Aminoguanidine bicarbonate (23.5 g, 172 mmol) was added in batches to a mixture of ethanoic acid (26.2 g, 345 mmol) and water (10 mL) over a period of 0.1 hours. During the addition, the reaction mixture was gently heated to maintain the internal temperature at 25 °C. Subsequently, concentrated nitric acid (1.0 mL) was added slowly and dropwise to the reaction system, and then the reaction mixture was heated to an internal temperature of 104-108 °C over 22 hours. Upon completion of the reaction, the heating was stopped and the solution was allowed to cool naturally with stirring. The slurry cooled to 10 °C was continued to be stirred for 2 h. Subsequently, it was filtered and the filter cake was washed with ethanol (EtOH). The resulting solid was dried overnight under vacuum to afford the target product (5-amino-1H-1,2,4-triazol-3-yl) methanol ethanolate (Product 88a, 29.5 g, 85% yield). Mass spectrometry analysis: calculated value (M + H)+ = 115, measured value (M + H)+ = 115.
