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

Abstract

Aryl halides, ArX (Ar = Ph, 2‐, 3‐ and 4‐Tol, 1‐ and 2‐Np, 4‐C 6 H 4 CONH 2 ; 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 (Ar 3 P) in up to 74 % yield (for X = F). Thus, three consecutive reactions of S N Ar (aromatic nucleophilic substitution) to form the three C(sp 2 )–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 (P n ) in the KOH/NMP superbase system. This environmentally friendly, PCl 3 ‐free synthesis of Ar 3 P 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.