1.2.5- Selenadiazolo 3,4-/1 quinolines oxidation

The nitration of l,2,5-selenadiazolo[3,4-/] quinoline 77 with benzoyl nitrate affords the 8-nitro derivative 78, whereas methylation with methyl iodide or methyl sulfate afforded the corresponding 6-pyridinium methiodide 79 or methosulfate 80, respectively (Scheme 29). The pyridinium salt 80 was submitted to oxidation with potassium hexacyanoferrate and provided 7-oxo-6,7-dihydro derivative 81 or, by reaction of pyridinium salt 79 with phenylmagnesium bromide, the 7-phenyl-6,7-dihydro derivative 82. Nucleophilic substitution of the methiodide 79 with potassium cyanide resulted in the formation of 9-cyano-6,9-dihydroderivative 83, which can be oxidized by iodine to 9-cyano-l,2,5-selenadiazolo [3,4-/]quinoline methiodide 84. All the reactions proceeded in moderate yields (81IJC648). 

Selenium dioxide oxidation of 7,8-dihydro-5(6//)-quinolinone semicarbazone gave, in addition to the expected 4,5-dihydro selenadiazoloquinoline 95 (analogous to sulfur derivative 76), the oxidized l,2,3-selenadiazolo[4,5-/]quinoline 96, which, when heated to 210°C for 30 min, gave the dimeric [l,4]diselenino [2,3-/ 5,6-/ ]diquinoline (95JHC177). 

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