Sodium Sulfate → 2-(2,6-Dichloro-4-nitrophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine 5-oxide

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Reaction Conditions

Reaction Steps

2-(2,6-Dichloro-4-nitrophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine (4.78 g, 14.62 mmol) was dissolved in DCM (90 mL) and a solution of meta-chloroperbenzoic acid (3.78 g, 21.93 mmol) in DCM (60 mL, which had been pre-dried over anhydrous sodium sulfate and passed through a phase separator), was added at 0° C. The reaction mixture was stirred at 0° C. for 1 hour and then at room temperature for 4 hours. Another portion of meta-chloroperbenzoic acid (1.26 g, 7.30 mmol) in DCM (20 mL, dried as above) was added and the reaction mixture was stirred for a further 1.25 hour at room temperature. The resultant mixture was sequentially washed with saturated aqueous sodium thiosulfate solution, saturated aqueous sodium bicarbonate solution and brine. The combined aqueous extracts were further extracted with DCM and the combined organic layers were dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was triturated with diethyl ether (×3) and the solid was collected by filtration and dried under reduced pressure to afford the title compound as a pale yellow solid (4.20 g, 84% yield). 1H NMR (300 MHz, CDCl3): δ 8.64 (d, J=1.4 Hz, 1H), 8.42 (s, 2H), 8.20 (d, J=2.3 Hz, 1H), 8.02 (dd, J=5.4, 1.4 Hz, 1H).

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