Efficient and selective procedures have been developed to prepare on a medium scale several phototoxic 2, 2′: 5′, 2 ″-terthiophene derivatives of general formula 2 and 3, which are characterized by a functional substituent in the 3′-or the 5-position. Most of these procedures, which are based on the construction of the 2.2′: 5′, 2 ″-terthiophene moiety and involve palladium-mediated carbon-carbon bond forming reactions, allow to ...