Iridium-Catalyzed Asymmetric Hydrogenation of Imines

We have evaluated a wide range of iridium complexes derived from chiral oxazoline-based N,P ligands for the asymmetric hydrogenation of imines and identified three efficient catalysts. These catalysts are readily synthesized by straightforward convenient routes and are air and moisture stable. In the reduction of acetophenone N-arylimines and related acyclic substrates, excellent enantioselectivities (up to 96% ee) were obtained by using 0.1-0.5 mol% of catalyst at -20 degrees C and 5-50 bar hydrogen pressure.