1,2-Dithiins and precursors, XVII: Synthesis and properties of thieno anellated 1,2-dithiins, structural influence on colour

Article abstract of DOI:10.1016/S0040-4020(97)00439-0

Various thieno[3,2-c] anellated (5a, 26) and dithieno[3,2-c:2,3-e] anellated 1,2-dithiins (32 a-c, 45) were obtained starting from appropriate thiophene precursors. The absorption maxima covered the range from 430 to 467 nm indicating olefinic rather than aromatic character of the anellating thiophene units. Access to the isomeric thieno[2,3-c] anellated series failed due to competing reactions in the final stage, e.g. by the formation of the 12-membered cyclic bis-disulfide 53.