A kind of preparation method of pesticide intermediate 2,3-dichloro-5-picoline

Abstract

The invention belongs to the technical field of organic chemical industry, and relates to a preparation method of an important intermediate, namely 2,3-dichloro-5-methylpyridine, of halogenated pyridine-containing organic compounds, more specifically to 2,3-dichloro-5-methylpyridine which is prepared by taking 5-methyl-3,4-dihydropyridine-2(1H)-ketone and chlorine gas as the starting materials through catalyzed synthesis, wherein the total yield is maintained to be 75% or above. The preparation method of pesticide intermediate, namely 2,3-dichloro-5-methylpyridine, provided by the invention, has the characteristics that lewis acid and ligand are combined with each other to serve as the catalytic system, so that high selectivity in reaction is achieved, the production cost is low, the equipment investment is low, and a safe and environment-friendly production environment is further achieved.

Description

technical field [0001] The invention belongs to the technical field of organic chemical industry, and relates to a preparation method of an important intermediate 2,3-dichloro-5-picoline of halogen-containing pyridine organic compounds, more specifically, to a method of using 5-methyl-3 , 4-dihydropyridine-2(1H)-one (abbreviation: pyridone) and chlorine gas are used as starting materials to catalyze the synthesis of 2,3-dichloro-5-methylpyridine with a stable total yield of more than 75%. . The present invention is characterized by adopting the combination of Lewis acid and ligand as the catalytic system, so that the reaction has high selectivity, low production cost, low equipment investment and safe and environment-friendly production environment. Background technique [0002] The raw material pyridone is prepared by the propionaldehyde-morpholine method described in the US4612377 patent. The specific synthetic route is as follows: Propionaldehyde and morpholine are catal...

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Problems solved by technology

[0005] At present, there are few documents on the synthesis of 2,3-dichloro-5-methylpyridine, Pews R.G (Pews R.G, Lysenko Z.Synthesis of halogenated pyridine[J].Org.Chem, 1985,50(25): 5115-5119) directly synthesized 2,3-dichloro-5-picoline by cyclization of dichloroacetonitrile and methacrolein, but the conversion rate of dichloroacetonitrile in the reaction is only about 60%, the utilization rate of raw materials is low, and the production high cost

Although, in the catalyst-free chlorination process, pyridone can also generate a small amount of 2,3-dichloro-5-picoline, but the yield is less than 20%.

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