Synthesis of Polymers Having Exomethylene Groups via Palladium(0)-Catalyzed Cross-Coupling Polymerization of Propargylic Carbonates with Various Nucleophiles

Abstract

Palladium-catalyzed reactions via π-allylpalladium intermediates are one of the most powerful methods for the synthesis of various compounds. Among such reactions, the cross-coupling reaction of propargylic carbonates with substrates having two nucleophilic sites is one of the effective synthetic methods for various cyclic compounds. In spite of its success in organic synthesis, the palladium-catalyzed cross-coupling polymerization using propargylic carbonates had not been investigated. Propargylic carbonates undergo two consecutive reactions with nucleophiles under palladium catalysis. Therefore, we have focused on the propargylic carbonates as monomers for the palladium-catalyzed cross-coupling polymerization. In this review, we describe a comprehensible overview of our recent studies using propargylic carbonates. The polymerizations of propargylic carbonates with bifunctional nucleophiles afforded various polymers with exomethylene groups in the main chains. In addition, cross-conjugated polymers composed of 2,3-butadiene and arenes were successfully synthesized by palladium-catalyzed cross-coupling polymerization of bis(propargylic carbonate)s with aromatic diboronic acids. Furthermore, such interesting exomethylene structure is suitable for post-functionalization and-transformation. The 2,3-butadiene structure of cross-conjugated polymers could easily be converted into vinylene structure of linear-conjugated polymers through Diels-Alder reaction.