2,3-dichloro-5-(trifluoromethyl)pyridine (DCTF) is an important organic intermediate for the agrochemical industry in particular for use in the synthesis of fluazinam and fluopicolide as well as other pesticidal active pyridine compounds.
Overview of Synthetic Routes
1) Using 2,3-dichloro-5-trichloromethylpyridine as raw material
106.16 g (0.4 mol) of 2,3-dichloro-5-trichloromethylpyridine and 180 g (9 mol) of anhydrous hydrogen fluoride were added to a polyethylene reactor, and the temperature was controlled at –20 °C within 3 h Slowly add mercuric oxide, control the reaction temperature of the system not to exceed 35 ℃, and stir the reaction for about 22 h after the addition, until the system is gray-white. Filter, neutralize the filtrate with sodium bicarbonate, extract with dichloromethane, dry with anhydrous sodium sulfate, remove the dichloromethane under reduced pressure to obtain the product 2,3-dichloro-5-trifluoromethylpyridine, the conversion rate is 100%, and the selectivity is 98%.
2) Using 3-methylpyridine as raw material
Take 50 g of 2,3-dichloro-5-trichloromethylpyridine, add catalyst, heat up to 170 °C, slowly introduce anhydrous hydrogen fluoride gas, and react for 11 h. After the reaction is completed, use 5% sodium bicarbonate solution in And, the organic phase was separated, washed with water, and dried to obtain a crude product with a content of 85% and a yield of 65%.
3) Using 2-chloro-5-trifluoromethylpyridine as raw material
Take 363 g of 2-chloro-5-trifluoromethylpyridine, add 325 g of ferric chloride, pass chlorine gas, heat up to 150-170 °C and react for 18 h, add the reaction system to 1.5 L of hot water, separate out The oil layer was dried with anhydrous sodium sulfate and rectified to obtain 163 g of product.