Department of Chemistry, University of California, Berkeley , Berkeley, California 94720, United States.
J Am Chem Soc. 2018 Feb 21;140(7):2450-2454. doi: 10.1021/jacs.7b13823. Epub 2018 Feb 6.
A general synthetic strategy for the construction of large, nitrogen-containing polycyclic aromatic hydrocarbons (PAHs) is reported. The strategy involves two key steps: (1) a titanocene-mediated reductive cyclization of an oligo(dinitrile) precursor to form a PAH appended with di(aza)titanacyclopentadiene functionality; (2) a divergent titanocene transfer reaction, which allows final-step installation of one or more o-quinone, diazole, or pyrazine units into the PAH framework. The new methodology enables rational, late-stage control of HOMO and LUMO energy levels and thus photophysical and electrochemical properties, as revealed by UV/vis and fluorescence spectroscopy, cyclic voltammetry, and DFT calculations. More generally, this contribution presents the first productive use of di(aza)metallacyclopentadiene intermediates in organic synthesis, including the first formal [2 + 2 + 2] reaction to form a pyrazine ring.
报道了一种构建大的含氮多环芳烃（PAHs）的通用合成策略。该策略涉及两个关键步骤：（1）通过茂金属介导的寡二腈前体的还原环化反应，形成带有二（氮杂）钛杂环戊二烯官能团的 PAH；（2）发散的茂金属转移反应，允许在最后一步将一个或多个邻醌、二唑或吡嗪单元安装到 PAH 骨架中。新方法通过紫外可见光谱、荧光光谱、循环伏安法和密度泛函理论计算，揭示了合理的、后期阶段控制 HOMO 和 LUMO 能级以及光物理和电化学性质。更一般地说，本贡献首次在有机合成中提出了二（氮杂）金属茂环戊二烯中间体的有效利用，包括首次通过[2+2+2]反应形成吡嗪环。
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