Highly Efficient Catalysts for Direct Arylation Polymerization (DArP)

Recently, the palladium-catalyzed direct arylation polymerization (DArP) has emerged as a viable alternative to conventional synthetic means of making pi-conjugated polymers based on catalytic cross-coupling reactions. The DArP, which proceeds through C-H bond activation, has a distinct advantage over cross-coupling polymerization in terms of fewer reaction steps and higher functional group tolerance. We have developed novel catalysts for DArP by using P(2-MeOC6H4)(3) (L1) and P(2-Me2NC6H4)(3) (L2) as ligands. Although common direct arylation catalysts require the use of strongly coordinating solvents such as DMA and DMF, our catalysts exhibit high activity in THF and toluene, which are good solvents for pi-conjugated polymers. Thus, we could realize the precise synthesis of highly head-to-tail regioregular poly(3-hexylthiophene) (HT-P3HT) and donor-acceptor type alternating copolymers (DA polymers) with well-controlled structures through DArP.