Sulfur Reagents Research Articles

Research Progress on the Construction of C—S Bond Using Aryl Disulfides as Radical Sulfur Reagents

Research Progress on the Construction of C—S Bond Using Aryl Disulfides as Radical Sulfur Reagents

One-pot synthesis of thioethers from indoles and p-quinone methides using thiourea as a sulfur source.

Thiourea is an inexpensive and user friendly sulfur reagent that acts as a sulfur source. A simple and efficient protocol has been developed to access thioethers by reacting indoles with p-quinone methides using thiourea as the sulfur source. In our experiments, the reaction apparently proceeded through an S-(3-indolyl)isothiuronium iodide intermediate and subsequent generation of indolethiol that attacked the 1,6 position of p-quinone methides to give desired thioethers in good to excellent yields.

Role of carboxylates in the phase determination of metal sulfide nanoparticles.

Techniques are well established for the control of nanoparticle shape and size in colloidal synthesis, but very little is understood about precursor interactions and their effects on the resultant crystalline phase. Here we show that oleate, a surface stabilizing ligand that is ubiquitous in nanocrystal synthesis, plays a large role in the mechanism of phase selection of various metal sulfide nanoparticles when thiourea is used as the sulfur source. Gas and solid-phase FTIR, 13C, and 1H NMR studies revealed that oleate and thiourea interact to produce oleamide which promotes the isomeric shift of thiourea into ammonium thiocyanate, a less reactive sulfur reagent. Because of these sulfur sequestering reactions, sulfur deficient and metastable nanoparticles are produced, a trend seen across four different metals: copper, iron, nickel, and cobalt. At low carboxylate concentrations, powder XRD indicated that the following phases formed: covellite (CuS); vaesite (NiS2); smythite (FeS1.3), greigite (FeS1.3), marcasite (FeS2) and pyrite (FeS2); and cattierite (CoS2). At high sodium oleate concentration, these phases formed: digenite (CuS0.55), nickel sulfide (NiS), pyrrhotite (FeS1.1), and jaipurite (CoS).

Synthesis of some new thiophene-based compounds and evaluations of their cytotoxic activities

ABSTRACT. A series of new thiophene derivatives was prepared through nucleophilic substitution reactions of the precursor N-(4-substituted-phenyl)-5-(2-chloroacetamido)-4-cyano-3-methylthiophene-2-‎carboxamides 4a and 4b with different sulfur and/or nitrogen nucleophilic reagents (namely; mercaptoacetic acid, 2-mercaptobenzothiazole, 5-(phenylamino)-1,3,4-thiadiazole-2-thiol, 2-mercapto-4,6-dimethylnicotinonitrile, 3-arylazo-4-mercapto-4-(phenylamino)-but-3-en-one derivatives, ammonium thiocyanate, piperidine and/or morpholine). The structures of the prepared thiophene compounds were characterized by spectral analysis. Their cytotoxicity was evaluated against two human cancer cell lines (HepG2 and MCF-7) and indicated promising results. Pretreatment of HepG2 cells with the tested compound 4b sensitized the cells to the cytotoxicity of sorafenib, leading to a significant decrease in the IC50 from 3.9 to 0.5 µM.
 
 KEY WORDS: N-(Thienyl)-2-chloroacetamide, Bis-thiophene, Thieno[2,3-d]pyrimidine, Ammonium thiocyanate, Cytotoxicity
 
 Bull. Chem. Soc. Ethiop. 2023, 37(2), 373-389. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i2.10

Postsynthetic Thiol-Induced Reshaping of Copper Sulfide Nanoparticles

Nanoparticles of copper sulfide, including roxbyite Cu1.8S, are important materials for many applications, and they also serve as versatile templates for cation exchange reactions that transform them into derivative metal sulfide compounds and complex heterostructures. The sizes and shapes of roxbyite nanoparticles are generally determined during synthesis, and their morphologies are retained during postsynthetic modifications such as cation exchange. Here, we demonstrate postsynthetic morphological modification of roxbyite nanoparticles by treating them with 1-dodecanethiol (1-DDT) and tert-dodecanethiol (t-DDT) at temperatures ranging from 90 to 160 °C. These thiols, which are typically used as ligands and/or sulfur reagents in nanoparticle synthesis, induce morphological reshaping while maintaining composition, crystal structure, and particle volume. For example, 56 nm × 21 nm roxbyite nanorods transform to 32 nm spherical particles in the presence of 1-DDT at 130 °C for two or more hours. The nanorods progressively decrease in length and increase in width, forming a series of ellipsoids having tunable aspect ratios at intermediate time points. Control experiments point to a single-crystal-to-single-crystal pathway that involves material diffusion and migration, which can be accelerated by increasing the density of cation vacancies in the nanoparticles. Because of this pathway, the thiol-induced morphology changes are selective to the copper sulfide regions of heterostructured nanorods containing roxbyite and ZnS, Co9S8, or CuInS2 made using partial cation exchange reactions, providing access to a library of derivative nanoparticles having otherwise inaccessible morphologies.

Utilisation of bis-chloroacetamide derivative in the synthesis of new biologically active sulfide compounds

4-Aminobenzohydrazide (1) undergoes chloroacetylation twice, at the primary amine and hydrazide-NH2 functional groups. The conforming bis-chloroacetamide derivative 3 was reacted with different sulfur reagents (namely, 2-mercaptobenzothiazole, 6-amino-2-mercaptopyrimidin-4-ol, and 2-mercapto-4,6-dimethyl-nicotinonitrile) to give new bis-sulfide compounds 5, 7 and 9, respectively. The newly synthesised bis-chloroacetamide and corresponding sulfides were screened for anti-microbial and antioxidant potential. The sulfide derivative 7 exhibited the most potent activity against Staphylococcus aureus and Pseudomonas aeruginosa. It shows inhibition activities of 83.4% and 78.8%, respectively. Moreover, the sulfide derivative 7 showed the highest antioxidant activity with an inhibition ratio of 85.9%, which is close to L-ascorbic acid.

Chemo‐ and Regioselective C−H Sulfidation of Indoles for the Synthesis of Tolylthioindoles under Metal‐Free Conditions

AbstractControllable chemoselectivity and regioselectivity synthesis of 3‐sulfinylated, 3‐sulfenylated and 2‐sulfonylated indoles via direct C−H functionalization are realized under metal‐free conditions. In particular, the synthesis of 3‐arylsulfinylindoles in high yields from a sulfone substrate in water without additives is reported. The process displays excellent functional groups compatibility. p‐Toluenesulfonyl cyanide (TsCN) possesses a hexavalent sulfonyl group, as an odorless and easy‐to‐handle solid, which has been used as a new sulfur reagent through the cleavage of S−C and S=O bonds in our work.magnified image

Cu-Catalyzed Three-Component Cascade Synthesis of 1,3-Benzothiazines from ortho-Aminohydrazones and Bromodifluoroacetamides.

An efficient and convenient synthesis of benzo[d][1,3]thiazine has been developed by employing a copper-catalyzed transformation of readily available ketone-derived hydrazones with elemental sulfur and bromodifluoroalkylative reagents. The strategy involves an S8-catalyzed selective triple-cleavage of bromodifluoroacetamides, which acts as a C1 synthon at the 2-position of benzo[d][1,3]thiazine. A mechanism proceeding through a Cu-carbene intermediate is proposed for the C-S bond formation.

Chiral Chalcogenide-Catalyzed Enantioselective Electrophilic Hydrothiolation of Alkenes.

A new strategy for the construction of chiral sulfides by catalytic enantioselective hydrothiolation of alkenes via an electrophilic pathway has been developed. Using this strategy, cyclic and acyclic unactivated alkenes efficiently afforded various chiral products in the presence of electrophilic sulfur reagents and silanes through chiral chalcogenide catalysis. The obtained products were easily transformed into other types of valuable chiral sulfur-containing compounds. Mechanistic studies revealed that the superior construction of chiral thiiranium ion intermediate is the key to achieving such a transformation.

Base‐catalyzed Sulfurative Condensation of 2‐Oxoindoles to Isoindigos Using Elemental Sulfur

AbstractHerein, the base‐catalyzed formation of isoindigos is described through the cascade reaction of 2‐oxoindoles with elemental sulfur (S8) serving as an environmentally friendly and cheap sulfurating reagent. Readily available organic amines, especially 1,4‐diazabicyclo[2.2.2]octane (DABCO), exhibit excellent activity for this protocol, thus simply and efficiently providing structurally diverse isoindigos in moderate to high yields with a broad substrate scope. A plausible mechanism involving the generation of 3‐thioisatin intermediates and the subsequent self‐condensation, was proposed on the basis of mechanistic studies. The practicality of the methodology was further demonstrated by the synthesis of gram‐scalable drug molecules and value‐added spirothiopyrans.

Sonochemical synthesis and characterization of CuInS2 nanostructures using new sulfur precursor and their application as photocatalyst for degradation of organic pollutants under simulated sunlight

In this research, we investigated the photocatalytic activity of CuInS2 nanoparticles in visible light during the decomposition of three toxic dyes (Eriochrome Black T, Rhodamine B, and Erythrosine). The CuInS2 nanostructures were synthesized by a rapid and simple sonochemical method using dithiooxamide as a sulfur reagent and various capping agents, including SDS, CTAB, and PVP, were applied to achieve a pure structure with fine morphology. The flower-like structure was observed through FESEM images, implying different capping agents and fabrication had a considerable influence on the morphology of samples. The suitable bandgap of CuInS2 (1.53 eV) was obtained from DRS analysis and resulted in higher photodegradation efficiency. The fabricated CuInS2 revealed better photodegradation efficiency (74.8%) to the anionic dyes than cationic dye. A possible photodegradation mechanism was suggested based on scavenger tests of active species.

C4-Sulfenylation of 4-iodine-1H-pyrazole-5-amine with arylsulfonyl hydrazide in water

A C4-sulfenylation of 4-iodine-1H-pyrazole-5-amine with arylsulfonyl hydrazide in water was developed. A series of C4-sulfenylated products were obtained in moderate to excellent yields. This protocol features green reaction conditions (metal-free, water as the solvent, in the air), odorless and easily available sulfur reagent, broad substrate scope as well as gram-scale synthesis. Mechanistic studies showed that the in-situ formation of iodine from 4-iodine-1H-pyrazole-5-amine in the presence of aryl sulfonyl hydrazides was the key to the C4-Sulfenylation.

New Electrophilic Sulfur Reagent and its Application in a Ni-Catalyzed syn-Carbosulfenylation of Alkenes

New Electrophilic Sulfur Reagent and its Application in a Ni-Catalyzed syn-Carbosulfenylation of Alkenes

Copper-Catalyzed Direct C(sp2)–H Sulfuration of Aryl Alkenes by Using Tetraalkylthiuram Disulfides for the Synthesis of Alkenyl Dithiocarbamates

AbstractCopper-catalyzed direct C(sp2)–H sulfuration of aryl alkenes by using tetraalkylthiuram disulfides as sulfuration reagents has been developed. The reaction provides an efficient method for the synthesis of a variety of alkenyl dithiocarbamates, which are important structure motifs widely applied in materials, pharmaceuticals, and agrochemicals.

Ynamide-Mediated Thioamide and Primary Thioamide Syntheses.

Environmentally friendly ynamide-mediated thioamidation of monothiocarboxylic acids with amines or ammonium hydroxide for the syntheses of thioamides and primary thioamides is described. Simple and mild reaction conditions enable the reaction to tolerate a wide variety of functional groups such as hydroxyl group, ester, tertiary amine, ketone, and amide moieties. Readily available NaSH served as the sulfur source, avoiding the use of toxic, expensive, and malodorous organic sulfur reagents and making this strategy environmentally friendly and practical. Importantly, the stereochemical integrity of α-chiral monothiocarboxylic acids was maintained during the activation step and subsequent aminolysis process, thus offering a racemization-free strategy for peptide C-terminal modification. Furthermore, a number of thioamide-modified drugs were prepared in good yields by using this protocol and the synthesized primary thioamides were transformed into backbone thiazolyl modified peptides.

Transition-Metal-Free Radical-Triggered Hydrosulfonylation and Disulfonylation Reaction of Substituted Maleimides with Sulfonyl Hydrazides.

A convenient and practical hydrosulfonylation and disulfonylation of substituted maleimides was realized using sulfonyl hydrazides as the sulfur reagent and tert-butyl hydroperoxide as the oxidant. The advantages of the reactions include mild and transition-metal-free reaction conditions, good functional group tolerance, and readily available starting materials. The radical species-induced pathway is also demonstrated by mechanistic studies.

A comparative study on the physicochemical properties, reactivity and long-term performance of sulfidized nanoscale zerovalent iron synthesized with different kinds of sulfur precursors and procedures in simulated groundwater

There are plentiful ways to synthesize sulfidized nanoscale zerovalent iron (S-nZVI), and this study investigated the influence of sulfur reagents (Na2S, Na2S2O3, Na2S2O4) and sulfidation sequence (co-sulfidation and post-sulfidation method) on the physicochemical properties, reactivity, and long-term performance of S-nZVI in simulated groundwater. The results suggested that the co-sulfidized nZVI (S-nZVIco) has higher reactivity (∼2-fold) than S-nZVIpost due to the stronger electron transfer capacity, deriving from the higher content of Fe0 and reductive sulfur species. However, during aging, the reactivity of S-nZVIco would be lost more rapidly than S-nZVIpost, due to the faster corrosion of Fe0 and more oxidation of reductive sulfur species. S-nZVIpost has the superior long-term performance with the degradation rate of trichloroethylene (TCE) remained at 30%∼60% even after 90 d of aging. Sulfur precursors can control the selectivity of S-nZVI by affecting the sulfur speciation on the particle surface. The proportion of reductive sulfur species on S-nZVIpost synthesized by Na2S was higher than S-nZVIpost synthesized by Na2S2O3 or Na2S2O4, resulting in a higher selectivity of the former S-nZVIpost than the latter S-nZVIpost. In addition, sulfidation procedures and sulfur precursors did not affect the degradation pathway of TCE. Nevertheless, the degradation product distribution can be affected by the different physicochemical transformation of various types of S-nZVI with the aging time. These results indicated that sulfur reagents and sulfidation procedures have crucial effects on the reactivity and long-term performance of S-nZVI, which can be designed for the specific application scenarios.

One‐Pot Synthesis of Thiocarbamates

AbstractAn efficient isocyanide‐based synthesis of S‐thiocarbamates was discovered and thoroughly investigated. The new reaction protocol is a one‐pot procedure and allows the direct conversion of N‐formamides into thiocarbamates by initial dehydration with p‐toluene sulfonyl chloride to the respective isocyanide and subsequent addition of a sulfoxide component. Contrary to recent literature, which also uses isocyanides as starting material, but with other sulfur reagents than sulfoxides, in this protocol, no isolation and purification of the isocyanide component is necessary, thus significantly decreasing the environmental impact and increasing the efficiency of the synthesis. The new protocol was applied to synthesize a library of sixteen thiocarbamates, applying four N‐formamides and four commercially available sulfoxides. Furthermore, experiments were conducted to investigate the reaction mechanism. Finally, four norbornene‐based thiocarbamate monomers were prepared and applied in controlled ring‐opening metathesis polymerization (ROMP) reactions. The polymers were characterized by size‐exclusion chromatography (SEC) and their properties were investigated utilizing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Calcium sulfide-organosilicon complex for sustained release of H2S in strongly acidic wastewater: Synthesis, mechanism and efficiency

Sulfide precipitation is an efficient method to remove Cu(II) and As(III) from strongly acidic wastewater, but the instantaneous release of H2S from traditional sulfuration reagents causes serious H2S pollution. Moreover, the obtained precipitates are mixtures of CuS and As2S3, leading to difficulties in resource recovery. In this study, a calcium sulfide-organosilicon complex (CaS-OSCS), in which CaS was coated into a matrix of {[O1.5Si(CH2)3NH]CS}n (OSCS) via the coordination bonding, was developed. OSCS, as a matrix of CaS-OSCS, can ensure the sustained and stable release of H2S under strongly acidic conditions owing to its low swelling (1.75% swelling ratio) and excellent acid resistance. The release longevity of H2S from CaS-OSCS extended from 5 min up to 50 min compared with that from CaS because the hydrophobic OSCS prevented solution diffusing to the pores of CaS-OSCS and thus slowed down the hydrolysis of CaS in pores. 99% of Cu(II)/As(III) was precipitated without H2S escape, and the dosage of sulfuration reagents was reduced by 30%. In addition, CaS-OSCS improved the selective separation of copper from wastewater, and a separation factor between Cu(II) and As(III) reached 2376. This study provides a potential approach for the elimination of H2S pollution and selective recovery of copper.

Arsenic Removal and Recovery of Germanium and Tungsten in Toxic Coal Fly Ash from Lignite by Vacuum Distillation with a Sulfurizing Reagent.

Every year, billions of tons of lignite are burnt to generate electricity, meanwhile generating large amounts of coal fly ash (CFA) that is regarded as an industrial waste. During lignite combustion, arsenic and scarce metals are simultaneously volatilized in the form of oxide into CFA. This study proposed an effective vacuum distillation method to remove As and recover Ge and W from CFA. The feasibility of separating As and recycling Ge and W from CFA was verified by the theoretical analysis. The experimental result indicated that the removal ratio of As was 96 ± 1% and the contents of Ge and W reached 0.75 ± 0.023 and 0.24 ± 0.016 wt % in the residue, which were enriched 17.2 and 1.2 times, respectively, at a temperature of 550 °C, with 50 wt % sulfurizing agent added under pressure of 1 Pa and 240 min of heating. For the condensed product, chemical species As2S3 and As4S4 were detected by X-ray photoelectron spectroscopy analysis. For Ge and W in the residue, GeOx (x < 2), GeS, WOx (x < 3), and WS2 were the main chemical species. The potential mechanism involved in the release of arsenic from CFA, vacuum sulfurization, evaporation, and condensation was proposed. The kinetic analysis indicated that the apparent activation energy (Eα) was 31.24 kJ mol-1. Those results encourage further exploration of vacuum separation technology to environmentally friendly recycle CFA.