The reaction of [3-oxonitrones --imidazoline derivatives --with hydroxylamine, phenylhydrazine, and semicarbazide takes place at the carbonyl group with retention of the nitrone group. Stable nitroxyl radicals --spiroimidazoisoxazole derivatives -are formed in the oxidation of fJhydroximinonitrones. The recyclization of the/3-oxonitrones, which takes place in an acidic medium, as well as by the action of hydrazine and thiosemicarbazide, leads, respectively, to pyrroline and pyrazole derivatives.
In a previous study of the properties of 2-substituted 5,5-dimethyl-4-oxo-l-pyrroline 1-oxides I --cyclic/3oxonitrones --it was shown that their reaction with nucleophilie reagents may take place either at the nitrone group or at the carbonyl group [1]. In the present research we examined the reaction of ~-oxo nitrones, in which the oxonitrone group is included in part in the composition of the imidazoline (II) and pyrroline (III) heterorings, with nueleophilic reagents.
Compounds II were obtained by condensation of imidazoline IVa with esters in the presence of phenyUithium [2]. It should be noted that, under similar conditions, the reaction of imidazoline IVb with ethyl benzoate leads to opening of the imidazoline heteroring to give acyclic V, which, according to the PMR data, exists in solution in the form of a mixture of two tautomeric forms.