Palladium-Catalyzed Syntheses of Polyethynyl-Substituted 2,2′-Bithiophenes

The syntheses of polyethynyl‐substituted 2,2′‐bithiophenes 2 and related 5,5′‐dicarbaldehyde derivatives 1 are described. The treatment of easily available polybrominated 2,2′‐bithiophenes 3 and 2,2′‐bithiophene‐5,5′‐dicarbaldehydes 4 with phenyl or (trimethylsilyl)acetylene in the presence of PdII and CuI in (i‐Pr)2NH yields substituted polyethynyl‐2,2′‐bithiophene compounds. The Me3Si protecting groups can be removed by protodesilylation under basic conditions to give the corresponding terminal ethynyl groups. These polyethynyl‐bithiophenes could be interesting precursors for the synthesis of macrocycles with interesting properties.