Benzimidazole as Ubiquitous Structural Fragment: An Update on Development of its Green Synthetic Approaches

Benzimidazole and its derivatives are privileged heterocyclic motifs and important building blocks for the development of the biologically active compound. However, several research reports are produced in a short period of time due to the rapid production of new drugs having a benzimidazole nucleus. In order to understand the current status of the benzimidazole nucleus in medicinal chemistry, it is therefore important to combine the latest knowledge with earlier information. Hence, synthetic organic chemists concentrated on inventing an effective green methodology for synthesizing benzimidazole derivatives. In addition to this, non-degradable chemical compounds cause the ecosystem to become fragile, damaged, or irritated as contaminants pose a danger to the environment. However, conventional methods of synthesis need longer heating time, with complicated and tedious apparatus set up, which results in high cost and pollution in contrast to greener methods which are inexpensive. In the present review, we have attempted to shed light on various synthetic strategies leading to the synthesis of different benzimidazole derivatives through the direct condensation reaction between ophenylenediamine and aromatic aldehydes using green chemistry approaches such as mechanochemistry, ultrasound irradiation, microwave irradiation, environmentally benign solvents/catalysts, reactant immobilized on a solid support, and blue light irradiation.