The reaction of 3-nitropyrazole and 3(5)-nitro-1,2,4-triazole with t-BuNHMgBr gives the corresponding asymmetrical diazene oxides. Furthermore, 3(5)-(1,1-dimethylethyl)azoxy-1,2,4-triazole was also synthesized by the reaction of 1-trimethylsilyl-3(5)-nitro-1,2,4-triazole with t-BuNHLi.