Abstract: | The reactions of 3-methoxycarbonylmethylene-2-oxo-1,2,3,4-tetrahydroquinoxaline 1 with aryl diazonium salts gave 3-(α-aryldiazenylmethoxycarbonylmethylene)-2-oxo-1,2,3,4-tetrahydroquinoxalines 2a-c , whose reactions with hydrazine hydrate afforded 3-(α-aryldiazenylhydrazinocarbonylmethylene)-2-oxo-1,2,3,4-tetrahydroquinoxalines 3a-c . The reactions of 3a-c with nitrous acid resulted in the Curtius rearrangement to provide the 1-aryl-3-quinoxalinyl-1,2,4-triazol-5-ones 4a-c. |