The synthetic routes to ladder polymers that consist of benzenetetrayl subunits with oxo
and methylsulfonio linkages are described. As the key intermediate, poly(phenylene oxide)s having pendant
methylsulfenyl groups are prepared by copper-catalyzed oxidative polymerization of the corresponding
phenols with O2. The oxidation of the polymer with an equimolar amount of H2O2 in the presence of
acetic acid effects the high-yielding conversion of methylsulfenyl to methylsulfinyl groups without the
formation of the undesired methylsulfonyl groups. The superacidified condensation of the resulting polymer
(Swern reaction of aryl sulfoxides) under dilution conditions induces the polymer-analogous intramolecular
electrophilic ring-closing reaction of the hydroxymethylphenylsulfonium cation onto the adjacent benzene
ring to yield the required ladder polymer, which has proved to be a semiconductor with an intrinsic electric
conductivity of 2 × 10-5 S/cm. A comparison of the spectroscopic properties of the ladder polymer with
those of the model compounds such as 5-methylphenoxathiinium triflate and phenoxathiin discloses
π-electron delocalization over the methylsulfonio linkages, demonstrating the efficacy of the ladderization
for p−π/d−π interactions in arylsulfonium moieties. This synthetic approach permits the thio and
alkylsulfonio ladder linkages for a variety of phenyl ethers to form in high yields.
The synthetic routes to ladder polymers which consist of benzenetetrayl subunits with imino and methylsulfonio 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.
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