Synthesis of 5-heteroaryl- and 5,7-bis(heteroaryl)azulenes by electrophilic substitution of 1,3-di-terf-butylazulene with triflates of N-containing heterocycles

Taku Shoji, Shunji Ito, Kozo Toyota, Noboru Morita

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

An efficient synthesis of 5-heteroaryl- and 5,7-bis(heteroaryl)azulene derivatives was established for first time. The reaction proceeded through electrophilic substitution of 1,3di-tert-butylazulene (1) with the triflates of N-containing heterocycles, in the presence of excess heterocycles, in good yields. The presumed intermediates, 5-(dihydroheteroaryl)azulene derivatives were also available by the reaction with several N-containing heterocycles in the presence of Tf2O under milder reaction, conditions. Treatment of the 5-(dihydroheteroaryl)azulene derivatives with KOH readily gave the desired 5-(heteroaryl)azulene derivatives. Unexpectedly, N(5-azulenyl)pyridinium triflate 17 was also obtained by the reaction of 1 with (trifluoromethylsulfonyl)pyridinium trifluoromethanesulfonate (TPT). 5-Heteroaryl- and 5,7-bis(heteroaryl)azulene derivatives exhibited a significant color change in acetic acid compared to those in dichloromethane due to the development of intramolecular charge-transfer (CT) absorption bands. The redox behavior of these new azulene derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV)

Original languageEnglish
Pages (from-to)1059-1069
Number of pages11
JournalEuropean Journal of Organic Chemistry
Issue number6
DOIs
Publication statusPublished - 2010 Feb 1

Keywords

  • Azulene derivatives
  • Electrochemistry
  • Electrophilic substitution
  • Heterocycles
  • Solvatochromism

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry

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