Step c: Synthesis of 6-chloro-4-iodo-pyridin-3-amine
Tert-butyl (6-chloro-4-iodo-pyridin-3-yl)-carbamate (10.0 g, 28 mmol) was dissolved in 3 M hydrochloric acid (600 mL), heated to 60°C, and reacted for 12 hours. After completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted with saturated sodium bicarbonate solution to 8. Subsequently, the aqueous layer was extracted with ethyl acetate (100 mL × 3). The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography with the eluent being a petroleum ether solution of 10% ethyl acetate to give 6-chloro-4-iodopyridin-3-amine (6.6 g, 93% yield).
1H-NMR (CDCl3, 400 MHz) δ 7.81 (s, 1H), 7.60 (s, 1H), 4.13 (br s, 2H).
