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.