Preparation method of pyroxsulam intermediate

Abstract

The invention discloses a preparation method of a pyroxsulam intermediate, which comprises the following steps: (1) carrying out condensation reaction on 4-alkoxy-1,1,1-trifluoro-3-buten-2-one and phosphonoacetic acid trialkyl ester in an alcohol solvent in the presence of sodium alcoholate to generate an intermediate 3-trifluoromethyl-5,5-dialkoxy pentenoic acid alkyl ester and an isomer of the intermediate 3-trifluoromethyl-5,5-dialkoxy pentenoic acid alkyl ester; and (2) carrying out cyclization reaction on the intermediate generated in the step (1) and ammonium acetate in the presence of a polymerization inhibition catalyst to generate 2-hydroxy-4-trifluoromethylpyridine. According to the method disclosed by the invention, hydroquinone and other polymerization inhibition catalysts are added in the cyclization process, so that polymerization side reaction of a condensation intermediate containing double bonds can be avoided, and the reaction yield and the product purity of the cyclization reaction are ensured. Meanwhile, the 4-butoxy-1,1,1-trifluoro-3-buten-2-one and the phosphonoacetic acid trimethyl ester are adopted as the condensation reaction raw materials, so that not only can higher condensation reaction yield be obtained, but also the cost is lower, and the safety is higher.

Description

technical field [0001] The invention belongs to the technical field of preparation of herbicide intermediates, and in particular relates to a preparation method of acesulfame intermediate 2-hydroxy-4-(trifluoromethyl)pyridine. Background technique [0002] Pyrexsulam (also known as methosulam), commonly known as Pyroxsulam in English, is a sulfonamide herbicide developed by Dow AgroSciences, which has a broad herbicidal spectrum, high herbicidal activity, and efficacy Fast acting features. Acesulfame has a very broad herbicidal spectrum, and has a good effect on common grass weeds in wheat fields, and also has a certain control effect on broad-leaved weeds. Its excellent control effect on vicious gramineous weeds such as kangaroo, ryegrass multiflora, wild oats, and hard grass is the outstanding advantage of acesulfame. It has no cross resistance and is widely used in the field of pesticides, and its synthesis is one of the research hotspots in the field of pesticides in r...

AI Technical Summary

Problems solved by technology

[0007] The disadvantages of this method are: (1) the cyclization reaction is difficult, most of the products are intermediate states before cyclization, and the purity of the target product is very low, less than 50%; (2) the reaction conditions are relatively harsh, requiring no The water anaerobic environment has high requirements on equipment, and the zinc powder needs to be activated in advance, which is difficult to produce and is not suitable for industrial production

[0009] The disadvantages of this method are: (1) the yield is low, especially the yield of the second step cyclization reaction is only 66%; (2) the product is light brown, the purity is also not high, and it is also not suitable for industrial production