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 x 10(-5) mol % of the catalysts with TON exceeding 0.9 million.