General procedure for the synthesis of 5-iodo-2-methylpyridin-4-amine (i55) from 2-methylpyridin-4-amine: to a solution of 2-methylpyridin-4-amine (5 g, 46 mmol) in water (25 mL) was added sodium carbonate (Na2CO3, 3.4 g, 32 mmol) and the reaction mixture was heated to reflux. Subsequently, potassium iodide (KI, 9.8 g, 59 mmol) and iodine (I2, 9.3 g, 36 mmol, dissolved in 50 mL of water) were added and the reaction was continued at reflux for 7 hours. Upon completion of the reaction, the reaction was quenched with sodium thiosulfate solution followed by extraction of the target compound with dichloromethane (DCM). The organic layer was separated, dried with anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The resulting residue was purified by column chromatography on silica gel (100-200 mesh) using a hexane solution of 25% ethyl acetate as eluent to give the final target product 5-iodo-2-methylpyridin-4-amine (i55) (0.85 g, 8% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 2.20 (s, 3H), 6.00 (s, 2H), 6.49 (s, 1H), 8.22 (s, 1H). Mass spectrum (ESI) showed m/e(M + 1)+: 235.
