Recent Developments in Ruthenium-Catalyzed C-H Arylation: Array of Mechanistic Manifolds

Functionalized biaryl-containing motifs are among the most valuable synthetic scaffolds in organic chemistry with wide ranging commercial applications in pharmaceuticals, functional materials, and agrochemicals. Recently, there has been tremendous progress in the development of methods for functional-group-tolerant, cost-effective, and atom-economic ruthenium-catalyzed C-H arylation, providing attractive catalytic alternatives to traditional C-H functionalization and cross-coupling approaches. New ruthenium-catalyzed C-H arylation reactions have resulted in the development of attractive and highly efficient synthetic approaches to functionalized biaryls unavailable by other methods. New mechanistic manifolds have emerged, thus opening prospects for the development of a broad range of novel reactions. Strategies for the use of ruthenium catalysis in complex synthesis, including industrial applications, have been reported, validating the synthetic potential of this mode of reactivity. The development of new catalysts, availability of ruthenium complexes in multiple oxidation states, and efficiency of various catalytic cycles allow for C-H arylation strategies that have been difficult to achieve by using other metals. Herein, we discuss the most recent advances in ruthenium-catalyzed C-H arylation, with a focus on both mechanistic aspects and synthetic utility.