Desulfonylative Functionalization of Organosulfones via Inert (Hetero)Aryl C(sp2)-SO2 Bond Cleavage

As "chemical chameleons," organosulfones have been widely applied in various desulfonylative functionalization reactions. However, the desulfonylative functionalization of (hetero)arylsulfones through the cleavage of inert C(sp2)-SO2 bonds remains a challenging and underexplored task. Over the past twenty years, the use of (hetero)arylsulfones as arylation reagents has gradually gained attention in diverse cross-coupling reactions under specific catalytic conditions, especially in transition metal-catalysis and photocatalysis chemistry. In this review, we discuss the representative accomplishments and mechanistic insights achieved in desulfonylative reactions of inactive C(sp2)-SO2 bonds in (hetero)arylsulfones, including: (i) transition-metal-catalyzed desulfonylative cross-coupling reactions and (ii) photo-/electrocatalytic radical desulfonylative coupling reactions. We anticipate that this review will provide an overall perspective in this area to a general audience of researchers and stimulate further innovative strategies for desulfonylative functionalization of inert arylsulfones.

Synthesis of 1,2,3-triazole-piperazin-benzo[b][1,4]thiazine 1,1-dioxides: antibacterial, hemolytic and in silico TLR4 protein inhibitory activities

In this study, we designed and synthesized a number of novel 1,2,3-triazole-piperazin-benzo[b][1,4]thiazine 1,1-dioxide derivatives and investigated their in vitro antibacterial and hemolytic activity. When compared to the lead chemical, dicloxacillin, the majority of the compounds demonstrated acceptable activity. Among them, the most promising compounds 6e, 6g, 6i, 8d, and 8e exhibited excellent antibacterial activity against the methicillin-susceptible S. aureus (MSSA), methicillin-resistant S. aureus (MRSA), and vancomycin-resistant S. aureus (VRSA) with MIC values of 1.56 ± 0.22 to 12.5 ± 1.75 μg mL-1, respectively, The percentage of hemolysis ranged from 21.3 μg mL-1 to 33.8 μg mL-1. Out of the six compounds (6i, 6e, 6f, 6g, 8e, 8d) tested compound 8e and 8d displayed minimal or negligible hemolytic activity across all the tested concentrations 29.6% and 30.2% recorded at 100 μg mL-1 concentration respectively. In silico docking studies were performed to evaluate the molecular interactions of 6e, 6f, 6g, 6i, 8d, and 8e compounds with Human, Mouse and Bovine TLR4 proteins (PDB: 3FXI, 3VQ1, 3RG1) and observed that three of the compounds (6i, 8d, and 8i) had appreciable binding energies ranging from -8.5 to -9.0 Kcal mol-1. Finally, the in silico pharmacokinetic profile was predicted for potent compounds 8d, 8e and 6i using SWISS/ADME, All compounds investigated in this study adhered to Lipinski's rule of five with slight deviation in molecular weight (8d and 8e).

Cross-Electrophile Coupling of Benzyl Halides and Disulfides Catalyzed by Iron

Cross-electrophile couplings are influential reactions that typically require a terminal reductant or photoredox conditions. We discovered an iron-catalyzed reaction that couples benzyl halides with disulfides to yield thioether products in the absence of a terminal reductant and under photoredox conditions. The disclosed platform proceeds without sulfur-induced catalyst poisoning or the use of an exogenous base, supporting a broad scope and circumventing undesired elimination pathways. We applied the developed chemistry in a new mode of disulfide bioconjugation, drug synthesis, gram-scale synthesis, and product derivatization. Lastly, we performed mechanistic experiments to better understand the stereoablative reaction between two electrophiles. Disulfides and benzylic thioethers are imperative for biological and pharmaceutical applications but remain severely understudied in comparison to their ethereal and amino counterparts. Hence, we expect this platform of iron catalysis and the downstream applications to be of interest to the greater scientific community.

Principal component analysis-multivariate adaptive regression splines (PCA-MARS) and back propagation-artificial neural network (BP-ANN) methods for predicting the efficiency of oxidative desulfurization systems using ATR-FTIR spectroscopy

Oxidative desulfurization (ODS) of diesel fuels has received attention in recent years due to mild working conditions and effective removal of the aromatic sulfur compounds. There is a need for rapid, accurate, and reproducible analytical tools to monitor the performance of ODS systems. During the ODS process, sulfur compounds are oxidized to their corresponding sulfones which are easily removed by extraction in polar solvents. The amount of extracted sulfones is a reliable indicator of ODS performance, showing both oxidation and extraction efficiency. This article studies the ability of a non-parametric regression algorithm, principal component analysis-multivariate adaptive regression splines (PCA-MARS) as an alternative to back propagation artificial neural network (BP-ANN) to predict the concentration of sulfone removed during the ODS process. Using PCA, variables were compressed to identify principal components (PCs) that best described the data matrix, and the scores of such PCs were used as input variables for the MARS and ANN algorithms. Thecoefficientofdeterminationincalibration (R²_c), root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were calculated for PCA-BP-ANN (R²_c = 0.9913, RMSEC = 2.4206 and RMSEP = 5.7124) and PCA-MARS (R²_c = 0.9841, RMSEC = 2.7934 and RMSEP = 5.8476) models and were compared with the genetic algorithm partial least squares (GA-PLS) (R²_c = 0.9472, RMSEC = 5.5226 and RMSEP = 9.6417) and as the results reveal, both methods are better than GA-PLS in terms of prediction accuracy. The proposed PCA-MARS and PCA-BP-ANN models are robust models that provide similar predictions and can be effectively used to predict sulfone containing samples. The MARS algorithm builds a flexible model using simpler linear regression and is computationally more efficient than BPNN due to data-driven stepwise search, addition, and pruning.

Adsorption and Dissociation of R-Methyl p-Tolyl Sulfoxide on Au(111)

Sulfur-based molecules producing self-assembled monolayers on gold surfaces have long since become relevant functional molecular materials with many applications in biosensing, electronics, and nanotechnology. Among the various sulfur-containing molecules, the possibility to anchor a chiral sulfoxide to a metal surface has been scarcely investigated, despite this class of molecules being of great importance as ligands and catalysts. In this work, (R)-(+)-methyl p-tolyl sulfoxide was deposited on Au(111) and investigated by means of photoelectron spectroscopy and density functional theory calculations. The interaction with Au(111) leads to a partial dissociation of the adsorbate due to S-CH₃ bond cleavage. The observed kinetics support the hypotheses that (R)-(+)-methyl p-tolyl sulfoxide adsorbs on Au(111) in two different adsorption arrangements endowed with different adsorption and reaction activation energies. The kinetic parameters related to the adsorption/desorption and reaction of the molecule on the Au(111) surface have been estimated.

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.

Syn-Selective Chlorosulfonylation of Alkynes via a Copper-Powder-Initiated Atom Transfer Radical Addition Reaction and Mechanistic Studies

Copper-powder-catalyzed syn-selective chlorosulfonylation of readily available alkynes by an atom transfer radical addition (ATAR) process has been developed, providing straightforward access to a broad range of (Z)-β-chlorovinylsulfones in good yields under mild conditions. In addition, this method is ligand-free and features excellent stereoselectivity and high atom economy. Moreover, the product was obtained without an apparent loss of yield when the reaction was performed on the gram scale at a low catalyst loading. In this reaction, the copper powder not only acts as a sulfone radical initiator but also produces the catalytically active CuCl species. Mechanistic investigations and DFT calculation studies revealed that the stereoselectivity is controlled by the thermodynamic stabilities of the in situ-generated cyclic alkenyl Cu^II complex intermediate, which can serve as a chlorine atom transfer agent.

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.

Collective Synthesis of Illudalane Sesquiterpenes via Cascade Inverse Electron Demand (4 + 2) Cycloadditions of Thiophene S,S-Dioxides

Thiophene S,S-dioxides are underutilized tools for the de novo construction of benzene rings in organic synthesis. We report a collective synthesis of nine illudalane sesquiterpenes using bicyclic thiophene S,S-dioxides as generalized precursors to the indane core of the natural products. Exploiting furans as unusual dienophiles in this inverse electron demand Diels-Alder cascade, this concise and convergent approach enables the synthesis of these targets in as little as five steps. Theoretical studies rationalize the reactivity of thiophene S,S-dioxides with both electron-poor and electron-rich dienophiles and reveal reaction pathways involving either nonpolar pericyclic or bifurcating ambimodal cycloadditions. Overall, this work demonstrates the wider potential of thiophene S,S-dioxides as convenient and flexible precursors to polysubstituted arenes.

Synthesis of Polysubstituted Ferrocenesulfoxides

The purpose of the study is to design synthetic methodologies, especially directed deprotometalation using polar organometallic reagents, to access polysubstituted ferrocenesulfoxides. From enantiopure 2-substituted (SiMe3, PPh2) S-tert-butylferrocenesulfoxides, a third substituent was first introduced at the 5 position (SiMe3, I, D, C(OH)Ph2, Me, PPh2, CH2NMe2, F) and removal of the trimethylsilyl group then afforded 2-substituted ferrocenesulfoxides unreachable otherwise. Attempts to apply the "halogen dance" reaction to the ferrocenesulfoxide series led to unexpected results although rationalized in light of calculated pKa values. Further functionalizations were also possible. Thus, new enantiopure, planar chiral di- and trisubstituted ferrocenes have been obtained, in addition to several original 2-substituted, 2,3- and 2,5-disubstituted, 2,3,5-trisubstituted and even 2,3,4,5-tetrasubstituted ferrocenesulfoxides, also enantiopure.

Facile construction of C,N-disulfonated 5-amino pyrazoles through an iodine-catalyzed cascade reaction

A green and facile synthesis of previously unreported C,N-disulfonated 5-amino pyrazoles was established through an iodine-catalyzed cascade reaction.

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

As the "chemical chameleon", sulfonyl-containing compounds and their variants have been merged with various types of reactions for the efficient construction of diverse molecular architectures by taking advantage of their incredible reactive flexibility. Currently, their involvement in radical transformations, in which the sulfonyl group typically acts as a leaving group via selective C-S, N-S, O-S, S-S, and Se-S bond cleavage/functionalization, has facilitated new bond formation strategies which are complementary to classical two-electron cross-couplings via organometallic or ionic intermediates. Considering the great influence and synthetic potential of these novel avenues, we summarize recent advances in this rapidly expanding area by discussing the reaction designs, substrate scopes, mechanistic studies, and their limitations, outlining the state-of-the-art processes involved in radical-mediated desulfonylation and related transformations. With a specific emphasis on their synthetic applications, we believe this review will be useful for medicinal and synthetic organic chemists who are interested in radical chemistry and radical-mediated desulfonylation in particular.

Direct halosulfonylation of alkynes: an overview

The difunctionalization reactions of easily available and inexpensive alkynes have emerged as a reliable, powerful, and step-economical approach for the construction of highly substituted complex alkenes in a one-pot manner, without the need for isolation of intermediates. A wide variety of transformations based on this concept have been successfully achieved for the preparation of synthetically and biologically important β-halovinyl sulfone scaffolds. In this Review, we summarize the recent advances and developments in this field and present a comprehensive overview of halosulfonylation of alkyne substrates with emphasis on the mechanistic features of the reactions.

Visible-Light Photoredox-Catalyzed Sulfonyl Lactonization of Alkenoic Acids with Sulfonyl Chlorides for Sulfonyl Lactone Synthesis

A visible-light photoredox-catalyzed sulfonyl lactonization of unsaturated carboxylic acids with sulfonyl chlorides is described. This reaction features good functional group tolerance and a broad substrate scope, providing a simple and efficient protocol to access a wide range of sulfonyl lactones in high to excellent yields. Preliminary mechanistic investigations suggested that a free-radical pathway should be involved in the process.

Transition Metal-Free De Novo Synthesis of Sulfonated Pyrazoles from Sulfonyl Hydrazides, 1,3-Diketones, and Sodium Sulfinates at Room Temperature

A transition metal-free method for de novo construction of diverse sulfonated pyrazoles from readily available sulfonyl hydrazides, 1,3-diketones, and sodium sulfinates was established under mild conditions. Pyrazoles bearing two different sulfonyl groups were obtained in one step. The method features a diversity of substituents of the pyrazole products and a remarkably simple work-up.

Design, crystal structure determination, molecular dynamic simulation and MMGBSA calculations of novel p38-alpha MAPK inhibitors for combating Alzheimer's disease

The hallmark of the Alzheimer's disease (AD) is the accumulation of aggregated, misfolded proteins. The cause for this accumulation is increased production of misfolded proteins and impaired clearance of them. Amyloid aggregation and tau hyperphosphorylation are the two proteinopathies which accomplish deprivation of cell and tissue hemostasis during neuropathological process of the AD, as a result of which progressive neuronal degeneration and the loss of cognitive functions. p38 mitogen-activated protein kinase (p38 MAPK) has been implicated in both the events associated with AD: tau protein phosphorylation and inflammation. p38α MAPK pathway is activated by a dual phosphorylation at Thr180 and Tyr182 residues. Clinical and preclinical evidence implicates the stress related kinase p38α MAPK as a potential neurotherapeutic target. Drug design of p38α MAPK inhibitors is mainly focused on small molecules that compete for Adenosine triphosphate in the catalytic site. Here we have carried out the synthesis of phenyl sulfonamide derivatives Sulfo (I) and Sulfo (II). Crystal structures of Sulfo (I) and Sulfo (II) were solved by direct methods using SHELXS-97. Sulfo (I) and Sulfo (II) have R_int values of 0.0283 and 0.0660, respectively, indicating good quality of crystals and investigated their ability against p38α MAPK. Docking studies revealed that the Sulfo (I) had better binding affinity (-62.24 kcal/mol) as compared to Sulfo (II) and cocrystal having binding affinity of -54.61 kcal/mol and -59.84 kcal/mol, respectively. Molecular dynamics simulation studies of Sulfo (I) and cocrystal of p38α MAPK suggest that during the course of 30 ns simulation run, compound Sulfo (I) attained stability, substantiating the consistency of its binding to p38α MAPK compared to cocrystal. Binding free energy analysis suggests that the compound Sulfo (I) is better than the cocrystal. Thus, this study corroborates the therapeutic potential of synthesized Sulfo (I) in combatting AD.Communicated by Ramaswamy H. Sarma.

Cascade Cross-Coupling of Dienes: Photoredox and Nickel Dual Catalysis

Chemical transformations based on cascade reactions have the potential to simplify the preparation of diverse and architecturally complex molecules dramatically. Herein, we disclose an unprecedented and efficient method for the cross-coupling of radical precursors, dienes, and electrophilic coupling partners via a photoredox- and nickel-enabled cascade cross-coupling process. The cascade reaction furnishes a diverse array of saturated carbo- and heterocyclic scaffolds, thus providing access to a quick gain in C-C bond saturation.

Fenton-Inspired C-H Functionalization: Peroxide-Directed C-H Thioetherification

Substoichiometric iron mediates the thioetherification of unactivated aliphatic C-H bonds directed by resident silylperoxides. Upon exposure to a catalytic amount of iron(II) triflate, TIPS-protected peroxides bearing primary, secondary, and tertiary C-H sites undergo chemoselective thioetherification of remote C-H bonds with diaryl disulfides. The reaction demonstrates a broad substrate scope and functional group tolerance without the use of any noble metal additives. Mechanistic experiments suggest that the reaction proceeds through 1,5-H atom abstraction by a hydroxyl radical generated with iron.

Role of Musa paradisiaca ascorbate peroxidase in the transformation of methyl phenyl sulfide to its sulfoxide

An ascorbate peroxidase from a new source Musa paradisiaca leaf juice has been purified to homogeneity using a simple procedure involving concentration by ultra filtration and anion exchange chromatography on diethyl amino ethyl [DEAE] cellulose column. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis [SDS-PAGE] analysis of the purified enzyme has shown a single protein band of molecular mass 208.9 kDa which has been confirmed by native-PAGE and intact mass analysis by mass spectrometry. The Km and k_cat values of the enzyme using ascorbate and H₂O₂ as the variable substrates were 0.13 m mol L^-1, 40.42 s^-1 and 0.23 m mol L^-1, 27.24 s^-1, respectively. The pH and temperature optima of the enzyme were 7.0 and 298 K, respectively. The enzyme transformed approximately 97% methyl phenyl sulfide to its sulfoxide. The product was racemic mixture.

Synthesis of multisubstituted arylsulfones via a one-pot, three-component [3 + 3] benzannulation reaction

A one-pot, three-component [3 + 3] benzannulation reaction of α,β-unsaturated carbonyl compounds, bromoallylic sulfones, and sodium sulfinates provided multisubstituted arylsulfones with moderate to good yields.

Facile synthesis of substituted diaryl sulfones via a [3 + 3] benzannulation strategy

A metal-free and efficient synthesis of highly substituted diaryl sulfones via a base-mediated [3 + 3] benzannulation strategy.

Preparation, characterization, and catalytic performances of a pyrazine dicarboxylate-bridging rare-earth-containing polytungstoarsenate aggregate for selective oxidation of thiophenes and deep desulfurization of model fuels

A new polytungstoarsenate, K₆LiH₆[Ce₄(H₂O)₁₄(pzdc)(H₂pzdc)As₃W₂₉O₁₀₃]·22H₂O (1), was synthesized via a conventional aqueous solution method.

Synthesis of Functionalized Pyrazoles via 1,3-Dipolar Cycloaddition of α-Diazo-β-ketophosphonates, Sufones and Esters with Electron-Deficient Alkenes

1,3-Dipolar cycloaddition of diazo compounds with olefinic substrates is a promising atom-economic strategy for the construction of functionalized pyrazoles. Over the last few years, our group has been engaged in the synthesis of phosphonyl/sulfonylpyrazoles and pyrazole esters by employing Bestmann-Ohira Reagent (BOR) and its sulfur and ester analogs as 1,3-dipole precursors with various dipolarophiles. This account describes the novel synthetic methods developed in our laboratory, in the perspective of closely related work by others, for the synthesis of phosphonyl/sulfonylpyrazoles, pyrazole esters and the total synthesis of Withasomnine, a natural product, by using 1,3-dipolar cycloaddition as the key step.

Catalytic Asymmetric 1,3-Dipolar Cycloaddition of β-Fluoroalkylated α,β-Unsaturated 2-Pyridylsulfones with Nitrones for Chiral Fluoroalkylated Isoxazolidines and γ-Amino Alcohols

2-Pyridylsulfone- and fluoroalkylated group-activated olefins underwent highly efficient diastereo- and enantioselective 1,3-dipolar cycloadditions across various aromatic and aliphatic nitrones in the presence of a chiral Ni^II /bis(oxazoline) catalyst. The process was tuned by 4 Å molecular sieves, chiral bis(oxazoline) ligands, reaction solvents, and temperature. A wide array of optically pure fluoroalkylated isoxazolidines were obtained, thus facilitating the asymmetric synthesis of an enantioenriched α-trifluoromethylated γ-amino alcohol in gram-scale and a trifluoromethylated derivative of 1,3-oxazinan-2-one with potential pharmaceutical interest. A stereochemical model, based on the absolute configuration of one adduct and some control experiments, was postulated to account for the observed endo- and enantioselectivity.

Metal-free molecular iodine-catalyzed direct sulfonylation of pyrazolones with sodium sulfinates leading to sulfonated pyrazoles at room temperature

A simple and highly efficient iodine-catalyzed sulfonylation of pyrazolones with sodium sulfinates has been developed under mild and metal-free conditions.

Synthesis of Alkyl Aryl Sulfones via Reaction of N-Arylsulfonyl Hydroxyamines with Electron-Deficient Alkenes

Alkyl aryl sulfones were prepared in high yields via the reaction of N-arylsulfonyl hydroxylamines with electron-deficient alkenes. These reactions have the advantages of simplicity, easily available starting materials and mild reaction conditions.

A Green, One-Pot Formation of Imidazolone and Pyrimidinone Derivatives Containing a Sulfonyl Group

The synthesis of sulfonyl-imidazolone derivatives via a four-component reaction between sodium arylsulfinates, trichloroacetonitrile, benzylamines and acetylenedicarboxylates in H2O at room temperature is described. When alkyl propiolate was used instead of acetylenedicarboxylates, sulfonyl-pyrimidinone was obtained.