General procedure for the synthesis of ethyl 5-hydroxy-6-iodo-3-pyridinecarboxylate from ethyl 5-hydroxynicotinate: a solution of ethyl 5-hydroxynicotinate was added to water (15 L), followed by sodium carbonate (733 g, 30.7 mol) and iodine (965 g, 15.3 mol). The reaction was carried out at room temperature with stirring for 2 hours. The progress of the reaction was monitored by thin layer chromatography (TLC) (unfolding agent: petroleum ether/ethyl acetate = 1/1, Rf = 0.8) and after confirming the completion of the reaction, the pH was adjusted to 7 by slowly adding 1N hydrochloric acid to the reaction solution, when a solid precipitated. The solid product was collected by filtration and dried under reduced pressure to give ethyl 5-hydroxy-6-iodo-3-pyridinecarboxylate (925 g) as a yellow solid in 82.5% yield.
