Phosphorus oxychloride → 4-Chloro-2-(2,6-dichloro-4-nitrophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine

Participants

Reaction Conditions

Reaction Steps

2-(2,6-Dichloro-4-nitrophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine 5-oxide (4.20 g, 12.24 mmol) was suspended in DCE (60 mL), under an atmosphere of nitrogen and phosphorus oxychloride (3.61 mL, 39.2 mmol) was added. The reaction mixture was heated at 70° C. for 95 minutes. The resultant mixture was cooled to room temperature and was carefully quenched by the addition of 10% aqueous sodium carbonate solution. The layers were separated and the aqueous layer was extracted with DCM (×4). The combined organic layers were filtered to remove insoluble solids, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel flash chromatography (0-50% ethyl acetate in cyclohexane) to afford the title compound as a pale yellow solid (1.78 g, 40% yield). 1H NMR (300 MHz, CDCl3): δ 8.43 (s, 2H), 8.37 (d, J=2.2 Hz, 1H), 8.03 (d, J=3.0 Hz, 1H).

Provenance & Evidence