Asymmetric Hydrogenation of C=O Double Bond with Modified Raney Nickel Catalyst. XXIII

Abstract

Abstract The ultraviolet spectra of acetylacetone and methyl acetoacetate adsorbed on evaporated nickel film modified with amino or hydroxy acid were measured. The spectroscopic data suggested that the adsorbed species of acetylacetone was affected by the modifying pH, that the interaction between acetylacetone and the hydroxy acid was different from that between acetylacetone and the amino acid, and also that methyl acetoacetate, similar to acetylacetone, chemisorbed with a pseudo aromatic ring on the nickel surface. Consequently, the above results strongly support the theory that in the asymmetic hydrogenation, the substrate, acetylacetone or methyl acetoacetate, approaches the catalyst surface in a form like a pseudo aromatic ring, that it is asymmetrically controlled by the modifying reagent adsorbed on the catalyst surface, and, further, that the ease of the adsorption of the substrate onto the catalyst determines the rate of asymmetric hydrogenation.