O=P(Cl)(Cl)Cl.[Br:6][C:7]1[CH:8]=[CH:9][C:10]([O:22][CH3:23])=[C:11]([C:13]2[N:14]=[C:15]3[CH:20]=[CH:19][CH:18]=[CH:17][N:16]3[CH:21]=2)[CH:12]=1.O.CN([CH:28]=[O:29])C>>[Br:6][C:7]1[CH:8]=[CH:9][C:10]([O:22][CH3:23])=[C:11]([C:13]2[N:14]=[C:15]3[CH:20]=[CH:19][CH:18]=[CH:17][N:16]3[C:21]=2[CH:28]=[O:29])[CH:12]=1POCl3 (0.39 g, 2.5 mmol) was added to DMF (0.43 g, 6 mmol) by dropwise at 0° C. Then 2-(5-bromo-2-methoxyphenyl)imidazo[1,2-a]pyridine (0.1 g, 0.33 mmol) in DMF (3 mL) was added. Then warmed to 25° C. and heated to 120° C. and stirred for 30 minutes and at 80° C. for 2 hours and then cooled to 25° C. H2O (20 mL) was added and extracted with EtOAc (3*50 mL), washed by aq NaHCO3 (3*50 mL) and brine (50 mL). After concentrated, the resulting residue was purified using prep-TLC (petroleum ether:EtOAc=3:1) to provide 2-(5-bromo-2-methoxyphenyl)imidazo[1,2-a]pyridine-3-carbaldehyde (100 mg, yield: 90%). 1H-NMR (CDCl3, 400 MHz) δ 9.85 (s, 1H), 9.60 (s, 1H), 7.77˜7.81 (m, 2H), 7.54˜7.58 (m, 2H), 7.12˜7.15 (m, 1H), 6.92˜6.94 (m, 1H), 3.82 (s, 3H). MS (M+H)+: 331/333.
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