Homogeneous and heterogeneous catalytic asymmetric reactions IV. Hydrogenation of the Ni complexes of cinnamic acid salts over MRNi catalyst

Abstract

Substituted cinnamic acids containing a prochiral CC bond, and their LiI, KI, NiII and CaII salts, were prepared and their surface complexes on Ni were studied over a Raney-Ni catalyst modified with tartaric acid. The hydrogenation product of sodium cinnamate is optically active. Of the alkali metal salts of (E)-α-phenylcinnamic acid, the hydrogenation of the Na salt gives the highest optical yield (17%). The solvent used significantly influences the selectivity. The published data for the chiral RH complexes are listed for comparison with the results of the homogeneous and heterogeneous hydrogenations described.The enantioselectivity in the presence of Raney-Ni is the result of a complex formed by the interaction of (R,R)-tartaric acid with the substrate.