Imidazolidine nitroxides, oxidation

Various a-fluorinated imidazolidine nitroxides have been obtained126 127 from 3-imida-zoline-3-oxide, and other five-membered N-oxide derivatives by reactions with xenon difluoride in CH2C12 (Scheme 53). 

Loss of the EPR signal during Fe(CN)g (hcf) oxidation of imidazolidine nitroxides having a hydrogen at position 4 of the heterocycle (HIMD) supports the assumption that the HIMD fragmentation is facilitated by proton abstraction from the position 4 of the oxoammonium cation formed as a result of the initial one-electron HIMD oxidation. ... 

Recently Keana and co-workers (1978) suggested a new method of synthesizing imidazolidine nitroxides. According to this method, condensation of 2,3-diamino-2,3-dimethylbutane with a ketone in the presence p-toluenesulfonic acid leads to imidazolidine 16. Oxidation of the latter with m-chloroperbenzoic acid gives the corresponding nitroxide 17, with a... 

Hence, polarization of the C=N bond of imidazolinium nitroxyl salts provides easy and unique addition of nucleophilic agents (i.e., cyanide ion, Grignard reagent, and hydride ion) with the formation of imidazolidine nitroxides, whereas the radical center participates when, in reactions of this type, as in the case of 3-imidazoline-3-oxides, the functional group becomes transformed and the heterocycle is opened. 

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