Exploring the Uncharted Indolizine Chemical Space: Construction of 5‐Acylindolizines via a Domino Aldol–Vinylogous Aldol Process

Described herein are two annulative functionalization approaches to novel indolizines leveraging a domino aldol condensation‐vinylogous aldol condensation procedure to construct the pyridine moiety of indolizines, enabling installation of an alkyl, an aryl, or an alkoxy group at the C7 position and an acyl group at the C5 position of indolizine framework. In the first approach, aldehyde oxidatively generated in situ from trialkylamine participated in a [4 + 2] annulation process with N ‐substituted pyrrole‐2‐carboxaldehydes to give rise to 5‐acylindolizines. In the second approach, the use of various aldehydes as reaction partners in this protocol allowed for the introduction of a wide range of substituents at the C7 site of indolizines.