Bergman Harrison M, Beattie D Dawson, Kiel Gavin R, Handford Rex C, Liu Yi, Tilley T Don
Department of Chemistry, University of California Berkeley California 94720 USA
Molecular Foundry, Lawrence Berkeley National Laboratory Berkeley California 94720 USA
Chem Sci. 2022 Apr 1;13(19):5568-5573. doi: 10.1039/d2sc00397j. eCollection 2022 May 18.
The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels-Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations the marriage of two powerful cycloaddition strategies. First, a formal CpZr-mediated [2 + 2 + 1] cycloaddition is used to generate a stannole-annulated PAH. Secondly, the stannoles are employed as diene components in a [4 + 2] cycloaddition/aromatization cascade with an aryne, enabling π-extension to afford a larger PAH. This discovery of stannoles as highly reactive - yet stable for handling - diene equivalents, and the development of a modular strategy for their synthesis, should significantly extend the structural scope of PAHs accessible by a [4 + 2] cycloaddition approach.
多环芳烃（PAHs）及相关纳米石墨烯的合成需要多个芳环的选择性和高效融合。为此，狄尔斯-阿尔德环加成反应已被证明特别有用；然而，这种方法目前面临重大限制，包括缺乏获得稠环二烯的通用策略、最常用二烯的不稳定性以及[4 + 2]加合物芳构化的困难。在本报告中，我们通过结合两种强大的环加成策略来解决这些限制。首先，使用形式上的CpZr介导的[2 + 2 + 1]环加成反应生成一个含锡环的PAH。其次，将这些锡环用作与芳炔进行[4 + 2]环加成/芳构化级联反应中的二烯组分，实现π-扩展以得到更大的PAH。锡环作为高反应性但易于处理的二烯等价物的这一发现，以及其模块化合成策略的开发，应能显著扩展通过[4 + 2]环加成方法可获得的PAHs的结构范围。
