[Na].[S:2]1([C:13]2[C:8](=[CH:9][CH:10]=[CH:11][CH:12]=2)[C:6](=[O:7])[NH:5]1)(=[O:4])=[O:3].[S:14]1[C:18]2[C:19](C(Cl)=O)=[CH:20][CH:21]=[CH:22][C:17]=2[N:16]=[N:15]1>CN(C)C1C=CN=CC=1.C(Cl)Cl>[C:13]1([S:2]([NH:5][C:6]([C:19]2[C:18]3[S:14][N:15]=[N:16][C:17]=3[CH:22]=[CH:21][CH:20]=2)=[O:7])(=[O:3])=[O:4])[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1After the addition of a spatula tip of 4-dimethylaminopyridine to a suspension of 4 g of the sodium salt of saccharin in 60 ml of methylene chloride, a solution of 3.9 g of benzo-1,2,3-thiadiazole-7-carboxylic acidchloride in 20 ml of methylene chloride is added dropwise at a maximum of 20° C. The mixture is stirred overnight at room temperature and thenext day the suspension is poured onto ice-water and extracted with ethyl acetate. The extracts are washed with dilute sodium hydrogen carbonate solution and water, dried and concentrated by evaporation. The residue is recrystallised from tetrahydrofuran/hexane to yield the title compound having a melting point of 173°-175° C.
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