Alkyl Sulfides Research Articles

Effect of organosilane agents on the vulcanizate structure and physical properties of silica-filled solution styrene butadiene rubber compounds

Physical properties of rubber compounds are affected by the filler-rubber interaction, filler dispersion in the rubber matrix, and crosslink structure formed during vulcanization. Organosilane agents are essentially used in silica-rubber compounds to inhibit the formation of silica agglomerates and increase the formation of silica-rubber networks. Generally, organosilane agents have an alkoxysilyl alkyl sulfide structure and are classified into silane coupling and covering agents depending upon the presence of sulfur. Coupling agents have a sulfur moiety and serve as a sulfur donor during the vulcanization process, thus increasing the formation of filler-rubber and chemical crosslink networks. On the other hand, covering agents promote the hydrophobation of silica surfaces, decreasing the adsorption loss of vulcanization additives, which increases the formation of chemical crosslink networks. This implies that organosilane agents can affect the vulcanizate structure, which causes a variation in the properties of silica compounds. Therefore, in this study, the effect of coupling (bis(3-triethoxysilylpropyl)disulfide (TESPD) and bis(3-triethoxysilylpropyl)tetrasulfide (TESPT)) agents and a covering (triethoxy(octyl)silane) agent on the vulcanizate structure and properties of silica compounds was investigated and compared. In the comparative study of coupling and covering agents, the influence of sulfur donors on the formation of vulcanizate structures was investigated. In the case of the coupling agents, the effect of sulfur rank on the vulcanizate structure and properties of silica-rubber compounds was quantitatively analyzed through various characterization techniques.

Highly carboxyl-decorated graphene oxide sheets as metal-free catalytic system for chemoselective oxidation of sulfides to sulfones

Highly-acidic graphene oxide in the presence of hydrogen peroxide was found to act as an efficient metal-free heterogeneous catalyst for oxidation of sulfides to sulfones under mild and neutral condition. Several factors such as catalyst amount, solvent, and reaction time pertaining to achieve the reactivity were also discussed. Sulfone formation increased with an increase in hydrogen peroxide concentration, temperature, and catalyst amounts. The uniqueness of this catalyst lies in its stability, cost-effective, ease in removal at the end of reaction, and chemoselective oxidation of alkyl and aryl sulfides to the corresponding sulfones. The catalyst is recyclable for at least four times only with the little reduction in oxidation of sulfides. Reaction kinetics was found to be pseudo-first order and the calculated activation energy was 32.11 kJ/mol.

Highly luminescent anthracene sulfides. Synthesis, experimental and DFT study of their optical properties and interaction with electron deficient nitroaromatic compounds

Abstract We report on the synthesis, thermal and photooxidative behavior and optical properties of a series alkyl and aryl sulfides with anthracene cores. All anthracene sulfides studied here were highly fluorescent. Their optical behavior was compared with that of related pyrene bisulfide and tetrasulfides. All sulfides are crystalline compounds and show good chemical stability in condensed phase. In solution, the pyrene derivatives are very stable but the anthracene derivatives suffer a slow photooxidation process under air and ambient light. While the bisulfides of anthracene and pyrene have very different spectroscopic behavior, the tetrasubstituted anthracene and pyrene sulfides exhibit quite a few similarities. Thus, the chromophoric core of the compounds consists of the aromatic core and the sulfur or oxygen atoms, so the variation from alkyl to aryl substituents does not alter the profiles of the absorption and emission spectra. All they show intense fluorescence, but sulfides bearing SCH 2 or OCH 2 groups display higher fluorescence efficiencies than the ones with aryl substituents. In addition, their quenching efficiencies with nitroaromatic compounds of both series are dominated by steric hindrance rather than by electronic factors. Bathochromic shifts in the absorption spectra are well reproduced by TDDFT. Moreover, calculations indicate that the lower energy excitations are of non-ionic type in agreement with experimental results which showed that both absorption and emission spectra are devoid of noticeable solvatochromic effects.

A Mild, Efficient and Highly Selective Oxidation of Sulfides to Sulfoxides Catalyzed by Lewis Acid–Urea–Hydrogen Peroxide Complex at Room Temperature

Alkyl and aryl sulfides were oxidized to the corresponding sulfoxides with urea–hydrogen peroxide (UHP) in the presence of FeCl3 as a Lewis acid catalyst under simple and mild reaction conditions. The protocol is efficient and highly selective and sulfoxides were obtained as the sole oxidation products in high yields at room temperature.

Metal–organic framework MOF-199-catalyzed direct and one-pot synthesis of thiols, sulfides and disulfides from aryl halides in wet polyethylene glycols (PEG 400)

ABSTRACTA highly porous metal–organic frame work Cu3 BTC2 (copper(II)-benzene-1,3,5-tricarboxylate) that is known as MOF-199 was synthesized from the reaction of 1,3,5-benzenetricarboxylic acid and Cu(OAc)2·H2O by a solvothermal method and characterized by several techniques including FT-IR, XRD, EDX and scanning electron microscopy. The MOF-199 used as an efficient catalyst for one-pot synthesis of thiols by domino reactions of aryl halides and thiourea, and subsequently conversion to aryl alkyl sulfides and diaryl disulfides in polyethylene glycols (PEGs). A variety of aryl alkyl sulfides can be obtained in good to excellent yields in a relatively short reaction time and in the presence of the trace amount of catalyst. Also, the catalyst can be separated from the reaction mixture by decanting, and be reused without significant degradation in catalytic activity.

An Efficient Coupling of p‐Quinone Mono‐Imine Ketals and Aryl/Alkyl Thiols: Rapid Synthesis of Biaryl/Aryl–Alkyl Sulfides

We report a fast, efficient, and metal‐free protocol for the synthesis of unsymmetrical biaryl sulfides and aryl–alkyl sulfides (4‐methoxy‐2‐sulfanyl‐phenylcarbamates) under catalytic influence of 2,4‐dinitrobenzoic acid. The reaction proceeded in a regioselective anti‐Michael addition fashion and all the products were obtained within a very short period of time and in good to excellent yields.

Reactivity and Structure Changes of Coal Tar Asphaltene during Slurry-Phase Hydrocracking

Coal tar asphaltene (CT-asp) is one of the important heavy components of coal tar. It has significant influences on the conversion efficiency of slurry-phase hydrocracking. The reactivity and structure changes of CT-asp in a slurry-phase process were investigated. Experimental results showed that the conversion of CT-asp reached 66.5 wt % with a significant decrease of sulfur and oxygen contents as the reaction time increased. The CT-asp obtained from the hydrocracking reaction carried out for different time has been analyzed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and 1H/13C nuclear magnetic resonance. The chemical structural analysis results confirmed that CT-asp was mainly composed of more aromatic rings with oxygen functional groups and possessed a higher aromaticity and shorter aliphatic chains after hydrocracking. Moreover, the effective cracking of carbonyl groups, pyrrolic nitrogen, and alkyl sulfides in CT-asp was found during the slurry-ph...

An efficient silica supported Chitosan@vanadium catalyst for asymmetric sulfoxidation and its application in the synthesis of esomeprazole

A new type of silica supported Chitosan@vanadium complex was used as a highly active heterogeneous catalyst for asymmetric oxidation of aryl alkyl sulfides. With the economic aqueous H2O2 (30%) as the oxidant, the oxidation products were obtained in high yields (up to 95%) with good enantioselectivities (up to 68% ee). It is noted that the marketed drug Nexium (first proton-pump inhibitor, esomeprazole) could be synthesized easily by the newly developed asymmetric sulfoxidation reaction. In addition, the highly active catalyst can be reused five times without losing its catalytic activity.

Acid/Phosphide-Induced Radical Route to Alkyl and Alkenyl Sulfides and Phosphonothioates from Sodium Arylsulfinates in Water.

A newly developed aqueous system with acid and phosphide was introduced in which odorless and stable sodium arylsulfinates can in situ generate arylsulfenyl radicals. These radicals have high reactivity to react with alkynes, alkenes, and H-phosphine oxides for the synthesis of alkyl and alkenyl sulfides and phosphonothioates. The control experiments and quantum calculations are also performed to gain insights into the generation mechanism of arylsulfenyl radicals. Notably, the chemistry is free of thiol odors, organic solvents, and metals.

Pyrite‐hydrocarbon Interaction under Hydrothermal Conditions: an Alternative Origin of H2S and Organic Sulfur Compounds in Sedimentary Environments

AbstractSulfate rocks and organic sulfur from sedimentary organic matter are conventionally assumed as the original sulfur sources for hydrogen sulfide (H2S) in oil and gas reservoirs. However, a few recent experiments preliminarily indicate that the association of pyrite and hydrocarbons may also have implications for H2S generation, in which water effects and natural controls on the evolution of pyrite sulfur into OSCs and H2S have not been evaluated. In this study, laboratory experiments were conducted from 200 to 450°C to investigate chemical interactions between pyrite and hydrocarbons under hydrothermal conditions. Based on the experimental results, preliminary mechanism and geochemical implications were tentatively discussed. Results of the experiments showed that decomposition of pyrite produced H2S and thiophenes at as low as 330°C in the presence of water andn‐pentane. High concentrations of H2S were generated above 450°C under closed pyrolysis conditions no matter whether there is water in the designed experiments. However, much more organic sulfur compounds (OSCs) were formed in the hydrous pyrolysis than in anhydrous pyrolysis. Generally, most of sulfur liberated from pyrite at elevated temperatures was converted to H2S. Water was beneficial to breakdown of pyrite and to decomposition of alkanes into olefins but not essential to formation of large amounts of H2S, given the main hydrogen source derived from hydrocarbons. In addition, cracking of pyrite in the presence of 1‐octene under hydrous conditions was found to proceed at 200°C, producing thiols and alkyl sulfides. Unsaturated hydrocarbons would be more reactive intermediates involved in the breakdown of pyrite than alkanes. The geochemistry of OSCs is actually controlled by various geochemical factors such as thermal maturity and the carbon chain length of the alkanes. This study indicates that the scale of H2S gas generated in deep buried carbonate reservoirs via interactions between pyrite and natural gas should be much smaller than that of thermochemical sulfate reduction (TSR) due to the scarcity of pyrite in carbonate reservoirs and the limited amount of long‐chained hydrocarbons in natural gas. Nevertheless, in some cases, OSCs and/or low contents of H2S found in deep buried reservoirs may be associated with the deposited pyrite‐bearing rock and organic matters (hydrocarbons), which still needs further investigation.

Solvent-free synthesis of alkyl and fluoroalkyl sulfonium salts from sulfides and fluoroalkyl trifluoromethanesulfonates

A series of diaryl(fluoroalkyl)sulfonium salts were synthesized from electron-rich diaryl sulfides and fluoroalkyl trifluoromethanesulfonates under solvent-free conditions. Unlike diaryl sulfides, dialkyl and alkyl(aryl) sulfides reacted with fluoroalkyl trifluoromethanesulfonates (e.g. CF3SO3CH2CF3, CF3SO3CH2CF2H) to provide trialkyl- and aryl(dialkyl)sulfonium trifluoromethanesulfonates in good yields, wherein dialkyl- and alkyl(aryl)(fluoroalkyl)sulfonium salts were formed, respectively, and nucleophilically attacked by a second sulfide to yield the non-fluorinated sulfoniums. The SN2-type reaction could stop at the first step and exclusively afford dialkyl- and alkyl(aryl)(fluoroalkyl)sulfonium salts, which was dramatically dependent upon the structure of sulfides, the nature of fluoroalkyl trifluoromethanesulfonates, the reactant ratio, and/or the reaction temperature. This protocol allows for an efficient and convenient access to a variety of alkyl and fluoroalkyl sulfonium salts.

ChemInform Abstract: Palladium‐Catalyzed ipso‐Borylation of Aryl Sulfides with Diborons.

AbstractInherently reluctant C—S bonds are transferred into C—B bonds in a catalytic Miyaura‐type reaction.

Oxidative Addition of Disulfides, Alkyl Sulfides, and Diphosphides to an Aluminum(I) Center.

The aluminum(I) compound NacNacAl (1) reacts with diphenyl disulfide and diethyl sulfide to form the respective four-coordinate bis(phenyl sulfide) complex NacNacAl(SPh)2 (2) and alkyl thiolate aluminum complex NacNacAlEt(SEt) (3). As well, reaction of 1 with tetraphenyl diphosphine furnishes the bis(diphenyl phosphido) complex NacNacAl(PPh2)2 (4). Production of 3 and 4 are the first examples of C(sp(3))-S and R2P-PR2 activation by a main-group element complex. All three complexes were characterized by multinuclear NMR spectroscopy and X-ray crystal structure analysis. Furthermore, a variable-temperature NMR spectroscopic study was undertaken on 4 to study its dynamic behavior in solution.

ChemInform Abstract: Reactions of HDDA‐Derived Benzynes with Sulfides: Mechanism, Modes, and Three‐Component Reactions.

AbstractThermally generated benzynes react with a range of alkyl sulfides by hexadehydro‐Diels—Alder (HDDA) cycloisomerization.

ChemInform Abstract: Direct α‐Acyloxylation of Organic Sulfides with the Hypervalent (Diacyloxyiodo)benzene/Tetra‐n‐butylammonium Bromide (TBAB) Reagent Combination.

Abstractα‐Acyloxy sulfides are directly synthesized under metal‐free conditions starting from a broad range of readily available alkyl sulfides.

ChemInform Abstract: Trifluorination of Sulfides and Dithioketals Using IF5‐Pyridine‐HF.

AbstractThe stable fluorination reagent is used for the trifluorination of aryl alkyl sulfides with concomitant migration of the arylsulfanyl group.

Palladium-Catalyzed ipso-Borylation of Aryl Sulfides with Diborons

A catalytic Miyaura-type ipso-borylation of aryl sulfides with diboron reagents has been achieved, providing arylboronate esters of synthetic use. The key conditions to transform inherently reluctant C-S bonds into C-B bonds include a palladium-NHC (N-heterocyclic carbene) precatalyst, bis(pinacolato)diboron, and lithium hexamethyldisilazide. This protocol is applicable to a reasonable range of aryl alkyl sulfides. Twofold borylation was observed in the reaction of diphenyl sulfide.

Copper(I) thiocyanate networks with aliphatic sulfide ligands

A total of five new CuSCN-L compounds with alkyl sulfide ligands, L=methyl sulfide (Me2S), ethyl sulfide (Et2S), isopropyl sulfide (Pri2S) or tetrahydrothiophene (THT) have been prepared and characterized. X-ray crystal structures for four of the compounds were obtained. Two compounds were collected from solutions of CuSCN in Me2S: {[Cu(SCN)(Me2S)2]}n (1a) in the form of colorless blocks and (CuSCN)(Me2S) (1b) as a white powder. Neat mixtures of CuSCN in the other alkyl sulfide ligands yielded only one product each: {[Cu(SCN)(Et2S)]}n (2); {[Cu(SCN)(Pri2S)]}n (3); and {[Cu(SCN)(THT)2]}n (4). Crystals of 2 and 4 underwent destructive phase changes at lower temperatures. Two networks types were observed: 1:2 decorated 1-D chains (1a and 4) and 1:2 decorated 1-D ladders (2 and 3). Further network formation through bridging of the organic sulfide ligands was not observed.

Reactions of HDDA-Derived Benzynes with Sulfides: Mechanism, Modes, and Three-Component Reactions.

We report here reactions of alkyl sulfides with benzynes thermally generated by the hexadehydro-Diels-Alder (HDDA) cycloisomerization. The initially produced 1,3-betaine (o-sulfonium/aryl carbanion) undergoes intramolecular proton transfer to generate a more stable S-aryl sulfur ylide. This can react in various manners, including engaging weak acids (HA) in the reaction medium. This can produce transient ion pairs ArSR2(+)A(-) that proceed to the products ArSR + RA. When cyclic sulfides are used, A(-) opens the ring and is incorporated into the product, an outcome that constitutes a versatile, three-component coupling process.

Manganese- and Lanthanide-Based 1D Chiral Coordination Polymers as an Enantioselective Catalyst for Sulfoxidation.

The chiral 1D-coordination polymers (CP) {[Ln2(MnLCl)2(NO3)2(dmf)6(H2O)2]·xH2O}n [Ln = Pr (1), Nd (2), Sm (3), and Gd (4)] were synthesized by the reaction of N,N'-bis(4-carboxysalicylidene)cyclohexanediamine (H4L) with [MnCl2·4(H2O)] and [Ln(NO3)3·x(H2O)] in the presence of dmf/pyridine at 90 °C. The polymers consist of manganese-salen-based moieties having carboxylate linkers connected to rare earth atoms in a 1D-chain structure. The polymers are very easily accessible. A one-step synthesis for the ligand and a second step for the preparation of the 1D coordination polymers starting from commercially available material are needed. The solid state structures of 1-4 were established by single-crystal X-ray diffraction. Compounds 1-4 were investigated as heterogeneous catalysts for the sulfoxidation reaction of various alkyl and aryl sulfides. The influence of various solvents and oxidizing agents on the catalytic reaction was examined. It was found that the catalysts were active for more than one reaction cycle without significant loss of activity. For phenylsulfide with 1 mol % of the catalyst 4, a maximum conversion 100% and a chemoselectivity 88% were observed.