General procedure for the synthesis of 1-chloro-2,5-difluoro-4-iodobenzene from 2,5-difluorochlorobenzene: Trifluoromethanesulfonic acid (9.9 mL, 110 mmol) was slowly added to 2-chloro-1,4-difluorobenzene (2.2 g, 15 mmol) at room temperature, and the reaction mixture was subsequently cooled down to 0 °C. At 0 °C, N-iodosuccinimide (3.16 g, 14.1 mmol) was added in batches. After the addition was completed, the reaction was kept for 10 minutes, then gradually warmed to room temperature and continued stirring for 2 hours. After completion of the reaction, the reaction mixture was poured into ice water and extracted with hexane. The organic layers were combined, washed with saturated Na2SO4 solution, dried over anhydrous Na2SO4 and concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography (100% hexane as eluent) to afford the target product 1-chloro-2,5-difluoro-4-iodobenzene (3.0 g, 74% yield). The structure of the product was confirmed by 1H NMR (400 MHz, CDCl3): δ 7.52 (dd, J = 5.4, 7.8 Hz, 1H), 7.17-7.08 (m, 1H).
