An Insight into the Recent Synthetic Approaches of Benzimidazole Motifs Based on Divergent Substrate Scope

Abstract

Abstract: Simple heterocyclic moieties are quite famous in synthetic organic chemistry due to their bioavailability, ease of laboratory synthesis, and variety of applications in multidisciplinary fields. Benzimidazole is an N-containing benzofused chemical compound with the formula C7H6N2 and belongs to the family of heterocyclic aromatic organic compounds. It is a potent bioactive molecule with prominent therapeutic activities and found to have prior importance in medicinal chemistry. Several advanced investigations in this area also proved that benzimidazole and its derivatives have significant antimicrobial, antiparasitic, antifungal, and anti-carcinogenic activities. It has also gained popularity in material science as well. Because of its versatile applications, numerous research groups paid considerable attention towards the synthesis of benzimidazoles. o-Phenylenediamine (OPD) is considered as the traditional substrate for benzimidazole synthesis. In this review, we discussed the synthetic approaches of benzimidazoles from OPD as a primary reactant with diverse substrates like aldehydes, alcohols, carboxylic acids/esters, etc. We have also briefed up reactions which uses the primary substrates such as o-nitroanilines and o-dinitro benzenes. This review report covers research findings which are published from 2016 till date and describes numerous practical and greener methods of synthesis. It also narrates innovative biocatalysts, photocatalysts and nano-catalysts, which are used for the synthesis of benzimidazoles.