Synthesis and properties of thieno[2,3-d:5,4-d’]bisthiazoles and their oxidized derivatives: Thionyl chloride as a sulfurative ring-fusing reagent towards thiophene-based ring-fused heteroaromatic compounds

Abstract A new route to thiophene-ring-fused compounds with thionyl chloride as a sulfur source was developed. Use of an excess amount thionyl chloride directly gave the corresponding thiophene-ring-fused compound via further reduction of generated thiophene-S-oxide with excess thionyl chloride in some cases. One-pot reduction with tributylphosphine also gave thiophene-ring-fused compounds in good yields, and oxidation with NaClO·5H2O gave S-dioxides. In addition, one of the obtained thiazole-thiophene ring-fused compounds showed some unexpected mechanochromism behavior.