Asymmetric hydrogen-transfer reduction of prochiral and α,β-unsaturated ketones by iridium complexes containing optically pure aminodiphosphine ligands

This work reports the catalytic reduction, via hydrogen-transfer from propan-2-ol, of various alpha,beta-unsaturated ketones or unsymmetrical ketones in the presence of [Lr(COD)(OMe)](2) and the chiral aminodiphosphine ligands (R)-PhC *H(Me)N(CH2CH2PR2)(2) (R = Ph, Cy) and (R)-(Et)C *H(Me)N(CH2CH2PPh2)(2). In general, these catalyst systems show good activity but modest enantioselectivity. Both the chemoselectivity and the enantioselectivity for the reduction of alpha,beta-unsaturated ketones to optically pure allylic alcohols depend on the nature of the substituent(s) at either the carbon stereocentre or the phosphorus substituents. (C) 1998 Elsevier Science B.V. All rights reserved.