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NaI-Mediated Electrochemical Cyclization-Desulfurization for the Synthesis of N-Substituted 2-Aminobenzimidazoles

Khuyen Thu Nguyen, Thao Nguyen Thanh Huynh, Kanisorn Ratanathawornkiti, Methasit Juthathan, Patchanita Thamyongkit, Mongkol Sukwattanasinitt, Sumrit Wacharasindhu*

*Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand, Email: sumrit.wchula.ac.th

K. T. Nguyen, T. N. T. Huynh, K. Ratanathawornkiti, M. Juthathan, P. Thamyongkit, M. Sukwattanasinitt, S. Wacharasindhu, J. Org. Chem., 2024, 89, 1591-1601.

DOI: 10.1021/acs.joc.3c02212


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Abstract

A NaI-mediated electrochemical desulfurization-cyclization of N-substituted o-phenylenediamines and isothiocyanates provides N-substituted 2-aminobenzimidazoles. The cost-effective NaI acts as both a mediator and an electrolyte in a catalytic amount (0.2 equiv), replacing traditional oxidizing reagents. At gram-scale, the reaction efficiency is maintained.


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Details

The article discusses an electrochemical method for synthesizing N-substituted 2-aminobenzimidazoles using a NaI-mediated desulfurization-cyclization process. This method employs NaI as both a mediator and an electrolyte in a catalytic amount, replacing traditional oxidizing reagents. The process involves N-substituted o-phenylenediamines and isothiocyanates undergoing thiourea formation, cyclization, and desulfurization in a single reaction vessel, achieving up to 98% yield. The method is applicable to gram-scale synthesis and offers advantages such as cost-effectiveness, eco-friendly solvents, and operation at ambient temperature. The study highlights the importance of 2-aminobenzimidazole derivatives in drug discovery, with applications in antihistamines and NF-κB inhibitors. The electrochemical approach is presented as a sustainable alternative to traditional methods, providing high selectivity and mild reaction conditions. The article also details the optimization of reaction conditions, including the use of different electrodes, current intensities, and solvents. The method's scalability and potential for large-scale production are demonstrated, along with insights into the reaction mechanism through control experiments and cyclic voltammetry. The study concludes that the electrochemical process is efficient, scalable, and environmentally friendly for synthesizing N-substituted 2-aminobenzimidazoles.


Key Words

benzimidazoles, electrochemistry


ID: J42-Y2024