Synthesis of azuleno[2,1-b]thiophenes by cycloaddition of azulenylalkynes with elemental sulfur and their structural, optical and electrochemical properties

Abstract

The reaction of several azulenylalkynes having an aryl substituent with elemental sulfur afforded the corresponding azuleno[2,1-b]thiophenes in moderate to good yields. Decarboxylation of an azuleno[2,1-b]thiophene derivative with an ester function was also achieved by treatment with 100% H₃PO₄. The structural features of the azuleno[2,1-b]thiophene derivatives were revealed by X-ray single-crystal analysis. The optical and electrochemical properties of the azuleno[2,1-b]thiophene derivatives were investigated by UV/Vis spectroscopy, voltammetry experiments and theoretical calculations.