Metal complexes of chiral Möbius aromatic [28]hexaphyrin(1.1.1.1.1.1): enantiomeric separation, absolute stereochemistry, and asymmetric synthesis.
Metal complexes of chiral Möbius aromatic [28]hexaphyrin(1.1.1.1.1.1): enantiomeric separation, absolute stereochemistry, and asymmetric synthesis.
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DOI：
10.1002/anie.201002282
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发表时间：
2010-09
影响因子：
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通讯作者：
Takayuki Tanaka;Tsutomu Sugita;Sumito Tokuji;Shohei Saito;A. Osuka
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文献类型：
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作者：
Takayuki Tanaka;Tsutomu Sugita;Sumito Tokuji;Shohei Saito;A. Osuka
莫比乌斯芳香性的概念由Heilbronner在1964年首次提出，预测了具有单扭曲的所谓莫比乌斯拓扑的[4 n π]轮烯的芳香性特征。[1]重要的是，这个概念补充了建立在正常平面π电子网络基础上的Hückel芳香性[1，2]，因此刺激了理论和实验研究。在这些研究中，第一个莫比乌斯芳香[16]轮烯是由埃尔热及其同事在2003年报道的[3]，随后是一个有趣的例子，即二对苯己卟啉，它在休克尔和莫比乌斯构象之间表现出温度依赖性的结构变化。[4]在过去的两年中，Möbius芳香体系已经从meso-aryl-substituted expanded porphyrins开始通过金属配位、[5a，B]温度控制、[5c，d]质子化、[5e，f]和分子内融合反应有效地制备。[5g具有单扭曲莫比乌斯拓扑结构的大环本质上是手性的，并且可以是P-扭曲或M-扭曲，如图1所示。控制莫比乌斯芳族扩展卟啉的手性对于理解它们的磁性以及将这些系统应用于手性传感和不对称催化剂是重要的。虽然Möbius芳香轮烯的对映异构体分离已经由埃尔热及其同事完成，但它们的绝对构型尚未确定。[3b]此外，迄今为止，只有有限的扭曲膨胀卟啉的对映体分离的实例已被报道。[6]We设想了[28]己卟啉的第10族金属络合物的对映体分离（1.1. 1.1. 1.1)的基础上，六卟啉被认为是相当强大的，如其几乎温度无关的1H NMR光谱所示。在此，我们报告了这些配合物的对映体分离，通过使用制备型HPLC手性固定相，以及钯（II）配合物的不对称合成。
The concept of Möbius aromaticity, first proposed by Heilbronner in 1964, predicts the aromatic characters for [4nπ] annulenes with singly twisted so-called Möbius topology.[1] Importantly, this concept complements the established Hückel aromaticity that is based on normal planar πelectronic network,[1, 2] and therefore stimulates both theoretical and experimental studies. Among these studies, the first Möbius aromatic [16] annulene was reported by Herges and co-workers in 2003,[3] and was followed by an interesting example of a di-p-benzi-hexaphyrin that exhibited a temperature dependent structural change between Hückel and Möbius conformations.[4] In the last two years, Möbius aromatic systems have been efficiently prepared starting from meso-aryl-substituted expanded porphyrins through metal coordination,[5a, b] temperature control,[5c, d] protonation,[5e, f] and intramolecular fusion reactions.[5g, h] Macrocycles that have a singly twisted Möbius topology are intrinsically chiral, and can be either P-twist or M-twist, as shown in Figure 1. Control of the chirality of Möbius aromatic expanded porphyrins is important to understand their magnetic properties and to apply these systems to chirality sensing and asymmetric catalysts. Although the enatiomeric separation of Möbius aromatic annulenes has been accomplished by Herges and co-workers, their absolute configurations have not been determined.[3b] In addition, only limited examples of the enantiomeric separations of twisted expanded porphyrins have been reported to date.[6]We envisioned the enantiomeric separation of Group 10 metal complexes of [28] hexaphyrin (1.1. 1.1. 1.1) on the basis that hexaphyrins are considered to be rather robust, as indicated by their almost temperature-independent 1H NMR spectra. Herein, we report the enantiomeric separation of these complexes by using preparative HPLC on a chiral stationary phase, as well as the asymmetric synthesis of the palladium (II) complex.