Bunte Salts Research Articles

Synthesis of Alkanethiolate-Capped Metal Nanoparticles Using Alkyl Thiosulfate Ligand Precursors: A Method to Generate Promising Reagents for Selective Catalysis.

Evaluation of metal nanoparticle catalysts functionalized with well-defined thiolate ligands can be potentially important because such systems can provide a spatial control in the reactivity and selectivity of catalysts. A synthetic method utilizing Bunte salts (sodium S-alkylthiosulfates) allows the formation of metal nanoparticles (Au, Ag, Pd, Pt, and Ir) capped with alkanethiolate ligands. The catalysis studies on Pd nanoparticles show a strong correlation between the surface ligand structure/composition and the catalytic activity and selectivity for the hydrogenation/isomerization of alkenes, dienes, trienes, and allylic alcohols. The high selectivity of Pd nanoparticles is driven by the controlled electronic properties of the Pd surface limiting the formation of Pd–alkene adducts (or intermediates) necessary for (additional) hydrogenation. The synthesis of water soluble Pd nanoparticles using ω-carboxylate-S-alkanethiosulfate salts is successfully achieved and these Pd nanoparticles are examined for the hydrogenation of various unsaturated compounds in both homogeneous and heterogeneous environments. Alkanethiolate-capped Pt nanoparticles are also successfully synthesized and further investigated for the hydrogenation of various alkynes to understand their geometric and electronic surface properties. The high catalytic activity of activated terminal alkynes, but the significantly low activity of internal alkynes and unactivated terminal alkynes, are observed for Pt nanoparticles.

A Novel Method for the Direct Synthesis of Symmetrical and Unsymmetrical Sulfides and Disulfides from Aryl Halides and Ethyl Potassium Xanthogenate

An efficient and new method for the synthesis of disulfides and sulfides via the reaction of aryl halides with ethyl potassium xanthogenate in the presence of MOF-199 is described. O-Ethyl-S-aryl ­carbonodithioate has a key role as an intermediate in this procedure; it was converted into symmetrical diaryl disulfides in DMF. Additionally, this could be applied to the synthesis of unsymmetrical aryl alkyl(aryl′) disulfides by the reaction with S-alkyl(aryl) sulfurothioates (Bunte salts) as well as unsymmetrical aryl alkyl(aryl′) sulfides in DMSO.

A thiol-free synthesis of alkynyl chalcogenides by the copper-catalyzed C–X (X = S, Se) cross-coupling of alkynyl carboxylic acids with Bunte salts

A thiol-free protocol is developed for the copper-catalyzed C–X (X = S, Se) cross-coupling of alkynyl carboxylic acids with Bunte salts.

Transition-metal-free KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins using Bunte salts.

An efficient and eco-friendly protocol for the KI-catalyzed regioselective sulfenylation of 4-anilinocoumarins with Bunte salts was established. The reaction worked smoothly under metal-free conditions and afforded a wide range of sulfenylated 4-anilinocoumarins with potential bioactivity in moderate to excellent yields. This method would expand the still limited scope of synthesis methods for C-S bond formation using Bunte salts.

Glycosyl Bunte Salts: A Class of Intermediates for Sugar Chemistry.

S-Glycosyl thiosulfates have been discovered as a new class of synthetic intermediates in sugar chemistry, named "glycosyl Bunte salts" after 19th-century German chemist, Hans Bunte. The synthesis was achieved by direct condensation of unprotected sugars and sodium thiosulfate using a formamidine-type dehydrating agent in water-acetonitrile mixed solvent. The application of glycosyl Bunte salts is demonstrated with transformation reactions into other glycosyl compounds such as a 1-thio sugar, a glycosyl disulfide, a 1,6-anhydro sugar, and an O-glycoside.

A new imidazoline-containing Bunte salt: synthesis, molecular and electronic structure

Abstract S-[(4,5-dihydro-1H-imidazol-2-yl)methyl]sulfothioate, a new imidazoline-containing Bunte salt 4 was prepared by reacting 2-chloromethylimidazoline 3 with sodium thiosulfate in aqueous solution at room temperature. The mechanism of the concerted SN2 reaction pathway was studied by means of quantum chemical calculations at the B3LYP/6-31G** level of theory. The molecular structure of compound 4 incorporating a formal amidine moiety was confirmed by single crystal X-ray diffraction analysis, while its electronic structure was studied using quantum chemical calculations at the MP2/6-311++G** level of theory.

Aqueous Reaction of Alcohols, Organohalides, and Odorless Sodium Thiosulfate under Transition-Metal-Free Conditions: Synthesis of Unsymmetrical Aryl Sulfides via Dual C-S Bond Formation.

A transition-metal-free process for the synthesis of unsymmetrical aryl sulfides via dual C-S bond formation by a one-pot three-component reaction of alcohols, organohalides, and odorless sodium thiosulfate in water has been developed. In addition, the aryl sulfides could also be prepared by the reaction of the corresponding alcohols and Bunte salts under the identical conditions. This protocol provides a green and efficient manner for the construction of various unsymmetrical aryl sulfides.

Physicochemical properties of keratin extracted from wool by various methods

Keratin from wool fibers was extracted with different extraction methods, for example oxidation, reduction, sulfitolysis, and superheated water hydrolysis. Different samples of extracted keratin were characterized by molecular weight determination, FT-IR and NIR spectroscopy, amino acid analysis, and thermal behavior. While using oxidation, reduction, and sulfitolysis, only the cleavage of disulfide bonds takes place; keratin hydrolysis leads to the breaking of peptide bonds with the formation of low molecular weight proteins and peptides. In the FT-IR spectra of keratoses, the formation of cysteic acid appears, as well as the formation of Bunte salts (–S–SO3–) after the cleavage of disulfide bonds by sulfitolysis. The amino acid composition confirms the transformation of amino acid cystine, which is totally converted into cysteic acid following oxidative extraction and almost completely destroyed during superheated water hydrolysis. Thermal behavior shows that keratoses, which are characterized by stronger ionic interaction and higher molecular weight, are the most temperature stable keratin, while hydrolyzed wool shows a poor thermal stability.

NaI-Mediated Acetamidosulfenylation of Alkenes with Bunte Salts as Thiolating Reagent Leading to β-Acetamido Sulfides

A direct and efficient method for the acetamidosulfenylation reaction of alkenes was developed, in which NaI was used as a catalyst, DMSO as the oxidant, nitriles as both the solvent and nucleophiles and stable, readily available Bunte salts as thiolating reagents. The reactions were carried out under mild conditions generating β-acetamido sulfides in good yields. Moreover, the reaction can be performed when alcohols are used as nucleophiles providing the corresponding β-alkoxysulfides in moderate yields, respectively.

Benzothiazoline Converts SO2 to Sulfuric Acid en Route to Benzothiazole

By a new sustainable strategy, sulfur dioxide (SO2) was converted at room temperature into sulfuric acid by taking advantage of the spontaneous aerial oxidation of benzothiazoline into benzothiazole. 2-(4-Methoxyphenyl)benzothiazoline (HL) was reacted with SO2 at room temperature, and the adduct upon reaction with aerial oxygen produced 2-(4-methoxyphenyl)benzothiazolium bisulfate. The same strategy was applied on [CdL2] and [ZnL2] and found to work better than neat benzothiazoline. Bunte salt, S-(2-((pyridin-1-ium-2-ylmethyl)amino)phenyl) thiosulfate, was obtained upon reacting SO2 with 2-(pyridin-2-yl)-2,3-dihydrobenzothiazole which is an important clue for the intermediates involved in the S-oxygenation of SO2 bound on electron rich centers. This sustainable route offers a new avenue of utilizing the suicidal reaction of benzothiazoline into benzothiazole in the activation of SO2 with the help of aerial oxygen.

ChemInform Abstract: Catalytic Synthesis of 3‐Thioindoles Using Bunte Salts as Sulfur Sources under Metal‐Free Conditions.

AbstractThe title protocol is advantageous with respect to the use of odorless and stable Bunte salts as sulfenylating agents and iodine as non metallic catalyst.

Catalytic Synthesis of 3-Thioindoles Using Bunte Salts as Sulfur Sources under Metal-Free Conditions.

An efficient catalytic method for the synthesis of 3-thioindoles has been successfully developed, which uses odorless, stable, readily available crystalline Bunte salts as the sulfenylating agents, iodine as nonmetallic catalyst, and DMSO as both the oxidant and solvent. This method is practical and environmentally benign in terms of sulfur sources, catalyst, and solvent. The catalytic reaction is selective at the C3 position of indoles and compatible with a wide range of substrates, giving the desired products in good to excellent yields.

A tetra-n-butylammonium iodide mediated reaction of indoles with Bunte salts: efficient 3-sulfenylation of indoles under metal-free and oxidant-free conditions.

A highly efficient tetra-n-butylammonium iodide (TBAI) triggered procedure for 3-sulfenylation of indoles with Bunte salts is demonstrated. This protocol provides a simple strategy to prepare 3-alkylthioindoles and 3-arylthioindoles from the corresponding indoles under metal-free and oxidant-free conditions.

ChemInform Abstract: Deep Eutectic Mixture Catalyzed the Synthesis of Disulfides Using Bunte Salts as Thiol Surrogates.

AbstractAn eutectic mixture of choline chloride and toluenesulfonic acid is used for the synthesis of disulfides from Bunte salts in the presence of an oxidant.

Subnanometer Control of Mean Core Size during Mesofluidic Synthesis of Small (D(core) < 10 nm) Water-Soluble, Ligand-Stabilized Gold Nanoparticles.

A convenient, single-step synthesis is reported that produces ligand-stabilized, water-soluble gold nanoparticles (AuNPs) with subnanometer-level precision of the mean core diameter over a range of 2-9 nm for a series of desired surface chemistries. The synthesis involves the reduction of a Au(III) species with sodium borohydride in the presence of a functionalized alkyl thiosulfate (Bunte salt) to yield thiolate-protected AuNPs. A key advantage of this synthesis is that simply adjusting the pH of the gold salt solution leads to control over the AuNP core size. The speciation of Au(III), and therefore the kinetics for its reduction and the core size produced, depends upon pH. The use of pH as the sole variable to control core size is a more reliable and convenient method than traditional approaches that rely on adjusting the concentrations and ratios of ligand, metal salt, and reducing agent. The average core size increased as the pH was raised for each ligand studied. Because the influence of pH was different for each of the ligands, working curves were plotted for each ligand to identify conditions to synthesize particles with specific, targeted core diameters. Using this approach, reaction conditions can be rapidly optimized using a combination of a mesofluidic reactor and small-angle X-ray scattering (SAXS) size analysis. The use of the mesofluidic reactor was needed to ensure fast mixing given the rapid kinetics for core formation. Using the reactor, it is possible to obtain reproducible sizes across multiple syntheses (<1-2% core size variation) and subnanometer control of the mean core dimensions. The synthetic method demonstrated here provides an attractive alternative to two-step syntheses involving ligand exchange because it is more efficient and eliminates the possibility of nanoparticle core size changes during exchange steps. This approach enables the development of "size ladders" of particles with the same surface chemistry for investigations of structure-function relationships.

Imidazole Promoted Highly Efficient Large-Scale Thiol-Free Synthesis of Symmetrical Disulfides in Aqueous Media

GRAPHICAL ABSTRACT

ChemInform Abstract: An Odorless Thia‐Michael Addition Using Bunte Salts as Thiol Surrogates.

AbstractThe synthesis of various β‐sulfido carbonyl compounds via hydrolysis of Bunte salts is described.

Deep Eutectic Mixture Catalysed the Synthesis of Disulfides Using Bunte Salts as Thiol Surrogates

Bunte salts, easily prepared from odourless sodium thiosulfates and various alkyl and aryl halides, acted as thiol surrogates for preparation of disulfides in the presence of hydrogen peroxide and a Brønsted-acidic deep eutectic mixture. The reaction proceeded smoothly to give the corresponding disulfide products in moderate to good yields, leaving odourless sodium bisulfite and water as the by-products. Moreover, this catalytic system could be readily recovered and reused several times without significant loss in activity.

An odorless thia-Michael addition using Bunte salts as thiol surrogates

An efficient thia-Michael addition using odorless, easy to synthesis and handle Bunte salts as thiol surrogates is introduced.

An efficient, one-pot synthesis of N-isatinylmethylthioacetic acid and its derivatives as potential anticancer agents

A convenient, one-pot synthesis of N-isatinylmethylthioacetic acid and several of its derivatives, as potential anticancer agents, by reactions of N-(hydroxymethyl)isatins with Bunte salts in TFA is described. The reactions involve attack of these salts on the S(II) atom by C-electrophilic species generated from hydroxy derivatives.