Solvent Dependent Selectivity in the Synthesis of 1,2‐Disubstituted and 2‐Substituted Benzimidazoles by Dehydrogenative Coupling Reactions with Ruthenium‐Polyoxoniobate Catalysts

Abstract Ruthenium‐polyoxoniobate complexes were found to be efficient catalysts for the selective synthesis of 2‐substituted benzimidazoles and 1,2‐disubstituted benzimidazoles by solvent switching. The current strategy enables the synthesis of 2‐substituted benzimidazoles in water as a green solvent. Switching to aprotic solvents resulted in the formation of 1,2‐disubstituted benzimidazoles as the major product. Control experiments showed the involvement of both acceptorless dehydrogenative and oxidative coupling pathways. The method was extended to synthesize various 2‐substituted and 1,2‐disubstituted benzimidazole derivatives, and the desired products were obtained in moderate to good yields.