[F:1][C:2]1[CH:21]=[C:20]([C:22]2[CH:27]=[CH:26][N:25]=[CH:24][CH:23]=2)[CH:19]=[CH:18][C:3]=1[C:4]([NH:6][C:7]1[C:8](O)=[C:9]([CH:14]=[CH:15][CH:16]=1)[C:10]([O:12][CH3:13])=[O:11])=[O:5].CC1C=CC(S(O)(=O)=O)=CC=1>C1(C)C=CC=CC=1>[F:1][C:2]1[CH:21]=[C:20]([C:22]2[CH:23]=[CH:24][N:25]=[CH:26][CH:27]=2)[CH:19]=[CH:18][C:3]=1[C:4]1[O:5][C:8]2[C:9]([C:10]([O:12][CH3:13])=[O:11])=[CH:14][CH:15]=[CH:16][C:7]=2[N:6]=1Methyl 3-(2-fluoro-4-(pyridin-4-yl)benzamido)-2-hydroxybenzoate (2.50 g, 6.83 mmol) and 4-methylbenzenesulfonic acid (3.25 g, 17 mmol) were added to toluene (50 mL) and the mixture was stirred at 118° C. for 2 days. The resulting mixture was extracted with ethyl acetate (100 mL×4) and concentrated. The crude product was purified by column chromatography (silica gel, petroleum ether/ethyl acetate=20:1 to 10:1) to obtain methyl 2-(2-fluoro-4-(pyridin-4-yl)phenyl)benzo[d]oxazole-7-carboxylate as white solid (500 mg, yield 21%). LC-MS (ESI) m/z: 349 (M+1)+.
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