Ruthenium-Catalysed Asymmetric Reduction of Ketones

The asymmetric reduction of carbonyl, C=O, groups for the production of enantiomerically pure secondary alcohols is a reaction of fundamental importance in modern synthetic chemistry. This reaction can be performed in a number of ways. Asymmetric chemocatalysis (1) and the often complementary biocatalysis offer solutions to the stereoselective reduction of C=O groups. These two techniques have found wide industrial application (2). In the mid 1990s, two new ruthenium systems based on dihydrogen or transfer hydrogenation for asymmetric reduction of prochiral ketones were developed by Professors Noyori and Ikariya. These systems enable catalytic asymmetric reduction to provide a route for the generation of enantiomerically pure secondary alcohols in a highly efficient, simple and economic way (3). This paper describes some robust and cost-effective chemocatalytic technology for asymmetric ketone reduction, using ruthenium catalysts with diphosphine ligands.