In the past decade, transition-metal-catalyzed functionalization of unactivated C–H bonds has emerged as a powerful approach to forging C–C bonds, especially for palladium, ruthenium, iridium and copper. Recently, Rh(III) complexes have presented their advantages in the step-economical synthesis of complex molecular scaffolds. Although a large amount of rhodium(III)-catalyzed functionalization of C–H bonds have been well documented, ligand promoted Rh(III)-catalyzed C–H activation remain relatively rare. Considering the impact of ligand development on Pd(II) catalyzed C–H functionalization reactions, it is reasonable to assume that the use of proper ligands could accelerate C(sp2)–H cleavage and promote the subsequent C–C or C–N bond formation step by potentially tuning the steric and electronic properties of the active catalyst. Notably, ligand scaffolds for Rh(III) catalysts are largely limited to cyclopentadienyl (Cp) motifs. To identify new ligand scaffolds for Rh(III) catalysts, series of amino acids, phosphines and pyridine-based ligands were tested for their efficiency of promoting C(sp2)–H olefination, arylation and amination, respectively, in our group. The significant enhancement observed with the ligands provides a new lead for ligand design in Rh(III)-catalyzed C–H activation reactions.

Ligand-promoted rhodium(III)-catalyzed <i>ortho</i>-C–H functionalization

255th National Meeting (2018)

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Ligand-promoted rhodium(III)-catalyzed ortho-C–H functionalization