- 6,6′-Dihydroxy terpyridine: A proton-responsive bifunctional ligand and its application in catalytic transfer hydrogenation of ketones
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The ligand 6,6′-dihydroxy terpyridine (dhtp) is presented as a bifunctional ligand capable of directing proton transfer events with metal-coordinated substrates. Solid-state analysis of a Ru(ii)-dhtp complex reveals directed hydrogen-bonding interactions of the hydroxyl groups of dhtp with a Ru-bound chloride ligand. The utility of dhtp was demonstrated by chemoselective transfer hydrogenation of ketones.
- Moore, Cameron M.,Szymczak, Nathaniel K.
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- CONJUGATE ADDITIONS OF GRIGNARD REAGENTS TO α,β-UNSATURATED KETONES MEDIATED BY DIAMINE ZINC(II)MONOALKOXIDES
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A method for zinc mediated 1,4-additions of Grignard reagents with alkoxides as non-tranferable ligands is described.Using a chiral TMEDA analogue upto 14 percent enantiomeric excess was achieved.
- Jansen, Johan F. G. A.,Feringa, Ben L.
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- Water soluble polymer-surfactant complexes-stabilized Pd(0) nanocatalysts: Characterization and structure-activity relationships in biphasic hydrogenation of alkenes and α,β-unsaturated ketones
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A suitable approach to stabilize palladium nanoparticles in water as a green reaction medium for catalytic hydrogenation reactions is described. Supramolecular self-assemblies, obtained through the mixture of modified polyethyleneimines as amphiphilic polymers and water-soluble ammonium salts as surfactants, were used as efficient protective agents in the synthesis of Pd(0) nanospecies. The size and dispersion of the nanoparticles prepared with these original self-assemblies were characterized by TEM, SAXS and DLS techniques. The performances of the catalysts according to the polymer-surfactant mixtures were investigated in the hydrogenation of alkenes and α,β-unsaturated ketones in pure biphasic water/substrate medium, under mild conditions (room temperature and 1 bar H2). The nanocatalysts showed efficient catalytic activities and selectivity towards C=C bonds. From investigations, the polymer-surfactant complexes act as cooperative protective agents and a pertinent structure-activity relationship was proposed based on the zeta-potential values and the catalytic activity of the resulting colloids.
- Albuquerque, Brunno L.,Denicourt-Nowicki, Audrey,Mériadec, Cristelle,Domingos, Josiel B.,Roucoux, Alain
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- Simultaneous Preparation of (S)-2-Aminobutane and d -Alanine or d -Homoalanine via Biocatalytic Transamination at High Substrate Concentration
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(S)-2-Aminobutane, d-alanine, and d-homoalanine are important intermediates for the production of various active pharmaceutical ingredients and food additives. The preparation of these small chiral amine or amino acids with high water solubility still demands searching for efficient methods. In this work, we identified an ω-transaminase (ω-TA) from Sinirhodobacter hungdaonensis (ShdTA) that catalyzed the kinetic resolution of racemic 2-aminobutane at a concentration of 800 mM using pyruvate as the amino acceptor, leading to the simultaneous isolation of enantiopure (S)-2-aminobutane and d-alanine in 46% and 90% yield, respectively. In addition, (S)-2-aminobutane (98% ee) and d-homoalanine (99% ee) were isolated in 45% and 93% yield, respectively, in the kinetic resolution of racemic 2-aminobutane at a concentration of 400 mM coupled with deamination of l-threonine by threonine deaminase. We thus developed a biocatalytic process for the practical synthesis of these valuable small chiral amine and d-amino acids.
- Li, Jianjiong,Wang, Yingang,Wu, Qiaqing,Yao, Peiyuan,Yu, Shanshan,Zhu, Dunming
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supporting information
(2022/03/01)
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- Methanol as hydrogen source: Chemoselective transfer hydrogenation of α,β-unsaturated ketones with a rhodacycle
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Methanol is a safe, economic and easy-to-handle hydrogen source. It has rarely been used in transfer hydrogenation reactions, however. We herein report that a cyclometalated rhodium complex, rhodacycle, catalyzes highly chemoselective hydrogenation of α,β-unsaturated ketones with methanol as the hydrogen source. A wide variety of chalcones, styryl methyl ketones and vinyl methyl ketones, including sterically demanding ones, were reduced to the saturated ketones in refluxing methanol in a short reaction time, with no need for inter gas protection, and no reduction of the carbonyl moieties was observed. The catalysis described provides a practically easy and operationally safe method for the reduction of olefinic bonds in α,β-unsaturated ketone compounds.
- Aboo, Ahmed H.,Begum, Robina,Zhao, Liangliang,Farooqi, Zahoor H.,Xiao, Jianliang
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p. 1795 - 1799
(2019/11/11)
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- Efficient Palladium(0) supported on reduced graphene oxide for selective oxidation of olefins using graphene oxide as a ‘solid weak acid’
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Selective oxidation of olefin derivatives to ketones has made innovative development over palladium(0) supported on reduced graphene oxide. Compared to traditional Wacker oxidation, the novel method offers an economical and environment-friendly option by using graphene oxide (GO) as a ‘solid weak acid’ instead of classical homogeneous catalysts like H2SO4 and CF3COOH. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscopy images of Pd0/RGO showed that the nanoscaled Pd particles generated at the flake structure of reduced graphene oxide. Under optimized condition, up to 44 kinds of ketones with different structures can be prepared with excellent yields.
- Gao, Xi,Zhou, Jianhao,Peng, Xinhua
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- Iminyl Radical-Triggered Intermolecular Distal C(sp3)-H Heteroarylation via 1,5-Hydrogen-Atom Transfer (HAT) Cascade
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An efficient iron-catalyzed intermolecular remote C(sp3)-H heteroarylation of alkyl ketones has been developed via an iminyl radical-triggered 1,5-hydrogen-atom transfer (HAT) cascade. This protocol was amenable to a wide variety of alkyl ketones and heteroaryls, thus providing a straightforward method for the late-stage functionalization of alkylketones and heteroaryls.
- Gu, Yu-Rui,Duan, Xin-Hua,Chen, Li,Ma, Zhi-Yong,Gao, Pin,Guo, Li-Na
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supporting information
p. 917 - 920
(2019/02/14)
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- Carbonylation of tertiary carbon radicals: synthesis of lactams
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Herein, we disclose an interesting iron-catalyzed approach for the carbonylation of a tertiary carbon radical. The tertiary carbon radical generated from a 1,5-hydrogen atom transfer can be captured by CO gas smoothly. Various six-membered lactams were constructed chemo-selectively in high yields.
- Yin, Zhiping,Zhang, Zhuan,Zhang, Youcan,Dixneuf, Pierre H.,Wu, Xiao-Feng
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supporting information
p. 4655 - 4658
(2019/05/09)
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- Iminyl Radical-Mediated Controlled Hydroxyalkylation of Remote C(sp3)-H Bond via Tandem 1,5-HAT and Difunctionalization of Aryl Alkenes
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A visible-light mediated γ-hydroxyalkylation of ketones via C(sp3)-H functionalization has been developed under redox neutral conditions. This protocol relies on the iminyl radical-triggered 1,5-HAT followed by oxyalkylation of alkenes, wherein C?C and C?O bonds were constructed in one step. This three-component reaction features mild conditions, wide substrate scope and excellent functional group tolerance, thus providing a facile and highly efficient access to complex valuable ketones. (Figure presented.).
- Ma, Zhi-Yong,Guo, Li-Na,Gu, Yu-Rui,Chen, Li,Duan, Xin-Hua
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supporting information
p. 4341 - 4347
(2018/10/20)
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- Biocatalytic Racemization Employing TeSADH: Substrate Scope and Organic Solvent Compatibility for Dynamic Kinetic Resolution
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Racemization in combination with a kinetic resolution is the base for a dynamic kinetic resolution (DKR). Biocatalytic racemization was successfully performed for a broad scope of sec-alcohols by employing a single alcohol dehydrogenase (ADH) variant from Thermoanaerobacter pseudoethanolicus (formerly T. ethanolicus; TeSADH W110A I86A C295A). The catalyst employed as a lyophilized whole cell preparation or cell free extract, which tolerated various non-water miscible organic solvents under micro-aqueous or two-phase conditions, whereby cyclohexane and n-hexane suited best. Various concepts for combining the enzymatic racemization with an enzymatic kinetic resolution to achieve overall a bis-enzymatic DKR were evaluated. A proof of concept showed a successful DKR with racemization in aqueous phase combined with acylation in the organic phase.
- Pop?oński, Jaros?aw,Reiter, Tamara,Kroutil, Wolfgang
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p. 763 - 768
(2018/02/27)
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- Silylated organometals: A family of recyclable homogeneous catalysts
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A general strategy has been developed to synthesize a family of silylated organometals (M-PPh2-TS and DPEN-Ru-PPh2-Ts, M = Pd2+, Rh+, Pt2+, Ir+, or Ru2+, PPh2-Ts = PPh2CH2CH2Si(OEt)3), DPEN = (1R,2R)-1,2-diphenylethylenediamine). They can act as homogeneous catalysts with high efficiencies in various organic reactions using THF, CH2Cl2 or toluene as the reaction medium. After reaction, they could be thoroughly settled down by adding pentane and then used repeatedly owing to the complete catalyst recovery and good preservation of the catalyst structure. This is particularly important due to the increasing concerns regarding the cost, toxicity and limited availability of these nonrenewable transition metals.
- Huang, Jian-Lin,Wang, Jun-Zhong,Li, He-Xing,Guo, Haibing,O'Doherty, George A.
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supporting information
p. 1473 - 1478
(2015/03/18)
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- A Rapid, efficient method for deprotection of oximes to carbonyl compounds with naclo2 in water
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A rapid, efficient method for deprotection of oximes to carbonyl compounds is demonstrated by using sodium chlorite (NaClO2) in water. The protocol has been found to be applicable to a wide range of aldoximes and ketoximes with good to excellent yields of the corresponding carbonyl compounds.
- Yao, Yuan-Yuan,Zhao, Xian-Liang
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- Site-selective oxidation of unactivated C sp 3-H bonds with hypervalent iodine(III) reagents
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By design: The site-selective oxidation of unactivated secondary C sp 3-H bonds was accomplished with hypervalent iodine(III) reagents and tert-butyl hydroperoxide (see scheme). The preparation and derivatization of the hypervalent iodine(III) reagent are simple, thus allowing the rational design of these reagents to optimize the site selectivity of the oxidation. Copyright
- Moteki, Shin A.,Usui, Asuka,Zhang, Tiexin,Solorio Alvarado, Cesar R.,Maruoka, Keiji
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supporting information
p. 8657 - 8660
(2013/09/12)
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- Cyclohexylamine oxidase as a useful biocatalyst for the kinetic resolution and dereacemization of amines
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The biocatalytic performance of a cloned cyclohexylamine oxidase derived from Brevibacterium oxydans IH-35A towards structurally different amines was investigated. Cycloalkyl primary amines, alkyl aryl amines, and α-carbon-substituted aliphatic amines were identified as suitable substrates for the biocatalyst based on an activity assay. Kinetic resolutions of several amines by either recombinant whole cells or crude enzyme extracts prepared therefrom gave enantiomerically pure (R)-amines besides the corresponding ketones. When cyclohexylamine oxidase in combination with a borane-ammonia complex as reducing agent was applied to the deracemization of several substrates, excellent enantiomeric ratios (>99:1) and good isolated yields (62%-75%) of the corresponding (R)-amines were obtained.
- Leisch, Hannes,Grosse, Stephan,Iwaki, Hiroaki,Hasegawa, Yoshie,Lau, Peter C.K.
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experimental part
p. 39 - 45
(2012/03/07)
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- Continuous flow oxidation of alcohols and aldehydes utilizing bleach and catalytic tetrabutylammonium bromide
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We report a method for the oxidation of a range of alcohols and aldehydes utilizing a simple flow system of alcohols in EtOAc with a stream of 12.5% NaOCl and catalytic Bu4NBr. Secondary alcohols are oxidized to ketones, aldehydes are oxidized directly to methyl esters in the presence of methanol, and benzylic alcohols are oxidized to either benzaldehydes or methyl esters, depending on the conditions used. The reaction conditions are mild and generally provide complete conversion in 5-30 min.
- Leduc, Andrew B.,Jamison, Timothy F.
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supporting information; experimental part
p. 1082 - 1089
(2012/08/27)
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- Polymer-mediated pinacol rearrangements
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Both poly(3,4-ethylenedioxythiophene) and poly(pyrrole) mediate a pinacol rearrangement of 1,2-diols. The yields of ketone or aldehyde products are comparable to those observed for treatment with mineral acids or Lewis acids. The advantage of this protocol is a two-phase reaction medium in hydrocarbon solvents that allows facile recovery of the products by simple filtration of the polymer and removal of solvents. Both the polymer and the hydrocarbon solvent may be recovered and used in subsequent reactions. Georg Thieme Verlag Stuttgart · New York.
- Pavlik, Christopher,Morton, Martha D.,Smith, Michael B.
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experimental part
p. 2191 - 2194
(2011/11/06)
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- Hydrogenation of olefins using water and zinc metal catalyzed by a rhodium complex
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The hydrogenation of olefins using H2O or D2O as a hydrogen source and zinc metal as a reducing agent has been found to be catalyzed by a rhodium complex. α,β-Unsaturated ketones also underwent hydrogenation, affording the corresponding saturated ketones selectively.
- Sato, Takashi,Watanabe, Shoji,Kiuchi, Hiroyoshi,Oi, Shuichi,Inoue, Yoshio
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p. 7703 - 7705
(2007/10/03)
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- Oxone/sodium chloride: A simple and efficient catalytic system for the oxidation of alcohols to symmetric esters and ketones
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An efficient method for the oxidation of alcohols is presented. The use of catalytic amounts of sodium chloride in combination with oxone allows the conversion primary aliphatic alcohols to symmetric esters. Secondary alcohols can be easily oxidized to ketones, and benzylic alcohols are converted to the corresponding aldehydes. The method is cost effective and enviromentally benign. Copyright Taylor & Francis Group, LLC.
- Schulze, Agnes,Pagona, Georgia,Giannis, Athanassios
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p. 1147 - 1156
(2007/10/03)
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- Facile deoxygenation of dicarbonyl compounds using a samarium diiodide-additive system
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The reduction of α- and β-dicarbonyl compounds was investigated with samarium diiodide in the presence of additive. Diketones and ketocarboxylic acids were easily reduced at room temperature to give the mono-alcohols in good to excellent yield, and ketoester afforded the saturated ester as the major product in moderate yield. These reductions containing the reductive deoxygenation can be rapidly performed under the facile and mild conditions by this method.
- Kamochi, Yasuko,Kudo, Tadahiro,Masuda, Toshinobu,Takadate, Akira
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p. 1017 - 1020
(2007/10/03)
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- Processes for the preparation of higher molecular weight ketones
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Processes for producing higher molecular weight ketones are disclosed that include the steps of feeding an aldol catalyst solution, a lower molecular weight aldehyde, and a lower molecular weight ketone, through a reactor provided with a solid hydrogenation catalyst and hydrogen gas; recovering a liquid reactor effluent containing the higher molecular weight ketone as a reaction product; and recycling a portion of the recovered liquid reactor effluent back through the reactor.
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- New ketone homoenolate anion equivalents derived from (alkenyl)pentamethyl phosphoric triamides
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Lithiated ambident anions derived from (1-alkyl-2-propenyl)- or (1-phenyl-2-propenyl)-pentamethyl phosphoric triamides undergo regioselectively γ-reaction with various alkylating reagents and isobutyraldehyde. Further hydrolysis of adducts releases the ketone under acid conditions. Number of synthetic applications clearly show the ketone homoenolate behaviour of these new carbanions.
- Grison, Claude,Thomas, Antoine,Coutrot, Frédéric,Coutrot, Philippe
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p. 2101 - 2123
(2007/10/03)
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- Selective 1,4-reduction of unsaturated carbonyl compounds using Co2(CO)8-H2O
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α,β-Unsaturated ketones and aldehydes were selectively reduced to the corresponding saturated carbonyl compounds by Co2(CO)8-H2O system. The current reducing system also offered a chemoselective reduction of less substituted unsaturated carbonyl groups.
- Lee, Hee-Yoon,An, Mihyun
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p. 2775 - 2778
(2007/10/03)
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- Iridium-catalyzed transfer hydrogenation of α,β-unsaturated and saturated carbonyl compounds with 2-propanol
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The selective transfer hydrogenation of α,β-unsaturated carbonyl compounds to saturated ones was achieved by the use of 2-propanol as a hydrogen donor under the influence of catalytic amounts of [Ir(cod)Cl]2, 1,3-bis(disphenylphosphino)propane (dppp), and Cs2CO3. Thus, a variety of conjugated enones were allowed to react with 2-propanol in the presence of the [Ir(cod)Cl]2/dppp/Cs2CO3 system to give the corresponding saturated carbonyl compounds in good to excellent yields without formation of allylic alcohols. Both dppp and Cs2CO3 were essential components to achieve the reduction satisfactorily. Additionally, the reduction of carbonyl compounds to alcohols was also promoted by the same catalytic system. When the reaction of a 1:1 mixture of a conjugated ketone and a saturated ketone with 2-propanol was carried out in the presence of [Ir(cod)Cl]2 combined with dppp and Cs2CO3, the reduction of the α,β-unsaturated ketone was found to take place in preference to that of the saturated ketone.
- Sakaguchi,Yamaga,Ishii
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p. 4710 - 4712
(2007/10/03)
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- Dynamic kinetic resolution of allylic alcohols mediated by ruthenium- and lipase-based catalysts.
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An enzyme-metal combo reaction has been developed for the dynamic kinetic resolution of allylic alcohols in which racemic substrates are transformed by a lipase and a ruthenium complex in the presence of an acyl donor to allylic acetates of high optical purity in over 80% yield.
- Lee,Huh,Kim,Jung,Koh,Park
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p. 2377 - 2379
(2007/10/03)
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- Enthalpies of hydrogenation and formation of enones. Resonance energies of 2-cyclopentenone and 2-cyclohexenone
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The enthalpies of hydrogenation of 2-cyclopentenone, 2-cyclohexenone, 2-methyl-3-isobutoxycyclohex-2-enone, and 5-methylhex-5-en-2-one have been measured and found to be -(97.1 ± 2.7) kJ·mol-1, -(109.2 ± 2.9) kJ·mol-1, -(106.1 ± 3.0) kJ·mol-1, and -(113.2 ± 2.7) kJ·mol-1, respectively. In combination with the enthalpies of formation of the corresponding alkanones, we obtained the enthalpies of formation ΔfHom (cyclopentenone) = -(100.3 ± 3.0) kJ·mol-1 and ΔfHom (cyclohexenone) = -(121.9 ± 3.0) kJ·mol-1. By using isodesmic reactions, the resonance energy of cyclic enones is estimated to be (13 ± 4) kJ·mol-1.
- Rogers, Donald W.,Zhao, Yeping,Traetteberg, Marit,Hulce, Martin,Liebman, Joel
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p. 1393 - 1400
(2007/10/03)
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- Effects of Substituents on the Strength of C-C Bonds, 11. - Thermolysis of Tetraalkylpinacol Dimethyl Ethers
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The products and the kinetics of the thermolysis reaction of the pinacol dimethyl ethers 1a-1f have been studied.A linear correlation between ΔG(excit.) (300 deg C) of thermolysis and the strain enthalpies HS of 1, or its release DS during dissociation into radicals 2, is observed.From this correlation a stabilization enthalpy HR = 2.1 +/- 0.5 kcal/mol is deduced for α-methoxyalkyl radicals 2 as compared to tert-alkyl radicals.Key Words: 1,2-Dialkoxyethanes, tetraalkyl- / Strain and structure / Thermolysis, kinetics of / Radicals, stability of
- Birkhofer, Hermann,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 1023 - 1030
(2007/10/02)
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- Trialkylborane as an Initiator and Terminator of Free Radical Reactions. Facile Routes to Boron Enolates via α-Carbonyl Radicals and Aldol Reaction of Boron Enolates
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A variety of trialkylborane-induced reactions were examined for the preparation of the α-carbonyl radicals: (1) addition of alkyl radical to methyl vinyl ketone, (2) reduction of α-halo ketone, and (3) intramolecular radical addition to α,β-unsaturated carbonyl moiety.Trialkylborane reacted with α-carbonyl radicals to give boron enolates.The resulting boron enolates were efficiently trapped by carbonyl compounds to give β-hydroxy ketones in good yields.
- Nozaki, Kyoko,Oshima, Koichiro,Utimoto, Kiitiro
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p. 403 - 409
(2007/10/02)
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- EFFECT OF STERIC FACTORS ON THE EQUILIBRIUM IN THE FORMATION OF TERT-BUTYLPEROXY KETALS FROM ALIPHATIC KETONES
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The equilibrium in the formation of tert-butylperoxy ketals from aliphatic ketones and tert-butyl hydroperoxide is determined by the steric factors of the substituents at the carbonyl group of the ketones.The dependence of the equilibrium constant on the steric parameters of the substituents is described by the Taft equation log K/KO = δΣEs0 with δ = 1.37 (r = 0.970).
- Antonovskii, V. L.,Fedorova, E. V.,Shtivel', N. E.,Emelin, Yu. D.
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p. 704 - 706
(2007/10/02)
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- -Sigmatropic rearrangement of allylic sulfinate esters: A novel synthesis of agelasidine-A analogues
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Sulfonylguanidino analogues 3,7-dimethyl-1,6-octadiene-3(β-guanidino)ethylsulfone sulfonate (4), 3,6-dimethyl-1-heptene-3(β-guanidino)ethylsulfone sulfonate (5), 3-methyl-5-phenyl--1-pentene-3(β-guanidino)ethylsulfone sulfonate (6) of agelasidine (1) have been synthesized in high yields using -sigmatropic rearrangement of allylic sulfinate esters as a key reaction.
- Suryawanshi, S N,Rani, A,Bhakuni, D S
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p. 1089 - 1094
(2007/10/02)
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- Zinc(II) Catalysed Conjugate Addition of Grignard Reagents to α,β-Unsaturated Ketones
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Zinc(II)-diamine complexes are efficient catalysts for the conjugate additions of Grignard reagents to various α,β-unsaturated ketones.
- Jansen, Johan F. G. A.,Feringa, Ben L.
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p. 741 - 742
(2007/10/02)
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- FACILE ROUTES TO BORON ENOLATES. Et3B-MEDIATED REFORMATSKY TYPE REACTION AND THREE COMPONENTS COUPLING REACTION OF ALKYL IODIDES, METHYL VINYL KETONE, AND CARBONYL COMPOUNDS
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Reaction of α-bromoketones with Ph3SnH in the presence of Et3B provides boron enolates which react with carbonyl compounds to give β-hydroxyketones in good yields.Et3B-induced Reformatsky type reaction of α-iodoketones with an aldehyde or ketone proceeds without Ph3SnH.
- Nozaki, Kyoko,Oshima, Koichiro,Utimoto, Kiitiro
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p. 1041 - 1044
(2007/10/02)
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- Oxidation of Secondary Alcohols with t-Butyl Hypochlorite in the Presence of Pyridine
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When treated with t-butyl hypochlorite and pyridine in methylene dichloride, secondary alcohols give the corresponding ketones in very high yield.The relative reactivities of a number of p-substituted 1-phenylethanols containing electron-donating and -withdrawing substituents were investigated.Oxidation of cis- and trans-4-t-butylcyclohexanol, as well as some other cycloalkanols, proceeds with the same relative rate.On the basis of this and other data a cyclic transition state and loss of α-hydrogen of the starting alcohols as hydride ion are proposed as characteristics of the reaction mechanism.
- Milovanovic, Jovan N.,Vasojevic, Miorad,Gojkovic, Svetislav
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p. 533 - 536
(2007/10/02)
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- Chemo-Selectivity of Group-VIII Metal Catalysts in Hydrogenation of Nonconjugated Enones
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The chemo-selectivity of group-VIII metal catalysts has been examined in the hydrogenation of nonconjugated enones at ambient temperature under an atmospheric pressure of hydrogen.A cobalt catalyst gave high yields of unsaturated alcohols from trialkylated olefinic ketones.Osmium showed the highest selectivity among platinum metal catalysts for the reduction of the carbonyl bond in the hydrogenation of trialkylated olefinic ketones.The hydrogenation of mono- and dialkylated olefinic ketone ordinarily proceeded with a preferential saturation of the olefinic function, regardless of the catalysts.The hydrogenation of 4-methylene- and 4-ethylidenecyclohexanone was accompanied by the formation of diethyl acetals over ruthenium, rhodium, and palladium black catalysts in an ethanol solvent.The acetals were not detected in the hydrogenation of the other enones and over the other catalysts.In addition, the chemoselectivity on the hydrogenation of acyclic enones was examined over nickel and cobalt catalysts treated with small amounts of alkali and carbon monoxide.The amount of unsaturated alcohols increased when the catalyst was treated with alkali in the case of di- and trialkylated olefinic ketones, whereas the characteristics of cobalt, which selectively reduces the ketonic function in trialkylated olefinic ketoones, were completely missing when cobalt was treated with carbon monoxide.
- Ishiyama, Jun-ichi,Maeda, Satoshi,Takahashi, Kazuhiro,Senda, Yasuhisa,Imaizumi, Shin
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p. 1721 - 1726
(2007/10/02)
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- Microbial Oxidation of Sterol Side-Chains
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Several sterol metabolising microorganisms, Pseudomonas convexa, P. stutzeri, Micrococcus sp., Cephalosporium longisporum and Moraxella sp. were isolated from soil on 2-cyclopentyl-6-methyl heptane and cholestane as carbon sources.All these organisms were shown to have the capacity of oxidizing the eight carbon side chain of cholesterol.Excepting P. convexa, the organisms needed a chelating agent for prevention of steroid ring degradation.The Moraxella sp. proved to be the most versatile as it degraded cholesterol derivatives such as 3β-methoxy cholest-5-ene, 3β-chloro cholest-5-ene, 3,5-cyclocholestan-6-one and potassium cholesteryl sulphate to the corresponding 17-keto steroids in 10-50percent yield in shake flasks.It also gave high yields of estrone from both 19-hydroxy-3β-acetoxy cholest-5-ene and 19-hydroxy-3β-acetoxy sitost-5-ene.Two new enzymes one carrying out the oxidative O-demethylation of 6β-methoxy 3,5-cyclocholestane and the other, the isomerisation of i-steroids to normal 3β-hydroxy-Δ5 steroids were discovered.Immobilized Moraxella cells in agar carried out the side chain degradation of cholesteryl sulphate to yield 3β-hydroxy androst-5-en-17-one sulphate and the 19-hydroxy-3β-acetoxy derivatives of both cholesterol and sitosterol to estrone in high yields.The half life of entrapped cells was estimated to be 28 days.
- Bhattacharyya, P. K.,Rao, M. Krishna,Natarajan, Rama Devi,Ramgopal, Malathi,Madyastha, Prema,Madyastha, K. M.
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- Steric, Polar, and Resonace Effects in Reactivity and Regioselectivity of Aryl Radical Addition to α,β-Unsaturated Carbonyl Compounds
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Free-radical decomposition of diazonium salts by titanous salts in the presence of olefins conjugated with carbonyl groups leads to reductive arylation or arylation and diazo coupling of the radical adduct, depending on the orientation of the aryl radical addition (β or α).The absolute rate constants of the addition (107 - 108 M-1s-1 at 5 deg C) were determined by comparison with the rate of the iodine abstraction by aryl radicals from isopropyl iodide.The obtained data of the addition rates to the β position correlate well with the Es steric parameters.The influence of the resonace stabilization of the radical adduct on the reactivity can be significant, but the regioselectivity of the addition is mainly determined by steric effects.The different fate of the α- and β-radical adducts are discussed on the basis of their different polar character.
- Citterio, Attilio,Minisci, Francesco,Vismara, Elena
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- Synthetic applications of α-hydroxydiazenes. III. Uncatalyzed and phenol catalyzed hydroalkylation of alkenes and of azobenzene with alkylazodiphenylmethanols
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Alkylazodiphenylmethanols (C6H5)2C(OH)N=NR, (R = CH(CH3)2, CH2CH3, CH3), when decomposed in the presence of olefinic substrates or in the presence of azobenzene, hydroalkylate those substrates.Addition of R and H across the double bond of an unsymmetric alkene occurs with the regiochemistry expected for a radical mechanism, in which the grooup R adds first.Radical intermediates from decomposition of alkylazodiphenylmethanols have been demonstrated earlier with spin trapping experiments.The fact that addition of phenol can enhance the yield of hydroalkylation product suggests that the process is a radical chain reaction, with chain carrying steps consisting of the reactions: (i) R. + CH2=CHY -> RCH2C.HY (ii) RCH2C.HY + (C6H5)2C(OH)N2R -> RCH2CH2Y + (C6H5)2CO + N2 + R..One deuterioalkylation and some yield-optimizing experiments are also reported.
- Yeung, Dominic W. K.,Warkentin, John
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p. 2386 - 2394
(2007/10/02)
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