Efficient Heterodifunctional Unimolecular Ring‐Closure Method for Cyclic Polymers by Combining RAFT and SuFEx Click Reactions

Abstract

A novel ring‐closure strategy for cyclic polymers by combining reversible addition–fragmentation chain transfer polymerization (RAFT) and the sulfur(VI)‐fluoride exchange (SuFEx) click reaction is presented. Herein, a new heterodifunctional trithiocarbonate RAFT agent, 2‐((tert‐butyldimethylsilyl)oxy)ethyl (4‐(fluorosulfonyl)benzyl) carbonotrithioate (TBDMS‐FSBCT), containing both tert‐butyldimethylsilyl ether and sulfonyl fluoride moieties, is developed. The polymerization behavior of TBDMS‐FSBCT is first demonstrated by a standard RAFT polymerization procedure for two types of vinyl monomers, N‐isopropylacrylamide (NIPAAm) (conjugated vinyl monomer) and N‐vinylpyrrolidone (NVP) (unconjugated vinyl monomer). The tert‐butyldimethylsilyl ether and sulfonyl fluoride groups at the α and ω positions of the obtained linear polymer precursors (L‐PNIPAAm and L‐PVP) are verified by 1H, 13C, and 19F NMR spectra. Subsequent intramolecular SuFEx click cyclization of the α,ω‐heterofunctionalized linear precursors in air at room temperature conveniently yields the corresponding cyclic polymers (C‐PNIPAAm and C‐PVP). Overall, this is the first report on the preparation of cyclic polymers based on the SuFEx reaction under ambient conditions. It is envisioned that the approach may open an avenue for the formation of cyclic polymers.

SuFEx-enabled, chemoselective synthesis of triflates, triflamides and triflimidates

“…In the framework of Sulfur( vi )–Fluoride Exchange (SuFEx) chemistry—an umbrella term for substitution events replacing fluoride at the electrophilic sulfur center—these ‘ molecular plugins ’ allow selective and efficient installation of linkages around the S VI core. Especially in the last seven years, various research groups have demonstrated the potential of SuFEx hubs such as sulfonyl fluorides (R–SO 2 F), 1 sulfuryl fluoride (SO 2 F 2 ), 2 thionyl tetrafluoride (SOF 4 ), 3 ethenesulfonyl fluoride (ESF, CH 2 CH–SO 2 F), 2 a ,4 and others. 5 The chemoselective and straightforward nature of SuFEx chemistry has enabled a range of applications in synthesis and materials.…”

Preparation of α,ω‐heterobifunctionalized poly(N‐vinylpyrrolidone) via a bis‐clickable RAFT reagent

“…9,10 Among these polymerization techniques, the RAFT process is particularly suitable for the preparation of terminal functional polymers due to its compatibility with a broader range of monomers and reaction media. For example, terminal functional polymers with linear, 11 star, 12 brush, 13 ring, 14 and other molecular architectures have been synthesized through the design of RAFT reagent structures. 2,3 Since the concept of click chemistry was first proposed by Sharpless et al in 2001, 15 it has been widely developed due to its characteristics of high efficiency and robust, rapid, and specific reactions.…”

Click chemistry strategies for the accelerated synthesis of functional macromolecules

“…The TBS and fluorosulfonyl end groups were stable during RAFT polymerization of Nisopropylacrylamide (NIPAAm) and N-vinylpyrrolidone (NVP), and intramolecular SuFEx cyclization performed under ambient condition in high yield. 352…”