Review of Synthesis of 2,3-Dichloro-5-Trifluoromethyl ...

Introduction

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CAS -84-7 2,3-Dichloro-5-Trifluoromethyl Pyridine is a very valuable fluorine-containing pyridine organic intermediate. It is used in the production of a series of high-efficiency insecticides such as diafenthiuron, fenflunom, the high-efficiency herbicide fenflufop and the high-efficiency fungicide fluazinam. Key Intermediates of New Pesticide Varieties

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%.

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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.

Source

Review of Synthesis of 2,3-Dichloro-5-trifluoromethyl Pyridine [YUAN Qi-liang, SHEN De-long, LU Xin-xin, Fu Qing]

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