Synthesis of 1,2,3‐Triphospholenes, 1,2‐Diphosphetes, and Unsymmetric Phospholes by Rhodium‐catalyzed Cleavage of P−P Bonds and Addition to Alkynes

The rhodium‐catalyzed addition reaction of cyclo ‐(PPh) 5 to alkynes in refluxing THF efficiently provide 1,2,3‐triphospholenes, in which the –PPh–PPh–PPh– group is transferred from cyclo ‐(PPh) 5 by the cleavage of P−P bonds. In refluxing chlorobenzene, the reactions are accompanied by the formation of 1,2‐diphosphetes. When the triphospholenes containing P−P bonds are reacted with reactive alkynes under rhodium‐catalyzed conditions, unsymmetric phospholes are obtained. The rhodium‐catalyzed reactions can be used to synthesize various phosphorus‐containing heterocycles with different numbers of phosphorus atoms.