Magnetically Recoverable Nanoparticles: Highly Efficient Catalysts for Asymmetric Transfer Hydrogenation of Aromatic Ketones in Aqueous Medium

Two magnetic chiral iridium and rhodium catalysts were prepared via directly postgrafting 1,2-diphenylethylenediamine-derived organic silica or 1,2-cyclohexanediamine-derived organic silica onto the silica-coated iron oxide nanoparticles followed by complexation with iridium(III) or rhodium(III) complexes. During the asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, the magnetic chiral catalysts exhibited high catalytic activities (up to 99% conversion) and enantioselectivities (up to 92% ee). Both catalysts could be recovered easily by magnetic separation and be reused ten times without significantly affecting their catalytic activities and enantioselectivities.