A solution of phosphorus oxychloride in dichloromethane was added to a mixture of 2-chloro-5-methylpyridine 1-oxide and triethylamine in dichloromethane at 0 ℃. After stirring for 2 hours, the mixture is reacted at room temperature for 24 hours. After that, the water was added and the mixture was neutralized with a sodium hydroxide solution. The organic layer was washed with a saturated brine solution and the aqueous layer was extracted with ethyl acetate and washed with a saturated brine solution. The combined organic layers were dried over magnesium sulfate, filtered, and concentrated under reduced pressure to afford 2,4-Dichloro-5-methylpyridine. The by-product of this reaction is 2,6-dichloro-3-methyl-pyridine.
