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

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 NH2OH·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.