Single electron transfer, oximes

Hydrogenated isoxazole derivatives were obtained by single electron transfer (SET) cyclization of /9,y-unsaturated oximes , by thermal [4- -2] cycloaddition of aldox-imes or ketoximes to conventional dienophiles or isomerization/cyclization of an ortho halogeno or nitro-substituted amidoximes. Preparation of 1,4-disubstituted 3-hydroximino-2-nitro-l-butenes and their oxidative cyclization to 4-nitroisoxazoles are reported " . Synthesis of fluorine-containing substituted isoxazolidines as well as isoxazoles by ultrasonic methods has been also described. 

A novel synthesis of 5,6-dihydro-4//-1,2-oxazines (20) is presented via the photo-induced cyclization of y. d-unsaturated oximes (21) see Scheme 4. Irradiation of (21) in the presence of 9,10-dicyanoanthraccnc (DCA) led to the heterocycle (20) only. The proposed mechanism proceeds via the radical cation (22), generated by single-electron transfer (SET) from the oxime (21) to the excited sensitizer (DCA. Cyclization of (22) affords the oxazine (20) after proton transfer to the DCA radical anion (DCA ) and H abstraction.61... 

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