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Electrophilic ipso ‐Substitution and Some Unique Reaction Behavior of 1,3,6‐Tri‐ tert ‐butylazulene
Author(s) -
Shoji Taku,
Ito Shunji,
Okujima Tetsuo,
Higashi Junya,
Yokoyama Ryuji,
Toyota Kozo,
Yasunami Masafumi,
Morita Noboru
Publication year - 2009
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200801078
Subject(s) - chemistry , electrophilic substitution , substitution reaction , azulene , medicinal chemistry , electrophilic aromatic substitution , tetracyanoethylene , acetic anhydride , electrophile , yield (engineering) , cycloaddition , decarbonylation , organic chemistry , materials science , metallurgy , catalysis
Electrophilic ipso ‐substitution reactions between 1,3,6‐tri‐ tert ‐butylazulene ( 2 ) and several electrophilic reagents were examined. Friedel–Crafts and Vilsmeier reactions of 2 gave the corresponding ipso ‐substitution products in moderate to excellent yields. One of the ipso ‐substitution products, 1,6‐di‐ tert ‐butyl‐3‐formylazulene ( 5 ), was converted in high yield into the synthetically more useful azulene derivative 1,6‐di‐ tert ‐butylazulene ( 1 ) by decarbonylation on treatment with pyrrole in acetic acid. Treatment of 2 with N ‐[(trifluoromethyl)sulfonyl]pyridinium trifluoromethanesulfonate (TPT) unexpectedly afforded 1‐trifluoromethylthioazulene 10 and 1(8 H )‐azulenone 11 . Compound 2 also reacted with tetracyanoethylene (TCNE) to give an excellent yield of cycloaddition product 13 , rather than the ipso ‐substitution reaction product.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)