Selective Synthesis of [12]Cycloparaphenylene
Selective Synthesis of [12]Cycloparaphenylene
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DOI：
10.1002/anie.200902617
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发表时间：
2009-01-01
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：
Takaba, Hiroko;Omachi, Haruka;Itami, Kenichiro
具有形状稳定性的纳米大环化合物（共轭分子环和共轭分子带）由于其在材料科学和超分子化学中的潜在应用而引起了人们的极大关注。[1，2]其中特别有趣和具有挑战性的是芳族带[1]和环，例如Vögtle带，[3，4]环苯并[5，6]环对苯并[7-9]和环并[10，11]。除了它们纯粹的美学吸引力之外，[1]这些不寻常的碳氢化合物代表了碳纳米管片段的结构模型，并且可以被设想为制备结构均匀的扶手椅或锯齿形碳纳米管的潜在前体（示意图1）。[12然而，尽管进行了广泛的试验，这些分子的合成仍然是一个艰巨的挑战。[1]在2005年，作为我们探索低聚芳烃[14]和纳米碳的新合成方法和性质的研究计划的一部分，[15]我们开始了这些芳香带/环的合成研究，旨在促进结构均匀的单壁碳纳米管的自下而上的有机合成。我们选择环对亚苯基[7-9]作为第一个目标，考虑到通过芳基-芳基键形成合成它们的相对简单的方法。尽管其结构简单，但在我们工作开始时没有成功的合成报道。最近，Bertozzi和同事完成了[9]-，[12]-和[18]环对亚苯基的首次合成，并将其命名为“碳纳米环”。[9]本文报道了一种通过钯催化的分步偶联反应选择性合成[12]环对苯撑（1）的方法。
Shape-persistent, nanosized macrocycles that are composed of only sp-and sp2-hydridized carbon atoms on their perimeter (conjugated molecular loops and belts) have attracted significant attention because of their potential applications in materials science and supramolecular chemistry.[1, 2] Particularly interesting and challenging among these are aromatic belts [1] and rings as exemplified by the Vögtle belts,[3, 4] cyclophenacenes,[5, 6] cycloparaphenylenes,[7–9] and cyclacenes [10, 11]. Adding to their sheer aesthetic appeal,[1] these unusual hydrocarbons represent structural models for carbon nanotube segments, and can be envisioned as potential precursors in the preparation of structurally uniform armchair or zigzag carbon nanotubes (Scheme1).[12, 13] However, despite extensive trials the synthesis of these molecules remains a formidable challenge.[1] In 2005, as a part of our research program exploring new synthetic methods and properties of oligoarenes [14] and nanocarbons,[15] we initiated a synthetic study of these aromatic belts/rings that aims at contributing to a bottom-up organic synthesis of structurally uniform single-walled carbon nanotubes. We selected cycloparaphenylene [7–9] as a first target in view of a comparatively straightforward approach to their synthesis through aryl–aryl bond formation. Despite its structural simplicity, no successful synthesis had been reported at the inception of our work. Very recently, Bertozzi and co-workers have accomplished the elegant first synthesis of [9]-,[12]-, and [18] cycloparaphenylenes and coined them as “carbon nanohoops”.[9] Herein, we report a selective synthesis of [12] cycloparaphenylene (1) through stepwise palladiumcatalyzed coupling reactions.