Long-Range Olefin Isomerization Catalyzed by Palladium(0) Nanoparticles

Long-range olefin isomerization of 2-alkenylbenzoic acid derivatives going through two to five sp³-carbon atoms to give (<i>E</i>)-alkenes was achieved with palladium(0) nanoparticles. The substrate scope of this reaction includes carboxylic acid, ester, and primary to tertiary amides and tolerates various substituents on the benzene ring. This isomerization reaction was catalyzed by recyclable Pd(0) nanoparticles, prepared in situ from PdCl₂ and characterized by X-ray powder diffraction and scanning electron microscopy analyses. ¹H NMR studies and kinetic modeling supported a stepwise process. This new process was applied to synthesize a natural dihydroisocoumarin with good efficiency