General procedure for the synthesis of 3-amino-1H-1,2,4-triazole-5-carboxylic acid from ethyl 2-(2-carbamoyliminohydrazide)-2-oxoacetate: ethyl 2-(2-carbamoyliminohydrazide)-2-oxoacetate (2 g, 35.60 mmol) was dissolved in water (100 ml) and the reaction was stirred for 12 hours at 100 °C. After completion of the reaction, the mixture was concentrated under vacuum to give a residue. The residue was dissolved in water (10 ml) and purified by precipitation to afford 5-amino-1H-1,2,4-triazole-3-carboxylic acid as a white solid (1.1 g, 63% yield). The product was confirmed by LC/MS (electrospray ionization, m/z) analysis: [M + H]+ 129.0.
