The base-induced cascade rearrangement of 4-acetylamino-3-arylazo-1,2,5-oxadiazole 2-oxides (furoxans) into 4-acetylamino-2-aryl-5-nitro-2H-1,2,3-triazoles

4-Acetylamino-3-arylazo-1,2,5-oxadiazole 2-oxides (furoxans) undergo two successive (cascade) mononuclear heterocyclic rearrangements in an aqueous basic medium with the formation of 4-acetylamino-2-aryl-5-nitro-2H-1,2,3-triazoles.