Sodium Iodide → 6-Iodopyridine-3-carboxylic acid

To 27.97 g (186.6 mmol) of sodium iodide cooled to -78° C. was added 121.77 g (71.6 ml, 952.0 mmol) of hydriodic acid (57 wt %). The reaction mixture was allowed to warm slightly with stirring for 5 minutes, and then 30.00 g (190.4 mmol) of 6-chloronicotinic acid was added. The resulting mixture was allowed to warm to room temperature with stirring and then heated at 120°-125° C. in an oil bath for 42 hours. A dark brown layer formed above the yellow solid material. The reaction mixture was allowed to cool to room temperature and then poured into acetone (chilled to 0° C.). The resultant yellow solid was collected by filtration, washed with 200 ml of 1N NaHSO3 solution, and dried in high vacuum (3 mm Hg) to give the title compound as a pale yellow solid.