Phosphorus oxybromide → 4-Bromo-2-(2,6-dichlorophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine
Reaction equation
[Cl:1][C:2]1[CH:7]=[CH:6][CH:5]=[C:4]([Cl:8])[C:3]=1[N:9]1[CH:19]=[C:12]2[CH:13]=[N+:14]([O-])[CH:15]=[C:16]([F:17])[C:11]2=[N:10]1.P(Br)(Br)([Br:22])=O>ClCCCl>[Br:22][C:13]1[C:12]2=[CH:19][N:9]([C:3]3[C:2]([Cl:1])=[CH:7][CH:6]=[CH:5][C:4]=3[Cl:8])[N:10]=[C:11]2[C:16]([F:17])=[CH:15][N:14]=1Participants
4
Procedure
To a cooled (0° C.) solution of 2-(2,6-dichlorophenyl)-7-fluoro-2H-pyrazolo[4,3-c]pyridine 5-oxide (2.5 g, 8.4 mmol) in DCE (55 mL) under nitrogen was added phosphorous oxybromide (7.2 g, 25.2 mmol). The reaction mixture was stirred for 30 minutes, warmed to room temperature, and stirred for a further 4 hours. The reaction was 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 (20% ethyl acetate in cyclohexane) to afford the title compound as a white solid (927 mg, 31% yield). LCMS (Method D): RT=3.74 min, m/z: 360 [M+H+].