An Unexpected Reaction of Arenesulfonyl Cyanides with Allylic Alcohols: Preparation of Trisubstituted Allyl Sulfones

Synthesis of Diverse Allylic Sulfone Derivatives via Sequential Hydroalkoxylation of 1,3-Enynes

A first metal-free protocol for the synthesis of allylic sulfones featuring aldehyde functionality at the δ-position has been reported. The formation of structurally complex δ,δ-dimethoxy allylic sulfones is enabled by the direct nucleophilic attack of methoxide onto the sulfone-containing 1,3-enynes. The present approach allows facile installation of acetal groups within the allylic sulfone scaffold, providing versatile platforms for further functionalization and drug development.

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.

One-Pot, Metal-Free Synthesis of Allyl Sulfones in Water

A one-pot dehydration cross-coupling reaction between allyl alcohols and sodium sulfinates that provides allyl sulfones in good to excellent yields is presented. Its broad substrate scope includes symmetrical and asymmetrical α,α-diaryl- and α-aryl-substituted allylic alcohols and aryl and alkyl sodium sulfinates. For asymmetrical allylic substrates, the E isomer predominates with examples of excellent stereoselectivity. Control experiments provide the basis for a proposed radical-mediated mechanism. The metal-free procedure applies cheap and commercially available tetrabutylammonium tribromide as the catalyst and H2O as the solvent. Notable features of this simple, efficient, weakly toxic, and environmentally benign strategy include mild and convenient operating conditions and readily accessible starting materials.

Photo-induced radical transformations of tosyl cyanide

Tosyl cyanide is a commonly used reagent for cyanation and sulfonylation in organic synthesis and pharmaceutical chemistry. The photocatalytic transformations of tosyl cyanide are generally conducted under mild conditions. This minireview summarizes the recent progress of radical-involved transformations of tosyl cyanide via photo-induced cyanation or sulfonylcyanation.

Sulfination of Unactivated Allylic Alcohols via Sulfinate-Sulfone Rearrangement

A dehydrative cross-coupling of unactivated allylic alcohols with sulfinic acids was achieved under catalyst-free conditions. This reaction proceeded via allyl sulfination and concomitant allyl sulfinate-sulfone rearrangement. Various allylic sulfones could be obtained in good to excellent yields with water as the only byproduct. This study expands the synthetic toolbox for constructing allylic sulfone molecules.

Organophotoredox-Catalyzed Arylation and Aryl Sulfonylation of Morita-Baylis-Hillman Acetates with Diaryliodonium Reagents

We report an organophotoredox-catalyzed stereoselective allylic arylation of MBH acetates with a palette of diaryliodonium triflates (DAIRs) to provide the corresponding trisubstituted alkenes in moderate to good yields. The method could be extended to three-component coupling involving 1,4-diazabicyclo[2.2.2]octane bis(sulfur dioxide) adduct (DABSO) as a sulfur dioxide surrogate for the synthesis of biologically relevant allylic sulfones. Both of these reactions were carried out under mild conditions featuring broad scope, robustness, and appreciable functional group tolerance.

Visible-Light-Induced, Palladium-Mediated Desaturation/Sulfonation Cascade To Access 4-Sulfonyltetrahydropyridine Scaffolds

Herein, we report a visible-light-induced, palladium-catalyzed desaturation/sulfonation cascade, offering a concise route to a series of highly valuable 4-sulfonyltetrahydropyridine scaffolds from inexpensive and readily available piperidine derivatives with sodium sulfinates. The key to the success of this transformation is the well-designed sequence of palladium-mediated 1,5-hydrogen atom transfer/β-hydride elimination/allylic sulfonation process, which demonstrates the synthetic potentials for orchestrating synthetic events by rationally taking advantage of varied catalytic modes.

Chemodivergent Synthesis of Sulfonamide and Sulfones from N-Tosylhydrazones by Switching Catalyst and Temperature

A catalyst- and temperature-controlled selective synthesis of sulfonamide and sulfones from N-tosylhydrazones and MBH carbonates has been developed. The use of palladium catalysts exclusively leads to sulfonamide products at room temperature, whereas the selective synthesis of sulfones is dominant for a temperature-controlled coupling reaction without palladium catalysis. Importantly, the catalyst- or temperature-controlled reaction exhibits high nucleophilicity rather than carbene reactivity in these transformations.

Visible-light-driven reactions for the synthesis of sulfur dioxide-inserted compounds: generation of S-F, S-O, and S-N bonds

Sulfur dioxide-containing compounds such as sulfonyl fluorides, sulfonyl esters, and sulfonyl amides are important structural frameworks in many natural products, pharmaceuticals, and organic compounds. Thus, synthesis of these molecules is a very valuable research topic in organic chemistry. Various synthetic methods to introduce SO₂ groups into the structure of organic compounds have been developed for the synthesis of biologically and pharmaceutically useful compounds. Recently, visible-light-driven reactions were carried out to create SO₂-X (X = F, O, N) bonds, and their effective synthetic approaches were demonstrated. In this review, we summarized recent advances in visible-light-mediated synthetic strategies for generation of SO₂-X (X = F, O, N) bonds for various synthetic applications along with proposed reaction mechanisms.

Dehydroxylative Sulfonylation of Alcohols

Described here is the R₃P/ICH₂CH₂I-promoted dehydroxylative sulfonylation of alcohols with a variety of sulfinates. In contrast to previous dehydroxylative sulfonylation methods, which are usually limited to active alcohols, such as benzyl, allyl, and propargyl alcohols, our protocol can be extended to both active and inactive alcohols (alkyl alcohols). Various sulfonyl groups can be incorporated, such as CF₃SO₂ and HCF₂SO₂, which are fluorinated groups of interest in pharmaceutical chemistry and the installation of which has received increasing attention. Notably, all reagents are cheap and widely available, and moderate to high yields were obtained within 15 min of reaction time.

Water-mediated radical C-H tosylation of alkenes with tosyl cyanide

The water-mediated tosylation of alkenes with tosyl cyanide was discovered. Experimental investigations revealed that the reaction was initiated by the in situ formation of sulfinyl sulfone in the presence of water. The sulfinyl sulfone species decomposed to a sulfonyl radical and a sulfinyl radical through homolytic fission. The vinyl sulfone was afforded via sequential addition of the alkene to the sulfonyl radical and the sulfinyl radical, followed by β-elimination of a sulfinyl moiety.

1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP)-Assisted Catalyst-Free Sulfonation of Allylic Alcohols with Sulfinyl Amides

A highly regioselective and catalyst-free sulfonation of allylic alcohols with sulfinyl amides has been realized. Such a mix-and-go procedure provides a convenient approach to synthetically various allylic sulfones under mild reaction conditions. Furthermore, this novel reaction shows ample substrate scope and outstanding functional group tolerance and could also be scaled-up. Meanwhile, it is the first example that sulfinyl amides act as a powerful sulfur nucleophile in the reactions. 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP) as a solvent plays a critical role in allylic sulfonation.

Nickel-Catalyzed Reductive Thiolation of Unactivated Alkyl Bromides and Arenesulfonyl Cyanides

The cross-electrophile coupling between unactivated alkyl bromides with arenesulfonyl cyanides catalyzed by Ni(acac)₂ under reductive conditions to form unsymmetrical sulfides is developed. This approach for sulfide synthesis is practical, relies on available, unfunctionalized materials such as alkyl (pseudo)halides, and is scalable. This catalytic strategy provides a complementary method for the preparation of unsymmetrical alkyl-aryl sulfides under mild conditions with good functional group tolerance.

An iodine-mediated new avenue to sulfonylation employing N-hydroxy aryl sulfonamide as a sulfonylating agent

A novel and highly efficient I2/K2CO3 mediated regioselective sulfonylation of thiophenols, aryl acetylenic acid and aromatic alkynes with N-hydroxy sulfonamide has been developed. N-hydroxy sulfonamide has been used for the first time for the synthesis of these sulfones. The scope and versatility of the reaction has been demonstrated by the regio- and stereoselective synthesis of different analogs of sulfones with various structural features.

An efficient approach for the synthesis of novel methyl sulfones in acetic acid medium and evaluation of antimicrobial activity

A series of nine methyl sulphones ( 3a –3 i ) starting from the aldehydes ( 1a–1i ) were synthesized in two consecutive steps. In the first step, preparation of allyl alcohols ( 2a–2i ) from their corresponding aldehydes by the reaction of sodium borohydride in methanol at room temperature is reported. Finally, methyl sulphones are synthesized by condensing sodium methyl sulfinates with allyl alcohols in the presence of BF ₃ .Et ₂ O in acetic acid medium at room temperature for about 2–3 h. The reaction conditions are simple, yields are high (85%–95%), and the products were obtained with good purity. All the synthesized compounds were characterized by their ¹ H, ¹³ C NMR, and mass spectral analysis. All the title compounds were screened for antimicrobial activity. Among the compounds tested, the compound 3f has inhibited both Gram positive and Gram negative bacteria effectively and compound 3i has shown potent antifungal activity. These promising components may help to develop more potent drugs in the near future for the treatment of bacterial and fungal infections.

Visible-light-induced sulfonylation of Baylis–Hillman acetates under metal- and oxidant-free conditions

A visible-light-driven metal- and oxidant-free procedure for the sulfonylation of Baylis–Hillman acetates with sulfonyl hydrazides under open-air conditions at room temperature is reported. The methods provide a green and facile synthetic route to access allylic sulfones.

Palladium nanoparticles as efficient catalyst for C-S bond formation reactions

The development of green, economical and sustainable chemical processes is one of the primary challenges in organic synthesis. Herein, we report an efficient and heterogeneous palladium-catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates via decarboxylative cross-coupling. Both aliphatic and aromatic sulfinate salts react with various vinyl cyclic carbonates to deliver the desired allylic sulfones featuring tri- and even tetrasubstituted olefin scaffolds in high yields with excellent selectivity. The process needs only 2 mol% of Pd2(dba)3 and the in situ formed palladium nano-particles are found to be the active catalyst.

Regio- and Enantioselective Preparation of Chiral Allylic Sulfones Featuring Elusive Quaternary Stereocenters

We describe here the first general asymmetric synthesis of sterically encumbered α,α-disubstituted allylic sulfones via Pd-catalyzed allylic substitution. The design and application of a new and highly efficient phosphoramidite ligand (L10) proved to be crucial, and a wide variety of challenging allylic sulfones featuring quaternary stereocenters could be obtained in good yields and with good to excellent levels of regio- and enantioselectivities under attractive process conditions. The developed methodology employs easily accessible chemical feedstock including racemic allylic precursors and sodium sulfinates. The utility of the method is further demonstrated by the synthesis of the sesquiterpene (-)-Agelasidine A.

Photoinduced synthesis of allylic sulfones using potassium metabisulfite as the source of sulfur dioxide

Synthesis of allylic sulfones through a photoinduced three-component reaction of aryl/alkyl halides, potassium metabisulfite, and allylic bromides under ultraviolet irradiation at room temperature is developed. Diverse allylic sulfones are generated in moderate to good yields.

Water-promoted C-S bond formation reactions

Allylic sulfones, owning to their widespread distributions in biologically active molecules, received increasing attention in the past few years. However, the synthetic method under mild conditions is still a challenging task. In this paper, we report a sulfinic acids ligation with allylic alcohols via metal-free dehydrative cross-coupling. Both aliphatic and aromatic sulfinic acids react with various allylic alcohols to deliver the desired allylic sulfones in high yields with excellent selectivity. This carbon-sulfur bond formation reaction is highly efficient and practical since it works under metal-free, neutral, aqueous media and at room temperature in which the products even can be obtained by simple filtration without the need for organic extraction or column chromatography. Water is found to be essential for the success of this carbon-sulfur bond formation reaction. DFT calculations imply that water acts as promoter in this transformation via intermolecular hydrogen bonds.

Rhodium-catalyzed addition of sulfonyl hydrazides to allenes: regioselective synthesis of branched allylic sulfones

A rhodium-catalyzed regioselective addition of sulfonyl hydrazides to allenes is reported. With Rh(i)/DPEphos/benzoic acid as the catalyst system, branched allylic sulfones can be obtained, in good to excellent yields and regioselectivities.

tert-Butyl nitrite-mediated vicinal sulfoximation of alkenes with sulfinic acids: a highly efficient approach toward α-sulfonyl ketoximes

A novel vicinal sulfoximation of alkenes was achieved under mild and metal-free conditions by using readily available sulfinic acids as the sulfonating agent and tert-butyl nitrite (TBN) as the radical initiator and the oxime source.

Iodine-catalyzed Sulfonylation of Arylacetylenic Acids and Arylacetylenes with Sodium Sulfinates: Synthesis of Arylacetylenic Sulfones

A highly efficient and generally applicable iodine-catalyzed reaction of arylacetylenic acids and arylacetylenes with sodium sulfinates for the synthesis of arylacetylenic sulfones was developed. The methodology has the advantages of a metal-free strategy, easy to handle reagents, functional group tolerance, a wide range of arylacetylenic acids and arylacetylenes, and easy access to arylacetylenic sulfones.

Synthesis of Unsymmetrical Sulfides and Their Oxidation to Sulfones to Discover Potent Antileishmanial Agents

Unsymmetrical sulfides were first synthesized using combinations of a 1,3-dicarbonyl, an aromatic aldehyde and a thiol in the presence of 10 mol % ethanolic piperidine. These sulfides derivatives were subsequently converted into corresponding sulfones via oxidation in the presence of m-chloroperoxybenzoic acid (m-CPBA) at ice-bath to room temperature. The former reaction was achieved at room temperature through one-pot three-component. The later was obtained in good yields using mild reaction conditions with flexibility in choice from a range of substrates. The antimicrobial properties of the newly synthesized sulfone derivatives were investigated against the protozoan parasite, Leishmania donovani, a causative agent of visceral leishmaniasis (VL). Nine sulfone derivatives were found to be efficacious and exhibited significant antimicrobial activity. Further, these compounds were nontoxic on murine peritoneal macrophages thus eliminating potential cytoxicity in the host cells. These compounds may be indicated as potential leads in the treatment of visceral leishmaniasis.

One-Pot Synthesis of Allylic Sulfones, Ketosulfones, and Triflyl Allylic Alcohols from Domino Reactions of Allylic Alcohols with Sulfinic Acid under Metal-Free Conditions

A metal-free tandem procedure by using a sulfonylation reaction of aryl allylic alcohols followed by an iodobenzenediacetate (PIDA)-promoted oxidative functionalization has been established. Allylic sulfones, γ-ketosulfones, and triflyl allylic alcohols have been constructed in a single operation. The methodology incorporates the sulfonyl (both aryl and triflyl) functionality with a simple work-up procedure.

A facile and mild synthesis of trisubstituted allylic sulfones from Morita-Baylis-Hillman carbonates

An efficient and catalyst-free synthesis of trisubstituted allylic sulfones through an allylic sulfonylation reaction of Morita-Baylis-Hillman (MBH) carbonates with sodium sulfinates has been developed. Under the optimized reaction conditions, a series of trisubstituted allylic sulfones were rapidly prepared in good to excellent yields (71%–99%) with good to high selectivity (Z/E from 79:21 to >99:1). Compared with known synthetic methods, the current protocol features mild reaction temperature, high efficiency and easily available reagents.

Iron-catalyzed direct difunctionalization of alkenes with dioxygen and sulfinic acids: a highly efficient and green approach to β-ketosulfones

A novel and efficient iron-catalyzed direct difunctionalization of alkenes with sulfinic acids and dioxygen for the synthesis of β-ketosulfones has been developed.