General procedure for the synthesis of 2-thio-2,3-dihydropyrazolo[1,5-a][1,3,5]triazin-4(1H)-one from compound (CAS: 34683-00-6): compound 46 (7.2 g) was dissolved in 2N NaOH solution (70 mL) and stirred at room temperature for 1.5 hours. Subsequently, 2N H2SO4 solution (100 mL) was slowly added to the reaction mixture. Upon completion of the reaction, the resulting precipitate was collected by filtration, washed thoroughly with water and then dried under vacuum to afford compound 47 (5.3 g, 100% yield) as a yellow powder. Thin layer chromatography (TLC) analysis showed an Rf value of 0.16 (unfolding agent ratio MeOH/CH2Cl2, 1/9).1H NMR (300 MHz, DMSO-d6) δ 13.42 (s, 1H), 12.70 (s, 1H), 7.86 (d, J = 1.8 Hz, 1H), 5.88 (d, J = 1.8 Hz, 1H).
![2-Thioxo-2,3-dihydropyrazolo[1,5-a][1,3,5]triazin-4(1H)-one](/CAS/GIF/34682-99-0.gif)