Preparation of 4-bromo-2,6-difluorobenzonitrile

Abstract

The invention discloses a preparation method of 4-bromo-2, 6-difluorobenzonitrile. In the preparation method, tetrahydrofuran, potassium tert butoxide, petroleum ether, 3, 5-difluorobromobenzene, DMF and n-butyllithium with the proportion of n-butyllithium: 3, 5-difluorobromobenzene, which is equal to 1.2:1 and the proportion of DMF: 3, 5-difluorobromobenzene, which is equal to1.6:1 are taken as raw materials to produce 4-bromo-2, 6-difluorobenzaldehyde, and methanoic acid, 4-bromo-2, 6-difluorobenzaldehyde and hydroxylamine hydrochloride with the weight ratio of the methanoic acid, the 4-bromo-2, 6-difluorobenzaldehyde and the hydroxylamine hydrochloride equal to 4:1:1.4 are taken as raw materials to prepare the 4-bromo-2, 6-difluorobenzonitrile. The preparation steps of the 4-bromo-2, 6-difluorobenzonitrile are as follows: A: the raw materials are added to a three-necked flask according to the proportion, and are heated and refluxed for 10 hours at normal pressure; B: a solvent is distilled at normal pressure, then corresponding volume of water is added to the system to continuously distill, and the 4-bromo-2, 6-difluorobenzonitrile is carried out; and C: the distilled aqueous solution is naturally cooled to the room temperature and is carried out suction filtration; a filter cake is washed with water to be neutral, and the product is obtained. The method for preparing the 4-bromo-2, 6-difluorobenzonitrile of the invention takes the 3, 5-difluorobromobenzene as a basic raw material which is cheap, and the whole process engineering is low in cost, so the 4-bromo-2, 6-difluorobenzonitrile is applicable to mass production. The preparation method does not adopt the hypertoxic potassium cyanide and strong corrosive substances such as sulfuric acid, bromine, and the like, which are adopted in the existing process, thus reducing the environmental pollution.

Description

technical field [0001] The invention relates to a preparation method of an intermediate compound of a liquid crystal compound, belonging to the field of chemical industry. Background technique [0002] The chemical formula of 4-bromo-2,6-difluorobenzonitrile is [0003] [0004] It is an intermediate compound widely used in the preparation of liquid crystal materials. At present, it generally uses 2,6-difluoroaniline as raw material to synthesize liquid crystal intermediate 4-bromo-2,6-difluorobenzonitrile through bromination diazotization and sandermer reaction. Its reaction formula is generally as follows: [0005] [0006] The technical process in the above-mentioned reaction formula is complicated, and bromine, potassium cyanide, and concentrated sulfuric acid are used in the raw materials. They not only have extremely strong corrosiveness, but also have high toxicity, serious environmental pollution during production, and low yield and high cost. high. Conten...

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Problems solved by technology

[0006] The technical process in the above-mentioned reaction formula is complicated, and bromine, potassium cyanide, and concentrated sulfuric acid are used in the raw materials. They not only have extremely strong corrosiveness, but also have high toxicity, serious environmental pollution during production, and low yield and high cost. high

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