Synthesis of 2,2,4,5,5-Pentasubstituted-3-imidazolines

For generating 3-imidazoline derivatives containing no N-oxide oxygen, 1,2-hydroxylaminoketones were employed, which are formed in the acidic hydrolysis of 1,2-hydroxylaminooximes (Volodarsky and Sevastyanova, 1971), The interaction of 1,2-hydroxylaminoketones with ketones and ammonia under mild conditions (in some cases at 20°C) leads to the formation of l-hydroxy-4-aryl- and l-hydroxy-4-alkyl-2,2,5,5-tetraalkyl-3-imidazolines (12) (Sevastyanova and Volodarsky, 1972 Volodarsky and Sevastyanova, 1973). Compounds 12 are colorless crystalline substances that have lower melting points and are more readily soluble in organic solvents than 3-imidazoline-3-oxides 6. When stored or recrystallized in air, they become partially oxidized to radicals. Oxi- 

The interaction of 1,2-hydroxylaminoketone with triacetonamine and ammonia gives a 1-hydroxy-3-imidazoline spiro derivative 12. Oxidation of the latter with Pb02 yields monoradical 14, and subsequent treatment 

a number of new nitroxides of 3-imidazoline derivatives were synthesized on the basis of 1,2-hydroxylaminoketones. 

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 

Reduction of the radical center to the hydroxylamino group, its shielding and subsequent oxidation of the amino group with m-chloroper-benzoic acid, and deshielding produced dinitroxide 18, in which the nitroxide groups are separated from each other by only one carbon atom. 

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