The synthesis of 2,4-dichloroquinoline is as follows:A suspension of quinoline-2,4-diol (150 g, 931 mmol) in POCl3 (975 mL, 10.4 mol) was stirred at reflux for 6 hr and the reaction mixture was concentrated. The residue was diluted with CHCl3 (500 mL) and the solution was poured into ice water. The aqueous layer was extracted with CHCl3 (three times). The combined organic layer was dried over MgSO4, filtrated, concentrated, and purified by flash chromatography (silica gel, 20% EtOAc in hexane) to give 2,4-dichloroquinoline (177 g, 96%) as a pale brown solid.
