Towards Nonalternant Nanographenes through Self-Promoted Intramolecular Indenoannulation Cascade by C-F Bond Activation.

Large polycyclic aromatic hydrocarbons (PAHs) containing pentagons represent an important class of compounds that are considered to be superior materials in future nano-electronic applications. From this perspective, the development of synthetic approaches to large PAHs and nanographenes (NGs) is a matter of great importance. In this context indenoannulation appears to be the most practical way to introduce pentagons into NGs. Here we report that alumina-mediated C-F bond activation is an attractive tool for the synthesis of non-alternant NGs bearing several pentagons. The unique nature of the reaction leads to a rather counter-intuitive outcome and allows considering each previous aryl-aryl coupling as a promoter of the following one, despite the continuous increase in the strain energy. Thus, the presented strategy combines both facile synthesis and significant yields for large nonalternant PAHs and NGs.