Synthesis of push-pull chromophores by the sequential [2+2] cycloaddition of 1-azulenylbutadiynes with tetracyanoethylene and tetrathiafulvalene

Azulene-substituted butadiynes have been prepared by Cu-mediated cross- and homo-coupling reactions. The azulene-substituted butadiynes reacted with tetracyanoethylene in a formal [2 + 2] cycloaddition reaction to afford the corresponding 1,1,4,4-tetracyanobutadiene chromophores, in excellent yields. Further [2 + 2] cycloaddition with TTF and TCNE gave novel donor-acceptor chromophores and novel azulene-substituted 6,6-dicyanofulvene derivatives.ArticleORGANIC & BIOMOLECULAR CHEMISTRY. 10(41):8308-8313 (2012)journal articl

Synthesis of 2-Azulenyl-1,1,4,4-tetracyano-3-ferrocenyl-1,3-butadienes by [2+2] Cycloaddition of (Ferrocenylethynyl)azulenes with Tetracyanoethylene

1-, 2-, and 6-(Ferrocenylethynyl)azulene derivatives 1016 have been prepared by palladium-catalyzed alkynylation of ethynylferrocene with the corresponding haloazulenes under SonogashiraHagihara conditions. Compounds 1016 reacted with tetracyanoethylene (TCNE) in a [2+2] cycloadditioncycloreversion reaction to afford the corresponding 2-azulenyl-1,1,4,4,-tetracyano-3-ferrocenyl-1,3-butadiene chromophores 1723 in excellent yields. The redox behavior of the novel azulene chromophores 1723 was examined by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.ArticleCHEMISTRY-A EUROPEAN JOURNAL. 19(18):5721-5730 (2013)journal articl

Synthesis of 2-and 6-thienylazulenes by palladium-catalyzed direct arylation of 2-and 6-haloazulenes with thiophene derivatives

Preparation of 2- and 6-thienylazulene derivatives was established by the palladium-catalyzed direct cross-coupling reaction of 2- and 6-haloazulenes with the corresponding thiophene derivatives in good yield. Several thienylazulene derivatives were also used in the reaction with 2-chloroazulene derivatives in the presence of the palladium-catalyst to afford the thiophene derivatives with two azulene functions in good yield.ArticleORGANIC & BIOMOLECULAR CHEMISTRY. 23(66):10191-10197 (2015)journal articl

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

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.ArticleCHEMISTRY-A EUROPEAN JOURNAL. 15(18):11903-11912 (2014)journal articl

Synthesis, Properties and Redox Behavior of Ene-Diyne Scaffolds Bearing 1- and 2-Azulenyl Groups at the Periphery

Ene-diyne systems possessing 1- and 2-azulenyl groups at the periphery were prepared by palladium-catalyzed cross-coupling reaction of 1- and 2-ethynylazulenes with 9-di-bromomethylene-9H-fluorene and 9,10-bis(dibromomethylene)-9,10-dihydroanthracene or 2-iodoazulene with 9,10-bis(diethynylmethylene)-9,10-dihydroanthracene under Sonogashira-Hagihara conditions. The redox behavior of the ene-diyne compounds was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Moreover, a significant color change of the ene-diyne derivatives was observed with visible spectroscopy under electrochemical reduction conditions.ArticleEUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2013(5):957-964 (2013)journal articl

Synthesis of donor-acceptor chromophores by the [2+2] cycloaddition of arylethynyl-2H-cyclohepta[b]furan-2-ones with 7,7,8,8-tetracyanoquinodimethane

Arylethynyl-2H-cyclohepta[b]furan-2-ones reacted with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2 + 2] cycloaddition reaction, followed by ring opening of the initially formed cyclobutene derivatives, to afford the corresponding dicyanoquinodimethane (DCNQ) chromophores in excellent yields. The intramolecular charge-transfer (ICT) interactions between the 2H-cyclohepta[b]furan-2-one ring and DCNQ acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel DCNQ derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties depended on the number of DCNQ units in the molecule. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.ArticleORGANIC & BIOMOLECULAR CHEMISTRY. 10(12):2431-2438 (2012)journal articl

Synthesis of 2-Aryl- and 6-Heteroaryl-1,3-di(4-pyridyl)azulenes by Katritzky’s Pyridylation of 2-Aryl- and 6-Heteroarylazulenes

Preparation of 2-aryl- and 6-heteroarylazulenes 2-6 and 8-10 was established by the palladium-catalyzed cross-coupling reaction of the corresponding haloazulenes with lithium aryl- and heteroarylmagnesium ate complexes, which were readily prepared from the corresponding aryl and heteroaryl halides. The reaction of 2-6 and 8-10, except for 3 and 8, with pyridine in the presence of Tf2O, followed by treatment with KOH in MeOH afforded the corresponding 2-aryl- and 6-heteroary1-1,3-di(4-pyridyl)azulenes 11-16 in good yields.ArticleHETEROCYCLES. 89(11):2588-2603 (2014)journal articl

Synthesis, Properties, and Redox Behavior of 1,1,4,4-Tetracyano-2-ferrocenyl-1,3-butadienes Connected by Aryl, Biaryl, and Teraryl Spacers

Aryl-substituted 1,1,4,4-tetracyano-1,3-butadienes (FcTCBDs) and bis(1,1,4,4-tetracyanobutadiene)s (bisFcTCBDs), possessing a ferrocenyl group on each terminal, were prepared by the reaction of a variety of alkynes with tetracyanoethylene (TCNE) in a [2+2] cycloaddition reaction, followed by retro-electrocyclization of the initially formed [2+2] cycloadducts (i.e., cyclobutene derivatives). The characteristic intramolecular charge transfer (ICT) between the donor (ferrocene) and acceptor (TCBD) moieties were investigated by using UV/ Vis spectroscopy. The redox behaviors of FcTCBDs and bis-FcTCBDs were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their properties of multi-electron transfer depending on the number of ferrocene and TCBD moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions.ArticleCHEMISTRY-A EUROPEAN JOURNAL. 23(21):402-409 (2015)journal articl

Synthesis of 1,2 '-Biazulenes by Palladium-Catalyzed Unusual Homocoupling Reaction of 1-Haloazulenes in the Presence of Ferrocene

The synthesis of 1,2-biazulenes was established by palladium-catalyzed homocoupling reactions of the corresponding 1-haloazulenes in the presence of ferrocene. The optical properties of the novel 1,2-biazulenes were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behaviors of 1,2-biazulenes were also examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV).ArticleSYNTHESIS. 89(11):2438-2448 (2016)journal articl

Synthesis and Properties of Azulene-Substituted Donor-Acceptor Chromophores Connected by Arylamine Cores

1-Ethynylazulenes connected by several arylamine cores reacted with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2+2] cycloaddition-cycloreversion reaction to afford the corresponding tetracyanobutadiene (TCBD) and dicyanoquinodimethane (DCNQ) chromophores, respectively, in excellent yields. The intramolecular charge-transfer (ICT) characters between the donor (azulene and arylamine cores) and acceptor (TCBD and DCNQ units) moieties were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the new TCBD and DCNQ derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions.ArticleEUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2013(34):7785-7799 (2013)journal articl