Copper-catalyzed formal [1 + 2 + 2]-annulation of alkyne-tethered diazoacetates and pyridines: access to polycyclic indolizines.

A copper-catalyzed formal [1 + 2 + 2]-annulation of alkyne-tethered diazo compounds with pyridines, which affords polycyclic fused indolizines in synthetically useful to good yields under mild reaction conditions, has been reported. This method features the use of an inexpensive copper catalyst and readily available starting materials, broad substrate generality, and operational simplicity. Notably, a variety of natural product derivatives are compatible under the current conditions, which shows significant potential of this method for the selective decoration and modification of analogous biomolecules or pharmaceuticals.