5-BroMo-1H-pyrazolo[4,3-b]pyridine

Synthesis

22282-96-8

110-46-3

1227628-78-5

To a stirred chloroform solution of 6-bromo-2-methyl-3-nitropyridine (5 g, 26.73 mmol) was added potassium acetate (3.14 g, 32.08 mmol) and acetic anhydride (10.9 g, 106 mmol) sequentially at 10 °C. The reaction mixture was stirred at 65 °C for 2 hours. The reaction process was monitored by thin layer chromatography (TLC). Upon completion of the reaction, the mixture was cooled to room temperature, followed by the addition of isoamyl nitrite (3.75 g, 32.06 mmol) dropwise over 15 minutes and 18-crown-6 (0.7 g, 2.67 mmol). The reaction mixture was continued to be stirred at 65 °C for 16 h. The progress of the reaction was likewise monitored by TLC. At the end of the reaction, it was cooled to room temperature and 120 mL of a mixture of methanol and water (1:1 volume ratio) was added to the reaction mixture, followed by the addition of potassium carbonate (34.48 g, 24.99 mmol) and potassium hydroxide (4.2 g, 74.97 mmol). The mixture was stirred at room temperature for 3 hours. After completion of the reaction, the reaction mixture was diluted with ethyl acetate and the organic layer was separated and washed sequentially with water and brine. The organic layer was dried over anhydrous sodium sulfate and concentrated under reduced pressure to give 5-bromo-1H-pyrazolo[4,3-b]pyridine (5 g) as an off-white solid.

References