An efficient synthesis 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‐ and 1,3‐bis(dihydroheteroaryl)azulene derivatives were readily converted into the desired 1‐heteroaryl‐ and 1,3‐bis(heteroaryl)azulenes by treatment with tBuOK in DMSO or KOH in EtOH in excellent yields. The pyridinium salts 26+·I– and 272+·2I– were also prepared by the reaction of 4a and 5a with methyl iodide. 1‐Heteroaryl‐ and 1,3‐bis(heteroaryl)azulenes exhibited a significant color change in acetic acid from that in dichloromethane due to the development of intramolecular charge‐transfer (CT) absorption bands.

Synthesis of 1-Heteroaryl-and 1,3-Bis(heteroaryl)azulenes: Electrophilic Heteroarylation of Azulenes with the Triflates of N-Containing Heteroarenes. -(SHOJI*, T.; ITO, S.; HIGASHI, J.; MORITA, N.; Eur. J. Org. Chem. 2011, 27, 5311-5322, http://dx.doi.org/10.1002/ejoc.201100498 ; Dep. Chem., Fac. Sci., Shinshu Univ., Matsumoto, Nagano 390, Japan; Eng.) -Nuesgen 08-168