Ethynylated 2H-cyclohepta[b]furan-2-ones 5-15 have been prepared by Pd-catalyzed alkynylation of 3-iodo-5-isopropyl-2H-cyclohepta[b]furan-2-one (2) with the corresponding ethynylarenes or the reaction of 2-iodothiophene with 3-ethynyl-5-isopropyl-2H-cyclohepta[b]furan-2-one (4) under Sonogashira-Hagihara conditions. Compounds 5-15 reacted with tetracyanoethylene in a formal [2+2] cycloaddition reaction, followed by ring opening of the initially formed [2+2] cycloadducts, cyclobutenes, to afford the corresponding 1,1,4,4-tetracyanobutadienyl (TCBD) chromophores 16-26 in excellent yields. The intramolecular charge-transfer interactions between the 2H-cyclohepta[b]furan-2-one ring and TCBD acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel TCBD derivatives 16-26 was examined by cyclic voltammetry and differential pulse voltammetry, which revealed multistep electrochemical reduction properties, depending on the number of TCBD units in the molecule. Moreover, a significant color change was observed by UV/Vis spectroscopy under electrochemical reduction conditions.

The reaction of azulenes with several sulfoxides in the presence of acid anhydrides to afford the corresponding 1-azulenylsulfonium and 1,3-azulenediyldisulfonium ions is reported. The subsequent conversion of these ions in high yields into 1-azulenyl methyl and phenyl sulfides and 1,3-bis(methyl-and phenylthio)azulenes through treatment with diethylamine is also described. Reaction of the 1-azulenyl sulfides with MCPBA afforded 1-azulenyl sulfoxides, which were then efficiently transformed into 1,1Ј-biazulene deriva-

Arylethynyl-2H-cyclohepta [b]furan-2-ones reacted with 7,7,8, 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 10 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. 15

Electrophilic ipso‐substitution reactions between 1,3,6‐tri‐tert‐butylazulene (2) and several electrophilic reagents were examined. Friedel–Crafts and Vilsmeier reactions of 2 gave the corresponding ipso‐substitution products in moderate to excellent yields. One of the ipso‐substitution products, 1,6‐di‐tert‐butyl‐3‐formylazulene (5), was converted in high yield into the synthetically more useful azulene derivative 1,6‐di‐tert‐butylazulene (1) by decarbonylation on treatment with pyrrole in acetic acid. Treatment of 2 with N‐[(trifluoromethyl)sulfonyl]pyridinium trifluoromethanesulfonate (TPT) unexpectedly afforded 1‐trifluoromethylthioazulene 10 and 1(8H)‐azulenone 11. Compound 2 also reacted with tetracyanoethylene (TCNE) to give an excellent yield of cycloaddition product 13, rather than the ipso‐substitution reaction product.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Ferrocenylmethylene‐bridged calix[4]azulene derivative 3 and bis(1‐azulenyl)ferrocenylmethane derivative 4 were obtained by the reaction of 6‐tert‐butylazulene (6) with ferrocenecarbaldehyde (7) in acetic acid. The new bis(1‐azulenyl)ferrocenylmethylium ion 5+ was also generated by the hydride abstraction reaction of the corresponding hydro derivative 4 with DDQ. The novel ferrocene‐substituted calix[4]azulene derivative 3 exhibit a reversible one‐step multi‐electron oxidation upon cyclic voltammetry.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)