A Modular and Size-Selective Synthesis of [n]Cycloparaphenylenes: A Step toward the Selective Synthesis of [n, n] Single-Walled Carbon Nanotubes
A Modular and Size-Selective Synthesis of [n]Cycloparaphenylenes: A Step toward the Selective Synthesis of [n, n] Single-Walled Carbon Nanotubes
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DOI：
10.1002/anie.201005734
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发表时间：
2010-01-01
影响因子：
16.6
通讯作者：
Itami, Kenichiro
中科院分区：
文献类型：
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作者：
Omachi, Haruka;Matsuura, Sanae;Itami, Kenichiro
近世纪来，环对亚苯基（CPP），一个简单的苯环串，吸引了科学家的原因有很多。[1，2]除了它们纯粹的美学吸引力和独特的弯曲共轭，CPP代表扶手椅碳纳米管结构的最短侧壁段（方案1）。[1，3]经过大量化学家的广泛试验，[4]由Bertozzi，[5]伊塔米，[6，7]和Yamago [8]领导的小组最终完成了一些[n] CPP（n= 8，9，12，18）的自下而上的有机合成。虽然在这些研究中已经确定了几种可能的CPP结构路线，但尚未开发出允许灵活和大小选择性合成一系列[n] CPP的统一策略。考虑到预期CPP可以作为制备结构均匀的扶手椅式单壁碳纳米管（SWNT）的前体或种子，设计这样的策略非常重要（方案1）。[1，9]正如其他人提出和证明的那样，[10]使用相对较短的烃模板如CPP的扩增生长策略有望实现期待已久的SWNT选择性合成。在这样的策略中，[n] CPP的模块化和尺寸选择性合成在以受控和选择性方式提供[n，n] SWNT中将是至关重要的。我们现在描述了[n] CPP（n！14)并报道了[14]-、[15]-和[16] CPP的合成，作为我们新策略的原理证明。我们的CPP合成非常灵活，以可控和可编程的方式组装弯曲和线性构建块。本质上，我们先前以3+ 3+ 3+ 3模式使用三联苯等价的L形二苯基环己烷单元合成[12] CPP; Pd催化逐步形成“盒”（3+ 3+ 3，然后9+ 3），然后芳构化（方案2）。[6]通过策略性地改变弯曲的数量，
For nearly one century, cycloparaphenylene (CPP), a simple string of benzene rings, has captivated scientists for many reasons.[1, 2] Adding to their sheer aesthetic appeal and unique curved conjugation, CPPs represent the shortest sidewall segment of armchair carbon nanotube structures (Scheme 1).[1, 3] After extensive trials by numerous chemists,[4] the groups led by Bertozzi,[5] Itami,[6, 7] and Yamago [8] have finally accomplished the bottom-up organic synthesis of some [n] CPPs (n= 8, 9, 12, 18). Although several possible routes toward CPP structures have been identified in these studies, a uniform strategy allowing the flexible and size-selective synthesis of a range of [n] CPPs has yet to be developed. Devising such a strategy is important in view of the expectation that CPP could serve as a precursor or seed in the preparation of structurally uniform armchair single-walled carbon nanotubes (SWNTs)(Scheme 1).[1, 9] As proposed and demonstrated by others,[10] the amplification growth strategy using a relatively short hydrocarbon template such as CPP holds the promise of a long-awaited selective synthesis of SWNTs. In such a strategy, a modular and size-selective synthesis of [n] CPPs would be critically important in providing [n, n] SWNTs in a controlled and selective fashion. We now describe a modular and size-selective synthetic approach to [n] CPPs (n! 14) and report the synthesis of [14]-,[15]-, and [16] CPP as a proof-of-principle of our new strategy. Our CPP synthesis is very flexible, assembling bent and linear building blocks in a controlled and programmable manner. In essence, we previously synthesized [12] CPP in a 3+ 3+ 3+ 3 mode using a terphenyl-equivalent L-shaped diphenylcyclohexane unit; Pd-catalyzed stepwise formation of a “box”(3+ 3+ 3 and then 9+ 3), followed by aromatization (Scheme 2).[6] By strategically varying the number of bent