Heteroarylation of 1-azulenyl methyl sulfide: Two-step synthetic strategy for 1-methylthio-3-(heteroaryl)azulenes using the triflate of N-containing heterocycles

1-Azulenyl methyl sulfide reacts with highly electrophilic trifluoromethanesulfonates of N-heterocycles, that is, pyridine, isoquinoline, 1,10-phenanthroline, benzothiazole, quinoline, and acridine, to give 1-methylthio-3-(dihydroheteroaryl)azulenes in good yields. In the case of the reaction with the trifluoromethanesulfonate of pyridine, 1-methylthio-3- pyridylazulene was obtained directly under certain reaction conditions. Treatment of the 1-methylthio-3-(dihydroheteroaryl)-azulenes with KOH or tBuOK afforded the corresponding 1-methylthio-3-(heteroaryl)azulenes in good yields. The redox behavior of these 1-methylthio-3-(heteroaryl)azulenes was examined by cyclic voltammetry and differential pulse voltammetry.