Oxidation of Thiols Using K 2 S 2 O 8 in Ionic Liquid

A green, straightforward, and novel method for oxidation of thiols to the corresponding disulfides is reported using K ₂ S ₂ O₈ in the ionic liquid 1-butyl-3-methylimidazolium bromide [(bmim)Br] at 65–70°C. The corresponding disulfides were obtained in excellent yield and short reaction time.     

Fe(HSO4)3 and Fe(HSO4)3/DMSO as Efficient,Heterogeneous, and Reusable Catalyst Systems for the Oxidative Coupling of Thiols

Fe(HSO₄)₃ has been used as a heterogeneous, efficient, and recyclable catalyst in ethanol for the selective oxidation of thiols to their corresponding disulfides. The same results were obtained under identical conditions using catalytic amounts of Fe(HSO₄)₃ in the presence of DMSO. Different types of aliphatic, aromatic, and heteroaromatic thiols have been used in the reaction, and in all cases the products were obtained in good to excellent yields.     

Visible-light-mediated facile synthesis of disulfides using reusable TiO2/MoS2 nanocomposite photocatalyst

A nontoxic and inexpensive TiO₂/MoS₂ nanocomposite was prepared and employed as an efficient photocatalyst for the synthesis of symmetrical disulfides under visible light irradiation at room temperature. Both aryl and alkyl thiols survived the reaction conditions, affording the corresponding disulfides in good to excellent yields. The photocatalyst could be easily recovered by simple centrifugation and filtration and reused several times without significant loss in its activity.     

A Convenient Method for the Aerobic Oxidation of Thiols to Disulfides

Thiols are oxidized to the corresponding disulfides using K⁺/CH ₃ CN system under ambient conditions in the presence of air. This system provides a convenient, rapid, and efficient aerobic oxidative for the syntheses of symmetrical disulfides.     

An Efficient and Selective Oxidation of Sulfides and Thiols with Silica-Supported 1,1,3,3-Tetramethylguanidine/Br2 Complex

Silica-supported 1,1,3,3-tetramethylguanidine/Br₂ complex is an efficient reagent for the selective oxidation of aliphatic and aromatic sulfides to the corresponding sulfoxides and the oxidative coupling of thiols to disulfides in aqueous solution at room temperature in a short reaction time.     

Oxidation of thiols to disulfides using H2O2 catalyzed by recyclable chromic potassium sulphate at room temperature

Chromic potassium sulphate is found to be an efficient and recyclable catalyst for the selective oxidation of thiols to disulfides. The reaction was carried out in 60% methanol (v/v) using 30% H₂O₂ at room temperature. Cr(III) forms a complex with thiol which was then oxidized by H₂O₂ to produce disulfide in excellent yield after a simple workup procedure.     

Mn(III) complex supported on Fe3O4 nanoparticles: magnetically separable nanocatalyst for selective oxidation of thiols to disulfides

A manganese(III) complex, [Mn(phox)₂(CH₃OH)₂]ClO₄ (phox?=?2-(2′-hydroxyphenyl)oxazoline), was immobilized on silica-coated magnetic Fe₃O₄ nanoparticles through the amino propyl linkage using a grafting process in dichloromethane. The resulting Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticles are used as efficient and recyclable catalysts for selective oxidation of thiols to disulfides using urea-hydrogen peroxide as the oxidant. The nanocatalyst was recycled several times. Leaching and recycling experiments revealed that the nanocatalyst can be recovered, recycled, and reused more than five times, without the loss of catalytic activity and magnetic properties. The recycling of the nanocatalyst in six consecutive runs afforded a total turnover number of more than 10,000. The heterogeneous Fe₃O₄@SiO₂–NH₂@Mn(III) nanoparticle shows more selectivity for the formation of disulfides in comparison with the homogeneous manganese complex.     

BiCl3 Catalyzed Thiolyzation Reaction of 1,2-Epoxides with Diaryl Disulfides in the Presence of Zinc Powder and Ionic Liquid

A new and efficient method has been developed for the regio- and chemoselective synthesis of β -hydroxysulfides with the ring-opening reaction of 1,2-epoxides by diaryl disulfides and zinc powder in the presence of a catalytic amount of BiCl ₃ in molten tetrabutyl phosphonium bromide as an ionic liquid.     

Rhodium-catalyzed thiophosphinylation and phosphinylation reactions of disulfides and diselenides

Alkyl and aryl dithiophosphinates were synthesized by the reaction of disulfides with biphosphine disulfides in the presence of RhH(PPh₃)₄ and 1,2-diphenylphosphinoethane (dppe). The catalyst also promoted synthesis of thiophosphinates and selenothiophosphinates from disulfides and diselenides.     

Solvent free,palladium catalyzed highly facile synthesis of diaryl disulfides from aryl thiols

An efficient solvent free Pd(pCH₂S)₂dba catalyzed green-chemical strategy for the synthesis of diaryl disulfides from aryl thiols in moderate to excellent yield is reported. Variety of diaryl disulfides were synthesized. The catalyst is recyclable up to four cycles.     

On the Reaction of Triaryl Trithioarsenites, (ArS)3As,with Octasulfur

para‐Substituted with electron donating or electron withdrawing groups triphenyl trithioarsenites, (ArS)₃As, and octasulfur in refluxing carbon disulfide or chloroform do not give the triaryl tetrathioarsenates, (ArS)₃As=S, as was claimed in the literature for tris(4‐methylphenyl) tetrathioarsenate. In some cases oxidative decomposition to As₂O₃ and disulfides ArSSAr was found. When equivalent amounts of the same esters and octasulfur were heated at 105 or 150 °C no As^V compound was detected or isolated and again some esters decomposed to As₂O₃ and disulfides. These experiments demonstrated that the aromatic trithioarsenites do not react with octasulfur, probably because they cannot open the octasulfur ring. These esters in solution react with octasulfur in the presence of a catalytic (10—20 mol%) amount of triethylamine giving disulfides, As₂O₃ and colored solids which could not be characterized.     

Fe3O4 MNPs-DETA/Benzyl-Br3: A new magnetically reusable catalyst for the oxidative coupling of thiols

We report a new strategy to immobilize a bromine source on the surface of magnetic Fe₃O₄ nanoparticles (Fe₃O₄ MNPs-DETA/Benzyl-Br₃) leading to a magnetically recoverable catalyst, which exhibits high catalytic efficiency in oxidative coupling of thiols to the disulfides (89–98%). The Fe₃O₄ MNPs-DETA/Benzyl-Br₃ catalyst was fabricated by anchoring 3-chloropropyltrimethoxysilane (CPTMS) on magnetic Fe₃O₄ nanoparticles, followed with N-benzylation and reaction with bromine in tetrachloridecarbon. The resulting nanocomposite was analyzed by a series of characterization techniques such as FT-IR, SEM, TGA, VSM and XRD. The catalyst could be recovered via magnetic attraction and could be recycled at least 5 times without appreciable decrease in activity.     

On the Reaction of Triaryl Trithioarsenites, (ArS)3As,with Iodine

Iodine in dry nonprotic solvents oxidizes triaryl trithioarsenites, (ArS)₃As, to As(III) iodide, AsI₃, and disulfides, ArSSAr. The reaction most likely involves arylsulfenyl iodide, ArSI, as an intermediate. With triphenyl and tris(4-chlorophenyl) trithioarsenites, AsI₃ is prepared in very good yields. When the disulfide, which is produced, has MeCONH─ or ─NH─CMe₂─OH groups, then it acts as a Lewis base towards AsI₃ forming complexes with stoichiometry 2AsI₃·3ArSSAr. Probable coordination modes of the AsI₃ are discussed.     

Water Accelerated Sm/TMSCl Reductive System: Debromination of VIC—Dibromides and Reduction of Sodium Alkyl Thiosulfates

A simple and efficient method for the debromination of vic-dibromides to (E)-alkenes and reduction of sodium alkyl thiosulfates to disulfides promoted by Sm/TMSCl/H₂O (trace) has been described.     

Exploratory syntheses,structures, and photoluminescent properties of three lead multi-dimensional frameworks

Three structurally diverse Pb^II coordination complexes, [Pb₃O(OH)(4-sphth)]₂(H₂O) (1), [Pb(3,5-Hdhb)]H₂O (2), and [Pb₃(4-nphth)₂(OH)₂] (3) (4-H₃sphth, 4-sulfophthalic acid; 3,5-H₂dhb, 3,5-dihydroxybenzoic acid; 4-H₂nphth, 4-nitrophthalic acid), were synthesized under hydrothermal conditions. X-ray diffraction analyses reveal that 1 is constructed from [Pb₄O₄] cubanes, based on which ladder-shaped structure is built via 4-H₃sphth bridge. This is the first Pb₄O₄-containing polymer. The Pb₂O₂ units in 2 are bridged by two parallel 3,5-HDHB ligands along the a-axis and two other parallel 3,5-HDHB ligands along the b-axis, forming a 3-D framework. For 3, the crystal structure is built up of a layer motif consisting of corner-sharing pyramidal Pb₃O units, which are linked through Pb corners to form a hexagonal unit. Each PbO₆ polyhedron is connected to three polyhedra (Pb₃O) via sharing an edge (two μ ₃-oxygen atoms) and two faces (three μ ₃-oxygen atoms), thus yielding an infinite 2-D Pb–O–Pb (3,6-net) honeycomb layer. The luminescence of 1–3 demonstrates that they may be good candidates for luminescent materials.     

A Green and Efficient Approach for the Synthesis of 3-Chalcogen Benzo[b]Furans via I2-Mediated Cascade Annulation Reaction of 2-Alkynylanisoles at Room Temperature in Water

Abstract

An efficient and green aqueous protocol to access 3-chalcogen benzo[b]furan derivatives has been developed. The reaction can proceed via I₂-mediated intramolecular annulation reaction of 2-alkynylanisoles with diaryl disulfides (diselenides) in water or under solvent-free conditions at room temperature. With the participation of I₂, a variety of 3-chalcogen benzo[b]furan derivatives were obtained in good to excellent yields. This reaction was considered to work via an iodocyclization cascade mechanism and the intermediate 3-iodo-2-phenylbenzofuran was detected by GC-MS.     

Cu(II)-catalyzed oxidation of sulfides

A variety of sulfides and disulfides were converted into the corresponding sulfoxide derivatives with 70% t-BuOOH (water) as the oxidant in the presence of catalytic quantity of CuBr₂. The method described does not involve cumbersome work-up, has wide range of applicabilities, exhibits chemoselectivity, and proceeds under mild reaction conditions, and the resulting products are obtained in good yields within reasonable time.     

Oxidation/reduction interconversion of thiols and disulfides using hydrogen and oxygen catalyzed by a rhodium complex

RhH(PPh₃)₄ catalyzes reduction of disulfides to thiols by hydrogen and RhH(PPh₃)₄/1,4-bis(diphenylphosphino)butane (dppb) catalyzes oxidation of thiols to disulfides by oxygen.     

A traceless, one-pot preparation of unsymmetric disulfides from symmetric disulfides through a repeated process involving sulfenic acid and thiosulfinate intermediates

A variable group of unsymmetric disulfides was prepared under mild reaction conditions and in high yields through the reaction of symmetric disulfides with sulfuryl chloride followed by treatment with thiols in the presence of water.     

Photoelectron spectra of powder and single crystalline chromium-copper disulfides

2p _3/2,1/2 Photoelectron spectra of single crystalline specimens of chromium-copper disulfides CuCrS₂ and CuCr_0.85V_0.15S₂ are studied. It is shown that the spectra of single crystalline specimens substantially differ from the corresponding spectra of chromium-copper disulfides in the powder state.