A FACILE SYNTHESIS OF NOVEL TRIAZOLOQUINOXALINONES AND TRIAZINOQUINOXALINONES

A series of 1‐aryl‐s‐triazolo[4,3‐a]quinoxalin‐4‐ones, 3, were synthesized via the pyrolysis of the corresponding hydrazones, 6. Thus, the cyclodehydrogenation occurred by refluxing them in an inert solvent (e.g. ethylene glycol) to give the triazoloquinoxalin‐4‐ones in a satisfactory yield. Using DMSO as a solvent for the above transformation afforded as a minor by‐product an S‐ylid. In contrast to earlier findings, annelation of a six‐membered ring was successful and achieved through the pyrolysis of the pyruvate hydrazones derived of the quinoxalin‐4‐ones at −230° to give the as‐triazino[4,3‐a]quinoxalin‐5‐ones, 4. The reaction of 5 with acetylacetone afforded 3‐(3′,5′‐dimethylpyrazol‐1‐yl)‐2(1H)‐quinoxalinone, 10. The structural assignments for the new compounds were based on their elemental analysis and spectroscopic data as well as an independent synthesis. Copyright © 1990 Journal of Heterocyclic Chemistry