6-Chloro-1-methyl-1H-pyrazolo[3,4-d]pyrimidin-4(7H)-one

98141-42-5

5334-35-0

General procedure for the synthesis of 6-chloro-1-methyl-1H-pyrazolo[3,4-d]pyrimidin-4(7H)-one from 4,6-dichloro-1-methyl-1H-pyrazolo[3,4-d]pyrimidinium: In a sealed reaction vessel, 4,6-dichloro-1-methyl-1H-pyrazolo[3,4-d]pyrimidinium (2.2 g, 10.8 mmol) and 2 M sodium hydroxide aqueous solution (50 mL). After sealing the vessel, the reaction mixture was heated to 70 °C and stirred for 30 min under the protection of a blast shield. Upon completion of the reaction, the clarified reaction solution was diluted with water and the pH was adjusted to 6-7 with 2M aqueous hydrochloric acid solution, followed by vacuum concentration. The precipitated solid was collected by filtration and washed with ethanol (~300 mL). The filtrate was concentrated in vacuum and adsorbed on Celite and purified by fast chromatography (using a 40 g silica gel column with 1-10% methanol:dichloromethane as eluent) to afford 6-chloro-1-methyl-1,5-dihydro-pyrazolo[3,4-d]pyrimidin-4-one as a white solid (1.45 g, 72.5% yield). The product was confirmed by 1H NMR (300 MHz, DMSO-d6): δ 3.87 (s, 3H), 8.06 (s, 1H), 13.18 (br.s., 1H).Results of the LC-MS analysis: calculated value C6H6ClN4 [(M+H)+] 185, measured value 184.9.