Preparation of 2,3,5,6-tetrafluorobenzyl alcohol

Abstract

The invention discloses a preparation method of 2, 3, 5, 6-phenylcarbinol tetrafluoride; the preparation method is as follows: the 2, 3, 4, 5, 6-cyanobenzene pentafluoride is taken as initial raw material; cyano group is firstly reduced by catalytic hydrogenation, and then diazotization and hydrolysis reaction are carried out for obtaining hydroxide radical, and then contraposition defluorination is carried out for obtaining the 2, 3, 5, 6-phenylcarbinol tetrafluoride; or the 2, 3, 4, 5, 6-cyanobenzene pentafluoride is taken as initial raw material, the contraposition defluorination is carried out for obtaining the 2, 3, 5, 6-cyanobenzene pentafluoride, the hydroxide radical is reduced by the catalytic hydrogenation, and then the diazotization and the hydrolysis reaction are carried out for obtaining the 2, 3, 5, 6-phenylcarbinol tetrafluoride. The two synthetic routes of the invention both comprises the three reaction steps of catalytic hydrogenation, diazotization and hydrolysis and contraposition defluorination; wherein, in the catalytic hydrogenation process, acid is added for obtaining amine salt, and the diazotization and the hydrolysis reaction are carried out by a one pot process, thus leading byproducts to be greatly reduced, the main products to have high purity and the yield coefficient to reach more than 74 percent; in addition, the whole process has simple operation, mild reaction condition and cheap and easily obtained raw material; catalyst and solvent can be recycled and used, thus reducing pollution, being environment-friendly, having economic value and being suitable for industrialization.

Description

(1) Technical field [0001] The invention belongs to the field of synthesis of chemical drug intermediates, in particular to a preparation method of 2,3,5,6-tetrafluorobenzyl alcohol. (2) Background technology [0002] Transfluthrin (transfluthrin) is a pyrethrin insecticide developed and produced by German Bayer Company in the 1980s. It is mainly used for the prevention and control of sanitary pests, and has the effect of quickly striking and killing. At present, few domestic manufacturers produce it, and it is a pyrethroid pesticide with great market prospects. 2,3,5,6-Tetrafluorobenzyl alcohol is an important intermediate in the synthesis of the pyrethroid insecticide transfluthrin. Therefore, the synthesis of 2,3,5,6-tetrafluorobenzyl alcohol has become an important research topic. The structural formula of 2,3,5,6-tetrafluorobenzyl alcohol is as follows, [0003] [0004] 2,3,5,6-Tetrafluorobenzyl alcohol [0005] 2,3,5,6-Tetrafluorobenzyl alcohol is mainly obtain...

AI Technical Summary

Problems solved by technology

[0023] The route uses organic tertiary amines (such as N,N-dimethylbenzylamine) and metal chloride salts as catalysts in methanol to reduce 2,3,5,6-tetrafluorobenzoic acid with sodium borohydride To obtain 2,3,5,6-tetrafluorobenzyl alcohol, the use of sodium borohydride and metal chlorides increases the cost, while the use of organic tertiary amines increases the pollution to the environment

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