Norbornenyl-based RAFT agents for the preparation of functional polymers via thiol-ene chemistry

A synthetic platform for the preparation of various norbornenyl (Nb) containing reversible addition–fragmentation chain transfer (RAFT) agents has been developed. The design of the chain transfer agents (CTAs) is based on the desymmetrization of α,α′-dibromo-p-xylene by monosubstitution with an alkoxide anion and subsequent replacement of the residual bromine atom in the benzylic bromide to create several series of RAFT CTA including trithiocarbonate, xanthate and dithiobenzoate CTAs, allowing for the possibility to introduce other functional groups besides Nb, such as an allyl group. While a norbornene functionality was chosen as most reactive functional group toward thiols in radical-mediated thiol–ene chemistry, an allyl group was introduced for the sake of direct comparison of the double bond reactivity in the thiol–ene reaction. Control of the radical polymerization of acrylates, styrene and vinyl acetate has been achieved by using this novel family of CTAs. The results indicate that the Nb group rem...