Superbase‐Assisted Selective Synthesis of Triarylphosphines from Aryl Halides and Red Phosphorus: Three Consecutive Different SNAr Reactions in One Pot

Abstract

Aryl halides, ArX (Ar = Ph, 2‐, 3‐ and 4‐Tol, 1‐ and 2‐Np, 4‐C6H4CONH2; X = F, Cl, Br), rapidly and exothermically (100–180 °C, 0.5–2 h) react with red phosphorus in superbase systems KOH/L, where L is a polar nonhydroxylic complexing solvent (ligand), such as NMP, DMSO, HMPA, to afford the corresponding triarylphosphines (Ar3P) in up to 74 % yield (for X = F). Thus, three consecutive reactions of SNAr (aromatic nucleophilic substitution) to form the three C(sp2)–P bonds are realized in one pot. The synthesis is mostly chemoselective (with rare exception): neither mono‐ nor diphosphines have been isolated. The best results were attained when aryl fluorides were treated with red phosphorus (Pn) in the KOH/NMP superbase system. This environmentally friendly, PCl3‐free synthesis of Ar3P from available starting materials opens an easy and straightforward access to triarylphosphines, which are important ligands, synthetic auxiliaries, and components of high‐tech‐ and medicinally oriented complexes.