Konishi A.
*
Morinaga A.
Yasuda M.
* Osaka University, Japan
Construction of Polycyclic π-Conjugated Systems Incorporating an Azulene Unit Following
the Oxidation of 1,8-Diphenyl-9,10-bis(phenylethynyl)phenanthrene.
Chem. Eur. J. 2018;
24: 8548-8552
Key words
azulenes - non-alternate hydrocarbons - polycyclic aromatic hydrocarbons
Significance
Incorporation of heptagons and pentagons into a polycyclic aromatic hydrocarbon (PAH)
core leads to changes in the molecular geometry and electronic properties of the
original PAH. This report demonstrates the use of silver(I) cations to achieve an
efficient synthesis of an azulene-embedded PAH 2, which is a challenging issue that is plagued by limited methodologies.
Comment
Two-electron oxidation of the silver(I) ion promoted a three-fold transannulation
reaction between the aromatic and acetylene units of 1 resulting in the selectively embedded azulenium cation 2H+
, which could be subsequently deprotonated by trimethylamine to afford the neutral
azulene-embedded PAH 2. Compound 2 exhibited a low-energy absorption band featuring characteristics of the non-alternant
moiety, along with reversible one-electron redox events for the oxidation or reduction
of 2, resulting in tropylium cation or cyclopentadienyl anion scaffolds, respectively.
