Catalyst-free, One-pot Synthesis of 2-Aryl Benzimidazoles from Orthophenylenediamine and Aryl Aldehyde in Acetonitrile

Aim: The study aims to optimize and synthesize benzimidazole derivatives. Background: Benzimidazoles are essential intermediates and scaffolds for biological activity and drug substances. The reported syntheses of benzimidazoles suffer from disadvantages like longer reaction time using a catalyst, which makes the method costly, and the use of strong corrosive acids and toxic reagents that increase environmental hazards. Objectives: One-pot synthesis of 2-aryl benzimidazole from ortho-phenylenediamine and aryl aldehyde. Method: Herein disclosed a catalyst-free, one-pot synthesis of 2-aryl benzimidazole. Results: Different 2-aryl benzimidazoles were synthesized in good yields via the condensation reaction of aryl aldehyde and ortho-phenylenediamine in acetonitrile as a solvent at room temperature. The method is very simple and convenient, with good yields. The formation of the desired product is affected by the substituent of aryl aldehydes. Electron donating substituents are shown to have a higher time in the completion of a reaction than electron-withdrawing substituents. Conclusion: One-pot synthesis of benzimidazole was found to be simpler and economical.