5-Chloro-1H-pyrazolo[4,3-d]pyrimidine

633328-97-9

633328-98-0

General procedure for the synthesis of 5-chloro-1H-pyrazolo[4,3-d]pyrimidin-1-yl from 1-(5-chloro-1H-pyrazolo[4,3-d]pyrimidin-1-yl)ethanone: To a stirred solution of 1-(5-chloro-1H-pyrazolo[4,3-d]pyrimidin-1-yl)ethanone (1.5 g, 7.65 mmol) in tetrahydrofuran (THF, 15 mL), was added an 8% hydrochloric acid aqueous solution (14.46 mL). The reaction mixture was refluxed at 50 °C for 30 min. After completion of the reaction, it was cooled to 25 °C and extracted with ethyl acetate (EtOAc, 2 × 50 mL). The organic layers were combined, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to afford 5-chloro-1H-pyrazolo[4,3-d]pyrimidine as an off-white solid (1.1 g, 93% yield). Mass spectrum (ESI): m/z = 153.0 [M-H]-.