C([O-])(=O)C.[Na+].[N+:6]([C:9]1[CH:17]=[CH:16][CH:15]=[C:14]2[C:10]=1[CH:11]=[N:12][NH:13]2)([O-:8])=[O:7].C(Cl)(Cl)Cl.[Br:22]Br>C(O)(=O)C>[Br:22][C:11]1[C:10]2[C:14](=[CH:15][CH:16]=[CH:17][C:9]=2[N+:6]([O-:8])=[O:7])[NH:13][N:12]=1Sodium acetate (52.8 g, 644 mmol) and 4-nitro-1H-indazole (100 g, 613 mmol) were mixed with acetic acid (1000 mL) and chloroform (1000 mL) in a 5 L 4-neck flask with mechanical stirring. A solution of bromine (103 g, 644 mmol) in acetic acid (120 mL) was added over approximately 3.5 hours, while keeping the temperature below 21° C. After the addition was completed, the reaction mixture was stirred for an additional 2 hours. The reaction mixture was concentrated under reduced pressure. Water (2000 mL) was added to the residue. The yellow solids were collected by filtration and washed with water (3×1000 mL). The solids were air-dried on the filter and then under vacuum at 40° C. to give the desired product (129 g) as a yellow solid.
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