Electron spin resonance study of phosphorus-nitroxides from 1,3-additions of silicon-phosphorus reagents to nitrones
✍ Scribed by Dr D. Lawrence Haire; Edward G. Janzen; Valerie J. Robinson; Ivan Hrvoic
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 179 KB
- Volume
- 42
- Category
- Article
- ISSN
- 0749-1581
- DOI
- 10.1002/mrc.1436
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✦ Synopsis
Abstract
This article explores a new, convenient route to β‐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. α‐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 α‐phosphityl‐ or α‐phosphinyl‐O‐silylhydroxylamines. Acidic hydrolysis provides the corresponding hydroxylamines that are easily oxidized to the title β‐phosphorus‐nitroxides. ESR spectroscopic analysis revealed some very large β‐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. Copyright © 2004 John Wiley & Sons, Ltd.