[OH:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][N:6]=[CH:5]2.[F:11][C:12]1[CH:13]=[C:14]([N+:19]([O-:21])=[O:20])[CH:15]=[CH:16][C:17]=1F.C(=O)([O-])[O-].[K+].[K+]>CN(C=O)C>[F:11][C:12]1[CH:13]=[C:14]([N+:19]([O-:21])=[O:20])[CH:15]=[CH:16][C:17]=1[O:1][C:2]1[CH:3]=[C:4]2[C:8](=[CH:9][CH:10]=1)[NH:7][N:6]=[CH:5]25.00 g (37.3 mmol) of 5-hydroxyindazole are dissolved in 40 ml of anhydrous DMF. 5.93 g (37.3 mmol) of 3,4-difluoronitrobenzene and 5.15 g (37.3 mmol) of potassium carbonate are added, and the mixture is stirred at 40° C. overnight. For work-up, the mixture is filtered off with suction through kieselguhr, diluted with water and extracted three times with ethyl acetate. The combined organic phases are washed 1× with saturated aqueous sodium chloride solution, dried over sodium sulfate and concentrated using a rotary evaporator. The residue is chromatographed twice on silica gel using cyclohexane/ethyl acetate 3:1→1:1→1:2 and then purified by preparative HPLC.
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