Zur Kenntnis der katalytischen Dimerisation von Acrylsäurederivaten mit Hilfe von Palladium‐Komplexen. III. Reaktionen von β‐Palladioacrylestern und deren Beziehung zur Katalytischen Reaktion

Abstract

On the Knowledge of the Catalytic Dimerization of Acrylic Acid Derivatives by Palladium Complexes. III Reactions of β‐Palladio Acrylates and Their Relation to the Catalytic Reaction Complexes of the type L 2 PdCl(CH  CHCOOCH 3 ) (L 2 = 2 PPh 3 or Ph 2 PCH 2 CH 2 PPh 2 ) were decomposed to dimethyl muconate by pyrolysis or by substraction of the phosphine ligands with (CH 3 CN) 2 PdCl 2 in acetonitrile. The last mentioned reaction gave Δ 3 ‐dimethyl dihydromuconate in the presence of hydrochloric acid. Δ 3 ‐Dimethyl dihydromuconate was also formed by decomposition of (Ph 2 PCH 2 CH 2 PPh 2 ) PdCl (CH  CHCOOCH 3 ) with HBF 4 in acetonitrile, but the analogous reaction in methyl acrylate as solvent gave Δ 2 ‐dimethyl dihydromuconate. Thus, we have simulated the formation of the two main products of the catalytic dimerization of methyl acrylate with palladium(II)chloride in a stoichiometric manner. Mechanisms with hydride and carbene intermediates are discussed.