- Exploring the catalytic activity of Lewis-acidic uranyl complexes in the nucleophilic acyl substitution of acid anhydrides
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The catalytic activities of several uranyl complexes, such as N,N′-disalicylidene-o-phenelyenediaminato(ethanol)dioxouranium(vi) (UO2(salophen)EtOH), bis(dibenzoylmethanato)(ethanol)dioxouranium(vi) (UO2(dbm)2EtOH), pentakis(N,N-dimethylformamide)dioxouranium(vi) ([UO2(DMF)5]2+), and tetrakis(triphenylphosphine oxide)dioxouranium(vi) ([UO2(OPPh3)4]2+), were examined in the nucleophilic acyl substitution of acid anhydrides. Among them, [UO2(OPPh3)4]2+ was the most efficient to give ethyl acetate and acetic acid from acetic anhydride (Ac2O) and ethanol, and was resistant towards decomposition during the catalytic reaction. Several nucleophiles were also subjected to the catalytic acylation reaction using acetic and pivalic anhydride. Kinetic and spectroscopic studies suggested that [UO2(OPPh3)4]2+ interacts with Ac2O to form [UO2(Ac2O)(OPPh3)3]2+. Interaction of this actual catalyst with additional Ac2O determines the rate of the overall nucleophilic acyl substitution reaction.
- Takao, Koichiro,Akashi, Shin
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p. 12201 - 12207
(2017/03/08)
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- Chemoselective CaO-mediated acylation of alcohols and amines in 2-methyltetrahydrofuran
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Calcium oxide is proposed as an innocuous acid scavenger for the chemoselective synthesis of amide- and ester-type compounds. Although these molecules have wide spread applications in organic and pharmaceutical chemistry, and a large number of routes have been designed for their synthesis, the development of more efficient and environmentally friendly acylation strategies remains an ongoing challenge. The use of CaO allows for the stoichiometric acylation of primary alcohols in the presence of phenols or tertiary alcohols; amines can also be subjected to acylation reactions in the presence of hydroxyl groups. Chirality is obtained through acylation if the starting material is an optically pure alcohol or if a chiral acylating agent is used. Furthermore, the use of 2-methyltetrahydrofuran (2-MeTHF), a more ecofriendly solvent, leads to maximized yields. This protocol is successfully applied to the synthesis of an interesting N-aryloxazolidin-2-one intermediate for the preparation of linezolid-type compounds.
- Pace, Vittorio,Hoyos, Pilar,Alcántara, Andrés R.,Holzer, Wolfgang
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p. 905 - 910
(2013/07/27)
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- Double molecular recognition with aminoorganoboron complexes: Selective alcoholysis of β-dicarbonyl derivatives
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Double duty: Aminoorganoboron (AOB) complexes recognize alcohol and β-dicarbonyl units, and thereby facilitate chemo- and site-selective alcoholysis of the latter (see scheme). The complex activates both reaction partners. This strategy enables C-C, C-N, and C-O bond cleavage in addition/elimination reactions under near neutral pH conditions and provides a new method for functional group conversions. Copyright
- Oishi, Shunsuke,Saito, Susumu
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supporting information; experimental part
p. 5395 - 5399
(2012/06/18)
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- A mild and efficient chemoselective protection of primary alcohols as pivaloyl esters using La(NO3)3·6H2O as a catalyst under solvent-free conditions
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Primary alcohols are selectively and efficiently protected as their pivaloyl esters with pivaloyl chloride in the presence of catalytic amounts of La(NO3)3·6H2O at room temperature under solvent-free conditions in excellent yields. Copyright
- Prabhakar,Suryakiran,Venkateswarlu
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p. 732 - 733
(2008/02/09)
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- Alpha- haloenamine reagents
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The present invention describes immobilized haloenamine reagents, immobilized tertiary amides, methods for their preparation, and methods of use.
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- Hydroesterification of tert-butyl alcohol in room temperature ionic liquids
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Hydroesterification of tert-butyl alcohol with ethanol catalyzed by transition metal triphenylphosphine complexes in the presence of p-toluenesulfonic acid was investigated using room temperature ionic liquids as the reaction medium at 373-413 K and 3-6 MPa of CO. In comparison with the organic solvents as reaction medium, higher conversion was achieved and ethyl tert-valerate could be directly formed in the ionic liquid medium. The products could be separated from the ionic liquids easily due to their immiscibility in this medium.
- Qiao, Kun,Deng, Youquan
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p. 667 - 670
(2007/10/03)
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- The Pd3(dppm)3 (CO)2+ cluster: An efficient electrochemically assisted Lewis acid catalyst for the fluorination and alcoholysis of acyl chlorides
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The dicationic palladium cluster Pd3(dppm)3-(CO)2+ (dppm = bis(diphenylphosphino)methane) reacts with acid chlorides RCOCl (R = n-C6H13, t-Bu, Ph) to afford quantitatively the chloride adduct Pd3(dppm)3(CO)(Cl)+ and the acyl cation RCO+ as the organic counterpart. The dicationic reactive cluster can be reformed by electrolyzing the chloride complex with a copper anode leaving CuCl as a byproduct. The combination of these two reactions provides an electrocatalytic way to form the acylium from the acid chloride. Indeed, in CH2Cl2, 0.2 M NBu4PF6, or NBu4BF4, the electrolysis of the acid chloride in the presence of a catalytic amount of the cluster (1%) gives in good yields the acid fluoride RCOF, arising from the coupling of the acylium with a F- issued from the fluorinated supporting electrolyte. Alternatively, in CH2Cl2 or 0.2 M NBu4ClO4, by operating with an alcohol R′OH as the nucleophile, the electrolysis gives the ester RC(O)OR′ as the only final product.
- Lemaitre, Frederic,Lucas, Dominique,Mugnier, Yves,Harvey, Pierre D.
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p. 7537 - 7540
(2007/10/03)
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- Syntheses based on monocarbon molecules: III.1 hydroethoxycarbonylation of 2-methylpropene in the presence of palladium phosphine complexes at a low pressure of carbon monoxide
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Among the catalytic systems PdCl2(PPh3)2, PdCl2(PPh3)2-PPh3, PdCl2(PPh3)2-TsOH, PdCl2(PPh3)2-PPh3-TsOH, and PdCl2-PPh3-TsOH, the latter is the best catalyst for hydroethoxycarbonylation of 2-methylpentene at a low pressure of carbon monoxide.
- Suerbaev,Shalmagambetov,Zhubanov
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p. 1924 - 1926
(2007/10/03)
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- Reversible protonation of isobutane in liquid superacids in competition with protolytic ionization
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The deuterium distribution observed in isobutane recovered after short contact times with the DF-SbF5 superacid at 0°C shows that a very fast reversible protonation of all C-H bonds occurs before ionization of the alkane, in accord with the Olah σ-basicity concept. Comparison of the amounts of hydrogen with the amount of tert-butyl ions generated during ionization shows that the reaction is purely protolytic in HF containing up to 20 mol % SbF5, but becomes oxidative at higher concentrations.
- Sommer, Jean,Bukala, Jozef,Hachoumy, Mohammed,Jost, Roland
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p. 3274 - 3279
(2007/10/03)
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- Reaction enthalpy of nucleophilic substitution of ethyl iodide in acetonitrile and its mechanistic significance
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Enthalpies of reaction for nucleophilic substitution of ethyl iodide have systematically been determined in acetonitrile. Through the concurrent analysis of empirical correlations between the reaction enthalpies and the specific interaction enthalpies for relevant anions with those between the logarithmic rates and the specific interaction enthalpies, partial desolvation accompanying activation has been deduced to be the major contributor to activation thermodynamic parameters, while the propensity of the reacting central atom in the nucleophilic anion plays a crucial role in determining reaction thermodynamic parameters. Semi-empirical molecular orbital calculations have supported these ideas. The application of the Marcus equation to the analysis of reaction characteristics in these reactions is discussed.
- Kondo, Yasuhiko,Tsukamoto, Tamio,Kimura, Naoko
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p. 1765 - 1769
(2007/10/03)
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- Dual Reaction Channels for Solvolyses of Acyl Chlorides in Alcohol-Water Mixtures
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Rate constants are reported for solvolyses at 0 deg C of trimethylacetyl chloride (3) in 90-30percent v/v acetonitrile-, acetone-, ethanol- and methanol-water mixtures, of adamantane-1-carbonyl chloride (4) in 90-60percent acetone-, ethanol- and methanol-water mixtures, and of cyclopropanecarbonyl chloride (5) in 90-40percent acetone-water.Quantitative product data (acid and ester) are also reported for solvolyses of trimethylacetyl chloride in 98-20percent ethanol- and methanol-water mixtures.Product selectivities (S) show maxima in 90-95percent alcohol-water mixtures, similar to those, reported previously for solvolyses of p-chlorobenzoyl chloride (1a), benzoyl chloride (1b), 2,4,6-trimethylbenzenesulfonyl chloride (2a) and 4-methoxy-2,6-dimethylbenzenesulfonyl chloride (2b).Using rate-rate profiles, logarithms of rate constants are dissected into the competing reaction channels.Given the sharp maxima in S that occur at different alcohol compositions for different substrates, and the link to 'breaks' in rate-rate profiles, the results are consistent with competing mechanisms having different rate-limiting steps.The competing mechanisms involve two broad reaction channels: (1) nucleophilic attack by one molecule of solvent assisted by a second molecule of solvent acting as a general base catalyst-consequently, in aqueous alcohol there are four mechanistic combinations operating simultaneously within this one reaction channel; (2) nucleophilic attack by solvent occurs via a carbocationic reaction within the SN2-SN1 mechanistic spectrum, involving for example, a solvent-separated ion pair intermediate (SN1) or a concerted nucleophilic attack (SN2).
- Bentley, T. William,Shim, Chang Sub
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p. 1659 - 1664
(2007/10/02)
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- Nucleophilic Substitution Reactions of Aliphatic and Aromatic Carboxylate Ions with Ethyl Iodide. Specific Interactions and Isokinetic Relationships in Acetonitrile-Methanol Mixtures
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Transfer enthalpies for the transition-state anions in the reactions of the carboxylate anions adamantane-1-carboxylate, pivalate, benzoate, and 4-nitrobenzoate with ethyl iodide have been determined in acetonitrile-methanol mixtures (AN-MeOH).After the separation of these enthalpies into their constituent terms, i.e., physical interaction and specific interaction enthalpies, the number of methanol molecules hydrogen-bonded to the anion has been evaluated on the basis of the assumption that the isokinetic relationship is realized between activation parameters, which can be identified as physical interaction quantities.An empirical correlalation was observed between that number and the specific interaction enthalpy, ΔHAN->MeOHt,SI, for the anion.On the basis of the AM1 model calculations, discussion is given on the factors which affect the physical interaction enthalpy.
- Kondo, Yasuhiko,Fujiwara, Tadayuki,Hayashi, Akio,Kusabayashi, Shigekazu,Takagi, Tatsuya
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p. 741 - 746
(2007/10/02)
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- The Esterification of Carboxylic Acid with Alcohol over Hydrous Zirconium Oxide
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The esterification of carboxylic acids with alcohols proceeded efficienly with hydrous zirconium oxide to give the corresponding esters in the vapor phase, in the liquid phase, and in an autoclave.The steric hindrance of carboxylic acids and alcohols affected the esterification by lowering the reactivity.With a rise in the reaction temperature, the conversion of the carboxylic acid increased.The dehydration of alcohols was prevented by using hydrous zirconium oxide in spite of the high reaction temperature.The reaction rate is first-order with respect to the concentration of the catalyst and an alcohol and is inversely proportional to thta of the carboxylic acid.Transesterification also proceeded efficiently.
- Takahashi, Kyoko,Shibagaki, Makoto,Matsushita, Hajime
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p. 2353 - 2361
(2007/10/02)
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- REACTION OF ORGANIC AZIDES WITH UNSATURATED COMPOUNDS. IX. PRODUCTS FROM REARRANGEMENT OF 1-ARYLSULFONYL-4,4,5-TRIMETHYL-5-ETHOXY-1,2,3-TRIAZOLINES
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Ethyl N-arylsulfonyl-2,2-dimethylpropanimidates and N-(1,1-dimethyl-2-ethoxy-2-propenyl)arenesulfonamides are obtained in the reaction of arylsulfonyl azides with 2-methyl-3-ethoxy-2-butene.Thus, the intermediate 1-arylsulfonyl-4,4,5-trimethyl-5-ethoxy-1,2,3-triazolines not only rearrange to the imidates but are also converted into unstable 1-arylsulfonyl-2,2,3-trimethyl-3-ethoxyaziridines, which isomerize to the N-substituted arenesulfonamides.
- Semenov, V. P.,Mishin, M. A.,Ogloblin, K. A.
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p. 2149 - 2153
(2007/10/02)
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- Hydrogenolysis of Small Cycloalkanes, XI. - Hydrogenation of Bicyclobutane-1- and -2-carboxylates
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Hydrogenation of ethyl bicyclobutane-2-carboxylate (1) with Pd/C in ethanol at normal conditions leads to 95 percent of ethyl 2-methylbutyrate (2) and 5 percent of ethyl n-valerate (3).The corresponding 1-carboxylic acid ester 8 yields 99 percent of 2 but less than 1 percent of cyclobutane as well as the cis- and trans-2-methylcyclopropanecarboxylates 5 and 9.In this case 2-methylenebutyric and cis- and trans-2-methylcrotonic acid esters (10, 11a, and 12) can be detected as intermediates.From these, conclusions can be made about the mechanism at the catalyst. 5 is the main product with a poisoned catalyst.
- Hertzsch, Winfried,Musso, Hans
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p. 1485 - 1491
(2007/10/02)
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- Esterification of Carboxylic Acids Mediated by Chlorotrimethylsilane
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The reaction of aliphatic and aromatic carboxylic acids with alcohols in presence of chlorotrimethylsilane affords, under mild condition, the corresponding esters in excellent yields.The reaction can be extended to amino acids which also yield the amino esters in high yields.
- Mandal, Arun K.
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- Characterization of Intermediates in the Reaction of Ozone with Di-tert-butylacetylene. A Novel Pivaloylating System
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Reaction of di-tert-butylacetylene (1a) with ozone in -40 deg C aprotic solvents upon warming leads to pivalic anhydride, pivalil, and pivalic acid, with evolution of isobutane, isobutene, carbon dioxide, and carbon monoxide.Spectral and chemical evidence indicated the presence of at least two labile intermediates in the reaction.Ozonolysis of the alkyne in the presence of compounds containing a hydroxyl function led to their pivaloyl derivatives with incorporation of both tert-butyl groups, probably via fragmentation of an adduct of ROH to an intermediate carbonyl oxide.
- Jenkins, Jerry A.,Mendenhall, G. David
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p. 3997 - 4000
(2007/10/02)
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- ACTION DE L'OZONE SUR DES DERIVES VINYLIQUES; REACTIONS CONSERVANT L'ENCHAINEMENT CARBONE.
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Ozone reacts with vinyl derivatives (sulphides, enamines, ethers) and gives abnormal reactions or/and double bond cleavages.
- Strobel, Marie-Paule,Morin, Luc,Paquer, Daniel
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p. 523 - 524
(2007/10/02)
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- Effets de cryptands et activation de bases. VI. Reactions d'organo-lithiens.
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Utilization of the cryptand shows the need of electrophilic catalysis by the Li(1+) ion in the nucleophilic addition of organolithium compounds to ketones, esters, or carboxylic acids.When nucleophilic addition is inhibited, organolithium reagents enolyze ketones or esters.When activated by cryptation of Li(1+), organolithium reagents attack ethers in a few minutes.With alkyl halides, only elimination takes place: exchange and nucleophilic substitution are not observed any longer in the presence of the cryptand.Generally speaking, the cryptand seems to enhance the basicity of the organolithium reagent, and nucleophilicity does not manifest itself any more.
- Perraud, Robert,Handel, Henri,Pierre, Jean-Louis
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p. 283 - 288
(2007/10/02)
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