Electron-rich silicon containing phosphinanes for rapid Pd-catalyzed C-X coupling reactions

Palladium-catalyzed cross-coupling reactions are among the most useful and efficient methods for direct access to complex structures in organic synthesis. However, heteroatom-containing compounds can complicate such coupling reactions due to their competitive coordination with the palladium catalyst and electronic effects. As a result, good yields are often only obtained under harsher reaction conditions, such as high temperatures and long reaction times. Here we report the design of a highly active phosphine ligand that provides excellent yields for C-N coupling reactions at ambient temperature. Incorporation of the phosphorus atom into a cyclohexane ring maintains the pyramidal structure of the phosphorus while reducing steric hindrance. This, and a silicon atom in the cyclohexane moiety, results in an electron-rich phosphinane ligand. This novel silicon containing SabPhos ligand can be obtained in excellent yields in a straightforward synthesis. In palladium catalyzed reactions, this ligand facilitates the coupling of a broad range of heteroaryl chlorides via C-C bonds with boronic acids and C-N bonds with secondary amines in excellent yields under mild conditions.