- Thiourea-Mediated Halogenation of Alcohols
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The halogenation of alcohols under mild conditions expedited by the presence of substoichiometric amounts of thiourea additives is presented. The amount of thiourea added dictates the pathway of the reaction, which may diverge from the desired halogenation reaction toward oxidation of the alcohol, in the absence of thiourea, or toward starting material recovery when excess thiourea is used. Both bromination and chlorination were highly efficient for primary, secondary, tertiary, and benzyl alcohols and tolerate a broad range of functional groups. Detailed electron paramagnetic resonance (EPR) studies, isotopic labeling, and other control experiments suggest a radical-based mechanism. The fact that the reaction is carried out at ambient conditions, uses ubiquitous and inexpensive reagents, boasts a wide scope, and can be made highly atom economic, makes this new methodology a very appealing option for this archetypical organic reaction.
- Mohite, Amar R.,Phatake, Ravindra S.,Dubey, Pooja,Agbaria, Mohamed,Shames, Alexander I.,Lemcoff, N. Gabriel,Reany, Ofer
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supporting information
p. 12901 - 12911
(2020/11/26)
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- Silver/NBS-Catalyzed Synthesis of α-Alkylated Aryl Ketones from Internal Alkynes and Benzyl Alcohols via Ether Intermediates
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The silver hexafluoroantimonate/N-bromosuccinimide (NBS)-catalyzed synthesis of α-alkylated aryl ketones with a tertiary carbon center from internal alkynes and benzyl alcohols is reported. This reaction proceeds via the etherification of benzyl alcohols with an in situ generated benzyl bromide, formed by the reaction of benzyl alcohol with a catalytic amount of NBS and AgSbF6. Ag-catalyzed C-O cleavage of the ether leads to a tolyl radical, which undergoes addition to the alkyne, ultimately leading to the α-alkylated aryl ketone products.
- Chun, Supill,Chung, Young Keun
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supporting information
p. 5583 - 5586
(2018/09/21)
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- Effect of Alcohol Structure on the Kinetics of Etherification and Dehydration over Tungstated Zirconia
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Linear and branched ether molecules have attracted recent interest as diesel additives and lubricants that can be produced from biomass-derived alcohols. In this study, tungstated zirconia was identified as a selective and green solid acid catalyst for the direct etherification of primary alcohols in the liquid phase, achieving ether selectivities of >94 % for C6–C12 linear alcohol coupling at 393 K. The length of linear primary alcohols (C6–C12) was shown to have a negligible effect on apparent activation energies for etherification and dehydration, demonstrating the possibility to produce both symmetrical and asymmetrical linear ethers. Reactions over a series of C6 alcohols with varying methyl branch positions indicated that substituted alcohols (2°, 3°) and alcohols with branches on the β-carbon readily undergo dehydration, but alcohols with branches at least three carbons away from the -OH group are highly selective to ether. A novel model compound, 4-hexyl-1dodecanol, was synthesized and tested to further demonstrate this structure–activity relationship. Trends in the effects of alcohol structure on selectivity were consistent with previously proposed mechanisms for etherification and dehydration, and help to define possible pathways to selectively form ethers from biomass-derived alcohols.
- Rorrer, Julie,Pindi, Suresh,Toste, F. Dean,Bell, Alexis T.
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p. 3104 - 3111
(2018/09/06)
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- Synthesis of Benzyl Alkyl Ethers by Intermolecular Dehydration of Benzyl Alcohol with Aliphatic Alcohols under the Effect of Copper Containing Catalysts
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Synthesis of benzyl alkyl ethers was performed in high yields by intermolecular dehydration of benzyl and primary, secondary, tertiary alcohols under the effect of copper containing catalysts. The formation of benzyl alkyl ethers occurs with participation of benzyl cation.
- Bayguzina,Gimaletdinova,Khusnutdinov
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p. 1148 - 1155
(2018/10/24)
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- Organohalide-catalyzed dehydrative O-alkylation between alcohols: A facile etherification method for aliphatic ether synthesis
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Organohalides are found to be effective catalysts for dehydrative O-alkylation reactions between alcohols, providing selective, practical, green, and easily scalable homo- and cross-etherification methods for the preparation of useful symmetrical and unsymmetrical aliphatic ethers from the readily available alcohols. Mechanistic studies revealed that organohalides are regenerated as reactive intermediates and recycled to catalyze the reactions.
- Xu, Qing,Xie, Huamei,Chen, Pingliang,Yu, Lei,Chen, Jianhui,Hu, Xingen
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supporting information
p. 2774 - 2779
(2015/05/27)
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- Intermolecular dehydration of alcohols by the action of copper compounds activated with carbon tetrabromide. synthesis of ethers
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Copper compounds of the general formula CuXn (X = Cl, Br, I, acac, OAc, C7H4O3, C7H 5O2; n = 1, 2) activated by carbon tetrabromide catalyzed intermolecular dehydration of primary and secondary alcohols with formation of the corresponding ethers.
- Khusnutdinov, R. I.,Bayguzina, A. R.,Gimaletdinova, L. I.,Dzhemilev, U. M.
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p. 1191 - 1196,6
(2020/10/15)
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- Ionic liquids - Advanced reaction media for organic synthesis
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The advantages in the application of ionic liquids as reaction media in organic synthesis, i.e., in the preparation of chromane derivatives, substituted pyrazines, 4-aminofuran-2(5H)-ones, or in bromination of Levulinic acid or dehydration of alcohols, saccharides, and polysaccharides, have been demonstrated on several examples. Ionic liquids with Bronsted acidity have been shown to possess catalytic activity and provide access to convenient technologies for the preparation of various useful compounds. Copyright Merck KGaA.
- Ignat'ev, Nikolai V.,Schulte, Michael,Koppe, Karsten,Barthen, Peter,Zlotin, Sergei G.,Makhova, Nina N.,Sheremetev, Aleksei B.,Valente, Anabela A.
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scheme or table
p. 1205 - 1216
(2011/09/16)
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- Rhodium-catalyzed, efficient deutero- and tritiosilylation of carbonyl compounds from hydrosilanes and deuterium or tritium
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A cationic rhodium compound which is an active catalyst for both the hydrogen isotope exchange in hydrosilanes and the hydrosilylation of carbonyl compounds permits, in a one-flask, two-step procedure, efficient deutero- and tritiosilylations using SiEt3H under D2 (0.5 bar) or T2, at low catalyst loadings (0.1-0.5 mol %).
- Rubio, Miguel,Campos, Jesuus,Carmona, Ernesto
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supporting information; experimental part
p. 5236 - 5239
(2011/12/15)
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- DEHYDRATION OF ALCOHOLS TO GIVE ALKENES OR ETHERS
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The present invention relates to a process for the dehydration of alcohols, polyalcohols or alcoholates having at least one CH group in the α-position to the alcoholate or alcohol function to give alcenes or ethers, where the dehydration is carried out in ionic liquids of the general formula K+A?.
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Page/Page column 9
(2009/04/24)
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- High-efficiency conversion of trimethylsilyl ethers to their corresponding ethers using carbon-based solid acid as a new catalyst in heterogeneous mixtures
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Carbon-based solid acid was used as a new catalyst for conversion of trimethylsilyl ethers to their corresponding ethers in heterogeneous mixtures. The experiments were done moderately at room temperature, and high yields in suitable times were obtained under these conditions. Copyright Taylor & Francis Group, LLC.
- Shokrollahi, Arash,Zali, Abbas,Pouretedal, Hamid Reza
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p. 371 - 375
(2008/04/01)
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- Catalysts for hydrogenation and hydrosilylation, methods of making and using the same
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A compound is provided including an organometallic complex represented by the formula I: [CpM(CO)2(NHC)Lk]+A???I wherein M is an atom of molybdenum or tangsten, Cp is substituted or unsubstituted cyclopentadienyl radical represented by the formula [C5Q1Q2Q3Q4Q5], wherein Q1to Q5are independently selected from the group consisting of H radical, C1-20hydrocarbyl radical, substituted hydrocarbyl radical, halogen radical, halogen-substituted hydrocarbyl radical, —OR, —C(O)R′, —CO2R′, —SiR′3and —NR′R″, wherein R′ and R″ are independently selected from the group consisting of H radical, C1-20hydrocarbyl radical, halogen radical, and halogen-substituted hydrocarbyl radical, wherein said Q1to Q5radicals are optionally linked to each other to form a stable bridging group, NHC is any N-heterocyclic carbene ligand, L is either any neutral electron donor ligand, wherein k is a number from 0 to 1 or L is an anionic ligand wherein k is 2, and A?is an anion. Processes using the organometallic complex as catalyst for hydrogenation of aldehydes and ketones are provided. Processes using the organometallic complex as catalyst for the hydrosilylation of aldehydes, ketones and esters are also provided.
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Page column 19
(2008/06/13)
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- Silica Sulfuric Acid: An Efficient Catalyst for the Direct Conversion of Primary and Secondary Trimethylsilyl Ethers to their Corresponding Ethers under Mild and Heterogeneous Conditions
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Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence silica sulfuric acid with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Mirjalili, Bibi Fatemeh,Bamoniri, Abdolhamid
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p. 1877 - 1879
(2007/10/03)
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- The use of Nafion-H as an efficient catalyst for the direct conversion of primary and secondary trimethylsilyl ethers to their corresponding ethers under mild and heterogeneous conditions
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Primary and secondary trimethylsilyl ethers were converted to their corresponding ethers in the presence Nafion-H with good to excellent yields under mild and heterogeneous conditions.
- Zolfigol, Mohammad Ali,Mohammadpoor-Baltork, Iraj,Habibi, Davood,Mirjalili, BiBi Fatemeh,Bamoniri, Abdolhamid
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p. 8165 - 8167
(2007/10/03)
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- Polyoxometalates as reduction catalysts: Deoxygenation and hydrogenation of carbonyl compounds
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Excellent deoxygenation of ketones and aldehydes is achieved with Keggin-type polyoxometalates in the presence of hydrogen (see Equation (1) for an example). The mixed addenda phosphovanadomolybdate [PV2Mo10O4]5- was found to be the best catalyst. X-ray diffraction and IR studies suggest that the polyoxometalates are structurally stable under the strongly reducing conditions.
- Kogan, Vladimir,Aizenshtat, Zeev,Neumann, Ronny
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p. 3331 - 3334
(2007/10/03)
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- Organic reactions catalyzed by methylrhenium trioxide: Dehydration, amination, and disproportionation of alcohols
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Methylrhenium trioxide (MTO) is the first transition metal complex in trace quantity to catalyze the direct formation of ethers from alcohols. The reactions are independent of the solvents used: benzene, toluene, dichloromethane, chloroform, acetone, and in the alcohols themselves. Aromatic alcohols gave better yields than aliphatic. Reactions between two different alcohols could also be used to prepare unsymmetric ethers, the best yields being obtained when one of the alcohols is aromatic. MTO also catalyzes the dehydration of alcohols to form olefins at room temperature, aromatic alcohols proceeding in better yield. When primary (secondary) amines were used as the limiting reagent, direct amination of alcohols catalyzed by MTO gave good yields of the expected secondary (tertiary) amines at room temperature. Disproportionation of alcohols to alkanes and carbonyl compounds was also observed for aromatic alcohols in the presence of MTO. On the basis of the results of this investigation and a comparison with the interaction between MTO and water, a concerted process and a mechanism involving carbocation intermediates have been suggested.
- Zhu, Zuolin,Espenson, James H.
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p. 324 - 328
(2007/10/03)
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- ALKYLATION OF PENTAERYTHRITOL BY PHASE-TRANSFER CATALYSIS 2. Crucial Effect of the Aqueous Sodium Hydroxyde Solution
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The mechanistic aspects of the alkylation of pentaerythritol (2-2'-bis(hydroxymethyl)-1,3-propanediol) (PE) by phase-transfer catalysis have been investigated.The dramatic effect of an excess and renewal of sodium hydroxide solutions on the one hand, and the solubility of the PT catalyst in the organic phase on the other, argue that the selectivity of this reaction appears to be controlled almost completely by the possible protonation of the sodium form of the alkoxide anion of PE (4).This protonation depends on the assumption that water molecules are present in the PT medium, and it based upon the observation that this PT medium is actually a three liquid-layer system.As the unusual layer (catalyst layer) may be readily hydrated, the concentrated sodium hydroxide solution can be no longer considered as an unquestionable desiccant.
- Nouguier, Robert,Mchich, Mohamed
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p. 2477 - 2482
(2007/10/02)
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- Electrogenerated Acid-Assisted Preparation of Ethers from Aldehydes and Ketones
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Symmetrical and unsymmetrical ethers are prepared from carbonyl compounds and alkoxytrimethylsilanes in the presence of hydrosilane by using an electrogenerated acid catalyst.
- Torii, Sigeru,Takagishi, Sadahito,Inokuchi, Tsutomu,Okumoto, Hiroshi
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p. 775 - 776
(2007/10/02)
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- Reduction of carbonyl compounds promoted by silicon hydrides under the influence of trimethylsilyl-based reagents
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The synthetic utility of hydrosilanes under the influence of trimethylsilyl-based reagents as new reducing systems is described. 1,1,3,3-Tetramethyldisiloxane (TMDS) reagent in combination with iodotrimethylsilane or bromotrimethylsilane produces alkyl halides from aldehydes in good to excellent yields.Polymethylhydrosiloxane (PMS) in the presence of iodotrimethylsilane also produces benzyl iodides in excellent yields.On the contrary, PMS reagent was found unsuitable for the synthesis of benzyl bromides.Similary, TMDS reagent in combination with trimethylsilyl triflate produces symmetrical ethers from aldehydes without concomitant formation of competitive products.Under similar conditions, PMS reagent failed to provide the expected symmetrical ethers and Friedel-Crafts products were formed.Reduction of quinones to hydroquinones is also described.
- Aizpurua, Jesus M.,Lecea, Begona,Palomo, Claudio
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p. 2342 - 2347
(2007/10/02)
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- Alkylation of Pentaerythritol and Trimethylolpropane, Two Very Hydrophilic Polyols, by Phase-Transfer Catalysis.
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Two very hydrophilic polyols, pentaerythritol and trimethylolpropane , can be etherified in good yields by phase-transfer catalysis with allyl chloride or heptyl bromide as alkylating agents.Ion pairs solubilities, lipophilicities of catalysts, and nature of the reaction products which are key factors in achievement of this PTC reaction are discussed.
- Nouguier, R. M.,Mchich, M.
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p. 3296 - 3298
(2007/10/02)
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- Synthese des ethers du pentaerythritol par catalyse en transfert de phase. Optimisation de la reaction d'etherification pour leur synthese industrielle
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The very hydrophilic pentaerythritol can be etherified with 1-bromo-heptane by phase transfer catalysis (PTC).The resulting mixture of ethers is an original synthetic additive.The PTC reaction was then optimized to increase the total yield, and to lower the cost of the final product.To our knowledge, it is the first industrial optimization of a PTC reaction.
- Nouguier, Robert,Mchich, Mohamed,Maldonado, Paul,Grangette, Henri
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p. 602 - 607
(2007/10/02)
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- Chemical Conversions using Sheet Silicates: Novel Intermolecular Dehydrations of Alcohols to Ethers and Polymers
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Aliphatic primary alcohols, when intercalated in certain ion-exchanged montmorillonites, react preferentially via an intermolecular nucleophilic displacement of water to give high yields of di-(alk-1-yl) ethers, rather than the competitive intramolecular dehydration to alkenes; an essentially similar process yields polymeric material, poly(phenylenemethylene), from benzyl alcohol, but aliphatic secondary and tertiary alcohols, in contrast, yield alkenes almost exclusively.
- Ballantine, James A.,Davies, Mary,Purnell, Howard,Rayanakorn, Mongkon,Thomas, John M.,Williams, Kevin J.
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p. 427 - 428
(2007/10/02)
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- OXIDATIVE CLEAVAGES OF ALIPHATIC AND CYCLIC IODIDES
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3 Undergoes elimination on treatment with m-chloroperbenzoic acid, performic acid or SO2Cl2/NaOCl, while iodine is retained in the novel peracid dehydrogenation of 9.
- McCabe, Peter Heggison,Jenga, Chine Isaac de,Stewart, Angus
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p. 3679 - 3680
(2007/10/02)
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- SOLID - LIQUID PHASE TRNSFER CATALYSIS USING SOLID SODIUM HYDROXIDE IN PREPARATIVE ETHERS SYNTHESIS
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Preparative ethers synthesis can be performed using P.T.C. if solid sodium hydroxide is used as basic medium.In this case, side reactions ( eg: hydrolysis or elimination ) are avoided.Moreover, secondary disymmetrical ethers can be synthesized starting from an alcohol and a secondary alkyl halide in acceptable yields.
- Dou, H. JM.,Delfort, B.,Hassanaly, P.,Gallo, R.,Kister, J.
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p. 421 - 426
(2007/10/02)
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