Preferential Formation of Cyclic Trimers by Palladium-Catalyzed Oxidative Coupling Reactions of 2,18-Diethynylporphyrins
Preferential Formation of Cyclic Trimers by Palladium-Catalyzed Oxidative Coupling Reactions of 2,18-Diethynylporphyrins
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钯催化 2,18-二乙炔基卟啉氧化偶联反应优先形成环状三聚体
DOI：
10.1002/anie.201207763
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
A. Osuka
中科院分区：
文献类型：
--
作者：
S. Tokuji;H. Yorimitsu;A. Osuka
受光合光捕获天线中细菌叶绿素和叶绿素巨大环状排列的启发，人们在环状卟啉低聚物（CPO）的合成方面投入了大量的精力。 [1]其中，直接 1, 3-丁二炔桥联的共轭 CPO 由于其有趣的结构、电子和光学特性而具有特殊的地位。通常，有效的大环化需要合成技巧。杉浦等人。使用L形5, 10-二芳基-15, 20-二乙炔基卟啉作为合成方形内消旋到内消旋丁二炔桥接平面CPO的关键角部分。 [2] Anderson 及其同事使用线性 5, 15-二芳基-10, 20-二乙炔基卟啉前体[3]开发了一种优雅的模板引导合成内消旋-内消旋丁二炔桥联环状 CPO，其中模板-底物复合物的结构决定了主要的 CPO 产物。这种方法已发展成为概念上新的 Verniertemplate 合成。[3d, f] 我们还报道了铜介导的 5, 10, 15-三芳基-2, 18-二乙炔基卟啉 1M 氧化二聚反应，以良好的产率提供 β-to-β 1, 3-丁二炔桥环卟啉二聚体 2M。 [4]人们已经认识到，钯催化的乙炔氧化偶联可以产生与通常的铜介导的反应不同的产物。作为一个代表性的例子，Haley和他的同事报道了通过单一前体的分子内偶联反应金属依赖性选择性合成两种不同的脱氢苯并轮烯，这是由于它们的反应机制的不同。 [5]尽管仍存在争议，但 Cu 介导的氧化丁二炔合成机制被认为涉及在还原消除之前以伪反式构型排列的二聚铜乙炔（方案 1）。 [6]另一方面，在钯催化反应中，两个乙炔基被建议以顺式几何形状排列以进行还原消除。 [7]与 Haley 及其同事的分子内反应相比，金属催化的分子间氧化丁二炔的形成更难以控制。[8, 9] 在此，我们报道了通过 Pd 催化的 1M 偶联反应优先形成三聚体 3M。在催化量的 PdCl2 (PPh3)2 和 CuI 存在下，在室温下搅拌 1Ni 的甲苯和二异丙胺溶液。两当量的1, 4-苯醌作为氧化剂。通过制备型凝胶渗透色谱分离得到 2Ni [4] 和 3Ni，产率分别为 9.3% 和 72%（方案 2）。 [10] 3Ni 的 MALDITOF 质谱显示母离子峰位于 2933.39（C198H210N12Ni3 计算值，m/z 2933.49 [M]+）。这
Inspired by the gigantic cyclic arrangements of bacteriochlorophylls and chlorophylls in photosynthetic light-harvesting antenna, considerable efforts have been devoted to the synthesis of cyclic porphyrin oligomers (CPOs).[1] Among these, directly 1, 3-butadiyne-bridged conjugated CPOs have a special place owing to their intriguing structural, electronic, and optical properties. Usually, effective macrocyclizations require synthetic tricks. Sugiura et al. used L-shaped 5, 10-diaryl-15, 20-diethynylporphyrin as a key corner part for the synthesis of square meso-to-meso butadiyne-bridged planar CPOs.[2] Anderson and co-workers developed an elegant template-directed synthesis of meso-to-meso butadiynebridged circular CPOs using linear 5, 15-diaryl-10, 20-diethynylporphyrin precursors,[3] in which the structure of the template–substrate complex dictates the major CPO product. This approach has evolved into a conceptually new Verniertemplate synthesis.[3d, f] We have also reported Cu-mediated oxidative dimerization reaction of 5, 10, 15-triaryl-2, 18-diethynylporphyrins 1M that provided β-to-β 1, 3-butadiynebridged cyclic porphyrin dimers 2M in good yields.[4] It has been recognized that Pd-catalyzed oxidative coupling of acetylene can produce different products from the usual Cu-mediated reaction. As a representative example, Haley and co-workers have reported metal-dependent selective synthesis of two different dehydrobenzoannulenes by the intramolecular coupling reactions of single precursors, which is owing to the difference of their reaction mechanisms.[5] While still under debate, the mechanism of Cu-mediated oxidative butadiyne synthesis is proposed to involve a dimeric Cu acetylide arranged in a pseudo-trans configuration prior to reductive elimination (Scheme 1).[6] On the other hand, in Pdcatalyzed reactions, two ethynyl groups are proposed to be arranged in a cis geometry for reductive elimination.[7] In contrast to Haley and co-workers intramolecular reactions, metal-catalyzed intermolecular oxidative butadiyne formation is more difficult to control.[8, 9] Herein, we report preferential formation of trimers 3M by Pd-catalyzed coupling reactions of 1M.A solution of 1Ni in toluene and diisopropylamine was stirred at room temperature in the presence of catalytic amounts of PdCl2 (PPh3) 2 and CuI and two equivalents of 1, 4-benzoquinone as the oxidant. Separation by preparative gel permeation chromatography provided 2Ni [4] and 3Ni and in 9.3 and 72% yields, respectively (Scheme 2).[10] The MALDITOF mass spectrum of 3Ni displayed a parent ion peak at 2933.39 (calcd for C198H210N12Ni3, m/z 2933.49 [M]+). The