Palladium-Catalyzed Cross-Methylation of Aryl Chlorides by Stabilized Dimethylaluminium and -Gallium Reagents

Abstract

Two methods for palladium-catalyzed cross-methylation of aryl chlorides by intramolecularly stabilized dialkylaluminium and -gallium complexes 6-13 have been studied. In one method, in which either tetrakis(triphenylphosphine)palladium (1) or dichlorobis(triphenylphosphine)palladium (2) is used as the catalyst at 80-90 °C, the activation of the chlorine atom is affected by introduction of strong electron-withdrawing groups into the aromatic moiety. The second method is based on the application of either [1,3-bis(diisopropylphosphino)propane)]palladium (4) or homologous electron-rich palladium complexes as catalysts. Although 4 promotes smooth cross-alkylation of aryl chlorides it fails to activate simple aryl bromides.