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3, 3 5, 4, 4 5 -Biphenyltetracarboxylic dianhydride is a precursor of high・per£ormance material polyimide. This article adopts the method of Grignard reagent coupling to study the synthesis of 3, 3 ', 4, 4 J -biphenyl tetracarb oxy lie dianhydride ・ Firstly, 4 ・brom o・o-xylene reacted w 让h magnesium metal to prepare Grignard reagent・ Secondly, under the action of ferric trifluoromethanesulfonate, the Grignard reagent self-coupled to produce 3, 3 ', 4, 4' -tetramethyl biphenyl, which was oxidized and then dehydrated to ob・ tain 3, 3 '-biphenyl tetracarboxylic dianhydride・ The effects of key factors of the experiments were examined, the optimal reaction conditions of coupling were determined・ The reaction mechanism has been analyzed ・ The results showed that the coupling reaction temperature was 60 °C and the reaction time was 8 h, the yield of 3, 3 ', 4, 4 '・tetramethylbiphenyl reached 83% ・ The yield of 3, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride was 78% ・ Mechanism analysis shows that Grignard reagent undergoes self coupling reaction with iron catalyst and 1, 2-dichloroethane to prepare 3, 3', 4, 4' -tetramethylbiphenyl. [ABSTRACT FROM AUTHOR]