Method for preparing cyhalofop-butyl

Abstract

Provided is a method for preparing cyhalofop-butyl. The method comprises the steps that (R)-2-(4-hydroxyphenoxy) propionic acid and 3,4-difluorobenzonitrile are subjected to an etherification reaction under the alkaline condition to obtain an (R)-2-[2-fluorine-4-cyano]-phenoxyl]-propionic acid intermediate, and then the (R)-2-[2-fluorine-4-cyano]-phenoxyl]-propionic acid intermediate and normal butanol are subjected to an esterification and dehydration reaction to obtain a cyhalofop-butyl product. According to the method for preparing cyhalofop-butyl, the reaction path is shortened, the production cost is reduced, the acylating chlorination step is omitted, the requirement on equipment is lowered, operation is simplified, the emissions of three wastes are reduced, and great guiding significance on process amplification and production is achieved.

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] Herbicide is an indispensable substance to ensure agricultural production. According to calculations, if the farmland is not weeded, the crop loss will reach 50-70%. In developed countries, the amount of herbicide accounts for 40-50% of the total amount of pesticides. The use of pesticides has also increased rapidly, and has now reached more than 30% of the total amount of pesticides, and the growth trend is very strong. [0003] In recent years, the area of ​​direct-seeding rice fields has been continuously expanding, resulting in an increase in the base of barnyardgrass and chinensis, and serious weed damage. At present, butachlor, bensulfuron-methyl, and quinclorac are the herbicides used in large amounts for weeding in paddy fields. These three varieties account for more than 50% of the mar...

AI Technical Summary

Problems solved by technology

[0016] "Pesticide Research and Application" 2007, Volume 11, No. 1, reported a synthetic method of cyhalofop-methyl, which is similar to the above-mentioned route 2, and its synthetic route is: using (S)-methyl lactate as raw material, first synthesize (S)-Methyl p-toluenesulfonyl lactate, then react with hydroquinone to obtain an intermediate, and then undergo hydrolysis and ethanol esterification to obtain (R)-2-(4-hydroxyphenoxy) ethyl propionate , and then reacted with 3,4-difluorobenzonitrile to obtain ethyl (R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propionate, which was then hydrolyzed into acid, The acid is reacted with n-butanol to generate cyhalofop through esterification. However, the process route is long and the operation is cumbersome. At the same time, a large amount of waste water is generated, and the by-product of p-toluenesulfonic acid cannot be recovered and is difficult to handle.

[0017] Route 3: Condensation reaction of (R)-2-(4-hydroxyphenoxy)propionic acid and 3,4-difluorobenzonitrile in an organic solvent under basic catalytic conditions to generate intermediate (R)-2- [4-(2-fluoro-4-cyano)-phenoxy]-propionic acid, the intermediate is then reacted with phosgene to generate intermediate (R)-2-[4-(2-fluoro-4 -Nitryl)-phenoxy]-propionyl chloride, and finally carry out esterification reaction with n-butanol to generate cyhalofop-methyl, in this method, intermediate (R)-2-[4-( 2-fluoro-4-nitrile group)-phenoxy]-propionic acid, carried out acyl chloride reaction, used poisonous, strongly corrosive acidic raw materials such as phosgene or thionyl chloride during acyl chloride, to experimental equipment and High operating requirements, increasing potential safety hazards

Images