HDH-PHARMA 26173

134031-24-6

871836-51-0

General procedure for the synthesis of 4-chloro-1H-pyrazolo[4,3-c]pyridine using 2,4-dichloronicotinaldehyde as starting material: intermediate 1 (1.7 g, 9.7 mmol) was dissolved in dimethoxyethane (12 ml) at room temperature, followed by addition of hydrazine monohydrate (1.2 ml, 38.6 mmol). The reaction mixture was stirred at 75°C overnight. Upon completion of the reaction, the mixture was concentrated to dryness and the resulting crude product was purified by fast chromatography using 20% to 100% ethyl acetate/petroleum ether gradient elution to afford the target product, 4-chloro-1H-pyrazolo[4,3-c]pyridine, as a white solid (0.82 g, 56% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 7.60 (d, J = 6.9 Hz, 1H), 8.14 (d, J = 6.0 Hz, 1H), 8.32 (s, 1H); mass spectra (ES + APCI)+: m/z 154 [M + H]+.