Synthesis of 5,5′-diarylated 2,2′-bithiophenes via palladium-catalyzed arylation reactions

2,2′-Bithiophene and 3,3′-dicyano-2,2′-bithiophenes are diarylated directly with aryl bromides at the 5- and 5′-positions accompanied by C–H bond cleavage in the presence of Pd(OAc)2 and a bulky phosphine ligand using Cs2CO3 as base. In the reaction using (2,2′-bithiophen-5-yl)diphenylmethanol as the substrate, monoarylation at the 5-position via C–C bond cleavage occurs selectively to give 5-aryl-2,2′-bithiophenes and the subsequent arylation with a different aryl bromide affords the corresponding unsymmetrically 5,5′-diarylated products.