Synthesis of mesoionic triazolo[4,3-a]quinoxalines

The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 1 or 6-chloro-2-(1-methylhydrazino)-quinoxaline 5 with phenyl isothiocyanate under reflux in N,N-dimethylformamide gave 7-chloro-3-methyl-1,2,4-triazolo4,3-a]quinoxalin-3-ium-1-thioate 4 , which was also obtained by refluxing of 6-chloro-2-1-methyl-2-(N-phenylthiocarbamoyl)hydrazino]quinoxaline 4-oxide 2b or 6-chloro-2-1-methyl-2-(N-phenylthiocarbamoyl)hydrazino]quinoxaline 6 in N,N-dimethylformamide.