Method for preparing high-quality high-purity pymetrozine

Abstract

The invention discloses a method for preparing high-quality high-purity pymetrozine. The method includes the following steps: acetamido triazone and acid are used as raw materials to produce an acidolysis reaction; after the reaction is qualified, alkali is used to neutralize; then, the product obtained in the previous step and a 3-pyridinecarboxaldehyde solution produce a condensation reaction; performing after-treatment to obtain a pymetrozine active compound. According to the invention, during the alkali neutralization process, weak base, such as ammonia water and ammonium salts of weak acid, is used to substitute for strong base, such as sodium hydroxide and liquid caustic soda which are commonly used in the existing production technology, to perform the neutral reaction and prepare the pymetrozine product, so that fewer flocculent impurities are generated, the reaction system viscosity is reduced, the filtration, separation and washing are facilitated, the prepared pymetrozine does not harden, the product is loose, the quality is high, the purity is increased from about 95% to 98% or above, and pymetrozine is especially suitable for large-scale industrial production.

Description

technical field [0001] The invention belongs to the technical field of pesticide chemical synthesis, and in particular relates to a preparation method of high-quality and high-purity pymetrozine. Background technique [0002] Pymetrozine belongs to pyridine or triazinone insecticides. It is a brand-new non-biocide insecticide. It was first developed by Ciba-Geigy in Switzerland in 1988. Pests showed excellent control effect. Studies using electropenetration graph (EPG) technology have shown that no matter in drip, feeding or injection experiments, as soon as aphids or planthoppers come into contact with pymetrozine, they will immediately produce a stylet blocking effect, stop feeding immediately, and eventually starve to death , and this process is irreversible. Pyridoxone has no knockdown activity and does not produce direct toxicity to insects. Therefore, pymetrozine has an excellent function of blocking insect transmission. Pymetrozine has a wide insecticidal spectrum,...

AI Technical Summary

Problems solved by technology

[0005] 1. Liquid caustic soda or sodium hydroxide flake alkali is too alkaline. During the dropping process, it is easy to cause the decomposition of the intermediate triazine ring and cause side reactions, resulting in many impurities. The formation of flocs or colloidal state, the post-treatment of pymetrozine is always accompanied by the problem of high viscosity, flocs or colloidal impurities are very easy to block the filter holes of the filter cloth, resulting in pymetrozine suction filtration or centrifugation or pressure filtration If the separation time is longer, the wet product of pymetrozine obtained is very hard and stiff, which brings obstacles to subsequent washing and refining operations, and the effect is not ideal. The purity of the obtained pymetrozine product is generally about 95%, which has a great impact on product quality and purity

[0006] 2. The impurities produced in the process of acidolysis and neutralization have good solubility under acidic conditions. In order to avoid the formation of flocs or colloids of such impurities under neutral or weak alkaline conditions, and reduce the viscosity of the post-treatment process The problem is that the pH has to be adjusted to a weak acidity of about 5.5-6.0 during the neutralization process, but this will cause the aminotriazinone salt to be unable to neutralize the completely free aminotriazinone, which will affect the subsequent interaction with nicotinaldehyde. Condensation reaction, resulting in a decrease in the yield of pymetrozine