c) Synthesis of 5-bromo-7-fluorobenzofuran: 5-bromo-7-fluoro-1-benzofuran-2-carboxylic acid (1.274 mmol) was dissolved in quinoline (2 mL) and copper powder (0.236 mmol) was added. The reaction system was sealed by nitrogen replacement and placed in a microwave reactor and radiated at 230 °C for 60 min. Upon completion of the reaction, the reaction solution was diluted with ethyl acetate and filtered through diatomaceous earth. The filtrate was concentrated under reduced pressure and the residue was purified by fast column chromatography (eluent: n-hexane) to afford 5-bromo-7-fluorobenzofuran as a colorless oil (280 mg, 100% yield).1H NMR (400 MHz, DMSO-d6) δ ppm: 8.17 (d, J = 2.02 Hz, 1H), 7.77 (d, J = 1.77 Hz. 1H), 7.55 (dd, J = 10.48, 1.64 Hz, 1H), 7.07 (dd, J = 3.16, 2.15 Hz, 1H).
