Oxidative Nucleophilic Aromatic ipso-Substitution for the Late-Stage Functionalization of Polycyclic Aromatic Hydrocarbons with Five-Membered Rings

Nanographenes and polycyclic aromatic hydrocarbons (PAHs) are promising materials for advanced organic electronics, but their late-stage functionalization remains challenging. Here, we report an ipso-substitution, in which tert-butyl groups, which are usually installed for solubility reasons, are selectively replaced by mesylates on PAHs and nanographenes bearing five-membered rings. The reaction proceeds via an oxidative nucleophilic aromatic substitution mechanism and can be implemented in oxidative cyclodehydrogenation protocols to produce substituted PAH skeletons in one pot. Density functional theory calculations (DFT) support the suggested mechanism. Post-functionalization of the mesylates is possible according to literature-known protocols and is successfully demonstrated by the introduction of ether, alkyne, and aryl substituents. By controlling the amount of oxidant and the reaction time, the method enables the synthesis of asymmetric functional hydrocarbons from symmetric precursors overcoming statistical limitations by other protocols. Selected tert-butyl groups thus act as sites for the late-stage functionalization of nanographenes and PAH dyes.