Palladium-catalyzed synthesis of oligo(methylthio) aniline and conversion to polyacene-type electrolytes bearing phenothiazinium repeating units

The synthetic routes to ladder polymers which consist of benzenetetrayl subunits with imino and methyl-sulfonio linkages are described. As the key intermediate, oligo- and polyaniline derivatives having pendant methylthio groups are prepared by the Pd-catalyzed aryl amination from various monomers. The Oxidation of the polymers with H₂O₂ in the presence of CH₃COOH effects the high yielding conversion of methylthio to methylsulfinyl groups without the formation of the undesired methylsulfonyl groups. The superacid-induced condensation of the resulting polymers under dilution conditions induced the polymer-analogous intramolecular electrophilic ring closure reaction of the hydroxy(methyl)(phenyl)sulfonium cation onto the adjacent benzene ring to yield the required ladder polymers which have proved to be semiconductors with intrinsic electric conductivities of ca. 10^-5 S · cm^-1.