Enantioselective hydrogenation over immobilized rhodium diphosphine complexes on mesostructured materials

Abstract

New heterogeneous chiral catalysts were prepared from rhodium diphosphine complexes [Rh(P–P)COD]Cl ((P–P) = diphosphine ligand and COD = cyclooctadiene), and Al–MCM-41, Al–MCM-48, and Al–SBA-15, respectively. Impregnation of the mesoporous Al–MCM-41, Al–MCM-48, and Al–SBA-15 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, methyl α-acetamidoacrylate, and methyl α-acetamidocinnamate were studied as test reactions. The immobilized catalysts showed high activities and excellent chemo- and enantioselectivities. Up to 98% e.e., >99% conversion and 99% selectivity were observed in the case of studied prochiral olefins. The catalysts could be reused without a loss of catalytic activity. Leaching of the homogeneous complex out of the mesoporous framework was not observed.