Method for electrolytic synthesis of 4-amino-3,6-dichloropyridine-2-carboxylic acid

Abstract

The invention discloses a method for electrolytic synthesis of 4-amino-3,6-dichloropyridine-2-carboxylic acid, which comprises: taking 4-amino-3,5,6-trichloropyridine-2-carboxylic acid (picloram) as a raw material, and performing selective dechlorination on the raw material through electrolysis; and acidifying, filtering and drying electrolyte after the electrolytic reaction is over, and obtaining the target compound, namely the 4-amino-3,6-dichloropyridine-2-carboxylic acid, wherein the electrolytic reaction is performed at normal temperature, and the alkalinity of the electrolyte is between 0.5 and 2.0 percent. The method has good reaction selectivity, high purity of the synthesized target compound, and simple process, has the reaction performed at normal temperature and normal pressure, effectively reduces the occurrence of side reactions of hydroxylation and amino oxidation, has less investment when being used for industrial production, and basically has no pollution of the three wastes.

Description

technical field [0001] The invention belongs to the field of organic electrochemical synthesis and relates to an electrolytic synthesis method of 4-amino-3,6-dichloropyridine-2-carboxylic acid. Background technique [0002] 4-Amino-3,6-dichloropyridine-2-carboxylic acid, trade name Aminazopyr, Aminopyralid, Dichloroaminopyridine, is a pyridinecarboxylic acid herbicide, it can quickly enter the plant In vivo, it is easily absorbed by stems and leaves, resulting in growth interruption and rapid necrosis. It is mainly used for weed control in pastures, plantations and non-crop areas, and for weeding in rapeseed and buckwheat fields. [0003] The electrolytic reduction method is currently the most effective synthesis method for 4-amino-3,6-dichloropyridine-2-carboxylic acid. US Patent USP6352635 discloses the use of electrolytic reduction method to synthesize 4-aminopyridine acid. This patent also involves 4-aminopyridine - The electrolytic synthesis method of 3,6-dichloropyri...

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Problems solved by technology

[0003] The electrolytic reduction method is currently the most effective synthesis method for 4-amino-3,6-dichloropyridine-2-carboxylic acid. US Patent USP6352635 discloses the use of electrolytic reduction method to synthesize 4-aminopyridine acid. This patent also involves 4-aminopyridine - The electrolytic synthesis method of 3,6-dichloropyridine-2-carboxylic acid, but this method has side reactions of hydroxylation and oxidation of amino groups, and the purity of the target substance after synthesis is not high enough, only 90%. If it is used in industrial production, Post-treatment purification must be carried out, which will increase production costs and increase the amount of three wastes to be treated; chemical synthesis method to synthesize 4-amino-3,6-dichloropyridine-2-carboxylic acid is to use diclopyridinate as raw material, through nitration , reduction, hydrolysis, purification and other steps are completed

However, the chemical synthesis method has the disadvantages of using expensive raw materials, difficult to control the reaction, low conversion rate, large amount of three wastes to be treated, and being very unfriendly to the environment, making it difficult to realize industrialization

[0004] The selective dechlorination of the electrolytic reduction method was published for the first time in U.S. Patent No. 4,217,185, mainly for the synthesis of diclopyralid by electrolytic reduction dechlorination of 3,4,5,6-tetrachloropicolinic acid; U.S. Patent No. 4,242,183 announced The method for preparing 2,3,5-trichloropyridine by electrolytic reduction of tetrachloropyridine; the above method does not involve the synthesis of amino-containing pyridine carboxylic acid; and the working electrode is a silver plate or silver powder, and the unit working area of ​​the silver plate electrode is small and the reaction cycle is long. , low space-time efficiency; the silver powder electrode is complex, the silver powder is easy to fall off, and the service life is short

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