Cu-catalyzed transannulation reaction of pyridotriazoles: general access to fused polycyclic indolizines

An efficient intramolecular transannulation reaction of pyridotriazoles using internal alkynes en route to various fused polycyclic indolizines has been developed. For the first time it is shown that in addition to the well-established Rh- or Cu-catalyzed carbene mechanism, the transannulation reaction could also follow a Lewis acid-mediated electrophilic pathway.