Method for preparing 2-bromo-3-ethylsulfonylpyridine

Abstract

Preparation of 2-bromine-3-ethylsulfonyl-pyridine is carried out by taking mixture of acetic oxide and acetic acid as reactive solvent, reacting 1,1,3,3-tetramethoxy-propane with acetic oxide under zinc chloride catalyzing to generate p-cis-trans-isomer, condensing with ethylsulfonyl-methyl cyanide to generate (di-cis-4-trans)-2-ethylsulfonyl-5-methoxy-2, 4-pentadienoic nitrile, and reacting it with hydrogen bromide to obtain final product. It's accurate, simple and efficient, and it has gentle reactive condition, higher content and can be used for industrial production. It can be used as pyrimi-butyl critical intermediate of synthetic sulfonylurea super-efficient corn, tomato, and herbicide jade pyrsulfogentian.

Description

technical field [0001] The invention relates to a preparation method of 2-bromo-3-ethanesulfonylpyridine. Background technique [0002] 2-Bromo(chloro)-3-ethanesulfonylpyridine is a key intermediate for the preparation of the ultra-efficient sulfonylurea herbicide rimsulfuron-methyl (patent US4774337). Generally, 1,1,3,3-tetramethoxypropane or N,N-dimethylaminoacrolein and ethanesulfonyl acetonitrile are condensed to form pentadiene nitrile, and then reacted with hydrogen bromide (or hydrogen chloride) to prepare 2-Bromo(chloro)-3-ethanesulfonylpyridine was obtained. [0003] ①. Patent US 5,206,372 once reported the following preparation method: [0004] [0005] ②. Document J.Org.Chem.39, 3436 (1974) and patent US 5,107,057 have reported the following preparation method: [0006] [0007] In method ①, N, N-dimethylaminoacrolein, which is expensive and not industrialized in China, is used, which is not suitable for industrialization. In method ②, the solvent used f...

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Problems solved by technology

[0007] In method ①, N,N-dimethylaminoacrolein, which is expensive and not industrialized in China, is used, which is not suitable for industrialization

In method ②, the solvent used for the condensation reaction is acetic anhydride, and the crude product of compound III is an oily substance, which is not high in content and difficult to purify. It is easy to emulsify during post-treatment liquid separation and difficult to operate; the obtained compound IV is an oily substance with a low content , is difficult to purify, and the reaction yield is also low, only about 58%; compound III is reacted with excess hydrogen bromide, although the bromide salt solid that can form compound IV is precipitated from the reaction system, but the solid particles are very small, Difficult to filter, not conducive to product purification

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