- Neighboring-Group Participation in the Gas Phase. Loss of Benzaldehyde from dialkylsilyl-Substituted 1,3-Dithianes
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dialkylsilyl-substituted 1,3-dithianes show in CI-MS an abundant loss of benzaldehyde from the (1+) quasi-molecular ion.The fragmentation is explained with an intramolecular redox process, where a hydride is proposed to be transfer
- Faessler, Juerg,Huber, Priska,Bratovanov, Svetoslav,Bigler, Laurent,Bild, Norbert,Bienz, Stefan
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- Cyanuric chloride-catalyzed thioacetalization for organocatalytic synthesis of thioacetals
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The thioacetalization of aromatic aldehydes has been realized with broad diversity in the presence of various thiols and thiophenols using cyanuric chloride as an organocatalyst.
- Liu, Yaqin
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p. 679 - 682
(2016/05/09)
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- Ethyl lactate mediated thioacetalization of aldehydes at ambient temperature
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Dithioacetalization reactions of aldehydes with thiols/thiophenols have been successfully achieved at room temperature by employing the green, bio-based ethyl lactate as the reaction medium. By means of this sustainable approach, a class of dithioacetals has been acquired with high diversity and efficiency.
- Wan, Jie-Ping,Jing, Yanfeng,Liu, Yunyun
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p. 1302 - 1305
(2016/09/28)
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- INTRODUCTION OF ALKYL SUBSTITUENTS TO AROMATIC COMPOUNDS
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Novel selective synthesis route to introduce primary alkyl groups on aromatic compounds is disclosed. The synthesis route is based on electrophilic aromatic substitutions of thionium ion species that are generated in-situ from aldehydes and thiols, affording benzyl sulfide that can be reduced with triethylsilane.
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Page/Page column 67
(2016/09/15)
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- Reductive Alkylation of Arenes by a Thiol-Based Multicomponent Reaction
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A simple and highly chemo- and regioselective method for introducing primary alkyl substituents into aromatic compounds was developed. The method is based on an electrophilic aromatic substitution of an aldehyde, promoted by a thiol, to afford 1-(alkylthio)alkylarenes, which can either be reduced in situ with triethylsilane or reacted further. This multicomponent reaction enables the direct introduction of both aromatic and linear and branched aliphatic alkyl groups into arenes. The above one-pot protocol may be performed in air and in the presence of water and is compatible with various functional groups.
- Parnes, Regev,Pappo, Doron
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supporting information
p. 2924 - 2927
(2015/06/30)
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- Visible-light-promoted conversion of alkyl benzyl ether to alkyl ester or alcohol via O-α-sp3 C-H cleavage
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A mild and high-yielding visible-light-promoted conversion of alkyl benzyl ethers to the alkyl esters or alkyl alcohols was developed. Mechanistic studies provided evidence for a radical chain reaction involving the homolytic cleavage of O-α-sp3 C-H bonds in the substrate as one of the propagation steps. We propose that α-bromoethers are key intermediates in the transformation.
- Lu, Ping,Hou, Tianyuan,Gu, Xiangyong,Li, Pixu
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p. 1954 - 1957
(2015/04/27)
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- Synthesis in ionic liquids only: Access to α-oxo-γ-thio-esters via Mukaiyama coupling
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Ionic liquids are solvents general enough to conduct a multi-step process in organic synthesis. We show that both the preparation of starting materials (thioacetals and enoxysilane) as well as their coupling can be realized in such medium.
- Jebri, Khouloud,Mazières, Marie-Rose,Ballereau, Stéphanie,Ben Ayed, Ta?cir,Plaquevent, Jean-Christophe,Baltas, Michel,Guillen, Frédéric
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supporting information
p. 1353 - 1356
(2014/03/21)
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- Chemoselective and odorless transthioacetalization of acetals using α-oxo-ketene dithioacetals as thiol equivalents
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Using α-oxo-ketene dithioacetals 1a as odorless thiol equivlents, an efficient and odorless transthioacetalization of acetals 2 has been developed. In the presence of MeCOCl in MeOH, the cleavage of 1a commences to generate thiols at both room and reflux temperatures, and the generated thiols then react with acetals 2 to give correspecting thioacetals 3 in good yield. This transthioacetalization is characterized by mild reaction conditions, simple procedure, good yields, and perfect chemoselectivity. It is noteworthy that only a very faint odor of thiols can be perceived during both the reaction and workup.
- Yu, Hai-Feng
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p. 1280 - 1286
(2013/04/10)
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- Triflic acid catalyzed reductive coupling reactions of carbonyl compounds with O-, S-, and N-nucleophiles
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Highly efficient metal-free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid (1-5 mol %) as the catalyst are presented. The reactions can be performed at ambient temperature without exclusion of moisture or air. A range of symmetrical and unsymmetrical ethers were obtained by this method in high yields and short reaction times. For the first time, the influence of additional functionalization has been studied. Furthermore, the formation of thioethers from ketones (by addition of unmodified thiols) and of sulfonamides from either aldehydes or ketones has been achieved under catalytic conditions.
- Gellert, Beate A.,Kahlcke, Nils,Feurer, Markus,Roth, Stefanie
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supporting information; experimental part
p. 12203 - 12209
(2011/11/07)
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- Silica-supported phosphorus pentoxide: A reusable catalyst for S,S-acetalization of carbonyl groups under ambient conditions
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Phosphorus pentoxide supported on silica gel (P2O 5/SiO2) efficiently acts as a highly active and reusable catalyst for cyclic and non-cyclic S,S-acetalization of a variety of carbonyl compounds under mild, solvent-free an
- Shaterian, Hamid Reza,Azizi, Kobra,Fahimi, Nafiseh
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experimental part
p. 85 - 91
(2012/01/06)
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- Catalytic syntheses of γ-functionalized α-keto esters from thioacetals and N,O-acetals
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Ethyl 2-(trimethylsilyloxy)acrylic ester (1a) reacts with thioacetals providing the corresponding α-keto-γ-thio esters in good to satisfactory yields. Whereas aminals do not react, N,O-acetals lead to γ-amino-α-keto esters in good to excellent yields. All reactions proceed under mild reaction conditions, and no additional work up is required. Subsequent transformations of the obtained products to the corresponding α-oximes have been demonstrated.
- Krebs, Anke,Bolm, Carsten
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experimental part
p. 4055 - 4060
(2011/06/24)
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- Catalytic carbon-sulfur bond formation by amphoteric vanadyl triflate: exploring with thia-Michael addition, thioacetalization, and transthioacetalization reactions
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A series of thiols have been examined as protic nucleophiles for Michael-type additions to α,β-unsaturated carbonyls as well as double nucleophilic condensations with aldehydes, ketones, and acetals catalyzed by amphoteric, water-tolerant vanadyl triflate under mild and neutral conditions. The newly developed C-S bond formation protocols were carried out smoothly in good to high yields in a highly chemoselective manner.
- Chen, Chien-Tien,Lin, Yow-Dzer,Liu, Cheng-Yuan
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supporting information; experimental part
p. 10470 - 10476
(2010/02/28)
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- Silica-PCl5: A novel heterogenous catalyst for simple and efficient chemoselective protection of carbonyl compounds
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A simple, efficient and environmentally benign procedure has been developed for chemoselective protection of carbonyl compounds using the newly developed heterogeneous catalyst: Silica-PCl5. A variety of aldehydes and ketones were efficiently c
- Pandey, Lokesh Kumar,Pathak, Uma,Tank, Rekha,Mazumder, Avik
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experimental part
p. 167 - 171
(2010/07/05)
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- Hafnium trifluoromethanesulfonate (hafnium triflate) as a highly efficient catalyst for chemoselective thioacetalization and transthioacetalization of carbonyl compounds
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(Chemical Equation Presented) A range of carbonyl compounds including aliphatic and aromatic aldehydes and ketones were converted to the corresponding thioacetals in high yields in the presence of a catalytic amount of hafnium trifluoromethanesulfonate (0.1 mol %, room temperature). The mild conditions tolerated various sensitive functional and protecting groups and were racemization-free when applied to α-aminoaldehydes. Transacetalization and chemoselective thioacetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones were also documented.
- Wu, Yan-Chao,Zhu, Jieping
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supporting information; experimental part
p. 9522 - 9524
(2009/04/06)
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- GaCI3- and TiCl4-catalyzed insertion of isocyanides into a C-S bond of dithioacetals
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(Chemical Equation Presented) The insertion reaction of isocyanide into a C-S bond of dithioacetals is catalyzed by GaCl3 or TiCl4 to afford thioimidates containing an a-alkylthio group. Balanced thiophilicity of these Lewis acids is
- Tobisu, Mamoru,Ito, Sana,Kitajima, Aki,Chatani, Naoto
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supporting information; body text
p. 5223 - 5225
(2009/06/18)
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- A mild and chemoselective dithioacetalization of aldehydes in the presence of anhydrous copper (II) sulfate
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Various aldehydes have been protected with different thiols as dithioacetals with excellent yields using anhydrous copper sulfate as a mild and chemoselective catalyst. The reaction is carried out in a solvent and/or under solvent-free conditions. The transthioacetalization of oxyacetals into dithioacetals was also achieved in an excellent yield. Copyright Taylor & Francis Group, LLC.
- Moghaddam, Firouz Matloubi,Bardajee, Ghasem Rezanejade,Oskui, Afsane Arefi
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p. 1445 - 1450
(2007/10/03)
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- Simple, mild and efficient thioacetalization and transthioacetalization of carbonyl compounds and deprotection of thioacetals: Unique role of thiols in the selectivity of thioacetalization
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Silica supported sodium hydrogen sulfate (NaHSO4·SiO 2) has been employed for efficient thioacetalization and transthioacetalization of carbonyl compounds in CH2Cl2 at room temperature. Selectivity of thioacetalization was dependent on the thiols used for the conversion. The same catalyst was also found to be effective for deprotection of thioacetals in CH2Cl2-H2O at room temperature.
- Das, Biswanath,Ramu, Ravirala,Reddy, Majjigapu Ravinder,Mahender, Gurram
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p. 250 - 254
(2007/10/03)
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- Ruthenium(III) chloride-catalyzed thioacetalization of carbonyl compounds: Scope, selectivity, and limitations
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A variety of carbonyl compounds can be easily and rapidly converted to the corresponding cyclic and acylic dithioacetals in the presence of a catalytic amount of ruthenium chloride in acetonitrile at room temperature. Some of the major advantages of this
- De, Surya Kanta
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p. 673 - 676
(2007/10/03)
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- Investigations towards the chemoselective thioacetaliztion of carbonyl compounds by using ionic liquid [bmim]Br as a recyclable catalytic medium
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The ionic liquid based on the 1-n-butyl-3-methylimidazolium cation has been prepared and used as an efficient catalytic medum for the chemoselective thioacetalization of carbonyl compounds. Furthermore, recycling and reuse of this ionic liquid medium has
- Kamal, Ahmed,Chouhan, Gagan
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p. 579 - 582
(2007/10/03)
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- Pr(OTf)3 as an efficient and recyclable catalyst for chemoselective thioacetalization of aldehydes
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Praseodymium triflate has been found to be an efficient and recyclable catalyst for chemoselective protection of aldehydes.
- De, Surya Kanta
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p. 2837 - 2840
(2007/10/03)
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- Cobalt(II)chloride catalyzed chemoselective thioacetalization of aldehydes
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A mild and chemoselective dithioacetalization procedure for the protection of various aldehydes in the presence of catalytic amount of cobalt(II)chloride is described.
- De, Surya Kanta
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p. 1035 - 1036
(2007/10/03)
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- Chemoselective thioacetalization and transthioacetalization of carbonyl compounds catalyzed by immobilized scandium(III) triflate in ionic liquids
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Immobilized scandium triflate [Sc(OTf)3] in ionic liquids has been found to be an extremely efficient and recyclable catalyst for the thioacetalization and transthioacetalization of both aromatic and aliphatic aldehydes. Significant rate acceleration and chemoselectivity was achieved by employing this catalytic system.
- Kamal, Ahmed,Chouhan, Gagan
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p. 3337 - 3340
(2007/10/03)
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- 2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO), N-bromosuccinimide (NBS) and bromine as efficient catalysts for dithioacetalization and oxathioacetalization of carbonyl compounds and transdithioacetalization reactions
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The use of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO), N-bromosuccinimide (NBS), and bromine as efficient catalysts for conversion of carbonyl compounds to their cyclic and acyclic dithioacetals and 1,3-oxathiolanes under mild reaction conditions are described. These catalysts are also used for efficient transdithioacetalization of acetals, diacetals, ketals, acylals, enamines, hydrazones, and oximes with high yields in the presence of thiols.
- Iranpoor, Nasser,Firouzabadi, Habib,Shaterian, Hamid Reza,Zolfigol
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p. 1047 - 1071
(2007/10/03)
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- Highly efficient transthioacetalization of O,O-acetals catalyzed by indium(III) chloride
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A simple, efficient and general procedure has been developed for the transthioacetalization of O,O-acetals catalyzed by indium(III) chloride in 1,2-dichloroethane.
- Ranu, Brindaban C.,Das, Arijit,Samanta, Sampak
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p. 727 - 730
(2007/10/03)
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- Oxathioacetalization, thioacetalization and transthioacetalization of carbonyl compounds by N-bromosuccinimide: Selectivity and scope
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Efficient oxathioacetalization, thioacetalization and transthioacetalization of carbonyl compounds have been achieved in high yields employing N-bromosuccinimide as a catalyst.
- Kamal, Ahmed,Chouhan, Gagan,Ahmed, Kaleem
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p. 6947 - 6951
(2007/10/03)
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- Catalysis by ionic liquids: Solvent-free efficient transthioacetalisation of acetals by molten tetrabutylammonium bromide
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Transthioacetalisation of acetals to dithioacetals by a solvent-free reaction with a thiol or dithiol catalyzed by molten tetrabutylammonium bromide was presented. Acetals were prepared by standard methods and were purified by distillation or chromatography. Tetrabutylammonium bromide in molten state was demonstrated to be an efficient and recyclable catalyst. The methodology offered improvements over other procedures in relation to yield of products, selectivity for acetal of aldehyde over that of ketone, and mildness of reaction conditions.
- Ranu, Brindaban C.,Das, Arijit,Samanta, Sampak
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p. 1520 - 1522
(2007/10/03)
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- Lithium bromide, a novel and highly effective catalyst for monothioacetalization of acetals under mild reaction conditions
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Lithium bromide is efficient as a catalyst for the monothioacetalization of acetals under mild reaction conditions to provide products in excellent yields with high chemoselectivity.
- Ono,Negoro,Sato
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p. 1581 - 1583
(2007/10/03)
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- TaCl5-Silicagel and TaCl5 as new Lewis acid systems for selective tetrahydropyranylation of alcohols and thioacetalisation, trimerisation and aldolisation of aldehydes
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TaCl5 adsorbed on silicagel has been utilized for the first time as Lewis acid catalyst for protection of aldehydes and alcohols as thiocetals and THP ethers respectively. Similarly TaCl5 has been exploited as an useful Lewis acid for chemoselective trimerisation and/or aldolisation of aldehydes.
- Chandrasekhar,Takhi, Mohamed,Reddy, Y. Ravindra,Mohapatra, Suchismita,Rao, C. Rama,Reddy, K. Venkatram
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p. 14997 - 15004
(2007/10/03)
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- Lewis Acid Activated Reactions of Mixed (O,Se) Acetals with Allyltrimethylsilane and Allyltributylstannane
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On the basis of preferential complexation of oxygen or selenium atoms by different Lewis acids, it was expected that, depending on the Lewis acid employed, the title reactions would lead to selective formation of homoallyl ethers or homoallyl selenides.This has not been confirmed by experiment: in almost all the reactions tried homoallyl ethers largely predominated, or were the exclusive allylation products, even when strongly oxygenophilic Lewis acids such as TiCl4 were used.In the cases of the latter type of Lewis acids, the results observed with (O,Se) and a couple of (O, S) mixed acetals are interpreted in terms of two major factors operating in opposite directions. 1H NMR data of a mixture of TiCl4 and (O,Se) acetal indicate that preferential (but not exclusive) complexation of the oxygen moiety takes place indeed.However, because of the much stronger C-O bond as compared to the C-Se bond, this latter (also activated by the Lewis acid to some extent) undergoes cleavage by allyl metals to give homoallyl ethers as predominating products.In contrast with BF3*OEt2, boron trichloride and boron tribromide were found to react with (O, Se) acetals to give the corresponding α-halo selenides, which in turn were cleanly transformed into homoallyl selenides on reaction with allyltrimethylsilane in the presence of tin tetrachloride.
- Hermans, Bernard,Hevesi, Laszlo
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p. 6141 - 6147
(2007/10/03)
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- Proton Transfer from Carbon. A Study of the Acid-Base-catalysed Relaxation and the Bromination of Aryl-substituted Methanedisulfones
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Seven aryl-substituted derivatives of bis(ethylsulfonyl)methane have been synthesized and studied thermodynamically and kinetically in aqueous solution with respect to proton abstraction from the central carbon atom.The acidities of the six carbon acids are in the range pKA 10-12.The relaxation times of the reactions were studied by a spectrophotometric temperature-jump technique (hydroxide ion and phenolates as proton acceptors) and are in the microsecond range.The rates of bromination of the various carbanions have also been studied (potentiometrically) and the reactions are shown to be almost diffusion-controlled, with no marked trend with aromatic substituent.A small chemical activation may be due to a steric effect by the two sulfonyl groups.The rates of deprotonation, however, show considerable chemical activation, i.e., intrinsic rates are 3-4 orders of magnitude lower than for normal acids, indicating partial delocalization of the negative charge on the carbanion.This effect is somewhat larger than for cyano-activated carbon acids but considerably smaller than for carbon acids activated by carbonyl or nitro groups.It is concluded that sulfonyl groups interact with carbanions primarily by polar effects, but also, to some extent, mesomerically.The degree of mesomerism is, however, uncertain because part of the intrinsic barrier may derive from steric effects, as is also observed for bromination.
- Aiken, Fiona,Cox, Brian G.,Soerensen, Poul E.
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p. 783 - 790
(2007/10/02)
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- Tellurium tetrachloride as a mild and efficient catalyst for dithioacetalization
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A variety of aldehydes and aliphatic ketones were converted into the corresponding dithioacetals at room temperature in good yields by using small amounts of tellurium tetrachloride as a mild Lewis acid catalyst.
- Tani, Hiroyuki,Masumoto, Kazunori,Inamasu, Tokuo,Suzuki, Hitomi
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p. 2039 - 2042
(2007/10/02)
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- Synthese von 4-Benzylthio- und 4-(Arylthio)-1,3-oxazol-5(2H)-onen
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Following a known procedure, 4-(benzylthio)-1,3-oxazol-5(2H)-one (4a) was synthesized starting from sodium cyanodithioformate (1) and cyclohexanone (Scheme 1).The structure of the intermediate 4-(benzylthio)-1,3-thiazol-5(2H)-one (3a) was established by X-ray crystallography.An alternative route was developed for the synthesis of 4-(arylthio)-1,3-oxazol-5(2H)-ones which are not accessible by the former reaction.Treatment of ethy cyanoformate (5) with a thiophenol in the presence of catalytic amounts of Et2NH and TiCl4, followed by addition of a ketone anf BF3*Et2O in a one-pot-reaction, gave 4f-i in low-toair yields (Scheme 3).Both synthetic pathways - complementary as for benzyl-S aryl-S derivatives seem to be limited with respect to variation of substituents of the ketone.
- Wipf, Peter,Prewo, Roland,Bieri, Jost H.,Heimgartner, Heinz,Nastopoulos, Vassilios,Germain, Gabriel
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p. 1380 - 1388
(2007/10/02)
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- TITANIUM TETRACHLORIDE, AN EFFICIENT AND CONVENIENT REAGENT FOR THIOACETALIZATION
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Aldehydes and ketones, when exposed to alkyl thiols or suitable alkane dithiols in presence of titanium tetrachloride, furnish near quantitative yields of the corresponding thioacetals.
- Kumar, Vijay,Dev, Sukh
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p. 1289 - 1292
(2007/10/02)
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- CARBON-CARBON DOUBLE BOND CLEAVAGE WITH A HARD LEWIS ACID AND ETHANETHIOL
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Double bonds activated by the electron withdrawing group(s) are cleaved with the reagent system consisting of a hard Lewis acid and ethanethiol to give dithioacetals.
- Fuji, Kaoru,Kawabata, Takeo,Node, Manabu,Fujita, Eiich
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p. 875 - 878
(2007/10/02)
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- A simple and efficient method of thioacetal - and ketalization
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AlCl3 has been found to be an efficient reagent for promoting thioacetal- and ketalization of carbonyl compounds.
- Ong, Beng S.
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p. 4225 - 4228
(2007/10/02)
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- Electroreduction of Organic Compounds, 2. - Preperation of Dithioacetals by Electroreductive Alkylation of Alkyl Dithiocarboxylates
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Alkyl Dithiobenzoates 1 and O-methyl thiobenzoate (7) yield the benzaldehyde dithioacetals 2 or monothioacetals 8, respectively, by electroreduction in the presence of alkyl halides.The S-acylal 3b is formed from ethyl dithiobenzoate 1b in the presence of acetic anhydride. - The dithioacetals 5 and the ketene dithioacetals 6 are obtained by co-electroreduction of methyl dithiopropionate (4) with alkyl halides. - Conclusions about the reaction mechanism are drawn from voltammetric measurements.
- Kistenbruegger, Lothar,Voss, Juergen
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p. 472 - 480
(2007/10/02)
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