- Thiolation of cycloalkenes C5, C6 by redox-activation of hydrogen sulfide
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Direct and indirect redox-activation of H2S in the presence of cyclopentene or cyclohexene in MeCN at 25?°C affords the corresponding cycloalkanethiols.
- Shinkar, Elena V.,Kudryavtsev, Daniil A.,Pashchenko, Konstantin P.,Berberova, Nadezhda T.,Okhlobystina, Alexandra V.
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Read Online
- The benzyl can be selectively removed by visible light or near visible light. Method for protecting allyl and propargyl group
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The invention provides a method for selectively removing benzyl, allyl and propargyl protecting groups by visible light or near visible light, namely a substrate containing benzyl, allyl or propargyl protecting groups. The method has the advantages of simple operation, safe and clean visible light or near visible light as excitation conditions, cheap and easily available reagents, high reaction yield, high reaction chemistry and regional selectivity, and is suitable for selective removal of benzyl, allyl and propargyl protecting groups in various substrates.
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Paragraph 0031
(2021/10/16)
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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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- Chromium(III) and indium(III) 3,6-di-tert-butyl-o-semiquinolate complexes as redox mediators of hydrogen sulfide oxidation in reactions with cycloalkanes
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The electrochemical oxidation of the chromium(III) and indium(III) complexes with 3,6-di-tert-butyl-o-semiquinolate leading to the formation of active monocationic species is studied by cyclic voltammetry. The reactions of the latter with hydrogen sulfide generate the radical cation of H2S, whose fragmentation affords the proton and thiyl radical. These complexes are proposed for the first time as redox mediators for the one-pot thiolation of inert cycloalkanes C6–C8, which decreases the activation energy of hydrogen sulfide compared to that for direct electrochemical oxidation. The major products of cycloalkane functionalization involving H2S are thiols and organic di- and trisulfides. The yield of the synthesized compounds depends on the type of the mediator: the chromium(III) complex exhibits the highest efficiency in the electrocatalytic transformations.
- Berberova,Shinkar,Smolyaninov,Shvetsova,Sediki
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p. 578 - 582
(2017/09/23)
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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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p. 4050 - 4055
(2017/04/27)
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- Redox mediators of hydrogen sulfide oxidation in reactions with cycloalkanes
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An indirect electrochemical method for thiolation of cycloalkanes C5-C7 has been suggested. The method is based on a new approach to activation of hydrogen sulfide by redox mediators.
- Berberova,Shinkar',Smolyaninov,Pashchenko
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p. 295 - 298
(2016/01/12)
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- Flavouring and odorant thiols from renewable natural resources by InIII-catalysed hydrothioacetylation and lipase-catalysed solvolysis
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A chemoenzymatic access to thiol compounds, including ethyl 3-thiobutanoate, 3-thio-p-menthene and 8-thio-p-menthan-2-one, three compounds of interest in flavour and fragrance chemistry presenting various fruity notes, is proposed. It involves an indium(III)-catalysed hydrothioacetylation of renewable precursors followed by an enzymatic solvolysis of the obtained thioesters by lipases in aqueous or organic solvents.
- Dia, Reine-Marie,Belaqziz, Rim,Romane, Abderrahmane,Antoniotti, Sylvain,Du?ach, Elisabet
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scheme or table
p. 2164 - 2167
(2010/06/13)
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- Process and catalyst for synthesis of mercaptans and sulfides from alcohols
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A process and catalyst blend for selectively producing mercaptans and sulfides from alcohols. The alcohol is reacted with hydrogen sulfide, in the presence of a catalyst blend containing a hydrotreating catalyst and a dehydration catalyst to convert the alcohol to mercaptan or sulfide in one-pass. The alcohols can include primary and secondary alcohols. The mercaptan or sulfide having less than about 30% unreacted alcohol contained therein.
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Page/Page column 9-10
(2008/06/13)
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- Deacylation of esters, thioesters and amides by a naphthalene-catalysed lithiation
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The reaction of different esters, thioesters and amides derived from pivalic, benzoic and 4-tert-butylbenzoic acids with an excess of lithium and a catalytic amount of naphthalene (8 mol%) led, after methanolysis, to the corresponding alcohols, thiols and amines, respectively, through a reductive non-hydrolytic procedure. This methodology represents a reasonable alternative to other non-reductive protocols. Georg Thieme Verlag Stuttgart.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
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p. 309 - 314
(2007/10/03)
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- Desilylation procedure via a naphthalene-catalysed lithiation reaction
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The reaction of silyl protected alcohols, amines and thiols with lithium powder and a catalytic amount of naphthalene, in THF, at 0°C led, after hydrolysis, to the recovery of the free alcohols, amines and thiols in very good yields. At least a phenyl group was required in the silyl protecting group for the success of the reaction. Some polyfunctionalised starting materials have successfully been deprotected. The stereochemical outcome of the deprotection of a silylated chiral secondary alcohol has also been studied and no racemization was observed. The process has shown to be a good alternative to the acid-catalysed desilylation procedures, the latter being not useful for the deprotection of some silylated tertiary alcohols.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
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p. 6908 - 6915
(2007/10/03)
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- Deallyloxy- and debenzyloxycarbonylation of protected alcohols, amines and thiols via a naphthalene-catalysed lithiation reaction
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The naphthalene-catalysed lithiation of Alloc- and Cbz-protected alcohols, amines and thiols in THF at 0°C led, after quenching with methanol, to the recovery of the free alcohols, amines and thiols in short reaction times and with very good yields. The selectivity for the removal of the Alloc- or the Cbz- group in a polyfunctionalised substrate has been studied. The selective reductive cleavage of a benzylic carbon-oxygen bond was achieved in the presence of an allylic carbon-oxygen or carbon-nitrogen bond. This method represents a great improvement in comparison with the previously reported deprotection procedures by dissolving metals, since it avoids the use of the toxic liquid ammonia and, therefore, the need to perform the reaction at low temperatures.
- Behloul, Cherif,Guijarro, David,Yus, Miguel
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p. 9319 - 9324
(2007/10/03)
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- Catalytic polymer-supported potassium thiophenolate in methanol as a method for the removal of ester, amide, and thioacetate protecting groups
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Polymer-supported potassium thiophenolate to remove ester, activated amide, and thioacetate protecting groups catalytically in the presence of methanol is reported.
- MacCoss, Rachel N.,Henry, Dara J.,Brain, Christopher T.,Ley, Steven V.
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p. 675 - 678
(2007/10/03)
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- Modified Borohydride Agents, 1-Benzyl-4-aza-1-azoniabicyclooctane Tetrahydroborate (BAAOTB) versus Tetrabutylammonium Tetrahydroborate (TBATB). Efficient, Selective, and Versatile Reducing Agents
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1-Benzyl-4-aza-1-azoniabicyclooctane tetrahydroborate (BAAOTB) and tetrabutylammonium tetrahydroborate (TBATB) are used for the selective reductions of aldehydes, ketones, α,β-unsaturated carbonyl compounds, acid chlorides, azides, epoxides, and disulfides in t-BuOH and hexane/chloroform.ABBOAB with its rigid and bulky structure reacts more selectively than its analogue TBATB.
- Firouzabadi, Habib,Afsharifar, Gholam Reza
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p. 2595 - 2602
(2007/10/03)
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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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p. 2655 - 2663
(2007/10/02)
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- The reaction of carbon radicals with sulfur. A convenient synthesis of thiols from carboxylic acids
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A new synthesis of thiols in high yield utilizing carbon radicals and elemental sulfur is demonstrated. The procedure is applicable to 1°, 2° and 3° carboxylic acids.
- Barton, Derek H. R.,Castagnino, Enzo,Jaszberenyi, Joseph Cs.
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p. 6057 - 6060
(2007/10/02)
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- NONCONVENTIONAL FRIEDEL-CRAFTS CHEMISTRY IV. ON THE REACTION OF 1,3-OXATHIOLAN-5-ONE-2-SPIRO-1'-CYCLOALKANES WITH FERROCENE IN THE PRESENCE OF AlCl3 CATALYLST
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The reaction of ferrocene with 1-oxa-4-thiaspirononan-2-one (1) and /or 1-oxa-4-thiaspiro-decan-2-one (2) in the presence of aluminum chloride catalyst afforded the spiroferrocene derivatives 4, 6, 5 and 7, respectively.The mechanism of these reactions is discussed.Key words: Friedel-Crafts reactions; ferrocene chemistry.
- Ei-Zohry, Maher F.
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p. 305 - 310
(2007/10/02)
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- NONCONVENTIONAL FRIEDEL-CRAFTS CHEMISTRY III. ON THE REGIOSPECIFIC SYNTHESIS OF SPIRO-4'-ONE DERIVATIVES
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The rection of 1-oxa-4-thiaspirononan-2-one (4) and/or 1-oxa-4-thiaspirodecan-2-one (5) with arenes (6) under the catalytic action of aluminum chloride afforded in all cases spiro-4'-ones (7a - g and 8a - g), -acetic acid, (9a - g and 10a - g), cycloalkylthioacetic acids, (11 and 20) aryl cycloalkyl sulfides, (14 and 23) diarylsulfides (15), diaryl disulfides and dicycloalkyl disulfides (13 and 22).The mechanisms of these reactions are discussed.Key words: Spiroisothiochroman-4-ones; Friedel-Crafts reactions.
- El-Zohry, Maher F.
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p. 311 - 320
(2007/10/02)
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- Organic Syntheses with Transition Metal Complexes, 48. - Methyl Thiocarbene and Alkenyl Thiocarbene Chromium Complexes: Synthesis and Reactions
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Thiocarbene chromium complexes (CO)5Cr=C(SR1)R (4: R = Me, Ph; R1 = c-C6H11, CH2CH=CH2, C2H5, C6H5) were readily obtained in up to 97 percent isolated yields from the corresponding ethoxycarbene chromium complexes 5a,b and thiols 6 in methanol in the presence of Na2CO3 as a catalyst.Reaction conditions, which lead to unfavorable side products, like thioacetals 8 and/or thioenol ether 10, are discussed.Methyl thiocarbene complexes 4b-d undergo a facile aldol condensation with the aromatic aldehydes 14 or 16 to give alkenyl thiocarbene complexes 15b-d and 17, respectively.The Cr=C bonds of 15 prove to be reactive towards the insertion of isocyanides or oxygen.Thus, on addition of two equivalents of the isocyanide 18 to 15d, 1-aza-1,2,4-pentatriene 20 is obtained.The oxidative decomposition of 15d on silica gel leads to the formation of thioester 25 and thioindene 26.Characteristic differences in the reactivity of thiocarbene complexes and ethoxycarbene complexes are discussed.
- Aumann, Rudolf,Schroeder, Jochen
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p. 2053 - 2058
(2007/10/02)
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- NEW SYNTHESIS OF 1,2,5-SELENADIAZOLES
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A new synthesis of 1,2,5-selenadiazoles which starts from unsubstituted or monosubstituted 1,2,5-thiadiazoles and Grignard reagents is described and the mechanism of the reaction discussed.
- Bertini, Vincenzo,Munno, Angela De,Picci, Nevio,Lucchesini, Francesco,Pocci, Marco
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p. 2153 - 2158
(2007/10/02)
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- Studies on the Occurrence of Hydrogen Transfer, 76. The Anomal Course of the Electroreduction of Coumarine with Supporting Electrolyts Containing Li(+). Experiments to Influence the Reaction by Mediators
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In contradiction to the experience the hydrodimer is formed as the main product in the electroreduction of coumarine using lithium compounds as a supporting electrolyt.It is assumed that the lithium ions are coordinated internally with the radicalanion A resp.B derived from coumarine.In this way the hydrodimerization is favoured.From 18 different compounds added as possible mediators to the catholyt only pyridine influences moderately the ratio: hydrodimerization product/dihydroproduct. - Keywords: Hydrogen Transfer, Coumarine, Electroreduction
- Horner, Leopold,Franz, Christoph
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p. 822 - 825
(2007/10/02)
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- FORMATION OF SULPHUR COMPOUNDS DURING THE HYDRODENITROGENATION OF ANILINE, CYCLOHEXYLAMINE, BENZYLAMINE, AND 2-PHENYLETHYLAMINE ON A NICKEL-TUNGSTEN CATALYST IN THE PRESENCE OF HYDROGEN SULPHIDE
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Hydrodenitrogenations of aniline, cyclohexylamine, benzylamine, and 2-phenylethylamine were performed on a sulphided nickel-tungsten catalyst at 300 deg C in an autoclave filled with hydrogen in the absence and in the presence of hydrogen sulphide.Due to the presence of hydrogen sulphide the degree of conversion increased from 0.9 to 3,6percent for aniline and from 72 to 99percent for benzylamine, and the fraction of neutral substances increased from 2.4 to 7percent for cyclohexylamine and from 5.0 to 8.9percent for 2-phenylethylamine.The neutral fractions contained cyclohexanethiol, thiobenzamide, 2-phenylethanethiol, and other sulphur compounds giving evidence that the increased degree of conversion of the amines was due to the hydrogen sulphide taking direct part in the chemical reaction.
- Cerny, Mirko,Trka, Antonin
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p. 2387 - 2392
(2007/10/02)
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- Thiono Compounds. 1. Interactions of Monoatomic Sulfur, Including Insertion into S-H Bonds
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Possible traps for monoatomic sulfur were assessed by determining the reduction in yields of cyclohexanethiol (6) when carbonyl sulfide was photolyzed in cyclohexane containing the potential trap; the identity of 6 was confirmed by GC/MS and other means.Reduction of the yield of 6 by benzene, triethylamine, acetic acid, acetonitrile, and ethanol indicates undesirability of lone pair and ? systems in the assessment procedure.In order of promise as traps, compounds tested were n-Bu3SnH > (n-C5H11S)2 ca.= RSH > (EtO)3SiH > Et3SiH ca.= cyclohexane.Insertion of sulfur was demonstrated with two thiols, chosen as members of one of the most promising classes, by identity with authentic samples of derivatives of the hydrodisulfides generated; this result points to the chemical feasibility of postulated insertions of monoatomic sulfur in biological reactions and also suggests promise of the other potential traps for further study.
- Field, Lamar,Ravan, J. Valerie,Dunkel, John D.,Waites, John A.,White, David W.,et al.
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p. 4651 - 4654
(2007/10/02)
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- Metalation of 1,3-Dithiolanes. Mercaptan Synthesis and Carbonyl Transposition
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The reaction of 1,3-dithiolanes with n-butyllithium results in fragmentation to the corresponding thiocarbonyl compound followed by furhter reaction with n-butyllithium.All four types of thiocarbonyl reactions are observed: reduction, S-addition, C-addition, double addition.Synthetic applications of this reaction for the synthesis of secondary mercaptans and 1,2-carbonyl transposition (23 -> 24a-c) are described.
- Wilson, Stephen R.,Georgiadis, Gregory M.,Khatri, Hiralal N.,Bartmess, John E.
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p. 3577 - 3583
(2007/10/02)
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- Desulfuration Using Plasma Techniques, III. - Reaction of Thioethers
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Plasma desulfurations were tested with nine thioethers.While aliphatic, as well as aromatic thioethers and thiophene react easily, benzothiophenes are hard to desulfurize.Predominant reaction products are low molecular alkenes and alkanes (Table 1).Addition of oxygen greatly improves the results (Table 2).
- Suhr, Harald,Henne, Peter,Iacocca, Diodoro,Ropero, Marcos J.
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p. 441 - 446
(2007/10/02)
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