General procedure for the synthesis of 3-chloro-6-fluoroisoquinoline using 1,3-dichloro-6-fluoroisoquinoline as starting material: hydriodic acid (20 mL, 45% aqueous solution) and red phosphorus (0.9 g, 28.9 mmol) were added to a stirring solution of 1,3-dichloro-6-fluoroisoquinoline (2.5 g, 11.6 mmol) in acetic acid (40 mL) at room temperature. The reaction mixture was stirred at 100 °C for 4 hours. After the reaction was completed, it was cooled to room temperature and the mixture was concentrated under reduced pressure. The residue was dissolved in dichloromethane (100 mL) and washed with saturated aqueous sodium bicarbonate (2 x 100 mL). The organic layer was dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated under reduced pressure to give 3-chloro-6-fluoroisoquinoline as a dark gray solid. Mass spectrum (ESI, m/z): 182.0 [M + 1]+; 1H NMR (400 MHz, DMSO-d6) δ 9.24 (s, 1H), 8.32-8.29 (m, 1H), 8.04 (s, 1H), 7.82-7.76 (m, 1H), 7.66-7.61 (m, 1H).
