ESR of new β-phosphorus nitroxides from aldo- and keto-nitrones

✍ Scribed by D. Lawrence Haire; Edward G. Janzen; Ivan Hrvoic

• Book ID: 101252768
• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 106 KB
• Volume: 37
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199911)37:11<767::aid-mrc527>3.0.co;2-1

✦ Synopsis

This investigation deals mainly with the synthesis of new phosphorus-nitroxide free radicals. Nitroxides with a ˇ 31 P group were synthesized from the aldo-nitrones ˛-phenyl-N-tert-butylnitrone and 5,5-dimethyl-1pyrroline-N-oxide (DMPO) as well as the keto-nitrones 2,5,5-trimethyl-1-pyrroline-N-oxide (2,5,5-M 3 PO) and 2phenyl-5,5-dimethyl-1-pyrroline-N-oxide (2-Ph-DMPO). Three different routes were explored. The first two routes involved nitronyl spin trapping of phosphorus-centred radicals generated thermally or photochemically by hydrogen abstraction by tert-butoxyl radicals from di-tert-butyl peroxyoxalate or from photoexcited benzophenone, respectively. The third approach used the addition of phosphorus anions (generated by the strong, hindered base lithium diisopropylamide) to the nitrones and subsequent one-electron oxidation to the corresponding nitroxides. The most novel feature of the work presented here may be the synthesis of ˇ-phosphoranyl [P(OR) 4 ] nitroxide spin adducts. For comparison purposes the related ˇ-phosphityl [P(O)(OR) 2 ] nitroxides were also assembled and characterized by ESR spectroscopy.