Studies on Stable Free Radicals. II. Reactivity of Stable Nitroxide Radicals and NMR Spectra of Reaction Products

Abstract

We have isolated coupled products of such stable free radicals as 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (II), cyclohexane-1-spiro-2′-(4′-oxoimidazolidine-l′-oxyl)-5′-spiro-l″-cyclohexane (IV) and 2,2,6,6-tetramethyl-4-oxopiperidine-1-thiyl derived from bis-[2,2,6,6-tetramethyl-4-oxopiperidyl-(1)]disulfide (VII) with a C-radical derived from α,α′-azo-bis(isobutyronitrile). The reactive site in these stable free radicals was studied from the structure of the coupled products. The homolysis of the disulfide (VII) appeared to be accelerated by an attack of the C-radical, 1-methyl-1-cyanoethyl. The NMR spectra of the products suggested a slow inversion of the nitrogen atom in piperidine derivatives.

Imidazolidinone Nitroxide-Mediated Polymerization

“…Nitroxide/Alkoxyamine Synthesis. The parent nitroxides 4a and 5a have been previously described in a series of papers by Murayama et al − However, their use in nitroxide-mediated polymerization has not previously been described.…”

Radiation-induced binding of 2,2,6,6-tetramethyl-1,4-piperidone-N-oxyl to thymidine in oxygen-free aqueous solutions. Isolation and characterization of the adducts

“…4). It should be noted that the addition of the TAN molecule to the carbon C(6) is less stereoselective than to carbon C(5 probably due to the presence of the two bulky substituents on radicals may generate either hydroxylamine derivatives (25) or the carbon C(5) preventing the preferential trans radical N-oxide type compounds (26). Chemical transformations of the addition which is usually observed with respect to the 5-or adducts 2-9 provided the most convincing evidence that the 6-monosubstituted carbon within the pyrimidine ring (24).…”

Antioxidant action of a lipophilic nitroxyl radical, cyclohexane‐1‐spiro‐2′‐(4′‐oxyimidazolidine‐1′‐oxyl)‐5′‐spiro‐1″‐cyclohexane, against lipid peroxidation under hypoxic conditions

“…Nitroxyl radical I was prepared as reported previously (10). Briefly, 1-amino-1-cyanocyclohexane and cyclohexanone were stirred in a methanol solution at room temperature, after which an appropriate amount of 40% NaOH solution was added to this solution.…”