Evolving organic synthesis fostered by the pluripotent phenylsulfone moiety

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.

Pd-Catalyzed Picolinamide-Directed C(sp2)-H Sulfonylation of Amino Acids/Peptides with Sodium Sulfinates

This report describes a Pd-catalyzed picolinamide-directed site-selective C(sp2)-H sulfonylation of amino acids and peptides with sodium sulfinates in moderate to good yields. Sulfonylation of levodopa and dopamine drug molecules and late-stage directed peptide sulfonylation are studied for the first time. Broad substrate scope having various functionalities, late-stage drug modifications, and various post synthetic utilities such as chalcogenation, bromination, olefination, and arylation are potential advantages.

Catalyst-Free α-trans-Selective Hydroboration and (E)-Selective Deuterated Semihydrogenation of Alkynyl Sulfones

Here, we present a straightforward α-trans-selective hydroboration of alkynyl sulfones with NHC-boranes without the need for a catalyst. This reaction is compatible with a wide range of substrates for efficiently producing structurally diverse α-borylated vinyl sulfones in satisfactory yields. The hydride transfer from NHC-borane 2a to alkynyl triflone 1b is studied by density functional theory (DFT) calculations for trans-hydroboration. Moreover, a regiodivergent deuterated semihydrogenation of alkynyl triflones has also been developed using D2O as the deuterium source. A variety of diversity-oriented D-containing vinyl triflones were prepared in good to excellent yields with excellent deuterium incorporation ratios. Synthetic manipulations of the deuterated products are achieved for the conversion into valuable deuterated molecules, indicating the utility of this protocol.

A Single Terminal [NiII-OH] Catalyst for Direct Julia-Type Olefination and α-Alkylation Involving Sulfones and Alcohols

A terminal [NiII-OH] complex 1, supported by triflamide-functionalized NHC ligands, showed divergent reactivity for the reaction of sulfone with alcohol, contingent on base concentration, temperature, and time. Julia-type olefination of alcohols with sulfones was achieved using one equiv. of base, whereas lowering base loading to 0.5 equiv. afforded α-alkylated sulfones. Besides excellent substrate scope and selectivity, biologically active stilbene derivatives DMU-212, pinosylvin, resveratrol, and piceatannol were synthesized in high yield under Julia-type olefination conditions. An extensive array of controlled experiments and DFT calculations provide valuable insight on the reaction pathway.

Umpolung-Enabled Divergent Dearomative Carbonylations

Although dearomative functionalizations enable the direct conversion of flat aromatics into precious three-dimensional architectures, the case for simple arenes remains largely underdeveloped owing to the high aromatic stabilization energy. We herein report a dearomative sequential addition of two nucleophiles to arene π-bonds through umpolung of chromium-arene complexes. This mode enables divergent dearomative carbonylation reactions of benzene derivatives by tolerating various nucleophiles in combination with alcohols or amines under CO-gas-free conditions, thus providing modular access to functionalized esters or amides. The tunable synthesis of 1,3- or 1,4-cyclohexadienes as well as the construction of carbon quaternary centers further highlight the versatility of this dearomatization. Diverse late-stage modifications and derivatizations towards synthetically challenging and bioactive molecules reveal the synthetic utility. A possible mechanism was proposed based on control experiments and intermediate tracking.

Electrochemical Oxidative Sulfonylation-Azidation of Alkenes

A novel electrochemical oxidative sulfonylation-azidation of alkenes is accomplished by using sulfonyl hydrazide and trimethylsilyl azide (TMSN3) for the one-pot and green synthesis of β-azidoarylsulfone, which involves the direct construction of new C-S and C-N bonds. Notably, neither exogenous oxidants/additives nor metal catalysts are required for this method. In addition, this electrochemical strategy features mild conditions and wide substrate scope and has been proved to be a radical pathway by mechanistic studies.

A formal vinylic substitution reaction for the synthesis of α,β-unsaturated enol esters and their anticancer potential

Arylsulfonyl group-bearing α,β-unsaturated enol esters were readily assembled via the Cs2CO3-mediated union of 2-bromoallyl sulfones and cinnamic acids. The overall transformation is equivalent to an sp2 carbon-oxygen coupling reaction, and therefore constitutes a formal vinylic substitution. Several of the products display promising levels of antiproliferative activities higher than that of the anticancer drug carboplatin. Thiophenol reacted with 2-bromoallyl sulfones under identical conditions to afford α-thiophenyl-α'-tosyl acetone via an apparent aerial oxidation.

Visible-Light Induced Radical Addition-Elimination Reaction for Constructing Allylic Sulfones from Sulfonyl Chlorides and Allyl Bromides

Allyl sulfones are commonly present in bioactive compounds and organic building blocks. This work introduces a photocatalytic radical addition-elimination reaction involving readily accessible sulfonyl chlorides and allyl bromides. It delivers structurally diverse allylic sulfones in moderate to excellent yields, showcasing a high tolerance to functional groups. Notably, this method operates under mild reaction conditions without the need for oxidants, stoichiometric reducing metals, or additives.

Organophotocatalyzed Alkyl/Arylsulfonylation of Vinylcyclopropanes

Allyl sulfones are an essential pharmacophore in many bioactive compounds. To combat their synthetic barrier, we report a practical, straightforward organophotocatalyzed methodology for accessing miscellaneously functionalized allyl sulfone derivatives using inexpensive and bench-stable sodium sulfinate salts under mild conditions. This photo-catalyzed radical sulfonylation provides access to a variety of allyl sulfones in good to excellent yields with high E : Z selectivity. A wide range of vinyl cyclopropanes, as well as aryl/hetero and alkyl sodium sulfinates, were tolerated and reliable in gram-scale synthesis. Later on, further functionalization of allyl sulfones was demonstrated. A plausible mechanism for radical sulfonylation is proposed from the control experiments.

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.

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.

Copper-Catalyzed Diastereoselective Borylative Allylation of Alkenyl Sulfones and Base-Controlled Synthesis of Skipped Dienes

Divergent functionalization of α,β-unsaturated sulfones under copper catalysis is reported. Diastereoselective borylative allylation of alkenyl sulfones was achieved with a copper catalyst, allyl phosphate, bis(pinacolato)diboron, and LiOMe. In this method, the addition of a copper-boryl complex to alkenyl sulfone and subsequent allylic substitution rendered boroallylated products in good yield with excellent syn-diastereoselectivity. In contrast, a stronger base (KOt-Bu) promoted the reaction further toward the formation of (E)-skipped dienes, through elimination of the sulfonyl and boryl groups.

A Redox-neutral Nickel-catalysed Sulfonylation of (Hetero)aryl Boronic Acids with 2-Chlorothiazoles

A redox-neutral nickel-catalysed sulfonylation for arylsulfone synthesis was developed. (Hetero)aryl boronic acids reacted with potassium metabisulfite (K2 S2 O5 ) and readily available 2-chlorothiazoles in the presence of air-stable Ni(OTf)2 and 4,4-di-tert-butyl bipyridine (dtbpy) as a commercially available ligand to produce the corresponding 2-sulfonylthiazoles in moderate to excellent yields. This practical protocol tolerates a wide range of substrates including boronic acids and 2-chloro(benzo)thiazoles without additional bases, allowing the direct synthesis of functional arylsulfones.

Reagentless Chemistry "On-Water": An Atom-Efficient and "Green" Route to Cyclic and Acyclic β-Amino Sulfones via aza-Michael Addition Using Microwave Irradiation

A reagentless, catalyst-free, and sustainable methodology was developed for facile access to cyclic and acyclic β-amino sulfones "on-water" using a microwave. A variety of aromatic and aliphatic amines undergo double aza-Michael addition on the surface of the water with water-insoluble divinyl sulfones upon microwave irradiation at 150 °C for 10 min to mostly afford solid cyclic β-amino sulfones as easily separable products in excellent yields by simple filtration avoiding any workup steps. Thus, all atoms of the substrates are reflected in the product making it a 100% atom-efficient method. Both electron-rich and electron-deficient amines participated well in the reaction as well as good functional group tolerance was observed. The competitive experiments expectedly revealed faster reaction kinetics for electron-rich amines. The methodology was extended to acyclic β-amino sulfones by interacting phenyl/ethyl vinyl sulfones with various amines in a similar manner. Expectedly, the method afforded very low environmental factors (in a range of 0.05-0.5) and a high Ecoscale score (up to 94). In an attempt toward sustainable development, this reagent-free, metal-free, organic solvent-free, cost-effective protocol is certainly a viable alternative to the available methods for β-amino sulfones.

Recent Advances of S-18F Radiochemistry for Positron Emission Tomography

The click chemistry of sulfur(VI) fluoride exchange (SuFEx) has facilitated the widespread application of sulfur-fluoride compounds such as sulfonyl fluorides, fluorosulfates, and sulfamoyl fluorides in various fields, especially in the development of 18F ligands for PET (positron emission tomography) imaging. In recent years, the prominent progress of sulfur-[18F]fluoride compounds has been achieved through the combination of 18F and sulfur-fluoride chemistry. These compounds serve as potential 18F tracers, 18F synthons, and reagents for 18F-fluorination, thereby complementing the range of 18F ligands, typically C-18F structures, used in PET studies. This review aims to provide an overview of S-18F labeling reactions through examples of relevant 18F compounds and highlight the advancements and breakthroughs achieved in the past decade.

Rh-Catalyzed Asymmetric Hydrogenation of α-Substituted Alkenyl Sulfones: Highly Chemo- and Enantioselective Access to Chiral Sulfones

Rh-(R,R)-f-spiroPhos complex-catalyzed asymmetric hydrogenation of α-substituted alkenyl sulfones has been achieved, affording the chiral γ-keto sulfones and simple α-alkyl-substituted sulfones in high yields (96-99%) with excellent chemo-/enantioselectivities (86-96% ee) and high turnover numbers (TONs) of up to 4000. The method provides an efficient and high-enantioselectivity strategy for chiral γ-keto sulfones and simple α-substituted sulfones under mild conditions. Moreover, the obtained hydrogenation product was transformed into other important chiral α-substituted sulfones.

Rhodium-Catalyzed Regio- and Enantioselective Allylic Sulfonylation from Sulfonyl Hydrazides

A highly regio- and enantioselective allylic sulfonylation has been developed with rhodium and bisoxazolinephosphine (NPN*) ligands from racemic branched allylic carbonates and readily available sulfonyl hydrazides under neutral conditions. Branch-selective allylic sulfones with a >20:1 branch:linear ratio and >99% ee could be synthesized in ≤96% yield. Both Z and E linear allylic carbonates could also be converted into the same chiral branched allylic sulfones with high regio- and enantioselectivities.

Electrochemical C-H Sulfonylation of Hydrazones

We have developed an electrochemical method for the direct C-H sulfonylation of aldehyde hydrazones using sodium sufinates as the sulfonylating agent under supporting electrolyte-free conditions. This straightforward sulfonylation strategy afforded a library of (E)-sufonylated hydrazones with high tolerance of various functional groups. The radical pathway of this reaction has been revealed by the mechanistic studies.

Photo/Ni dual-catalyzed radical defluorinative sulfonylation to synthesize gem-difluoro allylsulfones

Radical defluorinative functionalization of α-trifluoromethyl styrenes represents an effective way toward gem-difluoroalkenes. There are general interests in developing novel synthetic protocols for defluorinative functionalization with various types of radicals. However, reports on the preparation of gem-difluoro allylsulfones via an S-centered radical pathway are limited. Herein, we developed a photo/nickel dual-catalyzed defluorinative sulfonylation that rapidly and reliably synthesizes gem-difluoro allylsulfones. The merit of this protocol is exhibited by its mild conditions and wide scope, thus providing a novel strategy for the sulfonyl radical participating in radical defluorinative coupling.

C-Sulfonylation of 4-Alkylpyridines: Formal Picolyl C-H Activation via Alkylidene Dihydropyridine Intermediates

4-Picoline derivatives are converted to the corresponding aryl picolyl sulfones upon treatment with aryl sulfonyl chlorides and Et₃N in the presence of catalytic DMAP. The reaction proceeds smoothly for a variety of alkyl and aryl picolines using a range of aryl sulfonyl chlorides. The reaction is believed to involve N-sulfonyl 4-alkylidene dihydropyridine intermediates and results in formal sulfonylation of unactivated picolyl C-H bonds.

Easy access to α-carbonyl sulfones using cross-coupling of α-aryl-α-diazoesters with sulfonyl hydrazides

A facile synthesis of α-carbonyl sulfones has been accomplished by the cross-coupling of α-aryl-α-diazoesters with sulfonyl hydrazides in the presence of CuI and DBU. The reaction employs inexpensive and bench stable sulfonyl hydrazides as a sulfonyl source, and facilitates the migratory insertion with α-aryl-α-diazoesters under mild reaction conditions.

Nickel-catalyzed sulfonylative coupling of 2-chlorobenzothiazoles with sulfinates at room temperature

An efficient nickel-catalyzed cross-coupling for the synthesis of 2-sulfonylthiazoles from readily available 2-chlorobenzothiazoles and sodium sulfinates has been developed. A variety of 2-chlorobenzothiazoles and sulfinates having a diverse range of substitution patterns can undergo the coupling process successfully at room temperature. Avoiding the use of precious catalysts and sensitive ligands, moderate to excellent yields of various 2-sulfonylthiazoles were observed.

Substitution of α-Azido Sulfones with Thiolates to Form α-Azido Sulfides

Upon treatment of α-azido sulfones with a thiol in the presence of 1,1,3,3-tetramethylguanidine, substitution of the sulfonyl group with a thiolate occurred, resulting in the formation of α-azido sulfides. Based on experimental results and DFT calculations, a reaction mechanism that involves the addition of a thiolate to the azido group and generation of an alkylidene triazene is proposed.

Palladium-Catalyzed Regio- and Stereoselective Coupling of Alkynylsulfones with Alkenes: Access to Dichlorinated Vinyl Sulfones

A palladium-catalyzed coupling reaction of alkynylsulfones with alkenes has been described, which provides an efficient and practical entry to various functionalized dichlorinated vinyl sulfones. This method features excellent regio- and stereoselectivities, good functional group compatibility, as well as mild reaction conditions. Mechanistic studies suggest that the reaction goes through sequential syn-chloropalladation, alkene insertion, and C(sp³)-Cl bond formation processes, and the sulfonyl group is crucial to the stereoselectivity control of the reaction.

Photomediated Tandem Sulfonyl Addition-Chemoselective N-Cyclization of o-Alkenyl Aryl Ureas: Direct Assembly of Functionalized Dihydroquinazolinones

Photoredox-mediated tandem addition-chemoselective cyclization of o-alkenyl aryl ureas is reported for the synthesis of sulfonyl and activated alkyl-decorated dihydroquinazolinones. By a careful choice of o-alkenyl aryl urea starting materials, we achieved chemoselective N-cyclization in the presence of more reactive amidic oxygen. We have demonstrated the scope of the methodology with a variety of sulfonyl chlorides and activated alkyl halides. Finally, large-scale synthesis of sulfonyl-substituted dihydroquinazolinone showcases the synthetic utility of the methodology.

A regio- and stereoselective Heck-Matsuda process for construction of γ-aryl allylsulfonyl fluorides

A highly efficient regio- and stereoselective Heck–Matsuda method was developed employing aryl diazoniums and allylsulfonyl fluorides for the construction of a class of novel γ-aryl allylsulfonyl fluorides in the presence of Pd(OAc)₂ and PPh₃. The method features excellent regio- and stereoselectivity (up to 100% E-selectivity), broad substrate scope and mild reaction conditions. Further application of γ-aryl allylsulfonyl fluoride in SuFEx reactions was achieved to provide their corresponding sulfonates and sulfonamides in excellent yields.

A Heck–Matsuda reaction of aryl diazoniums with allylsulfonyl fluorides for the construction of γ-aryl allylsulfonyl fluorides was developed.

Catalytic Enantioselective Entry to Triflones Featuring a Quaternary Stereocenter

A highly enantioselective one-pot synthesis of functionalized triflones, bearing a quaternary stereocenter, has been developed, exploiting the Michael reaction of α-(trifluoromethylsulfonyl) aryl acetic acid esters with N-acryloyl-1H-pyrazole catalyzed by commercially available Takemoto’s catalyst, followed by nucleophilic acyl substitution with alcohols. Preliminary investigations highlighted the attractive potential of the triflinate anion as the leaving group for stereocontrolled postfunctionalizations.

Efficient Synthesis of 3-Sulfonyl-2-sulfonylmethyl-2H-chromenes via Tandem Knoevenagel Condensation/Oxa-Michael Addition Protocol

An organocatalytic [4 + 2] cascade annulation of salicylaldehydes and 1,3-bisarylsulfonylpropenes has been developed. This protocol enables the efficient and straightforward synthesis of a new series of 3-sulfonyl-2-sulfonylmethyl-2H-chromenes that are useful for exploring pharmacologically valued compounds. Further reductive modifications result in 3-desulfonylated chromene or chromane derivatives. This protocol can be expanded to the synthesis of 3-sulfonyl-2-sulfonylmethyl 1,2-dihydroquinoline.

Visible-Light-Induced Tandem Reaction of Allenes with Selenesulfonates Leading to (E)-2,3-Disulfonylpropene Derivatives

A visible-light-induced tandem reaction of allenes with selenesulfonates was developed, providing (E)-2,3-disulfonylpropene derivatives in moderate to good yields. This reaction was featured with simple operation, good regioselectivity and stereoselectivity, and wide functional group tolerance. Photoinduced radical additions via energy transfer were proposed.

Aryldiazonium Salts and DABSO: a Versatile Combination for Three-Component Sulfonylative Cross-Coupling Reactions

A combination of aryldiazonium salts and DABSO provides a unique opportunity for sulfonylative multicomponent cross-coupling reactions. Here, a copper-catalyzed three-component cross-coupling of aryldiazonium salts, DABSO with arylboronic acids to obtain medicinally relevant unsymmetrical diarylsulfones is disclosed. Interestingly, a catalyst-free approach for the synthesis of arylvinylsulfones from the corresponding vinyl boronic acid or vinyl halides is explored under basic condition. Tethered aryldiazonium salts provided the corresponding annulated alkylvinylsulfones via alkene difunctionalization under the same transition metal-free condition. Mechanistically, these multicomponent reactions proceed through a single electron pathway by the formation of arylsulfonyl radical as a key intermediate.

Photons or Electrons? A Critical Comparison of Electrochemistry and Photoredox Catalysis for Organic Synthesis

Redox processes are at the heart of synthetic methods that rely on either electrochemistry or photoredox catalysis, but how do electrochemistry and photoredox catalysis compare? Both approaches provide access to high energy intermediates (e.g., radicals) that enable bond formations not constrained by the rules of ionic or 2 electron (e) mechanisms. Instead, they enable 1e mechanisms capable of bypassing electronic or steric limitations and protecting group requirements, thus enabling synthetic chemists to disconnect molecules in new and different ways. However, while providing access to similar intermediates, electrochemistry and photoredox catalysis differ in several physical chemistry principles. Understanding those differences can be key to designing new transformations and forging new bond disconnections. This review aims to highlight these differences and similarities between electrochemistry and photoredox catalysis by comparing their underlying physical chemistry principles and describing their impact on electrochemical and photochemical methods.

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.

Photoredox-catalyzed synthesis of sulfonated oxazolines from N-allylamides through the insertion of sulfur dioxide

Photoredox-catalyzed generation of sulfonated oxazolines starting from N-allylamides, DABCO·(SO2)2, and aryldiazonium salts has been developed and a range of sulfonated oxazolines were obtained in moderate to good yields.

Recent Progress and Emerging Technologies towards a Sustainable Synthesis of Sulfones

Sulfones play a pivotal role in modern organic chemistry. They are highly versatile building blocks and find various applications as drugs, agrochemicals, or functional materials. Therefore, sustainable access to this class of molecules is of great interest. Herein, the goal was to provide a summary on recent developments in the field of sustainable sulfone synthesis. Advances and existing limitations in traditional approaches towards sulfones were reviewed on selected examples. Furthermore, novel emerging technologies for a more sustainable sulfone synthesis and future directions were discussed.

Benzannulation and Hydrocarboxylation Methods for the Synthesis of a Neopentylene-Fused Analogue of Ibuprofen

Neopentylene ring fusions (ring-fused 4,4-dimethylcyclopentane polycycles) are found in many natural products, but they are largely absent from synthetic compound libraries and focused medicinal chemistry research. Here is reported a synthetic approach to one of the few non-natural product-based target compounds from medicinal chemistry that includes a neopentylene ring fusion: an analogue of ibuprofen referred to herein as "neoprofen". The approach features ring-opening fragmentation reactions of dimedone derivatives coupled with transition metal-catalyzed benzannulation and hydrocarboxylation methods.