Diversity-Oriented Two-Step Annulative π-Extension Enables Access to Structurally Complex Nanographenes.

The development of a general strategy for accessing structurally diverse nanographenes and polycyclic aromatic hydrocarbons (PAHs) remains a central challenge in synthetic chemistry. Although annulative π-extension (APEX) enables the direct construction of fused aromatic systems from unfunctionalized PAHs, its structural scope has been largely constrained by the limited diversity of applicable π-extending reagents. Herein, we report on a diversity-oriented two-step APEX strategy that overcomes this limitation through the use of structurally diverse naphthalene-based aryltrimethylsilanes in Pd/o-chloranil-catalyzed C-H arylation, followed by oxidative cyclodehydrogenation. This approach enables the introduction of sterically congested polyaryl motifs and provides access to nanographenes with 8 to 10 fused rings and diverse ring-fusion patterns. Notably, a negatively curved nanographene containing five-, six-, and seven-membered rings was synthesized and fully characterized by x-ray crystallography, spectroscopy, and theoretical calculations, highlighting the capability of this approach to access challenging nanographene architectures. This work establishes a general platform for diversity-oriented APEX synthesis, thereby redefining the scope and synthetic potential of APEX chemistry.