923283-54-9

3473-63-0

314021-93-7

GENERAL STEPS: To a mixture of 4-amino-1-methyl-1H-pyrazole-5-carboxylic acid methyl ester (0.92 g, 5.9 mmol) dissolved in 5 mL of a mixture of N,N-diisopropylethylamine (Hunig base) and 5 mL of n-butanol was added formamidine acetate (0.68 g, 6.5 mmol). The reaction mixture was heated to 110 °C and stirred for 1 hour. After completion of the reaction, it was cooled to room temperature, the white precipitate was collected by filtration and washed with ether. The resulting white solid was dried under reduced pressure to afford 1-methyl-1H-pyrazolo[4,3-d]pyrimidin-7-ol (0.83 g, 94% yield). The product was characterized by 1H NMR (d6-DMSO): δ 4.33 (s, 3H), 8.50 (s, 1H), 8.80 (s, 1H); electrospray mass spectrometry (ES-MS) showed m/e = 151 ([M + H]+).