Preparation method of 2-chloro-5-picoline

Abstract

The invention relates to a preparation method of 2-chloro-5-picoline. According to the method, benzyl chloride is taken as a raw material, benzaldehyde is taken as an inhibitor, ammonia is taken as an aminating agent, a product has a condensation reaction with propionaldehyde under the catalysis of an organic base, then a product has acetylation with an acetylation reagent, finally, a product performs cyclization under actions of N,N-dimethylformamide and triphosgene, and the target product 2-chloro-5-picoline is obtained through purification. The product purity is higher than or equal to 99.5%, and the total molar yield higher than 80% is realized. The preparation method of 2-chloro-5-picoline has good reaction selectivity, high yield and few three wastes, is simple to operate and facilitates industrialized production.

Description

technical field [0001] The invention belongs to the technical field of fine chemical preparation, and in particular relates to a preparation method of 2-chloro-5-picoline. Background technique [0002] 2-Chloro-5-picoline is an important pesticide intermediate, which can be used to synthesize imidacloprid, acetamiprid, nitenpyram and other neonicotinoid insecticides. Spectrum high efficiency, low toxicity, less dosage, long duration, good safety, strong drug resistance and other advantages, these products have a huge production tonnage, therefore, the development of high yield, high quality, high safety, low environmental protection, low cost 2 -Chloro-5-picoline has practical significance. [0003] At present, there are mainly five methods for the synthesis of 2-chloro-5-picoline: [0004] 1. Using morpholine and propionaldehyde as raw materials, they are synthesized through cyclization, dehydrogenation, chlorination and other reactions. This method has a long route, comp...

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Problems solved by technology

[0004] 1. Using morpholine and propionaldehyde as raw materials, they are synthesized through cyclization, dehydrogenation, chlorination and other reactions. This method has a long route, complicated operation, serious environmental pollution and high overall cost; (US4612377, US4645839);

[0005] 2. Using 3-picoline as a raw material, it is synthesized through nitrogen oxidation, chlorination and other reactions. This type of method has easy-to-obtain raw materials, fewer reaction steps, and lower cost, but this type of method has poor route selectivity, many by-products, and product separation Purification is difficult, it is difficult to obtain high-purity products or the purification cost is high and the yield is low; (EP0393453, EP0512436);

[0006] 3. Using nicotinic acid as a raw material, it is synthesized through reactions such as chlorination and reduction. This kind of method has many reaction steps, and the operation is relatively cumbersome, and because of the shortage of raw material nicotinic acid, the cost is high, so it is difficult to industrialize; (EP0569947);

[0007] 4. Using cyclopentadiene and acrolein as raw materials, it is synthesized through Diels-Alder reaction, Michael addition and other reactions. Easy to polymerize, so there are a lot of three wastes in this route, poor safety, serious environmental pollution; (US05229519);

[0008] 5. Using benzylamine and propionaldehyde as raw materials, they are synthesized through reactions such as cyclization and phosphorus oxychloride chlorination. The current yield of this type of method is low, the total yield is 68%, and the product purity is not high. (EP0546418, US5304651)

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