Mechanistic aspects of transition metal catalysed 1,6-diene and 1,6-enyne cycloisomerisation reactions

Isotopic, kinetic, spectroscopic, structural and computational investigations into the mechanism by which transition metals effect cycloisomerization are reviewed. Focus is on 1,6-diene and 1,6-enyne transition metal catalyzed cycloisomerization reactions. It is emphasized that all aspects of cycloisomerization would benefit from increased mechanistic insight and in the long term this will be the key to increasing catalyst efficiency, inducing or improving regio- chemo- or enantio-selectivities or eliminating cycloisomerization as side reaction.