Metal-Free Synthesis of Benzimidazoles via Oxidative Cyclization of D-Glucose with o-Phenylenediamines in Water

D-Glucose has been identified as an efficient C1 synthon in the synthesis of benzimidazoles from o-phenylenediamines via an oxidative cyclization strategy. Isotopic studies with C-13(6)-D-glucose and D2O unambiguously confirmed the source of methine. The notable features of this method include the following: broad functional group tolerance, a biorenewable methine source, excellent reaction yields, a short reaction time, water as an environmentally benign solvent, and the synthesis of vitamin B-12 component on the gram scale.