Organosilanes in Metal-Catalyzed, Enantioselective Reductions

The growth and development of an extensive range of metals complexed with chiral ligands for the purpose of catalyzing a variety of reactions in an enantioselective manner has been impressive for its scope, chemical yields and high ee values. Chief among the classes of synthetic transformations has been that of the asymmetric reduction of prochiral substrates. These include the asymmetric reduction of prochiral ketones, imines, unsaturated aldehydes, ketones, esters, nitriles and olefins, as well as a number of asymmetric coupling reactions. In concert with these efficient catalyst systems, organosilanes have the ability to carry out any number of organic reductions under a variety of conditions. In these reactions, which in reality are hydrosilylations (hydrosilylation and reduction are considered interchangeable herein) in which the initially resulting silylated product is hydrolyzed to the ultimate desired functionality, the ability to sterically and electronically alter the organosilane reductant can contribute to the overall success of the transformation. In this review, we present a thorough compilation of the literature covering the use of organosilanes in metal-catalyzed asymmetric reductions (hydrosilylations) and coupling reactions.