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
Azulene reacts with highly electrophilic trifluoromethanesulfonates of N-containing heterocycles to give 1-dihydroheteroaryl and 1,3.-bis(dihydroheteroaryl)azulene derivatives in a good yield. Treatment of the dihydroheteroarylazulene derivatives with KOH or tert-BuOK afforded 1-heteroaryl and 1,3-bis(heteroaryl)azulenes in a good yield. (c) 2006 Elsevier Ltd. All rights reserved.
Synthesis of 1-Heteroaryl- and 1,3-Bis(heteroaryl)azulenes: Electrophilic Heteroarylation of Azulenes with the Triflates of N-Containing Heteroarenes
An efficientsynthesis of 1-heteroaryl- and 1,3-bis(heteroaryl)azulenes was established by electrophilic substitution. The reaction of azulenes and 1,1'-biazulene with the triflate of N-containing heteroarenes proceeded smoothly in the presence of excess heteroarenes to afford the corresponding 1-dihydroheteroaryl- and 1,3-bis(dihydroheteroaryl)azulene derivatives in good yields. The 1-dihydroheteroaryl-