Polycyclic Arene Synthesis by Annulative π-Extension

Annulative π-extension (APEX) has emerged as a powerful and efficient synthetic method for the construction of polycyclic aromatic hydrocarbons, nanographenes, and π-extended fused heteroarenes. In contrast to classical multistep syntheses requiring substrate prefunctionalization, APEX reactions minimize the number of preparative steps by direct C-H activation of small aromatic templates. In this Perspective, we review recently reported APEX reactions to shed light on the utility, scope, and promise of this approach for next-generation syntheses of polycyclic arenes.