[Cl:1][C:2]1[CH:15]=[CH:14][C:5]2[NH:6][C:7]([S:12][CH3:13])=[N:8][S:9](=[O:11])(=[O:10])[C:4]=2[CH:3]=1.C(=O)([O-])[OH:17].[Na+].[OH-].[Na+].BrBr.Cl>>[Cl:1][C:2]1[CH:15]=[CH:14][C:5]2[NH:6][C:7]([S:12]([CH3:13])=[O:17])=[N:8][S:9](=[O:11])(=[O:10])[C:4]=2[CH:3]=1A suspension of 7-chloro-3-methylsulfanyl-4H-1,2,4-benzothiadiazine 1,1-dioxide (0.5 g) in an aqueous solution of sodium hydrogen carbonate (0.22 g/25 mL) was supplemented dropwise with 2M NaOH until complete dissolution. Liquid bromine (0.1 mL) was added under stirring at room temperature. After 10 min., the resulting suspension was adjusted to pH 2-3 with 6N HCl and the insoluble material was collected by filtration and washed with water. The white precipitate was suspended in methanol (20 mL), stirred for 1 h and then collected by filtration, washed with methanol and dried (yield: 0.45 g); m.p. 260-261° C.
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