2-(Methylthio)pyrazolo[1,5-a][1,3,5]triazin-4(3H)-one

34682-99-0

74-88-4

54346-18-8

General procedure for the synthesis of 2-(methylthio)pyrazolo[1,5-α][1,3,5]triazin-4(1H)-one from 2-thio-2,3-dihydropyrazolo[1,5-a][1,3,5]triazin-4(1H)-one (7.99 g, 0.05 mol) and iodomethane (3 mL, 0.05 mol): firstly, 2-thio-2,3-dihydro pyrazolo[1,5-a][1,3,5]triazin-4(1H)-one was first suspended in a solvent mixture of ethanol (200 mL) and 2M aqueous sodium hydroxide (48 mL). Since the mixture was too viscous, it needed to be diluted by adding about 10 mL of water. The mixture was then cooled to 0°C and iodomethane was slowly added dropwise. During the dropwise addition, the mixture briefly dissolved and then began to form a white precipitate. The reaction system was gradually warmed to room temperature with continuous stirring for 3 hours, after which it was left overnight. Upon completion of the reaction, it was cooled again to 0 °C, 2N aqueous sulfuric acid solution (58 mL) was added and stirred for 1 hour. The precipitate was collected by filtration, washed sequentially with water (200 mL) and cyclohexane (50 mL), and finally dried in a vacuum oven to afford the target product 2-(methylthio)pyrazolo[1,5-α][1,3,5]triazin-4(3H)-one (6.85 g, 79% yield) as a white solid. The product was confirmed by NMR hydrogen spectroscopy (DMSO-d6): δH 12.94 (s, 1H), 7.96 (d, J=1.9Hz, 1H), 6.34 (d, J=1.9Hz, 1H), 2.53 (s, 3H).