Bringmann Gerhard, Götz Daniel C G, Gulder Tobias A M, Gehrke Tim H, Bruhn Torsten, Kupfer Thomas, Radacki Krzysztof, Braunschweig Holger, Heckmann Alexander, Lambert Christoph
Institute of Organic Chemistry and Röntgen Research Center for Complex Material Systems, University of Würzburg, Am Hubland, D-97074 Würzburg, Germany.
J Am Chem Soc. 2008 Dec 31;130(52):17812-5. doi: 10.1021/ja8055886.
In this paper, the synthesis of a new type of intrinsically chiral, directly beta,beta'-linked, octa-meso-aryl-substituted bisporphyrins is described, by using an optimized Suzuki-Miyaura coupling procedure. This strategy leads to a broad variety of such axially chiral 'superbiaryls', differing in their metalation states and substitution patterns. On the basis of an efficient route to as-yet-unknown beta-boronic acid esters of various meso-tetraarylporphyrins (TAPs) by a two-step bromination-borylation protocol, 18 axially chiral bisporphyrin derivatives were prepared in good to excellent yields. As compared to all other directly linked dimeric porphyrin systems, the joint presence of eight bulky meso substituents and the peripheral position of the porphyrin-porphyrin linkage is unprecedented. The axial configurations and rotational barriers of the pure atropo-enantiomers were investigated by HPLC-CD experiments on a chiral phase in combination with quantum chemical CD calculations. According to the HPLC experiments and in agreement with quantum chemical calculations by applying the dispersion-corrected BLYP method, the configurational stability of the central porphyrin-porphyrin axis strongly depends on the nature of the central metals. Cyclovoltammetric studies proved the systematic influence of the meso substituents and of the metal ions on the oxidation potentials of the bisporphyrins. The novel axially chiral bis(tetrapyrrole) compounds described here are potentially useful as substrates for asymmetric catalysis, biomimetic studies on directed electron-transfer processes, for photodynamic therapy (PDT), and for chiral recognition.
本文描述了一种新型本征手性、直接β,β'-相连、八介观芳基取代双卟啉的合成方法，采用了优化的铃木-宫浦偶联程序。该策略可得到多种此类轴向手性“超级联芳基”，它们的金属化状态和取代模式各不相同。基于一种通过两步溴化-硼化协议高效合成各种介观四芳基卟啉（TAPs）的未知β-硼酸酯的方法，以良好至优异的产率制备了18种轴向手性双卟啉衍生物。与所有其他直接相连的二聚卟啉体系相比，八个庞大的介观取代基的共同存在以及卟啉-卟啉键的外围位置是前所未有的。通过在手性相上进行HPLC-CD实验并结合量子化学CD计算，研究了纯阻转对映体的轴向构型和旋转势垒。根据HPLC实验并与应用色散校正BLYP方法的量子化学计算结果一致，中心卟啉-卟啉轴的构型稳定性强烈依赖于中心金属的性质。循环伏安研究证明了介观取代基和金属离子对双卟啉氧化电位的系统性影响。本文所述的新型轴向手性双（四吡咯）化合物有可能用作不对称催化的底物、定向电子转移过程的仿生研究、光动力疗法（PDT）以及手性识别的底物。
