New cyclopalladated benzothiophenes: a catalyst precursor for the Suzuki coupling of deactivated aryl chlorides

Dimeric benzothiophene-based palladacycles were synthesized from thioanisole-substituted perfluoroalkyl propargyl imines and palladium(II) salts via an intramolecular thiopalladation pathway. The treatment of benzothiophene-based palladacycles with an excess of phosphine ligands in benzene at room temperature selectively afforded trans-bis(phosphine) palladium complexes in good yields. The trans-bis(tricyclohexylphosphine) palladium complex was found to be an active catalyst in the Suzuki coupling of electron rich aryl chlorides. The complex was also employed in the catalytic synthesis of sterically hindered biaryls. The anticancer activity of palladacycles is also discussed.