Metal-Free Ionic-Liquid-Mediated Synthesis of Benzimidazoles and Quinazolin-4(3H)-ones from Benzylamines

An expedient metal-free synthetic protocol for the construction of benzimidazoles has been developed from o-phenylenediamine and benzylamine, using an imidazolium-based ionic liquid as the reaction medium. The reactions proceed by oxidation of benzylamine derivatives to their corresponding imines, followed by intramolecular cyclization, to yield benzimidazoles. Advantages of this method include: an environmentally friendly metal-free process, recyclable reaction media, high yields, short reaction times, and the applicability for the synthesis of quinazolin-4(3H)-ones. An NMR spectroscopy study provided further insight into the reaction.