BINAP also appears to play a critical role in promoting the desired quaternary-center forming path over the b-hydride elimination pathway, while the use of bipyridine ligand gave a 1:1 ratio of 8a:8b (Figure , panel III). Bipyridine-type ligands are known to enhance chain-walking in favor of the isomerization pathway. Other mono-and bidentate phosphines, including PPh3 and dppp, were inferior to BINAP (see panel III and SI).