Abstract:The present review highlights recent developments in the chemistry of sulfur radicals. Background material essential to the understanding of these developments is briefly reviewed and references to previous in depth reviews are cited. The exciting applications of current research involving sulfur radicals in bonding theory, organic synthesis, polymer chemistry, materials science, and biochemistry are outlined.
“…That said, the most widely agreed pathway for conventional vulcanization is via hydrogen abstraction of the α-position relative to the double bond, leading to a combination of crosslinking by proton substitution and addition across the double bonds, with substitutions of hydrogen for sulfur being the dominant factor (Fig. 4a) 39,42,48,50 .Fig. 4Reaction schemes of vulcanizations.…”
The discovery of inverse vulcanization has allowed stable polymers to be made from elemental sulfur, an unwanted by-product of the petrochemicals industry. However, further development of both the chemistry and applications is handicapped by the restricted choice of cross-linkers and the elevated temperatures required for polymerisation. Here we report the catalysis of inverse vulcanization reactions. This catalytic method is effective for a wide range of crosslinkers reduces the required reaction temperature and reaction time, prevents harmful H2S production, increases yield, improves properties, and allows crosslinkers that would be otherwise unreactive to be used. Thus, inverse vulcanization becomes more widely applicable, efficient, eco-friendly and productive than the previous routes, not only broadening the fundamental chemistry itself, but also opening the door for the industrialization and broad application of these fascinating materials.
“…That said, the most widely agreed pathway for conventional vulcanization is via hydrogen abstraction of the α-position relative to the double bond, leading to a combination of crosslinking by proton substitution and addition across the double bonds, with substitutions of hydrogen for sulfur being the dominant factor (Fig. 4a) 39,42,48,50 .Fig. 4Reaction schemes of vulcanizations.…”
The discovery of inverse vulcanization has allowed stable polymers to be made from elemental sulfur, an unwanted by-product of the petrochemicals industry. However, further development of both the chemistry and applications is handicapped by the restricted choice of cross-linkers and the elevated temperatures required for polymerisation. Here we report the catalysis of inverse vulcanization reactions. This catalytic method is effective for a wide range of crosslinkers reduces the required reaction temperature and reaction time, prevents harmful H2S production, increases yield, improves properties, and allows crosslinkers that would be otherwise unreactive to be used. Thus, inverse vulcanization becomes more widely applicable, efficient, eco-friendly and productive than the previous routes, not only broadening the fundamental chemistry itself, but also opening the door for the industrialization and broad application of these fascinating materials.
“…They are efficient at performing atom abstractions, in particular with H-atoms, adding to π-systems and electrophiles, such as carbonyl compounds [166]. They can be generated from the UV irradiation of disulfides, sulfides or even thiols [167]. However, their use in organophotocatalysis is scarce.…”
Organic dyes have emerged as a reliable class of photoredox catalysts. Their great structural variety combined with the easy fine-tuning of their electronic properties has unlocked new possibilities for the generation of reactive intermediates. In this review, we provide an overview of the available approaches to access reactive intermediates that employ organophotocatalysis. Our contribution is not a comprehensive description of the work in the area but rather focuses on key concepts, accompanied by a few selected illustrative examples. The review is organized along the type of reactive intermediates formed in the reaction, including C(sp3) and C(sp
2
) carbon-, nitrogen-, oxygen-, and sulfur-centered radicals, open-shell charged species, and sensitized organic compounds.
“…Sulfur, as a fascinating inorganic element, also plays a strong and increasingly prominent role in organic synthesis, polymer chemistry, and modern materials science. By virtue of its versatile reactivity, sulfur appears in many different functional groups allowing to address a widespread array of chemical and physical properties . For example, the versatile reactivity of thiols originates primarily from their specific structure, namely from the presence of a highly reactive sulfur atom that adjusts its valence state and high lability of the SH bond.…”
The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/marc.201800650.
ChemistryBefore moving to the recent advances within the last 5 years in the diverse applications of sulfur chemistry in polymer and
Sulfur-Containing PolymersSulfur and its functional groups are major players in an area of exciting research taking place in modern polymer and materials science, both in academia and industry. In fact, manifold sulfur-based reactions that are both exceptionally versatile as well as tremendously useful have been implemented, and further utilized for the design and preparation of polymeric materials that lead to a plethora of applications ranging from medicine to optics and nanotechnology to separation science. Hence, within this review, an overview of strategies and developments used over the last 5 years to reinforce the importance of the sulfur functional group in modern polymer and materials science is presented. In particular, many important references in the primary literature of sulfur chemistry are referred to, including thiol-ene, thiol-yne, thiol-Michael addition, disulfide cross-linking, and thiol-disulfide exchange, among others, by explaining and illustrating the important principles. Last but not least, the grand aim to underpin the importance of sulfur in modern polymer and materials science is achieved by presenting selected examples in diverse fields and postulating the respective potential for real-world applications. he is now a full professor at KIT.sulfur atoms, and tetraphenylethene-bearing di(alkyl bromide) (Scheme 3). The yield of the polymerization was dependent on the di(alkyl bromide) monomer; the longer spacer between the aromatic moiety and the reactive bromide end groups Scheme 1. The discussion henceforth focuses on the synthesis of polymers possessing the depicted sulfur functional groups.
Scheme 2.Representative examples of polythioethers prepared via A) the nucleophilic substitution reaction between an electrophilic dihalide with nucleophilic derivatives of dithiols under alkaline conditions; B) the thiol-ene/yne addition reaction between AA and BB type monomers (i.e., dithiols and dienes/diynes); and C) radical or ionic ring-opening of sulfurcontaining strained rings.Scheme 3. The thiol-bromo polymerization of conformationally fixed monomers to provide multifunctional polymers. [19] Macromol. Rapid Commun. 2019, 40, 1800650 Scheme 4. The regioselective selective nucleophilic aromatic substitution between thiol and fluorinated aromatic compounds, the para-fluorothiol reaction (PFTR).Scheme 5. Synthesis of a linear polymer via PFTR-reaction. [21]
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