Aryl phosphines are widely used ligands, e.g., in catalysis or pharmaceutical chemistry. They are usually synthesized using phosphorus chlorides, organometallics, or alkaline metals. A more environmentally benign method for their synthesis would be useful.

Boris A. Trofimov, A. E. Favorsky Institute of Chemistry, Irkutsk, Russia, and colleagues have developed an efficient and selective synthesis of aryl phosphines in good yields from red phosphorus (P_n)  and aryl halides. The synthesis proceeds via  three consecutive S_NAr reactions between the aryl halides and polyphosphide anions. The polyphosphide anions were generated in situ from the red phosphorus using superbase systems of the type KOH/L, where L is a polar complexing solvent. Under these conditions, red phosphorus is cleaved and supernucleophilic polyphosphide species are created.

The best results were achieved with aryl fluorides, red phosphorus, and a KOH/NMP system (NMP = N-methyl-2-pyrrolidone). According to the researchers, the reaction is readily scalable. It avoids toxic or ecologically harmful reactants, as well as harsh conditions.

• Superbase-Assisted Selective Synthesis of Triarylphosphines from Aryl Halides and Red Phosphorus: Three Consecutive Different S_NAr Reactions in One Pot,
  Svetlana F. Malysheva, Vladimir A. Kuimov, Natalia A. Belogorlova, Alexander I. Albanov, Nina K. Gusarova, Boris A. Trofimov,
  Eur. J. Org. Chem. 2019.
  https://doi.org/10.1002/ejoc.201901005