Dimethylmaleic anhydride → 2-chloro-5-(2,5-dihydro-3,4-dimethyl-2,5-dioxo-1H-pyrrol-1-yl)benzenesulfonamide

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Reaction Steps

In 3 ml of pyridine, 1 mmol of 5-amino-2-chlorobenzenesulfonamide and 1.05 mmol of 2,3-dimethylmaleic anhydride were stirred at 90°-100° C. for 9 hours. Pyridine was then distilled off from the reaction mixture, followed by the addition of 20 ml of ice water and 0.1 ml of 35% hydrochloric acid to the solid residue. After the mixture thus formed was stirred for 20 minutes, the resulting precipitate was collected by filtration and then dried in air. Yield: 93%. Its physicochemical properties are shown in Table 8.

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