N-Oxide radicals

C. Radicals from Oxygenated Azines 1. Azine N-Oxide Radicals... 

Janzen and Happ generated a series of 2- and 4-acylated pyridine N-oxide radical-anions by the autoxidation of corresponding alkyl or hydroxyalkyl precursors in mixtures of DMSO or DMF with t-butanol containing potassium f-butoxide.355 The computational approach of these workers to the spin distribution problem was rather different from that of the Japanese group,351 but their results and conclusions were essentially concordant. 

The theoretical account of the electronic absorption spectra of pyridine N-oxide radicals has also attracted interest.79,356... 

Beckmann rearrangement of 2,2,6,6-tetramethyl-4-piperidone oxime with thionyl chloride followed by oxidation gave the stable free radical 159.167 Beckmann rearrangement of the N-oxide radical of the piperidone oxime gave the same free radical (159).168... 

Important work on the nature of the pyridine N-oxide radical cation has been published. This was stimulated by consideration of the possible role of such a species in Gif chemistry.69>70,71... 

Peroxybenzoic acid N-Oxide radicals from amines... 

The free energies of reaction and activation have been calculated by the semiempirical molecular orbital method for the oxidation of ammonia and mono-, di- and trimethylamine by singlet and triplet oxygen atoms as models for oxidation by cytochrome P-450 [56]. For the non-radical oxidation (closed-shell path), the results indicate a two-step addition-rearrangement mechanism leading to both N-hydroxy and N-methoxy products via N-oxide intermediates. In the triplet path both a-C- and N-oxidation are competitive. N-oxidation via an addition mechanism seems to be favored over the H-abstraction mechanism, but no stable N-oxide radical intermediate is found on the triplet surface. 

A soln. of 85%-m-chloroperoxybenzoic acid in methylene diloride added to a stirred ice-cooled soln. of 5-norbornen-2-ol in the same solvent, after 2 hrs. treated with a soln. of 2,2,6,6-tetramethylpiperidine hydrochloride in methylene chloride followed by additional m-chloroperoxybenzoic acid soln., and the product isolated after 1.5 hrs. exo-5,6-epoxy-2-norbornanone. Y 86%. J. A. Celia, J. A. Celia, J. A. Kelley, and E. F. Kenehan, J. Org. Chem. 40, 1860 (1975) oxidation of alcohols with N-oxide radicals cf. B. Ganem, ibid. 40, 1998 ketones from sec. alcohols with m-chloroperoxybenzoic acid/HCl cf. J. A. Celia, J. P. McGrath, and S. L. Regen, Tetrah. Let. 1975, 4115 review of N-oxide radicals s. H. G. Aurich and W. Weiss, Topics Curr. Chem. 59, 65 (1975). 

Nitroxyls s. N-Oxide radicals Norbomadiene s. Chromium tetracarbonyl-norbornadiene Norrish type I cleavage 20, 534s31... 

Potassium hexacyanoferrate(III) N-Oxide radicals from hydroxylamines... 

Xep2 added to a soln. of l-nitroso-2,2,5,5-tetramethyl-4-phenyl-3-imidazoline 3-oxide in methylene chloride in a Teflon-type vessel, and stirred at 20-25° for 20 h 3-nitroso-2,2,4,4-tetramethyl-5-phenyl-5-fluoroimidazolidine 1-oxyl. Y 70%. F.e. and 1,1-difluoro-N-oxide radicals s. I.A. Grigorev et al., Izv. Akad. Nauk SSSR Ser. Khim. 1989, 933-7. 

Sodium sulfide/irradiation Amines from N-oxide radicals... 

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