A magnetically recoverable chiral rhodium catalyst exhibited excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation of aromatic ketones in aqueous medium, which could be recovered easily via a small magnet and used repetitively ten times without obviously affecting its enantioselectivity.

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 iridiumA C H T U N G T R E N N U N G (III) or rhodiumA C H T U N G T R E N N U N G (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.

A chiral rhodium catalyst anchored on SiO2-coated Fe3O4 magnetic nanoparticles is synthesized, which exhibits excellent catalytic activity and enantioselectivity in asymmetric transfer hydrogenation reactions of aryl methyl ketones in aqueous medium. -(SUN, Y.; LIU*, G.; GU, H.; HUANG, T.; ZHANG, Y.; LI, H.; Chem. Commun. (Cambridge) 47 (2011) 9, 2583-2585, http://dx.doi.org/10.1039/c0cc03730c ; Lab. Resour. Chem., Shanghai Norm. Univ., Shanghai 200234, Peop. Rep. China; Eng.) -R. Staver 26-023