13877-55-9

923283-63-0

3473-63-0

13877-55-9

GENERAL STEPS: Formamidine acetate (40.3 mmol, 4.2 g) was added to a mixed solution of Hunig base (40 mL) and n-butanol (n-BuOH, 40 mL) containing 1-tert-butyl 3-methyl 4-amino-1H-pyrazole-1,3-dicarboxylic acid (26, 8.85 g, 36.7 mmol). The reaction mixture was heated with stirring at 110 °C for 1 hour. After completion of the reaction, it was cooled to room temperature and the precipitated solid product was collected. The solid was washed with dichloromethane and then dried under reduced pressure to afford 7-hydroxypyrazolo[4,3-D]pyrimidine (27, 4.46 g, 89% yield). The structure of the product was confirmed by electrospray mass spectrometry (ES(+)MS), m/e = 137.