Synthesis, Reactivity, and Properties of Benz[a]azulenes via the [8 + 2] Cycloaddition of 2-H-Cyclohepta[b]furan-2-ones with an Enamine
Synthesis, Reactivity, and Properties of Benz[a]azulenes via the [8 + 2] Cycloaddition of 2-H-Cyclohepta[b]furan-2-ones with an Enamine
复制标题
2-H-环庚[b]呋喃-2-酮与烯胺的[8 2]环加成反应苯并[a]薁环烯的合成、反应性和性质
DOI：
10.1021/acs.joc.2c00133
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Ito Shunji
中科院分区：
文献类型：
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作者：
Shoji Taku;Yamazaki Akari;Katoh Ryuzi;Shimamura Konomi;Sakai Rina;Yasunami Masafumi;Okujima Tetsuo;Ito Shunji
以4-叔丁基环己酮和吡咯烷为原料，由2- h -环庚[b]呋喃-2-酮与烯胺反应为起点，经过三步反应得到了同时具有甲酰基和叔丁基的苯并[a]azulenes。随后，通过在100% h3po4中加热苯并[a]azulene衍生物来消除甲酰基和叔丁基，得到高产率不含这些取代基的苯并[a]azulene。就产物收率而言，该方法是迄今为止报道的合成母体苯并[a]azulene的最佳方法。通过丙二酸二甲酯缩合和Brønsted酸介导的分子内环化反应，研究了含甲酰基的苯并[a]azulene衍生物转化为环庚[a]苊-3- 1衍生物。通过核磁共振、NICS计算和单晶x射线结构分析揭示了苯并[a]azulene衍生物的结构特征，包括键的改变。采用紫外/可见光谱、荧光光谱和伏安法研究了一系列苯并[a]azulene衍生物的光学和电化学性质。结果，我们发现一些苯并[a]azulene衍生物在酸性介质中表现出显著的发光。此外，具有吸电子基团的苯并[a]azulene衍生物和环庚[a]苊-3- 1衍生物在电化学氧化还原条件下的光谱变化具有良好的可逆性。
Starting with the reaction of 2H-cyclohepta[b]furan-2-ones with an enamine, which was prepared from 4-tert-butylcyclohexanone and pyrrolidine, benz[a]azulenes having both formyl andtert-butyl groups were obtained in the three-step sequence. Subsequently, both the formyl andtert-butyl groups were eliminated by heating the benz[a]azulene derivatives in 100% H3PO4to give benz[a]azulenes without these substituents in high yields. In terms of product yield, this method is the best one ever reported for the synthesis of the parent benz[a]azulene so far. The conversion of the benz[a]azulene derivatives with a formyl group into cyclohept[a]acenaphthylen-3-one derivatives was also investigatedviaKnoevenagel condensation with dimethyl malonate, followed by Brønsted acid-mediated intramolecular cyclization. The structural features including the bond alternation in the benz[a]azulene derivatives were revealed by NMR studies, NICS calculations, and a single-crystal X-ray structural analysis. The optical and electrochemical properties of a series of benz[a]azulene derivatives were evaluated by UV/Vis, fluorescence spectroscopy, and voltammetry experiments. As a result, we found that some benz[a]azulene derivatives showed remarkable luminescence in acidic media. In addition, the benz[a]azulene derivatives with the electron-withdrawing group and cyclohept[a]acenaphthylen-3-one derivative displayed good reversibility in the spectral changes under the electrochemical redox conditions.