Sulfur Fluoride Exchange Research Articles

Click chemistry reaches a new dimension

In 2014, K. Barry Sharpless and coworkers at Scripps Research Institute California developed sulfur fluoride exchange (SuFEx), a simple and rapid click chemistry reaction that uses sulfuryl fluoride (SO2F2) to make carbon-sulfate links. They used the technique to synthesize disulfates, polysulfate polymers, and other linear products. Suhua Li, Sharpless, and coworkers have now devised a variation that kicks SuFEx click chemistry into another dimension. Using thionyl tetrafluoride (SOF4) instead of SO2F2 as a SuFEx reagent enables them to make up to three tetrahedrally oriented connections to each sulfur hub molecule instead of two linear linkages (Angew. Chem. Int. Ed. 2017, DOI: 10.1002/anie.201611048). Thionyl tetrafluoride reacts initially with a primary amino group, forming a tetrahedral iminosulfur product with two fluoride “handles.” One fluoride or both can then react with aryl alcohols or alkyl amines to create products that are doubly or triply substituted along the sulfur hub’s tetrahedral axes. Potential applications

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

Functional polystyrenes and polyacrylamides, containing combinations of fluorosulfate, aromatic silyl ether, and azide side chains, were used as scaffolds to demonstrate the postpolymerization modification capabilities of sulfur(VI) fluoride exchange (SuFEx) and CuAAC chemistries. Fluorescent dyes bearing appropriate functional groups were sequentially attached to the backbone of the copolymers, quantitatively and selectively addressing their reactive partners. This combined SuFEx and CuAAC approach proved to be robust and versatile, allowing for a rare accomplishment: triple orthogonal functionalization of a copolymer under essentially ambient conditions without protecting groups.

Multifunctional Surface Manipulation Using Orthogonal Click Chemistry.

Polymer brushes are excellent substrates for the covalent immobilization of a wide variety of molecules due to their unique physicochemical properties and high functional group density. By using reactive microcapillary printing, poly(pentafluorophenyl acrylate) brushes with rapid kinetic rates toward aminolysis can be partially patterned with other click functionalities such as strained cyclooctyne derivatives and sulfonyl fluorides. This trireactive surface can then react locally and selectively in a one pot reaction via three orthogonal chemistries at room temperature: activated ester aminolysis, strain promoted azide-alkyne cycloaddition, and sulfur(VI) fluoride exchange, all of which are tolerant of ambient moisture and oxygen. Furthermore, we demonstrate that these reactions can also be used to create areas of morphologically distinct surface features on the nanoscale, by inducing buckling instabilities in the films and the grafting of nanoparticles. This approach is modular, and allows for the development of highly complex surface motifs patterned with different chemistry and morphology.

Combination of AGET ATRP and SuFEx for post-polymerization chain-end modifications

Post-polymerization modification of polymer chain-ends is a powerful tool for the preparation of functional materials. “Click” type reactions represent the most prevalent post-polymerization strategies. We applied the recently described sulfur(VI) fluoride exchange reaction to functionalize the chain-ends of four polymers prepared using activators generated by electron transfer atom transfer radical polymerization. Aryl-TBDMS terminated polymers were reacted with aryl sulfurofluoridate compounds with a near quantitative conversion. This research represents the application of a new click type reaction to prepare functional polymers.

SuFEx on the Surface: A Flexible Platform for Postpolymerization Modification of Polymer Brushes.

Polymer brushes present a unique architecture for tailoring surface functionalities due to their distinctive physicochemical properties. However, the polymerization chemistries used to grow brushes place limitations on the monomers that can be grown directly from the surface. Several forms of click chemistry have previously been used to modify polymer brushes by postpolymerization modification with high efficiency, however, it is usually difficult to include the unprotected moieties in the original monomer. We present the use of a new form of click chemistry known as SuFEx (sulfur(VI) fluoride exchange), which allows a silyl ether to be rapidly and quantitatively clicked to a polymer brush grown by free-radical polymerization containing native -SO2F groups with rapid pseudo-first-order rates as high as 0.04 s(-1). Furthermore, we demonstrate the use of SuFEx to facilely add a variety of other chemical functional groups to brush substrates that have highly useful and orthogonal reactivity, including alkynes, thiols, and dienes.

SuFEx on the Surface: A Flexible Platform for Postpolymerization Modification of Polymer Brushes

AbstractPolymer brushes present a unique architecture for tailoring surface functionalities due to their distinctive physicochemical properties. However, the polymerization chemistries used to grow brushes place limitations on the monomers that can be grown directly from the surface. Several forms of click chemistry have previously been used to modify polymer brushes by postpolymerization modification with high efficiency, however, it is usually difficult to include the unprotected moieties in the original monomer. We present the use of a new form of click chemistry known as SuFEx (sulfur(VI) fluoride exchange), which allows a silyl ether to be rapidly and quantitatively clicked to a polymer brush grown by free‐radical polymerization containing native ‐SO2F groups with rapid pseudo‐first‐order rates as high as 0.04 s−1. Furthermore, we demonstrate the use of SuFEx to facilely add a variety of other chemical functional groups to brush substrates that have highly useful and orthogonal reactivity, including alkynes, thiols, and dienes.