Polyarylene Synthesis by Suzuki Polycondensation of Aryl Dichlorides and an Aryl Diboronic Acid Ester

This paper describes the successful application of the Suzuki polycondensation (SPC) to the synthesis of high molecular weight polyphenylenes using aryl dichloride monomers. From readily available starting material, two meta-dichloromonomers (2b and 2c) were prepared and subjected to SPC with benzene 1,4-diboronic acid ester to produce reasonably high molar mass poly(para-meta-phenylene)s 4a and 4b, respectively, if freshly prepared Pd-catalyst, Buchwald ligand and the base K3PO4 were used. The polymer with butoxy substituent (4a) was compared regarding GPC molar mass and glass transition temperature with its exact same congener which had been synthesized in a previous work starting from a meta-dibromo monomer. This comparison unequivocally confirms the molar masses achieved and, thus, establishes the first reported case of a SPC using aryl chloride monomers, instead of the more expensive and less amply available aryl bromides which had to be used otherwise.