Rate and Mechanism of the Heck Reactions of Arylpalladium Complexes Ligated by a Bidentate P,P Ligand with an Electron-Rich Alkene (Isobutyl Vinyl Ether)

Two main intermediate complexes, PhPd(OAc)(dppp) and PhPdI(dppp), are generated in palladium-catalyzed Heck reactions performed from PhI and an acetate salt used as a base, in DMF. Both complexes react with the electron-rich alkene isobutyl vinyl ether (CH 2 CHO i Bu) exclusively by an ionic mechanism, i.e., via the cationic complex [PhPd(dppp)(DMF)] + formed by dissociation of AcO - or I - from the parent complexes, as already established for the reaction of PhPd(OAc)(dppp) with styrene and methyl acrylate and the reaction of PhPdI(dppp) with styrene. A mechanism is proposed which rationalizes the regioselectivity observed when reacting the electron-rich isobutylvinyl ether in palladium-catalyzed Heck reactions.