S,2S)-C5H8(PR2)(2) [PR2 = P(OMe)(2) (3), P(OPh)(2) (4), P[OCH(Me)Et-(S)](2) (5), P[2-OC10H6C10H6O-2'-(R)] (6), P(NC4H8O-cyclo)(2) (7)] gave cationic rhodium complexes bearing these new ligands, [(1,5-COD)Rh{(PR2)(2)C5H8-(1S,2S)}]O3SCF3 (Rh-3-7). Use of these as catalysts in the homogeneous enantioselective hydrogenation of alpha-acetamidocinnamic acid to N-acetylphenylalanine provided optical yields of 75-78% ee for the complexes [(1,5-COD)Rh{[P(OPh)(2)](2)C5H8-(1S,2S)}]O3SCF3 (Rh-4) and [(1,5-COD)Rh{[P(OCH(Me)Et-(S)](2))(2)C5H8-(1S,2S)}]O3SCF3 (Rh-5), respectively. [References: 17]