Copper-dipyridylphosphine-polymethylhydrosiloxane: A practical and effective system for the asymmetric catalytic hydrosilylation of ketones

In the presence of the inexpensive and non-toxic stoichiometric reductant polymethylhydrosiloxane (PMHS), the chiral copper(II)-dipyridylphosphine catalyst displayed high efficiency in the stereoselective hydrosilylation of a wide scope of aryl alkyl and heteroaromatic ketones under an air atmosphere and mild conditions in good to excellent ees (up to 97%). With certain amounts of sodium tert-butoxide and tert-butyl alcohol as additives, the reaction on a 21-g substrate scale can be conveniently completed within a few hours even at a substrate-to-ligand (S/L) ratio of 50,000.