[F:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][C:10]=1[F:11])[NH:7][CH:6]=[C:5]2[CH:12]=O.Cl.[NH2:15]O.C(OC(=O)C)(=O)C.[OH-].[Na+].Cl>O1CCCC1.N1C=CC=CC=1>[F:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][C:10]=1[F:11])[NH:7][CH:6]=[C:5]2[C:12]#[N:15]To a solution of 5,6-difluoro-1H-indole-3-carbaldehyde (1.0 g) in tetrahydrofuran (15 ml) were added hydroxylamine hydrochloride (0.81 g) and pyridine (1.9 g), and this mixture was stirred at 80° C. for 8 hours. Acetic anhydride was added to reaction mixture and this mixture was stirred at 80° C. for 8 hours. After cooling to ambient temperature, 2 mol/L aqueous sodium hydroxide solution was added to this mixture and resulting mixture was stirred for 30 minutes. This mixture was poured into 2 mol/L hydrochloric acid and the precipitated solid was collected by filtration, and washed with water and n-hexane. The solid was dissolved in ethyl acetate and this residue was purified by column chromatography on silica gel (eluent: n-hexane/ethyl acetate) to give the title compound (0.95 g).
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