Department of Chemistry, University of California, Berkeley, CA, 94720, USA.
Angew Chem Int Ed Engl. 2017 Apr 18;56(17):4839-4844. doi: 10.1002/anie.201700818. Epub 2017 Mar 23.
Syntheses of large polycyclic aromatic hydrocarbons (PAHs) and graphene nanostructures demand methods that are capable of selectively and efficiently fusing large numbers of aromatic rings, yet such methods remain scarce. Herein, we report a new approach that is based on the quantitative intramolecular reductive cyclization of an oligo(diyne) with a low-valent zirconocene reagent, which gives a PAH with one or more annulated zirconacyclopentadienes (ZrPAHs). The efficiency of this process is demonstrated by a high-yielding fivefold intramolecular coupling to form a helical ZrPAH with 16 fused rings (from a precursor with no fused rings). Several other PAH topologies are also reported. Protodemetalation of the ZrPAHs allowed full characterization (including by X-ray crystallography) of PAHs containing one or more appended dienes with the ortho-quinodimethane (o-QDM) structure, which are usually too reactive for isolation and are potentially valuable for the fusion of additional rings by Diels-Alder reactions.
大尺寸多环芳烃（PAHs）和石墨烯纳米结构的合成需要能够选择性和有效地融合大量芳环的方法，但此类方法仍然很少。在此，我们报告了一种新方法，该方法基于低价锆试剂定量的内分子还原环化，得到具有一个或多个稠合锆茂环（ZrPAHs）的 PAH。该过程的效率通过高产率的五重内分子偶联来证明，形成具有 16 个稠合环的螺旋 ZrPAH（从前体中没有稠合环）。还报道了其他几种 PAH 拓扑结构。ZrPAHs 的脱金属化允许对含有一个或多个附加二烯的 PAHs 进行充分表征（包括通过 X 射线晶体学），这些二烯具有邻醌二甲基甲烷（o-QDM）结构，通常由于太活泼而无法分离，并且对于通过 Diels-Alder 反应融合额外的环具有潜在价值。
