Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes
Localized Antiaromaticity Hotspot Drives Reductive Dehydrogenative Cyclizations in Bis- and Mono-Helicenes
复制标题
局部反芳香性热点驱动双螺旋烯和单螺旋烯的还原脱氢环化
DOI：
10.1021/jacs.2c03681
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发表时间：
2022
影响因子：
15
通讯作者：
Alabugin, Igor V.
中科院分区：
文献类型：
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作者：
Zhou, Zheng;Egger, Dominic T.;Hu, Chaowei;Pennachio, Matthew;Wei, Zheng;Kawade, Rahul K.;Üngör, Ökten;Gershoni-Poranne, Renana;Petrukhina, Marina A.;Alabugin, Igor V.
我们描述了还原脱氢环化反应，从具有嵌入五元环的单螺旋烯和双螺旋烯形成七环、九环和十环阴离子石墨烯亚单元。双螺烯的反应可以进行到完全的双环化，或者在中间阶段通过加入分子氧来中断。双螺旋烯的中断环化级联的区域选择性证实，反芳香性的救济是这些容易的闭环的主导力量。计算分析揭示了独特的作用，预先存在的带负电荷的α部分在指导第二个负电荷在一个特定的远程位置，因此，创建一个本地化的反芳族区域。该区域是促进初始环化的热点。计算研究，包括MO分析，分子静电势图，和NICS（1.7）ZZ计算，评估各种效应的相互作用，包括电荷离域，螺旋烯应变释放，和反芳香性。反芳香性消除的作用进一步得到了应变较小的单螺旋烯的有效还原闭合的支持，其中反芳香性的消除促进了环化，即使当应变显著降低时。后一个发现显着扩大了Scholl环闭合的这种还原替代的范围。
We describe reductive dehydrogenative cyclizations that form hepta-, nona-, and decacyclic anionic graphene subunits from mono- and bis-helicenes with an embedded five-membered ring. The reaction of bis-helicenes can either proceed to the full double annulation or be interrupted by addition of molecular oxygen at an intermediate stage. The regioselectivity of the interrupted cyclization cascade for bis-helicenes confirms that relief of antiaromaticity is a dominant force for these facile ring closures. Computational analysis reveals the unique role of the preexisting negatively charged cyclopentadienyl moiety in directing the second negative charge at a specific remote location and, thus, creating a localized antiaromatic region. This region is the hotspot that promotes the initial cyclization. Computational studies, including MO analysis, molecular electrostatic potential maps, and NICS(1.7)ZZcalculations, evaluate the interplay of the various effects including charge delocalization, helicene strain release, and antiaromaticity. The role of antiaromaticity relief is further supported by efficient reductive closure of the less strained monohelicenes where the relief of antiaromaticity promotes the cyclization even when the strain is substantially reduced. The latter finding significantly expands the scope of this reductive alternative to the Scholl ring closure.