Palladium-catalyzed cross-methylation of aryl chlorides by stabilized dimethylaluminium and -gallium reagents

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