Cu/Fe/O=PPh₃-catalyzed etherification for the synthesis of aryl 3-benzo[b]thienyl ethers

Cu/Fe-cocatalyzed cross-coupling reactions between 3-bromobenzo[b]thiophene and hydroxyaryls are described herein. The combination of Cu and Fe catalysts is important for the progress of the reactions, and the use of triphenylphosphine oxide as a ligand suppresses the dehalogenation of 3-bromobenzo[b]thiophene, and promptly facilitates the reaction. The obtained aryl benzo[b]thienyl ethers can be converted to π-extended thienobenzofuran derivatives via Pd-catalyzed dehy-drogenative cyclizations.