US 11,981,616 B2
Method for preparing 3,3′-diaminobenzidine
Yun Ling, Beijing (CN); Yongfang Li, Beijing (CN); Kun Wang, Beijing (CN); Lizhu Chen, Beijing (CN); Wei Yin, Beijing (CN); and Jinying Zhang, Beijing (CN)
Assigned to Hubei Huida High-Tech Co., Ltd, Jingzhou (CN); and Borun High-Tech Co., Ltd., Beijing (CN)
Appl. No. 18/552,016
Filed by HUBEI HUIDA HIGH-TECH CO., LTD., Hubei (CN); and BORUN HIGH-TECH CO., LTD., Beijing (CN)
PCT Filed Jan. 12, 2022, PCT No. PCT/CN2022/071586
§ 371(c)(1), (2) Date Sep. 22, 2023,
PCT Pub. No. WO2022/199226, PCT Pub. Date Sep. 29, 2022.
Claims priority of application No. 202110308372.0 (CN), filed on Mar. 23, 2021.
Prior Publication US 2024/0109835 A1, Apr. 4, 2024
Int. Cl. C07C 209/68 (2006.01); C07C 209/22 (2006.01); C07C 209/84 (2006.01)
CPC C07C 209/22 (2013.01) [C07C 209/84 (2013.01)] 10 Claims
 
1. A method for preparing 3,3′-diaminobenzidine, comprising:
step S1: subjecting 4,4′-biphenol and N,N-dimethylsulfamoyl chloride to an esterification reaction in a first solvent at 40-70° C. to obtain 4,4′-biphenyl bis(N,N-dimethylaminosulfonate) as a first intermediate;
step S2: 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;
step S3: subjecting the second intermediate 3,3′-dichloro-4,4′-biphenyl bis(N,N-dimethylaminosulfonate) to an ammonolysis reaction with an ammoniation reagent in the presence of a combined catalyst to obtain a crude product of 3,3′-diaminobenzidine, wherein the combined catalyst is a mixture of proline, a cuprous salt and a phase transfer catalyst; and
step S4: subjecting the crude product of 3,3′-diaminobenzidine to post-treatment to obtain a purified product of 3,3′-diaminobenzidine.