Nitric Acid → 5-Fluoro-7-nitro-2,3-dihydrobenzofuran

A mixture of nitric acid (100%, 1.5 ml, 36 mmol) in acetic anhydride (18 ml) was maintained at room temperature for 0.5 hour. The mixture was added to a solution of 5-fluoro-2,3-dihydrobenzofuran (2.5 g, 18 mmol) in 10 ml acetic anhydride at 10° C. The reaction mixture was stirred at room temperature for 2 hours then poured into ice-water. The mixture was extracted with methylene chloride (3×60 ml), washed with 1N sodium hydroxide (5×100 ml) and brine (200 ml). The organic layer was dried over anhydrous sodium sulfate and filtered. The solvent was removed under vacuum to afford a yellow solid: mp 113-114° C.