Abstract
The exploitation and use of alternative synthetic methods, in the face of classical procedures that do not conform to the ethics of green chemistry, represent an ever-present problem in the pharmaceutical industry. The procedures for the synthesis of benzimidazoles have become a focus in synthetic organic chemistry, as they are building blocks of strong interest for the development of compounds with pharmacological activity. Various benzimidazole derivatives exhibit important activities such as antimicrobial, antiviral, anti-inflammatory, and analgesic activities, and some of the already synthesized compounds have found very strong applications in medicine praxis. Here we report a selective and sustainable method for the synthesis of 1,2-disubstituted or 2-substituted benzimidazoles, starting from o-phenylenediamine in the presence of different aldehydes. The use of deep eutectic solvent (DES), both as reaction medium and reagent without any external solvent, provides advantages in terms of yields as well as in the work up procedure of the reaction.
Highlights
Among the heterocyclic pharmacophores, the benzimidazole ring is one of the most widespread systems in nature
Choline chloride is one of the most commonly used hydrogen bond acceptors (HBA) used for the formation of deep eutectic solvent (DES) [56] and its combination with a suitable hydrogen bond donors (HBDs) produces eutectic mixtures that are liquid at ambient temperature and have unusual solvent properties [57]
Biodegradable, nontoxic, and even edible quaternary salt that can be extracted from biomass or synthesized from fossil reserves
Summary
The benzimidazole ring is one of the most widespread systems in nature. It is indicated as a “privileged nucleus” due to its occurrence in molecules essential for the life cycle of organisms [1]. Bioactive compounds with a benzimidazole nucleus are heterogeneous molecules in structure and activity. This diversification is to be found in the derivatization of the basic core, followed by a structure–activity relationship for each compound. The first example of a clinically available benzimidazole-based drug is thiabendazole, capable of acting as a fungicide and antiparasitic [3]. Many other derivatives have been developed: The antihistamine Clemizole, the anti-ulcerative
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