Formal Fusion of a Pyrrole Ring onto 2‐Pyridyl and 2‐Pyrimidyl Cations: One‐Step Gas‐Phase Synthesis of Indolizine and Its Derivatives

Gaseous 2‐pyridyl and 2‐pyrimidyl cationsreact promptly with 1,3‐dienes by annulation to produce a new pyrrole ring. ortho‐Hetarynium ions and 1,3‐dienes thus provide the two building blocks for the efficient gas‐phase synthesis of ionized indolizines and their derivatives (see scheme).