Facile Synthesis of Nitrogen Cation-Doped Polycyclic Aromatic Hydrocarbons by Anodic Intramolecular Pyridination

The bottom-up synthesis of heteroatom-doped polycyclic aromatic hydrocarbons (PAHs) has attracted attention in the development of models of doped graphene. Among PAHs, nitrogen-cation ( N + )-doped PAHs are known to exhibit superior optoelectronic functionalities; however, practical methods for synthesizing N + -doped PAHs are limited and challenging [1]. In our previous study, the S N Ar reaction was used for the intramolecular cyclization of phenylpyridine derivatives possessing an electron-deficient perfluoroaryl moiety to give the corresponding N + -doped triphenylene in high yields under moderate conditions without the use of a transition-metal catalyst [2,3]. However, one of the challenges in the synthesis of N + -doped PAHs via the S N Ar reaction is poor functional-group tolerance. Here, a facile and selective synthesis method for N + -doped PAHs has been established via anodic intramolecular cyclization, inspired by the Yoshida’s protocol for C–H amination without a transition-metal catalyst or an oxidant [4]. The reaction mechanism, in particular the reaction selectivity, was elucidated using density functional theory (DFT) calculations. The N + -doped PAH products were found to have a donor–acceptor structure composed of an arene moiety and a pyridinium moiety, as evidenced by DFT calculations, UV–vis analysis, and electrochemical measurements. The proposed intramolecular anodic pyridination is a practical strategy for the late-stage introduction of N + into π-electron systems and broadens the scope of molecular design of N + -doped PAHs. References: J. Liu, X. Feng, Synlett 2020 , 31 , 211–222 Y. Asanuma, H. Eguchi, H. Nishiyama, I. Tomita, S. Inagi, Org. Lett. 2017 , 19 , 1824–1827 N. Shida, H. Nishimi, Y. Asanuma, I. Tomita, S. Inagi, Polym. J. 2020 , 52 , 1401–1406. T. Morofuji, A. Shimizu, J. Yoshida, J . Am . Chem . Soc ., 2013 , 135 , 5000–5003. Figure 1