Cesium carbonate (Cs2CO3) (0.6 mmol, 195 mg), o-fluorobenzoic acid (1) (0.3 mmol), photocatalyst [Ir(dF(CF3)ppy)2dtbbpy]PF6(D) (6 μmol, 6.7 mg), N-iodosuccinimide (NIS) (0.9 mmol, 202.5 mg) and iodine (I2) (15 μmol, 5 mol%) were added in order to a 15 mL test tube. 202.5 mg) and iodine (I2) (15 μmol, 5 mol%). The tubes were evacuated and displaced three times with argon, followed by the addition of 3 mL of anhydrous 1,2-dichloroethane (DCE) via syringe under argon protection. The tubes were sealed with Parafilm M, placed in an oil bath fitted with a contact thermometer, and the reaction was carried out at 50 °C by irradiation with a 6 × 5 W blue LED (λmax = 455 nm). After 24 or 36 h of reaction, the reaction mixture was filtered through a 2 cm thick pad of silica gel and the silica gel was washed with dichloromethane (DCM) (50 mL). The filtrates were combined and concentrated under reduced pressure to remove the solvent. The crude product was purified by rapid column chromatography on silica gel to afford the target product o-fluoroiodobenzene (2). (Note: The reaction is extremely sensitive to moisture, and the product yield was significantly reduced to less than 5% when 0.01 equivalents of water was added to the system.)
