- Infrared studies of acetophenone and its deuterated derivatives
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The i.r. spectra of acetophenone and their deuterated analogues (-d3, -d5, -d8) in the liquid-phase have been recorded and analyzed in the range 4000-130 cm-1.Additional data on band contours in the gas-phase, in conjuction with the deuteration effects, allowed us to assign all the fundamentals for the four isotopic varieties.A valence force field calculation was also used to support the proposed assignment.
- Gambi, A.,Giorgianni, S.,Passerini, A.,Visinoni, R.,Ghersetti, S.
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- Rearrangements Accompanying the Fragmentation of Ionized 1-Phenylalkan-1-ols
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Some aspects of the fragmentation sequence of 1-phenylalkan-1-ols(C6H5CH(OH)R), which consists of the loss of R(.) followed by the elimination of CO and subsequently of H2, are discussed.Labelling studies and collision activation data of reference compounds allow a mechanism to be proposed for this rearrangement.
- Budzikiewicz, H.,Drabner, G.,Hammes, Ch.
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- Intermolecular hydrogen bonds in water@IL supramolecular complexes
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The role of small amounts of water in ionic liquids (ILs), namely, 1-n-butyl-2,3-dimethylimidazolium imidazolate (BMMI·Im), 2-methylimidazolate (BMMI·MeIm), and pyrazolate (BMMI·Pyr), is examined using NMR spectroscopy and density functional theory (DFT) calculations. The nuclear Overhauser effect (NOE) indicates that a water molecule is trapped inside the ionic network, keeping the ion pair in contact through strong H-bonds involving the hydrogen atoms of water and the nitrogen atoms of the IL anions to give a guest@host supramolecular structure. The formation of the H2O@IL pair complex with different ILs combined with the strong hydrogen bond strength within the complex is responsible for the selective H/D exchange reactions at the imidazolium C2-Me and ketone Cα positions.
- Zanatta, Marcileia,Dupont, Jairton,Wentz, Gabriela Negruni,Dos Santos, Francisco P.
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- A tailored organometallic-inorganic hybrid mesostructured material: A route to a well-defined, active, and reusable heterogeneous iridium-NHC catalyst for H/D exchange
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(Chemical Equation Presented) A tailored hybrid mesostructured material containing regularly distributed imidazolium units, and subsequent transformation of these imidazolium moieties into Ir-NHC (NHC = N-heterocyclic carbene) complexes via the formation of Ag-NHC species in situ and further transmetalation with [{IrCp*Cl2}2], gives a well-defined, active,and reusable Ir-NHC heterogeneous catalyst for H/D exchange reactions (see picture).
- Maishal, Tarun K.,Alauzun, Johan,Basset, Jean-Marie,Coperet, Christophe,Corriu, Robert J. P.,Jeanneau, Erwan,Mehdi, Ahmad,Reye, Catherine,Veyre, Laurent,Thieuleux, Chloe
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- The structure of ethylbenzene as a solute in liquid crystalline solvents via analysis of proton NMR spectra
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Previous attempts to analyze the proton spectrum of ethylbenzene as a solute in nematic liquid crystalline solvents failed, but a successful strategy has now been devised and is described here. The proton spectra of samples of ethylbenzene dissolved in four different liquid crystals have been analyzed to yield sets of the partially-averaged dipolar couplings, D(ij). The couplings are then used to test models for the structure and conformation of this molecule.
- Algieri,Castiglione,Celebre,De Luca,Longeri,Emsley
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- The oxidation of secondary alcohols by dimethyldioxirane: Re-examination of kinetic isotope effects
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The kinetic isotope effects for the oxidation of a series of deuterated isopropanols and a -trideuteromethyl benzyl alcohol by dimethyldioxirane ( 1 ) to the corresponding ketones were determined in dried acetone at 23 ° C. A primary kinetic isotope effect (PKIE) of 5.2 for the oxidation of isopropyl-2-d alcohol by 1 was obtained. The SKIEs for oxidation of a -trideuteromethyl benzyl alcohol and isopropyl-1,1,1,3,3,3-d6 alcohol were found to be 1.07 and 0.98, respectively. Oxidation of isopropanol-d by 1 yielded a k OH /k OD value of 1.12, which is similar to that previously reported for α -methylbenzyl alcohol-d. Both normal and inverse secondary kinetic isotope effect (SKIEs) are observed. Mechanistically, the results indicate that the process is more complex than the previously proposed models.
- Baumstark, Alfons L.,Vasquez, Pedro C.,Cunningham, Mark,Leggett-Robinson, Pamela M.
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- Conversion of xanthyrones into glutaconic anhydride-pyrone (GP) compounds in strong acid media: Selective deuteriation as between chelated and unchelated acetyls
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The structure, and mechanism of formation, of the pyrone-glutaconic anhydride (GP1) obtained by treatment of diaikylxanthophanic enols with concentrated H2SO4 or F3CCO2H, is further supported, and a new example GP2 is prepared. Experiments with deuteriated acids show that deuterium is introduced at C-5′ and the unchelated acetyl of GP1, the second acetyl being apparently protected by chelation. This is supported by benzenoid test examples, though in the naphthalene series acetyl migration also occurs through deacylation/reacylation. An explanation of the protective effect of chelation against acid catalysed enolisation of the acetyl methyl is suggested.
- Crombie, Leslie,Dove, Roderick V.
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- Secondary deuterium isotope effects for enolization reactions
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Secondary α- and β-deuterium isotope effects for enolization reactions and equilibria have been determined by ab initio calculations, 1H NMR spectroscopy, and triton exchange kinetics. Kinetic and equilibrium α-deuterium isotope effects for hydroxide ion-catalyzed enolization of acetaldehyde calculated by ab initio methods are normal and depend on the orientation of the secondary hydrogen with respect to the carbonyl group. The computed transition state structure indicates a small degree of bond rehybridization at the transition state. Experimentally measured secondary isotope effects on the deuteroxide ion-catalyzed proton exchange of acetophenone are k(H)/k(D) = 1.08 ± 0.07 for α-CH3 exchange and k(H)/k(D) = 0.96 ± 0.08 for α-CH2D exchange. For α-CH2T exchange in water, the corresponding secondary isotope effect is k(H)/k(D) = 1.06 ± 0.02, assuming the rule of the geometric mean is valid. These effects are smaller than the calculated equilibrium isotope effect for formation of the enolate ion-water complex: K(H)/K(D) = 1.11-1.22 at the MP2 level. The normal kinetic isotope effects are smaller than might be expected due to a loss in hyperconjugation of the out-of-plane C-H bond and a lag in structural reorganization that contributes to the intrinsic barrier for proton transfer from carbon. Ionization of protonated acetone gives rise to an inverse secondary isotope effect of 0.97/D for the C-L bond adjacent to the carbonyl group and is consistent with a loss in hyperconjugation upon formation of the neutral ketone.
- Alston II, William C.,Haley, Kari,Kanski, Ryszard,Murray, Christopher J.,Pranata, Julianto
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- Spontaneous conversion of prenyl halides to acids: application in metal-free preparation of deuterated compounds under mild conditions
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Here we reveal a simple generation of deuterium halide (DX) from common and inexpensive reagents readily available in a synthetic chemistry laboratory,i.e. prenyl-, allyl-, and propargyl halides, under mild conditions. We envisaged thatin situgeneration of an acid, deuterium halide, would be useful for acid-catalyzed reactions and could be employed for organocatalytic deuteration. The present work reports a metal-free method for deuterium labeling covering a broad range of substrate including phenolic compounds (i.e. flavonoids and stilbenes), indoles, pyrroles, carbonyl compounds, and steroids. This method was also applied for commonly used drugs such as loxoprofen, haloperidol, stanolone, progesterone, androstenedione, donepezil, ketorolac, adrenosterone, cortisone, pregnenolone, and dexamethasone. A gram-scale chromatography-free synthesis of some deuterated compounds is demonstrated in this work. This work provides a simple, clean and by-product-free, site-selective deuteration, and the deuterated products are obtained without chromatographic separation. When applying these initiators for other acid-catalyzed reactions, the deuterium isotope effects of DX may provide products which are different from those obtained from reactions using common acids. Although the mechanism of the spontaneous transformation of prenyl halides to acid is unclear, this overlooked chemistry may be useful for many reactions.
- Darshana, Dhanushka,Kittakoop, Prasat,Mahidol, Chulabhorn,Ruchirawat, Somsak,Sureram, Sanya
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supporting information
p. 7390 - 7402
(2021/09/07)
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- Organocatalytic Deuteration Induced by the Dynamic Covalent Interaction of Imidazolium Cations with Ketones
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In this article, we suggest a new organocatalytic approach based on the dynamic covalent interaction of imidazolium cations with ketones. A reaction of N-alkyl imidazolium salts with acetone-d6 in the presence of oxygenated bases generates a dynamic organocatalytic system with a mixture of protonated carbene/ketone adducts acting as H/D exchange catalysts. The developed methodology of the pH-dependent deuteration showed high selectivity of labeling and good chiral functional group tolerance. Here we report a unique methodology for efficient metal-free deuteration, which enables labeling of various types of α-acidic compounds without trace metal contamination. (Figure presented.).
- Ananikov, Valentine P.,Galkin, Konstantin I.,Gordeev, Evgeniy G.
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p. 1368 - 1378
(2021/01/18)
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- Selectively Upgrading Lignin Derivatives to Carboxylates through Electrochemical Oxidative C(OH)?C Bond Cleavage by a Mn-Doped Cobalt Oxyhydroxide Catalyst
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Oxidative cleavage of C(OH)?C bonds to afford carboxylates is of significant importance for the petrochemical industry and biomass valorization. Here we report an efficient electrochemical strategy for the selective upgrading of lignin derivatives to carboxylates by a manganese-doped cobalt oxyhydroxide (MnCoOOH) catalyst. A wide range of lignin-derived substrates with C(OH)-C or C(O)-C units undergo efficient cleavage to corresponding carboxylates in excellent yields (80–99 %) and operational stability (200 h). Detailed investigations reveal a tandem oxidation mechanism that base from the electrolyte converts secondary alcohols and their derived ketones to reactive nucleophiles, which are oxidized by electrophilic oxygen species on MnCoOOH from water. As proof of concept, this approach was applied to upgrade lignin derivatives with C(OH)-C or C(O)-C motifs, achieving convergent transformation of lignin-derived mixtures to benzoate and KA oil to adipate with 91.5 % and 64.2 % yields, respectively.
- Zhou, Hua,Li, Zhenhua,Xu, Si-Min,Lu, Lilin,Xu, Ming,Ji, Kaiyue,Ge, Ruixiang,Yan, Yifan,Ma, Lina,Kong, Xianggui,Zheng, Lirong,Duan, Haohong
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supporting information
p. 8976 - 8982
(2021/03/16)
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- Ruthenium-Catalyzed Deuteration of Aromatic Carbonyl Compounds with a Catalytic Transient Directing Group
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A novel ruthenium-catalyzed C?H activation methodology for hydrogen isotope exchange of aromatic carbonyl compounds is presented. In the presence of catalytic amounts of specific amine additives, a transient directing group is formed in situ, which directs selective deuteration. A high degree of deuteration is achieved for α-carbonyl and aromatic ortho-positions. In addition, appropriate choice of conditions allows for exclusive labeling of the α-carbonyl position while a procedure for the preparation of merely ortho-deuterated compounds is also reported. This methodology proceeds with good functional group tolerance and can be also applied for deuteration of pharmaceutical drugs. Mechanistic studies reveal a kinetic isotope effect of 2.2, showing that the C?H activation is likely the rate-determining step of the catalytic cycle. Using deuterium oxide as a cheap and convenient source of deuterium, the methodology presents a cost-efficient alternative to state-of-the-art iridium-catalyzed procedures.
- Kopf, Sara,Ye, Fei,Neumann, Helfried,Beller, Matthias
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p. 9768 - 9773
(2021/06/17)
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- Structure Dependence in Asymmetric Deprotonative Fluorination and Fluorocyclization Reactions of Allylamine Derivatives with Linked Binaphthyl Dicarboxylate Phase-Transfer Catalyst
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The asymmetric fluorofunctionalization of γ,γ-disubstituted allylamine derivatives (e.g., 3, 7, and 8) was investigated using our dianionic phase-transfer catalyst. Depending on the substituents on the alkene moiety, the reaction afforded chiral allylic fluorides and fluorinated dihydrooxazines in a highly enantioselective manner (up to 99% ee). The absolute stereochemistry of these products was found to be opposite to that in our previously reported fluorocyclization of γ-monosubstituted allylic amides (e.g., 13 and 14). To probe this interesting phenomenon, we investigated the influence of the substitution pattern of the alkene moiety on the reaction by means of NMR experiments and kinetic studies. The rate laws of the deprotonative fluorination and the fluorocyclization of γ,γ-disubstituted substrates were v = k[cat]0.6, while that of the fluorocyclization of γ-monosubstituted substrates was v = k[substrate][cat]0.4. An exponent of less than 1 suggests the involvement of an aggregated state of the catalyst ion pair in the catalytic cycle. Interestingly, a positive nonlinear effect was observed in the reactions of the γ,γ-disubstituted substrates, while a negative nonlinear effect was observed in the case of the γ-monosubstituted substrates. Thus, the reaction pathway depends on the presence or absence of an alkyl substituent at the γposition of the substrates, and on the basis of our mechanistic studies we propose that the active catalytic species for γ,γ-disubstituted substrates is a catalyst ion pair aggregate, whereas that for γ-monosubstituted substrates is the more active monomeric catalyst ion pair species, even though its concentration would be low.
- Egami, Hiromichi,Hamashima, Yoshitaka,Nishibashi, Kousuke,Niwa, Tomoki,Sato, Hitomi,Ujiie, Kiyoshi,Yamashita, Kenji
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p. 16599 - 16609
(2021/10/20)
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- 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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- Oxidation of Alkenes by Water with H2 Liberation
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Oxidation by water with H2 liberation is highly desirable, as it can serve as an environmentally friendly way for the oxidation of organic compounds. Herein, we report the oxidation of alkenes with water as the oxidant by using a catalyst combination of a dearomatized acridine-based PNP-Ru complex and indium(III) triflate. Compared to traditional Wacker-type oxidation, this transformation avoids the use of added chemical oxidants and liberates hydrogen gas as the only byproduct.
- Ben-David, Yehoshoa,Milstein, David,Tang, Shan
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supporting information
p. 5980 - 5984
(2020/04/27)
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- Br?nsted Acid Catalyzed Friedel–Crafts-Type Coupling and Dedinitrogenation Reactions of Vinyldiazo Compounds
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The direct Friedel–Crafts-type coupling and dedinitrogenation reactions of vinyldiazo compounds with aromatic compounds using a metal-free strategy are described. This Br?nsted acid catalyzed method is efficient for the formation of α-diazo β-carbocations (vinyldiazonium ions), vinyl carbocations, and allylic or homoallylic carbocation species via vinyldiazo compounds. By choosing suitable nucleophilic reagents to selectively capture these intermediates, both trisubstituted α,β-unsaturated esters, β-indole-substituted diazo esters, and dienes are obtained with good to high yields and selectivity. Experimental insights implicate a reaction mechanism involving the selective protonation of vinyldiazo compounds and the subsequent release of dinitrogen to form vinyl cations that undergo intramolecular 1,3- and 1,4- hydride transfer processes as well as fragmentation.
- Arman, Hadi,Dong, Kuiyong,Doyle, Michael P.,Wherritt, Daniel,Zheng, Haifeng
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supporting information
p. 13613 - 13617
(2020/06/10)
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- Catalytic Deuterium Incorporation within Metabolically Stable β-Amino C-H Bonds of Drug Molecules
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An efficient deuteration process of β-amino C-H bonds in various N-alkylamine-based pharmaceutical compounds has been developed. Catalytic reactions begin with the action of Lewis acidic B(C6F5)3 and Br?nsted basic N-alkylamine, converting a drug molecule into the corresponding enamine. The acid/base catalysts also promote the dedeuteration of acetone-d6 to afford a deuterated ammonium ion. Ensuing deuteration of the enamine then leads to the formation of β-deuterated bioactive amines with up to 99% deuterium incorporation.
- Chang, Yejin,Yesilcimen, Ahmet,Cao, Min,Zhang, Yuyang,Zhang, Bochao,Chan, Jessica Z.,Wasa, Masayuki
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supporting information
p. 14570 - 14575
(2019/10/11)
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- Phosphonium Phenolate Zwitterion vs Phosphonium Ylide: Synthesis, Characterization and Reactivity Study of a Trimethylphosphonium Phenolate Zwitterion
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4-Methoxy-3-(trimethylphosphonio)phenolate was obtained from a regioselective addition of PMe3 to p-quinone monoacetal. This compound undergoes hydrogen isotope exchange with D2O or CD3CN, and is capable of catalyzing H/D exchange of CD3CN with substrates bearing weakly acidic hydrogens. It exhibits similar reactivity to phosphorus ylides for olefinations of aldehydes. A possible tautomerization between the phosphonium phenolate zwitterion and phosphonium ylide is proposed for the first time to rationalize the unique reactivity.
- Xiao, Jing,Li, Qiang,Shen, Ruwei,Shimada, Shigeru,Han, Li-Biao
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supporting information
p. 5715 - 5720
(2019/11/22)
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- Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
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Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
- Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
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supporting information
p. 5556 - 5564
(2019/10/28)
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- 3,4-Alkadienyl ketones: Via the palladium-catalyzed decarboxylative allenylation of 3-oxocarboxylic acids
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In this communication, we report a palladium-catalyzed decarboxylative allenylation of benzyl carbonates and tert-butyl carbonates of 2,3-allenols with 3-oxocarboxylic acids. The reaction provides a new and straightforward approach to 3,4-dienyl ketones under mild conditions.
- Zhu, Tonghao,Ma, Shengming
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supporting information
p. 6037 - 6040
(2017/07/10)
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- Nickel-Catalyzed Direct Synthesis of Aryl Olefins from Ketones and Organoboron Reagents under Neutral Conditions
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Nickel-catalyzed addition of arylboron reagents to ketones results in aryl olefins directly. The neutral condition allows acidic protons of alcohols, phenols, and malonates to be present, and fragile structures are also tolerated.
- Lei, Chuanhu,Yip, Yong Jie,Zhou, Jianrong Steve
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supporting information
p. 6086 - 6089
(2017/05/08)
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- Organocatalytic Imidazolium Ionic Liquids H/D Exchange Catalysts
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Simple 1,2,3-trialkylimidazolium cation associated with basic anions, such as hydrogen carbonate, prolinate, and imidazolate, is an active catalyst for the H/D exchange reaction of various substrates using CDCl3 as D source, without the addition of any extra bases or metal. High deuterium incorporation (up to 49%) in acidic C-H bonds of ketone and alkyne substrates (pKa from 18.7 to 28.8) was found at room temperature. The reaction proceeds through the fast and reversible deuteration of the 2-methyl H of the imidazolium cation followed by D transfer to the substrate. The IL acts as a neutral base catalyst in which the contact ion pair is maintained in the course of the reaction. The basic active site is due to the presence of a remote basic site in the anion namely, OH of bicarbonate, NH of prolinate, and activated water in the imidazolate anion. Detailed kinetic experiments demonstrate that the reaction is first order on the substrate and pseudozero order relative to the ionic liquid, due to the fast reversible reaction involving the deuteration of the ionic liquid by the solvent.
- Zanatta, Marcileia,Dos Santos, Francisco P.,Biehl, Cristina,Marin, Graciane,Ebeling, Gunter,Netz, Paulo A.,Dupont, Jairton
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supporting information
p. 2622 - 2629
(2017/03/14)
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- Chelation versus Non-Chelation Control in the Stereoselective Alkenyl sp2 C?H Bond Functionalization Reaction
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A hydroxy group chelation-assisted stereospecific oxidative cross-coupling reaction between alkenes was developed under mild reaction conditions. In the presence of palladium catalyst, the alkenes tethered with hydroxy functionality can couple efficiently with electron-deficient alkenes to form the corresponding multi-substituted olefin products. The hydroxy group on the substrate could play dual roles in reaction, acting as the directing group for alkenyl C?H bond activation and controlling the stereoselectivity of the products.
- Liang, Qiu-Ju,Yang, Chao,Meng, Fei-Fan,Jiang, Bing,Xu, Yun-He,Loh, Teck-Peng
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supporting information
p. 5091 - 5095
(2017/04/24)
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- Palladium-Catalyzed Arylation of Ketones and Acetonitrile with Ortho Alkylation of Aryl Rings: De Novo Synthesis of Tetralines and Benzocycloheptenes
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Palladium-catalyzed α-arylation reactions of ketones with simultaneous ortho alkylation offer 1,2,3-substituted arenes. The reactions of 1,ω-dihaloalkanes also allow facile construction of medicinally important tetralines and benzocycloheptenes.
- Lei, Chuanhu,Cao, Jiajia,Zhou, Jianrong
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supporting information
p. 6120 - 6123
(2016/12/09)
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- SPIRO-THIAZOLONES
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The present invention provides spiro-thiazolones, which act as V1a receptor modulators, and in particular as V1a receptor antagonists, their manufacture, pharmaceutical compositions containing them and their use as medicaments. The present compounds are useful as therapeutics acting peripherally and centrally in the conditions of inappropriate secretion of vasopressin, anxiety, depressive disorders, obsessive compulsive disorder, autistic spectrum disorders, schizophrenia, aggressive behavior and phase shift sleep disorders, in particular jetlag.
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Page/Page column 79
(2016/06/06)
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- Synthesis of α-Aminonaphthalenes via Copper-Catalyzed Aminobenzannulation of (o -Alkynyl)arylketones with Amines
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A copper-catalyzed aminobenzannulation of (o-alkynyl)arylketones with amines has been developed. This method features the use of a cheap copper catalyst, the facile annulation involving various amines, and the good functional group tolerance. (Chemical Equation Presented).
- Zhang, Mingliang,Ruan, Wenqing,Zhang, Hui-Jun,Li, Weiwei,Wen, Ting-Bin
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supporting information
p. 1696 - 1703
(2016/03/01)
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- Transition-metal-free formal decarboxylative coupling of ?±-oxocarboxylates with ?±-bromoketones under neutral conditions: A simple access to 1,3-diketones
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A transition-metal-free formal decarboxylative coupling reaction between ?±-oxocarboxylates and ?±-bromoketones to synthesize 1,3-diketone derivatives is presented. In this reaction, a broad scope of substrates can be employed, and neither a metal-based reagent nor an additional base is required. DFT calculations reveal that this reaction proceeds through a coupling followed by decarboxylation mechanism and the ?±-bromoketone unprecedentedly serves as a nucleophile under neutral conditions. The rate-determining step is an unusual hydrogen-bond-assisted enolate formation by thermolysis.
- He, Zhen,Qi, Xiaotian,Li, Shiqing,Zhao, Yinsong,Gao, Ge,Lan, Yu,Wu, Yiwei,Lan, Jingbo,You, Jingsong
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supporting information
p. 855 - 859
(2015/02/05)
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- A simple method for α-position deuterated carbonyl compounds with pyrrolidine as catalyst
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A simple, cost-effective method for deuteration of carbonyl compounds employing pyrrolidine as catalyst and D2O as deuterium source was described. High degree of deuterium incorporation (up to 99%) and extensive functional group tolerance were achieved. It is the first time that secondary amines are used as catalysts for H/D exchange of carbonyl compounds, which also allow the deuteration of complex pharmaceutically interesting substrates. A possible catalytic mechanism, based on the hydrolysis of 1-pyrrolidino-1- cyclohexene, for this pyrrolidine-catalyzed H/D exchange reaction has been proposed. Pyrrolidine has been shown to be an efficient catalyst for deuteration of carbonyl compounds. The method also allowed the deuteration of complex pharmaceutically interesting substrates. Preliminary experiment showed that the enamine and/or iminium activation modes may be involved. Copyright
- Zhan, Miao,Zhang, Tao,Huang, Haoxi,Xie, Yongmei,Chen, Yuanwei
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p. 533 - 539
(2014/08/05)
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- Vinyl dihydropyrans and dihydrooxazines: Cyclizations of catalytic ruthenium carbenes derived from alkynals and alkynones
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A novel synthesis of 2-vinyldihydropyrans and dihydro-1,4-oxazines (morpholine derivatives) from alkynals and alkynones has been developed. The cyclizations require a mild generation of catalytic ruthenium carbenes from terminal alkynes and (trimethylsilyl)diazomethane followed by trapping with carbonyl nucleophiles. Mechanistic aspects of the new cyclizations are discussed. Setting a trap: A novel synthesis of 2-vinyldihydropyrans and dihydro-1,4-oxazines (morpholine derivatives) from alkynals and alkynones has been developed. The cyclizations require a mild generation of catalytic ruthenium carbenes from terminal alkynes and (trimethylsilyl)diazomethane followed by trapping with carbonyl nucleophiles.
- Cambeiro, Fermin,Lopez, Susana,Varela, Jesus A.,Saa, Carlos
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supporting information
p. 5959 - 5963
(2014/06/10)
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- Acid-catalyzed hydration of alkynes in aqueous microemulsions
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Terminal aromatic alkynes are converted rapidly into ketones in a regioselective manner by treatment of their microemulsions with 0.33 M mineral acid between 80 and 140 °C. Internal and aliphatic acetylenes are likewise hydrated, but require longer reaction periods. The products are easily isolated from the reaction mixtures by phase separation. Replacement of H2O by D2O leads to the formation of trideuteriomethyl ketones. Copyright
- Nairoukh, Zackaria,Avnir, David,Blum, Jochanan
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p. 430 - 432
(2013/04/24)
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- Catalytic C-O bond cleavage of 2-aryloxy-1-arylethanols and its application to the depolymerization of lignin-related polymers
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A ruthenium-catalyzed, redox neutral C-O bond cleavage of 2-aryloxy-1-arylethanols was developed that yields cleavage products in 62-98% isolated yield. This reaction is applicable to breaking the key ethereal bond found in lignin-related polymers. The bond transformation proceeds by a tandem dehydrogenation/reductive ether cleavage. Initial mechanistic investigations indicate that the ether cleavage is most likely an organometallic C-O activation. A catalytic depolymerization of a lignin-related polymer quantitatively yields the corresponding monomer with no added reagent.
- Nichols, Jason M.,Bishop, Lee M.,Bergman, Robert G.,Ellman, Jonathan A.
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supporting information; experimental part
p. 12554 - 12555
(2010/12/19)
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- On the mechanism of ylide-mediated cyclopropanations: Evidence for a proton-transfer step and its effect on stereoselectivity
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In this paper, we describe studies on the cyclopropanation of Michael acceptors with chiral sulfur ylides. It had previously been found that semi-stabilized sulfonium ylides (e.g., Ph-stabilized) reacted with cyclic and acyclic enones and substituted acrylates with high ee and that stabilized sulfonium ylides (e.g., ester-stabilized) reacted with cyclic enones again with high ee. The current study has focused on the reactions of stabilized sulfonium ylides with acyclic enones which unexpectedly gave low ee. Furthermore, a clear correlation of ee with ylide stability was observed in reactions with methyl vinyl ketone (MVK): ketone-stabilized ylide gave 25% ee, ester-stabilized ylide gave 46% ee, and amide-stabilized ylide gave 89% ee. It is believed that following betaine formation an unusual proton transfer step intervenes which compromises the enantioselectivity of the process. Thus, following addition of a stabilized ylide to the Michael acceptor, rapid and reversible intramolecular proton transfer within the betaine intermediate, prior to ring closure, results in an erosion of ee. Proton transfer occurred to the greatest extent with the most stabilized ylide (ketone). When the same reactions were carried out with deuterium-labeled sulfonium ylides, higher ees were observed in all cases since proton/deuteron transfer was slowed down. The competing proton transfer or direct ring-closure pathways that are open to the betaine intermediate apply not only to all sulfur ylides but potentially to all ylides. By applying this model to S-, N-, and P-ylides we have been able to rationalize the outcome of different ylide reactions bearing a variety of substituents in terms of chemo- and enantioselectivity.
- Riches, Samantha L.,Saha, Chandreyee,Filgueira, Noelia Fontan,Grange, Emma,McGarrigle, Eoghan M.,Aggarwal, Varinder K.
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supporting information; experimental part
p. 7626 - 7630
(2010/07/09)
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- Pd-catalyzed oxidative cross-coupling of N-tosylhydrazones with arylboronic acids
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The Pd-catalyzed reaction of N-tosylhydrazones and arylboronic acids provides olefin derivatives. This oxidative cross-coupling is suggested to proceed through a migratory insertion process of a Pd carbene intermediate.
- Zhao, Xia,Jing, Jing,Lu, Kui,Zhang, Yan,Wang, Jianbo
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supporting information; experimental part
p. 1724 - 1726
(2010/07/06)
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- Diastereo- and enantioselective Aza-MBH-type reaction of nitroalkenes to N-tosylimines catalyzed by bifunctional organocatalysts
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The first example of diastereo- and enantioselective aza-MBH-type reaction was accomplished by the asymmetric synthesis of β-nitro-γenamines via a (1R,2R)-diaminocyclohexane thiourea derivative mediated tandem Michael addition and aza-Henry reaction in good yields (up to 95%) and high enantioselectivities (up to 91% ee) and diastereoselectivities (up to 1:99 dr).
- Wang, Xiao,Chen, Yong-Fei,Niu, Liang-Feng,Xu, Peng-Fei
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supporting information; experimental part
p. 3310 - 3313
(2009/12/05)
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- Alcohols for the α-alkylation of methyl ketones and indirect aza-wittig reaction promoted by nickel nanoparticles
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Nickel nanoparticles have been found to activate primary alcohols used for the α-alkylation of ketones or in indirect aza-Wittig reactions. These processes involve hydrogen transfer from the alcohol to the intermediate α,β-unsaturated ketone or imine, respectively. All these reactions are carried out in the absence of any ligand, hydrogen acceptor or base under mild reaction conditions. For the first time nickel is employed as a potential alternative to noble-metal-based catalysts in both reactions. A reaction mechanism is proposed on the basis of some deuteration experiments. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Alonso, Francisco,Riente, Paola,Yus, Miguel
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experimental part
p. 4908 - 4914
(2009/05/27)
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- Triazabicyclodecene: An effective isotope exchange catalyst in CDCl 3
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(Chemical Equation Presented) We describe the first effective H/D exchange reaction with acidic substrates in CDCl3 at room temperature. The particularly mild reaction conditions involved (solvent, base, and temperature) allow the chemoselective deuteration of ketones over esters. An NMR study was conducted with the aim of rationalizing the results obtained in the presence of TBD as catalyst.
- Sabot, Cyrille,Kumar, Kanduluru Ananda,Antheaume, Cyril,Mioskowski, Charles
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p. 5001 - 5004
(2008/02/07)
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- Highly efficient C-C bond-forming reactions in aqueous media catalyzed by monomeric vanadate species in an apatite framework
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A calcium vanadate apatite (VAp), in which PO43- of hydroxyapatite (HAP), Ca10(PO4)6(OH) 2, is completely substituted by VO43- in the apatite framework, was synthesized. Physicochemical analysis of the VAp reveals the presence of isolated VO4 tetrahedron units with a pentavalent oxidation state. The VAp acts as a high-performance heterogeneous base catalyst for various carbon-carbon bond-forming reactions such as Michael and aldol reactions in aqueous media and the H-D exchange reactions using deuterium oxide. For example, a 200-mmol-scale Michael reaction under triphasic conditions proceeded rapidly, with an extremely high turnover number of up to 260 400 and an excellent turnover frequency of 48 s-1. No vanadium leaching was detected during the above reactions, and the catalyst was readily recycled with no loss of activity.
- Hara, Takayoshi,Kanai, Satoko,Mori, Kohsuke,Mizugaki, Tomoo,Ebitani, Kohki,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 7455 - 7462
(2007/10/03)
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- Synthesis of deuterium labeled compounds by KCN-assisted hydrolysis of phosphonium salts
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We developed a facile deuterium labeling method for benzylic or allylic halides or acetates systems. Conversion of the halides or acetates to the corresponding phosphonium salts and the following mild hydrolysis with KCN afforded the deuterium labeled compounds in good yields.
- Lee, Ka Young,Na, Jeong Eun,Lee, Mi Jung,Kim, Jae Nyoung
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p. 5977 - 5981
(2007/10/03)
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- Preparation of deuterium labelled organophosphonium salts (Wittig Salts) under hydrothermal condition catalyzed by molecular sieves
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Organophosphonium salt was converted into deuterium labelled ones under hydrothermal condition in the presence of molecular sieves. The hydrothermal condition can be obtained by either heating D2O in an autoclave or irradiating with microwave to D2O in a sealed vial.
- Yamamoto, Mitsuru,Oshima, Koichiro,Matsubara, Seijiro
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p. 846 - 847
(2007/10/03)
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- Mechanism of Homogeneously and Heterogeneously Catalysed Meerwein-Ponndorf-Verley-Oppenauer Reactions for the Racemisation of Secondary Alcohols
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The mechanism of hydrogen transfer from alcohols to ketones, catalysed by lanthanide(III) isopropoxides or zeolite Beta has been studied. For the lanthanide catalysed reactions, (S)-1-phenyl-(1-2H 1)ethanol and acetophenone were used as case studies to determine the reaction pathway for the hydrogen transfer. Upon complete racemisation all deuterium was present at the 1-position, indicating that the reaction exclusively takes place via a carbon-to-carbon hydrogen transfer. Zeolite Beta with different Si/Al ratios was applied in the racemisation of (S)-1-phenylethanol. In this case the racemisation does not proceed via an oxidation/reduction pathway but via elimination of the hydroxy group and its readdition. This mechanism, however, is not characteristic for all racemisation reactions with zeolite Beta. When 4-tert-butyl cyclohexanone is reduced with this catalyst, a classical MPV reaction takes place exclusively. This demonstrates that zeolite Beta has a substrate dependent reaction pathway.
- Klomp, Dirk,Maschmeyer, Thomas,Hanefeld, Ulf,Peters, Joop A.
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p. 2088 - 2093
(2007/10/03)
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- Preparation, structure, and unique thermal [2 + 2], [4 + 2], and [3 + 2] cycloaddition reactions of 4-vinylideneoxazolidin-2-one
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The terminal allene Cα=Cβ bonds of 4-vinylidene-2-oxazolidinone (2) readily undergo [2 + 2] cycloaddition with a wide variety of terminal alkynes, alkenes, and 1,3-dienes irrespective of their electronic nature under strictly thermal activation conditions (70-100°C) and provide 3-substituted (Z)-methylenecyclobutenes 6, 3-substituted methylenecyclobutanes 7 and 8, and 3-vinylmethylenecyclobutanes 9, respectively, in good to excellent yields. Alkenes react with 2 with complete retention of configuration. The [2 + 2] cycloaddition is concluded to proceed via a concerted [(π2s + π2s)allene + π2s] Hueckel transition state on the basis of experimental evidences and quantum mechanical methods. Some highly polarized enones and nitrile oxide, on the other hand, react with 2 selectively at the internal C4=Cα double bonds and give spiro compounds 10 and 11, respectively. The bent allene bonds (173-176°) and the unique reactivity associated with 2 are attributed to a low-lying LUMO (Cα=Cβ) that is substantiated by a through-space σ*(N-SO2)-π*(Cα= Cβ) orbital interaction.
- Horino, Yoshikazu,Kimura, Masanari,Tanaka, Shuji,Okajima, Toshiya,Tamaru, Yoshinao
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p. 2419 - 2438
(2007/10/03)
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- Oxidation of benzyl alcohols by dimethyldioxirane. The question of concerted versus stepwise mechanisms probed by kinetic isotope effects
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The primary and β-secondary kinetic isotope effects in the oxidation of secondary alcohols with dimethyl dioxirane were measured. The substantial primary and the absence of a β-secondary kinetic isotope effect support a concerted mechanism for the title reaction.
- Angelis, Yiannis S.,Hatzakis, Nikos S.,Smonou, Ioulia,Orfanopoulos, Michael
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p. 3753 - 3756
(2007/10/03)
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- Efficient H-D exchange of aromatic compounds in near-critical D2O catalysed by a polymer-supported sulphonic acid
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Hydrogen atom exchange of aromatic compounds in neutral near-critical D2O has been improved by using a polymer-supported sulphonic acid catalyst. Phenol, aniline, quinoline, and substituted aromatic hydrocarbons are selectively ring-perdeuterated in high yields with insignificant by-product formation at 325 °C for 24 h in D2O/Deloxan.
- Boix, Carmen,Poliakoff, Martyn
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p. 4433 - 4436
(2007/10/03)
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- New transition-state models and kinetics of elimination reactions of tertiary alcohols over aluminum oxide
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A new transition-state model was developed in order to justify the anti intramolecular E2 elimination with cis (Z)-preference over pure alumina and interinolecular E2 elimination with trans (E)-preference over doped alumina. The reactions of model compounds 1,2,3-triphenyl-2-propanol (1), 1,2-diphenyl-2-propanol (2), and 3,3,3-trideuterio-1,2-diphenyl-2-propanol (3) with aluminum oxides with a pH range of 4.5-9.5 and thorium oxide in the temperature range of 200-350 °C in 2-hexanol have been investigated. Over acidic alumina (pH = 4.5 ±0.5), the ratio of E-isomer to Z-isomer (E/Z ? 2) for 2 was found to remain unchanged in this temperature range. At 300 °C, however, Saytzeff elimination favored Hofmann. Over pure alumina the E/Z ratio was equal to 0.650 (2-alkene/1-alkene = 0.750). At equilibrium, the E/Z ratio for 2 was equal to 4.5 with the formation of trace amounts of Hofmann adducts. The ratio of Saytzeff to Hofmann elimination was found to be pH independent. Any decrease in pH caused a slight increase in the E/Z ratio. The average primary kinetic isotope effect (kH/kD) for elimination at 230 °C was equal to 3.775 ± 0.227. The ratio of E/Z over thorium oxide at 300 and 350 °C was similar to that of aluminum oxide at 300 °C, but the Saytzeff elimination was surprisingly favored over Hofmann! The energy of activation (Ea), entropy of activation (AS?), selectivity, isotope effect (kH/kD), and semiempirical calculation (AM1) all agreed with concerted E2 elimination.
- Dabbagh,Salehi, J. Mohammad
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p. 7619 - 7627
(2007/10/03)
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- A convenient method for deuteration at the alpha position of an Oxo group in carbohydrates
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CH-Hydrogens at the alpha position of an oxo group in carbohydrates are readily exchanged in 4:4:2:3 1,4-dioxane-THF-Et3N-D2O.
- El Nemr, Ahmed,Tsuchiya, Tsutomu
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p. 3543 - 3546
(2007/10/03)
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- Kinetics of the enolisation reactions of 3-acetyl-2,5-dimethylfuran and of 2-acetylselenophene
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Rate constants for the enolisation reactions of title compounds have been measured by their rates of halogenation at 25 °C in water, in several buffers, in dilute hydrochloric acid, in dilute sodium hydroxide, and in the presence of some metal ion salts. The results have been compared with those previously obtained from the corresponding reactions of acetophenone and a number of other acetyl heterocycles. Electronegativity of the heteroatoms and the "π-excessive" nature of the heterocyclic rings appear to be the main factors determining the relative reactivities in the acid-catalysed reactions. Bronsted β values and isotope effects, kH/kD, point to a more symmetrical transition state for the investigated acetyl heterocycles than that for acetophenone in the general base-catalysed reaction. Metal-activating factors (MAF), i.e. the catalytic constant for metal-ion (Cu2+, Zn2+, and Ni2+) catalysis, kM, relative to that for proton catalysis, kH, are discussed as an empirical measure of the "hard or soft" character of the carbonyl groups in acyl heterocycles.
- De Maria, Paolo,Fontana, Antonella,Siani, Gabriella,Spinelli, Domenico
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p. 1867 - 1872
(2007/10/03)
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- Formation of cyclopent[a]indene and acenaphthylene from allyl esters of biphenyl mono- and di-carboxylic acids and from biphenyl dicarboxylic anhydrides on flash vacuum pyrolysis at 1000-1100°C
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Flash vacuum pyrolysis at 1000-1100°C of the allyl esters of the three isomeric biphenylcarboxylic acids, of the allyl esters of the 12 biphenyldicarboxylic acids and of the three biphenyldicarboxylic anhydrides gave pyrolysates which were examined by 1H n.m.r. spectroscopy at temperatures below -50°C. In all cases the spectra showed the presence of cyclopent[a]indene and acenaphthylene together with other products. Possible mechanisms for these ring contraction and cyclization processes are discussed and the results of pyrolyses of [2,3-13C2]biphenyl-2,3-dicarboxylic anhydride, and [3,4-13C2]-and (2-2H1)-biphenyl-3,4-dicarboxylic anhydrides are reported.
- Bapat, Jayant B.,Brown, Roger F.C.,Bulmer, Glenn H.,Childs, Trevor,Coulston, Karen J.,Eastwood, Frank W.,Taylor, Dennis K.
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p. 1159 - 1182
(2007/10/03)
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- Classical Organic Reactions in Pure Superheated Water
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At high temperatures and pressures, pure liquid water becomes a surprisingly effective medium for the reactions of organic compounds.It may function simultaneously as a convenient solvent, catalyst, and reagent for reactions which are typically acid- or base-catalyzed.Rapid and highly selective conversion are observed for the majority of the compounds in this study.
- Kuhlmann, Barbara,Arnett, Edward M.,Siskin, Michael
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p. 3098 - 3101
(2007/10/02)
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- Solvolytic Elimination Reactions of Tertiary α-CSNMe2-Substitutedd Systems
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The tertiary benzylic α-CSNMe2-substituted p-nitrobenzoates and trifluoroacetates of general structure Ar(CH3)C(CSNMe2)(OCOR), 7 and 8, solvolyze to give exclusively elimination products H2C=C(CSNMe2)Ar.A Hammett study gave a nonlinear correlation.Variation in rate with solvent ionizing power was small for the unsubstituted trifluoroacetate derivative of 8, and the β-CD3 isotope effect on rate was negligible.There is, however, a large isotope effect (2.5-2.8) in formation of the elimination product when Ph(CH2D)C(CSNMe2)(OCOCF3) solvolyzes.It is concluded that an intermediate must be involved sine the product-determining step and the rate-determining step have differing isotope effects.The likely intermediate is an α-CSNMe2-substituted cation as an ion pair), despite the fact that the reaction has few characteristics of a typical E1 reaction.Tertiary noorbornyl, cyclohexyl, and 2-propyl α-CSNMe2-substituted systems also react to give exclusively elimination products at rates far in excess of α-CONMe2 analogues.It is suggested that α-CSNMe2 cations are also intermediates and that these cations undergo proton loss at an early ion pair stage.These cations are proposed to derive substitantial stabilization by charge delocalization onto sulfur of the thiocarbonyl group. By way of contrast, the secondary system CH3CH(CSNMe2)(OCOCF3), 25, solvolyzes to give mainly a rearranged product CH3CH(CONMe2)(SCOCH3) via a KΔ mechanism involving neighboring thiocarbonyl participation leading to a cyclized ion.
- Creary, Xavier,Hatoum, Holia N.,Barton, Angela,Aldridge, Timothy E.
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p. 1887 - 1897
(2007/10/02)
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- Intrinsic Deuterium Isotope Effects of Deuteriated tert-Butyl Groups on the 13C NMR Spectra of Aromatic Compounds
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The 3Δ-deuterium isotope effects of partially and fully deuteriated tert-butyl groups on the 13C NMR spectra of tert-butylbenzene and derivatives are discussed in detail.It is shown that they correlate with the chemical shift of C-1 of the aromatic ring.It has been demonstrated that when deuterium is replaced with some other substituents, the SCS values of these substituents show a parallel behaviour to the deuterium isotope effects.It is concluded that, for the compounds studied, deuterium isotope effects and substituent chemical shifts can be described on a common basis.
- Balzer, Hartmut H.,Berger, Stefan
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p. 437 - 442
(2007/10/02)
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