A Review on Modern Approaches to Benzimidazole Synthesis.

Cancer is the second most source of cessation of life globally, with 9.6 million expirations at each stage around the globe. The resistance to the current chemotherapies urges researchers to develop new drugs to be available in the market. Among the wide range of drugs synthesized, heterocyclic compounds play a major role due to the abundance of heterocyclic rings in biological substances. In medicinal chemistry, benzimidazole is an important pharmacophore and a privileged structure. This bicyclic compound is made up of the fusion of a six-membered benzene ring and a five-membered imidazole ring with two nitrogen atoms at 1,3-positions. The benzimidazole ring has a great deal of stability. Many strong acids and alkalis do not affect benzimidazoles. The benzene ring of benzimidazole cleaves only under extreme conditions. Except in certain circumstances, the benzimidazole ring is also quite resistant to reduction. It is the most popular nucleus to study because of its wide range of biological functions. The recently developed methods for preparing benzimidazoles, such as condensation of o-phenylene diamines (OPDs) with aldehydes and many others using a wide range of nano, metal-based catalysts under solventfree conditions, are discussed in detail in the current studies.