Polycondensation of haloarylketones catalyzed by palladium compounds bearing N-heterocyclic carbene (NHC) ligands

Palladium-catalyzed α-arylation of ketones, which can efficiently give coupling products by using appropriate ligands and bases, could be applied to a polycondensation reaction. Stable N-heterocyclic carbenes (NHC) were used as favorable ligands coordinating the Pd catalysts, which were generated in situ from commercially available palladium compounds such as Pd(OAc)2 and Pd2(dba)3 as suitable catalyst precursors in this polymerization. Using small amounts of binary catalysts, poly(aryl alkyl ketone)s were afforded in high yields from haloarylketones in the presence of a base. A primarily prepared palladium catalyst having an NHC ligand, [Pd(OAc)2(NHC)], also efficiently catalyzed the polycondensation, whereas a palladium compound bearing two carbene ligands, [PdX2(NHC)2], did not.