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Formation of Azulene‐Embedded Nanographene: Naphthalene to Azulene Rearrangement During the Scholl Reaction
Author(s) -
Han Yi,
Xue Zibo,
Li Guangwu,
Gu Yanwei,
Ni Yong,
Dong Shaoqiang,
Chi Chunyan
Publication year - 2020
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201915327
Subject(s) - azulene , helicene , naphthalene , ring (chemistry) , chemistry , photochemistry , nuclear magnetic resonance spectroscopy , molecule , crystallography , computational chemistry , stereochemistry , organic chemistry
Incorporation of a non‐hexagonal ring into a nanographene framework can lead to new electronic properties. During the attempted synthesis of naphthalene‐bridged double [6]helicene and heptagon‐containing nanographene by the Scholl reaction, an unexpected azulene‐embedded nanographene and its triflyloxylated product were obtained, as confirmed by X‐ray crystallographic analysis and 2D NMR spectroscopy. A 5/7/7/5 ring‐fused substructure containing two formal azulene units is formed, but only one of them shows an azulene‐like electronic structure. The formation of this unique structure is explained by arenium ion mediated 1,2‐phenyl migration and a naphthalene to azulene rearrangement reaction according to an in‐silico study. This report represents the first experimental example of the thermodynamically unfavorable naphthalene to azulene rearrangement and may lead to new azulene‐based molecular materials.