Isolation of Ruthenium–Indolizine Complexes: Insight into the Metal-Induced Cycloisomerization of Propargylic Pyridines

A class
of ruthenium–indolizine complexes was isolated and
structurally characterized, and they represent the first examples
of metalated indolizine species. Both experimental and theoretical
investigations on the formation
of these complexes support a 5-endo-dig cyclization mechanism and discount a vinylidene–5-exo-dig cyclization pathway.