Reaction of azulenes with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate (TPT) and synthesis of the parent azulene.
2-Azulenyl trifluoromethanesulfonate was prepared by the reaction of 2-hydroxyazulene with trifluoromethanesulfonic anhydride in the presence of triethylamine as a base. Under the use of pyridine, 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate further reacted with 2-azulenyl trifluoromethanesulfonate to give 1-(1-trifluoromethanesulfonyl-1,4-dihydropyridin-4-yl)azulenyl trifluoromethanesulfonate. Moreover, we found that azulenes also reacted with 1-trifluoromethanesulfonylpyridinium trifluoromethanesulfonate to give 4-(1-azulenyl)-1,4-dihydropyridine derivatives and 6-(1-azulenyl)-1-trifluoromethanesulfonyl-1-aza-hexa-1,3,5-triene depending on the reaction conditions. 2-Azulenyl trifluoromethanesulfonate was converted finally into the parent azulene in excellent yield by palladium-catalyzed reduction using formic acid as a reducing reagent.
Ito
Shunji
S
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
Yokoyama
Ryuji
R
Okujima
Tetsuo
T
Terazono
Tomomi
T
Kubo
Takahiro
T
Tajiri
Akio
A
Watanabe
Masataka
M
Morita
Noboru
N
D052176:Azulenes; D003508:Cycloheptanes / Q000138:chemical synthesis / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000737:chemistry*
D052176:Azulenes; D003508:Cycloheptanes; D008698:Mesylates; D011726:Pyridinium Compounds; C005525:azulene; C012077:trifluoromethanesulfonic acid