Diastereoselective Synthesis of Polycyclic Indolizines with 2‑(2-Enynyl)pyridines and Enamines

A diastereoselective metal-catalyzed reaction of 2-(2-enynyl)­pyridines and cyclic enamines is reported. The method provides access to a variety of substituted indolizine derivatives by variation of the enyne component and the reaction conditions. Performing the reaction using a preformed enamine led to the formation of polycyclic indolizines. With in situ generated enamines, ketone-containing indolizine derivatives were obtained. An asymmetric reaction of 2-(2-enynyl)­pyridines and enamines generated from an aldehyde and a catalytic amount of amine is presented.