- Sensitive and accurate 13c kinetic isotope effect measurements enabled by Polarization transfer
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Polarization transfer is demonstrated as a sensitive technique for the measurement of isotopic fractionation of protonated carbons at natural abundance. This method allows kinetic isotope effects (KIEs) to be determined with substantially less material or shorter acquisition time compared with traditional experiments. Computations quantitatively reproduce the KIEs in a Diels-Alder reaction and a catalytic glycosylation. The glycosylation is shown to occur by an effectively concerted mechanism.
- Kwan, Eugene E.,Park, Yongho,Besser, Harrison A.,Anderson, Thayer L.,Jacobsen, Eric N.
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- Kinetics of Diels-Alder reaction of maleic anhydride and isoprene in supercritical CO2
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The kinetics of the reaction of maleic anhydride and isoprene (reaction 1) in supercritical CO2 was studied over an extended concentration range, from 5 × 10-5 to 1.3 × 10-2 mole fractions of maleic anhydride and isoprene at 60°C and 100 atm. The apparent rate constant of the reaction was concentration dependent, in contrast with the published data. The observed disagreement was explained based on the low solubility of maleic anhydride in supercritical CO2. The interpretation was confirmed by the visual observation of another (liquid) phase under the experimental conditions of the earlier works. The solubility of maleic anhydride in supercritical CO2 was directly measured by sampling and analyzing the supercritical phase. Positive dependencies inferred negative apparent volume of activation. The results obtained in the true one-phase supercritical conditions showed strong negative pressure dependencies of the rate constant of reaction 1.
- Krasnoperov,Glebov,Krishtopa,Stepanov
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- Synthesis and identification of epoxy derivatives of 5-methylhexahydroisoindole-1,3-dione and biological evaluation
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Cyclic imides belong to a well-known class of organic compounds with various biological activities, promoting a great interest in compounds with this functional group. Due to the structural complexity of some molecules and their spectra, it is necessary to use several spectrometric methods associated with auxiliary tools, such as the theoretical calculation for the structural elucidation of complex structures. In this work, the synthesis of epoxy derivatives of 5-methylhexahydroisoindole-1,3-diones was carried out in five steps. Diels–Alder reaction of isoprene and maleic anhydride followed by reaction with m-anisidine afforded the amide (2). Esterification of amide (2) with methanol in the presence of sulfuric acid provided the ester (3) that cyclized in situ to give imides 4 and 4-ent. Epoxidation of 4 and 4-ent with meta-chloroperbenzoic acid (MCPBA) afforded 5a and 5b. The diastereomers were separated by silica gel flash column chromatography, and their structures were determined by analyses of the spectrometric methods. Their structures were confirmed by matching the calculated1 H and13 C NMR chemical shifts of (5a and 5b) with the experimental data of the diastereomers using MAE, CP3, and DP4 statistical analyses. Biological assays were carried out to evaluate the potential herbicide activity of the imides. Compounds 5a and 5b inhibited root growth of the weed Bidens pilosa by more than 70% at all the concentrations evaluated.
- Alvarenga, Elson S.,Torrent, Kariny B. A.
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- High-Pressure Fourier Transform Infrared Spectroscopy Study of the Diels-Alder Reaction of Isoprene and Maleic Anhydride in Supercritical Carbon Dioxide
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A high-pressure FTIR spectroscopy was used to make an in situ study on the Diels-Alder reaction of isoprene and maleic anhydride catalyzed with aluminum chloride in supercritical carbon dioxide at 306 K and 7.45 and 7.85 MPa, suggesting a two-step mechanism and showing a pressure effect.
- Ikushima, Yutaka,Saito, Norio,Arai, Masahiko
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- Silica-supported chlorometallate(iii) ionic liquids as recyclable catalysts for Diels-Alder reaction under solventless conditions
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A range of Lewis acidic metal chlorides were tested as homogeneous catalysts in a model Diels-Alder reaction; AlCl3and GaCl3performed best in terms of conversion andendo : exoselectivity. Based on this outcome, the corresponding chlorometallate(iii) ionic liquids were tested as homogeneous catalysts, without a decrease in performance compared to the chlorides. Finally, these ionic liquids were heterogenised by covalent tethering of the cation onto a multimodal porous silica support; such supported chlorogallate(iii) ionic liquids are reported for the first time. Supported chlorometallate(iii) ionic liquids were used as recyclable heterogeneous catalysts for the Diels-Alder reaction under solventless conditions. High yields (99%) and highendo-selectivities (95%) were obtained after very short reaction times (5 min) at near-ambient temperature (25 °C).
- Chrobok, Anna,Jarz?bski, Andrzej,Latos, Piotr,Markiton, Magdalena,Matuszek, Karolina,Swad?ba-Kwa?ny, Ma?gorzata,Szymańska, Katarzyna
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p. 8129 - 8137
(2020/10/19)
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- A dehydrogenative diels-alder reaction of prenyl derivatives with 2,3-dichloro-5,6-dicyanobenzoquinone
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An efficient dehydrogenative Diels-Alder (DHDA) reaction of prenyl derivatives with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) has been developed under mild conditions, leading to a series of cyclohexene derivatives with good to excellent yields and excellent diastereoselectivity.
- Feng, Hong-Xia,Wang, Yuan-Yuan,Chen, Jie,Zhou, Ling
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supporting information
p. 940 - 944
(2015/03/30)
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- Hydrogen-bond-rich ionic liquids as effective organocatalysts for Diels-Alder reactions
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The synthesis and characterisation of new hydrogen-bond-rich ionic liquids and studies of their catalytic performance in Diels-Alder reactions are described. d-Glucose and chloroalcohols were used as the raw materials and as the sources of hydroxyl groups for the synthesis of ionic-liquid cations, whereas weakly coordinating bis(trifluoromethylsulfonyl)imide was used as the anion. The new ionic liquids were analysed by 1H and 13C NMR spectroscopy and by ESI-MS experiments, which confirmed their structures. In addition, the thermal data of the studied ionic liquids measured by differential scanning calorimetry and thermogravimetric analysis showed that these compounds tend to form a glass at temperatures in the range of -29°C to -16°C and are thermally stable from ambient temperature to at least 430°C, most likely because of the presence of bis(trifluoromethylsulfonyl) imide anions. The performance of the ionic liquids in the model reaction of cyclopentadiene with diethyl maleate or methyl acrylate was investigated. The studied ionic liquids showed high activity even when present in catalytic amounts (4 mol% with respect to the dienophile). An increase in the number of hydroxyl groups present in the ionic liquid structure resulted in higher reaction rates. This journal is the Partner Organisations 2014.
- Erfurt, Karol,Wandzik, Ilona,Walczak, Krzysztof,Matuszek, Karolina,Chrobok, Anna
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p. 3508 - 3514
(2014/07/08)
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- Novel diethyl-methyl-hexahydro-isobenzofurans and their use in perfume compositions
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The present invention is directed to novel diethyl-methyl-hexahydro-isobenzofuran compounds and a method of improving, enhancing or modifying a fragrance formulation through the addition of an olfactory acceptable amount of these novel compounds.
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Paragraph 0022; 0023
(2014/11/27)
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- Solvent-free Diels-Alder reaction in a closed batch system
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Solvent-free Diels-Alder reactions were carried out by heating a mixture of a volatile diene, such as 1,3-butadiene, isoprene, or 2,3-dimethyl-1,3- butadiene, and a dienophile, such as methyl vinyl ketone, methyl acrylate, or maleic anhydride, in a closed batch reactor. High yields of Diels-Alder products were obtained without using solvents and catalysts within a short reaction time in most of the reactions. In particular, several reactions of dienophiles with 1,3-butadiene, which is known as a diene with low reactivity because of its gaseous form, also proceeded with high yields of Diels-Alder products in the closed batch reactor under conditions pressured by the reactant vapor. Solvent-free reactions provided high yields compared to reactions in solvent since the reaction heat directly resulted in increasing the reaction temperature and pressure. Energy in the exothermic reaction was used effectively in the closed batch system under solvent-free conditions.
- Sun, Daolai,Sato, Fumiya,Yamada, Yasuhiro,Sato, Satoshi
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p. 276 - 282
(2013/05/08)
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- Scale-up of microwave-promoted reactions to the multigram level using a sealed-vessel microwave apparatus
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A range of synthetic transformations have been scaled up successfully using a sealed-vessel multimode microwave unit. These include metal-catalyzed couplings, synthesis of heterocycles, reactions under an atmosphere of reactive gas and two-step one-pot procedures. Also, observations have been made along the way that are of use to chemists addressing scale-up of microwave-promoted reactions.
- Bowman, Matthew D.,Schmink, Jason R.,McGowan, Cynthia M.,Kormos, Chad M.,Leadbeater, Nicholas E.
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p. 1078 - 1088
(2013/01/03)
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- Aqueous catalysis: Methylrhenium trioxide (MTO) as a homogeneous catalyst for the Diels-Alder reaction
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The title compound proves to be an effective and efficient catalyst for the Diels-Alder reaction when the dienophile is an α,β-unsaturated ketone or aldehyde. It is especially effective in water. Equal amounts of any such dienophile and any of six representative dienes (isoprene, 2-methyl-1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, cyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,3-cyclohexadiene) were used, along with 1% MTO. The reactions gave usually > 90% isolated yield of the cycloaddition product except for the larger dienophiles. Nearly exclusively, there was formed one product isomer, the same one that usually predominates. The reactions were often run in chloroform (mostly) and in other organic solvents. A select number were carried out in water, where the reactions gave a greater product yield in a considerably shorter time. Water, itself, is known to enhance the rates of Diels-Alder reactions, but MTO exerts an additional accelerating effect. Kinetics studies were carried out to show that the rate is proportional to the catalyst concentration. The products do not inhibit the reaction. The desirability of MTO as a Diels-Alder catalyst stems from a combination of favorable properties: the inertness to air/oxygen, the tolerance for many substrates, the use of an aqueous medium, and the absence of product inhibition. The initial step appears to be the (weak) coordination of the carbonyl oxygen to the electropositive rhenium center. Steric crowding around rhenium inhibits reactions of the larger dienophiles.
- Zhu, Zuolin,Espenson, James H.
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p. 3507 - 3512
(2007/10/03)
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- Process for preparing substituted phthalic anhydrides
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A process for preparing substituted phthalic anhydrides, e.g. 4-methylphthalic anhydride, in which the Diels-Alder addition product of a conjugated diene, e.g. isoprene, and maleic anhydride is reacted with bromine in the presence of an acid acceptor. Typical acid acceptors include dimethylformamide and pyridine.
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- Preparation of substituted phthalic anhydrides
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A process for preparing substituted phthalic anhydrides, example 4-methylphthalic, in which the Diels-Alder addition product of a conjugated diene, example isoprene, and maleic anhydride is reacted with sulfur in the presence of a catalyst. The catalyst is zinc oxide and 2-mercaptobenzothiazole. This reaction is carried out at elevated temperatures. A resulting thio derivative by-product can further be reacted with water at elevated temperatures in the presence of catalytic amounts of a base to form 4-methylphthalic anhydride. This base can be sodium hydroxide or N,N,N', N'-tetramethylguanidine. o-Dichlorobenzene can be added to prevent solids distillation during the process.
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- Reaktivity of Substituted 1,3-Butadienes in Diels-Alder-Reactions
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Kinetic data for the reaction of substituted 1,3-dienes with tetracyanoethylene (TCNE) and other dienophiles are interpreted in terms of the FMO-model.While the expectations are fulfilled qualitatively, the kinetic data cannot be correlated quantitatively.This shows that in Diels-Alder reactions besides HOMO-LUMO separation other factors play an important role, for instance the 1,4-distance in the diene and the conformational equilibrium cisoid transoid of the diene.The kinetic data are in accord with a one-step mechanism of the cycloaddition reaction.
- Ruecker, Christa,Lang, Dietrich,Sauer, Juergen,Friege, Henning,Sustmann, Reiner
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p. 1663 - 1690
(2007/10/02)
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