Synthesis of Heptagon‐Containing Polyarenes by Catalytic C−H Activation

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AbstractNanocarbons incorporating non‐hexagonal aromatic rings ‐ such as five‐, seven‐, and eight‐membered rings ‐ have various intriguing physical properties such as curved structures, unique one‐dimensional packing, and promising magnetic, optical, and conductivity properties. Herein, we report an efficient synthetic approach to polycyclic aromatics containing seven‐membered rings via a palladium‐catalyzed intramolecular Ar−H/Ar−Br coupling. In addition to all‐hydrocarbon scaffolds, heteroatom‐embedded heptagon‐containing polyarenes can be efficiently constructed with this method. Rhodium‐ and palladium‐catalyzed sequential six‐ and seven‐membered ring formations also afford complex heptagon‐containing molecular nanocarbons from readily available arylacetylenes and biphenyl boronic acids. Detailed mechanistic analysis by DFT calculations showed the feasibility of seven‐membered ring formation by a concerted metalation‐deprotonation mechanism. This reaction can serve as a template for the synthesis of a wide range of seven‐membered ring‐containing molecular nanocarbons.