Catalyst-free synthesis of substituted benzimidazoles and benzothiazoles in a sustainable solvent

A catalyst-free synthesis of various 2-alkyl or aryl-substituted benzothiazoles and benzimidazoles has been developed at room temperature by simply combining alkyl or arylaldehydes with ortho-phenylenediamines and 2-aminothiophenols, respectively. The synthesis of these widely applicable fused heterocycles is often challenging and requires additives. The advantages of this new benign procedure include: products with nearly quantitative yields, high atom economy and no toxic waste formation, catalyst-free process with no need for catalyst separation and/or recycling, the use of a green and sustainable solvent, ethanol, and mostly room temperature reactions with moderate reaction times to ensure that the protocol is energetically favorable.