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Abstract

A method for preparing 3,3′-diaminobenzidine, the method comprising the following steps: subjecting 4,4′-biphenol and N,N-dimethylsulfamoyl chloride to an esterification reaction in a specified solvent at 40-70° C. to obtain 4,4′-biphenyl bis(N,N-dimethylaminosulfonate) as a first intermediate; subjecting the 4,4′-biphenyl bis(N,N-dimethylaminosulfonate) to a chlorination reaction with a chlorinating reagent under acidic conditions to obtain 3,3′-dichloro-4,4′-biphenyl bis(N,N-dimethylaminosulfonate) as a second intermediate; subjecting the second intermediate 3,3′-dichloro-4,4′-biphenyl bis(N,N-dimethylaminosulfonate) to an ammonolysis reaction with anammoniation reagent in the presence of a combined catalyst to obtain a crude product of 3,3′,4,4′-tetraaminobiphenyl, wherein the combined catalyst is a mixture of proline, a cuprous salt and a phase transfer catalyst; and subjecting the crude product of 3,3′,4,4′-tetraaminobiphenyl to a post-treatment to obtain a purified 3,3′,4,4′-tetraaminobiphenyl product. In the present invention, 4,4′-biphenol is used as a raw material, a brand-new synthesis route is used, the product purity is high, and pollution of three kinds of waste is reduced.

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