Copper(I)-Catalyzed Nitrosylation/Annulation Cascade of Enaminones with tert-Butyl Nitrite: Access to 1H-1,2,3-Triazole 2-Oxides

The direct synthesis of triazole 2-oxides has posed a challenge in the field of N-heterocyclic chemistry. A novel copper(I)-catalyzed nitrosylation/annulation cascade of enaminones provides a straightforward route to 1H-1,2,3-triazole 2-oxides by forming new C-N, N=N, and N-N bonds using noncorrosive tert-butyl nitrite (TBN) as both the N and NO sources. The synthetic protocol features easily accessible starting materials, wide substrate scopes, and good tolerance toward various functional groups while avoiding use of explosive azides.

Electrochemical oxygenation of sulfides with molecular oxygen or water: switchable preparation of sulfoxides and sulfones

A practical and eco-friendly method for the controllable aerobic oxygenation of sulfides by electrochemical catalysis was developed. The switchable preparation of sulfoxides and sulfones was effectively controlled by reaction time, in which both molecular oxygen and water can be used as the oxygen source under catalyst and external oxidant-free conditions. The electrochemical protocol features a broad substrate scope and excellent site selectivity and is successfully applied to the modification of some sulfide-containing pharmaceuticals and their derivatives.

Dual Photoredox/Nickel-Catalyzed 1,4-Sulfonylarylation of 1,3-Enynes with Sulfinate Salts and Aryl Halides: Entry into Tetrasubstituted Allenes

A radical-mediated three-component 1,4-sulfonylarylation of 1,3-enynes with aryl iodides and sulfinate salts using cooperative photoredox/nickel catalysis is described. This protocol enables the synthesis of tetrasubstituted sulfonyl-containing allenes under redox-neutral conditions and provides a versatile 1,3-enyne 1,4-difunctionalization platform for the synthesis of a diverse range of tetrasubstituted allenes with high chemo- and regioselectivities, excellent functional group tolerance, and a broad substrate scope.

Design, synthesis and biological activity of bis-sulfonyl-BODIPY probes for tumor cell imaging

In recent years, BODIPY derivatives have become one of the research hotspots in the field of bioprobes, but most of them have the problems of poor hydrophilicity, low biocompatibility and no targeting. In this paper, novel ethylenediamine bridging bis-sulfonyl-BODIPY fluorescent probes were successfully designed and synthesized to solve these problems; What's more, the cytotoxicity analysis, cell imaging, in vivo imaging and apoptosis experiments were carried out. Ethylenediamine bridges and oxygen-rich sulfonyl groups made such probes had certain hydrophilicity, so they could be dissolved in dimethylsulfoxide and methanol. The IC₅₀ value of compound 9 in HCT-116 cells was 93.12 ± 6.33 µM, and in HeLa cells was 89.09 ± 11.84 µM, which indicating that the probe had certain inhibitory effect on cancer cells. The excellent biocompatibility and potential tumor targeting properties of the compound were clearly observed in cell and mice imaging. This study is of great significance for the rational design of novel targeted BODIPY probes with good hydrophilicity and biocompatibility.

Practical Electro-Oxidative Sulfonylation of Phenols with Sodium Arenesulfinates Generating Arylsulfonate Esters

A practical and sustainable synthesis of arylsulfonate esters has been developed through electro-oxidation. This reaction employed the stable and readily available phenols and sodium arenesulfinates as the starting materials and took place under mild reaction conditions without additional oxidants. A wide range of arylsulfonate esters including those bearing functional groups were produced in good to excellent yields. This reaction could also be conducted at a gram scale without a decrease of reaction efficiency. Those results well demonstrated the potential synthetic value of this reaction in organic synthesis.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Visible Light-Induced Radical Addition/Annulation to Construct Phenylsulfonyl-Functionalized Dihydrobenzofurans Involving an Intramolecular 1,5-Hydrogen Atom Transfer Process

A visible light-induced radical cascade reaction of 2-alkynylarylethers with sodium sulfinates was established for the synthesis of sulfonyl-functionalized dihydrobenzofurans, and an intramolecular 1,5-hydrogen atom transfer was involved in this transformation. This process provided an efficient and convenient C-C formation protocol for the construction of a dihydrobenzofuran ring. Various substituents on 2-alkynylarylethers and sodium sulfinates were tolerated in the reaction, and the corresponding products were obtained in moderate to good yields.

Benzotetramisole catalyzed kinetic resolution of 2H-azirines

An unprecedented benzotetramisole (BTM)-catalyzed kinetic resolution for the efficient synthesis of chiral 2H-azirines is described. This protocol provides two chiral isomers in one step with broad scope, good yield and high enantioselectivity. In addition, the optically pure 2H-azirine products have proven to be useful building blocks for further synthetic transformations.

Visible-light photoredox-catalyzed dual C–C bond cleavage: synthesis of 2-cyanoalkylsulfonylated 3,4-dihydronaphthalenes through the insertion of sulfur dioxide

A novel visible-light photoredox-catalyzed dual C–C bond cleavage of methylenecyclopropanes and cycloketone oximes for accessing 2-cyanoalkylsulfonated 3,4-dihydronaphthalenes is established.

Direct sulfonylation of BODIPY dyes with sodium sulfinates through oxidative radical hydrogen substitution at the α-position

A series of α-sulfonated BODIPYs were efficiently synthesized from sodium sulfinates via a radical process, and were demonstrated as new fluorescent probes for selective biothiol detection.

A three-component approach to isoxazolines and isoxazoles under metal-free conditions

A 1,3-dipolar cycloaddition of 2-methylquinoline, tert-butyl nitrite (TBN) and alkynes or alkenes for the synthesis of biheteroaryls containing both isoxazoline/isoxazole and quinoline motifs has been developed. In this protocol, TBN serves as a convenient N-O source to convert 2-methylquinoline into intermediate nitrile oxides in situ.

Dual Roles of tert-Butyl Nitrite in the Transition Metal- and External Oxidant-Free Trifluoromethyloximation of Alkenes

By employing tert-butyl nitrite as both nitrogen source and oxidant, the trifluoromethyloximation of alkenes proceeds smoothly in a free-radical process. The developed difunctionalization reaction enables practical and efficient synthesis of a wide range of α-CF₃ ketoximes in moderate yields with excellent regioselectivity. This method features the use of readily available and stable alkenes as substrates and inexpensive CF₃ SO₂ Na as a CF₃ reagent, no involvement of transition metals or external oxidant, and room-temperature conditions. Moreover, a scale-up of the reaction, further transformation of the products into various valuable CF₃ -containing compounds, and removal of the trifluoromethyl group are readily achieved.

Electrochemical Alkoxysulfonylation Difunctionalization of Styrene Derivatives Using Sodium Sulfinates as Sulfonyl Sources

An eco-friendly method for the synthesis of β-alkoxy sulfones via electrochemical alkoxysulfonylation reaction of styrenes with sodium sulfinates as sulfonyl sources has been established. The reaction is conducted in an undivided cell at room temperature and tolerates a wide scope of styrenes, sodium sulfinates, and alcohols. The reaction does not need any chemical oxidants and transition-metal catalysts, which provides a new and green access to β-alkoxy sulfones.

Synthesis of α-trifluoromethyl ethanone oximes via the three-component reaction of aryl-substituted ethylenes, tert-butyl nitrite, and the Langlois reagent

A three-component reaction of aryl-substituted ethylenes, tert-butyl nitrite, and the Langlois reagent to synthesize a-trifluoromethyl ethanone oximes was developed.

Visible-light-induced cascade sulfonylation/cyclization of N-propargylindoles with aryldiazonium tetrafluoroborates via the insertion of sulfur dioxide

A simple and efficient visible-light-catalyzed cascade sulfonylation/cyclization of N-propargylindoles with K₂S₂O₅ and aryldiazonium tetrafluoroborates for the construction of 2-sulfonyl-substituted 9H-pyrrolo[1,2-a]indoles is developed.

Visible-light promoted one-pot synthesis of sulfonated spiro[4,5]trienones from propiolamides, anilines and sulfur dioxide under transition metal-free conditions

A novel visible-light promoted sulfonylation/ipso-cyclization of N-arylpropiolamides with aromatic amines and DABCO·(SO₂)₂ to synthesize various sulfonated spiro[4,5]trienones is reported.