The role of cinchona alkaloids in enantioselective hydrogenation reactions: are they modifiers or hosts involved in supramolecular heterogeneous catalysis?

In this study experimental evidences are summarized supporting the modifier -substrate interaction taking place in the liquid phase in the enantioselec tive hydrogenation of cc-keto esters and related compounds. The results ind icate that the catalytic system cinchona alkaloids-supported platinum (or p alladium) can effectively be used in enantioselective hydrogenation for pro chiral substrates, in which the prochiral group is part of a conjugated dou ble bond system. It is considered that the above catalytic system is the fi rst example of a new class of heterogeneous catalytic reactions with the in volvement of supramolecular catalysis. (C) 2000 Elsevier Science B.V. All r ights reserved.