Background and overview of the purification method of 2,3-dichloro-5-trifluoromethylpyridine
Fluorinated, heterocyclic, and chiral are the three major characteristics of modern pesticides and new drugs in the pharmaceutical field. In recent years, new fluorine-containing pyridine pesticides, such as acetamipyr, triflufenuron, tetracycline and fluazinam, have the advantages of broad-spectrum systemic absorption, high efficiency, low toxicity, and low pollution, and have become highly effective pesticides, Backbone varieties of herbicides and fungicides. 2,3-Dichloro-5-trifluoromethylpyridine (2,3,5-DCTF) is a key intermediate in the production of these new pesticides and has become a hot topic in the industry.
Purification method of 2,3-dichloro-5-trifluoromethylpyridinePurification method
Report on the purification method of 2,3-dichloro-5-trifluoromethylpyridine 1.
1. Add 500g of 2,3-dichloro-5-trifluoromethylpyridine with a purity of 98.5% into the reaction kettle with stirring, and add ammonia water with a weight percentage of 25% to the reaction solution 2000g, control the reaction temperature to 70°C, stir the reaction, take a sample for analysis and detect that the front impurity peak of 2,3-dichloro-5-trifluoromethylpyridine has completely disappeared. The reaction solution was separated into static layers and the organic phase was obtained.
2. Transfer the organic phase into the distillation kettle with a water separator, add 2000g of distilled water, control the water vapor distillation temperature to 95°C, collect the liquid at the bottom of the water separator, and put this liquid into the distillation tower for decompression Distillate, control the pressure at -0.096MPa, collect the 140-150°C fraction, and obtain 484.2g of 2,3-dichloro-5-trifluoromethylpyridine, with a purity of 99.95% and a yield of 96.8%.
Report 2 on the purification method of 2,3-dichloro-5-trifluoromethylpyridine.
A method for purifying crude 2,3-dichloro-5-trifluoromethylpyridine. The specific processing method includes the following steps:
Add 1000g of crude 2,3-dichloro-5-trifluoromethylpyridine with a purity of 90% into the reaction kettle, wash it with water twice, use 1L of water each time, control the washing temperature to 30°C, and add a concentration of 148g of 10% sodium hydroxide, control the reaction temperature to 30°C, stir and react for 8 hours, add chlorobenzene, layer the water and fluorinated material, and separate the organic phase in the fluorinated material. Put the collected organic phase liquid into the distillation tower for vacuum distillation, control the pressure to -0.05MPa, and collect the 110-120°C fraction. Add 148g of sodium hydroxide with a concentration of 10%, control the reaction temperature to 20°C, stir and react for 8 hours, wash with water 2 times, use 1L of water each time, control the water washing temperature to 30°C, extract the organic phase after layering, perform distillation and Put it into the distillation tower for vacuum distillation, the distillation control pressure is -0.05MPa, collect the 110-120°C fraction, and finally obtain 861.9g of 2,3-dichloro-5-trifluoromethylpyridine, with a purity of 99.51% , the yield is 95.3%.
Refining method of 2,3-dichloro-5-trifluoromethylpyridine and highly selective preparation method
Add 2-chloro-5-trifluoromethylpyridine (90.8g, 0.5mol) and 15% WCl6/AC (activated carbon-loaded WCl6, loading 15wt%, 12g) into a 250mL high-pressure reaction kettle (Inconel alloy), after installing the lid of the kettle, fill it with 2MPa nitrogen and maintain the pressure for 2 hours. Conduct a leak test on the reaction kettle. After confirming that the reactant does not leak, put it into an ice ethanol bath for cooling. When the reaction kettle is cooled to 0 After the temperature reaches 150°C, about 37.5g of chlorine gas (0.5mol) is filled into the reaction kettle from the gas phase tube of the reaction kettle, and then the reaction kettle is placed in a heating mantle with magnetic stirring, and the reaction system is heated to 150°C under stirring conditions. At this time, the pressure of the reaction system is about 2.0MPa, and the reaction is continued at this temperature for 20 hours. After the reaction is completed, when the temperature of the reaction system drops to room temperature, nitrogen gas is passed from the liquid phase tube to the reaction kettle for 30 minutes (the replaced tail gas is passed into the alkali washing bottle for absorption and neutralization), the reaction kettle is opened, and the reaction kettle is filtered through Separate the catalyst and product by adding 10wt% NaOH solution to the product to neutralize, extract and separate the liquid to obtain an oily product. The obtained oily product was dried with anhydrous sodium sulfate and weighed to a mass of 107.0 g. Qualitative analysis was performed using GC-MS and quantitative analysis was performed using the gas chromatography internal standard method.
Application of purification method of 2,3-dichloro-5-trifluoromethylpyridine
CN201110329726.6 reports a preparation method of Jingcao Neng, which mainly involves preparing catalyst hydrogen peroxide, (S)-2-chloropropionic acid methyl ester, and 2,3-dichloro-5- Trifluoromethylpyridine, 3-chloro-2-(4-hydroxyphenoxy)-5-trifluoromethylpyridine, and the final prepared Jinggaicaoneng. The preparation method of the invention is simple, easy to operate, effectively utilizes the chiral property of hydrogen peroxide, and has good catalytic effect as a catalyst. In addition, the invention has less by-products, high yield and high purity, and is suitable for large-scale production.
CN200610154456.9 reports a method for preparing pyridofop-chloride with high optical purity. The method is carried out according to the following steps: methoxyphenylboronic acid: (1) using 2,3-dichloro-5 -Trifluoromethylpyridine and hydroquinone are used as starting materials. In the presence of K2CO3 as a base, react in N, N-dimethylformamide solvent at 105~110°C. At the end of the reaction, the intermediate is obtained by separation and purification. 3-chloro-2-(4-hydroxyphenoxy)-5-trifluoromethylpyridine; (2) 3-chloro-2-(4-hydroxyphenoxy)-5-trifluoromethylpyridine and (L)-2-Methanesulfonyloxypropionic acid methyl ester performs a nucleophilic substitution reaction in the presence of K2CO3 as a base using chlorobenzene as the solvent at 70~110°C. After the reaction is completed, the target product is purified pyridine chloride after post-treatment. He Ling. In the present invention, chlorobenzene is used as the solvent for the reaction between 3-chloro-2-(4-hydroxyphenoxy)-5-trifluoromethylpyridine and (L)-2-methanesulfonyloxypropionic acid methyl ester. The fluop-in has higher optical purity than di-tert-butyl dicarbonate.ee value is greater than 92%.
References
[1][Chinese invention] CN201610913216.6 A method for removing 2,3-dichloro-5-trifluoromethylpyridine precursor
[2][Chinese invention] CN201910307925.3 A purification method of 2,3-dichloro-5-trifluoromethylpyridine
[3][Chinese invention] CN201711275197.X A method for preparing 2,3-dichloro-5-trifluoromethylpyridine with high selectivity
[4][Chinese invention] Preparation method of CN201110329726.6 Jinggaicaoneng
[5]CN200610154456.9 A method for preparing fine pyriflufen with high optical purity
