General procedure for the synthesis of methyl 4-amino-3-iodobenzoate from methyl 4-aminobenzoate: dissolve methyl 4-aminobenzoate (5.0 g, 0.033 mol), benzyltrimethylammonium dichloroiodonate (22.1 g, 0.056 mol), and calcium carbonate (5.0 g, 0.050 mol) in a solvent mixture of dichloromethane (200 ml) and methanol (100 g). . The reaction mixture was heated to reflux overnight with stirring. Upon completion of the reaction, the solution was cooled to room temperature, washed with saturated sodium bisulfate solution, and the organic phase was dried over anhydrous sodium sulfate and concentrated under reduced pressure to afford the crude product methyl 4-amino-3-iodobenzoate (9.6 g, quantitative yield), which was used in the subsequent reaction without further purification. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 3.75 (s, 3H), 6.09 (s, 2H), 6.75 (d, J = 8.59 Hz, 1H), 7.66 (dd, J = 8.59, 2.02 Hz, 1H), 8.11 (d, J = 2.02 Hz, 1H).
