The general procedure for the synthesis of 4-fluorobenzofuran-3(2H)-ones from 2-fluoro-6-methoxybenzoyl chloride and trimethylsilylated diazomethane was as follows: 3.7 mL of a 2.0 M solution of trimethylsilylated diazomethane ether (yellow) was slowly added to a reaction vial containing 0.57 g (3.0 mmol) of 2-fluoro-6-methoxybenzoyl chloride under stirring conditions. After 3 hours of reaction, the solvent was removed by evaporation. The yellow residue obtained was dissolved in 3 mL of acetic acid (the reaction was exothermic and gaseous, requiring cooling of the reaction vial in a water bath for 1 min), followed by stirring at room temperature for 15 min. After completion of the reaction, the solvent was removed by vacuum distillation, and the red residue was dissolved in 2 mL of dichloromethane, washed sequentially with water and brine, and finally dried with anhydrous sodium sulfate. The crude product was purified by column chromatography (the eluent was a hexane solution of 10% ethyl acetate) to give 0.24 g (53% yield) of 4-fluorobenzofuran-3(2H)-one as a white solid.1H NMR (300 MHz, CDCl3): δ 7.58 (m, 1H), 6.92 (br d, 1H), 6.71 (t, 1H), 4.65 (s, 2H). 2H).
