Transition‐Metal‐Free Mechanochemical Construction of C─P Bonds Using Diazonium Salts With H‐Phosphonates and Phosphine Oxides

A transition‐metal‐free mechanochemical protocol for the construction of C─P bonds is reported. The reaction employs aryldiazonium tetrafluoroborates and bench‐stable P(O)─H compounds (H‐phosphonates and phosphine oxides) under solvent‐free ball‐milling conditions at room temperature. In contrast to a previously reported radical‐based mechanochemical C─P coupling utilizing stoichiometric magnesium and phosphoryl chlorides, our method operates via an ionic nucleophilic substitution pathway, as supported by the lack of inhibition by TEMPO and 1,1‐diphenylethylene and the accelerating effect of electron‐donating substituents. The protocol displays a broad substrate scope (43 examples, up to 96% yield), excellent functional group tolerance, and gram‐scale applicability, providing a practical and sustainable route to arylphosphonates and arylphosphine oxides.