Pd(0)-catalyzed cis-trans Alkene Isomerization

The cis-trans isomerization of some olefins bearing strong electron-withdrawing substituents (dmma and E-tse) is catalyzed by their mere coordination to a suitable Pd(0) fragment without any external reagents. The choice of spectator ligand is fundamental to the efficiency of the process, and the phosphanylquinolines dppq and dppq-Me have proven to be particularly effective. The mechanism of the rearrangement is discussed, and the presence of electron-withdrawing and conjugated substituents on the olefins appears to be an essential prerequisite for the isomerization.