1-(Pyridin-2-yl)methanamine-Based Ruthenium Catalysts for Fast Transfer Hydrogenation of Carbonyl Compounds in 2-Propanol

This Microreview focuses on the development of novel ruthenium complexes displaying high performance in the catalytic asymmetric transfer hydrogenation of ketones with 2‐propanol, providing this procedure alternative to the hydrogenation with dihydrogen. The key role is played by 1‐(pyridin‐2‐yl)methanamine (Pyme) type ligands which in combination with appropriate phosphanes afforded ruthenium systems of unprecedented high catalytic activity and productivity for the reduction of ketones and aldehydes. For the pincer CNN complexes a mixed inner‐outer sphere mechanism involving Ru‐hydride and Ru‐alkoxide species is proposed. The excellent properties of these complexes are expected to have implications for the design of a new generation of catalysts.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) The catalytic transfer hydrogenation of carbonyl compounds allows easy synthesis of alcohols under mild conditions. This review describes recent achievements in the preparation of a novel class of highly efficient Rucatalysts based on the 1‐(pyridin‐2‐yl)methanamine motif. Asymmetric reduction of ketones occurs fast and with unprecedented productivity.