Phosphorus oxybromide → 4-Bromo-2-(2,6-dichlorophenyl)-7-methoxy-2H-pyrazolo[4,3-c]pyridine

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Reaction Steps

To a cooled (0° C.) solution of 2-(2,6-dichlorophenyl)-7-methoxy-2H-pyrazolo[4,3-c]pyridine 5-oxide (1.3 g, 4.2 mmol) in DCE (30 mL) under nitrogen was added phosphorous oxybromide (2.4 g, 8.4 mmol). The reaction mixture was stirred for 30 minutes, warmed to room temperature, and stirred for a further 4 hours. Further phosphorous oxybromide (1.8 g, 6.3 mmol) was added and the reaction mixture was stirred for a further 16 hours. The temperature was raised to 80° C. and stirred for 2 hours. The resultant mixture was cooled, quenched with sodium carbonate (sat. aq.) and the layers were partitioned. The organic layer was washed with brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The resultant residue was purified by silica gel flash chromatography (30-40% ethyl acetate in cyclohexane) to afford the title compound as a white solid (143 mg, 9% yield). LCMS (Method D): RT=3.52 min, m/z: 372 [M+H+].

Provenance & Evidence