Effect of achiral condensed aromatic additives on the enantioselective hydrogenation of ethyl pyruvate over cinchonidine-platinum catalysts

The effect of the addition of various nitrogen containing and condensed aromatic compounds on both the rate and the enantioselectivity in the hydrogenation of over supported cinchonidine-Pt catalysts has been investigated. The results show that preadsorbed quinoline and acridine cannot be fully replaced from the surface of platinum by cinchonidine. It has been found that the addition of these compounds increases both the reaction rate and the enantioselectivity (both ee max and ee end values). The observation that these additives have no negative effect on the enantioselectivity indicates that generally accepted mechanistic models need some corrections.