Alkylation of (π-Allyl)palladium systems. Mechanism and regiocontrol

Palladium-catalyzed alkylation of 3-methyl-2-butenyl acetate with anions of dialkyl malonates gives the same product pattern as the stoichiometric alkylations of (η3-3-methylbutenyl)palladium chloride and the corresponding cationic complex. Consequently a (π-allyl)palladium intermediate is probable in the catalytic reaction. According to NMR evidence the reactive intermediate is a η3-allyl complex rather than a η1-allyl complex. Acceptor ligands, even weak ones such as phosphines, have a strong electronic influence on the reaction and direct the attack toward the more substituted position. The formal charge of the complexes is important to the reactivity, but when phosphines are present as acceptor ligands, the formation of cationic intermediates may not be necessary. © 1984 American Chemical Society