2-Chloro-3-(trifluoromethyl)pyridine

22253-72-1

52334-81-3

65753-47-1

In a four-necked flask equipped with a stirrer, thermometer and a drying tube, 32.62 g of 3-trifluoromethylpyridine N-oxide (CAS: 22253-72-1) and 46.0 g of phosphorus trichloride were added. The reaction mixture was stirred at 105-110°C for 2 hours. Subsequently, the temperature was raised to 120-125°C and the reaction was continued for 5 hours. The reaction mixture was analyzed by liquid chromatography and confirmed to contain 0.16% of 3-trifluoromethylpyridine N-oxide, 50.34% of 2-chloro-3-trifluoromethylpyridine and 25.34% of 2-chloro-5-trifluoromethylpyridine. The reaction mixture was heated under reduced pressure (100 mmHg) until an internal temperature of 75°C was reached to remove excess TCPO by distillation. The reaction mixture was slowly added to 163.1 g of ice water at a controlled temperature not exceeding 30°C and stirred for 1 hour. The reaction mixture was extracted with 1,2-dichloroethane, stirred for 30 minutes and partitioned. The organic layer was washed with water to give 132.11 g of a 1,2-dichloroethane solution containing 2-chloro-3-trifluoromethylpyridine. Liquid chromatographic analysis showed that the solution contained 13.17 g of 2-chloro-3-trifluoromethylpyridine.