Synthesis of 3-Imidazoline-3-oxide Derivatives

Condensation of 1,2-hydroxylaminooximes with hexadeuteroacetone diethylketal leads to compounds 6 a,e in which deuterium is substituted not only for the protons of methyl groups in position 2, but also for the 

Oxidation of 1-hydroxy derivatives (6a-g) with lead dioxide in nonpolar organic solvents leads smoothly to nitroxides, namely 2,2,5,5-tetra-alkyl-3-imidazoline-3-oxide-l-oxyls (7a-g) (Volodarsky and Kutikova, 1971). In the crystalline state radicals 7 can be stored for a long time without decomposition. Both radical precursors 6 and the radicals themselves enter into various substitution, condensation, and other reactions. 

An alternative method of synthesizing 3-imidazoline-3-oxide nitroxides is oxidation with hydrogen peroxide of 2,2,5,5,-tetraalkyl-3-imidaz-oline-3-oxides (8) containing a sterically hindered secondary amino group (Martin and Volodarsky, 1979). Compounds 8 are derived from a-aminooximes generated from olefinic nitrosochlorides (Michael and 

Carlson, 1939 Murman, 1957) and then reacted with ketones in the presence of catalytic quantities of acids (Volodarsky et a/., 1977). In this case it is possible to introduce various alkyl groups into position 2 of the imidazoline cycle and synthesize spiro derivatives. 

3-Imidazoline-3-oxide nitroxides (7a,c) can also be derived by oxidation of 1,2-iV-isopropylhydroxylaminooximes with excess lead dioxide 

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