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Contraction of π‐Conjugated Rings upon Oxidation from Cyclooctatetraene to Benzene via the Tropylium Cation
Author(s) -
Tamoto Akira,
Aratani Naoki,
Yamada Hiroko
Publication year - 2017
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.201704008
Subject(s) - cyclooctatetraene , cycloheptatriene , chemistry , aromatization , benzene , conjugated system , ring (chemistry) , derivative (finance) , photochemistry , medicinal chemistry , organic chemistry , catalysis , polymer , molecule , financial economics , economics
We have serendipitously discovered a unique transformation of a cyclooctatetraene derivative 1 into a cycloheptatriene spirolactone 3 upon oxidation, which is the first such transformation reported in 60 years. Product 3 could be reversibly interconverted into the aromatic tropylium cation 3H + by acid/base treatment, which was accompanied by drastic spectroscopic changes. The resultant cycloheptatriene could be further converted into benzene upon oxidation. We characterized all the key structures by X‐ray studies. Eventually, the π‐conjugated ring size shrinks from 8 to 7, then finally to 6 upon oxidation, in the direction of the stronger aromatization.