A new efficient chiral iridium catalyst for asymmetric transfer hydrogenation of ketones

Abstract

Abstract The interaction of [Ir(COD)Cl]2 with chiral tetradentate diaminodiphosphine ligands gave chiral diaminodiphosphine-Ir(I) complexes, which were characterized by IR, NMR and CD. The new chiral iridium(I) complex catalysts were applied to asymmetric transfer hydrogenation of various aromatic ketones using 2-propanol as a source of hydrogen. The results showed that the corresponding chiral alcohols could be obtained with high activity (up to 99.4% yield) and excellent enantioselectivities (up to 99.0% ee) under mild conditions. Propiophenone was a preferred substrate with respect to catalytic activity and enantioselectivity in the presence of base. The catalytic turnover reached 4780 mol product/mol iridium and the turnover frequency was as high as 1593 h−1 at 55°C.