Synthesis and properties of 6-methoxy- and 6-dimethylamino-1-methylthio- and 1,3-bis(methylthio)azulenes and triflic anhydride-mediated synthesis of their biaryl derivatives

6-Methoxy- and 6-dimethylaminoazulenes with methylthio groups at the 1- or 1,3-positions have been prepared by electrophilic substitution of the corresponding azulenes with DMSO in the presence of acid anhydride, followed by treatment with Et₃N. The products, 1-methylthioazulenes, reacted with Tf₂O to afford the corresponding 1,1′-biazulene derivatives in moderate yields. The redox behavior of these azulene and 1,1′-biazulene derivatives was examined by cyclic voltammetry (CV), which revealed reversible electron transfers under electrochemical oxidation conditions. 6-Dimethylamino-1,3-bis(methylthio)azulenes with a heteroaiyl group at the 2-position were also prepared by the reaction of 6-dimethylamino-1,3- bis(methylthio)azulene with triflates of iV-containing heterocycles, i.e., pyridine, quinoline, isoquinoline, acridine, and 1,10-phenanthroline, followed by treatment with KOH in alcohols.