Preparation method of clodinafop propargyl

Abstract

The invention relates to a preparation method of clodinafop propargyl used for controlling grassy weeds in wheat fields. R-2-(p-hydroxyphenoxy)propionic acid is taken as a raw material and has a reaction with caustic alkali in water and an aprotic polar solvent to form salt and then has a reaction with 5-chloro-2,3-difluoropyridine to form clodinafop acid, solvents are removed after the material is distilled, water is added to the material, the material is stirred and dissolved, PH (potential of hydrogen) of the mixture is adjusted with acid to be smaller than or equal to 3.5, solids are separated out while the mixture is stirred, and clodinafop acid is obtained after the solids are filtered and dried; the clodinafop acid is dissolved in an organic solvent and has a reaction with propargyl alcohol in the presence of a conventional esterification catalyst, and clodinafop propargyl is obtained. The reaction raw material used in the preparation method is easy to obtain, the reaction is mild, the yield is high, separation and purification are simple, the cost is low, and the preparation method is environment-friendly and has a good industrial application prospect.

Description

technical field [0001] The invention relates to a preparation method of clodinafop-propargyl which is mainly used for controlling gramineous weeds. Background technique [0002] Clodinafop-propargyl is a herbicide with the following chemical structural formula: [0003] [0004] Clodinafop-propargyl is used to control most gramineous weeds in wheat fields, and has the characteristics of wide herbicidal spectrum, quick effect, long-lasting curative effect and high safety. The preparation method of clodinafop-propargyl reported in the literature roughly has the following several kinds at present: [0005] One of the methods is to combine 5-chloro-2,3-difluoropyridine and p-hydroxyphenoxypropionic acid in an aprotic polar solvent (such as DMF, acetonitrile, etc.) in an anhydrous environment and in the presence of a large amount of anhydrous potassium carbonate. , NMP, DMI, DMPU) to condense to obtain the potassium salt of clodinafop-propargyl acid, then add propargyl chlor...

AI Technical Summary

Problems solved by technology

[0009] 1) This reaction route needs to be carried out in an anhydrous system, and the reactants and solvents need to be dehydrated and have high requirements for reaction equipment and central control conditions, which is not conducive to industrial production

[0010] 2) This reaction route requires a large amount of anhydrous potassium carbonate as an acid-binding agent, and its consumption is 2.5-3 times the molar amount of the raw material, which not only costs high, but also produces a large amount of solid waste that is difficult to recycle, causing great pressure on the environment

[0011] 3) This reaction route will cause racemization of the product and produce 2%-5% optical isomers

In order to obtain clodinafop-propargyl with high optical purity, a chiral separation method must be adopted, the cost is high and the yield is low, and the total yield of the product is only 80-85%.

[0012] 4) This reaction route adopts the condensation esterification reaction of propargyl chloride and potassium carboxylate to prepare clodinafop-propargyl, and propargyl chloride has very high polymerization activity, and it is easy to polymerize under alkaline conditions such as potassium carbonate to produce black Tar, which affects the quality of the product and causes difficulties in the purification of the product and recovery of the reaction solvent

[0013] 5) After the reaction of this reaction route, the product needs to be precipitated by adding water, resulting in a large amount of waste water containing organic solvents, which not only wastes solvents, but also causes high waste water treatment costs and the risk of environmental pollution

[0015] This method produces clodinafop-propargyl through indirect esterification, and the reaction needs to be carried out under anhydrous conditions. The cost of raw materials and production costs are high, and a large amount of hydrogen chloride and sulfur dioxide are released during the reaction process. The three wastes are difficult to treat and will cause the risk of environmental hazards.

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