Quaternary Immonium Salts of Imidazoline Nitroxides

Still greater stability in strong acids is displayed by such nitroxides as quaternary immonium salts 24. These salts are formed in quatemization of imidazoline-1-oxyls 13 with dimethyl sulfate (Volodarsky et al, 1979). They are stable, yellow, high-melting crystalline products, with an ESR spectrum in the form of a triplet with 14.0 Oe. Salts 24 are soluble in water, stable in aqueous solutions, and, when treated with 57% perchloric 

By analogy with the formation of enamines in the case of neutralization of immonium salts (Cook, 1969), neutralization of imidazolinium salts 24a,b leads to paramagnetic heterocyclic enamines 4-methylidene- and 4-ethylidene-2,2,3,5,5-pentamethylimidazolidine-1 -oxy Is (28a,b). Com- 

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