Cyclo[8]isoindoles: ring-expanded and annelated porphyrinoids.-猫眼课题宝

DOI：

10.1002/anie.201007510

发表时间：

2011-06

期刊：

Angewandte Chemie

影响因子：

通讯作者：

中科院分区：

文献类型：

作者：

T. Okujima;G. Jin;N. Matsumoto;J. Mack;Shigeki Mori;K. Ohara;Daiki Kuzuhara;C. Ando;N. Ono;H. Yamada;H. Uno;N. Kobayashi

近年来，人们越来越关注扩环卟啉（例如六菲林和八菲林）的化学性质，因为它们的性质与传统卟啉显着不同，这使得它们可能适合许多新颖的实际应用。[1-5]环[8]吡咯（[30]八菲林（0.0.0.0.0.0.0.0））及其较小的环[6]-和环[7]吡咯类似物，由 Sessler 及其同事基于 2, 2'-联吡咯与 FeCl3 的氧化偶联首次报道。 [6]与卟啉的一个关键结构差异是完全不存在内消旋碳原子。 [7]环 [n] 吡咯 (n= 6–8) 的光物理、[5] 阴离子结合、[7a, b] 和液晶特性 [7c] 及其电子结构已得到深入研究。[7d, 8] 环 [8] 吡咯的紫外/可见吸收光谱包含约 430 nm 处的较弱谱带 (ε% 1 105 mÀ1 cmÀ1) 和约 430 nm 处的强谱带1100nm (ε% 2 105 m−1 cm−1)。[6a] 近红外 (NIR) 区域的强吸光度使这些化合物可能适用于光存储和信号设备。尽管已经成功合成了多种稠环卟啉[9]，但目前还没有稠环扩张环[n]吡咯的报道，因为所需前体的制备极具挑战性。迄今为止，仅制备了β-烷基取代的化合物。[6, 7] 基于结构修饰（例如环退火）微调主要吸收带的波长的能力将大大增强这些化合物在实际应用中的实用性。在此，我们报告了基于双环[2.2]的氧化偶联首次成功合成环[8]异吲哚(3)。 2] 辛二烯 (BCOD) 稠合 2, 2’-联吡咯 (1)，然后进行环 [8] BCOD 吡咯的逆狄尔斯-阿尔德反应 (2；方案 1)。我们还报告了基于磁圆二色性（MCD）光谱和时间相关（TD）DFT计算对2和3的光学性质和电子结构的深入分析。最近，我们报告了使用retro-Diels-Alder策略从具有稠合BCOD基团的前体形成稠环扩张卟啉来合成苯并蓝宝石。 [10]采用类似的策略来合成环[8]-异吲哚。根据文献方法，由BCOD稠合吡咯制备BCOD稠合2, 2’-联吡咯1。[10a, 11]不同条件下2的合成详情总结于表1。最初，反应条件与 Sessler 及其同事 [6a] 报道的相似，采用 1m H2SO4 FeCl3 溶液作为氧化剂。在 Sessler 和同事报道的程序中，通过注射泵在 9 小时内将 1 的溶液缓慢添加到氧化剂和酸的混合物中。相反，我们立即将所有的FeCl3·6H2O氧化剂和H2SO4加入到2mm的1的CHCl3溶液中，并在08℃下搅拌混合物45分钟。通过硅胶柱色谱和凝胶渗透色谱(GPC)纯化后，得到深蓝色晶体2，收率43％。 MALDI-TOF 质谱包含分子离子峰

In recent years there has been a growing focus on the chemistry of ring-expanded porphyrins such as hexaphyrins and octaphyrins, because their properties differ markedly from those of conventional porphyrins in a manner that makes them potentially suitable for a number of novel practical applications.[1–5] Cyclo [8] pyrrole([30] octaphyrin (0.0. 0.0. 0.0. 0.0)), along with its smaller cyclo [6]-and cyclo [7] pyrrole analogues, was first reported by Sessler and co-workers based on an oxidative coupling of 2, 2’-bipyrrole with FeCl3.[6] A key structural difference with respect to the porphyrins is the complete absence of meso carbon atoms.[7] The photophysical,[5] anion-binding,[7a, b] and liquid-crystalline properties [7c] of cyclo [n] pyrroles (n= 6–8) have been studied in-depth, along with their electronic structures.[7d, 8] The UV/Vis absorption spectra of cyclo [8] pyrroles contain a weaker band at approximately 430 nm (ε% 1 105 mÀ1 cmÀ1) and a more intense band at approximately 1100nm (ε% 2 105 mÀ1 cmÀ1).[6a] The strong absorbance in the near-IR (NIR) region makes these compounds potentially suitable for use in optical storage and signaling devices. Despite the large variety of ring-annelated porphyrins that have been successfully synthesized,[9] there have been no reports of fused-ring-expanded cyclo [n] pyrroles, because the preparation of the required precursors is extremely challenging. To date, only β-alkyl substituted compounds have been prepared.[6, 7] The ability to fine-tune the wavelengths of the major absorption bands based on structural modifications such as ring annelation would greatly enhance the utility of these compounds for practical applications. Herein, we report the first successful synthesis of cyclo [8] isoindole (3) based on an oxidative coupling of bicyclo [2.2. 2] octadiene (BCOD)-fused 2, 2’-bipyrrole (1), followed by the retro-Diels–Alder reaction of cyclo [8] BCODpyrrole (2; Scheme1). We also report an in-depth analysis of the optical properties and electronic structures of 2 and 3 based on magnetic circular dichroism (MCD) spectroscopy and time-dependent (TD) DFT calculations.Recently, we reported the synthesis of benzosapphyrins using the retro-Diels–Alder strategy to form fused-ringexpanded porphyrins from precursors with fused BCOD groups.[10] A similar strategy is adopted to synthesize cyclo [8]-isoindoles. The BCOD-fused 2, 2’-bipyrrole 1 was prepared from BCOD-fused pyrrole according to literature procedures.[10a, 11] Details of the synthesis of 2 under different conditions are summarized in Table1. Initially, reaction conditions similar to those reported by Sessler and co-workers [6a] were adopted with a 1m H2SO4 solution of FeCl3 as the oxidant. In the procedure reported by Sessler and co-workers, the solution of 1 was slowly added to a mixture of the oxidant and acid over a period of 9 h by syringe pump. In contrast, we immediately added all of the FeCl3· 6H2O oxidant and H2SO4 toa2mm solution of 1 in CHCl3 and stirred the mixture for 45 minutes at 08C. After purification by silica gel column chromatography and gel permeation chromatography (GPC), 2 was obtained as deep blue crystals in 43% yield. The MALDI-TOF mass spectrum contained a molecular ion peak

Cyclo[8]isoindoles: ring-expanded and annelated porphyrinoids.

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