Improved method for preparing 4-cyanobiphenyl

Abstract

The invention relates to a method for preparing 4-cyanobiphenyl. The method comprises the following steps of: (1) carrying out Friedel-Craft reaction on N-methylamino formyl chloride and biphenyl in the presence of a lewis acid catalyst to obtain N-methyl-4-biphenyl formamide; (2) removing methanol from N-methyl-4-biphenyl formamide in the presence of a catalyst to obtain a target product. The method disclosed by the invention has the advantages that N-methylamino formyl chloride instead of trichloro-acetic chloride adopted in the prior art to react with biphenyl, so that the step of necessarily separating and purifying a reaction medium obtained after each batch of chloroform is reacted in the prior art is not needed and the operating cost is lowered. In addition, raw materials are low in cost and easy to obtain, a reaction process is easy to control, and a product can reach the yield of 70% or more than 70% by being recrystallized and can be directly used for producing C.I. pigment red 264.

Description

technical field [0001] The invention relates to a method for preparing 4-biphenylnitrile. Background technique [0002] 4-Biphenonitrile is a key intermediate in the production of pigments (C.I. Pigment 264). Regarding the synthesis of 4-biphenylnitrile, literature has reported multiple methods, briefly described as follows: [0003] 1) Biphenyl diazonium salt - cyanide method : Biphenyl is sequentially nitrated with mixed acid, reduced (to obtain 4-aminobiphenyl), diazotized (diazonium salt generated) and reacted with sodium cyanide to obtain 4-biphenylnitrile (Mettler HP, patent No.: DE19833409( 1998-12-24)). In this method, two intermediate products (4-nitrobiphenyl and 4-aminobiphenyl) are carcinogenic, and the sodium cyanide used is highly toxic, so it is harmful to the operator during the production process. Detrimental to physical and mental health. [0004] 2) Biphenyl bromination-cyanide method : Biphenyl is brominated to obtain 4-bromobiphenyl, which reacts ...

AI Technical Summary

Problems solved by technology

The defect that this method exists is: the price of harsh reaction condition and used catalyst is expensive, so that this method does not have commercial value at present

The disadvantage of this method is: the preparation steps are tedious, although the yield of each step reaction is not low, the total yield is not high, so that the method has lost its economic value

But this method also has a shortcoming, that is, although the result of chloroform reaction has generated biphenylamide, chloroform has also been generated at the same time, because the medium used for carrying out this reaction is dichloroethane, chloroform just remains in dichloroethane like this. However, dichloroethane containing chloroform cannot be directly used in the Friedel-Crafts reaction between biphenyl and trichloroacetyl chloride, and the reaction medium after each batch of chloroform reaction must be separated and purified, which obviously increases the 4-linkage Production cost of benzonitrile

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