Carbocyclic Carbene Ligands Derived from Aromatic Nitrones: Formation and Catalytic Activity of Their Pd(II) Complexes

Nitrones derived from aromatic aldehydes were shown to be convenient precursors to a novel class of carbocyclic carbene ligands. Air- and moisture-stable palladium complexes derived from the carbocyclic carbene ligands exhibit unprecedented catalytic efficiency in the Heck reaction. Deactivated aryl bromides, such as 4-bromoanisole, undergo coupling with styrene in the presence of 8 × 10-5 mol % of the catalysts with TON exceeding 0.9 million.