- New method of dimethyl sulfi de synthesis
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The synthesis of dimethyl sulfide consists in the reaction of dimethyl disulfide with methanol in the presence of solid catalyst, aluminum γ-oxide. The yield of dimethyl sulfide grows with growing temperature, contact time, and content of methanol in the reaction mixture. At 350-400°C, molar ratio methanol-dimethyldisulfide 2.0-2.5, and total conversion of the reagents the yield of dimethyl sulfide reached 95 mol%. Pleiades Publishing, Ltd., 2011.
- Mashkina
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- Catalytic synthesis of methanethiol from methanol and carbon disulfide over KW/Al2O3 catalysts
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Abstract A series of KW/γ-Al2O3 catalysts with varying K/W mole ratio were prepared for the synthesis of methanethiol from carbon disulfide and methanol, and characterized by N2 adsorption-desorption, XRD and NH3/CO2-TPD techniques. Experimental results showed that the acidic and basic property of the catalyst plays a key role on the catalytic performance. It is shown that the conversion of CH3OH is chiefly related to the acid sites, while the base sites of catalysts are favorable for the selectivity toward CH3SH and hydrocarbons, but the strong base sites will restrain the selectivity toward CH3SH. When the K/W mole ratio is K/W = 2/1 and the reaction temperature is at 603 K, the conversion of CH3OH and the selectivity toward CH3SH are 98.3 and 56.2%, respectively.
- Wang, Weiming,Li, Yang,Zhang, Xiang,Fang, Weiping,Yang, Yiquan
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- Pre-steady-state kinetic and structural analysis of interaction of methionine γ-lyase from Citrobacter freundii with inhibitors
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Methionine γ-lyase (MGL) catalyzes the γ-elimination of L-methionine and its derivatives as well as the β-elimination of L-cysteine and its analogs. These reactions yield α-keto acids and thiols. The mechanism of chemical conversion of amino acids includes numerous reaction intermediates.The detailed analysis of MGL interaction with glycine, L-alanine, L-norvaline, and L-cycloserine was performed by pre-steady-state stopped-flow kinetics. The structure of side chains of the amino acids is important both for their binding with enzyme and for the stability of the external aldimine and ketimine intermediates. X-ray structure of the MGL·L-cycloserine complex has been solved at 1.6 A? resolution. The structure models the ketimine intermediate of physiological reaction. The results elucidate the mechanisms of the intermediate interconversion at the stages of external aldimine and ketimine formation.
- Kuznetsov, Nikita A.,Faleev, Nicolai G.,Kuznetsova, Alexandra A.,Morozova, Elena A.,Revtovich, Svetlana V.,Anufrieva, Natalya V.,Nikulin, Alexei D.,Fedorova, Olga S.,Demidkina, Tatyana V.
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- Development of a Continuous Flow Sulfoxide Imidation Protocol Using Azide Sources under Superacidic Conditions
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The development of a continuous flow sulfoxide imidation protocol for a pharmaceutically relevant target molecule is described. Sulfoxide imidation is a key step in the preparation of certain ATR kinase inhibitors. Reactions with NaN3 or TMSN3 and concentrated sulfuric acid under literature conditions provided low conversions and poor selectivities. In contrast, reactions employing fuming sulfuric acid afforded the target sulfoximine with a selectivity of ～90% after a reaction time of only 10-15 min at 50 °C. The imidation reaction using TMSN3 as reagent was successfully performed in a flow reactor utilizing CH2Cl2/H2SO4 biphasic conditions. The mixture was subsequently quenched in-line with H2O. Phase separation, neutralization, and re-extraction with an organic solvent furnished the product in excellent purity and good yields, albeit with loss of chirality.
- Gutmann, Bernhard,Elsner, Petteri,O'Kearney-Mcmullan, Anne,Goundry, William,Roberge, Dominique M.,Kappe, C. Oliver
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- Reactions of α-isobutyl-α-(methylthio)methylene Meldrum's acid with primary amines in aqueous DMSO
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The aminolysis of α-isobutyl-α-(methylthio)methylene Meldrum's acid 7 with primary amines, namely, n-butylamine, glycinamide, and methoxyethylamine in DMSO-H2O (50:50, v/v) at 20°C is overall second-order but first-order in both 7 and amines. The reaction with aminoacetonitrile (AA) is overall third-order, first-order in substrate, and second-order in amine at low amine concentration, while at high amine concentration and high pH the dependence on amine is first-order. A general three-step mechanism has been proposed for all these reactions. For the former group of amines, the first step is a rate-limiting attack of the amine to form the tetrahedral intermediate (TA±), followed by a fast acid-base equilibrium and a fast RNH3+- or H 2O-assisted leaving group expulsion. For AA, general base catalysis was confirmed from the dependence of kA on [AA]f and on [OH-]. For all four amines, a good Bronsted plot of log k 1 vs. pKaAH in DMSO-H2O (50:50, v/v) with βnuc = 0.34 ± 0.02 was observed. These observations are consistent with the suggested mechanism.
- Biswas, Supriya,Ali, Mahammad,Rappoport, Zvi,Salim, Hatim
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- Catalytic synthesis of methanethiol from CO/H2/H2S mixtures using α-Al2O3
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Sustained synthesis of methanethiol from the reaction of CO/H 2/H2S mixtures is reported and discussed. Surprisingly, unmodified α-Al2O3 gives the best results for this reaction and methanethiol selectivities of > 98% at CO conversions of ca. 6% can be readily obtained (CO:H2:H2S = 4:5:1, 340°C, total pressure = 20 bar, 200 h-1). Reaction of CO+ H2 (CO:H2 = 1:1) in the absence of H2S using α-Al 2O3 under comparable conditions gives a lower CO conversion (ca. 1.3%) with significant selectivities to methane (20%), methanol (28.5%) and ethanol (21.1%). When H2S is added to the synthesis gas feedstock, the product selectivity switches to sulfur-containing products, almost exclusively methanethiol, but some by-product thiophene is also observed. A range of other catalysts were also investigated (e.g., γ-Al 2O3, Cr2O3, Cr2O 3/Al2O3, Cu/Cr2O3) but all give inferior catalytic performance when compared with α-Al 2O3. The mechanism of the synthesis of methanethiol is discussed, based on a modification of chain propagation in the Fischer-Tropsch synthesis reaction.
- Zhang, Baojian,Taylor, Stuart H.,Hutchings, Graham J.
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- Activity of zeolites in dimethyl sulfide synthesis
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Dimethyl disulfide conversion into dimethyl sulfide over various zeolites in an inert medium at atmospheric pressure and T = 190-330°C is reported. A significant activity in dimethyl sulfide formation is shown by the decationized zeolites HNaY and HZSM-5, whose surface has strong protonic and nonprotonic acid sites. Cobalt-containing faujasite is more active than HNaY, and the activity of CoHZSM-5 is comparable with the activity of its decationized counterpart.
- Mashkina,Khairulina
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- Metal Oxides as Catalysts for the Reaction between Methanol and Hydrogen Sulfide
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The reaction between methanol and hydrogen sulfide leading to the formation of methanethiol and dimethyl sulfide has been studied using different H2S:CH3OH molar ratios (0.5:1, 1:1, 2:1) at 623 K on various metal oxides presenting different acidity and basicity.The correlations between activity and selectivity of catalysts and their average oxygen and cation charges as well as the strength of their acidic and basic sites, determined by adsorption of probe molecules followed by IR spectroscopy, are as follows: (i) the highest strenth of basic sites and the highest negative charge on oxygen (MgO) lead to the lowest activity and the highest selectivity toward CH3SH; (ii) the lowest strength of basic sites (medium oxygen charge) and the highest cation charge (γ-Al2O3) cause the highest activity and the highest selectivity toward (CH3)2S.The dimethyl sulfide selectivity is in the reverse order of the number of basic sites.IR measurements show that the reaction occurs between chemisorbed methanol (methoxy species) and SH(1-) species or/and H2S molecules.Too strongly held methoxy species as on MgO and PO4(3-)/SiO2 do not react with H2S.The difference in activity and selectivity of both titania samples (anatase and rutile) is discussed.
- Ziolek, M.,Kujawa, J.,Saur, O.,LaValley, J. C.
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- Thiolation behaviors of methanol catalyzed by bifunctional ZSM-5@t-ZrO2 catalyst
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The catalytic properties of bifunctional ZSM-5@t-ZrO2 catalyst for methanol thiolation were revealed by using methanol and H2S as probe molecules. Taking the ZSM-5/t-ZrO2 physically-blended catalyst, pure ZSM-5 and t-ZrO2 as control catalysts, we investigated the characteristics of adsorption and transformation of different reaction molecules on or over different catalysts by combination of in-situ diffuse reflectance Fourier transform infrared spectroscopy (Drifts) and a variety of techniques including XRD, XPS, XRF, FT-IR, N2 adsorption-desorption, CO2/NH3-TPD, and DSC. The results showed that the synergistic effect of acid sites between ZSM-5 phase and t-ZrO2 phase in the bifunctional catalyst enhanced the adsorption and dissociation of methanol molecules, while the base sites in t-ZrO2 phase were mainly responsible for the adsorption and dissociation of H2S molecules. Due to the small specific surface area of pure t-ZrO2 catalyst, precursor species for sulfur deposition and carbon deposition were easily formed. Presulfurization could improve the initial activity of methanol thiolation and shorten the induction period. The dissociation of H2S at the base sites was the rate-determining step of the bimolecular reaction, and the appropriate increase of base sites in the bifunctional components could construct the matching formation rate of sulfhydryl and methoxy groups. At the same time, the special composite structure and meso-microporous system of ZSM-5@t-ZrO2 could effectively reduce the formation rate of carbon and sulfur deposits.
- Cao, Jianxin,Kawi, Sibudjing,Liu, Fei,Pei, Lijie,Wang, Xiaodan,Yang, Anjie,Yao, Mengqin,Zhao, Tianxiang
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- BORON CONTAINING COMPOUNDS AND THEIR USES
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The present disclosure contemplates novel boron-containing compounds and their uses as active agents that exhibit pesticidal activity such as antimicrobial, insecticidal, arachnicidal, and/or anti parasitic activity. An agrochemical composition containing such a compound and its use in, animal health, agriculture, or horticulture is also contemplated. A method for promoting plant performance and/or controlling, reducing, preventing, ameliorating, or inhibiting microbes, insects, arachnids, and/or parasites on or in an animal, a plant, a plant part, plant propagation material, and/or harvested fruits or vegetables is also contemplated.
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Paragraph 0254; 0255
(2020/03/29)
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- PROCESS FOR THE PREPARATION OF METHYL MERCAPTAN
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The invention relates to a process for preparing methyl mercaptan from a mixture of carbon oxide, hydrogen sulfide and hydrogen, in the presence of a catalyst based on molybdenum and potassium supported on zirconia, said catalyst not comprising any promoter.
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Paragraph 0058-0060
(2020/11/30)
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- The role of weak Lewis acid sites for methanol thiolation
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Weak Lewis acid sites combined with strong base sites of Cs+ supported on WS2 and γ-Al2O3 act as active sites in the thiolation of methanol. The acid-base pairs dissociate methanol upon adsorption. The formed surface alcoholate and the corresponding sulfuryl groups enable the substitution of oxygen for sulfur in a Langmuir-Hinshelwood mechanism. Stronger Lewis acid sites catalyze dimethyl ether formation via the Eley-Rideal mechanism in which methoxy groups react with gas phase methanol. The results demonstrate the importance of adjusting the acid-base strength in oxides to selectively catalyze substitution reactions.
- Weber-Stockbauer, Manuel,Gutiérrez, Oliver Y.,Bermejo-Deval, Ricardo,Lercher, Johannes A.
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p. 509 - 516
(2019/01/28)
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- Rh-Catalyzed Hydrogenation of CO2 to Formic Acid in DMSO-based Reaction Media: Solved and Unsolved Challenges for Process Development
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Process concepts have been conceived and evaluated for the amine-free homogeneous catalyzed hydrogenation of CO2 to formic acid (FA). Base-free DMSO-mediated production of FA has been shown to avoid the formation of stable intermediates and presumably the energy-intensive FA recovery strategies. Here, we address the challenges in the development of an overall process: from catalyst immobilization to the FA isolation. The immobilization of the homogeneous catalyst was achieved using a multiphasic approach (n-heptane/DMSO) ensuring high retention of the catalyst (>99%) and allowing facile separation of the catalyst-free product phase. We show that the strong molecular interactions between DMSO and FA on the one hand shift the equilibrium towards the product side, on the other hand, lead to the formation of an azeotrope preventing a simple isolation step by distillation. Thus, we devised an isolation strategy based on the use of co-solvents and computed the energy demands. Acetic acid was identified as best co-solvent and its compatibility with the catalyst system was experimentally verified. Overall, the outlined process involving DMSO and acetic acid as co-solvent has a computed energy demand on a par with state-of-the art amine-based processes. However, the insufficient chemical stability of DMSO poses major limitations on processes based on this solvent. (Figure presented.).
- Jens, Christian M.,Scott, Martin,Liebergesell, Bastian,Westhues, Christian G.,Sch?fer, Pascal,Franciò, Giancarlo,Leonhard, Kai,Leitner, Walter,Bardow, André
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supporting information
p. 307 - 316
(2018/11/10)
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- DEMETHYLATION OF METHYL ESTER OF METHIONINE AND ITS HYDROXY ANALOG
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The following invention regards a process of demethylating a methyl ester of methionine or its hydroxy analog and producing methane thiol as a side-product. The methionine and its hydroxy analog are suitable as an animal feed additive and as a food additive. The methane thiol may be consumed in a hydrothiolation step such as in a step of preparing the methyl ester of methio- nine or its hydroxy analog from from methyl vinyl glycolate.
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Page/Page column 14-15
(2019/12/04)
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- Trithioorthoester Exchange and Metathesis: New Tools for Dynamic Covalent Chemistry
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To expand the toolbox of dynamic covalent and systems chemistry, we investigated the acid-catalyzed exchange reaction of trithioorthoesters with thiols. We found that trithioorthoester exchange occurs readily in various solvents in the presence of stoichiometric amounts of strong Bronsted acids or catalytic amounts of certain Lewis acids. The scope of the exchange reaction was explored with various substrates, and conditions were identified that permit clean metathesis reactions between two different trithioorthoesters. One distinct advantage of S, S, S-orthoester exchange over O, O, O-orthoester exchange is that the exchange reaction can kinetically outcompete hydrolysis, thereby making the process less sensitive to residual moisture. We expect that the relatively high stability of the products might be beneficial in future supramolecular receptors or porous materials.
- Bothe, Michael,Furlan, Ricardo L. E.,Orrillo, A. Gastón,Von Delius, Max
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p. 1988 - 1994
(2019/10/22)
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- PROCESS FOR CONVERSION OF DIMETHYL SULFIDE TO METHYL MERCAPTAN
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Disclosed herein are systems and processes involving the catalyzed cleavage reaction of dimethyl sulfide to methyl mercaptan. The catalyzed cleavage reaction can be a standalone system or process, or can be integrated with a methyl mercaptan production plant.
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Paragraph 0086-0089
(2018/03/09)
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- Method for preparing methyl mercaptan through reaction of methyl chloride and hydrogen sulfide
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The invention discloses a method for preparing methyl mercaptan through a reaction of methyl chloride and hydrogen sulfide. The method comprises the following steps: inflating quantitative methyl chloride and hydrogen sulfide gas into a reactor in which a catalyst is added, and performing a chemical reaction at a certain temperature and under a certain pressure, cooling after the completion of thereaction, and separating to obtain the methyl mercaptan. By the method, the gas-gas reaction is adopted, the operation is simple, a target product has high selectivity and high purity, no waste wateris produced in the process, the pollution is low and a byproduct is mainly hydrogen chloride which can be sold as a product, so that the method has a relatively great economic significance.
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Paragraph 0041-0070
(2018/09/13)
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- Soluble and nanoporous silica gel-entrapped C. freundii methionine γ-lyase
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Methionine γ-lyase is a pyridoxal 5'-phosphate dependent tetramer that catalyzes the α,γ-elimination of methionine in ammonia, methanethiol and γ-ketobutyrate. MGL catalytic power has been exploited as a therapeutic strategy to reduce the viability of cancer cells or bacteria. In order to obtain a stable enzyme to be delivered at the site of action, MGL can be encapsulated in a variety of matrices. As a reference encapsulation strategy we have prepared MGL nanoporous wet silica gels. Immobilized MGL gels were characterized with regards to activity, stability, absorption, circular dichroism and fluorescence properties and compared with soluble MGL. We found that MGL gels exhibit (i) spectroscopic properties very similar to MGL in solution, (ii) a higher stability with respect to the soluble enzyme and (iii) catalytic activity six-fold lower than in solution. These findings prove that MGL encapsulation is a suitable strategy for therapeutic applications.
- Morozova, Elena A.,Kulikova, Vitalia V.,Faggiano, Serena,Raboni, Samanta,Gabellieri, Edi,Cioni, Patrizia,Anufrieva, Natalia V.,Revtovich, Svetlana V.,Demidkina, Tatyana,Mozzarelli, Andrea
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p. 2210 - 2219
(2018/01/12)
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- Investigation of the reaction pathway for synthesizing methyl mercaptan (CH3SH) from H2S-containing syngas over K-Mo-type materials
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The reaction pathway for synthesizing methyl mercaptan (CH3SH) using H2S-containing syngas (CO/H2S/H2) as the reactant gas over SBA-15 supported K-Mo-based catalysts prepared by different impregnation sequences
- Lu, Jichang,Liu, Pan,Xu, Zhizhi,He, Sufang,Luo, Yongming
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p. 21340 - 21353
(2018/06/26)
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- Ex Situ Formation of Methanethiol: Application in the Gold(I)-Promoted Anti-Markovnikov Hydrothiolation of Olefins
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A protocol for the Au-promoted anti-Markovnikov hydrothiolation of olefins using ex situ generated methanethiol is reported. The use of S-methylisothiourea hemisulfate salt as a solid precursor for methanethiol generation ensures a safe and reliable deliverance of a stoichiometric amount of this thiol. The procedure was shown to work for a broad range of olefins providing the corresponding hydrothiolated adduct in good to excellent yields. Mechanistic evaluations suggest that thiyl radicals are generated and that gold acts as an efficient but stable radical initiator.
- Kristensen, Steffan K.,Laursen, Simon L. R.,Taarning, Esben,Skrydstrup, Troels
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supporting information
p. 13887 - 13891
(2018/10/02)
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- Catalytic Synthesis of Methylthiophenes
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The gas-phase reaction of dimethyl disulfide with thiophene over Co/HZSM-5 catalyst in a helium medium under atmospheric pressure at 250–350°C gave a mixture of mono-, di-, tri-, and tetramethylthiophenes with an overall selectivity of 94–96%.
- Mashkina,Khairulina
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p. 1794 - 1797
(2019/03/26)
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- Catalytic synthesis of dialkyl sulfides from dialkyl disulfides
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Dialkyl disulfides R2S2 where R = Me, Et, or Pr, both as individual compounds and as their mixtures, isolated from petroleum products can turn into alkanethiols and dialkyl sulfides under the action of catalysts having strong acid sites and medium-strength basic sites on their surface. In a helium atmosphere, the main conversion products are alkanethiols, while dialkyl sulfides form in low yield at a selectivity of no higher than 20%. A much higher dialkyl sulfide selectivity is attained in the reaction involving methanol. The most efficient catalyst for this reaction is alumina, with which the dialkyl sulfide selectivity is up to 99%.
- Mashkina,Khairulina
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p. 402 - 408
(2017/08/08)
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- PROCESS FOR PRODUCING METHYL MERCAPTAN FROM DIMETHYL SULFIDE
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The present invention generally relates to the manufacture of methyl mercaptan using recycled dimethyl sulfide. In particular, the invention relates to a process for the continuous production of methyl mercaptan via the catalytic conversion of dimethyl sulfide using a non-promoted Al2O3 catalyst at low temperatures.
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Paragraph 0068-0069
(2018/01/04)
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- METHOD FOR PREPARING METHYL MERCAPTAN
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The present invention relates to a method for preparing methyl mercaptan, in batches or continuously, preferably continuously, said method including at least the following steps: a) reacting at least one hydrocarbon feedstock in the presence of hydrogen sulphide (H2S) and optionally sulphur (S) such as to form carbon disulphide (CS2) and hydrogen (H2); b) reacting said carbon disulphide (CS2) by hydrogenation in the presence of said hydrogen (H2) obtained in step a) such as to form methyl mercaptan (CH3SH), hydrogen sulphide (H2S) and possibly hydrogen (H2); c) optionally recirculating said hydrogen sulphide (H2S) formed during step b) to step a); and d) recovering the methyl mercaptan.
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Paragraph 0107-0110
(2017/06/27)
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- Method for catalyzing CO2 hydrogenation reduction by using sulfur-containing iridium complex
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The invention relates to a method for catalyzing CO2 hydrogenation reduction by using a sulfur-containing iridium complex. A sulfur-containing substituent-substituted dipyridyl iridium complex is synthesized and used as a catalyst to catalyze CO2 hydrogenation. The method has the advantages as follows: the iridium complex has good water solubility, no organic solvent is required to be added to a catalytic reaction, and pollution caused by the organic solvent is avoided; besides, a sulfydryl dipyridyl ligand is synthesized successfully with a thiourea alkylation hydrolysis method for the first time, the preparation process is simple, and synthesis methods, such as a sodium hydrosulfide alkylation method and the like, which cause severe environmental pollution are avoided. The invention provides a novel efficient transition metal catalyst for catalyzing CO2 hydrogenation.
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Paragraph 0034; 0036
(2017/01/23)
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- Catalytic reactions of dimethyl disulfide with thiophene and benzene
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The gas-phase reaction of dimethyl disulfide with thiophene proceeds under the action of acid catalysts under atmospheric pressure at 160-350°C and a residence time of τ = 0.6-21 s to form thioalkylation and alkylation products. Dimethyl disulfide reacts with benzene to form only alkylation products. Catalysts containing both strong protic and Lewis acid sites, as well as basic sites of moderate strength, are the most active ones.
- Mashkina,Khairulina
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- Effects of water and alcohols on the polymerization of furan during its acid-catalyzed conversion into benzofuran
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Furan, an important product from catalytic pyrolysis of biomass, has the potential to be further converted into value-added chemicals or biofuels. This study investigated the conversion of furan into benzofuran over a Br?nsted acid catalyst (Amberlyst 70) at 140-190°C in various solvents. With water as the solvent, furan could barely make its way to benzofuran as its polymerization dominated. With methanol as the solvent, the polymerization of furan was suppressed and benzofuran formation was enhanced substantially. This is because in methanol, the reactive intermediates (i.e., aldehydes) were stabilized and their involvement in polymerization reactions was suppressed. Other alcohols showed similar effects on suppressing polymerization. In dimethyl sulfoxide (DMSO), the polymerization of furan was also effectively suppressed. However, furan was not converted to benzofuran but to levulinic acid via a distinct reaction route.
- Hu, Xun,Jiang, Shengjuan,Kadarwati, Sri,Dong, Dehua,Li, Chun-Zhu
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p. 40489 - 40501
(2016/05/24)
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- C-S bond cleavage by a polyketide synthase domain
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Leinamycin (LNM) is a sulfur-containing antitumor antibiotic featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. The 1,3-dioxo-1,2- dithiolane moiety is essential for LNM's antitumor activity, by virtue of its ability to generate an episulfonium ion intermediate capable of alkylating DNA. We have previously cloned and sequenced the lnm gene cluster from Streptomyces atroolivaceus S-140. In vivo and in vitro characterizations of the LNM biosynthetic machinery have since established that: (i) the 18-membered macrolactam backbone is synthesized by LnmP, LnmQ, LnmJ, LnmI, and LnmG, (ii) the alkyl branch at C-3 of LNM is installed by LnmK, LnmL, LnmM, and LnmF, and (iii) leinamycin E1 (LNM E1), bearing a thiol moiety at C-3, is the nascent product of the LNM hybrid nonribosomal peptide synthetase (NRPS)-acyltransferase (AT)-less type I polyketide synthase (PKS). Sulfur incorporation at C-3 of LNM E1, however, has not been addressed. Here we report that: (i) the bioinformatics analysis reveals a pyridoxal phosphate (PLP)-dependent domain, we termed cysteine lyase (SH) domain (LnmJ-SH), within PKS module-8 of LnmJ; (ii) the LnmJ-SH domain catalyzes C-S bond cleavage by using L-cysteine and L-cysteine S-modified analogs as substrates through a PLP-dependent β-elimination reaction, establishing L-cysteine as the origin of sulfur at C-3 of LNM; and (iii) the LnmJ-SH domain, sharing no sequence homology with any other enzymes catalyzing C-S bond cleavage, represents a new family of PKS domains that expands the chemistry and enzymology of PKSs and might be exploited to incorporate sulfur into polyketide natural products by PKS engineering.
- Ma, Ming,Lohman, Jeremy R.,Liu, Tao,Shen, Ben
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p. 10359 - 10364
(2015/09/01)
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- Turning tryptophanase into odor-generating biosensors
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An odor-based sensor system that exploits the metabolic enzyme tryptophanase (TPase) as the key component is reported. This enzyme is able to convert an odorless substrate like S-methyl-L-cysteine or L-tryptophan into the odorous products methyl mercaptan or indole. To make a biosensor, TPase was biotinylated so that it could be coupled with a molecular recognition element, such as an antibody, to develop an ELISA-like assay. This method was used for the detection of an antibody present in nM concentrations by the human nose. TPase can also be combined with the enzyme pyridoxal kinase (PKase) for use in a coupled assay to detect adenosine 5-triphosphate (ATP). When ATP is present in the low μM concentration range, the coupled enzymatic system generates an odor that is easily detectable by the human nose. Biotinylated TPase can be combined with various biotin-labeled molecular recognition elements, thereby enabling a broad range of applications for this odor-based reporting system. The nose knows: Tryptophanase (TPase), which converts S-methyl-L-cysteine into methyl mercaptan (smelly), was coupled to a molecular recognition element (such as an antibody) to create an odor-based biosensor. Biotinylated TPase could be combined with various biotin-labeled molecular recognition elements, thereby enabling a broad range of applications for this odor-based reporting system.
- Xu, Yaqin,Zhang, Zhuyuan,Ali, M. Monsur,Sauder, Joanna,Deng, Xudong,Giang, Karen,Aguirre, Sergio D.,Pelton, Robert,Li, Yingfu,Filipe, Carlos D. M.
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supporting information
p. 2620 - 2622
(2014/03/21)
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- An efficient synthesis of some novel 3-cyano-4-imino-2-(methylthio)4H- pyrido[1,2-a]pyrimidine and their derivatives
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Pyrazolo pyrimido pyrimidine (4a-k) was prepared by the reaction of compound 3-cyano-4-imino-2-(methylthio)4H-pyrido[1,2-a]pyrimidine (3) with hydrazine hydrate, phenyl hydrazine, 2-hydrazino benzothiazole, and 6-substituted hydrazine benzothiazole in N,N-dimethylformamide and anhydrous potassium carbonate. These synthesized compounds were characterized by elemental analysis IR, 1H NMR, and mass spectral data.
- Vartale, Sambhaji P.,Halikar, Nilesh K.,Sirsat, Shivraj B.,Pawar, Yogesh D.
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p. 351 - 354
(2013/06/04)
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- Synthesis antimicrobial and anticancer activity of N′- arylmethylidene-piperazine-1-carbothiohydrazide
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Ten newly synthesized thiosemicarbazones of piperazine (3a-3j) were evaluated for their antibacterial and antifungal activity against non-pathogenic strains of Escherichia coli (NCIM 2068), Klebsiella pneumonia (NCIM 2957), Staphylococcus aureus (NCIM 2079), and Bacillus subtilis (NCIM 2921); pathogenic strains of Vibrio cholerae, protease, Candida albicans and Aspergillus niger. All the 10 compounds (3a-3j) were found to be better than Ciprofloxacin against B. subtilis and four molecules (3c, 3d, 3e, and 3h) against S. aureus. Compound 3j, a derivative of benzophenone, has been identified as a potent and promising candidate against C. albicans. The compounds were also evaluated for their anticancer activity against HBL-100 and HL60 cell lines. Compound 3a, a p-hydroxy benzaldehyde derivative, has been identified as a potent and promising candidate.
- Kulandaivelu, Umasankar,Shireesha, Boyapati,Mahesh, Chidara,Vidyasagar, Jannu Vincent,Rao, Tadikonda Rama,Jayaveera,Saiko, Philipp,Graser, Geraldine,Szekeres, Thomas,Jayaprakash, Venkatesan
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p. 2802 - 2808
(2013/07/26)
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- Sulfur as a selective 'soft' oxidant for catalytic methane conversion probed by experiment and theory
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Developing efficient catalytic processes to convert methane into useful feedstocks relies critically upon devising new coupling processes that use abundant, thermodynamically 'mild' oxidants together with selective catalysts. We report here on elemental sulfur as a promising 'soft' oxidant for selective methane conversion to ethylene over MoS 2, RuS 2, TiS 2, PdS and Pd/ZrO 2 catalysts. Experiments and density functional theory reveal that methane conversion is directly correlated with surface metal-sulfur bond strengths. Surfaces with weakly bound sulfur are more basic and activate methane C-H bonds more readily. In contrast, experimental and theoretical selectivities scale inversely with surface metal-sulfur bond strengths, and surfaces with the strongest metal-sulfur bonds afford the highest ethylene selectivities. High CH 4 /S ratios, short contact times and the provision of a support maximizes the coupling of CH x intermediates and selectivity to ethylene, because these conditions yield surfaces with stronger metal-sulfur bonding (for example, Pd 16 S 7), which suppresses the over-oxidation of methane.
- Zhu, Qingjun,Wegener, Staci L.,Xie, Chao,Uche, Obioma,Neurock, Matthew,Marks, Tobin J.
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p. 104 - 109
(2013/08/24)
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- Thiolation of dimethyl sulfide to methanethiol over WO3/ZrO 2 catalysts
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The thiolation of dimethyl sulfide with H2S over a variety of tungsten-zirconia (WO3/ZrO2) catalysts with different contents of WO3 was studied. The maximum yield of methanethiol was obtained at the reaction temperature of 633 K in the presence of 10 wt.%WO 3/ZrO2 catalyst. XRD, BET and TPD characterization results reveal that supporting WO3 species on ZrO2 gives rise to the improvement of both in structure stability and surface acidity. The MT yield increased first and then decreased with the increase of reaction temperature for all of the catalysts due to the decomposition of methanethiol and dimethyl sulfide. The optimum loading of WO3 was found to be 5-10 wt.% (with a surface density of 3.5-4.5 w-atom nm-2). Furthermore, the WO 3/ZrO2 catalyst exhibits high resistance to water.
- Chen, Shiping,Wang, Weiming,Zhang, Yuanhua,Wei, Yucai,Fang, Weiping,Yang, Yiquan
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- Iridoid glucosides and anthraquinone from the aerial parts of Saprosma fragrans
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Paederoside, paederosidic acid, 1,3-dimethoxyanthraquinone-2-carboxylic acid and β-sitosterol-D-glucoside have been isolated from the ethanolic extract of the aerial parts of Saprosma fragrans and their structures were established by spectral evidences and chemical studies. This is the first report of iridoid glucosides, paederoside and paederosidic acid containing rarely encountered S-methyl thiocarbonate moiety, 1,3-dimethoxyanthraquinone-2- carboxylic acid and β-sitosterol-D-glucoside in S. fragrans. The identities of isolated iridoid glucosides were also verified by detailed spectral data (UV, IR, FAB-MS, 1H NMR and 13C NMR) analyses of acetate derivatives of paederoside and paederosidic acid prepared by the acetylation of the respective iridoid glucosides.
- Singh,Verma
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p. 429 - 431
(2012/11/13)
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- PROCESS FOR CONTINUOUSLY PREPARING METHYL MERCAPTAN FROM CARBON COMPOUNDS, SULFUR AND HYDROGEN
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The invention relates to a process for continuously preparing methyl mercaptan by reacting a mixture comprising carbon compounds with sulfur and hydrogen, wherein the carbon disulfide and hydrogen sulfide compounds which form are subsequently converted to methyl mercaptan.
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Page/Page column 5
(2011/02/18)
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- Hydrogenation Catalyst, Particularly for Carbon Disulphide
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The present invention relates to a hydrogenation catalyst, particularly useful for the hydrogenation of carbon disulphide (CS2) to form methyl mercaptan (CH3SH), and to a preparation method thereof. The present invention also relates to a method for continuously preparing methyl mercaptan by the catalytic hydrogenation of carbon disulphide, with a carbon disulphide conversion rate of 100%, and a methyl mercaptan selectivity of 100%.
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Page/Page column 4-5
(2011/09/20)
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- PROBIOTIC MICROORGANISMS FOR THE REDUCTION OF MANURE ODOR
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Described are microorganism which are able to reduce the generation of feces odor by decreasing the amount of at least one of the compounds methyl mercaptan, a sulphide compound, cadavarine, putrescine, indole or skatole, and wherein said decrease in the amount of said compounds is independent of the growth of the microorganism. Also described are compositions, comprising such microorganisms, e.g. food, feed or pharmaceutical compositions and the use of such microorganisms for suppressing feces odor or the preparation of foodstuff or feedstuff, as well as corresponding methods for the production of food or feed composition and additives for food, feed or drinks.
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- A convenient method for synthesis of bis-2,2′-(1,3,4-thiadiazole) and bis-3,3′-(1,2,4-triazole) derivatives
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Reactions of the bis-hydrazonoyl chloride 1 with ketene N,S-acetal 2 and the active methine thioanilides 4 and 6 provide a new convenient site-selective synthetic strategy to functionalized bis-3,3′-(1,2,4-triazoles) 3 and bis-2,2′-(1,2,4-thiadiazoles) 5 and 7.
- Shawali, Ahmad S.,Sayed, Abdelwahed R.,Zayed, Mohie M.
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experimental part
p. 311 - 314
(2011/12/04)
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- Synthesis of acylsilanes by palladium-catalyzed cross-coupling reaction of thiol esters and silylzinc chlorides
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An acylsilane synthesis by a Pd-catalyzed cross-coupling reaction of thiol esters and silylzinc chlorides was developed. S-Phenyl thiol esters with a variety of functional groups were converted to corresponding acylsilanes.
- Azuma, Hiroki,Okano, Kentaro,Tokuyama, Hidetoshi
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supporting information; experimental part
p. 959 - 961
(2011/12/05)
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- MO CONTAINING CATALYST, A PREPARATION METHOD AND A METHOD FOR PREPARING METHYL MERCAPTAN
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A method is described to prepare a Mo containing supported catalyst comprising TeO2 as active promoter and a process for preparing methanethiol in the presence of said catalyst.
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Page/Page column 2-3
(2010/04/30)
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- SUPPORTED MO-O-K-MExOy CATALYST FOR THE SYNTHESIS OF METHANETHIOL FROM HIGH H2S-CONTAINING SYNGAS
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This invention is related to a preparation method of a supported catalyst Mo—O—K-MexOy for the synthesis of methanethiol from H2S-containing syngas. The catalyst comprises of an active component of Mo—O—K-based species, an active promoter and a support denoted as metal (or metals)-carrier. The support is prepared by electroless plating method in such a way that the metal or metals chosen are plated onto the surface of the carrier. Transition metal, especially Fe, Co or Ni are selected to be the plating metal, while SiO2, Al2O3 or TiO2 are selected to be carrier. The catalyst thus prepared is found to be efficient for the synthesis of methanethiol from H2S-containing syngasor carbon oxides/hydrogen mixtures, especially regarding a minor formation of the by-product CO2.
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Page/Page column 3; 4
(2010/12/29)
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- Regioselectivity of cyclization of 1-(6-methyl-5-oxo-2,5-dihydro-1,2,4- triazin-3-yl)-4-arylthiosemicarbazides by treating with methyl iodide and dicyclohexylcarbodiimide
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1-(6-Methyl-5-oxo-2,5-dihydro-1,2,4-triazin-3-yl)-4-arylthiosemicarbazides treated with methyl iodide in the presence of sodium acetate in ethanol convert into 6-methyl-3-arylamino[1,2,4]-triazolo[4,3-b][1,2,4]triazin-7(1H)-ones. In reaction with dicyclohexylcarbodiimide 6-methyl-3-arylamino[1,2,4]triazolo[3,4- c][1,2,4]triazin-5(1H)-ones were obtained which at heating in alcohol solution in the presence of sodium acetate or at 262-272°C underwent the Dimroth rearrangement to give 3-methyl-7-arylamino[1,2,4]triazolo[5,1-c][1,2,4]-triazin- 4(8H)-ones. Pleiades Publishing, Ltd., 2010.
- Vas'kevich,Savitskii,Rusanov,Staninets
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experimental part
p. 1682 - 1686
(2011/03/19)
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- Dimethyl disulfide conversion into dimethyl sulfide in the presence of sulfidized catalysts
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The conversion of dimethyl disulfide in the presence of various supported sulfidized metal-containing catalysts at atmospheric pressure and T = 150-350°C was studied. Sulfidized transition metals supported onto aluminum oxide were more active than catalysts based on a carbon support, silicon dioxide, amorphous aluminosilicate, and zeolite ZSM-5. The most active catalyst was 10% Co/Al2O3 prepared with the use of cobalt acetate as an active component precursor and treated with a mixture of hydrogen sulfide with hydrogen at T = 400°C. From kinetic data, it follows that all of the reaction products were formed simultaneously at a temperature of 200°C, whereas a consecutive reaction scheme took place at higher temperatures. In the presence of a sulfidized alumina-cobalt catalyst, the output of dimethyl sulfide was higher than that reached with the use of other well-known catalysts.
- Mashkina,Khairulina
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experimental part
p. 724 - 730
(2011/02/16)
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- PROCESS FOR PREPARING METHYL MERCAPTAN
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The present invention relates to a process for continuously preparing methyl mercaptan from hydrogen sulphide and methanol in a direct connection with the preparation of hydrogen sulphide.
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Page/Page column 2
(2009/04/24)
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- AMIDINE DERIVATIVES AND THEIR APPLICATIONS AS A MEDICAMENT
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The invention concerns amidine derivatives of general formula (I) exhibiting an inhibitory activity of calpains and/or a trapping activity of reactive forms of oxygen.
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Page/Page column 7
(2009/01/24)
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- Formation of DMSO and DMF radicals with minute amounts of base
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So far overlooked DMSO and DMF form long-lived radicals in the presence of small amounts of bases, DMF radicals being less stable than DMSO radicals. In solvent mixtures, the presence of DMSO prolonged the lifetime of DMF radicals. The occurrence of radic
- ?pstad, Christer L.,Mel?, Thor-Bernt,Sliwka, Hans-Richard,Partali, Vassilia
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body text
p. 7616 - 7619
(2009/12/04)
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- PROCESS FOR PREPARING METHYL MERCAPTAN FROM DIALKYL SULPHIDES AND DIALKYL POLYSULPHIDES
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A process for continuously preparing methyl mercaptan by reacting a reactant mixture which contains a dialkyl sulphide and a dialkyl polysulphide with hydrogen sulphide to give methyl mercaptan.
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Page/Page column 2; 3
(2008/12/08)
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- Process for preparing alkyl mercaptans in a multizone fixed bed reactor
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The invention relates to a process for preparing alkyl mercaptans by catalytic gas phase reaction of alkanols and hydrogen sulphide over alkali metal tungstates, the reaction being performed in at least two successive reaction zones which contain catalysts of different activity and selectivity.
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Page/Page column 5
(2008/06/13)
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- PROCESS FOR CONTINUOUSLY PREPARING METHYL MERCAPTAN FROM CARBON- AND HYDROGEN-CONTAINING COMPOUNDS
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Provided is a process for continuously preparing methyl mercaptan by reacting a reactant mixture comprising solid, liquid and/or gaseous carbon- and/or hydrogen-containing compounds with air or oxygen, and/or water and sulfur.
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Page/Page column 4-5
(2009/01/20)
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- Graded Catalyst Bed for Methyl Mercaptan Synthesis
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A process and graded catalyst bed for selectively producing methyl mercaptan from methanol. The methanol is reacted with hydrogen sulfide, in the presence of a graded catalyst bed containing at least three types of nickel or cobalt molybdenum alumina catalysts to convert the methanol to methyl mercaptan in one-pass. At least one of the hydrotreating catalysts can contain aluminium phosphate. Use of the graded catalyst bed prevents the formation of a hot spot within the graded catalyst bed. The methyl mercaptan having less than about 30 wt. % unreacted methanol contained therein.
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Page/Page column 5-8
(2008/12/07)
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- CATALYST FOR THE PREPARATION OF METHYL MERCAPTAN
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The present invention refers to a catalyst for the manufacture of methyl mercaptan from carbon oxides comprising Mo and K compounds and oxides or sulfides of metals chosen from the manganese group. The improvement of the present process consists of the fact that carbon dioxide can be converted with higher conversions and selectivities to methyl mercaptan as compared to state-of-the-art technologies, with only minor amounts of carbon monoxide being formed as side product. Simultaneously, carbon monoxide can be easily converted into carbon dioxide and hydrogen by reaction with water using established water-gas-shift-technologies thus increasing the overall selectivity to methyl mercaptan.
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Page/Page column 6
(2008/12/04)
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- Determination and isolation of a thioesterase from passion fruit (Passiflora edulis Sims) that hydrolyzes volatile thioesters
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Volatile organosulfur compounds (VOSCs) are high impact aroma chemicals characteristic of tropical fruits which are active as both free thiols and the respective thioesters. Using a simple and sensitive colorimetric enzyme assay, a thioesterase activity toward VOSCs has been identified in ripening purple passion fruit (Passiflora edulis Sims). The assay was based on determining the release of free thiols from 2-methyl-3-furanthiol acetate using Ellman's reagent. The major thioesterase in the fruit was found to be a wall-bound protein in the mesocarp. The extracted enzyme activity was purified 150-fold and shown to be associated with a 43 kDa monomeric serine hydrolase which was selectively labeled with a fluorophosphonate suicide probe. MS-MS sequencing identified the thioesterase as a class 13 glycoside hydrolase, most similar to pectin acetylesterase, an enzyme involved in cell wall modifications in the peel of a number of fruit. Our results suggest that cell wall hydrolases in tropical fruit may have additional useful roles in biotransforming VOSCs.
- Tapp, Edward J.,Cummins, Ian,Brassington, David,Edwards, Robert
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experimental part
p. 6623 - 6630
(2010/04/06)
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- Catalyst for the production of methyl mercaptan from methanol and hydrogen sulfide
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The invention relates to a catalyst for the synthesis of methyl mercaptan from hydrogen sulfide and methanol and to a process for preparing methyl mercaptans. The catalyst comprises active aluminum oxide on which an alkali metal tungstate and ammonium salts have been deposited.
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Page/Page column 3-4
(2008/06/13)
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