Radicals from Phosphorus Heterocycles

Anion-radicals were obtained by alkali-metal reduction of phospholes in ether solvents.602 Sodium and potassium gave radicals rapidly whereas lithium failed. The radicals persisted several days at — 80° but decomposed above - 30°. The persistence of the radicals and their relatively large phosphorus hyperfine splitting, e.g., 186, by comparison with anion-radicals from phosphines, were interpreted in terms of aromatic character.602 The results obtained here contrast with results obtained earlier for 187 where phenyl cleavage and small phosphine-like phosphorus splittings had been observed for the products of attempted anion-radical formation.603 Chemiluminescence on oxidation of the anion-radical of 1,2,5-triphenylphosphole has been reported.604 

When cation-radicals from A3-phosphorins such as 188 are formed in the presence of nucleophiles and excess of oxidant, further reaction takes place to give A5-phosphorin derivatives, e.g., 191, generated in the presence of methanol by oxidation of 188 with mercuric acetate.611-614 A crystal and molecular structure determination of a A5-phosphorin shows a planar heterocycle with spd-hybridized phosphorus.615 Anion- and cation-radicals are also obtainable from the A5-phosphorin system.606,611,612 

I am indebted to Dr. B. C. Gilbert for helpful comments during the preparation of this article and to my wife for invaluable assistance in the collation of references. 

School of Chemical Sciences, University of East Anglia, Norwich, England 

Copyright 1979 by Academic Press, Inc. All rights of reproduction in any form reserved. 

---

The mass spectra of a number of heterocyclic compounds have been reported. The fragmentation patterns of thiophosphoryl derivatives of phosphorinanes are sensitive to stereochemistry, thus for the series (95) facile loss of the HS radical is indicative of an axial PS bond. The seven-membered heterocycles (96 Ch = S, Se) undergo a remarkable migration of sulphur or selenium from phosphorus to carbon with ring cleavage. While exocyclic P-C bonds of five-and six-membered heterocycles in the phosphonic class may be readily cleaved with retention of the phosphorus ring system, the seven-membered ring (97) exhibits facile expulsion of a phosphorus radical. ... 

---