Aryl Shift Rearrangement in Scholl-Type Reaction Toward Nanographene

Oxidative dehydrogenation, known as Scholl reaction, is a powerful method for synthesizing many polycyclic aromatic hydrocarbons. Sometimes, unexpected rearrangements can lead to the formation of new structures that are usually difficult to obtain. Here, we discover a novel Scholl-type reaction involving both 1,4-aryl- and 1,2-aryl shift rearrangements, resulting in the production of armchair nanographene. Additionally, we establish the principle of the rearrangement mechanism through thermodynamic and kinetic studies using density functional theory (DFT). Theoretical studies indicate that the rearrangement reaction involves both arenium cation- and radical cation mechanisms. The selection of arenium cation- or radical cation mechanisms depends on the sizes and positions of the shifting aryl groups. Large biphenyl or triphenylenyl groups undergo the arenium cation mechanism, while a small monophenyl group favors the radical cation mechanism. Our findings offer new insights into the controllable rearrangements in Scholl reaction and provide new synthetic methods for obtaining a variety of polycyclic aromatic hydrocarbons, which are typically challenging to design.