Hataaki Yoshimoto

Isotope effect of aromatic coupling reaction catalyzed by palladium acetate

Abstract Isotope effect in palladium catalyzed coupling reaction of aromatic compounds has been measured under oxygen pressure as well as under atmospheric pressure. For deuterobenzene, a large isotope effect ( k H k D ) was found to be 2.1–2.5 at 150 °C under oxygen pressure and to be 4.1–5.1 at room temperature under atmospheric pressure. On the basis of these isotope effects, we proposed the two-step hydrogen abstraction mechanism. Under oxygen pressure, oxygen plays an important role in the re-oxidation of reduced palladium(O) complex.

Palladium-catalyzed competitive reaction of aromatic compounds

Abstract The oxidative coupling of aromatic compounds proceeded catalytically, accompanied by regeneration of Pd(0) to Pd(II) with molecular oxygen. The relative reactivities to benzene and compositions of biaryls gave partial rate factors by the application of a two stage coupling process, showing remarkable polar and steric effects. The reactivity ratios o m , p m differ from those reported in a palladium salt-acetic acid system and a phenyl radical coupling.