- Azolium/Hydroquinone Organo-Radical Co-Catalysis: Aerobic C?C-Bond Cleavage in Ketones
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Organo-radical catalysts have recently attracted great interest, and the development of this field can be expected to broaden the applications of organocatalysis. Herein, the first example of a radical-generating system is reported that does not require any photoirradiation, radical initiators, or preactivated substrates. The oxidative C?C-bond cleavage of 2-substituted cyclohexanones was achieved using an azolium salt and a hydroquinone as co-catalysts. A catalytic mechanism was proposed based on the results of diffusion-ordered spectroscopy and cyclic voltammetry measurements, as well as computational studies.
- Nakatsuji, Yuya,Kobayashi, Yusuke,Masuda, Sakyo,Takemoto, Yoshiji
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supporting information
p. 2633 - 2637
(2021/02/03)
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- Visible Light-Driven, Copper-Catalyzed Aerobic Oxidative Cleavage of Cycloalkanones
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A visible light-driven, copper-catalyzed aerobic oxidative cleavage of cycloalkanones has been presented. A variety of cycloalkanones with varying ring sizes and various α-substituents reacted well to give the distal keto acids or dicarboxylic acids with moderate to good yields.
- Xin, Hong,Duan, Xin-Hua,Yang, Mingyu,Zhang, Yiwen,Guo, Li-Na
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supporting information
p. 8263 - 8273
(2021/06/30)
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- Selective C-C Bond Cleavage of Cycloalkanones by NaNO2/HCl
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A novel selective fragmentation of cycloalkanones by NaNO2/HCl has been established. The C-C bond cleavage reaction proceeds smoothly under mild conditions, selectively affording versatile keto acids or oxime acids. The methodology can streamline the synthesis of valuable chiral molecules and isocoumarins from readily available feedstocks.
- He, Tianyu,Chen, Dengfeng,Qian, Shencheng,Zheng, Yu,Huang, Shenlin
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supporting information
p. 6525 - 6529
(2021/09/02)
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- Palladium-Aminopyridine Catalyzed C?H Oxygenation: Probing the Nature of Metal Based Oxidant
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A mechanistic study of direct selective oxidation of benzylic C(sp3)?H groups with peracetic acid, catalyzed by palladium complexes with tripodal amino-tris(pyriylmethyl) ligands, is presented. The oxidation of arylalkanes having secondary and tertiary benzylic C?H groups, predominantly yields, depending on the substrate and conditions, either the corresponding ketones or alcohols. One of the three 2-pyriylmethyl moieties, which is pending in the starting catalyst, apparently, facilitates the active species formation and takes part in stabilization of the high-valent Pd center in the active species, occupying the axial coordination site of palladium. The catalytic, as well as isotopic labeling experiments, in combination with ESI-MS data and DFT calculations, point out palladium oxyl species as possible catalytically active sites, operating essentially via C?H abstraction/oxygen rebound pathway. For the ketones formation, O?H abstraction/в-scission mechanism has been proposed.
- Lubov, Dmitry P.,Bryliakova, Anna A.,Samsonenko, Denis G.,Sheven, Dmitriy G.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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p. 5109 - 5120
(2021/11/10)
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- Metal-Free, Visible-Light-Induced Selective C?C Bond Cleavage of Cycloalkanones with Molecular Oxygen
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A metal-free, visible-light-induced oxidative C?C bond cleavage of cycloketones with molecular oxygen is described. Cooperative Br?nsted-acid catalysis and photocatalysis enabled selective C?C bond cleavage of cycloketones to generate an array of γ-, δ- and ?-keto esters under very mild conditions. Mechanistic studies indicate that singlet molecular oxygen (1O2) is responsible for this transformation.
- Xin, Hong,Duan, Xin-Hua,Liu, Le,Guo, Li-Na
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supporting information
p. 11690 - 11694
(2020/08/21)
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- Aryl Boronic Acid Catalysed Dehydrative Substitution of Benzylic Alcohols for C?O Bond Formation
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A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C?O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid.
- Estopi?á-Durán, Susana,Donnelly, Liam J.,Mclean, Euan B.,Hockin, Bryony M.,Slawin, Alexandra M. Z.,Taylor, James E.
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supporting information
p. 3950 - 3956
(2019/02/16)
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- Synergistic palladium/enamine catalysis for asymmetric hydrocarbon functionalization of unactivated alkenes with ketones
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Synergistic palladium and enamine catalysis was explored to promote ketone addition to unactivated olefins. A secondary amine-based organocatalyst was identified as the optimal co-catalyst for the directed Pd-catalyzed alkene activation. Furthermore, asymmetric hydrocarbon functionalization of unactivated alkenes was also achieved with good to excellent yield (up to 96% yields) and stereoselectivity (up to 96% ee). This strategy presented an efficient approach to prepare α-branched ketone derivatives under mild conditions.
- Wei, Chiyu,Ye, Xiaohan,Xing, Qingyu,Hu, Yong,Xie, Yan,Shi, Xiaodong
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p. 6607 - 6611
(2019/07/16)
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- Direct Asymmetric α-Hydroxylation of Cyclic α-Branched Ketones through Enol Catalysis
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Enantiopure α-hydroxy carbonyl compounds are common scaffolds in natural products and pharmaceuticals. Although indirect approaches towards their synthesis are known, direct asymmetric methodologies are scarce. Herein, we report the first direct asymmetric α-hydroxylation of α-branched ketones through enol catalysis, enabling a facile access to valuable α-keto tertiary alcohols. The transformation, characterized by the use of nitrosobenzene as the oxidant and a new chiral phosphoric acid as the catalyst, delivers a good scope and excellent enantioselectivities.
- Shevchenko, Grigory A.,Pupo, Gabriele,List, Benjamin
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- Oxidative cleavage of olefins by in situ-generated catalytic 3,4,5,6-tetramethyl-2-iodoxybenzoic acid/oxone
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Oxidative cleavage of a variety of olefins to the corresponding ketones/carboxylic acids is shown to occur in a facile manner with 3,4,5,6-tetramethyl-2-iodobenzoic acid (TetMe-IA)/oxone. The simple methodology involves mere stirring of the olefin and catalytic amount (10 mol %) of TetMe-IA and oxone in acetonitrile-water mixture (1:1, v/v) at rt. The reaction mechanism involves initial dihydroxylation of the olefin with oxone, oxidative cleavage by the in situ-generated 3,4,5,6-tetramethyl-2-iodoxybenzoic acid (TetMe-IBX), and oxidation of the aldehyde functionality to the corresponding acid with oxone. Differences in the reactivities of electron-rich and electron-poor double bonds have been exploited to demonstrate chemoselective oxidative cleavage in substrates containing two double bonds.
- Moorthy, Jarugu Narasimha,Parida, Keshaba Nanda
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p. 11431 - 11439
(2015/02/05)
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- Oxidation cascade with oxone: Cleavage of olefins to carboxylic acids
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A variety of olefins is shown to be cleaved oxidatively to the corresponding acids with oxone as the reagent. The simple methodology that works well for a range of alkenes, i.e., styrenes, nitrostyrenes, stilbenes, cinnamic acids, chalcones, etc., involves heating of the reactant with oxone in acetonitrile-water mixture (1:1, v/v) at reflux. The oxidation cascade involves initial dihydroxylation followed by oxidative cleavage and oxidation of the resultant aldehydes to acids.
- Parida, Keshaba Nanda,Moorthy, Jarugu Narasimha
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p. 2280 - 2285
(2014/03/21)
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- Natural phosphate modified by vanadium: A new catalyst for oxidation of cycloalkanones and α-ketols with oxygen molecular
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In this work, we have studied the catalytic oxidative cleavage of C-C bonds of cycloalkanones and α-ketols, in the presence of natural phosphate (NP) type fluorapatite, Ca10(PO4)6F2, and dioxygen. The aim was to find a heterogeneous system clean and efficient alternative to the industrial oxidation of cyclohexanone to adipic acid with nitric acid. The modification of the NP by vanadium leads to the preparation of a new catalyst V/PN. The latter was characterized by: XRD, FTIR, SEM and BET. It appears that vanadium is well dispersed on the surface of the NP. Using 2-methylcyclohexanone as model substrate, we optimized the conditions of reaction in order to make the system 'V/PN/O2' more performance. The comparative study between the two catalytic systems 'PN/O2' and 'V/PN/O2' shows that the latter is more active. Finally, the system 'V/PN/O2' has been recycled but low leaching of vanadium was observed in the first use of the catalyst.
- Dakkach, Mohamed,Atlamsani, Ahmed,Sebti, Sa?d
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scheme or table
p. 482 - 492
(2012/07/31)
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- K-10 montmorillonite: An efficient and reusable catalyst for the aerobic CC bond cleavage of α-substituted ketones
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A commercially available acid-activated montmorillonite clay catalyst, K10 montmorillonite, was tested for the catalytic oxidation of cyclic ketones in the presence of molecular oxygen under mild conditions (343 K and atmospheric pressure). K10 montmorillonite catalyzed the oxidative cleavage of CC bonds in 2-methylcyclohexanone, 2-phenylcyclohexanone, 2-hydroxylcyclohexanone and 1,2-cyclohexanedione with good activity and excellent selectivity toward the formation of the corresponding ketoacids and diacids. The effects of acidity, amount of catalyst, temperature and solvent on the catalytic activity were investigated. Furthermore, this catalyst was reusable without any appreciable loss in activity and selectivity.
- El Younssi, Iman,Rhadfi, Tarik,Atlamsani, Ahmed,Draoui, Khalid,Quisefit, Jean-Paul,Herbst, Frederic
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p. 437 - 445,9
(2020/07/31)
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- Polymer supported vanadium complexes as catalysts for the oxidation of alkenes in water
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Polymer supported vanadium complexes (denoted as c-PMA n -V) were prepared by the complexation of vanadium ions onto a cross linked polyacrylate. c PMA n -V can catalyze the oxidative cleavage of olefins with a large excess of t-butyl hydroperoxide (TBHP) or bishydroxylation of olefins with 4 eq. of TBHP. Graphical Abstract: [Figure not available: see fulltext.].
- Hsiao, Ming-Chieh,Liu, Shiuh-Tzung
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experimental part
p. 61 - 66
(2010/12/25)
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- Oxidative cleavage of alkenes using an in situ generated iodonium ion with oxone as a terminal oxidant
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A facile and operationally convenient catalytic procedure for oxidative cleavage of alkenes is described. In situ formed [hydroxy(4-carboxyphenyl) iodonium]ion, 2, from the oxidation of 4-iodobenzoic acid, 1, has been shown to facilitate the cleavage of a variety of alkenes in presence of Oxone as a co-oxidant. Optimization of the reaction conditions using 1-phenyl-1- cyclohexene, 3, and the competitive oxidative cleavage of different substrates using the optimized conditions has uncovered important mechanistic details of the reaction.
- Thottumkara, Prem P.,Vinod, Thottumkara K.
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supporting information; experimental part
p. 5640 - 5643
(2011/02/27)
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- Oxidative cleavage of cycloalkanones with dioxygen catalyzed by supported catalysts or homogeneous systems: Evidence for novel active ruthenium (II) and/or (III) species
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α-Substituted cycloalkanones are oxidized to oxo-acids by low-nuclearity complexes (Cu2+ or [VO2] +/[VO]2+ - exchanged Nafion beads), or homogeneous systems with ruthenium acetate complexes and [Ru(H 2O)6] (tosylate)2 in dioxygen (0.1 MPa) at 55-60 °C. The catalytic procedures compare well with previously described systems involving homogeneous catalysis with copper (II) or polyoxometalates such as "H8[PMo7V5O40] ·aq". The results complement the widely used oxidative methods for ketone cleavage in cases when protons and transition metal salts are involved. A tentative dioxygenase mechanism, involving peroxygen species, is proposed for these reactions.
- Vennat, Maxence,Brégeault, Jean-Marie
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scheme or table
p. 9 - 15
(2011/01/03)
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- Benzylic carbon oxidation by an in situ formed o-iodoxybenzoic acid (IBX) derivative
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Benzylic C-H bonds are selectively oxidized to the corresponding carbonyl functionalities using catalytic quantities of 2-iodobenzoic acid (2IBAcid) and Oxone. The reported procedure tolerates different functional groups and operates under mild conditions. A radical mechanism is proposed for the transformation and evidence supporting the proposed mechanism is also presented. Georg Thieme Verlag Stuttgart.
- Ojha, Lawanya R.,Kudugunti, Shashi,Maddukuri, Padma P.,Kommareddy, Amitha,Gunna, Meena R.,Dokuparthi, Praveen,Gottam, Hima B.,Botha, Kiran K.,Parapati, Divya R.,Vinod, Thottumkara K.
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scheme or table
p. 117 - 121
(2009/05/30)
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- Cobalt-Catalyzed Oxidations in Volumetrically Expanded Liquids by Compressed Gases
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Oxidations of hydrocarbons, cycloalkanes and alkenes, arylalkanes, and a variety of other organic substrates are accomplished by cobalt-N-hydroxysuccinimide co-catalyzed reactions with dioxygen under unusually mild, near ambient conditions of temperature and pressure. The improved safety of the oxidation method and the high yields of product obtained make use of a unique combination of cobalt (II) complexes with N-hydroxysuccinimide. These autoxidation reactions do not have prolonged initiation times. Many of these reactions can be safely performed under normal chemical laboratory conditions and do not require specialized equipment or reagents.
- -
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Page/Page column 7
(2008/12/06)
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- Structurally simple trichostatin A-like straight chain hydroxamates as potent histone deacetylase inhibitors
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A series of new, structurally simple trichostatin A (TSA)-like straight chain hydroxamates were prepared and evaluated for their ability to inhibit partially purified human histone deacetylase 1 (HDAC-1). Some of these compounds such as 8m, 8n, 12, and 15
- Woo, Soon Hyung,Frechette, Sylvie,Khalil, Elie Abou,Bouchain, Giliane,Vaisburg, Arkadii,Bernstein, Naomy,Moradei, Oscar,Leit, Silvana,Allan, Martin,Fournel, Marielle,Trachy-Bourget, Marie-Claude,Li, Zuomei,Besterman, Jeffrey M.,Delorme, Daniel
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p. 2877 - 2885
(2007/10/03)
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- Ruthenium-catalyzed oxidative cleavage of olefins to aldehydes
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Three oxidation protocols have been developed to cleave olefins to carbonyl compounds with ruthenium trichloride as catalyst (3.5 mol %). These methods convert olefins that are not fully substituted to aldehydes rather than carboxylic acids. While aryl olefins were cleaved to aromatic aldehydes in excellent yields by using the system of RuCl3-Oxone-NaHCO3 in CH3CN-H2O (1.5:1), aliphatic olefins were converted into alkyl aldehydes with RuCl3-NaIO4 in 1,2-dichloroethane-H2O (1:1) in good to excellent yields. It is noteworthy that terminal aliphatic olefins were cleaved to the corresponding aldehydes in excellent yields by using RuCl3-NaIO4 in CH3CN-H2O (6:1).
- Yang,Zhang
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p. 4814 - 4818
(2007/10/03)
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- Oxidation of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate in alcohols and acetic acid
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The reaction of 2-substituted cycloalkanones with cerium(IV) sulfate tetrahydrate (CS) in alcohols and acetic acid gave the corresponding alkyl esters of oxo acids (80-96%) and oxo acids (78-96%), respectively, by oxidative cleavage of the C(R).C=O bond. In the case of 2-iodocycloalkanones in methanol, the dimethyl ester was obtained in good yield. A treatment of 5α-cholestan-3-one with CS in methanol produced 2-acetal 3-ester of 2,3-seco derivative in good yield. The effects of cerium(IV) and copper(II) salts are also discussed.
- He, Liangyou,Horiuchi, C. Akira
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p. 2515 - 2521
(2007/10/03)
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- Photochemistry of nonconjugated diketones: internal self-quenching and energy transfer
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The triplet state behavior of nine α,ο-dibenzoylalkanes indicates the occurrence of a rapid quenching interaction between the two carbonyl groups.This quenching is fastest (k=3E7 s-1) in dibenzoylbutane, is slightly slower (ca.E7 s-1) in dibenzoylethane, dibenzoylpentane, and 2,2-dibenzoylpropane, but is absent in 1,3-dibenzoylpropane.It also occurs in several "mixed" 1,4-diaroylbutanes incorporating p-ethylbenzoyl or p-methoxybenzoyl chromophores.This internal self-quenching is interpreted as the intramolecular counterpart of the well-know bimolecular self-quenching of aryl ketones, although no exact mechanism can be proposed.Such internal quenching does not occur as rapidly, if at all, in three "turned around" diketones: δ-(p-acetylphenyl)valerophenone, δ-(p-acetylphenoxy)valerophenone, and γ-(p-acetylphenoxy)butyrophenone.This fact, together with the varying rates of internal self-quenching in the dibenzoylalkanes, indicates the necessity for a very specific and close orientation of the two carbonyl groups for self-quenching.In the mixed diketones containing a p-alkylbenzoyl group, triplet excitation appears to be fully equilibrated between the two chromophores.However, in those containing a p-methoxybenzoyl group, excitation does not fully equilibrate before triplet decay, as evidenced by different quenching efficiencies for products from the two carbonyls.Analysis indicates intramolecular energy transfer rate constants -1.These are sufficiently lower than in other bichromophoric systems to suggest relatively slow energy hopping in the polymers of phenyl vinyl ketone.Key words: nonconjugated diketones, dibenzoylalkanes, sefl-quenching, energy transfer, triplet ketones.
- Wagner, Peter J.,Frerking, Harlan W. Jr.
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p. 2047 - 2061
(2007/10/03)
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- The mechanistic study and synthetic applications of the base treatment in the ozonolytic reactions
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The E1cb mechanism is the overwhelming process in the reaction of bases and ozonides. As a quenching agent in the ozonolysis of a variety of alkenes, the reactions involving triethylamine often gave better yields and proceeded faster than those involving methyl sulfide. On the other hand, in the presence of 4 A molecular sieves, the secondary amines reacted with mono- and 1,1-di-substituted ozonides to afford the reductive amination products in high yields. The formation of ammonium formate in the reaction mixture also supported the E1cb mechanism in the reaction of ozonide and amine.
- Hon, Yung-Son,Lin, Sheng-Wun,Lu, Ling,Chen, Yao-Jung
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p. 5019 - 5034
(2007/10/02)
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- Synthesis of 5- and 6-oxoalkanoic acids by copper(II) catalyzed oxidative cleavage of cycloalkanones with dioxygen
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α-Substituted cycloalkanones are oxidized to oxo acids by the copper(II)/dioxygen/acetic acid/water system. This catalytic procedure compares well with the previously described systems involving vanadium precursors.
- Atlamsani,Bregeault
-
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- The Oxidation of Ketones with a Heteropolyacid, H5 and Dioxygen
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Substituted cycloalkanones, 1-phenylalkanones, and open-chain ketones are oxidatively cleaved by the title compound under very mild conditions.
- Ali, Bassam El,Bregeault, Jean-Marie,Mercier, Jacqueline,Martin, Jacques,Martin, Claudine,Convert, Odile
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p. 825 - 826
(2007/10/02)
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- REACTION OF α,β-UNSATURATED ALDEHYDES WITH HYDROGEN PEROXIDE CATALYSED BY BENZENESELENINIC ACIDS AND THEIR PRECURSORS
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Oxidation of α,β-unsaturated aldehydes with hydrogen perixide catalysed by benzeneselenic acids and their precursors has been investigated.Bis 2-nitrophenyl diselenide has proved to be the most effective catalyst.The major products resulting from the oxidation are vinyl formates (a) which on hydrolysis give saturated aldehydes or ketones (g) having the carbon chain shortened by one carbon atom, compared with the starting aldehydes.The minor products are formyloxyoxiranes (b), α-hydroxycarbonyl (e) and α-formyloxycarbonyl (f) compounds with the carbon chain shortened by one carbon atom.Carbonyl compounds d, formally derived from an oxidative fission of the carbon-carbon double bond, have been also isolated.Diformyloxy (4c) and formyloxyacetoxy phenylmethane (5c) have been isolated when cinnamaldehyde (4) or 1-phenyl-2-formyloxypropane (5a) were oxidized, respectively.Possible mechanisms of formation of these products are discussed.Similar products resulted when α,β-unsaturated aldehydes were oxidized with organic peroxy acids.
- Syper, Ludwik
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p. 2853 - 2872
(2007/10/02)
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- Aspects of Tautomerism. 13. Alkaline Hydrolysis of γ-, δ-, and ε-Keto Esters and their Desoxy Analogues. Geometrical Constraints on Keto Participation
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The rates of alkaline hydrolysis of methyl β-benzoylpropionate (I), methyl γ-benzoylbutyrate (II) and methyl δ-benzoylvalerate (III) decrease in the order I>II>III.Keto participation is the predominant pathway in the case of γ-keto esters.Evidence has also been obtained for keto participation in the case of δ-keto esters, whereas no such evidence is available in the case of ε-keto esters studied.
- Bhatt, M. Vivekananda,Ravindranathan, M.,Somayaji, Viswanatha,Rao, G. Venkoba
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p. 3170 - 3173
(2007/10/02)
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- Liquid Crystalline Properties of Cholesteryl ω-Arylalkanoates
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The thermal properties of the homologous series of cholesteryl ω-(4-benzoylphenyl)- (I), ω-(4-benzylphenyl)- (II), ω-benzoyl- (III), and ω-phenoxyalkanoate (IV) have been investigated.For series I and II the cholesteric-isotropic (Ch-I) transition temperatures, enthalpies, and entropies show a remarkable alternation.For series III and IV, the transition temperatures, enthalpies, and entropies exhibit weak alternation and their trends are opposite to those for series I and II, and the cholesteryl ω-phenylalkanoates.The cholesteric-isotropic transition temperatures are discussed in terms of the geometrical and electrical alternations stemming from the terminal aryl groups, and also the relative importance between these two terms.
- Koden, Mitsuhiro,Miyake, Shiro,Takenaka, Shunsuke,Kusabayashi, Shigekazu
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p. 2387 - 2390
(2007/10/02)
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- A CONVENIENT METHOD FOR THE DIRECT PREPARATION OF KETONES FROM 2-(6-(2-METHOXYETHYL)PYRIDYL) CARBOXYLATES AND ALKYL IODIDES BY USE OF ZINC DUST AND A CATALYTIC AMOUNT OF NICKEL DICHLORIDE
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Treatment of 2-(6-(2-methoxyethyl)pyridyl) carboxylates with alkyl iodides in the presence of zinc dust and a catalytic amount of NiCl2 in DMF at 50 deg C affords unsymmetrical ketones in good yields by a one-pot procedure.
- Onaka, Makoto,Matsuoka, Yoshio,Mukaiyama, Teruaki
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p. 531 - 534
(2007/10/02)
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- LIQUID-PHASE OXIDATION OF PHENYLCYCLOALKANES BY MOLECULAR OXYGEN. V. COMPOSITION OF THE ACIDIC PRODUCTS FROM OXIDATION OF PHENYLCYCLOHEXANE.
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The composition of the acidic products from the liquid-phase oxidation of phenylcyclohexane by atmospheric oxygen at atmospheric pressure and 120-140 gradC was established. ω-Benzoylvaleric, glutaric, benzoic, and valeric acids are mainly formed with a small amount of other lower mono- and dicarboxylic acids (C1-C4, C6), α- and β-phenyladipic acids, and phenol; their ratio depends on the degree of conversion of the hydrocarbon.Possible paths for the formation of some of the acids were determined on the basis of the obtained kinetic relationships governing the accumulation of the individual acids.
- Velyutin, L.P.,Potekhin, V.M.,Ovchinnikov, V.I.
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p. 862 - 866
(2007/10/02)
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