Method for preparing 2,6-diethyl-4-methyl bromobenzene

Abstract

The invention discloses a method for continuous flow preparation of 2,6-diethyl-4-methyl bromobenzene. A whole preparation process is performed in an integrated reactor, a nitrite reagent, alcohol andacid are continuously added to a charging opening of the integrated reactor to prepare nitrite, then, the nitrite is subjected to a diazotization reaction with 2,6-diethyl-4-methylaniline, the obtained diazo salt is then subjected to a bromation reaction with a bromination reagent, and the 2,6-diethyl-4-methyl bromobenzene is continuously obtained from a discharging opening of the integrated reactor. According to the method, the production process is safe and efficient, the accumulation of high-risk diazo salts is not caused, the problem that a reactor type reaction system is high in viscosity is solved, the yield and purity of product are relatively high, and the technological operation is simple and efficient.

Description

technical field [0001] The invention relates to a preparation method of a pesticide intermediate, 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 of the herbicide pinoxaden. [0003] CN109134187A, CN106928253A, CN102395546A, and CN108864144A all reported that 2,6-diethyl-4-methylaniline was first diazotized and then brominated to prepare 2,6-diethyl-4- Methyl bromide method. [0004] These methods have the following significant disadvantages: [0005] (1) There are many potential safety hazards, which limit the increase in production capacity. After the diazotization reaction, there will be a large amount of diazonium salts accumulated in the reaction kettle. 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- T...

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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 accumulated in the reaction kettle. 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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