Aqueous enantioselective hydrogenations involving silica-heterogenised catalysts

A mesoporous silica (HMS) has been prepared with an average pore size of 26 Angstrom. The pores have been shown to include typical chiral catalysts fo r enantioselective hydrogenation viz Rh-BPPM and Ru-BINAP. The heterogenise d catalysts have been shown to be effective for hydrogenations of water-sol uble alkenes, e.g. itaconic acid 3 and the sodium salt of N-acetamidocinnam ic acid (1a). Modest enantioselectivity was achieved for hydrogenation of t he cinnamic acid derivative (40-60% ee) but only poor values for the itacon ic acid (0 less than or equal to 16% ee). In some cases, the catalysts coul d be recovered and reused without significant loss of activity or selectivi ty. (C) 2000 Elsevier Science S.A. All rights reserved.