1. 4-Hydroxypyridine (4.76 g, 50.1 mmol) and sodium carbonate (Na2CO3, 10.8 g, 100 mmol) were dissolved in 200 mL of water.
2. Iodine (I2, 12.7 g, 50.1 mmol) was added to the above solution and the reaction mixture was stirred for 14 hours.
3. After completion of the reaction, the pH of the reaction mixture was adjusted to 5 with concentrated hydrochloric acid (HCl).
4. The solid obtained was suspended in boiling ethanol and thermally filtered.
5. After removal of solvent, the resulting solid was recrystallized from methanol (MeOH) to give 4-hydroxy-3-iodopyridine (5.1 g, 46% yield).
6. The product was characterized by 1H NMR (DMSO-d6) δ 8.26 (br s, 1H), 7.70 (s, 1H), 7.69 (d, J = 7 Hz, 1H), 6.14 (d, J = 7 Hz, 1H); MS (DCI/NH3) m/z: 222 (M + H)+, 239 (M + NH4)+.
