制备2,2′,4,4′-联苯四甲酸的新方法

A Novel Synthetic Method for 2,2′,4,4′-Tetra Carboxylic Acid Biphenyl

以对甲苯胺为原料研究了2,2′,4,4′-联苯四甲酸的新合成路线。首先由对甲苯胺经三步反应制备了2-氨基-5-甲基苯甲酸,对工艺条件进行了优化,明显地减少了试剂的用量,三步收率达61.5%;2-氨基-5-甲基苯甲酸经重氮化反应、重氮盐偶联反应得到4,4′-二甲基-2,2′-联苯二甲酸,NaOH和NH2OH.HC l的摩尔投料比为1∶1时偶联反应收率最高可达到88%;在弱碱性条件下以KMnO4氧化二甲基联苯二甲酸得到最终产物,以对甲苯胺计算总收率为43.3%。产物结构经1H NMR和IR测试技术确证。以羧酸芳烃重氮盐为反应物制备联苯四甲酸的工艺路线,反应条件温和,收率较高。

A novel method for the synthesis of 2,2＇ ,4,4＇-tetra carboxylic acid biphenyl with p-methyl aniline as raw material is described in this article. Firstly, 2-amino-5-methylbenzoic acid was prepared from p-methyl aniline in three steps with a yield of 61.5%. The process was optimized and the quantities of the reactants were reduced remarkably. Then, 4,4＇-dimethyl-2,2＇-diphenylic acid was obtained by the coupling of diazonium which was made by the diazotization of 2-amino-5-methylbenzoic acid. The effect of molar ratio of NaOH to NH2 OH·HCl on the yield was researched. It was found that the maximum yield of 4,4＇-dimethyl-2,2＇-diphenylic acid was 88% when the molar ratio was 1： 1. Finally, the target product 2,2＇ ,4,4＇-tetra carboxylic acid biphenyl was prepared from the oxidation of 4,4＇-dimethyl-2,2＇-diphenylic acid by KMnO4 in an alkaline solution. Total yield based on p-methyl aniline was 43.3 %. The structure of the product was characterized by ^1H NMR and IR （KBr）. By using benzoic diazonium as a reactant, this synthetic route for tetra carboxylic biphenyl uses mild reaction condition, with high yields and good industrial application potential.