1,2,3-Triazolo[1,5-a]- (II) and 1,2,4-triazolo[4,3-a]quinoxaline 5-oxide (III) react with the carbanions of β-diketones and β-keto esters to give enaminones in the same way as their tetrazolo analogue. The difference in mechanism of reactions of these N-oxides with carbanions of 3-alkylpentane-2,4-dione and ethyl methyl acetoacetate giving aziridinopolyazoloquinoxalines and ethyl 2-(polyazoloquinoxalin-4-yl)propanoates, respectively, is discussed. It was shown that the reaction with carbanion including the aziridine ring closure proceeds with 3,4-dihydro-3-oxoquinoxaline-1-oxide as well.