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New insights into bromination process: effective preparation of Ambroxol

Jun-Hui Xu, Yan-Qiong Ma, Jian-Ping Wei, Fang-Mei Li, and Xin-Hua Peng

School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China



Abstract: Ambroxol used as an expectorant in treating respiratory diseases was effectively prepared with a total yield of 62 %, with o-toluidine as the feedstock via successive procedures of electrophilic bromination, acetylation, radical benzylic bromination, N-alkylation and hydrolysis processes. The addition of aqueous hydrogen peroxide could enhance the utilisation of liquid bromine in the electrophilic bromination of o-toluidine, avoiding the hazardous HBr generated as a by-product. In addition, liquid bromine promoted by MnO2 was used efficiently for the radical benzylic bromination of N-acetyl-N-(2,4-dibromo-6-methylphenyl)acetamide under mild conditions.

Keywords: Ambroxol – electrophilic bromination – radical benzylic bromination – total synthesis

Full paper is available at

DOI: 10.1515/chempap-2015-0077


Chemical Papers 69 (5) 722–728 (2015)

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