Synthesis of 3,4′-Diaryl- and 4,4′-Diaryl-2,2′-bithienyls from 2,5-Dichlorothiophene

Abstract 3,4′-Diaryl-, and 4,4′-diaryl-2,2′-bithienyls, new classes of mixed thiophene–arene oligomers, were synthesized from 2,5-dichlorothiophene via 4-aryl-2-chlorothiophene in three and two steps, respectively. Namely, a Friedel–Crafts type self-condensation of 4-aryl-2-chlorothiophene, followed by catalytic dechlorination, yielded unsymmetrical bithienyls. Homocoupling of 4-aryl-2-chlorothiophene using a nickel–phosphine catalyst gave symmetrical bithienyls.