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 sp(3)-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.