Stereodifferentiation in heterogeneous catalytic hydrogenation. Kinetic resolution and asymmetric hydrogenation in the presence of (S)-proline: Catalyst-dependent processes

The kinetic resolution of 3,5,5-trimethyl cyclohexanone (TMCH) and asymmetric hydrogenation of isophorone (3,5,5-trimethyl cyclohex-2-enone, IP) were investigated on different Pd catalysts in the presence of (S)-proline (Pr). It could be proven that in isophorone hydrogenation the optically active TMCH was formed not only by kinetic resolution but also through asymmetric Cdouble bond; length as m-dashC hydrogenation. The activity and stereoselectivity of different Pd catalysts depended on the support material, preparation method, and reaction conditions as well, confirming our assumption that enantiodifferentiation takes also place on the catalyst surface and not only in the homogeneous liquid phase condensation reaction.