Aryl Sulfides Research Articles

Electrochemical Stereoselective Synthesis of (Z)‐Allyl Aryl Selenides and Sulfides from Baylis‐Hillman Acetates

AbstractThis research presents a method for the oxidative selenylation and thiolylation of Morita‐Baylis‐Hillman adducts through constant‐current electrolysis in an undivided cell at room temperature. The reaction enables direct production of trisubstituted (Z)‐allyl aryl selenides and sulfides with yields of 27–98%. A wide variety of different functionalities are well tolerated under these reaction conditions. This strategy could be carried out on gram scale and several synthetic transformations were accomplished for the construction of other allyl selenide derivatives. Control experiments and mechanistic studies indicate a radical or an ionic addition pathway for this electrochemical transformation.

Synthesis and Antitumor Activity of Benzoheterocyclic Aryl Sulfide

Synthesis and Antitumor Activity of Benzoheterocyclic Aryl Sulfide

Phosphonate-substituted porphyrins as efficient, cost-effective and reusable photocatalysts.

Recent advances in visible light photocatalysis represent a significant stride towards sustainable catalytic chemistry. However, its successful implementation in fine chemical production remains challenging and requires careful optimization of available photocatalysts. Our work aims to structurally modify bioinspired porphyrin catalysts, addressing issues related to their laborious synthesis and low solubility, with the goal of increasing their efficiency and developing reusable catalytic systems. We have demonstrated the catalytic potential of readily available meso-tetrakis[4-(diethoxyphosphoryl)phenyl]porphyrins (M(TPPP)). Novel metal (Pd(II), Co(II) and In(III)) complexes with this ligand were prepared in good yields. These chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence) and electrochemical methods. The introduction of phosphonate groups on the phenyl substituents of meso-tetraphenylporphyrins (M(TPP)) improves solubility in polar organic solvents without significantly altering the photophysical properties and photostability of complexes. This structural modification also leads to easier reductions and harder oxidations of the macrocycle for all investigated complexes compared to the corresponding TPP derivatives. The free base porphyrin, zinc(II), palladium(II), and indium(III) complexes were studied as photocatalysts for oxidation of sulfides to sulfoxides using molecular oxygen as a terminal oxidant. Both dialkyl and alkyl aryl sulfides were quantitatively transformed into sulfoxides under blue LED irradiation in the acetonitrile-water mixture (10 : 1 v/v) with a low loading (0.005-0.05 mol%) of porphyrin photocatalysts, where H2(TPPP) and Pd(TPPP) were found to be the most efficient. The reaction mechanism was studied using photoluminescence and EPR spectroscopies. Then, to access reusable catalysts, water-soluble derivatives bearing phosphonic acid groups, H2(TPPP-A) and Pd(TPPP-A), were prepared in high yields. These compounds were characterized using spectroscopic methods. Single-crystal X-ray diffraction analysis of Pd(TPPP-A) reveals that the complex forms a 3D hydrogen-bonded organic framework (HOF) in the solid state. Both H2(TPPP-A) and Pd(TPPP-A) were found to catalyze the photooxidation of sulfides by molecular oxygen in the acetonitrile-water mixture (1 : 1 v/v), while only Pd(TPPP-A) resulted in selective production of sulfoxides. The complex Pd(TPPP-A) was easily recovered through extraction in the aqueous phase and successfully reused in five consecutive cycles of the sulfoxidation reaction.

Effect of two-fold single-atom substitutions (S, Se; C, N) in band gap engineered donor-acceptor conjugated microporous polymers on the efficient aerobic photooxidation of aryl sulfides.

Substitution of a single atom in a photoactive system is capable of vastly altering its optoelectronic properties leading to the generation of an efficient photocatalyst. In this study, we explore the impact of two-fold single-atom substitutions on the optoelectronic properties and photocatalytic performance of donor-acceptor type conjugated microporous polymers (D-A CMPs). For this, three isostructural triphenylamine (TPA)-based D-A CMPs were synthesized namely PTPA-BT, PTPA-BS, and PTPA-PS containing 2,1,3-benzothiadiazole, 2,1,3-benzoselenadiazole and [1,2,5]selenadiazolo[3,4-c]pyridine as the acceptor moieties, respectively. Firstly, PTPA-BT and PTPA-BS were synthesized using the S to Se single-atom substitution strategy, followed by the synthesis of PTPA-PS employing a second C to N single-atom substitution. The effect of single-atom substitution demonstrated drastic changes in their band gap, conductivity, and charge carrier dynamics, which in turn impacted their photocatalytic activity, although the change in their porosity was not much pronounced. In terms of photocatalytic detoxification of sulfur mustards, the activities of D-A CMPs follow the trend: PTPA-BS > PTPA-PS > PTPA-BT. In comparison with PTPA-BT (containing C, S) and PTPA-PS (containing N, Se), PTPA-BS (containing C, Se) exhibits a higher photocatalytic activity towards the photooxidation of thioanisole with >99% conversion and ∼93% isolated yield under visible-light illumination, which is attributed to its lower interfacial charge transfer resistance, stronger photocurrent response, optimal band gap and higher activity to generate superoxide anion radicals. Therefore, the two-fold single-atom substitution strategy is crucial for optimizing D-A CMPs for the photocatalytic oxidation of aryl sulfides. This approach allows fine-tuning of the optoelectronic properties to enhance photocatalytic efficiency and performance.

Synthesis of Perfluoro Alkyl/Alkenyl Aryl Sulfide: C−S Coupling Reaction Using Hexafluoropropylene Dimer (HFPD) as a Building Block

AbstractEfficient approaches to perfluoroalkyl/alkenyl aryl sulfides were accomplished by a C−S coupling reaction under mild conditions. Hexafluoropropylene dimer was employed as a versatile building block for the perfluoroalkylation and perfluoroalkenylation of thiophenol. The application of the synthetic strategy was demonstrated by the high‐yield transformation of a broad range of aryl derivatives. A plausible mechanistic explanation was proposed to elaborate the differences between the two reaction pathways. The methodology provides straightforward and convenient access to aryl sulfides constituting C6 perfluoroalkyl and perfluoroalkenyl substituents.

Immobilized zirconium‐thiouracil complex on MCM‐41 magnetic mesoporous as a recyclable nanocatalyst for carbon‐sulfide bond formation

The synthesis and characterization of MCM‐41 magnetic mesoporous material, which has been modified with zirconium‐thiouracil complex (M‐MCM‐41@TU‐ZrO), has been conducted and thoroughly analyzed using an array of techniques such as X‐ray diffraction (XRD), energy‐dispersive X‐ray spectroscopy (EDX), elemental mapping, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT‐IR), Brunauer‐Emmett‐Teller (BET), inductively coupled plasma‐optical emission spectrometry (ICP‐OES), thermogravimetric analysis (TGA) and vibrating sample magnetometer (VSM). The catalytic performance of M‐MCM‐41@TU‐ZrO was tested in the synthesis of phenyl aryl sulfides through a three‐component coupling reaction of aryl halides/phenolic esters with phenylboronic acid and sulfur powder in the presence of a base in PEG200 at 80–90°C. Also, the synthesis of symmetrical diaryl sulfides using aryl halides and sulfur powder and M‐MCM‐41@TU‐ZrO as a nanocatalyst in dimethyl sulfoxide at 120°C was investigated. A major novelty is that this is the first time that a highly efficient magnetically recyclable zirconium nanocatalyst is used for the synthesis of unsymmetrical diaryl sulfides in the presence of arylboronic acid/S8 system as thiolating agent and phenolic esters as cross‐coupling partners. The other advantages of this method are as follows: (a) the structurally diverse phenyl aryl sulfides have been synthesized in good to high yields in PEG as a green solvent; (b) starting materials, sulfur source, and catalyst are commercially available, cheap, non‐toxic, and chemically stable; and (c) M‐MCM‐41@TU‐ZrO nanocatalyst was easily removed from the reaction mixture using an external magnet and reused numerous times without any significant change in activity.

Nickel-catalyzed synthesis of aryl sulfides from aromatic primary amides and thioethers via aryl exchange strategy

Herein, a nickel-catalyzed synthesis of aryl sulfide through a formal aryl exchange reaction between aromatic amide and thioether was reported. This work not only realized the activation of non-activated primary amides through an unconventional dehydration strategy, but also provided a practical and facile method for aryl sulfide synthesis without odorous and toxic thiols.

High permeance nanofiltration membrane for harsh organic solvent based on spiral-ring polyesters

Currently, many polymeric membranes are poorly tolerated in harsh (strong polar aprotic) solvents like dimethylformamide (DMF) and N-methylpyrrolidone (NMP) and are not applicable to organic solvent nanofiltration (OSN). In this study, we combined the oxidized poly (arylene sulfide sulfone) (OPASS) supports with excellent organic solvent resistance and the spiral-ring polyester interfacial polymerization (IP) layer together to fabricate ultra-resistant and high permeance membranes for OSN. The tetramethyl-1,1′-spirobisindane-6,6′diol (SBI), a contorted diphenol monomer with a spiral-ring structure, was preferentially selected from six types of polyphenols based on molecular simulations and experimental results. It was conducted to react with trimesoyl chloride (TMC) via interfacial polymerization to yield a polyester separation layer of thin film composites (TFC). Investigating the different alkali ratios and types revealed that the alkali added in the aqueous phase to improve the solubility of the SBI could cause hydrolysis of the polyester layer generated by IP, which led to increased membrane permeance and reduced rejection, and the more alkali and the stronger the alkali used, the more severe the hydrolysis. Besides, DMF activation treatment to the TFC membrane improved the ethanol permeance by at least four times while maintaining high congo red rejection. As a result, combining the effects of alkali and DMF activation, the representative TFC membranes fabricated in our work exhibited excellent permeance of 21.5±1.3, 9.0±1.1 L m−2 h−1 bar−1 for DMF and NMP, respectively, and high rejection rates (≥ 93%) for congo red (Mw 696.7 Da), higher than the earlier reports. This research presents a new and straightforward approach to developing TFC membranes with high-efficiency filtration capabilities, suitable for harsh organic solvent separation applications.

Room Temperature Anhydrous Suzuki-Miyaura Polymerization Enabled by C-S Bond Activation.

The Suzuki-Miyaura cross-coupling is one of the most important and powerful methods for constructing C-C bonds. However, the protodeboronation of arylboronic acids hinder the development of Suzuki-Miyaura coupling in the precise synthesis of conjugated polymers (CPs). Here, an anhydrous room temperature Suzuki-Miyaura cross-coupling reaction between (hetero)aryl boronic esters and aryl sulfides was explored, of which universality was exemplified by thirty small molecules and twelve CPs. Meanwhile, the mechanistic studies involving with capturing four coordinated borate intermediate revealed the direct transmetalation of boronic esters in the absence of H2 O suppressing the protodeboronation. Additionally, the room temperature reaction significantly reduced the homocoupling defects and enhanced the optoelectronic properties of the CPs. In all, this work provides a green protocol to synthesize alternating CPs.

Room Temperature Anhydrous Suzuki–Miyaura Polymerization Enabled by C−S Bond Activation

AbstractThe Suzuki–Miyaura cross‐coupling is one of the most important and powerful methods for constructing C−C bonds. However, the protodeboronation of arylboronic acids hinder the development of Suzuki–Miyaura coupling in the precise synthesis of conjugated polymers (CPs). Here, an anhydrous room temperature Suzuki–Miyaura cross‐coupling reaction between (hetero)aryl boronic esters and aryl sulfides was explored, of which universality was exemplified by thirty small molecules and twelve CPs. Meanwhile, the mechanistic studies involving with capturing four coordinated borate intermediate revealed the direct transmetalation of boronic esters in the absence of H2O suppressing the protodeboronation. Additionally, the room temperature reaction significantly reduced the homocoupling defects and enhanced the optoelectronic properties of the CPs. In all, this work provides a green protocol to synthesize alternating CPs.

Cis-dioxomolybdenum(VI) complex bearing tridentate ONO isonicotinoyl hydrazone Schiff base: Synthesis, characterization, crystal structure, and catalytic activity investigation for the oxidation of sulfides

A cis-dioxomolybdenum Schiff base complex, MoO2(L)(CH3OH), has been synthesized by reacting MoO2(acac)2 with isonicotinic acid hydrazide in refluxed methanol. The synthesized dioxomolybdenum complex was characterized by elemental analysis and diverse spectroscopic methods, for example, UV-Vis, FT-IR, and 1H and 13C NMR. The single crystal X-ray diffraction technique was used to determine the structure of the complex, which indicates that Mo(VI) ion is hexa coordinated and adopts a distorted octahedral coordination geometry on complexation. The synthesized complex is novel for its catalytic potential for the oxidation of aryl and alkyl sulfides under refluxing conditions in the presence of hydrogen peroxide and ethanol. This method generates the required sulfoxides and sulfones with high yields in short intervals of time.

Benzanthrone sulfides: synthesis, solvatochromism characterization and analysis of experimental photophysical parameters and theoretical calculations

In this paper the synthesis, characterization, and photophysical properties of benzanthrone-derived sulfides are discussed. The compounds were synthesized using a practical method of nucleophilic aromatic substitution reactions of 3-bromobenzanthrone with thiols. Structural characterization was conducted using nuclear magnetic resonance (NMR) and Fourier-transform (FTIR) spectroscopy and high-resolution mass spectrometry, confirming the chemical structures. The crystal structure of a compound was determined via X-ray diffraction, revealing π-π stacking interactions and intermolecular hydrogen bonding. Photophysical analysis showed solvatochromic effects (emission of light upon excitation from 507 nm in benzene to 591 nm in ethanol) and attributed fluorescence to intramolecular charge transfer. Computational analysis using DFT calculations provided further insights into the compounds' properties, including excited state energies and the potential for efficient intersystem crossing. Overall, the research provides a comprehensive understanding of the newly synthesized benzanthrone alkyl and aryl sulfides as well as a phenylselanyl derivative. The photophysical properties, charge transfer characteristics observed in the compounds and the solvatochromic effects exhibited by the compounds suggest their potential to be utilized for developing sensors for detecting environmental changes, chemical substances or biological targets.

Kinetic and Product Study of the S‐oxidation vs HAT Chemoselectivity in Reactions Promoted by Nonheme Iron(IV)‐oxo Complex/NHPI Mediator System

AbstractThe chemoselectivity between S‐oxidation and hydrogen atom transfer (HAT) from C−H bonds has been investigated in the oxidations of a series of aryl sulfides, alkyl aromatic compounds and benzylic alcohols promoted by the iron(IV)‐oxo complex [(N4Py)FeIV(O)]2+ (N4Py: N,N‐bis(2‐pyridylmethyl)‐N‐bis(2‐pyridyl)‐methylamine) either alone or in the presence of the N‐hydroxyphthalimide (NHPI) mediator via kinetic and product studies. Kinetic analyses indicate a generally higher reactivity of [(N4Py)FeIV(O)]2+ for S‐oxidation process while HAT is favored in the reactions promoted by phthalimide‐N‐oxyl radical (PINO) deriving from NHPI oxidation. Product analysis in intermolecular competitive oxidations confirms the kinetic results with sulfoxides obtained as major products in the oxidation promoted by [(N4Py)FeIV(O)]2+. Conversely, when NHPI is employed as a mediator, significant differences in terms of chemoselectivity are observed, and HAT‐derived products are obtained in higher yields which translate into an inversion of selectivity in the case of the substrates containing activated C−H bonds like diphenylmethane, triphenylmethane and benzylic alcohols. A similar change of chemoselectivity is also observed in the oxidation of aromatic substrates containing both a sulfur atom and α to OH benzylic C−H bonds, with the sulfoxide product more abundant in the absence of NHPI and carbonyl products prevailing with the [(N4Py)FeIV(O)]2+/NHPI system.

Dehydroaromatization of Indolines and Cyclohexanones with Thiol Access to Aryl Sulfides under Basic Conditions.

Aryl sulfides are common and ubiquitous motifs in natural products and pharmaceuticals. Presented herein is the first example of the synthesis of diaryl sulfide derivatives via dehydroaromatization under simple basic conditions. Dehydroaromatization reactions between indolines or cyclohexanones with aryl thiols are performed in an environmentally benign manner by the use of air (molecular oxygen) as the oxidant, with producing water as the only byproduct. The methodology provides a simple and practical route to diaryl sulfides with wide functional groups in good to excellent yields. Preliminary mechanistic studies suggest that a radical process is involved in the transformation.

Selective C−H Acyloxylation of Sulfides/Disulfides Enabled by Hypervalent Iodine Reagents

AbstractHerein, we report the α−C−H acyloxylation of sulfides and disulfides enabled by hypervalent iodine(III) reagents via photoredox catalysis. The methoxylbenziodoxole derivatives serve as the hydrogen atom transfer agent, the mild oxidant, and the acyloxylation source in the reaction. External nucleophiles can also be introduced to the α−C−H of sulfides. The reaction applies to various aryl and alkyl sulfides including methionine peptide derivatives. Disulfides are applicable for the first time with excellent chemoselectivity and functional group compatibility.

Palladium-Catalyzed Cyanation of Aryl Sulfonium Salts.

A palladium-catalyzed cyanation of aryl dimethylsulfonium salts using cheap, nontoxic, and bench-stable K4[Fe(CN)6]·3H2O as the cyanating reagent has been developed. The reactions proceeded well under base-free conditions with various sulfonium salts and provided aryl nitrile with yields of up to 92%. Aryl sulfides can be transformed to aryl nitriles directly via a one-pot process, and the protocol is scalable. Density functional theory calculations were performed to investigate the reaction mechanism that involved a catalytic cycle involving oxidative addition, ligand exchange, reductive elimination, and regeneration to yield the product.

New Strategy for Improvement of Interfacial Interactions between Poly(arylene sulfide sulfone) and Carbon Fiber by Grafting Polymeric Chains via Thiol-Ene Click Chemistry.

A simple and efficient strategy for enhancing the interfacial interaction in carbon fiber-reinforced poly(arylene sulfide sulfone) (CF/PASS) composites by grafting polymeric chains via thiol-ene click chemistry is reported here. Simultaneously, three thiol compounds and carbon nanotubes were grafted on CFs to explore the reaction between the CF and thiol groups. X-ray photoelectron spectroscopy, Raman spectroscopy, and normalized temperature-dependent IR spectroscopy results confirm the successful grafting of three thiol compounds, carbon nanotubes, and polymer chains. Similarly, obvious changes on the CF surface can be seen before and after modification via scanning electron microscopy, such as grafted nanotubes and polymeric resin, and the increase in the modulus gradient and interfacial thickness of CF/PASS can be clearly seen via atomic force microscopy. All the results of micro and macro tests on mechanical properties indicate that connecting low molecular weight thiol-terminated PASS (HS-LPASS) onto CFs enhances the interfacial property and mechanical performance of CF/PASS to a greater extent. The interfacial shear strength, interlaminar shear strength, and tensile strength of CF@HS-LPASS-reinforced PASS (CF@HS-LPASS/PASS) increase significantly by 38.5, 43.6, and 24.4%, respectively. All the results demonstrate that thiol-ene click reactions can be used for CF modification; furthermore, in the presence of external stress, the grafted polymeric interphase can act as a "bridge layer" to improve the stress transfer efficiency.

Synthesis of Asymmetric Diaryl Sulfides via HI-Mediated C(sp2)-H Sulfenylation of Arenes with Sodium Sulfinates.

A novel hydroiodic acid-promoted metal-free C(sp2)-H sulfenylation of electron-rich arenes was developed using stable and easy-to-handle sodium sulfinates as sulfur sources. Diverse kinds of asymmetric aryl sulfides were afforded in good yields from various commercially available aromatic substrates under mild conditions. Comprehensive mechanistic experiments demonstrate that RSO2SR and RSSR are the key intermediates responsible for the redox process.

Oxidations of aromatic sulfides promoted by the phthalimide N-oxyl radical (PINO)

The oxidation of a series of alkyl aryl sulfides promoted by the phthalimide N-oxyl radical (PINO) has been investigated by kinetic and product analysis. Sulfoxides are formed as major reaction products in the oxidation of thioanisoles and benzyl phenyl sulfides. The observation of fragmentation products in the oxidation of 2-phenyl-2-propyl phenyl sulfide and diphenylmethyl phenyl sulfide indicates that the reaction involves an initial electron transfer reaction from the sulfide to PINO with the formation of aryl sulfide radical cations and the anion PINO-. Combination of the species then leads to a radical adduct precursor of sulfoxides while the rapid C–S cleavage occurs with aryl sulfide radical cations that can form the stable 2-phenyl-2-propyl or diphenylmethyl carbocation.

Photocatalytic Aryl Sulfide Oxidation Using 4-Nitrophenylacetylene-Modified Cu2O Crystals.

4-Nitrophenylacetylene-functionalized Cu2O rhombic dodecahedra and cubes have been used to photocatalyze aryl sulfide oxidation generating aryl sulfoxides. With an oxygen supply and light from a blue light-emitting diode (LED), the reaction can be completed in 12 h with a water and methanol mixed solution. Generally high product yields and excellent product selectivity of sulfoxides over sulfones were achieved. In particular, a thioanisole to methyl phenyl sulfoxide yield of 98% was obtained. A mechanistic study has revealed that photogenerated electrons, holes, and superoxide radicals are involved in the oxidation reaction. The benefit of simple photocatalyst preparation and molecular functionalization to boost catalytic performance shows that surface-controlled ionic solids can be very effective photocatalysts for some organic transformations.