Nitric Acid → 6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-5-nitro-2(3H)-benzothiazolone

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Reaktionsschritte

A compound of 6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-2(3H)-benzothiazolone (11.5 g) was added portionwise to concentrated sulfuric acid (200 g) which had been cooled to a temperature of 5° to 10° C. The reaction mixture was stirred at a temperature of 0° to 5° C. for 10 minutes. To the reaction mixture was dropwise added a 98% nitric acid (3 g). The reaction mixture was stirred at a temperature of 0° to 5° C. for 2 hours, and then poured onto ice. Ethyl acetate (1 liter) was added to the mixture, and the whole was stirred. The ethyl acetate layer was separated, washed with water, with a saturated aqueous sodium bicarbonate solution, and then with a saturated aqueous sodium chloride solution, and dried over anhydrous sodium sulfate. The solvent was distilled off, and the residue was recrystallized from ethanol, so that the aimed product, i.e. 6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-5 -nitro-2(3H)-benzothiazolone (13.0 g) was obtained. m.p. 192°-193° C.

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