- Electromediators based on the Ni(II) and Cr(III) complexes with the redox-active ligands in the synthesis of sulfur-containing organic compounds
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The chromium(III) tris-o-semiquinolate complex Cr(LSQ) 3 (LSQ is 3,6-di-tert-butyl-o-semiquinone) and the monoanionic paramagnetic nickel(II) complex [n-Bu4N][Ni(L S SQ)(L S DT)] (L S SQ is o-thiosemiquinone, L S DT is benzene-1,2-dithiolate) are considered as electromediators of hydrogen sulfide oxidation in the presence of various organic substrates (hex-1-ene, oct-1-ene, benzene, toluene, and benzoic acid). It is revealed that the electrolysis of hydrogen sulfide at the oxidation potential of the mediators in the presence of the substrates affords the corresponding aliphatic and aromatic thiols in a yield of 62-75%.
- Okhlobystin,Smolyaninov,Okhlobystina,Berberova,Koldaeva, Yu. Yu.,Abdulaeva
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- Insight into the Mechanism of Reversible Ring-Opening of 1,3-Benzoxazine with Thiols
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The reversible ring-opening addition and fragmentation reaction of p-cresol-based N-phenylbenzoxazine with aliphatic and aromatic thiols was investigated in solvent-mediated and solvent-free reactions. Independently of the used thiol, N-phenylbenzoxazine and the thiols reacted to equilibrium with comparable amounts of reactants and products in aprotic solvent, whereas in protic solvent almost full conversions were reached. In contrast, thiol reactivity was a crucial factor in solvent-free reactions yielding fast and complete conversions for a more acidic thiol and balanced equilibrium concentrations in case of thiols with high pKa values. The strong influence of thiols with low pKa values emphasizes the relevance of the protonation step in the ring-opening reactions of 1,3-benzoxazines with thiols in absence of solvents where acidity predominates nucleophilicity. The reverse reactions, namely adduct dissociation and benzoxazine recovery, were successfully conducted at elevated temperatures and reduced pressure facilitated by the removal of the formed thiols yielding up to 95% recovered 1,3-benzoxazine. These results provide deeper understanding of the reversible ring-opening reaction mechanism of 1,3-benzoxazine with thiols.
- Urbaniak, Tobias,Soto, Marc,Liebeke, Manuel,Koschek, Katharina
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- New organic single crystal of (benzylthio)acetic acid: Synthesis, crystal structure, spectroscopic (ATR-FTIR, 1H and 13C NMR) and thermal characterization
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(Benzylthio)acetic acid (Hbta) was synthesized with 78% yield from benzyl chloride and thiourea as substrates. Well-shaped crystals of Hbta were grown by slow solvent evaporation technique from pure methanol. The compound was investigated by single-crystal X-ray and powder diffraction techniques and was also characterized by other analytical methods, like ATR-FTIR, 1H and 13C NMR and TG/DSC. The acid molecule adopts bent conformation in the solid state. The crystal structure of Hbta is stabilized by numerous intermolecular interactions, including O-H···O, C-H···O, C-H···S and C-H···π contacts. Thermal decomposition of the obtained material takes place above 150 °C.
- Sienkiewicz-Gromiuk, Justyna,Tarasiuk, Bogdan,Mazur, Liliana
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- Synthesis of thiols via palladium catalyzed methanolysis of thioacetates with borohydride exchange resin
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Various thiols are prepared quantitatively from the corresponding thioacetates via Pd catalyzed methanolysis with borohydride exchange resin under a mild and neutral conditions. One-pot synthesis of thiols from alkyl halides through the formation of alkyl thioacetates using thioacetate exchange resin followed by methanolysis is also described.
- Choi,Yoon
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- Tris(3-hydroxypropyl)phosphine (THPP): A mild, air-stable reagent for the rapid, reductive cleavage of small-molecule disulfides
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Tris(3-hydroxypropyl)phosphine (THPP) is demonstrated to be a versatile, water-soluble and air-stable reducing agent, allowing for the rapid, irreversible reductive cleavage of disulfide bonds in both aqueous and buffered aqueous-organic media. The reagent shows exceptional stability at biological pH under which condition it permits the rapid reduction of a wide range of differentially functionalized small-molecule disulfides.
- McNulty, James,Krishnamoorthy, Venkatesan,Amoroso, Dino,Moser, Michael
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- Template effects of vesicles in dynamic covalent chemistry
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Vesicle lipid bilayers have been employed as templates to modulate the product distribution in a dynamic covalent library of Michael adducts formed by mixing a Michael acceptor with thiols. In methanol solution, all possible Michael adducts were obtained in similar amounts. Addition of vesicles to the dynamic covalent library led to the formation of a single major product. The equilibrium constants for formation of the Michael adducts are similar for all of the thiols used in this experiment, and the effect of the vesicles on the composition of the library is attributed to the differential partitioning of the library members between the lipid bilayer and the aqueous solution. The results provide a quantitative approach for exploiting dynamic covalent chemistry within lipid bilayers. This journal is
- Bravin, Carlo,Hunter, Christopher A.
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- Hydrolysis and aminolysis of alkyl xanthate esters and cellulose analogues
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The hydrolysis and aminolysis of a series of S-substituted O-alkylxanthate esters was studied in 20% v/v aqueous methanol at 35°C. The pH-rate profiles of the hydrolyses showed water and hydroxide-ion-catalyzed reactions. The reaction of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) and p-nitrobenzyl cellulose xanthate (CelXNB) with polyalanine and lysozyme produced a covalent bond between the polypeptide and the cellulose matrix, as shown by solid-state 13C NMR. However, the nature of the bonding could not be identified. The reaction of nucleophiles (H2O, OH-, RNH2) and xanthic esters was consistent with an addition-elimination mechanism through a tetrahedral intermediate. Bronsted plots against the pKa of the nucleophile (βnu) or the nucleofuge of the substrate (βlg) were used to characterize the rate-determining step. The pKa values of the nucleophiles ranged between -1.74 and 15.74, and for the nucleofuges, they were in the range of 10.50-0.92. For nucleophiles with pKa values up to about 10, βlg was 0.10-0.15, and βnu changed from 0.48 to 0.35 for the strongest electron-withdrawing nucleofuge. It was concluded that the water-catalyzed hydrolyses, and also aminolyses with moderately basic amines, occur with rate-determining formation of the tetrahedral intermediate. For strong bases such as hydroxide ion, the disappearance of the intermediate becomes the slowest step. The reaction of cellulose xanthic esters with external nucleophiles as hydroxide ion and amines shows simple first-order kinetics and is slower than alkyl or sugar xanthates, probably due to the diffusion effect through the tight cybotactic region of cellulose.
- Humeres, Eduardo,Soldi, Valdir,Klug, Marilene,Nunes, Mauricea,Oliveira, Celia M.S.,Barrie, Patrick J.
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- Thermal reactions of dibenzyl disulfide and dibenzyl sulfide with metals: A new route to trans-stilbene and dibenzyl
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A procedure was developed for preparing stilbene by thermal desulfuring of dibenzyl disulfide and dibenzyl sulfide with metals (Fe, Zn). The major product of the similar reaction of dibenzyl disulfide with copper is dibenzyl.
- Voronkov,Panova,Timokhina,Gromkova
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- New Birch Type Reduction. Halogen or Halides-Activated Reduction of Disulfides to Thiols with Aluminium in Liquid Ammonia
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Aromatic and aliphatic disulfides were reduced to the corresponding thiols in high yields by new halogen or halides-activated Birch type reduction with aluminium in liquid ammonia.
- Sato, Ryu,Akaishi, Ryouichi,Goto, Takehiko,Saito, Minoru
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- Cyclic Sulfenyl Thiocarbamates Release Carbonyl Sulfide and Hydrogen Sulfide Independently in Thiol-Promoted Pathways
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Hydrogen sulfide (H2S) is an important signaling molecule that provides protective activities in a variety of physiological and pathological processes. Among the different types of H2S donor compounds, thioamides have attracted attention due to prior conjugation to nonsteroidal anti-inflammatory drugs (NSAIDs) to access H2S-NSAID hybrids with significantly reduced toxicity, but the mechanism of H2S release from thioamides remains unclear. Herein, we reported the synthesis and evaluation of a class of thioamide-derived sulfenyl thiocarbamates (SulfenylTCMs) that function as a new class of H2S donors. These compounds are efficiently activated by cellular thiols to release carbonyl sulfide (COS), which is quickly converted to H2S by carbonic anhydrase (CA). In addition, through mechanistic investigations, we establish that COS-independent H2S release pathways are also operative. In contrast to the parent thioamide-based donors, the SulfenylTCMs exhibit excellent H2S releasing efficiencies of up to 90percent and operate through mechanistically well-defined pathways. In addition, we demonstrate that the sulfenyl thiocarbamate group is readily attached to common NSAIDs, such as naproxen, to generate YZ-597 as an efficient H2S-NSAID hybrid, which we demonstrate releases H2S in cellular environments. Taken together, this new class of H2S donor motifs provides an important platform for new donor development.
- Pluth, Michael D.,Steiger, Andrea K.,Zhao, Yu
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- Microwave-assisted synthesis of thioamides with elemental sulfur
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Thioamides are prepared in moderate-to-good yields from the benzylamines or benzylamine derivatives by treatment with elemental sulfur under microwave and solvent-free conditions at 170.C in 15 min.
- Milen, Matyas,Abranyi-Balogh, Peter,Dancso, Andras,Keglevich, Gyoergy
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- Novel Alkylation with Tetrathiotungstates and Tetrathiomolybdates: Facile Synthesis of Disulfides from Alkyl Halides
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A novel reaction of alkyl halides with piperidinium tetrathiotungstate or piperidinium tetrathiomolybdate (MS42-) has been found to afford disulfides in good to excellent isolated yields under very mild reaction conditions.
- Dhar, Preeti,Chandrasekaran, Srinivasan
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- Direct synthesis of thioethers from sulfonyl chlorides and activated alcohols
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An efficient, safe one-pot synthesis of thioethers from aromatic sulfonyl chlorides and activated alcohols has been developed under non-aqueous conditions.
- Martin, Michael T,Thomas, Alford M,York, Douglas G
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- The unexpected desulfurization of 4-aminothiophenols
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Thermolysis of 4-aminophenyl benzyl sulfide at 523 K in the hydrogen donor solvent (HDS), 9,10-dihydroanthracene (AnH2), gave 4-aminothiophenol and toluene as the predominant products of the homolytic S-C bond cleavage. Under these conditions, a portion of the 4-aminothiophenol was desulfurized to aniline with first-order kinetics and with a rate constant estimated by kinetic modeling to be 7.0 × 10-6 s-1. Starting with 4-NH2C6H4SH at 523 K, it was found that sulfur loss was more efficient in the non-HDSs, anthracene and hexadecane, than in AnH2. Under similar (competitive) reaction conditions, YC 6H4SHs with Y = H, 4-CN, and 3-CF3 were completely inert; with Y = 4-CH3O, there was some very minor desulfurization, whereas with Y = 4-N(CH3)2 and 4-N(CH3)(H), the sulfur extrusions were as fast as that for Y = 4-NH2. We tentatively suggest that this apparently novel reaction is a chain process initiated by the bimolecular formation of diatomic sulfur, S2, followed by a reversible addition of ground state, triplet 3S2 to the thiol sulfur atom, 4-NH2C 6H4S↑(SS↑)H, and insertion into the S-H bond, 4-NH2C6H4SSSH. In a cascade of reactions, aniline and S8 are formed with the chains being terminated by reaction of 4-NH2C6H4S↑(SS↑)H with 4-NH2C6H4SH. Such a reaction mechanism is consistent with the first-order kinetics. That this reaction is primarily observed with 4-YC6H4SH having Y = N(CH3) 2, N(CH3)(H), and NH2 is attributed to the fact that these compounds can exist as zwitterions.
- Mulder, Peter,Mozenson, Olga,Lin, Shuqiong,Ingold
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- Dicobalt Octacarbonyl Catalyzed Conversion of Benzylic Alcohols to Thiols, Hydrocarbons, and Esters Using Hydrogen Sulfide and Carbon Monoxide
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The first examples of a homogeneous, metal complex catalyzed conversion of alcohols to thiols are reported, using hydrogen sulfide and catalytic quantities of dicobalt octacarbonyl.If ethanol is employed as one of the components of the reaction medium, th
- Alper, Howard,Sibtain, Fazle
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- Biomimetic thiolate alkylation with zinc pyrazolylbis(thioimidazolyl)borate complexes
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The NS2ZnX coordination in thiolate-alkylating zinc enzymes is reproduced in (tripod)ZnX complexes with substituted pyrazolylbis(thioimidazolyl)borate tripod ligands. Intermediate (tripod)Zn nitrates and perchlorates are converted into (tripod) Zn thiolates, including the biologically relevant homocysteinate. Methylation with CH3I converts these to (tripod)ZnI and the corresponding thioethers CH3SR, including methionine. A kinetic investigation has shown the alkylations to be intramolecular SN2 processes that take place at the zinc-bound thiolates. They are considerably faster for the (NS2)Zn thiolates than for the (N2S)- and (N3)Zn-thiolates with similar pyrazolylborate-derived tripod ligands, in agreement with Nature's choice of an NS2 donor set for zinc. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Ibrahim, Mohamed M.,He, Guosen,Seebacher, Jan,Benkmil, Boumahdi,Vahrenkamp, Heinrich
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- Phosphorus pentasulfide mediated conversion of organic thiocyanates to thiols
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In this paper we report an efficient and mild procedure for the conversion of organic thiocyanates to thiols in the presence of phosphorus pentasulfide (P2S5) in refluxing toluene. The method avoids the use of expensive and hazardous transition metals and harsh reducing agents, as required by reported methods, and provides an attractive alternative to the existing methods for the conversion of organic thiocyanates to thiols.
- Maurya, Chandra Kant,Mazumder, Avik,Gupta, Pradeep Kumar
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- A rapid and efficient cleavage of organic disulfides to mercaptans using ZrCl4/NaBH4
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A practical and cheaper reagent system ZrCl/NaBH4 is used for the reductive cleavage of organic disulfides to mercaptans under mild conditions, in excellent yields.
- Purushothama Chayr,Rajaram,Iyengar
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- A Novel Transformation of Alcohols to Thiols
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Treatment of alcohols with 2,4-bis(p-methoxyphenyl)-1,3-dithiaphosphetane-2,4-disulphide (Lawesson reagent) gave the corresponding thiols.
- Nishio, Takehiko
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- Rate and Equilibrium Constants for the Reaction of Thiolate Ions with Dibenzo-1,2-dithiin and Naphtho-1,2-dithiole 1,1-Dioxides
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In aqueous dioxane the cyclic thiosulfonate dibenzo-1,2-dithiin 1,1-dioxide (1) reacts rapidly with thiolate ions and undergoes opening of the thiosulfonate ring (eq 2), forming disulfide 3a.Acidification of solutions of 3a with carboxylic acid buffers of appropiate pH leads to facile reversal of ring-opening reaction and the quantitative regeneration of 1.Since this reversal of ring opening is not acid-catalyzed, it must take place via a simple intramolecular displacement of RS- by the sulfinate (SO2-) group present in 3a and is therefore the microscopic reverse of the ring-opening reaction.Rate constants have been determined for both ring opening (kRS) and reversal of ring opening (k-RS) for a series of alkanethiolates of varying pKa.From these data one may also calculate the equilibrium constant, Keq(=kRS/k-RS), for reaction of each thiolate with 1.From comparison of the log Keq's with previously determined equilibrium constants for reaction of cyanide and sulfite ions with 1 one obtains quantitative information on the thermodynamics of reactions of the type ArSSR + CN- = ArSCN + RS- and ArSSR + SO32- = ArSSO3- + RS- that should be of considerable value for predicting the magnitude of equilibrium constants for cyanide-disulfide and sulfite-disulfide equilibria.Plots of log Keq, log KRS, and log k-RS vs. the pKa of RSH reveal that βeq=1.25, βRS=0.26, and β-RS=-0.99.These β values show that the transition state for eq 2 is quite unsymmetrical, with a structure Δ-...S-SO2δ-> where the RS-S bond is only ca. 20percent formed.The βRS and β-RS values are compared with the β values for several other previously studied displacements involving disulfides.The reaction of naphthol-1,2-dithiole 1,1-dioxide (2) with thiolates behaves in a fashion analogous to that of the reaction of RS- with 1.Comparison of Keq, kRS, and k-RS for an equilibrium involving 2 and a thiolate with those for the corresponding thiolate reacting with 1 allows one to assess how a change from a six- to a five-membered thiosulfonate ring influences Keq, kRS, and k-RS.The major effects are that k-RS is much larger and Keq is considerably smaller.
- Boduszek, Bogdan,Kice, John L.
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- The First Practical Method of Selective Heteroatom-Directed Chlorohydroxylation
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A new Pd(II)-catalyzed nucleophilic chlorohydroxylation reaction of allylic amines and sulfides was achieved, and the regioselective reaction gives high yields of the chlorohydrin products, which can be transformed into epoxy compounds or aziridine compou
- Lai, Jin-Yu,Wang, Fu-Song,Guo, Guang-Zhong,Dai, Li-Xin
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- Solid Supported Reagents and Reactions. Part 21.1 Rapid and Clean Synthesis of Thiols from Halides Using Polymer-supported Hydrosulfide
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A variety of thiols are prepared from corresponding halides using polymer-supported hydrosulfide in excellent yields. Isolation of pure products by simple filtration and evaporation is an important feature of this method.
- Bandgar, Babasaheb P.,Pawar, Sanjay B.
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- A preparative scale reduction of alkyl disulfides with tributyl phosphine and water
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A series of alkyl disulfides has been shown to be reduced by tributyl phosphine at room temperature. The resulting thiols were then acylated in the same pot and isolated in good yields. This sequence is convenient and is a practical option for the preparation of gram quantities of thiol or thioester from the corresponding disulfide.
- Ayers, Joshua T.,Anderson, Shelby R.
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- Silylating Disulfides and Thiols with Hydrosilicones Catalyzed by B(C6F5)3
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Hydrosilanes and silicones, catalyzed with B(C6F5)3, may be used to silylate thiols or cleave disulfides giving silyl thio ethers. Alcohols were found to react faster than thiols or disulfides, while alkoxysilanes (the Piers-Rubinsztajn reaction) were slower such that the overall order of reactivity was found to be HO>HS>SS>SiOEt. The resulting silane and silicone-protected thio ethers produced from the sulfur-based functional groups could be cleaved to thiols using alcohols or mild acid with rates that depend on the steric bulk of the siloxane.
- Brook, Michael A.,Liao, Mengchen,Zheng, Sijia
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- A NEW, HIGHLY EFFICIENT METHOD FOR THE CONVERSION OF ALCOHOLS TO THIOLESTERS AND THIOLS
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Various alcohols were converted to their corresponing thiolacetates by treatment with triphenylphosphine and diisopropyl azodicarboxylate in the presence of thiolacetic acid.The overall conversion was both highly efficient (89-99percent yields) and stereoselective (99.5percent inversion).
- Volante, R. P.
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- Hydrophobic polymer-supported catalyst for organic reactions in water: Acid-catalyzed hydrolysis of thioesters and transprotection of thiols
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(Matrix presented) A hydrophobic polystyrene-supported sulfonic acid was found to be effective for hydrolysis of thioesters in pure water. It was revealed that the catalyst was much superior to other Bronsted acid catalysts. Transprotection of thiols from thioesters to thioethers has been successfully performed in water using this catalytic system.
- Iimura, Shinya,Manabe, Kei,Kobayashi, Shu
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- Phosphorus Pentasulfide Mediated Conversion of Primary Carbamates into Thiols
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In this paper, we report a method for the conversion of primary carbamates into thiols in the presence of phosphorus pentasulfide (P 2 S 5) in refluxing toluene. Presently, no method exists in the literature for conversion of carbamates into thiols and, to the best of our knowledge, it is the first report for this type of conversion. This method presents an indirect route for the conversion of alcohols into thiols via their carbamate derivatives that may be useful in the total synthesis of compounds containing a thiol functionality.
- Maurya, Chandra Kant,Gupta, Pradeep Kumar
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- Mild and efficient methods for the conversion of benzylic bromides to benzylic thiols
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Very mild and efficient methods are established for the conversion of the benzylic bromides at room temperature to their corresponding benzylic thiols with high yields (94-99%) in 1 h under N2.
- Han, Chien-Chung,Balakumar
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- Photoactive Metal-Organic Frameworks for the Selective Synthesis of Thioethers: Coupled with Phosphine to Modulate Thiyl Radical Generation
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Metal-organic framework (MOF) materials are intriguing photocatalysts to trigger radical-mediated chemical transformations. We report herein the synthesis and characterization of a series of isomorphic MOFs which show a novel structure, wide visible-light absorption, high chemical stability, and specific redox potential. The prepared MOFs were explored for the photoinduced single-electron oxidation of thiol compounds, generating reactive thiyl radicals to afford thioethers via a convenient thiol-olefin reaction. Importantly, we provide a widely applicable strategy by combing a photoactive MOF with phosphine to modulate the generation of thiyl radical in the reaction, thereby producing a single product of the thioether without the formation of a disulfide byproduct due to the dimerization of thiyl radicals. The photocatalytic reaction takes advantage of this strategy, showing great generality where tens of thiols and olefins have been examined as coupling partners. In addition, the strategy has also been demonstrated to be effective for the reactions catalyzed by other MOFs. Mechanism studies reveal that the selective synthesis of C-S products relies on a synergy between the photoinduced generation of a thiyl radical over the MOF and the in situ cleavage of S-S bond into a S-H bond by phosphine. It is notable that the synthesized MOFs show advanced performance in comparison with classical MOFs. The work not only provides a series of novel MOF photocatalysts that are capable of photoinduced thiol-olefin coupling but also indicates the great potential of MOFs for photochemical transformations mediated by reactive radicals.
- Guo, Zhifen,Liu, Xin,Bai, Rong,Che, Yan,Chi, Yanhong,Guo, Chunyi,Xing, Hongzhu
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supporting information
p. 8672 - 8681
(2021/06/28)
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- METHOD FOR PRODUCING TRICHLOROSILYLSULFIDE ANION AND ITS USE IN THE PREPARATION OF ORGANOSULFUR COMPOUNDS
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Preparation of sulfur fine chemicals from sulfur sources is described.
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Paragraph 0105-0106
(2021/05/07)
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- Catalytic Hydrogenation of Thioesters, Thiocarbamates, and Thioamides
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Direct hydrogenation of thioesters with H2 provides a facile and waste-free method to access alcohols and thiols. However, no report of this reaction is documented, possibly because of the incompatibility of the generated thiol with typical hydrogenation catalysts. Here, we report an efficient and selective hydrogenation of thioesters. The reaction is catalyzed by an acridine-based ruthenium complex without additives. Various thioesters were fully hydrogenated to the corresponding alcohols and thiols with excellent tolerance for amide, ester, and carboxylic acid groups. Thiocarbamates and thioamides also undergo hydrogenation under similar conditions, substantially extending the application of hydrogenation of organosulfur compounds.
- Luo, Jie,Rauch, Michael,Avram, Liat,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 21628 - 21633
(2021/01/11)
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- THIOL COMPOUND PRODUCTION METHOD AND NOVEL THIATING AGENT
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PROBLEM TO BE SOLVED: To provide: a thiol compound production method which allows selective production of a thiol compound of interest, inhibits production of by-products ending up wastes, is excellent in production efficiency, and can reduce production costs; and a novel thiating agent used for the method. SOLUTION: The thiol compound production method comprises: a step 1 of preparing a thiuronium salt by reacting at least one compound represented by the general formula (1) defined by R-(X)m with a thiating agent comprising at least one compound selected from compounds represented by the general formula (2) in the figure; and a step 2 of hydrolyzing the thiuronium salt to prepare a compound represented by the general formula (3) defined by R-(SH)m. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0070
(2019/12/25)
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- Orthophosphate and Sulfate Utilization for C-E (E = P, S) Bond Formation via Trichlorosilyl Phosphide and Sulfide Anions
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Reduction of phosphoric acid (H3PO4) or tetra-n-butylammonium bisulfate ([TBA][HSO4]) with trichlorosilane leads to the formation of the bis(trichlorosilyl)phosphide ([P(SiCl3)2]-, 1) and t
- Geeson, Michael B.,Ríos, Pablo,Transue, Wesley J.,Cummins, Christopher C.
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supporting information
p. 6375 - 6384
(2019/05/02)
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- Metal-Sulfide Catalysts Derived from Lignosulfonate and their Efficient Use in Hydrogenolysis
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Catalytic lignosulfonate valorization is hampered by the in situ liberation of sulfur that ultimately poisons the catalyst. To overcome this limitation, metal sulfide catalysts were developed that are able to cleave the C?O bonds of lignosulfonate and are
- Liu, Sijie,van Muyden, Antoine P.,Bai, Lichen,Cui, Xinjiang,Fei, Zhaofu,Li, Xuehui,Hu, Xile,Dyson, Paul J.
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p. 3271 - 3277
(2019/06/17)
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- Synergistic Effects of ppm Levels of Palladium on Natural Clinochlore for Reduction of Nitroarenes
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Augmenting the modified naturally occurring clay clinochlore with ppm amounts of palladium leads to a new and very effective reagent for the reduction of numerous aromatic nitro species. When palladium nanoparticles are supported on pyridyltriazole-modified clinochlore, iron within clinochlore acts synergistically with palladium to catalyze the reduction of a wide variety of nitroarenes at room temperature in aqueous media. Based on E-factor calculations, the catalyst system is found to be in line with green chemistry standards and can be recycled up to five times.
- Gholinejad, Mohammad,Oftadeh, Erfan,Shojafar, Mohammad,Sansano, José M.,Lipshutz, Bruce H.
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p. 4240 - 4248
(2019/09/06)
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- Nonenzymatic Dynamic Kinetic Resolution of in situ Generated Hemithioacetals: Access to 1,3-Disubstituted Phthalans
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The first nonenzymatic DKR reaction of hemithioacetals is developed. Hemithioacetals were formed in situ via thiol addition and subsequently underwent an intramolecular oxa-Michael reaction. The scope of the reaction was quite broad ranging from aliphatic to aromatic substituents and 1,3-disubstituted-1,3-dihyroisobenzofuran products were obtained in good yields with moderate diastereoselectivities and high enantioselectivities. (Figure presented.).
- Nath, Utpal,Chowdhury, Deepan,Pan, Subhas Chandra
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p. 1628 - 1633
(2018/03/21)
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- Benzylic Thio and Seleno Newman-Kwart Rearrangements
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The thermally induced OBn → SBn and OBn → SeBn migration reactions facilitate the rearrangement of O-benzyl thio- and selenocarbamates [BnOC(=X)NMe2] (X = S or Se) into their corresponding S-benzyl thio- and Se-benzyl selenocarbamates [BnXC(=O)NMe2] (X = S or Se). A series of substituted O-benzyl thio- and selenocarbamates were synthesized and rearranged in good yields of 33-88%. The reaction rates are higher for substrates with electron-donating groups in the 2 or 4 position of the aromatic ring, but the rearrangement also proceeds with electron-withdrawing substituents. The rearrangement follows first-order reaction kinetics and proceeds via a tight ion pair intermediate consisting of the benzylic carbocation and the thio- or selenocarbamate moiety. Computational studies support these findings.
- Eriksen, Kristina,Ulfkj?r, Anne,S?lling, Theis I.,Pittelkow, Michael
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p. 10786 - 10797
(2018/09/06)
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- Method for producing thionocarbamate and dibenzyl disulfide
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The invention discloses a method for producing thionocarbamate and dibenzyl disulfide. The method comprises the following steps: carrying out an esterification reaction on alkyl xanthate and benzyl halide to obtain alkyl benzyl xanthate; carrying out an aminolysis reaction on the alkyl benzyl xanthate and fatty amine to obtain a thionocarbamate and benzyl mercaptan mixture; and carrying out an oxidation reaction on the thionocarbamate and benzyl mercaptan mixture and hydrogen peroxide, and carrying out liquid-solid separation to obtain a solid which is the dibenzyl disulfide product and a liquid, and allowing the liquid to stand for oil and water layering in order to obtain an oil phase which is the thionocarbamate product. The dibenzyl disulfide product and thionocarbamate product obtained through the method have high yield and high purity, and the method has the advantages of easiness in separation of the products in the preparation process, environmental protection, high atom economy property, low production cost, and easiness in realization of industrial production.
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- Method for preparing thionocarbamate and trithiocarbonate
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The invention discloses a method for preparing thionocarbamate and trithiocarbonate. The method comprises the following steps: carrying out an esterification reaction on alkyl xanthate salt and a halogenation reagent to obtain alkyl xanthate ester; carrying out an aminolysis reaction on the alkyl xanthate ester and fatty amine to obtain a thionocarbamate and mercaptan compound mixture; and carrying out an addition reaction on the thionocarbamate and mercaptan compound mixture and carbon disulfide in the presence of caustic alkali, and carrying out solid-liquid separation to obtain a liquid phase which is the thionocarbamate product and a solid phase which is the trithiocarbonate product. The products prepared through the preparation method have high yield and high purity, and the method allows the two high-efficiency collectors comprising thionocarbamate and trithiocarbonate to be simultaneously produced, and has the advantages of easiness in separation of the products, high atom economy property, low production cost, and easiness in realization of industrial production.
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- Method for preparing sulfhydryl compounds by hydroxyl substitution and sulfhydryl compounds
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The invention provides a method for preparing sulfhydryl compounds by hydroxyl substitution and the sulfhydryl compounds. According to the method, low-cost and easily-obtained benzene or fused ring compounds with phenolic hydroxyl groups or benzyl hydroxyl substituents serving as raw materials to react with the raw materials such as inorganic sulfide under the catalysis conditions to prepare the corresponding sulfhydryl compounds. The method has the advantages that the preparation method is simple, convenient and rapid, low in cost, mild in reaction condition, high in reaction site selectivity and high in yield, a post-processing process is simple, and no pollution is caused.
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Paragraph 0070; 0071; 0072
(2017/06/02)
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- Copper(I)-Catalyzed Alkyl- and Arylsulfenylation of 3,4-Dihalo-2(5H)-furanones (X=Br, Cl) with Sulfoxides under Mild Conditions
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An efficient copper(I)/proline sodium salt-catalyzed alkyl- and arylsulfenylation of C(sp2)–X 3,4-dihalo-2(5H)-furanone compounds with sulfoxides is described. For inexpensive C(sp2)–Cl compounds, there is also a satisfactory reactivity with the moderate yields. This transformation provides a novel approach for the utilization of sulfoxides (not only DMSO) as sulfur source at mild temperatures without the need for an anaerobic atmosphere. More importantly, both sulfoxide and proline sodium salt can play a dual role in this reaction. (Figure presented.).
- Cao, Liang,Luo, Shi-He,Wu, Han-Qing,Chen, Liu-Qing,Jiang, Kai,Hao, Zhi-Feng,Wang, Zhao-Yang
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p. 2961 - 2971
(2017/09/08)
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- A practical non-metal catalytic silicon of the amino protection of the new method (by machine translation)
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The invention relates to a high efficiency, mild organic silicon reagent carbon silicon key fracture of the new method. The method of this reaction to the alkali is cheap and easy to obtain metal catalyst, in order to common commercial solvent as a reaction solvent and a hydrogen source, in the air and in the under mild conditions can be successfully catalytic trimethyl aryl silicon reagent or aryl alkyne base silicon reagent selectively generating carbon silicon key cracking hydrogenation reaction, the substrate universality is wide, functional group compatibility outstanding. The first innovative to realize the non-transition metal catalyzed carbon silicon key breaking reaction, also overcome the traditional method requires the use of greatly excessive inorganic alkali or an expensive metal catalyst to the limitation of the silicon of the amino protection, for the laboratory preparation and industry in the production of the organosilicon group deprotection provides a completely new strategy. (by machine translation)
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Paragraph 0032; 0033
(2018/04/01)
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- Efficient Generation of C–S Bonds via a By-Product-Promoted Selective Coupling of Alcohols, Organic Halides, and Thiourea
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A metal- and base-free three-component coupling of alcohols, heteroaryl halides, and thiourea has been developed for direct and selective synthesis of heteroaryl thioethers. This method can be easily scaled up to the gram scale and extended to dialkyl thioethers, heteroaryl selenides, benzothiazoles, and some antimycobacterially-active thioethers. Mechanistic studies revealed that a by-product-promoted in situ C–O activation of alcohols to more reactive alkyl halides and slow release of the thiol and alkyl halide intermediates are the key to the high selectivity and success of the reaction. (Figure presented.).
- Ma, Xiantao,Yu, Lei,Su, Chenliang,Yang, Yaqi,Li, Huan,Xu, Qing
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supporting information
p. 1649 - 1655
(2017/05/29)
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- Two-step three-component process for one-pot synthesis of 8-alkylmercaptocaffeine derivatives
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A highly efficient, odourless and two-step three-component process for one-pot synthesis of some 8-alkylmercaptocaffeine derivatives has been described. The catalyst-free three-component reaction of alkyl bromides, thiourea, and 8-bromocaffeine gave 8-alkylmercaptocaffeine products in excellent to quantitative yields. In addition, the impact of parameters on sample reaction is discussed.
- Rad, M. N. Soltani,Maghsoudi
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p. 70335 - 70342
(2016/08/06)
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- Hemithioketal formation of vicinal tricarbonyl compound with thiols and their recovery
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In this paper, we report hemithioketal formation of diphenylpropanetrione (DPPT) with thiols and their recovery. Addition of thiols to the central carbonyl group occurred readily at ambient temperature to provide the thiol adducts of DPPT (DPPT–thiols), which has a hemithioketal structure. On the other hand, oxidizing DPPT–thiols with an oxidation reagent enabled successful recovery of DPPT, which indicated the reversible nature of this system.
- Yuki, Tatsuya,Yonekawa, Morio,Matsumoto, Kozo,Sei, Yoshihisa,Tomita, Ikuyoshi,Endo, Takeshi
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p. 4783 - 4788
(2016/07/18)
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- One-Pot Intermolecular C–S Self-Coupling of Dimethyl Sulfoxide Promoted by Molybdenum Pentachloride
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The reactions between MoCl5and 1–2 equiv. of a selection of sulfoxides at room temperature in dichloromethane as solvent were studied. The 1:1 molar reaction between MoCl5and dimethyl sulfoxide (DMSO) afforded the C–S coupling product [Me2SCH2SMe][MoOCl4] (1), which was isolated in 46 % yield and characterized by analytical and spectroscopic methods and by X-ray diffraction. MoOCl3, SMe2and HCl were identified as side products. The reactions between MoCl5and tetrahydrothiophene 1-oxide, nBu2SO, MePhSO or (PhCH2)2SO yielded the corresponding sulfides and, in the cases of (PhCH2)2SO and MePhSO, also C–S activation compounds. According to DFT calculations, the unusual formation of 1 is the consequence of thermodynamically feasible Cl/O interchange between MoCl5and DMSO, this being a prerequisite for successive C–H bond activation.
- Bortoluzzi, Marco,Ferretti, Eleonora,Hayatifar, Mohammad,Marchetti, Fabio,Pampaloni, Guido,Zacchini, Stefano
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p. 3838 - 3845
(2016/08/19)
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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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- Sulfur-and n-acyl carbonyl oxygen-assisted heterolysis of the C(=O)-S bond in excited-state (Z)-nacyl-α-dehydro(1-naphthyl)alanine thioesters
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Irradiation of the title thioesters (Z)-1 in nitrogen-saturated 1,2- dichloroethane at wavelengths greater than 280 nm was found to afford (Z)-4-(1- naphthylmethylene)-5(4H)-oxazolone derivatives (Z)-2, (E)-2, alkyl-substituted thiols 3, and (E)-1 without
- Hosoi, Yosuke,Igarashi, Tetsutaro,Sakurai, Tadamitsu
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p. 117 - 126
(2013/08/23)
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- Dependence of thermal stability on molecular structure of RAFT/MADIX agents: A kinetic and mechanistic study
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The thermal decomposition of different classes of RAFT/MADIX agents, namely dithioesters, trithiocarbonates, xanthates, and dithiocarbamates, were investigated through heating in solution. It was found that the decomposition behavior is complicated interplay of the effects of stabilizing Z-group and leaving R-group. The mechanism of the decomposition is mainly through three pathways, i.e., β-elimination, α-elimination, and homolysis of dithiocarbamate (particularly for universal RAFT agent). The most important pathway is the β-elimination of thiocarbonylthio compounds possessing β-hydrogen, leading to the formation unsaturated species. For the leaving group containing solely α-hydrogen, such as benzyl, α-elimination takes place, resulting in the formation of (E)-stilbene through a carbene intermediate. Homolysis occurs specifically in the case of a universal RAFT agent, in which a thiocarbonyl radical and an alkylthio radical are generated, finally forming thiolactone through a radical process. The stabilities of the RAFT/MADIX agents are investigated by measuring the apparent kinetics and activation energy of the thermal decomposition reactions. Both Z-group and R-group influence the stability of the agents through electronic and steric effects. Lone pair electron donating heteroatoms of Z-group show a remarkable stabilizing effect while electron withdrawing substituents, either in Z- or R-group, tends to destabilize the agent. In addition, bulkier or more β-hydrogens result in faster decomposition rate or lower decomposition temperature. Thus, the stability of the RAFT/MAIDX agents decreases in the order where R is (with identical Z = phenyl) -CH2Ph (5) > -PS (PS-RAFT 15) > -C(Me)HPh (2) > -C(Me)2C(=O)OC2H5 (7) > -C(Me)2Ph(1) > -PMMA (PMMA-RAFT 16) > -C(Me) 2CN (6). For those possessing identical leaving group such as 1-phenylethyl, the stability decreases in the order of O-ethyl (11) > -N(CH2CH3)2 (13) > -SCH(CH3)Ph (8) > -Ph (2) > -CH2Ph (4) > -PhNO2 (3). These results consort with the chain transfer acitivities measured by the CSIRO group and agree well with the ab initio theoretical results by Coote. In addition, the difference between thermal stabilities of the universal RAFT agents at neutral and protonated states has also been demonstrated.
- Zhou, Yanwu,He, Junpo,Li, Changxi,Hong, Linxiang,Yang, Yuliang
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experimental part
p. 8446 - 8457
(2012/03/12)
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- One-step synthesis of N-acetylcysteine and glutathione derivatives using the Ugi reaction
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Fully protected natural and unnatural N-acetylcysteine, dipeptide Cys-Gly, glutathione, and homoglutathione derivatives were synthesized by the Ugi four-component reaction using various benzylthio aldehydes and ketones as carbonyl building blocks. The scope and limitations of the method were investigated. Formation of imidazoline by-products in the Ugi reaction was discussed. 2,2,2-Trifluoroethanol was shown to be a superior reaction media than methanol in some reactions. Also, the 4-methyl-2,6,7-trioxabicyclo[2.2.2]octyl derivative (OBO-ester) of isocyanoacetic acid was shown to be superior to use than ethyl isocyanoacetate as a peptide synthesis precursor in cases when higher reactivity of an isocyanide is required.
- Zhdanko, Alexander G.,Gulevich, Anton V.,Nenajdenko, Valentine G.
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experimental part
p. 4692 - 4702
(2009/10/02)
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- Preparation and in-vitro evaluation of 4-benzylsulfanylpyridine-2- carbohydrazides as potential antituberculosis agents
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A set of 4-benzylsulfanylpyridine-2-carbohydrazides was synthesized and evaluated for in vitro antimycobacterial activity against Mycobacterium tuberculosis, non-tuberculous mycobacteria, and multidrug-resistant M. tuberculosis. The activities expressed as the minimum inhibitory concentration (MIC) fall into a range of 2 to 125 μmol/L, most often 4 to 32 μmol/L. The results revealed that the substituents on the benzyl moiety do not influence the antimycobacterial efficacy. The substances exhibited similar activities against sensitive and resistant strains of M. tuberculosis. Furthermore, compounds show low antiproliferative effect and cytotoxicity.
- Herzigova, Petra,Klimesova, Vera,Palat, Karel,Kaustova, Jarmila,Dahse, Hans-Martin,Moellmann, Ute
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body text
p. 394 - 404
(2009/11/30)
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- Probing the mechanism of electron capture and electron transfer dissociation using tags with variable electron affinity
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Electron capture dissociation (ECD) and electron transfer dissociation (ETD) of doubly protonated electron affinity (EA)-tuned peptides were studied to further illuminate the mechanism of these processes. The model peptide FQpSEEQQQTEDELQDK, containing a
- Sohn, Chang Ho,Chung, Cheol K.,Yin, Sheng,Ramachandran, Prasanna,Loo, Joseph A.,Beauchamp, J. L.
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experimental part
p. 5444 - 5459
(2009/09/25)
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- Facile conversion of dithioesters into carboxylic acids or esters using alkaline hydrogen peroxide
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Simple, mild, and environmentally friendly procedures for the direct conversion of dithioesters into either carboxylic acids or esters using hydrogen peroxide under alkaline conditions are described. Georg Thieme Verlag.
- Grellepois, Fabienne,Portella, Charles
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experimental part
p. 3443 - 3446
(2009/05/09)
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- Novel N,S-phenacyl protecting group and its application for peptide synthesis
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The phenacyl group can be introduced onto amino and thio groups by N,S-alkylation reactions. Conversely, these groups are removed rapidly by employing magnesium in acetic acid. This protecting group was successfully applied to a short peptide synthesis of Boc-L-Cys-Gly-OMe. Georg Thieme Verlag Stuttgart.
- Tang, Guo,Ji, Tao,Hu, An-Fu,Zhao, Yu-Fen
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experimental part
p. 1907 - 1909
(2009/04/11)
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- Thioacetate deprotection
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A method of thioacetate deprotection by providing a compound of the formula R1—S—CO—R2, and reacting the compound with a quaternary ammonium cyanide salt in the presence of a protic solvent in an inert atmosphere to convert the compound to a product of the formula R1—SH. R1 is an organic group in which the bonding to sulfur is through a saturated carbon, and R2 is an aliphatic group.
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- Electron transfer to sulfides and disulfides: Intrinsic barriers and relationship between heterogeneous and homogeneous electron-transfer kinetics
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The electron-acceptor properties of series of related sulfides and disulfides were investigated in N,N-dimethylformamide with homogeneous (redox catalysis) and/or heterogeneous (cyclic voltammetry and convolution analysis) electrochemical techniques. The electron-transfer rate constants were determined as a function of the reaction free energy and the corresponding intrinsic barriers were determined. The dependence of relevant thermodynamic and kinetic parameters on substituents was assessed. The kinetic data were also analyzed in relation to corresponding data pertaining to reduction of diaryl disulfides. All investigated reductions take place by stepwise dissociative electron transfer (DET) which causes cleavage of the Calkyl-S or S-S bond. A generalized picture of how the intrinsic electron-transfer barrier depends on molecular features, ring substituents, and the presence of spacers between the frangible bond and aromatic groups was established. The reduction mechanism was found to undergo a progressive (and now predictable) transition between common stepwise DET and DET proceeding through formation of loose radical anions. The intrinsic barriers were compared with available results for ET to several classes of dissociative- and nondissociative-type acceptors, and this led to verification that the heterogeneous and the homogeneous data correlate as predicted by the Hush theory.
- Meneses, Ana Belen,Antonello, Sabrina,Arevalo, Maria Carmen,Gonzalez, Concepcion Carmen,Sharma, Jadab,Wallette, Andrea N.,Workentin, Mark S.,Maran, Flavio
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p. 7983 - 7995
(2008/04/01)
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- Deacetylation of thioacetate using acetyl chloride in methanol
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A highly efficient method for the deacetylation of thioacetate is reported under mild acidic conditions employing acetyl chloride in methanol. Some of the major advantages are mild conditions, high efficiency, high yields, and easy operations. Copyright Taylor & Francis Group, LLC.
- Tewari, Neera,Nizar, Hashim,Mane, Avinash,George, Vinod,Prasad, Mohan
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p. 1911 - 1914
(2007/10/03)
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- Aliphatic thioacetate deprotection using catalytic tetrabutylammonium cyanide
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A series of thiol-functionalized organic compounds were selected to analyze the scope and efficiency of a new thioacetate deprotection method using catalytic tetrabutylammonium cyanide (TBACN) to effect the transformation of a thioacetate group to a free thiol in the presence of a protic solvent. Particularly attractive are the mild reaction and workup conditions, reduced byproduct formation typically seen using literature methods and yields of greater than 80% for the free aliphatic thiols. This method is effective on aliphatic thiols with trityl, benzyl, p-halo-benzyl, phenethyl, phenoxyethyl, and cyclohexylethyl structural moieties, but it is not effective with thiophenols.
- Holmes, Brian T.,Snow, Arthur W.
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p. 12339 - 12342
(2007/10/03)
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- Mechanisms of the hydrodenitrogenation of alkylamines with secondary and tertiary α-carbon atoms on sulfided NiMo/Al2O3
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The HDN of alkylamines with secondary and tertiary α-carbon atoms (2-pentylamine, 3-methyl-2-butylamine, 3,3-dimethyl-2-butylamine, 2-methylcyclohexylamine, 2-methyl-2-butylamine) and benzylamine and the HDS of corresponding alkanethiols were studied over sulfided NiMo/Al2O3. Alkanethiols and dialkylamines were primary products in the HDS of the amines with secondary products, formed from elimination and hydrogenolysis of the alkanethiols, as confirmed by the similar alkenes/alkane ratios in the HDN of the alkylamines and HDS of the corresponding alkanethiols. 2-Methyl-2-butylamine and benzylamine reacted much faster than the amines with secondary α-carbon atoms. Methylbutenes and methylbutane were the primary products of 2-methyl-2-butylamine, and toluene was the primary product of benzylamine. This and the different methylbutenes/methylbutane ratios in the HDS of 2-methyl-2-butylamine and HDS of 2-methyl-2-butanethiol indicated that 2-methyl-2-butylamine, with a tertiary α-carbon atom, and the activated benzylamine reacted by means of an E1 mechanism. The substitution of the NH2 group by H2S led to an alkanethiol and NH3 and, thus, to total denitrogenation. Substitution by an amine led to a dialkylamine and NH3 and to 50% nitrogen removal. High partial pressures of H2S and alkylamine increased the rate of transformation of alkylamine to alkanethiol and thus, of denitrogenation. However, the rate of sulfur removal from the alkanethiol decreased.
- Zhao,Prins
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p. 532 - 544
(2007/10/03)
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- Generation of thiols by biotransformation of cysteine-aldehyde conjugates with baker's yeast
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Baker's yeast was shown to catalyze the transformation of cysteine-furfural conjugate into 2-furfurylthiol. The biotransformation's yield and kinetics were influenced by the reaction parameters such as pH, incubation mode (aerobic and anaerobic), and substrate concentration. 2-Furfurylthiol was obtained in an optimal 37% yield when cysteine-furfural conjugate at a 20 mM concentration was anaerobically incubated with whole cell baker's yeast at pH 8.0 and 30 °C. Similarly to 2-furfurylthiol, 5-methyl-2-furfurylthiol (11%), benzylthiol (8%), 2-thiophenemethanethiol (22%), 3-methyl-2-thiophenemethanethiol (3%), and 2-pyrrolemethanethiol (6%) were obtained from the corresponding cysteine-aldehyde conjugates by incubation with baker's yeast. This work indicates the versatile bioconversion capacity of baker's yeast for the generation of thiols from cysteine-aldehyde conjugates. Thanks to its food-grade character, baker's yeast provides a biochemical tool to produce thiols, which can be used as flavorings in foods and beverages.
- Huynh-Ba, Tuong,Matthey-Doret, Walter,Fay, Laurent B.,Rhlid, Rachid Bel
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p. 3629 - 3635
(2007/10/03)
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- Chemoselective protection of thiols versus alcohols and phenols. The Tosvinyl group
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The conjugate addition of aliphatic and aromatic thiols to ethynyl p-tolyl sulphone (tosylacetylene) has been managed to afford Tosvinyl derivatives chemoselectively (in the presence of oxygen nucleophiles) and stereoselectively (isomers Z) in practically quantitative yields. The conditions of choice are: catalytic amounts of Et3N (only 0.5-1.0 mol%), a reaction temperature around 0°C and, for the less acidic thiols, CF3CH2OH or CH3CN/CF3CH2OH as the solvent. Thus, N-Boc-Cys-OMe has been quantitatively protected as its S-Tosvinyl derivative in the presence of N-Boc-Ser-OMe and N-Boc-Tyr-OMe. This novel protecting group is stable to several basic and acidic conditions; its removal is achieved at rt by treatment with an excess of pyrrolidine or at 0°C with alkanethiolate ions.
- Arjona, Odón,Medel, Rocío,Rojas, Jenny,Costa, Anna M.,Vilarrasa, Jaume
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p. 6369 - 6373
(2007/10/03)
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