Iodine → 3-Iodo-7-phenylimidazo[1,2-a]pyridine

A solution of 7-phenylimidazo[1,2-a]pyridine (1-4, 110 mg, 0.56 mmol, 1 equiv) and iodine (140 mg, 0.56 mmol, 1.0 equiv) in acetic acid (4 mL) was stirred at 23° C. for 18 h. More iodine (130 mg) was added and the mixture was stirred for 24 h at 70° C. A third portion of iodine (130 mg) was added and heating (70° C.) was continued for 2 h. The reaction mixture was basified with aqueous saturated sodium bicarbonate solution (100 mL), and the remaining iodine was quenched with addition of aqueous saturated sodium thiosulfate solution (10 mL). The mixture was extracted with EtOAc (100 mL), and the organic layer was washed with brine, dried over sodium sulfate, and then concentrated to give 3-iodo-7-phenylimidazo[1,2-a]pyridine (1-5) as a light-brown solid. 1H NMR (300 MHz, CDCl3) δ 8.18 (d, 1H, J=7.3 Hz), 7.82 (s, 1H), 7.73 (s, 1H), 7.67 (m, 2H), 7.50 (t, 2H, J=7.3 Hz), 7.42 (t, 1H, J=7.3 Hz), 7.23 (d, 1H, J=7.0 Hz).