Zeolite imidazolate frameworks in catalysis: Synthesis of benzimidazoles via cascade redox condensation using Co-ZIF-67 as an efficient heterogeneous catalyst

Zeolite imidazolate framework Co-ZIF-67 was synthesized and utilized as a recyclable catalyst for the synthesis of benzimidazoles via the cascade redox condensation of 2-nitroanilines with benzylamines without added oxidizing or reducing agents. The Co-ZIF-67 catalyst expressed better performance in the generation of benzimidazoles than many MOFs and many conventional homogeneous catalysts. The transformation progressed via genuinely heterogeneous catalysis, and the formation of benzimidazoles via homogeneous catalysis due to the leaching phenomenon, if any, was not considerable. The cobalt-based framework catalyst could be reutilized many times for the reaction without losing its efficiency. The fact that the cascade redox condensation could proceed readily with a recyclable catalyst while additional reducing or oxidizing agents were not required would outperform previous synthetic protocols. To the best of our knowledge, this is the first heterogeneous catalytic approach to achieve benzimidazoles via the cascade redox condensation of 2-nitroanilines with benzylamines.