The general procedure for the synthesis of 4-chloro-6-iodoquinoline from 6-iodo-4-hydroxyquinoline was as follows: 6-iodo-4-hydroxyquinoline (100 g, 369 mmol) was suspended in phosphorus oxychloride (POCl3, 340 mL, 3.7 mol) at room temperature. After 1 hour of reaction, the reaction mixture was concentrated. The concentrated residue was carefully placed in an ice water bath and neutralized with saturated sodium bicarbonate solution. The resulting brown suspension was filtered and the solid was washed with water (2 x 500 mL) and subsequently dried under vacuum overnight to afford 4-chloro-6-iodoquinoline as a brown solid (103 g, 92% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 8.88 (d, J = 4.8 Hz, 1H), 8.54 (d, J = 1.8 Hz, 1H), 8.15 (dd, J = 8.8, 2.0 Hz, 1H), 7.88 (d, J = 8.8 Hz, 1H), 7.82 (d, J = 4.8 Hz, 1H); mass spectrum (MS) showed m/z of 289.9 ([M + H]+).
