Preparation method of cyhalofop-butyl

Abstract

The invention relates to a preparation method of cyhalofop-butyl. The method comprises the following steps: by using (R)-2-(4-hydroxyphenoxy)propionic acid and 3,4-difluorobenzonitrile as raw materials and an inorganic alkali as an acid-binding agent, adding an organic alkali and a phase-transfer catalyst, carrying out etherification reaction under milder conditions within a short time to generate an intermediate (R)-2-[4-(2-fluoro-4-cyano)-phenoxy]-propionic acid, and carrying out esterification reaction for dehydration, wherein the total yield of the two reactions can reach 94% or above, and the optical purity is greater than 99%. The method lowers the etherification reaction temperature, shortens the etherification reaction time, enhances the reaction selectivity, completely maintains the chirality, and increases the product yield, thereby saving the energy consumption and lowering the cost. Besides, in the esterification reaction, the used dehydration solvent can lower the byproduct content, thereby omitting the refinement operation of the product, reducing the discharge amount of three wastes, and being beneficial to environmental protection.

Description

technical field [0001] The invention belongs to the field of herbicide production, and in particular relates to a preparation method of cyhalofop-ethyl. Background technique [0002] Cyhalofop-ethyl is a post-emergent herbicide in paddy fields with high activity and selectivity to weeds at very low doses. It is mainly used to control important grass weeds, especially barnyard grass (including older barnyard grass), Qianjinzi, Kanmai Niang, Xiaokangcao, crabgrass, paspalum, setaria, goosegrass, etc. have excellent effects, are very safe to rice crops, and have the characteristics of low toxicity and low residue. The damage of A. japonicus in paddy fields is serious, but cyhalofop-ester shows extremely high herbicidal activity on A. japonicus before the 4-leaf stage, which cannot be compared with other pesticides. [0003] Therefore, the promotion and application of cyhalofop-fop will play an important role in increasing the production and income of crops nationwide, and the ...

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Problems solved by technology

The process route is long, the operation is cumbersome, a large amount of waste water is generated, and the by-product of p-toluenesulfonic acid cannot be recovered and it is difficult to handle ("Pesticide Research and Application", Volume 11, No. 1, 2007)

[0010] Reaction of hydroquinone with 3,4-difluorobenzonitrile to obtain 3-fluoro-4-(4-hydroxyphenoxy)benzonitrile, and then react with (S)-p-toluenesulfonyl lactylate to generate cyhalofor Esters; affected by raw materials and reaction conditions, there is racemization in the reaction, and only 80-90% (R)-isomers can be obtained in reality. At the same time, considering the cost, 3,4-difluorobenzonitrile and p- In the reaction that diphenol takes place, two phenolic hydroxyl groups of p-diphenol can participate in reaction, generate by-product, increase the consumption of 3,4-difluorobenzonitrile, and 3,4-difluorobenzonitrile is expensive, so this The cost of the route is expensive, and the post-treatment of p-toluenesulfonic acid needs to be further processed by microbial degradation, so this synthetic route is generally not used in industry ("Pesticides", Volume 49, Issue 5, 2010)

[0011] Chinese patent CN104803883A discloses a method for synthesizing cyhalofop-methyl, using L-butyl lactate and p-toluenesulfonyl chloride as raw materials for condensation reaction to generate p-toluenesulfonyl-protected L-butyl lactate, and then reacting with terephthalate The etherification reaction of phenol under alkaline conditions generates (R)-4-hydroxyphenoxypropionic acid, and the etherification product undergoes condensation reaction with 3,4-difluorobenzonitrile in an organic solvent under alkaline conditions to generate cyanide Fluoxate is obtained from the (R)-4-hydroxyphenoxybutyl propionate produced as a raw material, the reaction temperature is 100-110°C, first reflux dehydration and then etherification reaction with 3,4-difluorobenzonitrile Cyhalofop-ethyl, which uses potassium hydroxide as a raw material, the resulting product has a darker color and is prone to side reactions, such as hydrolysis of cyano groups; the etherification reaction temperature is greater than 100°C, and under alkaline conditions, the configuration of the product is likely to occur Racemization, affecting product quality

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