Cationic π-extended heteroaromatics via a catalytic C-H activation annulative alkyne-insertion sequence

Cationic pi-conjugated organic molecules have broad applications in materials science as next-generation organic materials. The annulative alkyne-insertion pi-extension (AAIPEX) strategy has emerged as a promising synthetic approach for the rapid synthesis of cationic polycyclic heteroaromatic compounds (cPHACs) in a single step. The AAIPEX reaction provides a synthetic shortcut to achieve complex organic molecules from simple (hetero)arene templates and alkynes as pi-extending partners, which would otherwise be difficult to achieve using traditional methods. In general, a step-economic AAIPEX protocol proceeds via C-H activation of unfunctionalized heteroarene templates, followed by alkyne insertion-annulation to furnish cPHACs. In this Feature Article, recent progress in the AAIPEX strategy to construct cPHACs is described along with brief illustrations of the resulting cPHACs in luminescence-related applications.