P.2 4-Nitrobenzisothiazole, 5-nitrobenzisothiazole and 7-nitrobenzisothiazole 300 g of benzisothiazole are added, with cooling, to 750 ml of concentrated sulfuric acid, the solution is cooled to -40° C., and 227.5 g of potassium nitrate are added in portions, in such a manner that the temperature does not rise above room temperature. After standing at room temperature for 15 hours, the reaction mixture is poured onto ice and the solid portion is filtered off and dried. The product is chromatographed on silica gel with tetrahydrofuran:methylene chloride:hexane 5:10:85. After evaporation, there are isolated from the fractions 5.5% of the theorectical yield of 4-nitrobenzisothiazole, 56.5% of the theoretical yield of 5-nitrobenzisothiazole and 36.8% of the theoretical yield of 7-nitrobenzisothiazole (compounds 16, 11 and 1, Table).
