Preparation method of 2, 3-dihydro-5-methyl-2-oxo-1, 3, 4-oxadiazole-3-acetone

Abstract

The invention discloses a preparation method of 2, 3-dihydro-5-methyl-2-oxo-1, 3, 4-oxadiazole-3-acetone, which adopts KI and NaI as catalysts, so that the 2, 3-dihydro-5-methyl-2-oxo-1, 3, 4-oxadiazole-3-acetone can be rapidly and completely reacted at a proper low temperature, the safety risks of raw material accumulation, sudden heat release, material rushing and the like are avoided, and the safety and the stability of an alkylation reaction production process are improved; the industrial large-scale production period is shortened to 2-5 hr from 8-12 hr, the reaction production period is greatly shortened, and the production cost is effectively reduced; in the reaction process and the reduced pressure distillation process, hot water heating is relatively mild, reaction parameters are easy to control, and side reaction caused by local overheating is avoided; the product yield is further improved and can reach 95.0% or above, the product with the content of 96.0% or above can be directly obtained without refining and purification, and the industrial safety production requirement is met.

Description

technical field [0001] The invention belongs to the technical field of chemical synthesis of pesticides, and relates to an intermediate of a high-efficiency pesticide pyrazinone pesticide, in particular to a 2,3-dihydro-5-methyl-2-oxo-1,3,4- The preparation method of oxadiazol-3-acetone. Background technique [0002] Pyrazinone is a pyridine or triazinone insecticide, which is a brand-new non-biocidal insecticide. It was first developed by Ciba-Geigy of Switzerland in 1988. Pests showed excellent control effect. Research using electro-penetration mapping (EPG) technology has shown that no matter it is drip, feeding or injection test, as soon as aphids or planthoppers come into contact with pyrazinone, they will immediately produce an oral needle blocking effect, stop feeding immediately, and eventually starve to death , and this process is irreversible. Pyrazinone has no knockdown activity and does not produce direct toxicity to insects. Therefore, pyrazinone has an excel...

AI Technical Summary

Problems solved by technology

In the literature, dangerous bromine is used to carry out bromination reaction first, and then alkylation reaction. There are too many dangerous reaction processes, raw material bromine and monobromoacetone are expensive, and the production cost is very high. Therefore, this method cannot participate in the intense Market competition, the feasibility of industrial production is poor

[0011] In the above synthetic method, the main shortcomings mainly include: the reaction time is relatively long, the synthesis process yield is low, and the product purity is relatively low; this reaction is a typical alkylation reaction, and is one of the main dangerous chemical processes. During the analysis process and the reaction risk assessment process, it was possible to detect a large amount of monohaloacetone remaining in the reaction system. After the dropwise addition, it was detected that about 25% to 40% of monohaloacetone remained in the reaction system, especially the cheap raw material monochloroacetone. The reaction activity of acetone is low, and a large amount of it remains during the dropping process and the heat preservation reaction after the dropping. About 35% to 40% of monochloroacetone remains, and the phenomenon that the conversion reaction cannot be completed immediately. This reaction is an exothermic reaction. Since the two main reaction raw materials exist in the reaction system at the same time, when a certain concentration is accumulated, the two raw materials will suddenly accelerate the reaction, the reaction temperature will rise sharply, the reaction rate will continue to accelerate, the reaction temperature will rise even faster, and the vicious cycle of mutual promotion may cause the reaction to run out of control. , punching material, over-temperature and over-pressure explosion and other major safety risks; and this reaction system has certain heat sensitivity, the higher the temperature, the easier the product will be degraded and lost

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