2-Chloro-4-fluorobenzoic acid (4.000 g, 22.91 mmol) was used as starting material and mixed with NaIO3 (0.906 g, 4.58 mmol) and I2 (2.037 g, 8.02 mmol) in concentrated H2SO4 (40 mL). The reaction mixture was stirred at room temperature for 8 hours. Upon completion of the reaction, cold water (100 mL) was added to quench the reaction. The resulting solid product was collected by filtration, washed with H2O and dried under vacuum at 50 °C to give 2-chloro-4-fluoro-5-iodobenzoic acid as a white solid (6.824 g, 99% yield). The melting point of the product was 124-126 °C; IR (pure sample) showed absorption peaks located at 1700, 1580, 1558, 1400, 1348, 1298, 1258 cm-1 ; 1H NMR (500 MHz, CD3OD) showed δ= 8.33 (d, J = 7.0 Hz, 1H), 7.37 (d, J = 8.0 Hz, 1H); 13C NMR (125 MHz, CD3OD) showed δ= 164.9, 163.3 (d, J = 250.0 Hz), 142.0 (d, J = 3.7 Hz), 135.1 (d, J = 10.0 Hz), 128.4, 117.9 (d, J = 28.7 Hz), 78.1 (d, J = 26.2 Hz); 19F NMR (470 MHz, CD3OD) showed δ= -89.5; HRMS (EI) m/z [M]+ calculated value C7H3ClFIO2: 299.8850, measured value: 299.8855.
