Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, 565-0871, Japan).
Chemistry. 2018 May 23;24(29):7489-7497. doi: 10.1002/chem.201800617. Epub 2018 Apr 26.
Polycyclic heteroaromatic compounds including pyrrole units are promising functional scaffolds owing to their electron-rich nature, bright fluorescence, and applicability to anion recognition at the pyrrolic hydrogen atom. We report herein the effective synthesis of pseudo-aza[5]helicene and aza[7]helicene derivatives, and unexpected formation of azahepta[8]circulenes by oxidative fusion reactions. By choosing reaction conditions and peripheral substituents attached at the terminal indole moieties, we obtained aza[7]helicenes 10 a-c and azahepta[8]circulenes 11 a,c selectively in moderate to good yields. Their solid-state structures have been revealed by X-ray diffraction analysis. UV/Vis absorption, emission, and cyclic voltammetry of these compounds were studied in comparison with those of previously reported tetraaza[8]circulene (TA8C), a symmetric and planar molecule. Furthermore, the enantiomeric separation of dimethyl-substituted aza[7]helicene 10 b was achieved, and the racemization kinetics have been elucidated both theoretically and experimentally. This work illustrates a wealth of advantages of pyrrole incorporation into the polycyclic aromatic scaffolds in terms of synthetic aspects, structural variation, and optical tuning.
包括吡咯单元的多环杂芳烃化合物由于其富电子性质、明亮的荧光以及在吡咯氢原子处对阴离子识别的适用性，是很有前途的功能支架。我们在此报告了假氮[5]并苯和氮[7]并苯衍生物的有效合成，以及通过氧化融合反应意外形成氮杂庚[8]轮烯。通过选择反应条件和连接在末端吲哚部分的外围取代基，我们以中等至良好的产率选择性地获得了氮[7]并苯 10a-c 和氮杂庚[8]轮烯 11a,c。它们的固态结构已通过 X 射线衍射分析揭示。与先前报道的对称且平面的四氮[8]轮烯（TA8C）相比，对这些化合物的紫外/可见吸收、发射和循环伏安法进行了研究。此外，还实现了二甲基取代氮[7]并苯 10b 的对映体拆分，并从理论和实验上阐明了外消旋化动力学。这项工作说明了在合成方面、结构变化和光学调谐方面，将吡咯掺入多环芳烃支架具有丰富的优势。
