Preparation and application background and overview of 2-chloro-6-trifluoromethylpyridine
2-Chloro-6-trifluoromethylpyridine is a key intermediate in the synthesis of pesticides. The pesticide was successfully developed by a U.S. company in the 1990s and used to control field crop pests such as cotton, soybeans, and rapeseed. The product. It has the characteristics of strong efficacy, low dosage per mu, low toxicity, low residue, and remarkable effect. It has become the backbone product of pesticides in developed countries abroad.
2-Chloro-6-trifluoromethylpyridine is not only used as a new pesticide intermediate, but also widely used in the fields of organic synthesis, dyes and medicine. In recent years, it has been found that the introduction of trifluoromethyl group into the heterocyclic ring can improve The lipophilicity of the compound can thereby improve the permeability of biological membranes and tissues and the electron attraction when reacting with living organisms, thereby enhancing the physiological activity of the compound. The compound 2-chloro-6-trifluoromethylpyridine has a trifluoromethyl group introduced into the pyridine ring. At present, 2-chloro-6-trifluoromethylpyridine has been widely used in pesticides, medicines, dyes and other fields.
Preparation and application of 2-chloro-6-trifluoromethylpyridine
Preparation and application of 2-chloro-6-trifluoromethylpyridine (1) Chlorination
Pump into the 1000L chlorination kettle 200kg of dry raw materials 2-chloro-6-methylpyridine, 6kg of phosphorus trichloride, 1000kg of carbon tetrachloride, 5kg of benzoyl peroxide, and turn on the light source (800W (two ultraviolet lights), heat up the steam through the jacket, open the tail gas system, operate at a slight negative pressure (-0.01MPa), when the temperature in the kettle reaches 80°C, start to pass chlorine, the chlorine flow rate is 45kg/h, first quickly After the reaction is slow, keep the reflux reaction. Through sampling and analysis, the G.C detects that the trichlorine content reaches more than 90% and the dichlorine content is less than 5%, which is the reaction end point. If you need to continue the reaction, take samples and analyze every 2 hours until it is qualified.
After passing the test, stop passing chlorine, pump the reaction liquid into the carbon tetrachloride distillation kettle, and steam away carbon tetrachloride under normal pressure. When the carbon tetrachloride content in the chlorinated material is less than 2.0%, stop distillation and cool down. to 60℃ and put it into a 200kg plastic bucket for later use.
Preparation and application of 2-chloro-6-trifluoromethylpyridine (2) Fluorination
Put 800kg of chlorinated material into a hot melt tank and heat to dissolve it (about 50℃), put it into a 1500L fluorination kettle, pass the condenser into ice brine (temperature of ice brine -15℃-5℃), add 0.5kg Antimony pentachloride, connect the pipelines between the anhydrous hydrogen fluoride cylinder and the fluoride kettle (the angle valve above the hydrogen fluoride cylinder is connected to the compressed air, and the angle valve below is connected to the fluoride kettle), ensure there is no leakage, open the exhaust system, and open the kettle For the hydrogen fluoride charging valve and the pressure reducing valve after the condenser, close other valves on the kettle, slowly open the angle valve under the hydrogen fluoride cylinder and rely on the self-pressure of the cylinder to add it to the fluorination kettle. After 20 minutes, open the angle valve above the cylinder and use 0.2Mpa. Use compressed air to press the remaining hydrogen fluoride in the cylinder into the fluorination kettle. After adding a total of 500kg of hydrogen fluoride in the two bottles, close all the valves on the kettle, turn on stirring, turn on the thermal oil furnace, and heat the jacket with hot oil (and close the condenser at the same time) 11 Triglyceride carbonate cooling ice salt water), control the reaction temperature 160°C-185°C, when the pressure of sodium pyrithione reaches 8.5Mpa, slowly release the pressure. After multiple times of release, the pressure no longer rises and remains at 8.5Mpa for reaction 16 hour, lower the temperature and slowly release the pressure to 0.0Mpa, and introduce air to inflate it for more than 6 hours until HF disappears.
Add 1/2 water and industrial sodium carbonate to the steam distillation kettle, stir and dissolve, press the fluorinated material into the steam distillation kettle, raise the temperature for steam distillation, complete the distillation, and stratify still to obtain 2-chloro-6-trifluoro Crude methylpyridine is placed in a 200kg plastic bucket for later use.
Preparation and application of 2-chloro-6-trifluoromethylpyridine (3) Distillation
Dissolve 1200kg of crude 2-chloro-6-trifluoromethylpyridine and put it into the vacuum distillation kettle to open the vacuum. When the vacuum reaches -0.07Mpa, the rectification kettle begins to heat up to 140°C, and the cooler is at 30°C hot water circulation, hot water pipe insulation from the cooler to the receiving tank. When there is reflux at the top of the tower, control the heating and maintain the reflux for 60 minutes, and then press the production: reflux = 1:8 vacuum distillation , the extracted fraction enters the front fraction receiving tank, and is sampled once every 20 minutes, followed by chromatography. When the content of the main fraction reaches more than 98%, the extracted fraction is cut into the finished product receiving tank. At this time, the reflux ratio is controlled at 1:4. When the kettle temperature rises and the temperature at the top of the tower drops, adjust the reflux ratio to 1:8, take samples once every 10 minutes, and perform chromatographic tracking analysis. When the content of the main fraction is lower than 98%, stop extraction, cool down, and vent. After the system is at normal pressure, Stop the vacuum pump, measure the pre-fraction, finished product, and post-fraction, and package and store the finished product. Product yield is 85%.
Preparation and application of 2-chloro-6-trifluoromethylpyridine
CN201711146933.1 discloses a preparation method of 2-hydroxy-6-trifluoromethylpyridine. The preparation method of 2-hydroxy-6-trifluoromethylpyridine is characterized by: using 2-chloro-6-trifluoromethylpyridine as raw material, 2-chloro-6-trifluoromethylpyridine and hydroxide The potassium aqueous solution is mixed and the reaction is sealed; after the reaction is completed, hydrochloric acid solution is added dropwise to the reaction material to neutralize it, and then the product is obtained by centrifugation, water washing, secondary centrifugation and drying. The raw materials of the invention are simple and easy to obtain, no organic solvent is added during the reaction process, the process is simple, the production cost is low, the product yield is high, and it is suitable for widespread promotion and application.
References
[1][China invention, China invention authorization] Preparation method of CN200610044599.42-chloro-6-trifluoromethylpyridine
[2]CN201711146933.1 A preparation method of 2-hydroxy-6-trifluoromethylpyridine
