Heterogeneization of a new Ru(II) homogeneous asymmetric hydrogenation catalyst containing BINAP and the N-tridentate bpea ligand,through covalent attachment on amorphous AlPO_4 support

摘要

Following a new methodology to obtain hybrid organic-inorganic solids,the homogeneous complex [Ru~(II)(bpea) {(S)(-)(BINAP)}Cl](BF_4),(bpea = N,N-bis(2-pyridylmethyl)ethylamine and BINAP = 2,2'-bis(diphenylphosphino)-1,l'-binaph-thyl) has been covalently immobilized on an AlPO_4 amorphous solid.It was tested in the successive liquid phase enantioselective hydrogenation of several prochiral substrates such us dimethyl itaconate,methyl 2-acetamidoacrylate and methyl 2-acetamido-cinnamate,in CH_2Cl_2 as solvent,([subs]/[cat] = 0.016/0.000352 = 45.4),hydrogen pressure 6.8 atm and 50-70 deg C reaction temperatures.Results obtained indicate that the catalytic activity with a high enantioselectivity (99%) was maintained throughout 10 successive reactions.Furthermore,the immobilized catalyst was easily recovered when repeatedly used and handled for several days,under the same experimental conditions as those in a conventional heterogeneous supported Ru catalyst.