A mixture of compound 2-fluoro-4-bromobenzaldehyde (2 g, 10 mmol), hydroxylamine hydrochloride (830 mg, 12 mmol) and sodium acetate (656 mg, 8 mmol) in water (5 mL) and ethanol (20 mL) was stirred under nitrogen and kept at 25C for 5 hours. The solution was concentrated to dryness. The crude product was washed with water (5 mL) and dried to give compound 280B. potassium carbonate (638 mg, 4.6 mmol) was added to a solution of compound 280B (717 mg, 3.3 mmol) in DMSO (10 mL) at 25 C. The mixture was stirred at 120 C overnight. The solution was cooled to room temperature and extracted with ethyl acetate (100 mL x 2). The combined organic layers were washed with water (50 mL) and brine (50 mL), dried over anhydrous sodium sulfate, filtered and evaporated to give the compound 6-bromo-1,2-benzisothiazole 280C.
