Hydrochloric Acid → 2-Chloro-5-fluoro-1,3-benzothiazole

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Reaction Steps

A solution of 242 g (3.5 mol) of sodium nitrite in 440 ml of water is added dropwise with stirring to a mixture, cooled to -10° C., of 147 g (0.87 mol) of 2-amino-5-fluoro-benzothiazole, 1700 ml of conc. hydrochloric acid and 20 g of copper power and the reaction mixture is stirred at 0° C. for 60 minutes and at 50° C. for a further 60 minutes. It is then extracted with chloroform and the solvent is carefully removed by distillation from the organic phase in a water-jet vacuum. 80 g (49% of theory) of 2-chloro-5-fluoro-benzothiazole are obtained as a crystalline residue of melting point 69° C.

Provenance & Evidence