(Step 1) Synthesis of 2-bromo-6-fluorobenzothiazole: Copper(I) bromide (619 mg, 4.32 mmol) was suspended in acetonitrile (10 mL). To this suspension was added tert-butyl nitrite (640 mg, 5.38 mmol) followed by stirring at 60°C for 5 min. To the reaction mixture was added 2-amino-6-fluorobenzothiazole (605 mg, 3.60 mmol). The resulting mixture was stirred at 60°C for 10 minutes. After completion of the reaction, it was cooled to room temperature and the reaction mixture was diluted with ethyl acetate. The ethyl acetate layer was washed sequentially with 1N HCl and saturated saline and then dried over anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography using n-hexane/ethyl acetate (5:1, v/v) as eluent to afford 2-bromo-6-fluorobenzothiazole (330 mg, 40% yield) as a brown solid. The structure of the product was confirmed by 1H-NMR (CDCl3) δ: 7.19-7.24 (m, 1H), 7.49-7.52 (m, 1H), 7.92-7.96 (m, 1H) and mass spectrometry (ESI) m/z 273.8 ([M + H + MeCN]+).
