Metal-Free Reduction of Phosphine Oxides, Sulfoxides, and N-Oxides with Hydrosilanes using a Borinic Acid Precatalyst

The general reduction of phosphine oxides, sulfoxides, and amine N-oxides was achieved by combining bis(2-chlorophenyl)borinic acid with phenylsilane. The reaction was shown to tolerate a wide range of substrates and could be performed under mild conditions, with only 2.5 mol% of the easily synthesized catalyst. Mechanistic investigations pointed to a key borohydride as the real catalyst and at bis(2-chlorophenyl)borinic acid as a precatalyst.