4-oxo-2, 2, 6, 6-tetramethylpiperidinyl-1-oxy radical (TEMPO), a nitroxide, oxidized 4-substituted Hantzsch 1,4-dihydropyridines (DHP) under UV irradiation in CH3CN to give aromatic products in good yields. A possible mechanism for the oxidation was suggested.

Photochemical or thermal decomposition of azo-compounds (such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, dialkyl peroxides (such as tert-butyl peroxide and diacyl peroxides (such as benzoyl peroxide) in anaerobic nitric oxide (NO)-saturated dimethylsulfoxide (DMSO) or aqueous solutions yielded nitroxides. Well-characterized electron paramagnetic resonance spectra of nitroxides revealed that NO was favorable for reacting with carbon-centered and less stereoinhibited transient alkyl radicals, giving kinds of nitrosoalkane, typically nitrosomethane, which act sequentially as C-nitroso compounds to trap transient radicals present in solution, yielding spin-trapping adducts, i.e. nitroxides. Radicals, including sulfinyl radicals from UV-irradiated DMSO, were trapped by the in situ formed CH3NO. O-centered radicals could not add to the freshly formed C-nitroso compounds. Possible mechanisms are suggested.

Epoxide rings of 2,3-epoxy phenyl ketones were cleaved by nitric oxide, affording regioselectively the C-3 ring-opened products, erythro-a-hydroxyl nitrates (2), in a highly syn-selective manner (isolated yield of the erythro products up to 91%). Products were identified by NMR, MS, and X-ray crystallography. The reaction is assumed to be initiated by NO2, unlike a nucleophilic attack.

Stable aminoxyls and an iminoxyl were observed by spin trapping and EPR techniques during the nitrationof coumarins containing a hydroxy group by nitric oxide. The trapped free radicals are deduced to be the resonance stabilized phenoxy-like radicals. The mechanisms for the nitrations are suggested.

Thermal or photolytic reactions of bioactive S-nitrosothiols and related thiols in the presence of radical generators in deaerated DMSO or aqueous solutions under argon or saturated with nitric oxide (NO) produced nitroxides and an oxyaminyl radical, which were well characterized by EPR spectra. Nitroxides containing a thiyl substituent were obtained. Possible mechanisms are proposed. Bioactive S-nitrosothiols such as S-nitrosoglutathione, S-nitroso-N-acetylpenicillamine and related thiols such as glutathione and N-acetylpenicillamine were used for the investigation. Radical generators utilized as transient radical sources were 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylpropionamidine) dihydrochloride, tert-butyl peroxide and benzoyl peroxide.