Effect of Zinc Metal on the Stereocontrol of Iron-Catalyzed Hydrosilane Reduction

Significance

In this paper the authors describe the enantioselective hydrosilane reduction of ketones mediated by iron catalysts with chiral BOPA ligands. Both enantiomers of the product can often be accessed from the same chiral source; in most cases the sense of the enantiocontrol was found to be reversed upon the addition of small amounts of zinc powder. Few substrates furnished the products of identical configuration in both the presence and absence of zinc. The use of ligand 2 allowed the preparation of a number of products with up to 99% yield and 32-95% ee.