Synthesis of 1,3‐Bis(tetracyano‐2‐azulenyl‐3‐butadienyl)azulenes by the [2+2] Cycloaddition–Retroelectrocyclization of 1,3‐Bis(azulenylethynyl)azulenes with Tetracyanoethylene |
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| Authors: | Dr. Taku Shoji Mitsuhisa Maruyama Akifumi Maruyama Prof. Dr. Shunji Ito Dr. Tetsuo Okujima Prof. Dr. Kozo Toyota |
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| Affiliation: | 1. Department of Chemistry, Faculty School of Science, Shinshu University, Matsumoto 390‐8621, Nagano (Japan), Fax: (+81)?263‐37‐2476;2. Department of Material Science, Graduate School of Science and Technology, Shinshu University, Matsumoto 390‐8621, Nagano (Japan);3. Graduate School of Science and Technology, Hirosaki University, Hirosaki 036‐8561, Aomori (Japan);4. Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790‐8577, Ehime (Japan);5. Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980‐8578, Miyagi (Japan) |
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| Abstract: | 1,3‐Bis(azulenylethynyl)azulene derivatives 9–14 have been prepared by palladium‐catalyzed alkynylation of 1‐ethynylazulene 8 with 1,3‐diiodoazulene 1 or 1,3‐diethynylazulene 2 with the corresponding haloazulenes 3–7 under Sonogashira–Hagihara conditions. Bis(alkynes) 9–14 reacted with tetracyanoethylene (TCNE) in a formal [2+2] cycloaddition–retroelectrocyclization reaction to afford the corresponding new bis(tetracyanobutadiene)s (bis(TCBDs)) 15–20 in excellent yields. The redox behavior of bis(TCBD)s 15–20 was examined by using CV and differential pulse voltammetry (DPV), which revealed their reversible multistage reduction properties under the electrochemical conditions. Moreover, a significant color change of alkynes 9–14 and TCBDs 15–20 was observed by visible spectroscopy under the electrochemical reduction conditions. |
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| Keywords: | azulene cycloadditions donor– acceptor system electrochemistry redox chemistry |
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