4,6-Dichloro-1H-pyrazolo[3,4-d]pyrimidine

Yellow solid

To a solution of 2,4,6-trichloropyrimidine-5-carbaldehyde (19.0 g, 990 mmol) in methanol (300 mL) was added drop-wise a solution of hydrazine monohydrate (4.8 mL) in methanol (80 mL) at 0 °C followed by drop-wise addition of triethylamine (13 mL) in methanol (80 mL) at 0 °C. The mixture was stirred at the same temperature for 30 mm. The solvent was removed, and the residue was purified by flash chromatography to afford 4,6-Dichloro-1H-pyrazolo[3,4-d]pyrimidine (10.3 g, 62 % yield) as a yellow solid. ‘H NMR (CDC13, 400IVIHz): 11.56 (br, 1H), 8.43 (s, 1H). MS m/z 190.68 [M+1].