Preparation of 4,7‐Dihalobenzo[ b ]Thiophene Derivatives Containing Iodine Atoms and Their Cross Coupling With Arylethynes

Quasi T‐shaped three‐way benzo[ b ]thiophene scaffolds, containing iodine atom(s) at the 4‐ and/or 7‐position, were prepared by several methods including silica gel‐assisted cyclization, electrophilic substitution, nucleophilic substitution, or borylation. The iodobenzo[ b ]thiophenes thus prepared were subjected to Sonogashira cross couplings to give various ethynylbenzo[ b ]thiophenes. Benzo[ b ]thiophenes bearing different ethynyl groups in the molecule were also prepared, utilizing (bromo)(iodo)benzo[ b ]thiophenes. In addition, photophysical properties as well as theoretical calculations of some 4,7‐diethynylbenzo[ b ]thiophenes were studied.