Synthesis and Properties of Thiophene-Fused Thiopyrylium Salts

A new family of thiophene-fused thiopyrylium salts has been synthesized via Lewis-acid-induced Rieche formylation, followed by an intramolecular Friedel–Crafts cyclization of a series of diarylthioethers. Moreover, in the case of diarylthioethers that bear formyl groups, Lewis-acid-promoted intramolecular cyclizations afforded novel thiophene-fused bisthiopyrylium salts in good yield. The electronic structures of the new compounds were determined experimentally by NMR and UV–vis absorption spectroscopy and theoretically investigated by density functional theory calculations. The results of our examinations revealed effective conjugation of the π-electrons over the entire linearly fused heteroacene framework.