β-hydride elimination in palladium-catalyzed reactions

Pd(II)-catalyzed reactions were developed using beta-heteroatom elimination and protonolysis reaction to quench the carbon-palladium bond in the presence of halide ions or nitrogen ligands (pyridine, bipyridine, phenanthroline, etc.) for the regeneration of the divalent palladium species. Halide ions or nitrogen ligands are necessary for the catalytic cycle and high yield of the reactions. For Pd(O)-catalyzed reactions, control of beta-hydride elimination is also a challenge for making coupling reactions more diversified. Different kinds of ligands were used to make the coupling reaction suitable for aliphatic compounds. Recently, examples using chloride ion or bathophenanthroline for this purpose were also developed.