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A Zwitterionic, 10 π Aromatic Hemisphere
Author(s) -
Hafezi Nema,
Shewa Wondimagegn T.,
Fettinger James C.,
Mascal Mark
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201708521
Subject(s) - aromaticity , chemistry , deprotonation , annulene , benzene , sulfonium , ammonium , stacking , crystallography , medicinal chemistry , computational chemistry , salt (chemistry) , molecule , organic chemistry , ion
A new concept in anionic 10 π aromaticity is described by the embedding of a compensating charge within an aromatic cyclononatetraenide ring by the symmetric superposition of an alkyl ammonium bridge. This is accomplished by the methylation of azatriquinacene to give a quaternary ammonium salt, followed by oxidation to the tetraene and final deprotonation. The resulting zwitterion is a stable [9]annulene with strong aromaticity as shown by its degree of C−C bond equalization and a nucleus‐independent chemical shift value lower than that of benzene. The solid‐state structure shows an eclipsed stacking motif with the electron‐poor ammonium methyl groups occupying the electron‐rich cavity of the aromatic bowl.