Electron spin resonance study of phosphorus-nitroxides from 1,3-additions of silicon-phosphorus reagents to nitrones.
This article explores a new, convenient route to beta-phosphorus nitroxides. Specifically, the reaction sequence involves the novel 1,3-addition of trimethylsilyl phosphites (e.g. diethyl) or trimethylsilyl phosphines (e.g. diphenyl) to aldo-nitrones [e.g. alpha-phenyl-N-tert-butylnitrone (PBN) or 5,5-dimethyl-l-pyrroline-N-oxide (DMPO)] or keto-nitrones [e.g. 2-ethyl-5,5-dimethyl-1 pyrroline-N-oxide (2-Et-DMPO) or 2-phenyl-5,5-dimethyl-l-pyrroline-N-oxide (2-Ph-DMPO)] to form alpha-phosphityl- or alpha-phosphinyl-O-silylhydroxylamines. Acidic hydrolysis provides the corresponding hydroxylamines that are easily oxidized to the title beta-phosphorus-nitroxides. ESR spectroscopic analysis revealed some very large beta-phosphorus hyperfine splittings (i.e. in excess of 5 mT). For this reason and their remarkable stability (persistence) some of these nitroxides show promise as integral components in new, improved weak-field dynamic nuclear polarization (DNP) magnetometers.
Haire
D Lawrence
DL
Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1, Canada. lhaire@uoguelph.ca
Janzen
Edward G
EG
Robinson
Valerie J
VJ
Hrvoic
Ivan
I
D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006898:Hydroxylamines / Q000138:chemical synthesis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D015394:Molecular Structure; D009589:Nitrogen Oxides / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D017646:Organosilicon Compounds / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D017553:Phosphorus Compounds / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry
D003497:Cyclic N-Oxides; D006898:Hydroxylamines; D009589:Nitrogen Oxides; D009942:Organometallic Compounds; D017646:Organosilicon Compounds; D017553:Phosphorus Compounds; C015388:nitrones; D010758:Phosphorus; C029217:phenyl-N-tert-butylnitrone; C095292:5,5-dimethyl-2-phenyl-1-pyrroline-N-oxide; C017245:5,5-dimethyl-1-pyrroline-1-oxide; C039900:nitroxyl; D012825:Silicon