Method for synthetizing 2,6-dichloroquinoxaline by using diketene

Abstract

The invention discloses a method for synthetizing 2,6-dichloroquinoxaline by using diketene. The method comprises the following steps: taking P-chloro-o-nitroaniline and diketene as primal raw materials, and carrying out condensation, cyclization, reduction, acidification and chlorination reactions in sequence so as to obtain 2,6-dichloroquinoxaline; in the reduction step, taking NaHS as a reducing agent; performing the following steps between the steps of reduction and acidification: (1) adding activated carbon into an reaction system in a reduction step, so as to obtain reaction liquid: (2), heating the reaction liquid while stirring until the reaction liquid reaching 323 to 372 K; and (3) leading air into the reaction liquid for reaction for at least 0.1 h. In the invention, the characteristic of alkalinity of the system when 6-chlorine-2-quinoxaline sodium alkoxide is dissolved in water is used, under the stirring and certain-temperature condition, air is blown into the reaction liquid for a certain time, and polysulfide is enabled to be catalyzed and oxidized. Therefore, no elemental sulfur impurities are produced in the subsequent acidification reaction.

Description

technical field [0001] The invention relates to a method for synthesizing 2,6-dichloroquinoxaline, in particular to a method for synthesizing 2,6-dichloroquinoxaline with diketene. Background technique [0002] 2,6-Dichloroquinoxaline is an important intermediate compound, which can be used to synthesize the upland herbicide quizalofop-p-ethyl, and is also the main intermediate for the synthesis of the herbicide glycoside. At the same time, it is also an important fine chemical industry Intermediates, widely used in cosmetics, medicine and other industries. [0003] At present, the synthetic method of 2,6-dichloroquinoxaline mainly contains two kinds: [0004] First, with p-chloro-o-nitroaniline and chloroacetyl chloride as starting materials, 2,6-dichloroquinoxaline is obtained through acid chlorination, hydrogenation, cyclization, oxidation, chlorination and other series of reactions; the process route is as follows As shown in the figure: [0005] [0006] Second, t...

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Problems solved by technology

And when NaHS is used as the reducing agent, in addition to generating Na in the above reaction 2 S and SO 2 In addition, a small amount of polysulfide compounds are also generated. In the subsequent acidification reaction (i.e. reaction 2), polysulfide compounds will generate elemental sulfur and exist in the reaction product, resulting in the final reaction product except the target product 2,6-di In addition to chloroquinoxaline, it also contains a small amount of elemental sulfur (generally about 0.3%, w / w), which has not only affected the quality and purity of the intermediate, but also affected the quality and yield of the follow-up product prepared by the intermediate. Rate

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