[Br:1][C:2]1[CH:3]=[CH:4][C:5]([O:19]C)=[C:6]([C:8]2[N:9]=[C:10]3[CH:15]=[CH:14][CH:13]=[CH:12][N:11]3[C:16]=2[CH:17]=[O:18])[CH:7]=1.B(Br)(Br)Br.O>ClCCl>[Br:1][C:2]1[CH:3]=[CH:4][C:5]([OH:19])=[C:6]([C:8]2[N:9]=[C:10]3[CH:15]=[CH:14][CH:13]=[CH:12][N:11]3[C:16]=2[CH:17]=[O:18])[CH:7]=12-(5-bromo-2-methoxyphenyl)imidazo[1,2-a]pyridine-3-carbaldehyde (0.1 g, 3 mmol) was dissolved in dichloromethane (0.5 mL) at −78° C. BBr3 (1 mL) was added by dropwise stirred for 2 hours at that temperature. Then warmed to 25° C. and stirred for 10 hours. H2O (20 mL) was added by dropwise at −78° C. 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-hydroxyphenyl)imidazo[1,2-a]pyridine-3-carbaldehyde (40 mg, yield: 48%). 1H-NMR (CDCl3, 400 MHz) δ 10.29 (s, 1H), 9.76 (s, 1H), 7.78˜7.79 (m, 2H), 7.65˜7.69 (m, 1H), 7.46˜7.48 (m, 1H), 7.20˜7.22 (m, 1H), 7.00˜7.02 (m, 1H). MS (M+H)+: 317/319.
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