Mesoporous mixed metal oxide nanocrystals: Efficient and recyclable heterogeneous catalysts for the synthesis of 1,2-disubstituted benzimidazoles and 2-substituted benzothiazoles

Present communication elicits the use of mesoporous mixed metal oxide nanocrystals of Al2O3–Fe2O3, Al2O3–V2O5 and Al2O3–CuO as heterogeneous catalysts for the preparation of series of medicinally significant 1,2-disubstituted benzimidazoles and 2-substituted benzothiazoles. These nanocrystalline catalysts exhibited remarkable catalytic activity with a high substrate to catalyst weight ratio (20:1) to achieve the synthetic targets in the range of yield 81–96%. The solvent-free microwave assisted synthesis of these compounds was an advantageous way which resulted in excellent yields in much lesser time (0.75–1.5 min) in comparison to conventional heating. The use of catalyst in eco-friendly green protocol and its reusability up to four cycles with similar catalytic response are the unique features of the heterogeneous catalysis. This protocol provided greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yields.

Graphical abstractPresent communication elicits the use of mesoporous mixed metal oxide nanocrystals of Al2O3–Fe2O3, Al2O3–V2O5 and Al2O3–CuO as heterogeneous catalysts for the preparation of series of medicinally significant 1,2-disubstituted benzimidazoles and 2-substituted benzothiazoles. These nanocrystalline catalysts exhibited remarkable catalytic activity with a high substrate to catalyst weight ratio (20:1) to achieve the synthetic targets in the range of yield 81–96%. The solvent-free microwave assisted synthesis of these compounds was an advantageous way which resulted in excellent yields in much lesser time (0.75–1.5 min) in comparison to conventional heating. The use of catalyst in eco-friendly green protocol and its reusability up to four cycles with similar catalytic response are the unique features of the heterogeneous catalysis. This protocol provided greater selectivity, cost-efficiency, clean reaction profiles, simple work-up procedure and high yields.Figure optionsDownload full-size imageDownload high-quality image (219 K)Download as PowerPoint slideHighlights► Synthesis of benzimidazoles and benzothiazoles using mixed metal oxide nanocatalyst. ► Catalyst characterization was performed by XRD, SEM and N2 BET analysis. ► High substrate/catalyst weight ratio, reusability are unique properties of catalyst. ► Catalyst with microwave heating was helpful in reducing time and increasing yields. ► Other features are cost-effective, clean reaction, simple work-up and high yields.