Direct C–H Methylsulfonylation of Alkenes with the Insertion of Sulfur Dioxide

Photoinduced Alkylsulfonylation and Cyanoalkylsulfonylation of Morita-Baylis-Hillman Adducts via Multicomponent Insertion of Sulfur Dioxide

General and convenient visible-light-promoted alkylsulfonylation and cyanoalkylsulfonylation of MBH adducts have been developed through the multicomponent insertion of sulfur dioxide, enabling the assembly of two C-S bonds to generate structurally diverse allylic alkylsulfones (43 examples in total). The reaction of MBH adducts with potassium alkyltrifluoroborates and 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct afforded sulfones with generally good yields. Notably, the addition of N,N,N',N'-tetramethylethylenediamine as a base into the photocatalytic system led to yielding an alkyl sulfonyl unit and cyano group-anchored trisubstituted alkenes by utilizing cycloketone oxime esters as C-radical precursors. Both of these reactions have constructed two C-S bonds, and all desired products were obtained in moderate to excellent yields with complete stereospecificity.

Palladium-Catalyzed Three-Component Dearomatization/Sulfonylation Cascade

The diastereoselective synthesis of sulfonylated indolines is reported. A palladium-catalyzed dearomative sulfination of (aza)indole-tethered aryl iodides generates reactive benzylic sulfinates. These intermediates react with electrophiles in a one-pot, two-step process to generate sulfonylated products in good yields and excellent diastereoselectivity. This three-component sequence demonstrates good scalability and can be applied toward the synthesis of sulfonamides. Additionally, further derivatizations of aryl iodide containing products furnish spiro- and alkynylated indoline products.

Photoredox-Catalyzed α-Sulfonylation of Ketones from Sulfur Dioxide and Thianthrenium Salts

A photoredox-catalyzed sulfonylation of silyl enol ethers with DABCO·(SO₂)₂ and thianthrenium salts is achieved, providing diverse β-keto sulfones in moderate to good yields. This protocol features easily accessible starting materials and good functional group compatibility, enabling the introduction of various functionalized sulfonyl groups into ketones. Furthermore, as one of the important industrial raw materials, methanol can be employed as the methyl source to prepare α-methylsulfonated ketones through a methyl thianthrenium intermediate for the first time.

Metal-free synthesis of sulfonylated indolo[2,1-a]isoquinolines from sulfur dioxide

Access to sulfonylated indolo[2,1-a]isoquinolines through an efficient three-component reaction of 2-aryl-N-acryloyl indoles, sulfur dioxide and aryldiazonium tetrafluoroborates is developed. This transformation is performed under metal-free and mild conditions by using...

Construction of sulfonated spiro[5,5]trienones from sulfur dioxide via iron-catalyzed dearomative spirocyclization of biaryls

An iron-catalyzed dearomative spirocyclization of biaryl ynones with sodium metabisulfite and cycloketone oxime esters is developed. By using sodium metabisulfite as the source of sulfur dioxide, this approach enables the...

A photocatalytic radical relay reaction of 2-methylthiolated phenylalkynones and potassium metabisulfite

The generation of methylsufonyl-containing thioflavones through a radical relay reaction of methylthiolated phenylalkynones and potassium metabisulfite in the presence of sodium methylsulfinate under visible light irradiation is developed.

Synthesis of β-cyanoalkylsulfonylated vinyl selenides through a four-component reaction

A mild copper-catalyzed four-component selenosulfonylation of alkynes, cycloketone oxime esters, DABCO (SO₂)₂ and diselenides has been developed. This method enables the rapid assembly of β-cyanoalkylsulfonylated vinyl selenides in moderate to good yields. Advantages of this protocol include a broad substrate scope, good functional group tolerance and the late-stage functionalization of complex molecules. Moreover, the potential utility of this methodology is demonstrated through simple oxidation of the products to access synthetically important alkynyl sulfones. Mechanistic studies suggest that a cyanoalkylsulfonyl radical intermediate is involved in this process.

Generation of Heteroaryl-Substituted Sulfonyl Compounds from Sulfur Dioxide via Remote Heteroaryl ipso-Migration

The generation of heteroaryl-substituted sulfonyl compounds via a catalyst-, base-, and additive-free three-component reaction of heteroaryl-substituted tertiary alcohols, aryldiazonium tetrafluoroborates, and DABCO·(SO₂)₂ under mild conditions is developed. Various functional groups are tolerated well in this transformation, and a broad substrate scope is demonstrated. A preliminary mechanistic investigation shows that this reaction undergoes a radical process, including the insertion of sulfur dioxide, sulfonyl radical addition to unactivated alkene, and remote heteroaryl ipso-migration.

Photoinduced efficient synthesis of cyanoalkylsulfonylated oxindoles via sulfur dioxide insertion

A visible-light-promoted radical cascade reaction of N-arylacrylamide and cyclobutanone oxime esters with sulfur dioxide insertion is established. Mainly through the exploration of the visible light wavelength, it is found that the light source has a certain influence on the formation of cyanoalkylsulfonylated oxindoles, furnishing a range of sulfones in good to excellent yields. This protocol presents good functional group compatibility and does not require transition metals, photosensitizers, external bases, or oxidants.

Copper-Catalyzed Regioselective 1,4-Selenosulfonylation of 1,3-Enynes to Access Cyanoalkylsulfonylated Allenes

By employing CuOAc as the catalyst, we realize a four-component reaction of 1,3-enynes, diselenides, DABCO·(SO₂)₂, and cycloketone oxime esters, providing facile access to diverse cyanoalkylsulfonylated allenyl selenides in moderate to good yields. This reaction features high functional group tolerance and a broad substrate scope, enabling the regioselective, sequential formation of C-SO₂ and C-Se bonds under mild reaction conditions. Moreover, the utility of this methodology is further illustrated through the late-stage functionalization of drug-based molecules.

Metal-catalyzed C-S bond formation using sulfur surrogates

Sulfur-containing compounds are present in a wide range of biologically important natural products, drugs, catalysts, and ligands and they have wide applications in material chemistry. Transition metal-catalyzed C-S bond-forming reactions have successfully overcome the obstacles associated with traditional organosulfur compound syntheses such as stoichiometric use of metal-catalysts, catalyst-poisoning and harsh reaction conditions. One of the key demands in metal-catalyzed C-S bond-forming reactions is the use of an appropriate sulfur source due to its odor and availability. The unpleasant odor of many organic sulfur sources might be one of the reasons for the metal-catalyzed C-S bond-forming reactions being less explored compared to other metal-catalyzed C-heteroatom bond-forming reactions. Hence, employing an appropriate sulfur surrogate in the synthesis of organosulfur compounds in metal-catalyzed reactions is still of prime interest for chemists. This review explores the recent advances in C-S bond formation using transition metal-catalyzed cross-coupling reactions and C-H bond functionalization using diverse and commercially available sulfur surrogates. Based on the different transition metal-catalysts, this review has been divided into three major classes namely (1) palladium-catalyzed C-S bond formation, (2) copper-catalyzed C-S bond formation, and (3) other metal-catalyzed C-S bond formation. This review is further arranged based on the different sulfur surrogates. Also, this review provides an insight into the growing opportunities in the construction of complex organosulfur scaffolds covering natural product synthesis and functional materials.

Deaminative metal-free reaction of alkenylboronic acids, sodium metabisulfite and Katritzky salts

A convenient and efficient approach to (E)-alkylsulfonyl olefins via a metal/light-free three-component reaction of alkenylboronic acids, sodium metabisulfite and Katritzky salts is described. This alkylsulfonylation proceeds smoothly with a broad substrate scope, leading to diverse (E)-alkylsulfonyl olefins in moderate to good yields. During the process, excellent functional group tolerance is observed and sodium metabisulfite is used as the source of sulfur dioxide. Mechanistic studies show that the alkyl radical generated in situ from Katritzky salt via a single electron transfer with alkenylboronic acid or DIPEA is the key step for providing an alkyl radical intermediate, which undergoes further alkylsulfonylation with sulfur dioxide.

The Same Oxidation-State Introduction of Hypervalent Sulfur via Transition-Metal Catalysis

Sulfonyl compounds have attracted considerable interest due to their extensive applications in drug discovery, agricultural, and material science. The access to the assembly of SO₂ -containing compounds via the same oxidative-state introduction of hypervalent sulfur has come to the fore in the recent years. Especially, the transition-metal-involved synthesis of hypervalent sulfur compounds is the most effective strategy since SO₂ is easy to insert into the metal-carbon bonds. This review discusses the application of the same oxidation-state introduction of hypervalent sulfur strategy under the transition-metal-catalyzed conditions, and presents according to different metal catalysts and the synthesized diversity hypervalent sulfur-containing compounds skeletons, including sulfonamides, sulfones, sulfinamides, sulfonyl acids and sulfonyl fluorides.

Visible-light-induced remote C(sp3)–H sulfonylvinylation: assembly of cyanoalkylated vinyl sulfones

A photoinduced three-component sulfonylvinylation reaction of propargyl alcohols, potassium metabisulfite and cycloketone oxime esters is developed, affording cyanoalkylated vinyl sulfones in moderate to good yields.

Photoinduced intramolecular carbosulfonylation of alkynes: access to sulfone-containing dibenzazepines from sulfur dioxide

A visible-light-driven three-component carbosulfonylation of terminal alkynes, DABCO (SO₂)₂ and aryldiazonium tetrafluoroborates is developed, leading to sulfone-containing dibenzazepines in moderate to good yields under mild conditions.

Generation of (E)-β-sulfonyl enamines from sulfur dioxide via a radical process

An iron(ii)-catalyzed three-component reaction of O-acyl oximes, sulfur dioxide, and N-vinylacetamides is accomplished. Diverse (E)-β-sulfonyl enamines are obtained in moderate to good yields by using this protocol with excellent stereoselectivity and regioselectivity.

Synergistic photoredox and tertiary amine catalysis: generation of allylic sulfones from Morita–Baylis–Hillman acetates and sulfur dioxide

The first example of the synthesis of allylic sulfones through synergistic photoredox and tertiary amine catalysis, starting from MBH acetates, DABCO·(SO₂)₂ and 4-substituted Hantzsch esters or potassium alkyltrifluoroborates via a radical pathway, is reported.

A multi-component reaction of electron-rich arenes, potassium metabisulfite, aldehydes and aryldiazonium tetrafluoroborates

A multi-component reaction of electron-rich arenes, potassium metabisulfite, aldehydes and aryldiazonium tetrafluoroborates under mild conditions is reported, leading to a range of (arylsulfonyl)methylbenzenes in moderate to good yields.

A visible-light photoredox-catalyzed four-component reaction for the construction of sulfone-containing quinoxalin-2(1H)-ones

A visible-light photoredox-catalyzed four component reaction of quinoxalin-2(1H)-ones, alkenes, aryldiazonium, and sodium metabisulfite leading to sulfone-containing quinoxalin-2(1H)-ones has been developed.

Copper-catalyzed regio- and chemoselective selenosulfonylation of 1,6-enynes from sulfur dioxide

An efficient copper-catalyzed multicomponent reaction of 1,6-enynes, diselenides, DABCO·(SO2)2, and cycloketone oxime esters was achieved, providing cyanoalkylsulfonated pyrrolidines in moderate to good yields.

Copper(II)-Catalyzed Domino Synthesis of 4-Benzenesulfonyl Isoxazoles from 2-Nitro-1,3-enynes, Amines, and Sodium Benzenesulfinate

A simple and effective method for the synthesis of fully substituted 4-benzenesulfonyl isoxazoles through a copper(II)-catalyzed three-component reaction of 2-nitro-1,3-enynes, amines, and sodium benzenesulfinate is described. The reaction proceeds smoothly under mild conditions and provides the benzenesulfonyl isoxazoles with high chemoselectivity.

A metal-free reaction of sulfur dioxide, cyclopropanols and electron-deficient olefins

The importance of γ-keto sulfones in medicinal chemistry and organic synthesis is known. An efficient route to γ-keto sulfones via a metal-free reaction of cyclopropanols, sulfur dioxide and electron-deficient olefins is achieved. This reaction proceeds smoothly under mild conditions without the need of catalyst, oxidant or additive. A plausible mechanism is proposed, which occurs through a γ-keto sulfinate intermediate generated in situ from the reaction of cyclopropanol with sulfur dioxide. The γ-keto sulfinate intermediate would be trapped by the electron-deficient olefin, resulting in the formation of γ-keto sulfones. Various functional groups in the cyclopropanols and electron-deficient olefins are compatible in this transformation.

Recent advances in sulfonylation reactions using potassium/sodium metabisulfite

Recently, sulfonylation reactions using potassium/sodium metabisulfite as the sulfur dioxide surrogate have been developed rapidly. In most cases, the transformations go through radical processes with the insertion of sulfur dioxide under mild conditions. Additionally, transition metal catalysis is applied in the reactions for the synthesis of sulfonyl-containing compounds. Among the approaches, photoinduced conversions under visible light or ultraviolet irradiation are also involved. In this updated report, the insertion of sulfur dioxide from potassium metabisulfite or sodium metabisulfite is summarized.

Metal-free insertion of sulfur dioxide with aryl iodides under ultraviolet irradiation: direct access to sulfonated cyclic compounds

Metal-free insertion of sulfur dioxide with aryl iodides and silyl enolates or allylic bromide under ultraviolet irradiation at room temperature is accomplished. This protocol provides a convenient route to sulfonated cyclic compounds under mild conditions.

Photoredox-catalyzed sulfonylation of difluoroenoxysilanes with the insertion of sulfur dioxide

A photoredox-catalyzed three-component reaction of aryldiazonium tetrafluoroborates with sodium metabisulfite and 2,2-difluoro enol silyl ethers is described, providing α,α-difluoro-β-ketosulfones in moderate to good yields under mild conditions.

A copper-catalyzed insertion of sulfur dioxide via radical coupling

A copper-catalyzed reaction of O-acyl oximes, DABCO·(SO₂)₂, and 2H-azirines is developed under mild conditions, leading to diverse tetrasubstituted β-sulfonyl N-unprotected enamines with excellent stereoselectivity and regioselectivity.

Recent advances in the direct β-C(sp2)–H functionalization of enamides

Recent advances in the direct β-C(sp²)–H functionalization of enamides, mainly including arylation, alkenylation, alkynylation, alkylation, acylation, sulfonylation, phosphorylation, and others, are reported.

Photoinduced synthesis of alkylalkynyl sulfones through a reaction of potassium alkyltrifluoroborates, sulfur dioxide, and alkynyl bromides

A photoinduced reaction of potassium alkyltrifluoroborates, sodium metabisulfite, and alkynyl bromides under visible light irradiation at room temperature is developed.

Photoinduced synthesis of 2-sulfonylacetonitriles with the insertion of sulfur dioxide under ultraviolet irradiation

Metal-free insertion of sulfur dioxide with aryl iodides and 3-azido-2-methylbut-3-en-2-ol under ultraviolet irradiation at room temperature is achieved, giving rise to 2-(arylsulfonyl)acetonitriles in moderate to good yields. Alkyl iodide is also workable under these conditions. This transformation proceeds smoothly under mild conditions with a broad substrate scope. Various functional groups are compatible including amino, ester, halo, and trifluoromethyl groups. No metal catalyst or additive is needed during the reaction process. Mechanistic studies show that under ultraviolet irradiation, an aryl radical is generated in situ from aryl iodide, which undergoes subsequent sulfonylation via the insertion of sulfur dioxide leading to arylsulfonyl radical intermediates. Then the arylsulfonyl radical reacts with 3-azido-2-methylbut-3-en-2-ol giving rise to the corresponding 2-(arylsulfonyl)acetonitrile.

Copper-catalyzed synthesis of sulfonamides from nitroarenes via the insertion of sulfur dioxide

A three-component reaction of arylboronic acids, nitroarenes, and potassium metabisulfite under copper catalysis proceeds smoothly, giving rise to a range of sulfonamides in good to excellent yields with broad substrate scope.

Generation of (Z)-β-alkenyl alkylsulfones via a copper-catalyzed decarboxylative alkylsulfonylation

A copper-catalyzed three-component reaction of acrylamides, sulfur dioxide and phenyliodine(iii) dicarboxylates is developed. The conversion using phenyliodine dicarboxylates as alkyl radical precursors provides diverse (Z)-β-alkenyl alkylsulfones.