Introduction:
Fluorine, heterocyclic and chiral are the three major characteristics of modern pesticides and new drugs in the field of medicine. In recent years, new types of fluoropyridine pesticides, such as pyridinium, pyridinium urea, pyridinium and fluridine, have the advantages of broad spectrum absorption, high efficiency, low toxicity, low pollution and so on, and have become the backbone of efficient insecticides, herbicides and fungicides. Fluorine, heterocyclic and chiral are the three characteristics of modern pesticides and new drugs in the field of medicine. 2, 3-dichloro-5-trifluoromethyl pyridine (2,3,5-DCTF) is a key intermediate in the production of these new pesticides, and has become a hot spot in the industry.
Preparation method :
1. 500g of 2, 3-dichloro-5-trifluoromethyl pyridine with a purity of 98.5% was added to the reaction kettle with stirring, 2000g of ammonia water with a concentration of 25% by weight was added to the reaction liquid, and the reaction temperature was controlled at 70℃. The pre-impurity peaks of 2, 3-dichloro-5-trifluoromethyl pyridine have all disappeared. The reaction liquid was stratified at rest and separated into organic phases.
2. Transfer the organic phase into the distillation kettle with water separator, add 2000g of distilled water, control the water vapor distillation temperature to 95℃, collect the liquid under the water separator, and put the liquid into the rectification tower for decompress rectification, the pressure is controlled at -0.096MPa, and collect 140 ~ 150℃ distillate. The purity of 2, 3-dichloro-5-trifluoromethyl pyridine was 99.95% and the yield was 96.8%.
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