Reduction Aminium radical ions

Radical cations can be generated by many chemical oxidizing reagents, including Brpnsted and Lewis acids, the halogens, peroxide anions or radical anions, metal ions or oxides, nitrosonium and dioxygenyl ions, stable aminium radical cations, semiconductor surfaces, and suitable zeolites. In principle, it is possible to choose a reagent with a one-electron redox potential sufficient for oxidation-reduction, and a two-electron potential insufficient for oxidation-reduction of the radical ion. 

Amination refers to the reaction of the aminium radical (NH ) and its dialkyl derivatives (R2NH +) with organic substrates, particularly with olefins and aromatics. The aminium radical itself can be generated by the reduction of hydroxylamine O-sulfonic acid with ferrous ion (147) (Minisci and Galli, 1965). Dialkylaminium radicals are generated in several ways, the most common being the reduction of N-chlorodialkylamines by ferrous ion in acidic solution (148) and... 

Sosnovsky and Rawlinson (1972), and Minisci (1975), while work with nitrosamines has been carried out and reviewed by Chow (1973). The reduction of an amine oxide by ferrous ion also gives an aminium radical (Lindsay Smith et al., 1973). Danen and Rickard... 

Wieland, 1907 Wieland and Wecker, 1910). Oxidation was carried out in an inert solvent such as benzene, from which the salt precipitated. The easier and more reliable preparation of perchlorate salts by the iodine-silver perchlorate method (Weitz and Schwechten, 1926, 1927), to which we have referred earlier (p. 168), allowed a much clearer understanding of the nature of triarylaminium ions to be obtained. Isolation of perchlorates permitted chemical studies, and easy reduction to the triarylamine by iodide ion, ferrous ion, etc., was consistent with the cation-radical view that was developed. The name aminium ion was coined by Weitz. Other salts were prepared such as tritolylaminium picrate (by oxidation of the amine with lead dioxide in the presence of picric acid), and it was also recognized that conjugate anions in salts obtained by oxidation with antimony pentachloride, phosphorus pentachloride and ferric chloride had to be complex anions rather than simple anionic radicals. This is a particularly pertinent point in antimony pentachloride oxidations (p. 165). 

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