Porous polycyclic aromatic heterocycles via metal-free annulative π-extension

The synthesis of nitrogen-containing polycyclic aromatic heterocycles (PAHs) is important because of their expanding range of applications. Over the past decade, the preparation of PAHs has largely relied on complex, multistep processes. These methods necessitate the use of expensive transition-metal catalysts and sophisticated techniques. Here we report a one-pot, metal-free synthesis of PAHs that addresses the limits of traditional methods. Our method uses a sequence of imine condensation, nucleophilic aromatic substitution and intramolecular Friedel–Crafts reactions, leading to the synthesis of aromatic and seven-ring fused 5,11,17-triazatrinaphthylene compounds. The approach can incorporate various substituents, including alkyl chains and heteroatoms, with high regioselectivity and efficiency. In addition, this method enables the in situ crystallization of 5,11,17-triazatrinaphthylene molecules using precipitation under high pressure, potentially removing the need for chromatographic separation and allowing for bulk-scale production. This process is particularly beneficial for creating crystalline, porous polyaromatic heterocyclic materials with tunable permanent porosity.