Cyclic β-iminophosphine:: New P-stereogenic ligand for the asymmetric catalysed hydrogenation of ketones

A novel type of asymmetric C=O hydrogenation catalysts based on chiral beta-iminophosphine rhodium and ruthenium complexes was developed. The chirality of the ligand is centered on the phosphorus atom which can induce moderate enantioselectivity. A synergetic effect on both activity and enantioselectivity is observed when amines are introduced as co-ligands. Acetophenone is thus completely hydrogenated with ee values up to 68%. (c) 2005 Elsevier B.V. All rights reserved.