Role of Halide Ions in Divalent Palladium-Mediated Reactions:  Competition between β-Heteroatom Elimination and β-Hydride Elimination of a Carbon−Palladium Bond

The integral role of halide ions as a ligand in the reactions of stoichiometric arylpalladium reagents and Pd(II)-catalyzed reaction of phenylmercuric acetate with various allylic compounds were studied. The halide ion was found to inhibit β-H elimination and promote β-heteroatom elimination in acidic media. In this reaction, a C−Pd intermediate with a β-heteroatom (including halogen, acetoxy, alkoxy, and hydroxyl groups) gives only β-heteroatom elimination product in the presence of halide ions, while β-H elimination is effectively blocked.