Ruthenium-Catalyzed C-H Alkenylation of Phosphines: Reaction Development, Mechanistic Studies, and Applications to Ligand Design.

A general and efficient P(III)-directed ruthenium-catalyzed C-H olefination of tertiary phosphines with alkenyl reagents is reported for modular synthesis of axially olefin-phosphines. This late-stage functionalization exhibits broad substrate scope for both phosphines and olefins. A diverse library of 55 olefin-phosphines was prepared in high yields, tolerating up to 15 different functional groups. These ligands demonstrate exceptional performance in Suzuki coupling, achieving catalyst loadings as low as 0.005 mol % and surpassing commercial biarylphosphines in facilitating Pd-catalyzed C-C and C-X bond formations. Mechanistic studies and DFT calculations support a Ru-C addition/β-bromo elimination pathway over oxidative addition.