Highly Chemoselective Allylic Reductions with Silicon Hydrides and Palladium Catalyst

Novel reducing systems, comprising various silicon hydrides and a soluble palladium(0) catalyst, allow very mild and chemoselective reductive cleavage of allylic heterosubstituents. Other easily‐reducible functionalities such as ketones, aldehydes and Michael‐acceptors are not affected under these conditions. The relative reactivities of twelve commercially available silanes towards allylic reduction were determined using 1H NMR techniques. Similarly, the role of various reaction parameters such as temperature, solvent and concentration of reactants, and the effect of added water and zinc chloride on the reduction rate have been studied.