- Insights into the Molecular Recognition Process in Organocatalytic Chemoselective Monoacylation of 1,5-Pentanediol
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Monoacylation of long-chain linear diols often encounters difficulties associated with unavoidable overacylation affording the diacylate. However, several C1- and C2-symmetrical pyrrolidinopyridine (PPY) catalysts were found to effectively promote the chemoselective monoacylation of 1,5-pentanediol. The effects of catalyst structure on the performance for the monoacylation were investigated. The amide carbonyl group(s) in the pyrrolidine ring in both C1- and C2-symmetrical catalysts was(were) suggested to play the key role in selective monoacylation. On the other hand, the indolyl NH group in the amide side chain of the catalysts was found to be critically important for further increasing the chemoselectivity of monoacylation only when the catalyst has a C2-symmetrical structure. The effects of the catalyst structure on the chemoselective monoacylation were elucidated by DFT calculations, and the origin of the precise molecular recognition for 1,5-pentanediol by the catalysts and transition state (TS) stabilization effects by these functionalities were disclosed.
- Imayoshi, Ayumi,Yamanaka, Masahiro,Sato, Makoto,Yoshida, Keisuke,Furuta, Takumi,Ueda, Yoshihiro,Kawabata, Takeo
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supporting information
p. 1337 - 1344
(2016/04/26)
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- Flavin-functionalized gold nanoparticles as an efficient catalyst for aerobic organic transformations
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Monolayer-protected gold clusters functionalized with synthetic flavins were synthesized and their catalytic activity in aerobic organic transformations investigated. Gold nanoparticles with 5-ethyl-3-(8-thiooctyl)lumiflavinium perchlorate acts as an efficient catalyst for the aerobic oxidation of organic sulfides to the corresponding sulfoxides upon treatment with hydrazine at room temperature and under atmospheric pressure in oxygen. With a catalytic amount of gold nanoparticles with 3-(8-thiooctyl)lumiflavin, diimide reduction of various olefins can be performed with hydrazine at room temperature under atmospheric pressure in air with greater yields of product alkanes than with non-supported 3-methyllumiflavin catalyst under the same conditions. Kinetic studies revealed that the mono-layer-protected gold cluster-catalyzed reactions proceeded faster than those with non-supported catalysts over the full substrate concentration range for the hydrogenation of olefins and at lower substrate concentrations for sulfoxidation. This positive effect was rationalized by assuming a Michaelis-Menten-type mechanism in which the specific inclusion of substrates into the enzyme-like reaction cavities was a key factor in the high efficiency of the supported flavin catalysts.
- Imada, Yasushi,Osaki, Motonari,Noguchi, Mikiko,Maeda, Takatoshi,Fujiki, Misa,Kawamorita, Soichiro,Komiya, Naruyoshi,Naota, Takeshi
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- Compositions, Synthesis, and Methods of Using Cycloalkylmethylamine Derivatives
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The present invention provides novel cycloalkylmethylamine derivatives, and methods of preparing cycloalkylmethylamine derivatives. The present invention also provides methods of using cycloalkylmethylamine derivatives and compositions of cycloalkylmethylamine derivatives. The pharmaceutical compositions of the compounds of the present invention can be advantageously used for treating and/or preventing obesity and obesity related co-morbid indications and depression and depression related co-morbid indications.
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Page/Page column 28
(2012/07/14)
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- Organocatalytic chemoselective monoacylation of 1,n-linear diols
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Matters of length: Exclusive or predominant monoacylation of 1,n-linear diols took place in the presence of 1 when the chain length of linear diols was equal to or shorter than five carbon atoms. The chemoselectivity of acylation between 1,5-pentanediol (n=5) and 1,6-hexanediol (n=6) was 5.2, and that between 1,5-pentanediol and its monoacylate was 113. Copyright
- Yoshida, Keisuke,Furuta, Takumi,Kawabata, Takeo
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supporting information; experimental part
p. 4888 - 4892
(2011/06/22)
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- Aerobic reduction of olefins by in situ generation of diimide with synthetic flavin catalysts
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A versatile reducing agent, diimide, can be generated efficiently by the aerobic oxidation of hydrazine with neutral and cationic synthetic flavin catalysts 1 and 2. This technique provides a convenient and safe method for the aerobic reduction of olefins, which proceeds with 1 equiv of hydrazine under an atmosphere of O2 or air. The synthetic advantage over the conventional gas-based method has been illustrated through high hydrazine efficiency, easy and safe handling, and characteristic chemoselectivity. Vitamin B2 derivative 6 acts as a highly practical, robust catalyst for this purpose because of its high availability and recyclability. Association complexes of 1b with dendritic 2,5-bis(acylamino)pyridine 15 exhibit unprecedented catalytic activities, with the reduction of aromatic and hydroxy olefins proceeding significantly faster when a higher-generation dendrimer is used as a host pair for the association catalysts. Contrasting retardation is observed upon similar treatment of non-aromatic or non-hydroxy olefins with the dendrimer catalysts. Control experiments and kinetic studies revealed that these catalytic reactions include two independent, anaerobic and aerobic, processes for the generation of diimide from hydrazine. Positive and negative dendrimer effects on the catalytic reactions have been ascribed to the specific inclusion of hydrazine and olefinic substrates into the enzyme-like reaction cavities of the association complex catalysts. Copyright
- Imada, Yasushi,Iida, Hiroki,Kitagawa, Takahiro,Naota, Takeshi
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supporting information; experimental part
p. 5908 - 5920
(2011/07/07)
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- Formulating a new basis for the treatment against botulinum neurotoxin intoxication: 3,4-Diaminopyridine prodrug design and characterization
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Botulism is a disease characterized by neuromuscular paralysis and is produced from botulinum neurotoxins (BoNTs) found within the Gram positive bacterium Clostridium botulinum. This bacteria produces the most deadliest toxin known, with lethal doses as low as 1 ng/kg. Due to the relative ease of production and transport, the use of these agents as potential bioterrorist weapons has become of utmost concern. No small molecule therapies against BoNT intoxication have been approved to date. However, 3,4-diaminopyridine (3,4-DAP), a potent reversible inhibitor of voltage-gated potassium channels, is an effective cholinergic agonist used in the treatment of neuromuscular degenerative disorders that require cholinergic enhancement. 3,4-DAP has also been shown to facilitate recovery of neuromuscular action potential post botulinum intoxication by blocking K+ channels. Unfortunately, 3,4-DAP displays toxicity largely due to blood-brain-barrier (BBB) penetration. As a dual-action prodrug approach to cholinergic enhancement we have designed carbamate and amide conjugates of 3,4-DAP. The carbamate prodrug is intended to be a slowly reversible inhibitor of acetylcholinesterase (AChE) along the lines of the stigmines thereby allowing increased persistence of released acetylcholine within the synaptic cleft. As a secondary activity, cleavage of the carbamate prodrug by AChE will afford the localized release of 3,4-DAP, which in turn, will enhance the pre-synaptic release of additional acetylcholine. Being a competitive inhibitor with respect to acetylcholine, the activity of the prodrug will be greatest at the synaptic junctions most depleted of acetylcholine. Here we report upon the synthesis and biochemical characterization of three new classes of prodrugs intended to limit previously reported stability and toxicity issues. Of the prodrugs examined, compound 32, demonstrated the most clinically relevant half-life of 2.76 h, while selectively inhibiting AChE over butyrylcholinesterase-a plasma-based high activity esterase. Future in vivo studies could provide validation of prodrug 32 as a potential treatment against BoNT intoxication as well as other neuromuscular disorders.
- Zakhari, Joseph S.,Kinoyama, Isao,Hixon, Mark S.,Di Mola, Antonia,Globisch, Daniel,Janda, Kim D.
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supporting information; experimental part
p. 6203 - 6209
(2011/12/02)
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- Gold catalysis: In situ EXAFS study of homogeneous oxidative esterification
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Gold complexes were prepared and investigated as catalysts for the oxidative esterification of aldehydes. Stabilisation by pyridine ligands gave good conversions and the in situ extended X-ray absorption fine structure (EXAFS) study of the reactions indicated that the reaction mixtures contained only mononuclear gold species. Thus, this is the first proof for a homogeneous gold-catalysed oxidation reaction ; the presence of nanoparticles could be excluded experimentally.
- Hashmi, A. Stephen K.,Lothschuetz, Christian,Ackermann, Martin,Doepp, Rene,Anantharaman, Sankaran,Marchetti, Benjamin,Bertagnolli, Helmut,Rominger, Frank
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experimental part
p. 8012 - 8019
(2010/09/11)
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- Experimental and DFT studies on competitive heterocyclic rearrangements. 3. A cascade isoxazole-1,2,4-oxadiazole-oxazole rearrangement
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(Figure Presented) The thermal rearrangements of 3-acylamino-5- methylisoxazoles 1 have been investigated under basic and neutral conditions and interpreted with the support of computational data. The density functional theory (DFT) study on the competitive routes available for the base-catalyzed thermal rearrangement of isoxazoles 1 showed that the Boulton-Katritzky (BK) rearrangement, producing the less stable 3-acetonyl-1,2,4-oxadiazoles 5, is a much more favored process than either the migration-nucleophilic attack-cyclization (MNAC) or the ring contraction-ring expansion (RCRE). In turn, an increase in reaction temperature will promote the MNAC of oxadiazoles 5, producing the more stable 2-acylaminooxazoles 8. The thermal rearrangement of 3-acylaminoisoxazoles 1 into oxazoles 8 can therefore be interpreted in terms of a cascade BK-MNAC rearrangement involving 3-acetonyl-1,2,4-oxadiazoles 5 as ancillary intermediates.
- Pace, Andrea,Pierro, Paola,Buscemi, Silvestre,Vivona, Nicolò,Barone, Giampaolo
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experimental part
p. 351 - 358
(2009/04/11)
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- One-pot o-nitrobenzenesulfonylhydrazide (NBSH) formation-diimide alkene reduction protocol
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A one-pot protocol for the formation of 2-nitrobenzenesulfonylhydrazide (NBSH) from commercial reagents and subsequent alkene reduction is presented. The transformation is operationally simple and generally efficient for effecting diimide alkene reductions. A range of 16 substrates have been reduced, highlighting the unique chemoselectivity of diimide as a reduction system.
- Marsh, Barrie J.,Carbery, David R.
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supporting information; experimental part
p. 3186 - 3188
(2009/09/08)
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- Flavin-catalyzed generation of diimide: An environmentally friendly method for the aerobic hydrogenation of olefins
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The first green and practical method for "aerobic hydrogenation" involving the use of hydrazine and an organocatalyst is described. Olefins can be hydrogenated by treatment with hydrazine in the presence of a 5-ethyl-3-methyllumiflavinium perchlorate (FlEt+·ClO4-) catalyst under O2 atmosphere to give the corresponding hydrogenated products in excellent yields along with environmentally benign water and molecular nitrogen as the only waste products. Copyright
- Imada, Yasushi,Iida, Hiroki,Naota, Takeshi
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p. 14544 - 14545
(2007/10/03)
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- Oxidative transformation of 1,3-dioxacycloalkanes induced by chlorine dioxide
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The products and kinetic regularities of the reactions of 1,3-dioxacycloalkanes with chlorine dioxide were studied. The effects of the nature of solvent and the temperature on the reaction rate were considered and the activation parameters were determined.
- Abdrakhmanova,Kabal'nova,Rol'nik,Yagafarova,Shereshovets
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p. 1755 - 1760
(2007/10/03)
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- Oxidation of 1,3-dioxacycloalkanes with complexes of potassium chlorochromate and chlorodiperoxochromate with 15-crown-5, catalyzed with 2,2,5,5-tetramethyl-4-phenyl-3-oxo-3λ5-imidazolin-1-yloxyl
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2,2,5,5-Tetramethyl-4-phenyl-3-oxo-3λ 5-imidazolin-1-yloxyl catalyzes oxidation of 2-isopropyl-1,3-dioxolane, 2-phenyl-1,3-dioxolane, 2-phenyl-4-chloromethyl-1,3-dioxolane, and 2-phenyl-1,3-dioxane with 15-crown-5 complexes of potassium chlorodiperoxochromate (KCrO5Cl·2C 10H20O5) and potassium chlorochromate (KCrO3Cl·2C10H20O5). 2-Isopropyl-1,3-dioxolane is oxidized to the corresponding monoester in quantitative yield, and the 2-phenyl derivatives yield benzaldehyde. The spiro ketal, 2,2-pentamethylene-4-methyl-1,3-dioxane, is decomposed to cyclohexanone.
- Akbalina,Kabal'nova,Zlotskii,Grigor'ev,Kotlyar,Shereshovets,Tolstikov
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p. 447 - 448
(2007/10/03)
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- Transformations of cyclic acetals under the action of some organic and inorganic oxidants
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Liquid-phase oxidation of cyclic acetals and 2,2-disubstituted 1,3-dioxacyclanes with dimethyldioxirane, Caro salt, potassium persulfate, and complex of potassium chlorodiperoxochromate with 15-crown-5 was studied.
- Akbalina,Zlotskii,Kabal'nova,Grigor'ev,Kotlyar,Shereshovets
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p. 1120 - 1122
(2007/10/03)
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- Synthesis of symmetrical and unsymmetrical 1,2-Diketones through cathodic intramolecular coupling of diesters
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Electroreduction of diesters [R1COO(CH2)2OCOR2] with Mg electrode has been found to give the corresponding unsymmetrical 1,2-Diketones (R1COCOR2) with excellent yields.
- Kashimura, Shigenori,Murai, Yoshihiro,Washika, Chise,Yoshihara, Daisuke,Kataoka, Yasuki,Murase, Hiroaki,Shono, Tatsuya
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p. 6717 - 6720
(2007/10/03)
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- Oxidation of Cyclic Acetals as a Preparative Method of Diol Monoester Production
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Glycol monoesters were produced by oxidation of acetals with oxygen, hydroperoxides, hydrogen peroxide, hydrotrioxide and ozon.Addition of salts of metals of variable valency and crown-ether substantially increase the rate of oxidation and hydroxylation.The most efficient oxidizer is ozon.
- Kuramshin, E. M.,Kulak, L. G.,Nazarov, M. N.,Zlotsky, S. S.,Rakhmankulov, D. L.
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p. 591 - 599
(2007/10/02)
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- Alkyl Group Effects on the Rate Constants and Equilibrium Constants for Formation of Cyclic Tetrahedral Intermediates
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2-Hydroxy-2-alkyl-1,3-dioxolanes T are the cyclic intermediates of the degenerate intramolecular ester interchange reactions of ethylene glycol monoalkanoates A, in which alkanoyl groups transfer from one end of ethylene glycol to the other.This study reports equilibrium constants for the cyclization AT to the tetrahedral intermediate stage with 10 alkanoate derivatives.These equiilibrium constants, which when written as / are all large (1 E7-1 E9) in favor of the ring opened form, were obtained as the ratio of rate constants for equilibration occuring with H+ catalysis.Rate constants for the ring opening of T were directly measured through a study of kinetics of the hydrolysis of 2-methoxy-2-alkyl-1,3-dioxolane ortho esters.These hydrolysis proceed via T, and under acid conditions the breakdown of this intermediate is rate-limiting.Rate constants in the ring-closing direction were obtained by preparing HOCH2CD2OOCR and, with the use of 1H NMR spectroscopy, measuring the kinetics of isomerization to an equilibrium mixture with RCOOCH2CD2OH.The reaction under investigation is an intramolecular analogue of H+-catalyzed alkanoate ester hydrolysis, whose rate constant define the steric substituent parameter Es.The ring-closure rate constant for A -> T do show an excellent correlation with Es.However, the rate constants for ring-opening T -> A and the overall equilibrium constant are badly correlated, showing quite different behavior for series with α and β branching in the alkyl group.Thus, for this system the Es parameter does not correlate free energy differencies between the acyl derivative and tetrahedral intermediate.It is only the free energy differences between the acyl form and the transition state leading to the intermediate that fit Es.
- Santry, Linda J.,Azer, Salwa,McClelland, Robert A.
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p. 2909 - 2914
(2007/10/02)
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- Selective Palladium Catalysed Monohydroesterification of Diols
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Olefins react with diols (e. g. ethylene glycol) under oxidative carbonylation and acidic conditions, using palladium and copper(II) chloride as catalysts, to give hydroxy esters in good yields; this mild reaction (room temperature, 1 atm) is a regioselective one.
- Fergusson, Stuart B.,Alper, Howard
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p. 1349 - 1351
(2007/10/02)
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- The mechanism of oxidation of acetals by ozone. I. Stoichiometry, order of reaction, solvent effects, and substituent effects
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A systematic investigation of the reaction between ozone and acetals to form acetal hydrotrioxides A has been undertaken.The stoichiometry of the reaction has been shown to be 1:1 in each reactant and the order of the reaction was also one in each reactant.Substituent effects measured in a variety of systems and under several conditions of temperature and solvent were found to be small (ρ=-1.10 to -1.58).Solvent polarity was also found to have little effect on the rate of the reaction.Mechanistically, these facts are interpreted in terms of a 1,3-dipolar insertion of ozone into the C-H bond of the acetal function.
- Taillefer, Roland J.,Thomas, Shirley E.,Nadeau, Yves,Fliszar, S.,Henry, Herve
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p. 1138 - 1143
(2007/10/02)
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- Electronic Structure and Reactivity of Oxirans and Carboxylic Acids
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The electronic structures of several substituted oxirans and carboxylic acids have been studied by the extended Hueckel method with the aim of explaning their reactivities.
- Kretova, E. N.,Podgornova, V. A.,Stepanov, E. G.
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p. 1300 - 1302
(2007/10/02)
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