Thermal hydrothiolysis of di(2-thienyl)sulfide in the gaseous and liquid phase

At 500–600, di(2-thienyl)sulfide is converted to thiophene, thiophene thiols, dithienyls, and dithienothiophenes, and isomerized to 2,3-dithienylsulfide. Hydrogen sulfide accelerates these reactions significantly. In the liquid phase the thermal conversion of di(2-thienyl)sulfide takes place only with the participation of elemental sulfur or in the system sulfur-hydrogen sulfide. Thiophene and diethienothiophenes are not formed in this case, while isomerization occurs to a large degree. The observed thermal conversions of di(2-thienyl)-sulfide are based on the addition of thiyl radicals to the double bonds of the thiophene ring and to the sulfide sulfur atom.Communication 29 of the series High-temperature organic synthesis. For Communication 28 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1614–1619, December, 1986.     

Thermal transformations of allyl 2-thienyl sulfide and selenide

In the gas phase at 350–410C allyl 2-thienyl sulfide is converted to thiophene-2-thiol, di(2-thienyl) sulfide, and 2-methylthieno[2,3-b]thiophene. In the presence of acetylene thieno[2,3-b]thiophene is formed in addition to these products. Allyl 2-thienyl selenide is converted quantitatively to 2,3-dihydro-2-methylselenopheno[2,3-b]thiophene during fractional distillation in vacuo. Thiophene, di(2-thienyl) selenide, di(2-thienyl) diselenide, thiophene-2-selenol, and 2-methylselenopheno[2,3-b]thiophene are formed in addition to these compounds in the thermolysis of allyl thienyl selenide in the gas phase. In the presence of acetylene the thermal decomposition of allyl thienyl selenide is accompanied by the formation of selenophene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1312–1316, October, 1991.     

[3,3]-sigmatropic rearrangement of allyl 2-benzothienyl sulfide

Allyl 2-benzothienyl sulfide at 20–120 °C undergoes a [3,3]-sigmatropic rearrangement to give 3-allylbenzothiophene-2-thiol. The kinetic parameters of the reaction were studied. Under the experimental conditions the thiol undergoes cyclization to give 2-methyl-2,3-dihydrobenzothieno[2,3-b]thiophene, 2-methyl-benzothieno[2,3-b]thiophene, and benzothieno[2,3-b]dihydrothiopyran. Allyl 3-methyl-2-benzothienyl sulfide does not form a thiol even at 150–190 °C but rather forms only bis(3-methyl-2-benzothienyl) disulfide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 615–618, May, 1981.     

Synthesis of 2-mercapto-substituted thieno[2,3-d]thiazoles and ben zothieno[3,2-d] thiazoles

2-Mercaptothieno[2, 3-d]thiazoles were synthesized from bis(2-nitro-3-thienyl) disulfide by successive reduction of, initially, the disulfide bond and the nitro group in the presence of carbon disulfide without isolation of the intermediate 2-nitro-3-mercaptothiophene. 2-Mercaptobenzo-[b]thieno[3, 2-d]thiazole was synthesized by reaction of 3-aminobenzo[b]thiophene hydrochloride with sulfur monochloride and cleavage of the resulting benzo[b]thienothiazothionium chloride with sodium sulfide in the presence of carbon disulfide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1355–1356, October, 1976.     

Gas-phase Reaction of 2-Chlorothiophene with Hydrogen Sulfide in the Presence of Alcohols

The effect of methanol and ethanol on the route of the gas-phase reaction of 2-chlorothiophene with hydrogen sulfide, leading to 2-thiophenethiol and to bis(2-thienyl) sulfide, has been investigated. It was found that methanol significantly enhances this reaction and increases its selectivity for the thiol at higher temperatures than without the initiator. The optimal conditions were achieved at 570°C in the presence of 10 mole % of methanol when the conversion of the 2-chlorothiophene in the reaction with hydrogen sulfide reaches 98% and the yield of the thiophenethiol (43%) exceeds that of the bis(2-thienyl)sulfide (31%). In the absence of methanol the 2-thiophenethiol is formed only at 510-540°C in just 17% yield, the basic reaction product being the indicated sulfide (52% yield); the conversion of the 2-chlorothiophene does not exceed 54%.     

Transformations of 2-methylthiacyclobutane in the presence of aluminum oxide

The transformations of 2-methylthiacyclobutane at 150–350 °C in the presence of -Al₂O₃ samples with different aprotic acidities were investigated. It was established that the sulfide undergoes isomerization via two pathways, viz., with ring expansion to a five-membered ring and with opening at one C—S bond to give an unsaturated thiol. An experimental confirmation of the consecutive formation of hydrogen sulfide from a one-ring sulfide through a step involving the formation of an unsaturated thiol was obtained for the first time. The transformations are realized as a result of both ionic and polymerization-depolymerization processes.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 184–187, February, 1982.     

Thiyl radicals in gas-phase thermolysis of xanthic acid esters

Gas-phase thermolysis of xanthic acid esters and their reaction with acetylene at 250–600°C have been studied for the first time. The direction of the thermolysis is determined by the nature of the substituents at the oxygen and sulfur atoms. The main products of the thermolysis are gaseous hydrocarbons, carbon monoxide and hydrogen sulfide. The yields of liquid products of the thermolysis and of the reactions with acetylene are 4–46%. The role of thiyl radicals in thiophene molecule formation and reaction routes to carbon disulfide, dithiocarbonates, and stilbene are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 150–153, January, 1996.     

Synthesis and nitration of dimethyl-(3-thienyl)sulfonium salts

Conclusions A method was developed for the synthesis of the difficultly accessible methyl (5-nitro-3-thienyl) sulfide, which consisted in the conversion of methyl 3-thienyl sulfide to the sulfonium salt, with subsequent nitration and demethylation.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1161–1163, May, 1973.     

Rearrangement of allyl thienyl sulfides to allylthiophenethiols

It is shown that the rearrangement of allyl 2-thienyl and allyl 3-thienyl sulfides in various solvents at 89–136°C gives the corresponding allylthiophenethiols, which can subsequently undergo transallylation with the starting sulfide and cyclization to thienodihydrothiopyrans and methyldihydrothienothiophenes. The energy of activation of the rearrangement of both isomeric sulfides is 19 kcal/mole. The pK_a values of thiophenyl and some thiols of the thiophene series were determined, and it was established that the acidities of the allylthiophenethiols do not have a decisive effect on their ability to undergo cyclization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 186–189, February, 1978.     

Reactions of sulfur dichloride with allylthienyl sulfides

The reaction. of allyl-2-thienyl sulfide with sulfur dichloride yields products of intermolecular- addition of intermediately formed sulfenyl chloride to the starting sulfide, and in the case of allyl-3-thienyl sulfide, intramolecular cyclization also takes place with formation of a compound of the thienodithiin series.Moscow State University, Chemistry Faculty, Moscow 119899. A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, Moscow 117813. Translated Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 767–769, June, 1994. Original article submitted April 18, 1994.     

Reactions of aromatic and heteroaromatic compounds bearing electron-acceptor substituents

Dimethyl(2-thienyl)sulfonium salts were synthesized for the first time. The corresponding triiodomercurates were obtained by the reaction of methyl 2-thienyl sulfide or its substituted derivatives with methyl iodide and mercuric iodide. Sulfonium perchlorates are formed as a result of the reaction of thiophene compounds with dimethyl sulfoxide in the presence of POCl₃ and perchloric acid. The HgI₃ ^– anion was replaced by NO₃ ^– by means of an anion-exchange resin. The methods for the dimethylation of sulfonium salts with conversion of them to the corresponding sulfides were studied; the conditions for obtaining quantitative yields from these reactions by means of an anion exchange resin in the acetate form were found.See [1] for communication VII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 165–168, February, 1972.     

[3,3]-Sigmatropic rearrangement of chloro-substituted allyl thienyl sulfides

The kinetics of the rearrangement of allyl 5-chloro-2-thienyl sulfide and -chloroallyl 2-thienyl sulfide to, respectively, 5-chloro-3-allyl-2-thiophenethiol and 3-(-chloroallyl)-2-thiophenethiol were investigated. It is shown that an acceptor substituent in the allyl group decreases the reactivity of the sulfide significantly, whereas an acceptor in the heterocyclic ring does not have an appreciable effect on it.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 181–183, February, 1982.     

Synthesis of thienylhydrogermanes and their transformations in the presence of di(tert-butyl) peroxide

A method was developed for the synthesis of thienylhydrogermanes R_nGeH_4–n (where R=2-thienyl, n=1–3), involving the reduction of the corresponding ethoxygermanes by lithium aluminum hydride under the conditions of phase-transfer catalysis. The transformations of thienylhydrogermanes under the influence of di(tert-butyl) peroxide were studied. Features of the mass-spectrometric behavior of thienylethoxygermanes were analyzed.Latvian Institute of Organic Synthesis, Riga. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 198–201, February, 1997.     

Thiophene Hydrogenation to Tetrahydrothiophene over Tungsten Sulfide Catalysts

Independent reactions of thiophene reduction to tetrahydrothiophene and thiophene hydrogenolysis to form hydrogen sulfide and C₄ hydrocarbons are shown to occur over supported tungsten sulfide catalysts and unsupported tungsten sulfide at an elevated temperature and a high pressure. The highest rate of tetrahydrothiophene formation over the supported catalysts is observed when alumina was used as a support, and the lowest reaction rate is found when silica gel was used as a support. Both catalysts are less active than unsupported tungsten disulfide. The rate of thiophene hydrogenation over tungsten disulfide increases with increasing thiophene concentration and hydrogen pressure and is inhibited by tetrahydrothiophene. The selectivity to tetrahydrothiophene is constant (70–90%) in the whole range up to high thiophene conversions. The high selectivity over tungsten sulfide catalysts is suggested to be due to the reaction pathway through thiophene protonation mediated with the surface SH groups and to the inhibition of hydrogenolysis.     

The influence of activated carbon on the thermal decomposition of sodium ethyl xanthate

The thermal decomposition of SEX in a nitrogen atmosphere was studied by coupled thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The TG curve exhibited two discrete mass losses of 45.8% and 17.8% respectively, at 200 and 257–364°C. The evolved gases identified as a result of the first mass loss were carbonyl sulfide (COS), ethanol (C₂H₅OH), ethanethiol (C₂H₅SH), carbon disulfide (CS₂), diethyl sulfide ((C₂H₅)₂S), diethyl carbonate ((C₂H₅O)₂CO), diethyl disulfide ((C₂H₅)₂S₂), and carbonothioic acid, O, S, diethyl ester ((C₂H₅S)(C₂H₅O)CO). The gases identified as a result of the second mass loss were carbonyl sulfide, ethanethiol, and carbon disulfide. Hydrogen sulfide was detected in both mass losses by py-GC-MS, but not detected by FTIR. The solid residue was sodium hydrogen sulfide (NaSH).SEX was adsorbed onto activated carbon, and heated in nitrogen. Two discrete mass losses were still observed, but in the temperature ranges 100–186°C (7.8%) and 186–279°C (11.8%). Carbonyl sulfide and carbon disulfide were now the dominant gases evolved in each of the mass losses, and the other gaseous products were relatively minor. It was demonstrated that water adsorbed on the carbon hydrolysed the xanthate to cause the first mass loss, and any unhydrolysed material decomposed to give the second mass loss.Mr. N. G. Fisher would like to thank the A. J. Parker CRC for Hydrometallurgy for the provision of a PhD scholarship.     

1, 2-Dithiolium salts

A new method for the synthesis of 1, 2-dithiolium hydrogen sulfates by the oxidation of 1, 2-dithiole-3-thiones with hydrogen peroxide in acetic acid has been developed. From 4-(p-tolyl) 1, 2-dithiolium hydrogen sulfate a series of salts containing anions of inorganic, heteroorganic, and organic acids (Cl^–, Br^–, I^–, ClO ₄ ^– , CNS^–, VO ₃ ^– , HMoOO ₄ ^– , S₂O ₃ ^2– , S₂O ₈ ^2– , Cr₂O ₇ ^2– , Fe(CN) ₆ ^3– , Fe(CN) ₆ ^4– , B(C₆H₅) ₄ ^– , F₃CCOO^–, C₆H₂(NO₂)₃O^–) has been obtained. 4-(p-tolyl)-1, 2-dithiolium salts containing the anions NO ₂ ^– , NO ₃ ^– , ClO ₃ ^– , BrO ₃ ^– , SO ₃ ^2– , SO ₄ ^2– , S₂O ₅ ^2– and Cl₃CCOO^– dissolve in water and do not precipitate in double decomposition reactions. The reactions of 4-(p-tolyl)-1, 2-dithiolium hydrogen sulfate with sodium sulfite, disulfide, and hydrogen sulfide lead to the formation of bis[4-(p-tolyl)-1, 2-dithiol-3-yl] sulfide and disulfide and the sodium salt of 4-(p-tolyl-1, 2-dithiole-3-thiol, respectively. The reaction of 4-(p-tolyl)-1, 2-dithiolium hydrogen sulfate with solutions of salts of the alkali metals containing the anions of weak acids F^–, CNO^–, HCO ₃ ^– , CO ₃ ^2– , B₄O ₇ ^2– , HAsO ₄ ^2– , PO ₄ ^3– , CH₃COO^–, ClCH₂COO^–, etc.) forms bis[4-(p-tolyl)-1, 2-dithlol-3-yl] oxide. [8, Table 3].For part I, see [1].     

2-(Trialkoxysilylalkylthio)ethyl vinyl sulfides

Conclusions Trialkoxysilylalkanethiols (CH₃O)₃Si(CH₂)_nSH (n=1–3) react with divinyl sulfide at 100–110° to give 2-(trialkoxysilylalkylthio)ethyl vinyl sulfides (CH₃O)₃Si(CH₂)_nS (CH₂)₂SCH=CH₂ in high yield. The reactivity of the trialkoxysilylalkanethiols decreases with increase in the number of CH₂ groups between the S and Si atoms. A second molecule of the organosilicon thiol acids adds with difficulty to divinyl sulfide to give the diadduct.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 197–199, January, 1977.     

Reactions of aromatic and heteroaromatic compounds bearing electron-acceptor substituents

The specificity of the nitration and bromination of dimethyl(2-thienyl)sulfonium salts was studied. It was found that, in contrast to methyl 2-thienyl sulfide, which reacts to form 3- and 5-substituted derivatives, the sulfonium salts give a mixture of 4- and 5-substituted products. Total suppression of the activity of the position under the influence of the sulfonium grouping is not observed.See [1] for communication VIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 310–314, March, 1972.     

The fundamental properties of the direct injection method in the analysis of gaseous reduced sulfur by gas chromatography with a pulsed flame photometric detector

In this study, the fundamental aspects of gas chromatography with a pulsed flame photometric detector were investigated through the calibration of gaseous reduced sulfur compounds based on the direct injection method. Gaseous standards of five reduced sulfur compounds (hydrogen sulfide, methane thiol, dimethyl sulfide, carbon disulfide, and dimethyl disulfide) were calibrated as a function of injection volume and concentration level. The results were evaluated by means of two contrasting calibration approaches: fixed standard concentration method (variable volumetric injection of standard gases prepared at a given concentration) and fixed standard volume method (injection of multiple standards with varying concentrations at a given volume). The optimum detection limit values of reduced sulfur compounds, when estimated at 100 μL of injection volume, ranged from 2.37 pg (carbon disulfide) to 4.89 pg (dimethyl sulfide). Although these detection limit values improved gradually with decreasing injection volume, the minimum detectable concentration (e.g., in nmol mol⁻¹ scale) remained constant due to a balance by the sample volume reduction. The linearity property of pulsed flame photometric detector also appeared to vary dynamically with changes in its sensitivity. According to this study, the performance of pulsed flame photometric detector, when tested by direct injection method, is highly reliable to precisely describe the behavior of reduced sulfur compounds above ∼20 nmol mol⁻¹.     

Mechanisms and energetics of free radical initiated disulfide bond cleavage in model peptides and insulin by mass spectrometry

We investigate the mechanism of disulfide bond cleavage in gaseous peptide and protein ions initiated by a covalently-attached regiospecific acetyl radical using mass spectrometry (MS). Highly selective S–S bond cleavages with some minor C–S bond cleavages are observed by a single step of collisional activation. We show that even multiple disulfide bonds in intact bovine insulin are fragmented in the MS2 stage, releasing the A- and B-chains with a high yield, which has been challenging to achieve by other ion activation methods. Yet, regardless of the previous reaction mechanism studies, it has remained unclear why (1) disulfide bond cleavage is preferred to peptide backbone fragmentation, and why (2) the S–S bond that requires the higher activation energy conjectured in previously suggested mechanisms is more prone to be cleaved than the C–S bond by hydrogen-deficient radicals. To probe the mechanism of these processes, model peptides possessing deuterated β-carbon(s) at the disulfide bond are employed. It is suggested that the favored pathway of S–S bond cleavage is triggered by direct acetyl radical attack at sulfur with concomitant cleavage of the S–S bond (S_H2). The activation energy for this process is substantially lower by ∼9–10 kcal mol^–1 than those of peptide backbone cleavage processes determined by density functional quantum chemical calculations. Minor reaction pathways are initiated by hydrogen abstraction from the α-carbon or the β-carbon of a disulfide, followed by β-cleavages yielding C–S or S–S bond scissions. The current mechanistic findings should be generally applicable to other radical-driven disulfide bond cleavages with different radical species such as the benzyl and methyl pyridyl radicals.