Preparation method of 3,4,5-trifluoroaniline

Abstract

The invention relates to a preparation method of 3,4,5-trifluoroaniline. The preparation method comprises the following steps: (1) dispersing 3,4,5-trifluoro nitro benzene into water, adding a catalyst, and heating in a hydrogen atmosphere for reaction, so as to obtain a crude product, wherein the catalyst is a mixture of ruthenium carbon and tetrabutylammonium fluoride in a mass ratio of (1.8-2.2) to 1, and ruthenium carbon is counted based on 5% carbon-loaded ruthenium; and (2) extracting the crude product by virtue of dichloromethane, and carrying out primary reduced pressure rectificationon an organic phase, so as to obtain 3,4,5-trifluoroaniline. According to the synthesis method provided by the invention, a specific catalyst is selected, so that the generation of fluorine-generatingimpurities in the process of preparing 3,4,5-trifluoroaniline through 3,4,5-trifluoro nitro benzene can be reduced, and the purity of 3,4,5-trifluoroaniline is improved; and particularly, when the catalyst is the mixture of ruthenium carbon and tetrabutylammonium fluoride in a mass ratio of 2 to 1 and the plate number in every 50g of 3,4,5-trifluoroaniline on a rectifying tower is 1000-2000, thepurity of 3,4,5-trifluoroaniline is 99% or above.

Description

technical field [0001] The invention belongs to the field of intermediate synthesis, and in particular relates to a preparation method of 3,4,5-trifluoroaniline. Background technique [0002] 3,4,5-Trifluoroaniline is an important raw material for the preparation of liquid crystal materials. 3,4,5-Trifluoroaniline can be prepared through a series of reactions such as diazotization, bromination, Grignard reaction, boration, etc., to prepare 3,4 ,5-Trifluorophenylboronic acid. Raw materials for liquid crystal materials, in order to ensure the purity of liquid crystal materials, have very strict requirements on congeners. Generally, the impurities of congeners are required to be less than 50ppm. Therefore, it is necessary to control the impurities of congeners from the raw materials used in each step. [0003] 3,4,5-trifluoronitrobenzene, through nitro reduction to prepare 3,4,5-trifluoroaniline, there are many methods, which can be reduced by iron powder (this method has too ...

AI Technical Summary

Problems solved by technology

[0003] 3,4,5-trifluoronitrobenzene, through nitro reduction to prepare 3,4,5-trifluoroaniline, there are many methods, which can be reduced by iron powder (this method has too much waste water, and the country has banned the use of iron powder for nitration base reduction), and methods such as palladium carbon reduction, nickel reduction, ruthenium reduction, and platinum reduction can also be used, but the method cannot be carried out for fluorine removal by-products (such as m-difluoroaniline, o-difluoroaniline, monofluoroaniline, etc.) Effective control

[0004] In the prior art, there is no effective means to suppress the occurrence of by-products of fluorine removal