30.7 ml (329 mmol) of phosphoryl chloride at 0.7 C and 6 drops of sulfuric acid were added to 9 g (6.6 mmol) of 2-hydroxy-5-iodonicotinonitrile. The reaction mixture was heated at 110C for 5 hours and then at room temperature overnight. The reaction mixture was poured into a beaker containing ice and a small amount of water to form a precipitate. The mixture was allowed to gradually return to room temperature, then filtered and rinsed with water. The solid was dried to give 2-chloro-5-iodo-3-pyridinecarbonitrile.
