Synthesis of Optically Activeα-Isopropyl-4-substituted Phenylacetic Acids by Asymmetric Hydrogenation

Homogeneous hydrogenation of 2-phenyl-3-methyl-2-butenoic acid derivatives in the presence of a catalytic amount of such chiral phosphine-rhodium complexes as Rh/(R)-BINAP, Rh/(R)-, or (S)-Cy-BINAP, Rh/(R)-p-tolyl-BINAP, and Rh/(R)-p-methoxy-phenyl-BINAP afforded the corresponding phenylacetic acid derivatives in high enantiomeric excesses and in quantitative chemical yields. The optically active phenylacetic acid derivatives are useful intermediates of agrochemicals and pharmaceuticals.