Recent Advances in C–H Bond Functionalization with Ruthenium-Based Catalysts

The past decades have witnessed rapid development in organic synthesis via catalysis, particularly the reactions through C⁻H bond functionalization. Transition metals such as Pd, Rh and Ru constitute a crucial catalyst in these C⁻H bond functionalization reactions. This process is highly attractive not only because it saves reaction time and reduces waste,but also, more importantly, it allows the reaction to be performed in a highly region specific manner. Indeed, several organic compounds could be readily accessed via C⁻H bond functionalization with transition metals. In the recent past, tremendous progress has been made on C⁻H bond functionalization via ruthenium catalysis, including less expensive but more stable ruthenium(II) catalysts. The ruthenium-catalysed C⁻H bond functionalization, viz. arylation, alkenylation, annulation, oxygenation, and halogenation involving C⁻C, C⁻O, C⁻N, and C⁻X bond forming reactions, has been described and presented in numerous reviews. This review discusses the recent development of C⁻H bond functionalization with various ruthenium-based catalysts. The first section of the review presents arylation reactions covering arylation directed by N⁻Heteroaryl groups, oxidative arylation, dehydrative arylation and arylation involving decarboxylative and sp3-C⁻H bond functionalization. Subsequently, the ruthenium-catalysed alkenylation, alkylation, allylation including oxidative alkenylation and meta-selective C⁻H bond alkylation has been presented. Finally, the oxidative annulation of various arenes with alkynes involving C⁻H/O⁻H or C⁻H/N⁻H bond cleavage reactions has been discussed