Hydrochloric Acid → 2-Benzothiazolinone, 6-fluoro-

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22.4 g of 2-amino-6-fluorobenzothiazole (pure substance content: 97%) and 191.1 g of 30% hydrochloric acid are introduced into a 750 ml pressure vessel at room temperature. The mixture is subsequently heated for 30 minutes at 50° C. and then cooled to 10° C. Then, 46.7 g of aqueous, 40% sodium nitrite solution are metered in at a uniform rate in the course of 1 hour at 10° C., with vigorous stirring. After metering in has ended, stirring of the reaction mixture is continued for 12 hours at 20° C. Excess nitrite is then removed by adding approximately 12.5 g of 18% aqueous urea solution. The reaction vessel is subsequently sealed, and the reaction mixture is heated for 5 hours at 140°-150° C. (pressure approximately 4-5 bar). After the mixture has cooled to 20° C., the gray, crystalline product is filtered off with suction, washed with a small amount of water and dried at 60° C. to constant weight. 18.9 g of 6-fluorobenzothiazol-2-one with a pure substance content of 97.7% are obtained (corresponding to 85% yield). The product which is redissolved under alkaline conditions has a melting point of 188.4° C.

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