General procedure for the synthesis of 4,6-dichloro-3-methyl-1H-pyrazolo[4,3-c]pyridine from 1-(2,4,6-trichloropyridin-3-yl)ethanone: a mixture of intermediate 4A (3.55 g, 15.8 mmol) with 35% hydrazine aqueous solution (35 mL) in ethanol (35 mL) was stirred for 3.5 hours at room temperature. After completion of the reaction, the reaction mixture was poured into ice water and extracted with ethyl acetate. The organic phase was washed with saturated saline, dried over anhydrous sodium sulfate and concentrated. The residue was purified by fast column chromatography on silica gel with gasoline-ethyl acetate (3:1, v/v) as eluent to give an off-white solid product (1.71 g, 54% yield). The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 2.64 (s, 3H), 7.63 (s, 1H).
![4,6-dichloro-3-Methyl-1H-pyrazolo[4,3-c]pyridine](/CAS/GIF/120422-90-4.gif)