Role of graphene oxide as a heterogeneous acid catalyst and benign oxidant for synthesis of benzimidazoles and benzothiazolesElectronic supplementary information (ESI) available. See DOI: 10.1039/c5ra19066e

• Main Authors: Dhopte, Kiran B, Zambare, Rahul S, Patwardhan, Anand V, Nemade, Parag R
• Format: Journal Article
• Published: 20.01.2016
• ISSN: 2046-2069
• DOI: 10.1039/c5ra19066e

We report the synthesis of benzothiazoles and benzimidazoles using graphene oxide as an effective catalyst with good yields and easy recyclability. Graphene oxide plays the dual role of a metal-free acid catalyst and an oxidizing agent. The mechanism of action of graphene oxide as a catalyst was confirmed using X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. Good yields were obtained at 60 °C as well as under ultrasonic irradiation at 35 °C with methanol as the solvent. Additionally, this is also the first report in which the regeneration of partially-reduced spent graphene oxide has been carried out to restore the oxygen containing functional groups and provide a path for the reuse of graphene oxide as the catalyst and oxidizing agent. Graphene oxide plays a dual role as active metal-free acid catalyst and as non-toxic oxidant for benzothiazole and benzimidazole synthesis. Isolated partially reduced graphene oxide was re-oxidized to regenerate the catalyst and restore its activity.