Azulene-Based Donor-Acceptor Systems: Synthesis, Optical, and Electrochemical Properties

First published: 07 Aug 2017We describe the synthesis and properties of azulene-substituted 1,1,4,4-tetracyanobutadienes (AzTCBDs) and heteroazulenyl TCBDs. TCBD derivatives were prepared in good to excellent yields through reaction of the corresponding 1-ethynylazulenes with tetracyanoethylene (TCNE). In contrast, the reaction between propargyl alcohols and the 1-azulenyl group in TCNE generated 2-aminofuran derivatives, which were transformed into 6-aminofulvenes with a 1-azulenyl substituent upon treatment with several amines. The optical and electrochemical properties of the AzTCBDs were clarified by UV/Vis and voltammetry. The AzTCBD derivatives exhibited electrochromism, showing a multi-step color change under electrochemical redox conditions. The multistage redox properties of AzTCBDs could be useful for the development of novel organic electronic materials.ArticleCHEMISTRY-A EUROPEAN JOURNAL. 95(1):16696-16709 (2017)journal articl

First synthesis of 1-(indo1-2-yl)azulenes by the Vilsmeier-Haack type arylation with triflic anhydride as an activating reagent

Azulene derivatives reacted with 2-indolinones in the presence of triflic anhydride (Tf2O) to afford 1-(indo1-2-yl)azulenes in good yields. In the cases of the reaction of 6-tert-butyl-1-(methylthio)azulene (11) and 1-(1,4-dihydropyridin-4-yl)azulene 14, 1,1'-biazulene derivative 24 and 1-(indo1-2-yl)azulene (2) were obtained under the similar reaction conditions, respectively, instead of the presumed electrophilic substitution products.ArticleTETRAHEDRON LETTERS. 53(12):1493-1496 (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 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 1-(pyridyl, quinolyl, and isoquinolyl)azulenes by Reissert-Henze type reaction

Azulene derivatives reacted with N-oxide of several heterocycles in the presence of trifluoromethanesultonic anhydride (Tf(2)O) to afford 1-(pyridyl, quinolyl, and isoquinolyl)azulenes in good yield, respectively. In the case of the reaction with the 1-azulenyl methyl sulfide (12), 1,1'-biazulene derivative 13 was obtained under the similar reaction conditions. The first synthesis of unsymmetrical 1,3-di(pyridyl)azulene derivative was also established via our new preparation method following the electrophilic pyriclinylation using the reaction with pyridine in the presence of Tf(2)O.ArticleTETRAHEDRON LETTERS. 51(39):5127-5130 (2010)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

White Patchy Materials Formed in a Scoriacious Road-cut Profile on Miyake Island(Plant Production Science Soil Science)

Sulfurous gas, sulfur or sulfates are frequently contained in volcanic ejecta. We found white patchy materials (WPM) in a road-cut profile on Miyake Island, Japan. The layer containing WPM consists of scoria deposit in 1874. The major materials we identified in the WPM were CaSO_4・2H_2O and amorphous silica according to X-ray diffraction and energy dispersive X-ray analyses. A possible process for crystallization of CaSO_4・2H_2O in the WPM is the dissolution of CaSO_4・2H_2O contained in the overlying 2000 ash and its re-precipitation on the surface of the scoriacious road-cut profile. Emission of sulfur dioxide gas, converted to sulfuric acid in water, has been so abundant since the 2000 eruption that we further examined reaction products between crushed scoria and dilute H_2SO_4 (0.1-2.5mol L^). CaSO_4・2H_2O was also identified in the reaction products as well as alunogen, iron sulfate, etc. Because alunogen is highly soluble in water, CaSO_4・2H_2O was the major crystalline product after rinsing with water

Synthesis of 1-azulenyl ketones by Bronsted acid mediated hydration of 1-azulenylalkynes

Preparation of 1-azulenyl ketones was achieved by metal-free hydration of 1-azulenylalkynes using trifluoroacetic acid as a Bronsted acid in good to excellent yields. The reaction was accomplished at a relatively low temperature with complete regio-selectivity and compatibility of several functional groups.ArticleRSC ADVANCES. 90(1):78303-78306 (2016)journal articl