Synthesis of β-Methoxy, Methyl-Capped α-Oligothiophenes

Article abstract of DOI:10.1021/jo00126a034

The first syntheses of structurally defined methoxyoligothiophenes are described.Nine α-coupled oligothiophenes, dimers through hexamers, symmetrically substituted at the "inside" or "outside" β-positions with two or four methoxy groups, and with terminal methyl groups, were prepared.The electron-donor methoxy groups and terminal methyls have been shown to stabilize cationic species formed by oxidation or protonation of these oligomers.The oligomers were built up by the cross coupling of (mono- or oligo-) β-methoxy-α-iodothiophenes and (mono- or oligo-) α-stannylthiophenes catalyzed by Pd(0)/Pd(II) or by the redox homo-coupling of α-thienyllithium compounds with Fe(acac)3.Synthesis by the cross coupling of thienyl Grignard reagents and bromothiophenes with Ni(0) or Suzuki coupling using organoboranes was not successful.An X-ray crystal structure od a dimethoxy quaterthiophene is reported.