Ammonium thiocyanate → 6-Bromo-5-fluoro-1,3-benzothiazol-2-amine

To a solution of 4-bromo-3-fluoro-aniline (3.68 g, 19.37 mmol) in glacial AcOH (40 mL) was added ammonium thiocyanate (2.95 g, 38.74 mmol). When the reaction mixture was almost clear, it was placed in a cold water bath and a solution of bromine (3.1 g, 19.37 mmol) in glacial AcOH (10 mL) was added dropwise over a 10 min period. The reaction mixture was stirred at room temperature for 1 h, then it was concentrated in vacuo. The residue was partitioned between 1 N aqueous KOH and ethyl acetate. The aqueous layer was further extracted with ethyl acetate, and the combined organic layers were adsorbed on silica gel. Purification by flash chromatography on silica gel using a gradient of 0-70% ethyl acetate/hexane afforded 2.73 g of 6-bromo-5-fluoro-benzothiazol-2-ylamine as a light yellow solid (57% yield): 1H NMR (DMSO-d6) δ 7.29 (d, 1H), 7.78 (broad s, 2H), 7.99 (d, 1H); MS (m/z) 247, 249 [M+H+]+.