Phosphole

Phosphole is the organic compound with the chemical formula C₄H₄PH; it is the phosphorus analog of pyrrole. The term phosphole also refers to substituted derivatives of the parent heterocycle. These compounds are of theoretical interest but also serve as ligands for transition metals and as precursors to more complex organophosphorus compounds.

The first phosphole was discovered in 1953, pentaphenylphosphole followed in 1959 and the parent compound, phosphole itself, was first synthesized in 1987 ["A Guide to Organophosphorus Chemistry" Louis D. Quin 2000 John Wiley & Sons ISBN 0-471-31824-8] . Phenylphospholes can be prepared via treatment of an organozirconium compound with PhPCl₂. [OrgSynth | author = Paul J. Fagan and William A. Nugent | title = 1-Phenyl-2,3,4,5-Tetramethylphosphole| collvol = 9 | collvolpages = 653| year = 1998 | prep = CV9P0653]

Unlike other the 5-membered heterocycles pyrrole, thiophene, and furan, the aromaticity of phospholes is diminished, reflecting the reluctance of phosphorus to delocalize its lone pair. [D. B. Chesnut, L. D. Quin "The important role of the phosphorus lone pair in phosphole aromaticity" Heteroatom Chemistry 2007, Volume 18754-758. DOI: 10.1002/hc.20364.] For example, phospholes undergo Diels-Alder reactions with electrophilic alkynes. :

See also

* Organophosphorus chemistry
* Phosphorine

References