| Abstract: | The reaction of 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydro-1,2,4-triazolo4,3-a]quinoxaline 6 with 4-ethoxycarbonyl-1-methyl-1H-pyrazole-5-diazonium chloride or 4-cyano-1,3-dimethyl-1H-pyrazole-5-diazonium chloride gave 7-chloro-4-α-(4-ethoxycarbonyl-1-methyl-1H-pyrazol-5-ylhydrazono)-ethoxycarbonylmethyl]-1,2,4-triazolo4,3-a]quinoxaline 8a or 7-chloro-4-α-(4-cyano-1,3-dimethyl-1H-pyrazol-5-ylhydrazono)ethoxycarbonylmethyl]-1,2,4-triazolo4,3-a]quinoxaline 8b , respectively, while the reaction of 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydrotetrazolo1,5-a]quinoxaline 7 with 4-ethoxycarbonyl-1-methyl-1H-pyrazole-5-diazonium chloride or 4-cyano-1,3-dimethyl-1H-pyrazole-5-diazomum chloride provided 7-chloro-4-α-(4-ethoxycarbonyl-1-methyl-1H-pyrazol-5-ylhydrazono)ethoxycarbonylmethyl]tetrazolo1,5-a]quinoxaline 9a or 7-chloro-4-α-(4-cyano-1,3-dimethyl-1H-pyrazol-5-ylhydrazono)ethoxycarbonylmethyl]tetrazolo1,5-a]quinoxaline 9b , respectively. Compounds 8a,b and 9a,b showed the tautomeric equilibria between the hydrazone imine C and diazenyl enamine D forms in dimethyl sulfoxide and/or trifluoroacetic acid, and the effects of solvent and temperature on the tautomer ratios of C to D were studied by the nmr measurements in a series of mixed trifluoroacetic acid/dimethyl sulfoxide media (compounds 8a,b and 9a,b ) and at various temperatures (compounds 8a,b ). |
