Conversion dependence of enantioselective hydrogenation of (E)-alpha-phenylcinnamic acid on cinchonidine-modified Pd/TiO2 catalyst

The enantioselectivity of a cinchonidine-modified Pd/TiO2 catalyst varied with the extent of conversion in the hydrogenation of (E)-alpha-phenylcinnamic acid. The incremental enantioselectivity reached a maximum at an early stage of the reaction. Under optimized reaction conditions, optical yields of up to 72%e.e. of (S)-(+)-2,3-diphenylpropionic acid were obtained at 100% conversion.