Homologous series of regioregular alkylsubstituted oligothiophenes up to an 11-mer

A complete series of structurally well-defined butylated oligothiophenes up to an 11-mer was synthesized by a combination of aryl–aryl cross-coupling reactions and cyclization of 1,3-butadiyne precursors with sulfide anions. Palladium-catalyzed cross-coupling of halogenated thiophene units with trimethylsilylacetylene effectively yields ethynylated thiophenes which after deprotection are oxidatively coupled to the corresponding 1,3-butadiynes.