Iterative Extension of Thiophene Ring Leading to Head-to-Tail-Type Oligothiophenes via Stepwise CH Arylation and Halogen Exchange Sequence

Abstract

Iterative extension of the thiophene ring unit leads to oligothiophenes.The coupling reaction at the CH bond of thiophene with halo-thiophene occurs at the 5-position of 2-bromothiophene with 2-iodothiophene in the presence of a palladium catalyst and AgNO 3 /KF as an activator to give the corresponding bithiophene, whose carbon-bromine bond remains.Halogen exchange converts the bromine atom to iodide, which also allows further reaction to form thiophene-thiophene bond.Oligothiophenes are obtained by repeating such sequense.