Premium
Synthesis of Redox‐Active, Intramolecular Charge‐Transfer Chromophores by the [2+2] Cycloaddition of Ethynylated 2 H ‐Cyclohepta[ b ]furan‐2‐ones with Tetracyanoethylene
Author(s) -
Shoji Taku,
Higashi Junya,
Ito Shunji,
Okujima Tetsuo,
Yasunami Masafumi,
Morita Noboru
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201003628
Subject(s) - tetracyanoethylene , chemistry , intramolecular force , furan , cycloaddition , moiety , redox , photochemistry , cyclic voltammetry , sonogashira coupling , medicinal chemistry , chromophore , isopropyl , electrochemistry , stereochemistry , organic chemistry , catalysis , palladium , electrode
Ethynylated 2 H ‐cyclohepta[ b ]furan‐2‐ones 5 – 15 have been prepared by Pd‐catalyzed alkynylation of 3‐iodo‐5‐isopropyl‐2 H ‐cyclohepta[ b ]furan‐2‐one ( 2 ) with the corresponding ethynylarenes or the reaction of 2‐iodothiophene with 3‐ethynyl‐5‐isopropyl‐2 H ‐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 2 H ‐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.