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Facile Ring Enlargement of Azulene to Give the Cyclopentacyclononene System by Dipolar Cycloaddition
Author(s) -
Hafner Klaus,
Lindner Hans Jörg,
Ude Werner
Publication year - 1979
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.197901621
Subject(s) - azulene , ring (chemistry) , cycloaddition , benzene , derivative (finance) , chemistry , aryne , medicinal chemistry , stereochemistry , photochemistry , organic chemistry , catalysis , financial economics , economics
The cyclopentacyclononene derivative (3). the first compound to contain this ring system and also the first stable cyclononatetraene not to have an annelated benzene ring, has been synthesized from the “ethanoazulene” (1). This synthesis is possible because azulene reacts readily with the ynamine (2) , to give the tricyclic species (4). Although 4,6,8‐methylazulene initially gives the desired ring system (5) , immediate transannular bonding occurs. The bracket in (1) prevents this reaction.