Studies on Stable Free Radicals. III. Reactions of Stable Nitroxide Radicals with S-Radicals Derived from Benzenethiols and Thiamine

Abstract

The reaction of the extremely stable free radical, 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (I), was carried out with benzenethiols (IV). The formation of diphenyl disulfides (VI), benzenesulfinic acids (VII), and 1-(p-substituted benzenesulfinyl)-2,2,6,6-tetramethyl-4-oxopiperidines (X) from the above reaction shows that the radical (I) can act as a hydrogen-abstracting agent, an oxidizing agent, and a radical scavenger. Possible mechanisms for the coupling reaction of the radical (I) with the S-radicals (V) to give the sulfinamides (X) were discussed. A substituent effect was observed in the formation of the disulfides (VI). The N-oxyl radical (I) and another stable free radical, such as 2,6-di-t-butyl-4-methylphenoxyl radical (XXV), were shown to react with the S-radical (XVII) derived from thiamine (XIV) to give new types of thiamine derivatives, S-(2,2,6,6-tetramethyl-4-oxopiperidino) thiamine (XX) and S-(2,6-di-t-butyl-4-methylphenoxy)thiamine (XXVI) respectively.

A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series

“…The hydroxylamines can be stabilized in acidic media, e.g., upon reduction with alcohol in strongly acidic media [ 23 , 24 ]; however, hydroxylammonium cation formation adds an asymmetric center to the molecule, affording a mixture of diastereomers in variable ratio with superposition of signals or broadening in the NMR spectra [ 25 ]. Some other reactions, such as conversion to alkoxyamines [ 26 ] or reduction to amines with thiols [ 13 , 27 ], never afford a single diamagnetic product with quantitative yield.…”

Electron-Spin Resonance Study of Mainstream and Sidestream Cigarette Smoke: Nature of the Free Radicals in Gas-Phase Smoke and in Cigarette Tar

“…Qualitatively, the isotope effects for aliphatic thiols appear to follow the curve for isotope effect versus heat of reaction (41), indicating that the reaction is a hydrogen-atom transfer. The products of the reaction were not examined, but other workers have reported products that can be rationalized as dimerization and combination products from thiyl and nitroxide radicals (42). Qualitatively, thiophenol appears to have a much smaller isotope effect, suggesting the possibility of a rate-limiting electron-transfer reaction (K. Terauchi and W. H. Davis, this laboratory, unpublished data, 1977).…”

Electron-spin resonance study of mainstream and sidestream cigarette smoke: nature of the free radicals in gas-phase smoke and in cigarette tar.

“…Qualitatively, the isotope effects for aliphatic thiols appear to follow the curve for isotope effect versus heat of reaction (41), indicating that the reaction is a hydrogen-atom transfer. The products of the reaction were not examined, but other workers have reported products that can be rationalized as dimerization and combination products from thiyl and nitroxide radicals (42). Qualitatively, thiophenol appears to have a much smaller isotope effect, suggesting the possibility of a rate-limiting electron-transfer reaction (K. Terauchi and W. H. Davis, this laboratory, unpublished data, 1977).…”