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Open AccessReview

Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles

1
School of Chemistry, National University of Ireland Galway, University Road, H91 TK33 Galway, Ireland
2
Department of Pharmacy, School of Life Sciences, Pharmacy and Chemistry, Kingston University, Penrhyn Road, Kingston upon Thames KT1 2EE, UK
*
Author to whom correspondence should be addressed.
Academic Editor: Farid Chemat
Molecules 2021, 26(9), 2684; https://doi.org/10.3390/molecules26092684
Received: 9 April 2021 / Revised: 1 May 2021 / Accepted: 3 May 2021 / Published: 4 May 2021
(This article belongs to the Special Issue Synthetic Heterocyclic Chemistry)
This review article provides a perspective on the synthesis of alicyclic and heterocyclic ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles, and imidazo[5,4-f]benzimidazoles. These heterocycles have a plethora of biological activities with the iminoquinone and quinone derivatives displaying potent bioreductive antitumor activity. Synthesis is categorized according to the cyclization reaction and mechanisms are detailed. Nitrobenzene reduction, cyclization of aryl amidines, lactams and isothiocyanates are described. Protocols include condensation, cross-dehydrogenative coupling with transition metal catalysis, annulation onto benzimidazole, often using CuI-catalysis, and radical cyclization with homolytic aromatic substitution. Many oxidative transformations are under metal-free conditions, including using thermal, photochemical, and electrochemical methods. Syntheses of diazole analogues of mitomycin C derivatives are described. Traditional oxidations of o-(cycloamino)anilines using peroxides in acid via the t-amino effect remain popular. View Full-Text
Keywords: green chemistry; halogen; heterocycle; hydrogen peroxide; imidazole; iodine; nitrosobenzene; oxone; palladium; quinone green chemistry; halogen; heterocycle; hydrogen peroxide; imidazole; iodine; nitrosobenzene; oxone; palladium; quinone
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MDPI and ACS Style

Sweeney, M.; Conboy, D.; Mirallai, S.I.; Aldabbagh, F. Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles. Molecules 2021, 26, 2684. https://doi.org/10.3390/molecules26092684

AMA Style

Sweeney M, Conboy D, Mirallai SI, Aldabbagh F. Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles. Molecules. 2021; 26(9):2684. https://doi.org/10.3390/molecules26092684

Chicago/Turabian Style

Sweeney, Martin; Conboy, Darren; Mirallai, Styliana I.; Aldabbagh, Fawaz. 2021. "Advances in the Synthesis of Ring-Fused Benzimidazoles and Imidazobenzimidazoles" Molecules 26, no. 9: 2684. https://doi.org/10.3390/molecules26092684

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