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Ultrasound-assisted one-pot cyclization for the synthesis of 2-substituted benzimidazole derivatives: A rapid access via NaOH/I2 as an efficient oxidant system
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1 Department of Chemistry, Catalysis Division, Faculty of Organic Chemistry, University of Isfahan, Isfahan,
Iran
JES, 025280012 https://doi.org/10.36922/JES025280012
Received: 7 July 2025 | Revised: 30 August 2025 | Accepted: 15 September 2025 | Published online: 7 October 2025
© 2025 by the Author(s). This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ )
Abstract
Benzimidazole scaffolds represent an important class of heterocyclic compounds due to their wide range of pharmacological and industrial applications. An efficient, metal-free, and operationally simple protocol for the synthesis of 2-substituted benzimidazoles via an ultrasound-assisted one-pot cyclization of aromatic aldehydes and o-phenylenediamine is reported. The method employs NaOH/I₂ as an inexpensive and effective oxidant system under mild conditions at room temperature. This approach addresses the limitations of conventional methods, which often require transition-metal catalysts, hazardous oxidants, prolonged heating, and produce lower yields. In the present study, reactions were completed within 4–7 min, affording the desired products in yields up to 99% across a broad substrate scope. Control experiments demonstrated the beneficial role of ultrasonic irradiation, and a plausible mechanism was proposed. The combination of mild reaction conditions, short reaction times, and high efficiency highlights the potential of this method as a green and scalable alternative for benzimidazole synthesis.
Graphical abstract
Keywords
2-Substituted benzimidazole
Ultrasound-assisted synthesis
NaOH/I2 oxidant
One-pot reaction
Metal-free protocol
Green chemistry
Funding
None.
Conflict of interest
The author declares no conflict of interest.
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