Enantioselective hydrogenation of ethyl-2-oxo-4-phenylbutyrate on cinchonidine-modified Pt/γ-Al2O3 catalyst using a fixed-bed reactor

Enantioselective hydrogenation of ethyl-2-oxo-4-phenylbutyrate (EOPB) on a cinchonidine-modified Pt/gamma-Al2O3 catalyst was carried out using a fixed-bed reactor to obtain the chiral product, (R)-(+)-ethyl-2-hydroxy-4-phenylbutyrate ((R)-(+)-EHPB). About 95% conversion and 68% ee of the (R)-(+)-EHPB were obtained for the cinchonidine-modified Pt/gamma-Al2O3 catalyst in a continuous-flow reaction system with a fixed-bed reactor. It is observed that the ee of (R)-(+)-EHPB strongly depends on the different solvent and hydrogen pressure. The competitive adsorption between the solvent and reactant molecule plays an important role in determining the ee value of (R)-(+)-EHPB. This study also shows that a compact adsorption of chiral modifiers on the platinum surface is beneficial to the higher enantioselectivity.