A kind of continuous flow preparation method of 2,6-diethyl-4-methyl bromobenzene

Abstract

The invention discloses a continuous flow preparation method of 2,6-diethyl-4-methyl bromobenzene. The whole preparation process is carried out in an integrated reactor, and diazotization is continuously added at the feed port of the integrated reactor. Reagent, acid and 2,6-diethyl-4-methylaniline are subjected to diazotization reaction, and the obtained diazonium salt is subjected to bromination reaction with bromination reagent, and 2, The crude 6-diethyl-4-methyl bromobenzene was added with methylcyclohexane to extract and separate the phases, and the organic phase was washed with water, washed with saturated sodium carbonate and precipitation to obtain 2,6-diethyl-4- methyl bromide. The production process of the invention is safe and efficient, does not cause accumulation of high-risk diazonium salts, solves the problem of high viscosity of the kettle-type reaction system, has high product yield and purity, and is simple and efficient in process operation.

Description

technical field [0001] The invention relates to a preparation method of a pesticide intermediate, and more particularly to a continuous flow preparation method of 2,6-diethyl-4-methylbromobenzene. Background technique [0002] 2,6-Diethyl-4-methylbromobenzene is a key intermediate for the herbicide pinoxaden. [0003] CN109134187A, CN106928253A, CN102395546A, CN108864144A all reported that 2,6-diethyl-4-methylaniline was first diazotized by batch process, and then brominated to prepare 2,6-diethyl-4- The method of methyl bromobenzene. [0004] These methods have the following significant disadvantages: [0005] (1) There are great potential safety hazards, which limit the increase in production capacity. After the diazotization reaction, there will be a large amount of diazonium salts in the reactor. Because the diazonium salts are easily decomposed and cause explosions, there is a great safety hazard in the industrial production process, thus limiting the 2,6-diethyl- I...

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Problems solved by technology

[0005] (1) Large potential safety hazards, which limit the increase in production capacity

After the diazotization reaction, there will be a large amount of diazonium salts in the reactor. Since the diazonium salts are easy to decompose and cause explosions, there are great safety hazards in the industrial production process, thus limiting the production of 2,6-diethyl- Increased production capacity of 4-methylbromobenzene

[0006] (2) Large energy consumption and high production cost

In order to ensure safe production, the preparation of diazonium salt needs to be carried out at low temperature (-5°C), which increases energy consumption; at the same time, multiple heating and cooling operations in the production process not only make the operation cumbersome, but also reduce production efficiency

[0007] (3) Low batch operation efficiency and long reaction time

The above method needs to prepare the diazonium salt corresponding to 2,6-diethyl-4-methylaniline first, and then slowly add it dropwise to the bromination reagent for bromination reaction. The process requires the cooperation of multiple reactors Operation, a batch of production often takes many hours, the process operation is cumbersome, the production takes a long time, and the production efficiency is low

[0008] (4) The content of by-products is difficult to control

After the diazonium salt is prepared, due to the higher temperature of the bromination reaction in the next step, it is usually necessary to slowly drop the diazonium salt into the bromination reagent to carry out the bromination reaction. The reaction takes a long time, which easily affects the selectivity of the reaction and makes the by-product content increased

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