S(=O)(=O)(O)O.N([O-])=[O:7].[Na+].[Br:10][C:11]1[CH:24]=[CH:23][C:14]2[C:15]3[CH:21]=[CH:20][C:19](N)=[CH:18][C:16]=3[S:17][C:13]=2[CH:12]=1>O>[Br:10][C:11]1[CH:24]=[CH:23][C:14]2[C:15]3[CH:21]=[CH:20][C:19]([OH:7])=[CH:18][C:16]=3[S:17][C:13]=2[CH:12]=1A flask equipped with a stirrer and a thermometer was charged with 209.3 g of concentrated sulfuric acid and 8.93 g of NaNO2 in a nitrogen atmosphere, and cooled to 2° C. Then 24.0 g of the intermediate 7-bromodibenzothiophene-3-yl-amine prepared in Example 1-3 was added, and stirred at 2 to 4° C. for 3 hours. The resulting mixture together with 99.8 g of water was poured into 348.7 g of 65 wt % sulfuric acid preheated to 80° C., stirred at 80 to 85° C. for 5 hours, and cooled to room temperature. The reactant was filtered, extracted six times with 300 ml of ethyl acetate, and vacuum concentrated. The concentrate was purified by silica gel chromatography using chloroform as an eluting solvent to obtain 7.11 g of objective 7-bromodibenzothiophene-3-ol. The 1H-NMR spectrum data and the results of elemental analysis of the product are shown below:
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