SuFEx‐Based Synthesis of Polysulfates

Abstract

A handful of high fidelity reactions are at the core of industrial processes producing polymers in multimillion-ton quantities. Most commodity polymers are synthesized from olefins by forming carbon-carbon backbones, whereas engineering polymers are commonly prepared via condensation reactions of monomers often containing an activated carbonyl group or its equivalent and a suitable nucleophile, thus forming carbon-heteroatom linkages. Polyesters, polyamides, polyurethanes, and polyimides are produced in this manner. Despite the variety of backbone structures, polymers containing sulfur(VI) "-SO 2 -" connectors are virtually absent from the literature and are barely used in industrial applications (with the exception of polysulfones, in which the sulfone group is already present in the monomers [1] ).Unsurprisingly, most reported attempts to synthesize sulfur(VI)-containing polymers relied on reactions mimicking carbonyl group-based condensations, i.e. reactions of sulfonyl chlorides with nucleophiles [2] and, to a much lesser extent, Friedel-Crafts sulfonylations. [3] While polymers obtained by those methods can have attractive properties, such as good thermal and hydrolytic stability and mechanical resilience, [2c-e] the unselective reactivity of sulfur(VI) chlorides, which are susceptible to hydrolysis and participate in redox transformations and radical chlorinations, significantly limit the utility of these methods and materials.Sulfur(VI) fluorides, in particular sulfuryl fluoride (SO 2 F 2 ) and its monofluorinated derivatives, sulfonyl (RSO 2 -F) fluorides, sulfamoyl (R 2 NSO 2 -F) fluorides, and fluorosulfates (ROSO 2 -F) stand in stark contrast to other sulfur(VI) halides. These sulfur oxofluorides are much more hydrolytically stable, redox silent, and do not act as halogenating agents. Nevertheless, their selective reactivity can be revealed when an * fokin@scripps.edu Homepage: http://www.scripps.edu/fokin; sharples@scripps.edu Homepage: http://www.scripps.edu/sharpless. Supporting information for this article is available on the WWW under http://www.angewandte.org or from the authors. The formation of sulfonyl-heteroatom bonds is described in detail in an accompanying article in this issue. [5] In the early 1970s, Firth pioneered the synthesis of poly(arylsulfate) polymers from fluorosulfates of Bisphenol A (BPA), which he obtained from SO 2 F 2 , and disodium salts of the bisphenol. [6] Preparation of these monomers required prolonged heating, and pure high polymer was obtained only after repeated precipitation. Here, we report a simple and straightforward SuFEx-based method for the synthesis of high molecular weight polysulfate polymers from aryl fluorosulfates and aryl silyl ethers under simple and mild reaction conditions. HHS Public AccessReactions of silylated and fluorinated compounds are, of course, well known in organic synthesis [7] and in polymer chemistry. [8] For example, in 1983, Kricheldorf introduced the "silyl method" for the synthesis of polyaryl ethers taking advantage of the str...

Sulfur(VI) Fluoride Exchange (SuFEx): Another Good Reaction for Click Chemistry

“…In addition, the SuFEx process has proven itself reliable for polymer synthesis such as the preparation of robust poly(diarylsulfonate) thermoplastic materials. [7]…”

“…A wide variety of functional groups can be tolerated (Figure 13 B), limited only by steric bulk at silicon and the presence of acidic protons that can quench the basic catalyst. The process therefore has many characteristics of a click reaction and so is suitable for the synthesis of polymeric materials, such as the sulfate analogue [7,115] of the well-known poly(bisphenol A carbonate) (Lexan, CAS# 25037-45-2) shown in Figure 13 C. Additional iterations of this new polymerization process are described in a recent report by Dong et al [7] This conversion of aromatic silyl ethers into fluorosulfates and diarylsulfates is quite different from the popular use of silyl sulfonates (usually triflates) as catalysts in processes such as acetalization, [132] aldol, and allylation reactions. [133] In these and many other cases, silicon-oxygen bonds are swapped, or SiÀC is exchanged for SiÀO.…”

Selective and Orthogonal Post-Polymerization Modification using Sulfur(VI) Fluoride Exchange (SuFEx) and Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC) Reactions

“…In this work, we exploited the exquisite reactivity of the sulfur(VI) fluoride moiety toward aryl silyl ethers, a facet of sulfur fluoride exchange (SuFEx) chemistry that was first reported by Gembus 19 and further developed by Sharpless and our laboratories eq 1 and 2. 20,21 SuFEx was also recently exploited for the postmodification of polymer brushes on surfaces, 22 work highly related and complementary to our own herein. The SuFEx reactions, in combination with CuAAC eq 3, provide a robust and modular platform for selective modification of polymers and/or other materials.…”

Multidimensional SuFEx Click Chemistry: Sequential Sulfur(VI) Fluoride Exchange Connections of Diverse Modules Launched From An SOF4 Hub

“…[7] SuFEx reliably allows the flawless substitution of S VI ÀF with aryl silyl ethers to give S VI ÀObonds,and with amines to give S VI À Nbonds.While the mechanistic details are yet to be fully elucidated, these transactions are made possible by as pecial co-action between the hydrogen-bonding environment of fluoride ion, and the kinetic and thermodynamic properties of the bonds to sulfur(VI) and silicon centers.Key to SuFEx activation is the requirement for fluoride to transit from as trong covalent bond to al eaving group-a process mediated by tertiary amine derived catalysts [8] and thought to involve the bifluoride ion and related species. [7,[9][10][11][12][13] Early in the development of SuFEx, we identified sulfuryl fluoride (SO 2 F 2 ) [7,14] as as ulfur(VI) hub for creating diaryl sulfate links between molecules.Under SuFEx conditions,the latent reactivity of the otherwise stable S VI À Fbond is roused to react with SuFExable substrates. [7,15] While SuFEx is still an emerging technology it has already found diverse applications including,f or example:t he synthesis of tosylates [9] and sulfonyl azides; [10] application in polymer chemistry [11] and post-polymerization modification; [12,13] Suzuki coupling of aryl-and heteroaryl-fluorosulfates with boronic acids.…”

“…[7,[9][10][11][12][13] Early in the development of SuFEx, we identified sulfuryl fluoride (SO 2 F 2 ) [7,14] as as ulfur(VI) hub for creating diaryl sulfate links between molecules.Under SuFEx conditions,the latent reactivity of the otherwise stable S VI À Fbond is roused to react with SuFExable substrates. [7,15] While SuFEx is still an emerging technology it has already found diverse applications including,f or example:t he synthesis of tosylates [9] and sulfonyl azides; [10] application in polymer chemistry [11] and post-polymerization modification; [12,13] Suzuki coupling of aryl-and heteroaryl-fluorosulfates with boronic acids. [15] Of particular significance,h owever,i st he potential for SuFEx in biochemical applications: growing evidence supports the notion that proteins provide molecular and dynamic electrostatic field environments that sulfur(VI) fluoride linkages are adept at reading,and reacting to.…”