General procedure for the synthesis of methyl 5-chloro-2-iodobenzoate from methanol and 5-chloro-2-iodobenzoic acid: a mixture of 5-chloro-2-iodobenzoic acid (3.0 g, 10.62 mmol), dichlorosulfoxide (12 mL), and N,N-dimethylformamide (0.6 mL) was gently heated with a heat gun until a homogeneous solution was formed (about 15 minutes). Subsequently, the reaction solution was continued to be stirred at 23 °C for 30 min, after which the solvent was removed by concentration under reduced pressure. Methanol (24 mL) was added to the crude product and stirred at 23 °C for 30 min. After the reaction was completed, the reaction solution was again concentrated under reduced pressure. The crude product was purified by rapid chromatography on a Biotage silica gel column with a gradient of cyclohexane to cyclohexane:ethyl acetate (85:15) as eluent to give methyl 5-chloro-2-iodobenzoate (3.02 g, 10.20 mmol, 96% yield).UPLC-MS analysis showed a retention time of 1.17 min and a molecular ion peak m/z 296.6 [M + H]+ , analyzed by method 12.
