Enantioselective hydrogenation of ethyl pyruvate over cinchonidine–Pt/Al2O3 catalysts containing anchored silicium organic moieties Original Research Article

The enantioselective hydrogenation of ethyl pyruvate was investigated over a catalytic system consisting of a Pt/Al2O3 catalyst containing silicium organic moieties anchored to the support and cinchonidine, the chiral template molecule. The –Si(CH3)2R moieties (where R=–CH3 or –C8H17) were anchored to the alumina via surface reaction of silicium organic compounds and the surface OH groups of the support. The introduction of –Si(CH2)nR moieties onto the alumina significantly decreased both the rate and the enantioselectivity of the hydrogenation reaction. The decrease of the enantioselectivity indicates that the enantio-differentiation step is more complex than it is predicted by the existing models. The results also show that the enantio-differentiation step cannot be exclusively attributed to the interaction between the half-hydrogenated substrate and cinchonidine taking place at the platinum surface.