Mechanochemistry enabled highly efficient solvent-free deoxygenation of phosphine oxides in air†

Deoxygenation of phosphine oxides is an important method for the synthesis of valuable organophosphine compounds and recycling of phosphorus resources. However, existing solution-based deoxygenation protocols usually require long reaction times, significant amounts of potentially harmful organic solvents, and inert gas atmospheres. In addition, reactions of poorly soluble phosphine oxides are challenging and often inefficient. Herein, we demonstrate that a high-temperature mechanochemical protocol enables the highly efficient solvent-free deoxygenation of phosphine oxides with hydrosilanes in the presence of a phosphoric acid additive. These reactions were rapid and completed within 30 min for most substrates. Notably, this is the first practical deoxygenation of phosphine oxides in which all synthetic operations can be carried out in air. A preliminary study on the mechanochemical catalytic Wittig reaction is also described.