Enantioselective hydrogenation over immobilised transition metal complex catalysts

Abstract

A series of heterogeneous chiral catalysts was prepared from rhodium diphosphine complexes [Rh(L-L)COD]Cl ((L-L) = diphosphine ligand and COD = cyclooctadiene), Al-MCM-41 and Al-MCM-48, respectively. Impregnation of the mesoporous Al-MCM-41 and Al-MCM-48 with the organometallic complexes in dichloromethane led to strongly bonded hydrogenation catalysts. The catalysts were characterised with XRD, FT-IR and MAS-NMR, as well as thermoprogrammed desorption of ammonia, thermogravimetric analysis, and nitrogen sorption experiments. The hydrogenation of dimethyl itaconate (I), methyl a-acetamidoacrylate (II), and methyl a-acetamidocinnamate (III) were studied as test reactions. The immobilised catalysts showed high activities and excellent chemo- and enantioselectivities. Up to 99% e.e., >99% conversion and 99% selectivity were observed in the case of studied prochiral oleflns. The catalysts could be reused without a loss of catalytic activity. Leaching of the homogeneous complex out of the mesoporous framework was not observed.