- Thermal molecular beam matrix spectroscopy of cyclobutanol: temperature dependence of lineshapes and the conformation problem
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Thermal molecular beam spectra of cyclobutanol isolated in Ar and Xe matrices and the temperature dependence of the ν(OH) Raman line are reported.Six matrix bands are shown by lineshape analysis to consist of 4-6 components which systematically decrease and increase with increasing temperature of the molecular beam source.Data on lineshape parameters and relative intensities are reported.Likewise the ν(OH) Raman band is shown to consist of four components which behave with respect to temperature dependence analogously to the matrix bands.The results will be discussed in terms of two models.
- Gunde, R.,Guenthard, Hs. H.
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Read Online
- Synthesis method of cyclobutanone
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The invention provides a synthesis method of cyclobutanone. The method taking cyclopropanecarboxylic acid as a raw material comprises the following steps: reducing the raw material into cyclopropylmethanol, rearranging the cyclopropylmethanol under an acidic condition to obtain cyclobutanol, and carrying out TEMPO oxidation to obtain cyclobutanone. The method has the following advantages: the rawmaterials are cheap, the operation is simple, the total yield is high, and the product with the purity of 99% can be obtained through simple post-treatment. The method produces less three wastes and is suitable for large-scale production.
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Paragraph 0015; 0017; 0018
(2020/06/02)
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- Ru-Photoredox-Catalyzed Decarboxylative Oxygenation of Aliphatic Carboxylic Acids through N-(acyloxy)phthalimide
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Decarboxylative aminoxylation of aliphatic carboxylic acid derivatives with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) in the presence of ruthenium photoredox catalysis is reported. The key transformation entails a highly efficient photoredox catalytic cycle using Hantzsch ester as a reductant. The ensuing alkoxyamine can be readily converted to the corresponding alcohol in one pot, representing an alternative approach to access aliphatic alcohols under photoredox conditions.
- Zheng, Chao,Wang, Yuting,Xu, Yangrui,Chen, Zhen,Chen, Guangying,Liang, Steven H.
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supporting information
p. 4824 - 4827
(2018/08/24)
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- Baeyer–Villiger monooxygenase-catalyzed desymmetrizations of cyclobutanones. Application to the synthesis of valuable spirolactones
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A series of γ-butyrolactone derivatives, including some spiranic ones, was obtained through desymmetrization of the corresponding prochiral 3-substituted cyclobutanones via Baeyer–Villiger monooxygenase (BVMO)-catalyzed oxidation. After reaction optimization using several commercial enzymes, both antipodes of various lactones were synthesized in most cases with >90% conversion and >80% enantiomeric excess under mild reaction conditions. In some cases alcohol formation was also observed (up to 40% conversion) as an undesired side reaction due to the presence of alcohol dehydrogenases in these preparations. Selected transformations were achieved on a 100 mg scale showing the possibilities of these oxidative biocatalysts as a new source of highly interesting compounds.
- Rodríguez-Mata, María,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,García-Cerrada, Susana,Mendiola, Javier,de Frutos, óscar,Collado, Iván
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supporting information
p. 7268 - 7275
(2016/10/26)
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- Synthesis and kinetic regularities of the thermal decomposition of new hydrotrioxides of cyclic alcohols
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Cyclic hydrotrioxides were synthesized by low-temperature (?78 °C) ozonolysis of a series of cyclic alcohols and identified using 1H NMR spectra. The kinetic regularities of the thermal decomposition of the synthesized hydrotrioxides were studied. The experimental proof of the induced decomposition of alcohol hydrotrioxides was obtained for the first time using cyclohexanol hydrotrioxide as an example. The influence of cyclic substituents on the thermal stability of the hydrotrioxides is shown.
- Grabovskiy,Khalitova,Fedorova,Lobov,Rol’nik,Kabal’nova
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p. 464 - 468
(2017/03/08)
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- Application of three-legged piano-stool cyclopentadienyl-N-heterocyclic carbene iron(II) complexes as in situ catalysts for the transfer hydrogenation of ketones
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A one pot system has been developed based on nine related 1,3-dialkylated imidazolium salts for the in situ generation of N-heterocyclic carbene iron(II) complexes in which the complexes were directly tested as catalysts for the transfer hydrogenation of ketones. This is a simplified reproducible process that aims to eliminate unnecessary purification steps for the isolation of such catalysts prior to application. Complexes 10-12 have been prepared under similar conditions, isolated and structurally characterized by spectroscopic and crystallographic methods. Solid state structures of the three complexes were similar and showed distorted octahedral three-legged piano stool geometry around each iron center similar to reported complexes bearing related ligands. As a basis for comparison with the in situ catalyzed systems, the isolated complexes were also tested as catalysts for the transfer hydrogenation of ketones. As a result, under optimized reaction conditions, all the in situ generated catalysts were found to provide excellent activities similar to those based on the isolated complexes with moderate to excellent conversions to the desired alcohol products. Turn over numbers up to 200 at a conversion of 100% was recorded for a wide range of aliphatic, aromatic and cyclic ketones.
- Bala, Muhammad D.,Ikhile, Monisola I.
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- Transition metal free transfer hydrogenation of ketones promoted by 1,3-diarylimidazolium salts and KOH
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An efficient transition metal free and greener catalytic system was developed for the selective transfer hydrogenation of saturated ketones to alcohols. This was achieved by the use of 1,3-diarylimidazolium salts in the presence of KOH as a promoter for the reaction. When the range of substrates was expanded to include unsaturated ketones, selective reduction of the double bond occurred. The catalyst efficiency was comparable to some established transition metal catalyzed systems. The current system utilizes mild aerobic reaction conditions compared to the inert atmosphere conditions required for the corresponding metal based systems.
- Ikhile, Monisola Itohan,Nyamori, Vincent Onserio,Bala, Muhammad Dabai
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p. 4925 - 4928,4
(2020/07/31)
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- Restricted rotation due to the lack of free space within a capsule translates into product selectivity: Photochemistry of cyclohexyl phenyl ketones within a water-soluble organic capsule
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The rotational mobility of organic guest molecules when included within a confined capsule is restricted and this feature could be translated into product selectivity as established with the photochemical behavior of cyclohexyl phenyl ketones. The Royal Society of Chemistry.
- Kulasekharan, Revathy,Choudhury, Rajib,Prabhakar, Rajeev,Ramamurthy
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body text
p. 2841 - 2843
(2011/05/05)
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- A thermodynamic study of ketoreductase-catalyzed reactions 2. Reduction of cycloalkanones in non-aqueous solvents
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The equilibrium constants for the ketoreductase-catalyzed reactions (cycloalkanone + 2-propanol = cycloalkanol + acetone) have been measured in n-hexane, n-pentane, and supercritical carbon dioxide SCCO2 (pressure = (8.0 to 12.0) MPa). The cycloalkanones included in this study were: cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone, and cyclooctanone. The equilibrium constants for the reactions involving cyclobutanone and cyclohexanone were measured in n-hexane over the range T = (288.35 to 308.05) K. The thermodynamic quantities at T = 298.15 K are: K = (0.763 ± 0.001); ΔrGm=(0.670±0.002)kJ·mol-1; ΔrHm=-(1.09±0.11) kJ·mol-1, and ΔrSm=-(5.9±0.4)J·K-1·mol-1 for the reaction involving cyclobutanone; and K = (15.7 ± 0.2); ΔrGm=-(6.82±0.02)kJ·mol-1; ΔrHm=-(4.6±1.0) kJ·mol-1, and ΔrSm=(7.4±3.3)J·K-1·mol-1 for the reaction involving cyclohexanone, respectively. An inspection of the equilibrium constants for these reactions in n-hexane, n-pentane, and SCCO 2 shows that solvent dependence is not significant. The equilibrium constants of cycloalkanones decrease with increasing value of the number of carbons, NC with the exception of cyclohexanone. The cyclohexanol, which adopts a nearly strainless, idealized tetrahedral conformation around each carbon, is thermodynamically favored and more stable compared to other cycloalkanol rings, and this is reflected in the significantly higher value of the equilibrium constant obtained for this reaction. Comparisons with results obtained by using two independent thermochemical routes are also made.
- Tewari, Yadu B.,Phinney, Karen W.,Liebman, Joel F.
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p. 388 - 395
(2008/02/11)
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- Salt-free process for the production of cyclobutanone
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A process for the production of cyclobutanone comprises: (1) isomerization of cyclopropylmethanol to cyclobutanol in the presence of an acidic heterogeneous catalyst; and (2) dehydrogenation at a heterogeneous catalyst to form cyclobutanone.
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- Salt-free preparation of cyclobutanone
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A salt-free process for preparing cyclobutanone, including isomerizing cyclopropylmethanol, preferably in aqueous solution, in the presence of an acidic heterogeneous catalyst to form cyclobutanol and, preferably after extraction and removal of the extractant, dehydrogenating the cyclobutanol over a heterogeneous catalyst.
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- Diplogelasinospora grovesii IMI 171018, a new whole cell biocatalyst for the stereoselective reduction of ketones
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A screening of 416 strains (71 bacterial strains, 45 actinomycetes, 59 yeast, 60 basidiomycetes, 33 marine fungi and 148 filamentous fungi) has been performed to look for microorganisms that display reductase activity in the absence of oxidase activity. A new microorganism, Diplogelasinospora grovesii IMI 171018 (a nonpathogen strain), was isolated and showed very high activity and stereoselectivity in the reduction of cyclic ketones. The fungus was selected due to its selectivity towards monocyclic and bicyclic ketones and its easy culture conditions, which allow an easy scale-up. D. grovesii is more active in the reduction of conventional ketones than S. cerevisiae type II (from Sigma) and can work in the presence of high ketone concentrations (2 = 0.549) and can be used to explain and to predict the structure of ketones that can or cannot be reduced by this microorganism.
- Carballeira, Jose D.,Alvarez, Emilio,Campillo, Mercedes,Pardo, Leonardo,Sinisterra, Jose V.
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p. 951 - 962
(2007/10/03)
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- Fragmentation of cyclobutoxychlorocarbene: The cyclopropylcarbinyl/cyclobutyl cations revisited
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Fragmentations of cyclobutoxychlorocarbene (13, kfrag= 7.1 × 105 s-1) and cyclopropylmethoxychlorocarbene (14, kfrag = 7.6 × 105 s-1) in MeCN proceed to tight and distinct [R+ OC Cl-] ion pairs, which collapse to different distributions of cyclopropylcarbinyl, cyclobutyl and allylcarbinyl chlorides. B3LYP/6-31G* calculations support these conclusions, affording computed fragmentation activation energies of 6.4 (13) and 3.0 (14) kcal mol-1.
- Moss, Robert A.,Zheng, Fengmei,Johnson, Lauren A.,Sauers, Ronald R.
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p. 400 - 406
(2007/10/03)
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- Prodrugs activated by targeted catalytic proteins
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Prodrugs that are activated by and conjugated to a catalytic antibody conjugated to a moiety that binds to a tumor cell population are provided.
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- Thermodynamic and nuclear magnetic resonance study of the reactions of α- and β-cyclodextrin with acids, aliphatic amines, and cyclic alcohols
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Titration calorimetry was used to determine equilibrium constants and standard molar enthalpy, Gibbs energy, and entropy changes for the reactions of a series of acids, amines, and cyclic alcohols with α- and β-cyclodextrin. The results have been examined in terms of structural features in the ligands such as the number of alkyl groups, the charge number, the presence of a double bond, branching, and the presence of methyl and methoxy groups. The values of thermodynamic quantities, in particular the standard molar Gibbs energy, correlate well with the structural features in the ligands. These structural correlations can be used for the estimation of thermodynamic quantities for related reactions. Enthalpy-entropy compensation is evident when the individual classes of substances studied herein are considered, but does not hold when these various classes of ligands are considered collectively. The NMR results indicate that the mode of accommodation of the acids and amines in the α-cyclodextrin cavity is very similar, but that the 1-methyl groups in 1-methylhexylamine and in 1-methylheptylamine and the N-methyl group in N-methylhexylamine lie outside the α-cyclodextrin cavity. This latter finding is consistent with the calorimetric results. Many of the thermodynamic and NMR results can be qualitatively understood in terms of van der Waals forces and hydrophobic effects.
- Rekharsky, Mikhail V.,Mayhew, Martin P.,Goldberg, Robert N.,Ross, Philip D.,Yamashoji, Yuko,Inoue, Yoshihisa
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- Dynamic models for the thermal deazetization of 2,3-diazabicyclo[2.2.1]hept-2-ene
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Kinetic studies on the thermal nitrogen extrusion from 2,3-diazabicyclo[2.2.1]hept-2-ene-exo,exo-5,6-d2 are reported. The ratio of rate constants for formation of the label-isomeric products (bicyclo[2.1.0]pentane-exo,exo-2,3-d2 and -endo,endo-2,3-d2) is found to exhibit no statistically significant temperature dependence. A comparison of gas-phase and solution-phase results is presented. The results are interpreted in terms of two complementary dynamic models. In the first, classical trajectory calculations are run on a three-dimensional projection (two geometric coordinates) of the potential energy hypersurface. These calculations correctly identify the major product, and reproduce the near temperature-independence of the rate-constant ratio, but do not match the ratio quantitatively. Modification of the trajectory calculations to simulate the effect of collisions with solvent molecules also qualitatively matches the observed difference between gas-phase and solution-phase behavior. In the second model, the vector of atomic displacements corresponding to the reaction coordinate at the transition state for nitrogen loss is identified by both semiempirical and ab initio calculations. The components of this vector pointing along the paths to the post-transition-state minima are computed and are shown to lead to a prediction of the product ratio that is in good (if partly fortuitous) agreement with the experimental result. The vector model is used to predict isotope effects on the product ratio, which are then investigated experimantally with 2,3-diazabicyclo[2.2.1]hept-2-ene-endo,endo-1,4,5,6,7,7-d6 and -endo-7-d.
- Lyons, Barbara A.,Pfeifer, J?rg,Peterson, Thomas H.,Carpenter, Barry K.
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p. 2427 - 2437
(2007/10/02)
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- Reactions of alkali metal anions. XV. Reaction of ketones with alkali metal anions
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The potassium anions were found to react with ketones to39 yield both alcoholates and enolates. On the basis of the ESR and K NMR measurements the mechanism of this reaction is proposed. According to the proposed mechanism in the first step a ketyl radical is formed which after disproportionation yields an enolate and an alcoholate but only in the case of ketones having hydrogen atom in α-position in respect to carbonyl group.
- Jedlinski,Misioiek,Giowkowski,Janeczek,Wolinska
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p. 3547 - 3558
(2007/10/02)
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- DIRECT FORMATION OF EPOXYALKYLCOPPER REAGENTS FROM ACTIVATED COPPER AND EPOXYALKYL BROMIDES AND THEIR INTRAMOLECULAR CYCLIZATIONS
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Epoxyalkylcopper compounds have readily been prepared by the direct oxidative addition of active copper to epoxyalkyl halides.The intramolecular cyclization of the epoxyalkylcopper reagents via an epoxide cleavage process is described.Significantly, many functional groups can be present in the bromoepoxides yielding highly functionalized carbocycles.The regioselectivity of this cyclizations is affected by the connecting chain length, substitution pattern, reaction solvent, and the CuI-phosphine complex used to generate the copper.
- Wu, Tse-Chong,Rieke, Reuben D.
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p. 6753 - 6756
(2007/10/02)
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- SELECTIVE CYCLOALKANONE REDUCTIONS USING ALUMINUM AMALGAM
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Aluminum amalgam in aqueous tetrahydrofuran reduces cycloalkanones to their respective alcohols.The reaction exhibits sensitivity to the ring size and steric environment of the ketone.
- Hulce, Martin,LaVaute, Timothy
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p. 525 - 528
(2007/10/02)
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- Modification of Photochemical Reactivity by Cyclodextrin Complexation: Alteration of Photochemical Behavior via Restriction of Translational and Rotational Motions. Alkyldeoxybenzoins
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The photochemical behavior of alkyldeoxybenzoins has been investigated in isotropic organic solvents, in aqueous cyclodextrin solutions, and when they are bound to cyclodextrin in the solid state.Norrish type I and type II reactions occur in these media and the product distributions resulting from these primary processes are dependent on the medium.While in organic solvents the type I and the type II products are obtained in equal amounts, in the aqueous cyclodextrin solution the type II products are formed in large excess.In the solid state the type II products constitute more than 90percent of the product distribution.Ratios of products resulting via elimination and cyclization from the type II 1,4-diradical are also altered by the host cyclodextrin.Conformational and super-cage effects have been invoked to rationalize the dramatic alteration of the photobehavior of alkyldeoxybenzoins by the cyclodextrin.
- Reddy, G. Dasaratha,Ramamurthy, V.
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p. 5521 - 5528
(2007/10/02)
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- Gas-Phase Studies of Alkane Oxidation by Transition-Metal Oxides. Selective Oxidation by CrO+
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The gas-phase reactions of CrO+ with alkanes have been studied by using ion beam reactive scattering techniques.CrO+ undergoes facile reactions with alkanes larger than methane.CrO+ selectively oxidizes ethane to form ethanol.In addition to the possibility of alcohol formation, reactions with larger alkanes are more complex, yielding products in which dehydrogenation and loss of alkenes and alkanes occur.In reactions with cyclic alkanes, cyclopropane and cyclobutane yield products characterictic of C-C bond cleavage.In contrast, reactions with cyclopentane and cyclohexane mainly involve dehydrogenation and elimination of H2O.A series of hydrogen abstraction reactions are examined to determine the bond dissociation energy D0(CrO+-H) = 89 +/- 5 kcal/mol-1.This bond energy has implications for the reaction mechanisms of CrO+ with alaknes, leading to the suggestion of a multicenter reaction intermediate, in which alkyl C-H bonds add across the Cr+-O bond as an initial step.This is supported by an examination of the reactions of Cr+ with alcohols.
- Kang, H.,Beauchamp, J. L.
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p. 7502 - 7509
(2007/10/02)
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- Solvent Effects on Solvolytic Reactivity. A Diagnostic Test for Neighboring-Group Assistance by ? Conjugation in Solvolysis Reactions
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The solvolysis rates of 13 arenesulfonates have been determined in mixtures of ethanol and water (the E-series solvents) and acetic acid and formic acid (the A-series solvents).The substrates studied include the following: neophyl (1), 2-adamantyl (2), neopentyl (3), and cyclooctyl (4) tosylates; cyclopropylcarbinyl pemsylate (5a) and tosylate (5b); exo-2-norbornyl tosylate (6); cyclobutylcarbinyl (7), cyclobutyl (8), and pinacolyl (9) brosylates; cyclopentyl (10), cyclohexyl (11), and 2-propyl (12) tosylates; and cyclopentylcarbinyl brosylate (13).Correlations of the rate data by eq 1 t(Y) = a + b log kt(neophyl-OTs)> showed that the various substrates responded differently to the examined solvent effects on the solvolytic reactivity.For compounds 2-4, linear correlations were obtained.For compounds 5-9, E-line, A-line dispersions were noted which diverged with increasing ionizing power; for compounds 10-12, parallel E-line, A-line dispersions were obtained; and for compound 13, an E-line, A-line dispersion was observed which converged with increasing ionizing power.Stastistical analyses of the rate data correlations confirmed the significance of the E or A classification of data.The results are interpreted in terms of differences in the involvement of solvent in the transition state for those solvolyses assisted by bridging from those assisted by C-C ? bond hyperconjugation.
- Roberts, Donald D.
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p. 2521 - 2526
(2007/10/02)
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- SMALL RING COMPOUNDS-XLI. CYCLOBUTENE CYCLOADDITIONS; SYNTHESIS AND REACTIVITY IN THE BICYCLOHEXAN-2-ONE SERIES
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Cyclobutene, prepared by base-induced elimination from tosyloxycyclobutane 19 undergoes cycloaddition with ethyl propiolate in the presence of AlCl3 to provide ethyl bicyclohex-2-ene-2-carboxylate 20.This cycloadduct at room temperature and in the presence of AlCl3 undergoes forbidden ring opening into ethyl cyclohexa-1,3-diene-2-carboxylate 21.The cycloaddition of cyclobutene with dichloroketene provides 3,3-dichlorobicyclohexan-2-one 24 and after reductive halogen removal the endo 3-chloro bicyclohexan-2-one 28 (the first study of this strained system).However, further dechlorination of 28 results in rearrangement and fragmentation reactions.
- Fadel, A.,Salauen, J.,Conia, J. M.
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p. 1567 - 1574
(2007/10/02)
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- Photochimie en solution. XXIV. Mecanisme de l'addition des aldehydes aux double liaisons ethyleniques activees par des groupements attracteurs d'electrons
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The mechanism of the photochemical addition of aliphatic aldehydes to electron-deficient olefins has been rationalized.No addition to α,β-unsaturated ketones was observed when the latter were excited.The reaction can be explained by a first self-quenching step of the aliphatic aldehyde involving its lowest triplet state, which is reached with a moderate quantum yield (0.5).The radical R-C.=O produced in the self quenching process adds to the olefin at the more positively-charged carbon atom.The reaction ends by a hydrogen atom exchange between the radical produced by this addition and the radical R-C.HOH.The quantum yield of the product formation is much higher with benzaldehyde owing to the almost unity value of the intersystem crossing, but it competes with the formation of benzile.
- Kawenoki, Isabelle,Maurel, Daniele,Kossanyi, Jean
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p. 385 - 390
(2007/10/02)
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- Acid-Catalyzed Decomposition of Trialkyltriazenes: Protected Alkyldiazonium Ions
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The ecid-catalyzed decomposition of 1,3-di-n-butyl-3-methyltriazene and the synthesis and decomposition of 1,3-bis(cyclprpopylcarbinyl)-3-methyltriazene are reported.A kinetic study of the acid-catalyzed decomposition of 1,3-di-n-butyl-3-methyltriazene indicates that the reaction is subject to general acid catalysis.The rates of reaction have been studied by monitoring the disappearance of a triazene UV absorption band (263 nm).A plot of the buffer concentration vs. kobsd was a straight line, whose slope gave kcat = 1.84 *10-2 min-1M-1.A linear dependence of the log (kobsd) on pH (6.9 - 8.4) was observed, along with a solvent isotope effect (kD/kH) of 2.05.The products of the decomposition of the butyltriazene (n-butyl and sec-butyl alcohols and 1- and 2-butene) were accounted for by the intermediacy of a diazonium ion.The mechanism was corroborated by the product analysis of the decomposition of the (cyclopropylcarbinyl)triazene.The alcoholic products isolated were cyclopropylcarbinyl alcohol (48percent), cyclobutyl alcohol (48percent) and 3-buten-1-ol (4percent).This distribution is conclusive evidence that these trialkyltriazenes decompose in aqueous media to produce alkyldiazonium ions or directly to prduce carbonium ions in cases where the alkyl group is capable of stabilizing a positive charge.
- Sieh, David H.,Michejda, Christopher J.
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p. 442 - 445
(2007/10/02)
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- MIGRATION APTITUDES OF CYCLIC AND POLYCYCLIC BRIDGEHEAD GROUPS IN THE CRIEGEE REARRANGEMENT
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The migration aptitudes of cyclic and polycyclic bridgehead groups in the Criegee Rearrangement support ?-neighbouring group participation by pentacoordinated bonding and vertical charge stabilisation in the migrating group and therefore favour transition state 2b and not 2a.
- Wistuba, Eckehardt,Ruechardt, Christoph
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p. 3389 - 3392
(2007/10/02)
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- Reactions of cyclopropylcarbinol in dilute hydrochloric acid
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The treatment of cyclopropylcarbinol (1-OH) with dilute HCl has been used as a method for the preparation of cyclobutanol (2-OH).While 2-OH is the major product in this reaction, a careful investigation showed the presence of a total of 13 products, namely the alcohols 1-OH, 2-OH, and allylcarbinol (3-OH), cyclopropylcarbinyl, cyclobutyl and allylcarbinyl chlorides (1-Cl, 2-Cl and 3-Cl, respectively), dicyclopropylcarbinyl, cyclobutyl cyclopropylcarbinyl, allycarbinyl cyclopropylcarbinyl, dicyclobutyl and allylcarbinyl cyclobutyl ethers (1-O-1, 2-O-1, 3-O-1, 2-O-2, and 3-O-2, respectively), as well as butyraldehyde and isobutyraldehyde.The alcohols, chlorides, and ethers likely arose from reactions of the bicyclobutonium ion with available nucleophiles in the reaction mixture.The minor amounts of the two aldehydes may be due to a ring opening isomerization of 2-methylcyclopropanol, the latter in turn resulted from a net 1,3-hydride shift in the cyclopropylcarbinyl cation, probably via an edge-protonated cyclopropane-type of species.Treatment of cyclopropylcarbinol (1-OH-α-14C) with dilute HCl gave samples of 1-OH-x-14C, 2-OH-x-14C, and 3-OH-x-14C the degradation of which showed that all three methylene groups in these alcohols have become equivalent, indicating a complete equilibration between isotope-position labeled bicyclobutonium ions.
- Lee, Choi Chuck,Cessna, Allan J.
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p. 1075 - 1079
(2007/10/02)
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- ENZYMATIC "IN VITRO" REDUCTION OF KETONES VII. (1) Reduction rates and stereochemistry of the HLAD catalyzed reduction of 2-alkyl cyclohexanones, dimethyl cyclohexanones, cycloalkanones and bicycloalkanones.
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Values for the rate constants of the catalytic step HLAD-NADH + ketone -> HLAD-NAD1+ + alcohol in the HLAD catalyzed reduction of some 2-alkyl cyclohexanones, geminal dimethyl cyclohexanones, cycloalkanones and bicyclic ketones are presented.Also the thermodynamic parameters of activation are given and they are compared with the activation parameters of the NaBH4 reduction leading to a better understanding of some forces at work in enzymatic catalysis.The results are rationalized in the same way as was previously done for the 3-alkyl and 4-alkyl cyclohexanones.A reaction model is obtained in which steric hindrances and hydrophobic zones are responsible for rate decreasing, respectively increasing interactions between enzyme and substrates.
- Osselaer, T. A. Van,Lemiere, G. L.,Lepoivre, J. A.,Alderweireldt, F. C.
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p. 389 - 398
(2007/10/02)
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- Production of alcohols by reduction of carbonyl compounds with a crystalline aluminosilicate-isopropanol system
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Aliphatic alcohols are producted by reducing the corresponding aldehydes and ketones by contact with a molecular sieve zeolite having adsorbed therein a secondary alcohol which acts as a hydrogen donor agent.
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- Competitive reactions of nucleophiles. Solvolyses of cyclopropylcarbinyl and cyclobutyl methanesulfonates in the presence of NaBH4
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Cyclopropylcarbinyl (I) and cyclobutyl (II) mesylates were solvolysed in aqueous diglyme with or without added NaBH4 under a variety of conditions. The reaction products were isolated and analyzed by VPC. A mixture containing cyclopropylcarbinyl, cyclobutyl and minor quantities of homoallyl products, was obtained in all cases. The proportion of the unsaturated compound was greater in hydrocarbon than in carbinol products, the composition of the mixture depending upon reaction conditions and the starting mesylate. Thus, solvolysis of both I and II yielded cyclopropylcarbinol and cyclobutanol in a ratio of nearly 1:1, while in the hydrocarbon products methylcyclopropane predominated over cyclobutane by a factor of 3 in the reactions of I and by a factor of 2 in the reactions of II. It was shown that a direct displacement reaction of the BH4 ion on the primary mesylate I is not competitive with the solvolysis and cannot therefore be responsible for the above results. It was found that a better yield in hydrocarbons was obtained with I and II than with (1-methylcyclopropyl)carbinyl (III) and 1-methylcyclobutyl (IV) mesylates. The unexpected fact that the BH4- ion competes more efficiently with water for intermediates formed in solvolyses of I and II than for those of III and IV was confirmed by determination of competition factors of N3- ion vs water. In all cases, intermediates formed from I and II showed more discrimination in their reactions with reagents differing in nucleophylicity than did those formed from III and IV. The results indicate that the attack of the nucleophile occurs mostly on the ion pair formed in the rate determining step. The latter reaction is apparently subject to reactivity relationships typical for a direct displacement reaction and not characteristic for free carbonium ions. These facts should be borne in mind when conclusions concerning the structure of carbonium ions are drawn from the composition and structure of solvolysis products. It is concluded that the ion pairs trapped by NaBH4 have different structures, depending upon the starting isomeric mesylate. It is shown that the formation of an equilibrating mixture of classical ions or ion pairs as intermediates in these reactions cannot account for experimental results.
- Majerski,Borcic,Sunko
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p. 301 - 313
(2007/10/05)
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