A visible-light-initiated energy-transfer enabled radical cyclization for the divergent synthesis of polycyclic γ-sultine derivatives has been developed. The reaction provides an alternative and expeditious access to benzofused γ-sultine frameworks, the analogues of γ-lactones and γ-sultones, and features good functional group compatibility, mild reaction conditions and excellent diastereoselectivity. The robustness and application potential of this method have also been successfully displayed by two gram-scale reactions and the synthesis of polycyclic sultones. Mechanistic studies indicated the transformations through a possible energy-transfer enabled intramolecular radical homolytic substitution or hydrogen atom transfer process mainly.

Sulfonyl groups are widely observed in biologically relevant molecules and consequently, SO2 capture is an increasingly attractive method to prepare these sulfonyl-containing compounds given the range of SO2 -surrogates now available as alternatives to using the neat gas. This, along with the advent of photoredox catalysis, has enabled mild radical capture of SO2 to emerge as an effective route to sulfonyl compounds. Here we report a photoredox-catalyzed cross-electrophile sulfonylation of aryl and alkyl bromides making use of a previously under-used amine-SO2 surrogate; bis(piperidine) sulfur dioxide (PIPSO). A broad selection of alkyl and aryl bromides were photocatalytically converted to their corresponding sulfinates and then trapped with various electrophiles in a one-pot multistep procedure to prepare sulfones and sulfonamides.

This review disclosed synthetic approaches to sulfonyl amides from non-sulfonyl halogenated precursors. Known methods were systematized into groups and subgroups according to the type of starting organosulfur compound. Thiols, disulfides, and sulfonamides form a group of S(II)-containing precursors, which are used in oxidative amination reactions. An important and versatile group for oxidative amination is represented with S(IV)-containing compounds, i. e., sufinates, sulfinamides, DMSO, N-sulfinyl-O-(tert-butyl)hydroxylamine, etc. A series of S(VI)-containing precursors for amination reactions (except sulfonyl halides) include sulfonic acids, sulfonyl azides, thiosulfonates, and sulfones. All approaches are represented with the most prominent examples of the resulting sulfonamides, which could be obtained in high yields mostly via short reaction sequences. Promising electrochemical methods for the preparation of sulfonamides from thiols, disulfides, sulfonamides, sulfinic acid derivatives, and dimethyl sulfoxide under mild and green conditions are also highlighted.

The intermediate oxidation state of sulfoxides is central to the plethora of their applications in chemistry and medicine, yet it presents challenges for an efficient synthetic access, limiting the structural diversity of currently available sulfoxides. Here, we report a data-guided development of direct decarboxylative sulfinylation that enables the previously inaccessible functional group interconversion of carboxylic acids to sulfoxides in a reaction with sulfinates. Given the broad availability of carboxylic acids and the growing synthetic potential of sulfinates, the direct decarboxylative sulfinylation is poised to improve the structural diversity of synthetically accessible sulfoxides. The reaction is facilitated by a kinetically favored sulfoxide formation from the intermediate sulfinyl sulfones, despite the strong thermodynamic preference for the sulfone formation, unveiling the previously unknown and chemoselective radicalophilic sulfinyl sulfone reactivity.

Conjugated dienes and polyenes are central structural motifs of natural products, and key synthetic intermediates in organic synthesis and materials science. We describe herein a palladium-catalyzed dienylation of aryl, heteroaryl, and vinyl triflates, nonaflates and iodides that were previously identified as recalcitrant substrates for the sulfolene-mediated catalytic dienylation. The method has now been successfully expanded to C-O and C-I dienylation, demonstrating broad scope with respect to sulfonates, iodides and sulfolenes. The reactions proceed with high regio- and stereoselectivity, and efficiency that are strongly influenced by basic additives, whose influence on the reaction performance was systematically studied.

The aim of our study is to develop amine-free photoinitiating systems (PISs) for the polymerization of representative dental methacrylate resins under blue light irradiation. PISs based on camphorquinone (CQ)/sulfinate and CQ/sulfonate, eventually in combination with an iodonium salt, are proposed and compared to the well-established CQ/amine system. The polymerization performances of thick (1.4 mm) samples of different methacrylate blends upon exposure to a commercial blue LED centered at 477 nm under air are described. Finally, the performances of the new developed PISs are evaluated for dental composites application.
FTIR is used to monitor the photopolymerization profiles. ESR spectroscopy and electrochemical experiments are used to identify the radicals generated. Mechanical properties measurements and color stability measurements are carried out to determine the key properties of the dental composites prepared.
The performances of the new proposed PISs for the photopolymerization of thick (1.4 mm) samples of methacrylate upon exposure to a blue dental LED under air are excellent. Similar or better performances and bleaching properties are obtained with the new proposed amine-free systems compared to those reached with the CQ/amine reference system. Dental composites with excellent mechanical properties and exceptional color stability are obtained. The involved chemical mechanisms for the initiation step were also established.

An alternative method for forming sulfonates through hypervalent iodine(III) reagent-mediated oxidation of sodium sulfinates has been developed. This transformation involves trapping reactive sulfonium species using alcohols. With additional optimization of the reaction conditions, the method appears extendable to other nucleophiles such as electron-rich aromatic systems or cyclic ethers through a ring opening pathway.

Considerable strides have been made in understanding the oxidative mechanisms involved in the final steps of the cysteine pathway leading to taurine. The oxidation of sulfinates, hypotaurine and cysteine sulfinic acid, to the respective sulfonates, taurine and cysteic acid, has never been associated with any specific enzyme. Conversely, there is strong evidence that in vivo formation of taurine and cysteic acid is the result of sulfinate interaction with a variety of biologically relevant oxidants. In the last decade, many experiments have been performed to understand whether peroxynitrite, nitrogen dioxide and carbonate radical anion could be included in the biologically relevant reactive species capable of oxidizing sulfinates. Thanks to this work, it has been possible to highlight two possible reaction mechanisms (direct and indirect reaction) of sulfinates with reactive oxygen and nitrogen species.The sulfinates oxidation, mediated by peroxynitrite, is an example of both reaction mechanisms: through a two-electron-direct-reaction with peroxynitrite or through a one-electron-indirect-transfer reaction. In the indirect mechanism, the peroxynitrite homolysis releases hydroxyl and nitrogen dioxide radical and in addition the degradation of short-lived adduct formed by peroxynitrite and CO2 can generate carbonate radical anion. The reaction of hypotaurine and cysteine sulfinic acid with peroxynitrite-derived radicals is accompanied by extensive oxygen uptake with the generation of transient intermediates, which can begin a reaction by an oxygen-dependent mechanism with the sulfonates, taurine, and cysteic acid as final products. Due to pulse radiolysis studies, it has been shown that transient sulfonyl radicals (RSO2•) have been produced during the oxidation of both sulfinates by one-electron transfer reaction.The purpose is to analyze all the aspects of the reactive mechanism in the sulfinic group oxidation of hypotaurine and cysteine sulfinic acid through the results obtained from our laboratory in recent years.

Copper-zinc superoxide dismutase (SOD) is considered one of the most important mammalian antioxidant defenses and plays a relevant role due to its main function in catalyzing the dismutation of superoxide anion to oxygen and hydrogen peroxide. However, interaction between SOD and H2O2 produced a strong copper-bound oxidant (Cu(II)•OH) that seems able to contrast the self-inactivation of the enzyme or oxidize other molecules through its peroxidase activity. The bicarbonate presence enhances the peroxidase activity and produces the carbonate anion radical (CO3•-). CO3•- is a freely diffusible reactive species capable of oxidizing several molecules that are unwieldy to access into the reactive site of the enzyme. Cu(II)•OH oxidizes bicarbonate to the CO3•-, which spreads out of the binding site and oxidizes hypotaurine and cysteine sulfinic acid to the respective sulfonates through an efficient reaction. These findings suggest a defense role for sulfinates against the damage caused by CO3•- . The effect of hypotaurine and cysteine sulfinic acid on the CO3•--mediated oxidation of the peroxidase probe ABTS to ABTS cation radical (ABTS•+) has been studied. Both sulfinates are able to inhibit the oxidation of ABTS mediated by CO3•-. The effect of hypotaurine and cysteine sulfinic acid against SOD inactivation by H2O2 (~42% protection of enzyme activity) has also been investigated. Interestingly, hypotaurine and cysteine sulfinic acid partially avoid the H2O2-mediated SOD inactivation, suggesting that the two sulfinates may have access to the SOD reactive site and preserve it by reacting with the copper-bound oxidant. In this way hypotaurine and cysteine sulfinic acid not only intercept CO3•- which could move out from the reactive site and cause oxidative damage, but also prevents the inactivation of SOD.

Alkyl sulfinates function as formal nucleophiles in Mannich-type reactions to give sulfonyl formamides, which are readily dehydrated to the corresponding sulfonylmethyl isonitriles. The efficient, two-step synthesis provides a general route to sulfonylmethyl isonitriles from readily available methyl sulfinates or thiols. Mechanistic analysis reveals that the unusual nucleophlicity of the alkyl sulfinates arises from the in situ release of sulfinic acids.