Bottom-up Construction of π-Extended Arenes by a Palladium-Catalyzed Annulative Dimerization of o-Iodobiaryl Compounds.

A straightforward method was developed for construction of aromatic compounds with a triphenylene core. The method involves Pd-catalyzed annulative dimerization of o-iodobiaryl compounds by double C-I and C-H bond cleavage steps. Simple reaction conditions are needed, requiring neither a ligand nor an oxidant, and the reaction tolerates a wide range of coupling partners without compromising efficiency or scalability. Significantly, the tetrachloro-substituted synthon, 1,6,11-trichloro-4-(4-chlorophenyl)triphenylene, can be generated and used to prepare a series of fully fused, small graphene nanoribbons by a late-stage arylation with arylboronic acids and a subsequent Scholl reaction. The synthetic strategy enables bottom-up access to extended π-systems in a controlled manner.