Preparation method of metamitron

Abstract

The invention discloses a preparation method of metamitron. The method comprises the following steps of: adding 2-acethydrazide hydrazone-2-phenyl-acethydrazide, a polarity organic solvent, a phase-transfer catalyst and a water absorbent serving as raw materials into a reaction device; heating until reflux to perform a dehydration cyclization reaction; sampling to perform HPLC (high performance liquid chromatography) analysis, and finishing the reaction until the conversion rate of the 2-acethydrazide hydrazone-2-phenyl-acethydrazide reaches over 99 percent; and cooling to a temperature of lower than 0 DEG C and filtering after the reaction is finished, washing and drying the filter cake to obtain the metamitron, wherein the phase transfer catalyst is tetrabutylammonium bromide or benzyl triethyl ammonium chloride. The method is short in reaction time, high in yield, and low in energy consumption and production cost.

Description

technical field [0001] The invention relates to a preparation method of a herbicide, in particular to a preparation method of fenmetrione. Background technique [0002] The chemical name of metamitron is 4-amino-3-methyl-6-phenyl-1,2,4-triazin-5(4H)-one. It is a low-toxicity and low-residue herbicide developed by Bayer in 1975. It is a triazone selective pre-emergent herbicide. It is mainly absorbed through the roots of plants and then transported into the leaves. Er reaction to play a herbicidal effect. It can control monocotyledonous and dicotyledonous weeds. It is a herbicide used to control gramineous and broad-leaved weeds in beet fields. It is mainly used for field weeding of dryland crops, such as corn and sugar beets. Straw, wild sesame, bluegrass and other weeds. [0003] At present, the main route of synthesizing benzoylformate is as follows: first, methyl benzoylformate and acetylhydrazide are reacted to obtain methyl 2-acetylhydrazinobenzoylformate, and then m...

AI Technical Summary

Problems solved by technology

The deficiency of the method of this document is: (1) yield is lower, less than 90%

(2) Long reaction time and high energy consumption

(3) Using anhydrous sodium acetate as a water-absorbing agent not only requires a large amount (excessive anhydrous sodium acetate), but also increases costs, and the water-absorbing effect is not ideal

The deficiencies of the method of this document are: (1) although the method writes that the theoretical yield can be increased to 92% by adding a water-absorbing agent, on the one hand a large number of experimental results show that the dehydration and cyclization reaction of this method is particularly difficult, and the actual The yield is all less than 63%, and the content is less than 78%, so the theoretical yield of 92% is not very credible; 92% yield is even more unbelievable

(2) Long reaction time and high energy consumption

(3) Use anhydrous sodium acetate (including anhydrous sodium carbonate and anhydrous sodium sulfate) as the water-absorbing agent, not only in a large amount (the molar ratio of water-absorbing agent to 2-acetylhydrazidehydrazone-2-phenylacetylhydrazide is 1: 1~1.2∶1, too much), increase the cost, and the water absorption effect is not very ideal