Fluorescent naphthyl- and anthrylazoles from the catalytic coupling of phenylazoles with internal alkynes through the cleavage of multiple, C-H bonds
Fluorescent naphthyl- and anthrylazoles from the catalytic coupling of phenylazoles with internal alkynes through the cleavage of multiple, C-H bonds
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DOI：
10.1002/anie.200800924
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发表时间：
2008-01-01
影响因子：
16.6
通讯作者：
Miura, Masahiro
中科院分区：
文献类型：
--
作者：
Umeda, Nobuyoshi;Tsurugi, Hayato;Miura, Masahiro
多环芳香族和杂芳香族化合物由于其电化学和光化学性质，以及作为π共轭功能材料如有机半导体和发光材料的应用受到了广泛的关注具有凝聚芳香族核心的聚芳基衍生物由于其稳定性、增强的电荷传输能力和由芳基带来的固态荧光特性而受到特别关注。[2 - 4]其中一个有趣的例子是1,3,6,8 -四苯基芘，它被证明适用于具有场效应晶体管特性的有机发光二极管近年来，合成了更多的空间拥塞的四芳基芘，并对其固态发射性能进行了测试多芳基化化合物通常是由母体芳香族化合物溴化，随后与芳基金属试剂交偶联而得。由于交叉偶联反应通常受到空间体积的阻碍，用这种方法构建更密集的芳基化芳烃是有问题的另一种策略包括聚芳基苯和环戊二烯酮之间的Diels-Alder反应这种方法可以合成完全芳基化的萘和蒽单元，但是，由于体积大的试剂之间存在空间排斥，产品产率很低与苯相比，二芳基乙炔是更有效和更容易获得的构建块。因此，通过ArX与两个炔分子的偶联，过渡金属催化的芳香同源化[7]已经发展成为具有扩展芳香核的高取代芳烃的高效且易于调节的合成方案在本文中，我们报告了我们的新发现，苯基唑经历了一种高级类型的芳香同源化，在铑催化下[8g， h]通过两个CÀH键[9,10]裂解得到（1,2,3,4 -四芳基萘-5-基）唑；杂环作为一种有效的导向基团，增强了产物的荧光特性（vide infra）。此外，对合适的苯基唑底物进行类似处理，用四个等效的炔导致四个CÀH键的裂解，以获得高荧光的聚苯基化蒽（1:4偶联产物）。在最初的尝试中，1-苯基吡唑（1a）被用作与二苯乙炔（2a）反应的典型的唑底物。通过对不同反应条件的考察（见辅助资料）表明，[{Cp* RhCl2} 2]/C5H2Ph4（1,2,3,4 -四苯基环戊二烯）和Cu (OAc) 2·H2O分别是催化剂和氧化剂的合适选择。因此，在最佳条件下（1 mol%[{Cp* RhCl2} 2], 4mol% C5H2Ph4, 1等量Cu-(OAc) 2·H2O， DMF, 808C, N2, 6h），以93%的收率得到1-（1,2,3,4 -四苯基萘-5-基）吡唑（3a） （R1= R2= H, R3= R4= Ph，式(1)）；表1，条目1)。
Polycyclic aromatic and heteroaromatic compounds have attracted considerable attention because of their electrochemical and photochemical properties, and their application as π-conjugated functional materials such as organic semiconductors and luminescent materials.[1] Polyarylated derivatives with condensed aromatic cores are of particular interest because of their stability, their enhanced ability to transport charge, and their fluorescent properties in the solid-state that are brought about by the aryl groups.[2–4] Among the interesting examples is 1, 3, 6, 8-tetraphenylpyrene, which was shown to be applicable to organic light-emitting diodes with field-effect transistor characteristics.[2] Recently, more sterically congested tetraarylpyrenes were synthesized and their solid-state emission properties were examined.[3] Multiply arylated compounds are usually prepared by bromination of the parent aromatic compounds with subsequent cross-coupling with arylmetal reagents. Since the crosscoupling reaction is usually hampered by steric bulk, the construction of more densely arylated arenes by this method is problematic.[5] An alternative strategy includes the Diels–Alder reaction between polyarylated benzynes and cyclopentadienones.[4] This method enables the synthesis of exhaustively arylated naphthalene and anthracene units, however, the product yields are low because of steric repulsion between the bulky reagents.[6] Compared to benzyne, diarylacetylenes are more effective and readily available building blocks. Thus, transition-metal-catalyzed aromatic homologation [7] by the coupling of ArX with two alkyne molecules has been developed as an efficient and easily tunable synthetic protocol for highly substituted arenes possessing extended aromatic cores.[8] Herein, we report our new findings that phenylazoles undergo an advanced type of aromatic homologation, by the cleavage of two CÀH bonds [9, 10] under rhodium catalysis,[8g, h] to give (1, 2, 3, 4-tetraarylnaphthalen-5-yl) azoles; the heterocycle functions as an effective directing group and enhances the fluorescent properties of the products (vide infra). Furthermore, similar treatment of a suitable phenylazole substrate with four equivalents of an alkyne leads to the cleavage of four CÀH bonds to afford a polyarylated anthracene (1: 4 coupling product) that is highly fluorescent.In an initial attempt, 1-phenylpyrazole (1a) was used as a typical azole substrate for the reaction with diphenylacetylene (2a). The examination of different reaction conditions (see the Supporting Information) revealed that [{Cp* RhCl2} 2]/C5H2Ph4 (1, 2, 3, 4-tetraphenylcyclopentadiene) and Cu (OAc) 2· H2O are suitable choices for the catalyst and the oxidant, respectively. Thus, under optimal conditions (1 mol%[{Cp* RhCl2} 2], 4mol% C5H2Ph4, 1equiv Cu-(OAc) 2· H2O in DMF at 808C for 6h under N2) the 1: 2 coupling product, 1-(1, 2, 3, 4-tetraphenylnaphthalen-5-yl) pyrazole (3a), was obtained in 93% yield (R1= R2= H, R3= R4= Ph in Equation (1); Table 1, entry 1).