Solvent-free mechanochemical synthesis of phosphonium salts

Phosphonium salts have been prepared during high- energy ball- milling of triphenylphosphine with solid organic bromides; the reactions occur at ambient conditions without a solvent; in the case of 2- bromo- 2- phenylacetophenone the reaction in a solution usually produces a mixture containing both the C- phosphorylated and O- phosphorylated compounds, while the solvent- free mechanically induced transformation results in the thermodynamically favorable C-phosphorylated product; the occurrence of the observed transformations during mechanical processing of solid reactants is confirmed by the solid-state P-31 NMR spectroscopy and X- ray powder diffraction.