General procedure for the synthesis of 3-chloro-4-iodopyridine using 3-chloropyridine as starting material: lithium diisopropylammonium (LDA, 5.9 mL, 8.88 mmol) was slowly added to a cooled tetrahydrofuran (THF, 30.0 mL) solution of 3-chloropyridine (1.0 g, 8.88 mmol) at -75 °C. The reaction mixture was stirred continuously at -75 °C for 4 hours. Subsequently, iodine (2.2 g, 8.88 mmol) was added and stirring was continued at the same temperature for 1 hour. Upon completion of the reaction, the mixture was quenched with ice water at -70 °C, the organic layer was extracted with ethyl acetate, the organic phases were combined and concentrated to give 0.500 g of the target product 3-chloro-4-iodopyridine. The structure of the product was confirmed by 1H NMR (300 MHz, DMSO-d6): δ 8.01 (d, J = 5.1 Hz, 1H), 8.14 (d, J = 4.8 Hz, 1H), 8.63 (s, 1H).
