Synthesis of cyclic polymers containing various backbones by means of non-stoichiometric Suzuki-Miyaura polycondensation through intramolecular catalyst transfer

Cyclic polymers bearing various backbones are selectively synthesized by means of non-stoichiometric Suzuki-Miyaura polycondensation of 1.0 equivalent of diboronate monomers containing carbon-carbon double bond (C=C), ester, ether, and carbonate linkages with 1.3 equivalents of meta- or para-dibromophenylene in the presence of t-Bu3PPd G2 precatalyst and CsF/18-crown-6 as a base. The molecular weight of the cyclic polymers increases with increasing monomer concentration. The obtained polymer containing C=C is cyclic even in the high-molecular-weight region, as confirmed by end-group analysis after degradative cross-metathesis reaction of the obtained polymer with an excess of an olefinic small molecule. This non-stoichiometric A2 + B2 Suzuki-Miyaura polycondensation is expected to be a powerful tool for the synthesis of cyclic polymers containing various functional groups in the backbone.

Automated summary

Cyclic polymers with different backbones were selectively synthesized using a non-stoichiometric Suzuki-Miyaura polycondensation reaction. This reaction involved the use of 1.0 equivalent of diboronate monomers containing carbon-carbon double bond (C=C), ester, ether, and carbonate linkages with 1.3 equivalents of meta- or para-dibromophenylene, in the presence of t-Bu3PPd G2 precatalyst and CsF/18-crown-6 as a base. The obtained cyclic polymers showed an increase in molecular weight with increasing monomer concentration. The presence of C=C bonds in the polymer was confirmed even at high molecular weights through end-group analysis after a degradative cross-metathesis reaction.