title: 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.
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.
authors.affiliation: Department of Chemistry, Faculty School of Science, Shinshu University, Matsumoto 390-8621, Nagano (Japan), Fax: (+81) 263-37-2476; Department of Material Science, Graduate School of Science and Technology, Shinshu University, Matsumoto 390-8621, Nagano (Japan). tshoji@shinshu-u.ac.jp.
authors.forename: Taku
authors.initials: T
authors.lastname: Shoji
authors.forename: Mitsuhisa
authors.initials: M
authors.lastname: Maruyama
authors.forename: Akifumi
authors.initials: A
authors.lastname: Maruyama
authors.forename: Shunji
authors.initials: S
authors.lastname: Ito
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Okujima
authors.forename: Kozo
authors.initials: K
authors.lastname: Toyota
keywords: azulene; cycloadditions; donor-acceptor system; electrochemistry; redox chemistry