- Oxidations by the reagent O2-H2O2-vanadium complex - Pyrazine-2-carboxylic acid. Part 7. Hydroperoxidation of higher alkanes
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Alkanes (n-heptane, 2- and 3-methylhexane, cis- and trans-decalin) are readily oxidized under air in acetonitrile by the O2-H2O2-PCA-VO3- reagent at room temperature to produce alkyl hydroperoxides as main products as well as minor amounts of the corresponding alcohols and carbonyl compounds. The site selectivities of the reactions are very similar to those observed with hydroxylation of the alkanes with hydrogen peroxide under UV irradiation. The proposed mechanism involves the catalytic formation of hydroxyl radicals from hydrogen peroxide which abstract hydrogen atoms from the alkanes. The alkyl radicals react rapidly with molecular oxygen to produce peroxyl radicals which are transformed mainly into the hydroperoxides.
- Shul'pin, Georgiy B.,Guerreiro, Mario C.,Schuchardt, Ulf
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- Activation of dioxygen by cobaloxime and nitric oxide for efficient TEMPO-catalyzed oxidation of alcohols
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The aerobic oxidation of alcohols to their corresponding carbonyl compounds could be efficiently accomplished by using the combination of cobalt nitrate, dimethylglyoxime and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) as a novel catalytic system, and various alcohols including primary and secondary benzylic, allylic and aliphatic alcohols could be quantitatively converted to the corresponding aldehydes or ketones at 70 °C under 0.4MPa dioxygen pressure in dichloromethane. During the oxidation, the in situ generated cobaloxime and nitric oxide (NO) were responsible for the activation of dioxygen, respectively, thereby, two concerted catalytic routes exist: cobaloxime-activating-dioxygen TEMPO-catalyzed and NO-activating-dioxygen TEMPO-catalyzed aerobic oxidation of alcohols. Copyright
- Jing, Yuanyuan,Jiang, Jun,Yan, Bo,Lu, Shuai,Jiao, Jiemin,Xue, Huazhen,Yang, Guanyu,Zheng, Gengxiu
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- Synergistic hydrogen atom transfer with the active role of solvent: Preferred one-step aerobic oxidation of cyclohexane to adipic acid by N-hydroxyphthalimide
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In this work, we developed an one-step aerobic oxidation of cyclohexane to prepare adipic acid, catalyzed by N-hydroxyphthalimide (NHPI) under promoter- and metal-free conditions. A significant beneficial solvent effect for synergistic reaction is observed with varying polarity and hydrogen-bonding strength: detailed study reveals that the solvent environments manipulate catalytic activity and adipic acid selectivity. Cyclic voltammetry measurements and UV–visible spectra of the NHPI catalyst are examined in various solvent environments to understand the active role of solvent in influencing the catalytic-site structure (>NOH) of the molecule. Analysis of the UV–visible spectra reveals that these differences can be rationalized by considering hydrogen-bonding with solvent molecules, which modifies the catalytic-site structure. This observation is in agreement with cyclic voltammetry results: the different reversibility of the catalytic-site (>NOH/>NO[rad]) wave shows that the catalytic activity of NHPI is related to the formation of hydrogen bonds with the active participation of solvents. Computational studies presented herein have furnished mechanistic insights into the effect of solvent environments. Specifically, we present the structures, dissociation energies, and reaction barriers from DFT studies of the reactants and reaction intermediates involved in the two types of H-abstraction on >NO[rad] catalytic-sites for the rate-determining step. The results of modeling the solvent effects using the PCM continuum solvent method predict that the resulting reaction barrier of the rate-controlling H-abstraction for cyclohexane and cyclohexanone is modified significantly: the transition state barrier of H-abstraction for cyclohexane decreases from 22.36 (in benzene) to 20.78 kcal?mol?1 (in acetonitrile); the α-H-abstraction barrier for cyclohexanone decreases from 21.45 to 20.53 kcal?mol?1. The active participation of solvent molecule results in a strong interaction between pre-reaction complex (PINO???H???C NO[rad] catalytic-sites at the transition state. The lower calculated barriers of H-abstraction for cyclohexanone oxidation approximate more closely the experimental results of the higher adipic acid selectivity. Our work provides a dimension of sustainable chemistry for the metal-free preparation of adipic acid: a conversion of 27% with 79% adipic acid selectivity is achieved over use of NHPI catalysts in CH3CN solvent.
- Liang, Futong,Zhong, Wenzhou,Xiang, Liping,Mao, Liqiu,Xu, Qiong,Kirk, Steven Robert,Yin, Dulin
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- Manganese(II) based Oxidation of Alkanes: Generation of a High Valent Binuclear Catalyst in situ
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The efficiently Mn2+ -catalysed oxidation of saturated hydrocarbons by alkylhydroperoxides or iodosylbenzene in the presence of 2,2'-bipyridine in acetonitrile follows the following pathway: Mn2+ + bipy -> 2+ -> 3+, the latter being identified as the catalytic species; it affords cyclohexanol and cyclohexanone in equal amounts and the remarkable robustness of the active complex, under oxidative conditions, is noted.
- Menage, Stephane,Collomb-Dunand-Sauthier, Marie-Noe.,Lambeaux, Claude,Fontecave, Marc
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- Effect of cis/trans isomerism on selective oxidation of olefins with nitrous oxide
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Liquid phase oxidation of olefins with nitrous oxide is a promising synthetic route to ketones. The effect of cis/trans isomerism on the reactivity of olefins towards N2O and on the reaction mechanism was studied for the first time using 3-heptene oxidation as an example. Our experimental study revealed that cis- and trans-isomers of 3-heptene have similar reactivity and yield the same set of products. However, the cis/trans isomerism of the olefin has a pronounced effect on the reaction route involving the cleavage of the initial C=C bond and, accordingly, on the products ratio. The yield of ketones is lower for the trans-isomer due to higher contribution of the cleavage route.
- Ivanov, Dmitry,Babushkin, Dmitry,Semikolenov, Sergey,Malykhin, Sergey,Kharitonov, Alexander,Dubkov, Konstantin
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- Redox isomerization of allylic alcohols into carbonyl compounds catalyzed by the ruthenium(IV) complex [Ru(η3:η3-C 10H16)Cl(κ2 O,O -CH3CO 2)] in water and ionic liquids: Highly efficient transformations and catalyst recycling
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Isomerization reactions of allylic alcohols into carbonyl compounds can be efficiently performed in both water and in ionic liquids using [Ru(η3:η3-C10H16) Cl(κ2O,O-CH3CO2)] as catalyst. In both cases, the catalytic system could be recycled up to five times.
- Garcia-Alvarez, Joaquin,Gimeno, Jose,Suarez, Francisco J.
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- Photocatalytic oxidation of heptane in the gas-phase over TiO2
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VOC are important class of air pollutants, which are considered together with NOx, SOx, and particulates as the most important anthropogenic pollutants generated in urban and industrial areas. Gas-phase photocatalytic oxidation (PCO) of heptane over UV-illuminated TiO2 was performed at ambient temperature in a batch reactor. Complete oxidation of heptane with nearly stoichiometric production of CO2 and H2O was obtained. The intermediates were propanal, butanal, 3-heptanone, 4-heptanone, and CO. The photocatalytic activity of TiO2 could be sustained indefinitely due to the production of water in the system, which can replenish the consumed hydroxyl radicals. Reactive oxygen species, e.g., O2/-, O-, O, and ?OH, played important roles in the PCO of heptane. When hydroxyl radicals were consumed in the heterogeneous oxidation reactions, the surface must be continuously rehydrated if long-term catalytic activity is to be maintained.
- Shang,Du,Xu
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- In vitro double oxidation of n-heptane with direct cofactor regeneration
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A novel concept for the direct oxidation of cycloalkanes to the corresponding cyclic ketones in a one-pot synthesis in water with molecular oxygen as sole oxidizing agent was reported recently. Based on this concept we have developed a new strategy for the double oxidation of n-heptane to enable a biocatalytic resolution for the direct synthesis of heptanone and (R)-heptanols in a one-pot reaction. The bicatalytic cascade employs an NADH driven P450 BM3 monooxygenase variant (WTNADH, 19A12NADH or CM1 NADH) and an (S)-enantioselective alcohol dehydrogenase (RE-ADH). In the initial step n-heptane is hydroxylated under consumption of NADH to produce (R/S)-heptanol. In the second oxidation step the (S)-heptanol enantiomers are transformed to the corresponding ketones, reducing and thereby regenerating the cofactor. Characterization of initial hydroxylation step revealed high turnover frequencies (TOF) of up to 600 min-1, as well as high coupling efficiencies using NADH as cofactor (up to 44%). In the cascade reaction a nearly 2-fold improved product formation was achieved, compared to the single hydroxylation reaction. The total product concentration reached 1.1 mM, corresponding to a total turnover number (TTN) of 2500. Implementation of an additional cofactor regeneration system (D-glucose/glucose dehydrogenase) enabled a further enhancement in product formation with a total product concentration of 1.8 mM and a TTN of 3500. Copyright
- Mueller, Christina A.,Akkapurathu, Beneeta,Winkler, Till,Staudt, Svenja,Hummel, Werner,Groeger, Harald,Schwaneberg, Ulrich
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- Mild homogeneous oxidation of alkanes and alcohols including glycerol with tert-butyl hydroperoxide catalyzed by a tetracopper(II) complex
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The homogeneous catalytic system composed of the aqua-soluble tetracopper(II) triethanolaminate complex [O?Cu4{N(CH2CH2O)3}4(BOH)4][BF4]2 (1), t-BuOOH (TBHP), water and acetonitrile solvent (optional) has been applied for the mild oxidation of (i) linear and cyclic alkanes to the corresponding alkyl peroxides, alcohols and ketones, (ii) secondary or primary alcohols to ketones or aldehydes, respectively and (iii) glycerol (GLY) to dihydroxyacetone (DHA). Unusual regio-, bond and stereoselectivity parameters have been determined for the alkane oxygenations and discussed in terms of possible steric, hydrophobic and electronic effects. In alcohol oxidations, secondary alcohols are the most reactive substrates. Yields and TONs up to 82% and 1200, respectively, have been obtained in the oxidation of isopropanol to acetone. The selective oxidation of GLY to DHA by the 1/TBHP system has been also achieved, although providing lower conversions. The 1/H2O2 system for the GLY oxidation is particularly advantageous in terms of selectivity and oxidant efficiency. These systems constitute one of the first examples of a metal-catalyzed oxidation of glycerol under homogeneous conditions.
- Kirillova, Marina V.,Kirillov, Alexander M.,Mandelli, Dalmo,Carvalho, Wagner A.,Pombeiro, Armando J.L.,Shul'Pin, Georgiy B.
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- A NEW SYNTHESIS OF KETONES FROM 1,2-DIMETHOXYETHENYLLITHIUM, ORGANOBORANES, AND ALKYL FLUOROSULFONATES
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The reaction of alkyl fluorosulfonates with lithium 1,2-dimethoxyethenyltrialkylborates readily prepared from organoboranes gives corresponding ketones in good yields.
- Yogo, Toshinobu,Koshino, Junji,Suzuki, Akira
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- Evaluation of catalytic activity of [RuClCp(dmoPTA)(PPh3)](OSO2CF3) in the isomerization of allylic alcohols in water (dmoPTA = 3,7-dimethyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane)
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The catalytic activity of [RuClCp(HdmoPTA)(PPh3)](OSO2CF3) (1) and the dimeric complexes [RuClCp(PPh3)-μ-dmoPTA-1κP:2κ2N,N'-MCl2] (M = Ni (2), Co (3), Zn (4)) for the isomerization in water under Ar and ambient atmosphere of 1-octen-3-ol, 1-hepten-3-ol and 1-hexen-3-ol was investigated. A detailed study was devoted to the catalytic activity under Ar of 1 for the isomerization of 1-octen-3-ol.
- Mena-Cruz, Adrian,Serrano-Ruiz, Manuel,Lorenzo-Luis, Pablo,Romerosa, Antonio,Kathó, ágnes,Joó, Ferenc,Aguilera-Sáez, Luis Manuel
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- Oxidation with the "O2-H2O2-VO3 --pyrazine-2-carboxylic acid" reagent: 6. * Oxidation of n-heptane and cyclohexane. Direct determination of alkyl hydroperoxides by gas-liquid chromatography
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n-Heptane is readily oxidized in acetonitrile under the action of H2O2 with a "vanadate anion-pyrazine-2-carboxylic acid" system as the catalyst in air to form isomeric heptyl hydroperoxides (detected by GLC) along with isomeric heptanols and heptanones. Heptyl hydroperoxides slowly decompose at low temperature yielding the corresponding alcohols and ketones (aldehyde). The values of the parameter of the relative normalized reactivity of the H atoms at the carbon atoms in positions 1, 2, 3, and 4 depend on the reaction time and concentrations of the reagents. The value of the parameter of selectivity C(1) : C(2) : C(3) : C(4) varies in the range from 1.0 : 2.8 : 2.9 : 1.8 to 1.0 : 5.6 : 5.9 : 5.3. The low selectivity of the reaction shows that the key role is played by the attack of highly reactive radical particles on the C-H bond of the alkane molecule.
- Guerreiro,Schuchardt,Shul'pin
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- Water and catalytic isomerization of linear allylic alcohols by [RuCp(H2O-κO)(PTA)2]+ (PTA = 1,3,5-triaza-7-phosphaadamantane)
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A new water soluble complex [RuCp(H2O-κO)(PTA)2]+ (1) (PTA = 1,3,5-triaza-7-phosphaadamantane) has been synthesized and fully characterized by NMR and IR. The crystal structure of 1(CF3SO3)·3.5H2O was characterized by single crystal X-ray determination. The catalytic activity of this complex was evaluated for the isomerisation of linear allylic alcohols from 3-buten-2-ol to 1-octen-3-ol into the correspondent ketones under both an inert atmosphere and in air, using as solvents: water, the substrate, mixtures of water/substrate, MeOH and mixtures of MeOH/water. An isomerization experiment on a mixture of all the studied allylic alcohols was also carried out.
- Scalambra, Franco,Serrano-Ruiz, Manuel,Romerosa, Antonio
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- Oxygenation of alkanes with hydrogen peroxide catalysed by osmium complexes
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Efficient oxidation of alkanes, including methane and ethane, with H2O2 in the presence of catalytic amount of an Os complex in MeCN (addition of nitrogen-containing heterocycles significantly enhances the yield of the products) or in MeCO2H gives the corresponding ketones and alcohols.
- Shul'pin, Georgiy B.,Suess-Fink, Georg,Shul'pina, Lidia S.
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- Oxidation catalysis in air with CpIr: Influence of added ligands and reaction conditions on catalytic activity and stability
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We describe the systematic evaluation of CpIr catalysts for the aerobic oxidation of alcohols. Our results demonstrate turnover numbers up to 270 per [CpIrCl2]2 which have not been previously achieved for this reaction. Using air as the sole oxidant under base-free conditions, the effects of solvent systems and additives on the catalytic activity are documented systematically. We further elucidate the role of additives in catalyst decomposition processes and establish a novel buffer system which results in significant catalyst stabilization upon prolonged reaction times.
- Gunay, Ahmet,Mantell, Mark A.,Field, Kathleen D.,Wu, Wenbo,Chin, Michael,Emmert, Marion H.
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- On the Isolation and Characterization of Methyl(trifluoromethyl)dioxirane
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The title dioxirane 1f, generated by the reaction of CF3COCH3 with potassium peroxomonosulfate, has been isolated and fully characterized spectroscopically; it displays a remarkable reactivity in oxygen transfer reactions.
- Mello, Rossella,Fiorentino, Michele,Sciacovelli, Oronzo,Curci, Ruggero
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- Water-soluble ruthenium(II) catalysts [RuCl2(η6- arene)-{P(CH2OH)3}] for isomerization of allylic alcohols and alkyne hydration
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The novel water-soluble ruthenium(II) complexes [RuCl 2(η6-arene){P(CH2OH)3}] 2a-c and [RuCl(η6-arene){P(CH2OH)3} 2][Cl] 3a-c have been prepared in high yields by reaction of dimers [{Ru(η6-arene)(μ-Cl)Cl}2] (arene = C 6H6 1a, p-cymene 1b, C6Me6 1c) with two or four equivalents of P(CH2OH)3, respectively. Complexes 2/3a-c are active catalysts in the redox isomerization of several allylic alcohols into the corresponding saturated carbonyl compounds under water/n-heptane biphasic conditions. Among them, the neutral derivatives [RuCl2(η6-C6H6){P(CH 2OH)3}] 2a and [RuCl2(η6-p- cymene){P(CH2OH)3}] 2b show the highest activities (TOP values up to 600 h-1; TON values up to 782). Complexes 2/3a-c also catalyze the hydration of terminal alkynes.
- Cadierno, Victorio,Crochet, Pascale,Garcia-Garrido, Sergio E.,Gimeno, Jose
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- Mononuclear Ruthenium and Osmium Complexes with a Bicyclic Guanidinate Ligand: Synthesis and Catalytic Behavior in Olefin Isomerization Processes
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The preparation of the first mononuclear RuII, RuIV, and OsII complexes containing the anion of the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (Hhpp) as a chelating ligand, namely [RuX{κ2-(N,N′)-hpp}(η6-arene)] [arene = p-cymene, X = Cl (2a), Br (2b), I (2c); arene = C6Me6, X = Cl (7)], [RuCl{κ2-(N,N′)-hpp}(η3:η3-C10H16)] (9; C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl), and [OsCl{κ2-(N,N′)-hpp}(η6-p-cymene)] (11), is described. Compounds 2a–c, 7, 9, and 11 have been fully characterized by elemental analysis, HRMS, IR and NMR spectroscopy. In addition, the structure of 2a has been unequivocally confirmed by single-crystal X-ray diffraction methods. The catalytic behavior of these metal guanidinate complexes in the base-free redox isomerization of allylic alcohols is explored, with the ruthenium(IV) derivative 9 showing the best performance (TOF up to 5940 h–1). All of the synthesized complexes have also proven to be active in the isomerization of the allylbenzene estragole into the industrially relevant 1-propenylbenzene anethole, with a trans selectivity of up to 95 %.
- Gámez-Rivera, Sebastián A.,Francos, Javier,Borge, Javier,Cadierno, Victorio
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- New water-soluble iridium(I)-N-heterocyclic carbene-tertiary phosphine mixed-ligand complexes as catalysts of hydrogenation and redox isomerization
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Seven new [Ir(NHC)(η4-cod)(L)] complexes (4-9, 11) with NHC = bmim, emim, L = Cl-, H2O, or the water-soluble phosphines mtppms-Na, mtppts-Na3, and pta were synthesized and characterized. Na2[Ir(bmim)( η4-cod)(mtppts)] (6) and [Ir(bmim)( η4-cod)(pta)]Cl (7) actively catalyzed hydrogenation of alkenoic and oxo acids in aqueous solution. These catalysts were also found to be active in the hydrogenation of highly substituted C=C bonds (such as those in methylmaleic and methylfumaric acids). The stability of 6 was significantly increased by the addition of formate or oxalate. Under hydrogen, active catalysts were formed in situ from [IrCl(bmim)( η4-cod)], [IrCl(η4-cod)(emim)], or [IrCl(η4-cod)(IMes)] and mtppts-Na3 or pta. In the presence of HCOONa, [IrCl(η4-cod)(bmim)] + mtppts-Na3 showed a TOF of 150 h-1in the hydrogenation of itaconic acid in water at 60 °C, which is the highest value determined to date for a water-soluble Ir(I) hydrogenation catalyst in an aqueous system. Both 6 and 7 selectively isomerized alk-1-en-3-ols to the corresponding methyl ketones with no need for an external reducing agent such as H2. Furthermore, Na2[Ir(bmim)( η4-cod)(mtppts)] (6) was also shown to catalytically decompose aqueous formate to H2 and bicarbonate.
- Horvth, Henrietta,Kath, gnes,Udvardy, Antal,Papp, Gbor,Szikszai, Dorina,Jo, Ferenc
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- Cationic and anionic metalloporphyrins simultaneously immobilized onto raw halloysite nanoscrolls catalyze oxidation reactions
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We simultaneously immobilized an anionic iron(III) porphyrin (FePor) and a cationic manganese(III) porphyrin (MnPor) onto raw halloysite nanoscrolls. The positive and negative residual charges at the edges of the halloysite nanoscrolls and the negative residual charges on the surface of this support favored FePor and MnPor immobilization. We characterized the material containing simultaneously immobilized FePor and MnPor (FeMn-Hallo) by powder X-ray diffraction, Fourier transform infrared spectroscopy, textural analysis, and UV-vis spectroscopy (solid sample); these techniques confirmed that both FePor and MnPor were present on the support. We also investigated whether FeMn-Hallo catalyzed cyclooctene epoxidation as well as cyclohexane and n-heptane oxidation. FeMn-Hallo was an effective catalyst for oxidation reaction, attesting the efficiency and versatility of both immobilized metalloporphyrins in the same support. The simultaneous immobilization of metalloporphyrins paves the way for chemists to develop multifunctional catalysts that can simultaneously promote distinct reactions.
- Machado, Guilherme Sippel,Ucoski, Geani Maria,Lima, Omar José De,Ciuffi, Kátia Jorge,Wypych, Fernando,Nakagaki, Shirley
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- Deep eutectic solvents (DES) as green reaction media for the redox isomerization of allylic alcohols into carbonyl compounds catalyzed by the ruthenium complex [Ru(η3:η3-C10H 16)Cl2(benzimidazole)]
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The bis-allyl Ru(IV) complex [Ru(η3:η3-C 10H16)Cl2(benzimidazole)] (1c) is an active catalyst in the redox isomerization of allylic alcohols into saturated carbonyl compounds using, for the first time, Deep eutectic solvents (DES) as reaction media. A series of primary and secondary allylic alcohols could be isomerized into the corresponding carbonyl compounds in the absence of base. Although high activities and selectivities were reached at short reaction times and with low catalyst loadings (0.2 mol% in Ru) for monosubstituted allylic alcohols, for their disubstituted counterparts, high catalyst loading and longer reaction times were always required. It is important to note that the catalytic system: i) is active in a large-scale experiment, and ii) could be recycled up to four consecutive runs.
- Vidal, Cristian,Suárez, Francisco J.,García-álvarez, Joaquín
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- FeCl3-activated oxidation of alkanes by [Os(N)O 3]-
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Although the ion [OsVIII(N)(O)3]- is a stable species and is not known to act as an oxidant for organic substrates, it is readily activated by FeCl3 in CH2Cl2/CH 3CO2H to oxidize alkanes efficiently at room temperature. The oxidation can be made catalytic by using 2,6-dichloropyridine N-oxide as the terminal oxidant. The active intermediates in stoichiometric and catalytic oxidation are proposed to be [(O)3OsVIII≡N-Fe III] and [Cl4(O)OsVIII≡N-Fe III], respectively.
- Yiu, Shek-Man,Wu, Zhi-Biao,Mak, Chi-Keung,Lau, Tai-Chu
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- Robust Mn(iii): N -pyridylporphyrin-based biomimetic catalysts for hydrocarbon oxidations: heterogenization on non-functionalized silica gel versus chloropropyl-functionalized silica gel
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Two classes of heterogenized biomimetic catalysts were prepared and characterized for hydrocarbon oxidations: (1) by covalent anchorage of the three Mn(iii) meso-tetrakis(2-, 3-, or 4-pyridyl)porphyrin isomers by in situ alkylation with chloropropyl-functionalized silica gel (Sil-Cl) to yield Sil-Cl/MnPY (Y = 1, 2, 3) materials, and (2) by electrostatic immobilization of the three Mn(iii) meso-tetrakis(N-methylpyridinium-2, 3, or 4-yl)porphyrin isomers (MnPY, Y = 4, 5, 6) on non-modified silica gel (SiO2) to yield SiO2/MnPY (Y = 4, 5, 6) materials. Silica gel used was of column chromatography grade and Mn porphyrin loadings were deliberately kept at a low level (0.3% w/w). These resulting materials were explored as catalysts for iodosylbenzene (PhIO) oxidation of cyclohexane, n-heptane, and adamantane to yield the corresponding alcohols and ketones; the oxidation of cyclohexanol to cyclohexanone was also investigated. The heterogenized catalysts exhibited higher efficiency and selectivity than the corresponding Mn porphyrins under homogeneous conditions. Recycling studies were consistent with low leaching/destruction of the supported Mn porphyrins. The Sil-Cl/MnPY catalysts were more efficient and more selective than SiO2/MnPY ones; alcohol selectivity may be associated with hydrophobic silica surface modification reminiscent of biological cytochrome P450 oxidations. The use of widespread, column chromatography, amorphous silica yielded Sil-Cl/MnPY or SiO2/MnPY catalysts considerably more efficient than the corresponding, previously reported materials with mesoporous Santa Barbara Amorphous No 15 (SBA-15) silica. Among the materials studied, in situ derivatization of Mn(iii) 2-N-pyridylporphyrin by covalent immobilization on Sil-Cl to yield Sil-Cl/MnP1 showed the best catalytic performance with high stability against oxidative destruction and reusability/recyclability.
- Pinto, Victor Hugo A.,Falc?o, Nathália K. S. M.,Mariz-Silva, Bárbara,Fonseca, Maria Gardennia,Rebou?as, Júlio S.
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- ALKANE HYDROXYLATION CATALYZED BY METALLOPORPHYRINS: EVIDENCE FOR DIFFERENT ACTIVE OXYGEN SPECIES WITH ALKYLHYDROPEROXIDES AND IODOSOBENZENE AS OXIDANTS.
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A comparative study of cyclohexane and n-heptane hydroxylations by cumylhydroperoxide and iodosobenzene, catalyzed by various metalloporphyrins, indicates that different active oxygen species, presumably the cumyloxy radical and a metal-oxo intermediate, are involved in these reactions.
- Mansuy, D.,Bartoli, J-F.,Momenteau, M.
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- Pincer and diamine Ru and Os diphosphane complexes as efficient catalysts for the dehydrogenation of alcohols to ketones
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The ruthenium and osmium complexes [MCl2(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4-bis- (diphenylphosphino)butane), containing the N-H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans-[MCl2(dppf)(en)] (M=Ru 7, Os 13; dppf=1,1′-bis(diphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8-0.04mol% of catalyst. The effect of the base and the comparison of the catalytic activity of the Ru versus Os complexes are reported. The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13, which displays better activity in the dehydrogenation of 5-en-3β-hydroxy steroids. The synthesis of new Ru and Os complexes [MCl2(PP)(L)] (PP=dppb, dppf; L=(±)-trans-1,2-diaminocyclohexane, 2-(aminomethyl) pyridine, and 2-aminoethanol) of trans and cis configuration is also reported. Alcohol breakdown: Ruthenium and osmium phosphane complexes containing nitrogen ligands with the N-H functionality efficiently catalyze the acceptorless dehydrogenation of alcohols. With [MCl2(dppf)(en)] (M=Ru, Os; dppf=1,1′-bis(diphenylphosphino)ferrocene; en=ethylenediamine) in the presence of KOtBu several alcohols have been converted into ketones (see scheme), including sterols for which Os displays a better activity than Ru. Copyright
- Baratta, Walter,Bossi, Gianluca,Putignano, Elisabetta,Rigo, Pierluigi
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- Preparation of Cp-Functionalized N-Heterocyclic Carbene Complexes of Ruthenium. Resolution of Chiral Complexes and Catalytic Studies
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A series of piano-stool ruthenium(II) complexes bearing bidentate cyclopentadienyl-functionalized N-heterocyclic carbene ligands Ru(Cp X-NHC)(CO)I [Cp = tetramethylcyclopentadienyl (Cp*) and tetrabenzylcyclopentadienyl (CpBz)] have been prepared by the diastereoselective reaction of the imidazolium CpX-NHC proligands with [Ru3(CO)12]. The new complexes have been characterized by spectroscopic techniques and X-ray diffraction methods. The enantiopure complexes have been separated by preparative thin-layer chromatography of the diastereomeric mixtures resulting from the reaction of the Ru(CpX-NHC)(CO)I compounds with an auxiliary chiral amine. Ru(Cp*-NHC)(CO)I is an efficient catalyst for the isomerization of allylic alcohols both in water and in THF.
- Da Costa, Andre Pontes,Mata, Jose A.,Royo, Beatriz,Peris, Eduardo
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- One-pot dialkylation of allylphenylsulfide induced by aminoalkoxides- activated NaNH2. Application to the synthesis of unsymmetrical ketones
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It is shown that the activation of NaNH2 by sodium aminoalkoxides, leading to new superbases, induced an efficient one-pot dialkylation of allylphenylsulfide. The regioselectivity of the reaction (α,α' vs α,γ) was found as strongly dependent on the nature of the alkyl halide. As an application, α,γ dialkylated products were efficiently converted Into the corresponding unsymmetrical ketones.
- Choppin, Sabine,Gros, Philippe,Fort, Yves
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- Epoxldation of terminal alkenes with oxygen and 2-ethyl hexanal, without added catalyst or solvent
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Two terminal alkenes, 1-decene and methyl 10-undecenoate, were epoxidized with oxygen using 2-ethyl hexanal as coreactant without any added solvent. Under optimal conditions, the yield of methyl 10, 11-epoxyundecanoate was 98.7%. 2-Ethyl hexanal was oxidized mainly to 2-ethyl hexanoic acid and also formed some byproducts. The tested metal complexes retarded the epoxidation reaction slightly and increased the amount of byproducts of 2-ethyl hexanal.
- Lehtinen, Christel,Brunow, C?sta
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- Efficient catalytic oxidation of alkanes by lewis acid/[Os VI(N)Cl4]- using peroxides as terminal oxidants. Evidence for a metal-based active intermediate
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The oxidation of alkanes by various peroxides (tBuOOH, H 2O2, PhCH2C(CH3)2OOH) is efficiently catalyzed by [OsVI(N)Cl4]-/Lewis acid (FeCl3 or Sc(OTf)3) in CH2Cl 2/CH3CO2H to give alcohols and ketones. Oxidations occur rapidly at ambient conditions, and excellent yields and turnover numbers of over 7500 and 1000 can be achieved in the oxidation of cyclohexane with tBuOOH and H2O2, respectively. In particular, this catalytic system can utilize PhCH2C(CH 3)2OOH (MPPH) efficiently as the terminal oxidant; good yields of cyclohexanol and cyclohexanone (>70%) and MPPOH (>90%) are obtained in the oxidation of cyclohexane. This suggests that the mechanism does not involve alkoxy radicals derived from homolytic cleavage of MPPH but is consistent with heterolytic cleavage of MPPH to produce a metal-based active intermediate. The following evidence also shows that no free alkyl radicals are produced in the catalytic oxidation of alkanes: (1) The product yields and distributions are only slightly affected by the presence of O2. (2) Addition of BrCCl3 does not affect the yields of cyclohexanol and cyclohexanone in the oxidation of cyclohexane. (3) A complete retention of stereochemistry occurs in the hydroxylation of cis- and trans-1,2- dimethylcyclohexane. The proposed mechanism involves initial O-atom transfer from ROOH to [OsVI(N)Cl4]-/Lewis acid to generate [OsVIII(N)(O)Cl4]-/Lewis acid, which then oxidizes alkanes via H-atom abstraction.
- Yiu, Shek-Man,Man, Wai-Lun,Lau, Tai-Chu
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- Copper-catalyzed aerobic oxidative functionalization of C-H bonds of alkanes in the presence of acetaldehyde under mild conditions
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Copper-catalyzed oxidative functionalization of C-H bonds of alkanes with molecular oxygen has been performed in the presence of Cu(OAc)2 catalyst and acetaldehyde in acetonitrile at 70 C with extremely high turn-over numbers.
- Hayashi, Yukiko,Komiya, Naruyoshi,Suzuki, Ken,Murahashi, Shun-Ichi
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- Mechanism of Alcohol Oxidation by trans-Dioxoruthenium(VI): The Effect of Driving Force on Reactivity
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The effect of driving force on the rate of oxidation of alcohols by trans-2+(L1 = (2,2'-bipyridine)2; L2 = N,N'-dimethyl-6,7,8,9,10,11,17,18-octahydro-5H-dibenzodioxadiazacyclopentadecine; L3 = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)propylenediamine; L4 = meso-2,3,7,11,12-pentamethyl-3,7,11,17-tetraazabicycloheptadeca-1(17),13,15-triene; L5 = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) with E0(Ru(VI)-Ru(IV)) ranging from 0.66 zo 1.01 V vs. saturated calomel electrode has been investigated.In most cases the complexes behave as two-electron oxidants being reduced to trans-2+.The rate constants (k2) for alcohol oxidation increases with E0 of the ruthenium oxidant.The slopes of the linear free-energy plots of log k2 vs.E0 for benzyl alcohol and propan-2-ol are -14.7 and -16.9 V-1 respectively.The oxidation is accompanied by large kinetic α-C-H bond in the transition state.For trans-2+ the existence of a linear-free energy relationship between log k2 and the ionization energies of the alcohols and the large negative ρ values in Hammet plots for the oxiation of substituted benzyl alcohols indicate a charge-transfer mechanism.A common mechanism involving either a hydride or hydrogen atom abstraction is proposed.
- Che, Chi-Ming,Tang, Wai-Tong,Lee, Wai-On,Wong, Kwok-Yin,Lau, Tai-Chu
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- Immobilization of anionic metalloporphyrins on zinc hydroxide nitrate and study of an unusual catalytic activity
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This paper is the first report on the immobilization of an anionic iron(III) porphyrin family on zinc hydroxide nitrate (ZHN), a layered hydroxide salt. ZNH was prepared by means of a precipitation reaction between a zinc nitrate solution and ammonium hydroxide. Two immobilization systems were investigated, namely magnetic stirring at room temperature and stirring/reflux in an ethanolic solution. The solids were characterized by powder X-ray diffraction (XRD), electron paramagnetic resonance (EPR), thermogravimetric and derivative thermogravimetric (TGA/DTG), transmission electron microscopy (TEM), as well as ultraviolet-visible (UV-Vis) and Fourier transform infrared (FTIR) spectroscopic analyses. The catalytic activity of the materials was investigated in the oxidation of cyclooctene, cyclohexane, and n-heptane using iodosylbenzene as oxygen donor. The oxidation products were analyzed by gas chromatography. The results revealed an unusual selectivity for cyclohexanone in the reactions of cyclohexane oxidation catalyzed by the anionic iron(III) porphyrins immobilized onto ZHN. These results suggest that the structure of the ZHN support influences the catalytic mechanism and that cyclohexane oxidation occurs via a radicalar pathway.
- MacHado, Guilherme S.,Arizaga, Gregorio G.C.,Wypych, Fernando,Nakagaki, Shirley
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- Mono-oxygenase-like Oxidation of Hydrocarbons using Supported Manganese-Porphyrin Catalysts: Beneficial Effects of a Silica Support for Alkene Hydroxylation
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A suppoted Mn-porphyrin catalyst was prepared by strong adsorption of tetracationic Mn(Cl)4+4Cl- on silica, and was found very efficient for cyclo-octene epoxidation (95 percent yield, 13 turnovers per min) and for alkane hydroxylation, with alcohol yields and alcohol:ketone ratios remarkably highrer than those obtained with corresponding soluble Mn-porphyrins.
- Battioni, Pierette,Lallier, Jean-Pierre,Barloy, Laurent,Mansuy, Daniel
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- Ammonium Acetate as a very Simple and Efficient Cocatalyst for Manganese Porphyrin-catalysed Oxygenation of Hydrocarbons by Hydrogen Peroxide
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A one-phase system using chloromanganese(III) catalyst and ammonium acetate cocatalyst epoxidised alkenes by H2O2 with complete conversion in excellent yield and hydroxylated alkanes with yields of 45-87percent; for most reactions this system gave better results than a previously described analogous system using imidazole cocatalyst.
- Thellend, Annie,Battioni, Pierrette,Mansuy, Daniel
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- Hydrogen bonding Part 44 1Thermodynamics of complexation of 3,5-dichlorophenol with ketones and ethers in cyclohexane: The badger-Bauer relationship
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Equilibrium constants for 1 : 1 hydrogen bond complexation between 3,5-dichioropheno' (DCP) and 17 ketones and 12 ethers in cyclohexane solution have been obtained by an FTIR method that takes into account both diiaerization of the acid and formation of 2 :1 complexes. Enthalpies of complexation for the same ketones and ethers have been determined by a calorimeiric method, leading to values of log K, AG, AH and AS0 for 1 :1 complexation in the 29 systems, as well as log K2 for the 2 :1 complexation between 2 mol of acid and 1 mol of base. For the ketone systems there is very little variation in the three thermodynamic parameters with alkyl substitution, but for the ethers there are systematic variations depending on the alkyl substituent or if the ethers are cyclic. Values of the OH stretching frequency in the DCP complexes with the ketones and ethers in cyclohexane have been obtained. The band shapes for the DCP-ketone complexes are very asymmetric, possibly due to the presence of stereoisomeric complexes, but the VOH band for DCP-ether complexes is symmetric and very suitable for the evaluation of any relationship between v()H and A/f. It is found that for the complexation of DCP with the 12 aliphatic ethers in cyclohexane, there is almost no connection between the calorimetrically determined AH° values and values of AvOH.
- Abraham, Michael H.,Prior, David V.,Schulz, Ronald A.,Morris, Jeffrey J.,Taylor, Peter J.
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- The Application of 1,2-Oxazinanes as Chiral Cyclic Weinreb Amide-Type Auxiliaries Leading to a Three-Component, One-Pot Reaction
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1,2-Oxazines were synthesised via a copper-catalysed aerobic acyl nitroso Diels-Alder reaction from 1,4-disubstituted 1,3-dienes and N-Boc-hydroxylamine. From this, 1,2-oxazinanes were obtained in a novel follow-up reaction path. The stability of several 1,2-oxazines and 1,2-oxazinanes towards organometallic compounds was tested to rate their operability as cyclic chiral Weinreb amide auxiliaries. 3,6-Di-tertbutyl-1,2-oxazinane gave the best results and was introduced as a chiral Weinreb amide-type auxiliary to yield chiral α-substituted ketones in a diastereomeric ratio of up to 98:2. The removal of the auxiliary can be performed with BuLi to form unsymmetrical α-chiral ketones. Thereafter, the chiral auxiliary can be re-isolated and purified by sublimation under vacuum.
- F?hrmann, Jan,Hermann, Ludmila,Hilt, Gerhard
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- OZONE-FACILITATED SELECTIVE OXIDATION OF ALKANES IN LIQUID CARBON DIOXIDE
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A process for the ozonolysis of an alkane may comprise combining an alkane and ozone in a liquid phase medium comprising CO2 under conditions sufficient to oxidize the alkane to produce one or more non-combustion products. The liquid phase medium may be free of a super acid.
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Paragraph 0037
(2018/03/06)
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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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- Mixed-valence μ3-oxo-centered triruthenium cluster [Ru3(II,III,III)(μ3-O)(μ-CH3CO2)6(H2O)3]·2H2O: Synthesis, structural characterization, valence-state delocalization and catalytic behavior
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The oxo-centered, trinuclear, mixed valence [Ru3(II,III,III)O(CH3CO2)6(H2O)3]·2H2O (2) acetate complex has been prepared with high yield through reduction of [Ru3(III,III,III)O(CH3CO2)6(CH3OH)3]·CH3CO2precursor compound in presence of muccic acid under hydrothermal conditions. The crystalline trinuclear oxo-cluster has been obtained as crystalline powder and characterized by single-crystal and powder X-ray diffraction, elemental analysis, SEM, TGA, IR spectroscopy. Complex 2 composes of μ3-oxocentered trinuclear ruthenium array and exhibits the oxidation state delocalization between three Ru atoms at 293 K. Accurate single-crystal analysis along with valence bond calculations reveal trapped-valence state delocalization at room temperature, whereas three-site relaxation occurs at 100 K leading to Ru(II) and Ru2(III) formal states. Moreover, the mixed valence of RuIIRu2IIIunit in compound 2 has been confirmed by XANES spectroscopy. The catalytic behavior of oxo-centered triruthenium complex 2 has been examined in hydration of nitriles and isomerization of allylic alcohols reactions both realized in aqueous media.
- Dikhtiarenko, Alla,Khainakov, Sergei,García, José R.,Gimeno, José
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p. 107 - 116
(2016/11/19)
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- Facile synthesis of [Ru(η2-O2CO)(pta)(η6-p-cymene)], an outstandingly active Ru(II) half-sandwich complex for redox isomerization of allylic alcohols
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The water-soluble [RuCl2(pta)(η6-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-1-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of “in situ” catalyst ([RuCl2(pta)(η6-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(η2-O2CO)(pta)(η6-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction).
- Bolyog-Nagy, Evelin,Udvardy, Antal,Barczáné-Bertók, ágnes,Joó, Ferenc,Kathó, ágnes
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p. 514 - 520
(2016/12/02)
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- Synthesis of new metalloporphyrin derivatives from [5,10,15,20-tetrakis (pentafluorophenyl)porphyrin] and 4-mercaptobenzoic acid for homogeneous and heterogeneous catalysis
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Synthetic metalloporphyrins are catalysts that can efficiently insert oxygen and other atoms such as nitrogen and sulfur in hydrocarbons and in a wide variety of other organic compounds. This work reports on a synthetic strategy to prepare new metalloporphyrins via structural modification of [5,10,15,20-tetrakis (pentafluorophenyl)porphyrin], or [H2(TPFPP)], with 4-mercaptobenzoic acid; it also describes their characterization and catalytic activity. The substituent groups present in the structure of the resulting porphyrins furnished structured solids, which could potentially serve as catalysts in heterogeneous medium. Investigation of the catalytic activity of the new derivatives in the oxidation of (Z)-cyclooctene, cyclohexane, and heptane, under homogeneous conditions, and in the oxidation of (Z)-cyclooctene, in heterogeneous medium, proved that the new metalloporphyrins constituted excellent catalysts for (Z)-cyclooctene epoxidation. As for alkane oxidation, they selectively gave the corresponding alcohol in good yields.
- de F. Castro, Kelly A.D.,Sim?es, Mário M.Q.,da Gra?a P.M.S. Neves, Maria,Cavaleiro, José A.S.,Ribeiro, Ronny R.,Wypych, Fernando,Nakagaki, Shirley
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- Catalytic oxidation of alkanes by a (salen)osmium(VI) nitrido complex using H2O2 as the terminal oxidant
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The osmium(vi) nitrido complex, [OsVI(N)(L)(CH3OH)]+ (1, L = N,N′-bis(salicylidene)-o-cyclohexyldiamine dianion) is an efficient catalyst for the oxidation of alkanes under ambient conditions using H2O2 as the oxidant. Alkanes are oxidized to the corresponding alcohols and ketones, with yields up to 75% and turnover numbers up to 2230. Experimental and computational studies are consistent with a mechanism that involves O-atom transfer from H2O2 to [OsVI(N)(L)]+ to generate an [OsVIII(N)(O)(L)]+ active intermediate.
- Chen, Man,Pan, Yi,Kwong, Hoi-Ki,Zeng, Raymond J.,Lau, Kai-Chung,Lau, Tai-Chu
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supporting information
p. 13686 - 13689
(2015/09/02)
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- Regioselective Isomerization of 2,3-Disubstituted Epoxides to Ketones: An Alternative to the Wacker Oxidation of Internal Alkenes
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We report an alternative pathway to the Wacker oxidation of internal olefins involving epoxidation of trans-alkenes followed by a mild and highly regioselective isomerization to give the major ketone isomers in 66-98% yield. Preliminary kinetics and isotope labeling studies suggest epoxide ring opening as the turnover limiting step in our proposed mechanism. A similar catalytic system was applied to the kinetic resolution of select trans-epoxides to give synthetically useful selectivity factors of 17-23 for benzyl-substituted substrates.
- Lamb, Jessica R.,Mulzer, Michael,Lapointe, Anne M.,Coates, Geoffrey W.
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supporting information
p. 15049 - 15054
(2015/12/08)
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- Highly efficient alkane oxidation catalyzed by [MnV(N)(CN) 4]2-. Evidence for [MnVII(N)(O)(CN) 4]2- as an active intermediate
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The oxidation of various alkanes catalyzed by [MnV(N)(CN) 4]2- using various terminal oxidants at room temperature has been investigated. Excellent yields of alcohols and ketones (>95%) are obtained using H2O2 as oxidant and CF3CH 2OH as solvent. Good yields (>80%) are also obtained using (NH4)2[Ce(NO3)6] in CF 3CH2OH/H2O. Kinetic isotope effects (KIEs) are determined by using an equimolar mixture of cyclohexane (c-C6H 12) and cyclohexane-d12 (c-C6D12) as substrate. The KIEs are 3.1 ± 0.3 and 3.6 ± 0.2 for oxidation by H2O2 and Ce(IV), respectively. On the other hand, the rate constants for the formation of products using c-C6H12 or c-C6D12 as single substrate are the same. These results are consistent with initial rate-limiting formation of an active intermediate between [Mn(N)(CN)4]2- and H2O2 or CeIV, followed by H-atom abstraction from cyclohexane by the active intermediate. When PhCH2C(CH3)2OOH (MPPH) is used as oxidant for the oxidation of c-C6H12, the major products are c-C6H11OH, c-C6H10O, and PhCH2C(CH3)2OH (MPPOH), suggesting heterolytic cleavage of MPPH to generate a Mn=O intermediate. In the reaction of H2O2 with [Mn(N)(CN)4]2- in CF 3CH2OH, a peak at m/z 628.1 was observed in the electrospray ionization mass spectrometry, which is assigned to the solvated manganese nitrido oxo species, (PPh4)[Mn(N)(O)(CN)4] -·CF3CH2OH. On the basis of the experimental results the proposed mechanism for catalytic alkane oxidation by [MnV(N)(CN)4]2-/ROOH involves initial rate-limiting O-atom transfer from ROOH to [Mn(N)(CN)4]2- to generate a manganese(VII) nitrido oxo active species, [MnVII(N)(O) (CN)4]2-, which then oxidizes alkanes (R'H) via a H-atom abstraction/O-rebound mechanism. The proposed mechanism is also supported by density functional theory calculations.
- Ma, Li,Pan, Yi,Man, Wai-Lun,Kwong, Hoi-Ki,Lam, William W.Y.,Chen, Gui,Lau, Kai-Chung,Lau, Tai-Chu
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p. 7680 - 7687
(2014/06/10)
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- MONOMER, POLYMER, RESIST COMPOSITION, AND PATTERNING PROCESS
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A polymer comprising recurring units derived from a (meth)acrylate monomer of tertiary ester type having branched alkyl on alicycle is used to form a resist composition. When subjected to exposure, PEB and organic solvent development, the resist composition is improved in dissolution contrast.
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- The iron(II) complex [Fe(CF3SO3)2(mcp)] as a convenient, readily available catalyst for the selective oxidation of methylenic sites in alkanes
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The efficient and selective oxidation of secondary C-H sites of alkanes is achieved by using low catalyst loadings of a non-expensive, readily available iron catalyst [Fe(II)(CF3SO3)2(mcp)], {Fe-mcp, [mcp=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)cyclohexane-trans-1,2-diamine]}, and hydrogen peroxide (H2O2) as oxidant, via a simple reaction protocol. Natural products are selectively oxidized and isolated in synthetically amenable yields. The easy access to large quantities of the catalyst and the simplicity of the C-H oxidation procedure make this system a particularly convenient tool to carry out alkane C-H oxidation reactions on the preparative scale, and in short reaction times.
- Canta, Merce,Font, David,Gomez, Laura,Ribas, Xavi,Costas, Miquel
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supporting information
p. 818 - 830
(2014/04/03)
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- Tethered η5-oxocyclohexadienyl piano-stool ruthenium(II) complexes: A new class of catalysts?
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The straightforward synthesis of tethered η5-oxocyclohexadienyl Ru(II) complexes is presented. Pioneering results in catalysis show that these original half-sandwich Ru(II) complexes allow the effective isomerization of allylic alcohols under mild conditions without further additives; η5-oxocyclohexadienyl ruthenium complexes may be considered as a new class of catalysts.
- Kechaou-Perrot, Manel,Vendier, Laure,Bastin, Stphanie,Sotiropoulos, Jean-Marc,Miqueu, Karinne,Menndez-Rodrguez, Luca,Crochet, Pascale,Cadierno, Victorio,Igau, Alain
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supporting information
p. 6294 - 6297
(2015/02/19)
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- Regioselective oxidation of nonactivated alkyl C-H groups using highly structured non-heme iron catalysts
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Selective oxidation of alkyl C-H groups constitutes one of the highest challenges in organic synthesis. In this work, we show that mononuclear iron coordination complexes Λ-[Fe(CF3SO3) 2((S,S,R)-MCPP)] (Λ-1P), Δ-[Fe(CF3SO 3)2((R,R,R)-MCPP)] (Δ-1P), Λ-[Fe(CF 3SO3)2((S,S,R)-BPBPP)] (Λ-2P), and Δ-[Fe(CF3SO3)2((R,R,R)-BPBPP)] (Δ-2P) catalyze the fast, efficient, and selective oxidation of nonactivated alkyl C-H groups employing H2O2 as terminal oxidant. These complexes are based on tetradentate N-based ligands and contain iron centers embedded in highly structured coordination sites defined by two bulky 4,5-pinenopyridine donor ligands, a chiral diamine ligand backbone, and chirality at the metal (Λ or Δ). X-ray diffraction analysis shows that in Λ-1P and Λ-2P the pinene rings create cavity-like structures that isolate the iron site. The efficiency and regioselectivity in catalytic C-H oxidation reactions of these structurally rich complexes has been compared with those of Λ-[Fe(CF3SO3) 2((S,S)-MCP)] (Λ-1), Λ-[Fe(CF3SO 3)2((S,S)-BPBP)] (Λ-2), Δ-[Fe(CF 3SO3)2((R,R)-BPBP)] (Δ-2), Λ-[Fe(CH3CN)2((S,S)-BPBP)](SbF6) 2 (Λ-2SbF6), and Δ-[Fe(CH3CN) 2((R,R)-BPBP)](SbF6)2 (Δ-2SbF 6), which lack the steric bulk introduced by the pinene rings. Cavity-containing complexes Λ-1P and Λ-2P exhibit enhanced activity in comparison with Δ-1P, Δ-2P, Λ-1, Λ-2, and Λ-2SbF6. The regioselectivity exhibited by catalysts Λ-1P, Λ-2P, Δ-1P, and Δ-2P in the C-H oxidation of simple organic molecules can be predicted on the basis of the innate properties of the distinct C-H groups of the substrate. However, in specific complex organic molecules where oxidation of multiple C-H sites is competitive, the highly elaborate structure of the catalysts allows modulation of C-H regioselectivity between the oxidation of tertiary and secondary C-H groups and also among multiple methylene sites, providing oxidation products in synthetically valuable yields. These selectivities complement those accomplished with structurally simpler oxidants, including non-heme iron catalysts Λ-2 and Λ-2SbF6.
- Gómez, Laura,Canta, Merceì,Font, David,Prat, Irene,Ribas, Xavi,Costas, Miquel
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p. 1421 - 1433
(2013/03/29)
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- N-alkyl functionalised expanded ring N-heterocyclic carbene complexes of rhodium(i) and iridium(i): Structural investigations and preliminary catalytic evaluation
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A series of new N-alkyl functionalised 6- and 7-membered expanded ring N-heterocyclic carbene (NHC) pro-ligands 3-6 and their corresponding complexes of rhodium(i) and iridium(i), [M(NHC)(COD)Cl] 7-14 and [M(NHC)(CO) 2Cl] 15-22 are described. The complexes have been characterised by 1H and 13C{1H} NMR, mass spectrometry, IR and X-ray diffraction. It is noted from X-ray diffraction studies that the N-alkyl substituents are found to orientate themselves away from the metal centre due to unfavourable steric interactions resulting in low percent buried volume (%Vbur) values in the solid state. The heterocycle ring size is also found to dictate the spatial orientation of the N-alkyl substituents in the neopentyl functionalised derivatives 10 and 14. The 7-membered derivative 14 allows for a conformational 'twist' of the heterocycle ring with the N-alkyl substituents adopting a mutually trans configuration with respect to each other, while the more rigid 6-membered system 10 does not allow for this conformational 'twist' and consequently the N-alkyl substituents adopt a mutually cis configuration. The σ-donor function of this new class of expanded ring NHC ligand has also been probed by measured IR stretching frequencies of the [M(NHC)(CO)2Cl] complexes 15-22. A preliminary catalytic survey of the hydrogenation of functionalised alkenes with molecular hydrogen under mild conditions has also been undertaken with complex 10, affording an insight into the application of large ring NHC ancillary ligands bearing N-alkyl substituents in hydrogenation transformations.
- Dunsford, Jay J.,Tromp, Dorette S.,Cavell, Kingsley J.,Elsevier, Cornelis J.,Kariuki, Benson M.
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p. 7318 - 7329
(2013/08/26)
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- Oxidative C-C bond cleavage of aldehydes via visible-light photoredox catalysis
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The visible-light mediated oxidative C-C bond cleavage of aldehydes has been achieved in good yields at ambient temperature and open to air using Ru(bpy)3Cl2 (bpy = 2,2′-bipyridine) as the photoredox catalyst. Moreover, we further demonstrated the application in a tandem Michael/oxidative C-C bond cleavage reaction.
- Sun, Hongnan,Yang, Chao,Gao, Fei,Li, Zhe,Xia, Wujiong
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supporting information
p. 624 - 627
(2013/04/23)
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- Hydrogenation and redox isomerization of allylic alcohols catalyzed by a new water-soluble Pd-tetrahydrosalen complex
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For applications in aqueous media, sulfonated tetrahydrosalen (sulfosalan, HSS) was synthesized by sulfonation of tetrahydrosalen in fuming sulfuric acid. The Pd(II) complex of this ligand, [Pd(HSS)], showed outstanding activity in hydrogenation and redox isomerization of allylic alcohols in homogeneous aqueous solutions or in aqueous-organic biphasic systems (for oct-1-en-3-ol TOF(hydrogenation) = 1580 h-1, TOF(redox isomerization) = 400 h -1). DFT calculations revealed that H2 is activated heterolytically, resulting in a Pd(II)-hydride complex, [Pd(H)(HSS-Hphen)], in which one of the phenolate oxygens is protonated. Both hydrogenation and redox isomerization take place via concerted transfer of a proton and a hydride from the hydrogenated catalyst to the allylic alcohol.
- Voronova, Krisztina,Purgel, Mihaly,Udvardy, Antal,Benyei, Attila C.,Katho, Agnes,Joo, Ferenc
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p. 4391 - 4401
(2013/09/02)
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- Catalytic isomerization of allylic alcohols promoted by complexes [RuCl2(η6-arene)(PTA-Me)] under homogeneous conditions and supported on Montmorillonite K-10
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The mononuclear arene-ruthenium(II) derivatives [RuCl2(η 6-arene)(PTA-Me)] (arene = C6H6 (3a), p-cymene (3b), 1,3,5-C6H3Me3 (3c), C6Me 6 (3d)), containing the ionic phosphine ligand 1-methyl-3,5-diaza-1- azonia-7-phosphaadamantane chloride (PTA-Me), have been synthesized and fully characterized. These complexes were evaluated as potential catalysts for the redox isomerization of allylic alcohols. Among them, best results in terms of activity were obtained with complex [RuCl2(η6-C 6H6)(PTA-Me)] (3a) which, in combination with K 2CO3 (2.5 equiv. per Ru), was able to selectively isomerize a number of allylic alcohols RCH(OH)CHCH2 (R = H, aryl, alkyl or heteroaryl group) into the corresponding carbonyl compounds RC(O)CH2CH3 in refluxing THF (TOF values up to 800 h -1). Complex [RuCl2(η6-C6H 6)(PTA-Me)] (3a) was adsorbed onto the Montmorillonite K-10 clay, and the resulting solid proved also active in the isomerization of the model substrate 1-octen-3-ol. In addition, it could be easily separated from the reaction media by simple filtration and reused several times (up to 11 consecutive runs) with retention of its efficiency.
- Menéndez-Rodríguez, Lucía,Crochet, Pascale,Cadierno, Victorio
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p. 390 - 399
(2013/02/21)
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- Rapid aerobic oxidation of alcohols to carbonyl compounds with dioxygen using metallodeuteroporphyrin dimethyl esters as catalysts in the presence of isobutylaldehyde
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A facile biomimetic method for rapid oxidation of alcohols to carbonyl compounds using dioxygen as the primary oxidant catalyzed by metallodeuteroporphyrin dimethyl ester [M(DPDME)] in acetonitrile as the reaction solvent and isobutylaldehyde as cocatalyst has been investigated. Among the M(DPDME) catalysts, where M = Fe(III), Co(II), Mn(III), Ni(II), Cu(II), and Zn(II), cobalt porphyrin was found to be the most active and effective catalyst. The catalytic system was widely used in the oxidation of various alcohols and especially exhibited excellent activity for oxidation of aromatic alcohols under mild conditions. Moreover, M(DPDME) was prepared from an improved facile method by chemical modification of natural hemin and an alternative mechanism for the aerobic oxidation of alcohols has been proposed and discussed.
- Sun, Chengguo,Hu, Bingcheng,Liu, Zuliang
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experimental part
p. 295 - 303
(2012/07/28)
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- Role of Fe(IV)-oxo intermediates in stoichiometric and catalytic oxidations mediated by iron pyridine-azamacrocycles
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An iron(II) complex with a pyridine-containing 14-membered macrocyclic (PyMAC) ligand L1 (L1 = 2,7,12-trimethyl-3,7,11,17-tetra-azabicyclo[11.3.1] heptadeca-1(17),13,15-triene), 1, was prepared and characterized. Complex 1 contains low-spin iron(II) in a pseudo-octahedral geometry as determined by X-ray crystallography. Magnetic susceptibility measurements (298 K, Evans method) and Moessbauer spectroscopy (90 K, δ = 0.50(2) mm/s, ΔEQ = 0.78(2) mm/s) confirmed that the low-spin configuration of Fe(II) is retained in liquid and frozen acetonitrile solutions. Cyclic voltammetry revealed a reversible one-electron oxidation/reduction of the iron center in 1, with E1/2(FeIII/FeII) = 0.49 V vs Fc+/Fc, a value very similar to the half-wave potentials of related macrocyclic complexes. Complex 1 catalyzed the epoxidation of cyclooctene and other olefins with H2O2. Low-temperature stopped-flow kinetic studies demonstrated the formation of an iron(IV)-oxo intermediate in the reaction of 1 with H2O2 and concomitant partial ligand oxidation. A soluble iodine(V) oxidant, isopropyl 2-iodoxybenzoate, was found to be an excellent oxygen atom donor for generating Fe(IV)-oxo intermediates for additional spectroscopic (UV-vis in CH3CN: λmax = 705 nm, ε ≈ 240 M-1 cm-1; Moessbauer: δ = 0.03(2) mm/s, ΔEQ = 2.00(2) mm/s) and kinetic studies. The electrophilic character of the (L1)FeIV=O intermediate was established in rapid (k2 = 26.5 M-1 s-1 for oxidation of PPh3 at 0 °C), associative (ΔH a = 53 kJ/mol, ΔS a = -25 J/K mol) oxidation of substituted triarylphosphines (electron-donating substituents increased the reaction rate, with a negative value of Hammet's parameter ρ = -1.05). Similar double-mixing kinetic experiments demonstrated somewhat slower (k2 = 0.17 M-1 s-1 at 0 °C), clean, second-order oxidation of cyclooctene into epoxide with preformed (L1)FeIV=O that could be generated from (L1)FeII and H2O2 or isopropyl 2-iodoxybenzoate. Independently determined rates of ferryl(IV) formation and its subsequent reaction with cyclooctene confirmed that the Fe(IV)-oxo species, (L1)FeIV=O, is a kinetically competent intermediate for cyclooctene epoxidation with H2O2 at room temperature. Partial ligand oxidation of (L1)FeIV=O occurs over time in oxidative media, reducing the oxidizing ability of the ferryl species; the macrocyclic nature of the ligand is retained, resulting in ferryl(IV) complexes with Schiff base PyMACs. NH-groups of the PyMAC ligand assist the oxygen atom transfer from ferryl(IV) intermediates to olefin substrates.
- Ye, Wanhua,Ho, Douglas M.,Friedle, Simone,Palluccio, Taryn D.,Rybak-Akimova, Elena V.
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scheme or table
p. 5006 - 5021
(2012/06/15)
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- MCl2(ampy)(dppf) (M = Ru, Os): Multitasking catalysts for carbonyl compound/alcohol interconversion reactions
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The easily accessible complexes [MCl2(dppf)(ampy)] (M = Ru (cis-1), Os (trans-2); dppf = 1,1′-bis(diphenylphosphino)ferrocene; ampy = 2-aminomethylpyridine) in the presence of base (NaOiPr, KOtBu) are efficient catalysts for several reactions involving carbonyl compounds and alcohols. The derivatives 1 and 2 catalyze the selective transfer hydrogenation of aldehydes and ketones to alcohols with 2-propanol using 0.1-0.005 mol % of catalyst at 82 °C with TOF values up to 3.0 × 105 h-1. These compounds (0.1-0.02 mol %) promote the hydrogenation of aldehydes and ketones in EtOH or a MeOH/EtOH mixture at 30-90 °C (5 atm of H2) and the acceptorless dehydrogenation of alcohols to ketones in tBuOH at 130-145 °C (0.4 mol %). Complexes 1 and 2 (0.5 mol %) catalyze the racemization of chiral alcohols at 70 °C in 2-propanol and the isomerization of allylic alcohols to ketones in tBuOH at 70-120 °C (1 mol %). In addition, 1 and 2 (0.5 mol %) promote the α alkylation of α-tetralone with primary alcohols (EtOH, nPrOH, and nBuOH) at 120 °C in a tBuOH/toluene mixture (1/2 v/v). Complex 2 is easily obtained in 93% yield from [OsCl2(PPh3) 3], dppf, and ampy in toluene.
- Putignano, Elisabetta,Bossi, Gianluca,Rigo, Pierluigi,Baratta, Walter
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experimental part
p. 1133 - 1142
(2012/04/04)
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- Highly efficient redox isomerisation of allylic alcohols catalysed by pyrazole-based ruthenium(IV) complexes in Water: Mechanisms of bifunctional catalysis in water
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The catalytic activity of ruthenium( IV) ([Ru(h3 :h 3-C10H16)Cl2L]; C10H 16=2,7-dimethylocta-2,6-diene-1,8-diyl, L=pyrazole, 3-methylpyrazole, 3,5-dimethylpyrazole, 3-methyl-5-phenylpyrazole, 2-(1H-pyrazol-3-yl)phenol or indazole) and ruthenium(II) complexes ([Ru(h6-arene)Cl 2(3,5-dimethylpyrazole)]; arene=C6H6, p-cymene or C6Me6) in the redox isomerisation of allylic alcohols into carbonyl compounds in water is reported. The former show much higher catalytic activity than ruthenium(II) complexes. In particular, a variety of allylic alcohols have been quantitatively isomerised by using [Ru(h3 :h3-C10H16)Cl2(pyrazole)] as a catalyst; the reactions proceeded faster in water than in THF, and in the absence of base. The isomerisations of monosubstituted alcohols take place apidly (10-60 min, turn-over frequency= 750-3000 h-1) and, in some cases, at 35 8C in 60 min. The nature of the aqueous species formed in water by this complex has been analysed by ESI-MS. To analyse how an aqueous medium can influence the mechanism of the bifunctional catalytic process, DFT calculations (B3LYP) including one or two explicit water molecules and using the polarisable continuum model have been carried out and provide a valuable insight into the role of water on the activity of the bifunctional catalyst. Several mechanisms have been considered and imply the formation of aqua complexes and their deprotonated species generated from [Ru(h3 :h3-C 10H16)Cl2(pyrazole)]. Different competitive pathways based on outer-sphere mechanisms, which imply hydrogen-transfer processes, have been analysed. The overall isomerisation implies two hydrogen-transfer steps from the substrate to the catalyst and subsequent transfer back to the substrate. In addition to the conventional Noyori outer-sphere mechanism, which involves the pyrazolide ligand, a new mechanism with a hydroxopyrazole complex as the active species can be at work in water. The possibility of formation of an enol, which isomerizes easily to the keto form in water, also contributes to the efficiency in water.
- Bellarosa, Luca,Diez, Josefina,Gimeno, Jos,Lledos, Agusti,Suarez, Francisco J.,Ujaque, Gregori,Vicent, Cristian
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experimental part
p. 7749 - 7765
(2012/09/22)
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- Ruthenium(II) Arene complexes with asymmetrical guanidinate ligands: Synthesis, characterization, and application in the base-free catalytic isomerization of allylic alcohols
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The ruthenium(II) arene dimer [{RuCl(μ-Cl)(η6-p-cymene)} 2] readily reacted with 4 equiv of guanidines (iPrHN) 2C=NR (R = iPr (1a), 4-C6H4 tBu (1b), 4-C6H4Br (1c), 2,4,6-C 6H2Me3 (1d), 2,6-C6H 3iPr2 (1e)) in toluene at room temperature to generate the mononuclear complexes [RuCl{κ2N,N'-C(NR)(N iPr)NHiPr}(η6-p-cymene)] (2a-e) and the easily separable guanidinium chloride salts [(iPrHN) 2C(NHR)][Cl] (3a-e). Compounds 2a-e and 3a-e were fully characterized by elemental analysis and IR and NMR spectroscopy. The structures of [RuCl{κ2N,N'-C(NiPr)2NH iPr}(η6-p-cymene)] (2a) and [RuCl{κ 2N,N'-C(N-4-C6H4tBu)(N iPr)NHiPr}(η6-p-cymene)] (2b) were also determined by X-ray diffraction analysis. Regardless of the steric requirements of the aromatic substituents, a nonsymmetric coordination of the guanidinate anions in 2b-e was observed, in complete accord with theoretical calculations (DFT) on the corresponding [RuCl{κ2N,N'-C(NR)(N iPr)-NHiPr}(η6-p-cymene)] and [RuCl{κ2N,N'-C(NiPr)2NHR} (η6-p-cymene)] models. Remarkably, complexes 2a-e were active catalysts for the redox isomerization of allylic alcohols in the absence of base, which represents the first catalytic application known for ruthenium guanidinate species.
- Garcia-Alvarez, Rocio,Suarez, Francisco J.,Diez, Josefina,Crochet, Pascale,Cadierno, Victorio,Antinolo, Antonio,Fernandez-Galan, Rafael,Carrillo-Hermosilla, Fernando
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p. 8301 - 8311
(2013/02/22)
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- Highly efficient redox isomerization of allylic alcohols and transfer hydrogenation of ketones and aldehydes catalyzed by ruthenium complexes
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A dicationic dichloro-bipyridine-ruthenium complex shows very high catalytic activity in redox isomerization of allylic alcohols but a relatively low one in transfer hydrogenation of ketones; surprisingly, the analogous dimethyl-bipyridine-ruthenium complex shows reverse catalytic activities in the two reactions.
- Liu, Pei Nian,Ju, Kun Dong,Lau, Chak Po
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supporting information; experimental part
p. 275 - 280
(2011/04/16)
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- Redox isomerization of allylic alcohols catalyzed by osmium and ruthenium complexes containing a cyclopentadienyl ligand with a pendant amine or phosphoramidite group: X-ray structure of an η3-1-hydroxyallyl- metal-hydride intermediate
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Complexes [MCl2(η6-p-cymene)]2 (M = Os (1a), Ru (1b)) react with Li(C5H4CH2CH 2NHMe) (LiCpN) and KPF6 to give the sandwich derivatives [M(η5-CpN)(η6-p-cymene)] PF6 (M = Os (2a), Ru (2b)). Treatment of 2a and 2b with (2,2--biphenol)PCl leads to [M(η5-CpP) (η6-p-cymene)]PF6 (M = Os (3a), Ru (3b); Cp P = C5H4CH2CH2N(Me)P(2,2- -biphenol)). The photolysis of 2a, 2b, 3a, and 3b in acetonitrile produces the release of the p-cymene group and the coordination of the cyclopentadienyl pendant substituent to the metal center to afford [M(η5-C 5,κ-N-CpN)(CH3CN)2]PF 6 (M = Os (4a), Ru (4b)) and [M(η5-C 5,κ-P-CpP)(CH3CN)2]PF 6 (M = Os (5a), Ru (5b)). Complex 4a, which has been characterized by X-ray diffraction analysis, is a more efficient catalyst precursor than 4b for the redox isomerization of primary allylic alcohols, while the latter is more efficient than the former for the redox isomerization of secondary allylic alcohols. From the catalytic solutions containing 4a and 2-methyl-2-propen-1-ol, the η3-1-hydroxyallyl complex [OsH(η5-C 5,κ-N-CpN){η3-CH2C(CH 3)CHOH}]PF6 (6) has been crystallized and characterized by spectroscopic methods and X-ray diffraction analysis. The structure shows a N-HO hydrogen bond (2.22 a) between the NH-hydrogen atom of the coordinated pendant amine group and the oxygen atom of the hydroxy substituent of the allyl ligand.
- Batuecas, Maria,Esteruelas, Miguel A.,Garcia-Yebra, Cristina,Onate, Enrique
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scheme or table
p. 2166 - 2175
(2010/07/03)
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- Catalysis of redox isomerization of allylic alcohols by [RuClCp(mPTA)2](OSO2CF3)2 and [RuCp(mPTA)2(OH2-κO)](OSO2CF3)3·(H2O)(C4H10O)0.5. Unusual influence of the pH and interaction of phosphate with catalyst on the reaction rate
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In aqueous solutions at 80 °C, [RuClCp(mPTA)2](OSO2CF3)2 (1) and [RuCp(mPTA)2(OH2-κO)](OSO2CF3)3·(H2O)(C4H10O)0.5 (3) (mPTA: N-methyl-PTA) were found effective catalysts of the redox isomerization of alk-1-en-3-ols to the corresponding ketones, characterized by initial turnover frequencies (TOF) of 162 h-1 (3) and 9.6 h-1 (1) in 1-octen-3-ol isomerization. A sharp maximum of the reaction rate as a function of pH was observed with 1 in phosphate buffer solutions. Kinetic and 31P NMR measurements revealed for the first time in aqueous organometallic catalysis that component(s) of phosphate buffer (most probably HPO42-) strongly interact(s) with the catalyst complexes and this interaction leads to a dramatic loss of the catalytic activity.
- González, Beatríz,Lorenzo-Luis, Pablo,Serrano-Ruiz, Manuel,Papp, éva,Fekete, Marianna,Csépke, Klára,Osz, Katalin,Kathó, ágnes,Joó, Ferenc,Romerosa, Antonio
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experimental part
p. 15 - 20
(2010/10/01)
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- Alkane oxidation by the H2O2-NaVO3-H2SO4 system in acetonitrile and water
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A simple system is described, which oxidizes saturated hydrocarbons either in acetonitrile or (less efficiently) in water. The system consists of 50% aqueous hydrogen peroxide as an oxidant, sodium metavanadate, NaVO3, as a catalyst and sulfuric (or oxalic) acid as a co-catalyst. The reactions were carried out at 20-50 °C. In the oxidation of cyclohexane in acetonitrile, the highest yield (37% based on cyclohexane) and turnover number (TON=1700) were attained after 3 h at 50 °C. The corresponding parameters were 16% and 1090 for n-heptane oxidation under the same conditions. The oxidation of higher alkanes, RH, in acetonitrile gives almost exclusively the corresponding alkyl hydroperoxides, ROOH. Light alkanes (n-butane, propane, ethane, and methane) have been also oxygenated by the system under consideration. The highest TON (200) was attained for ethane and the highest yield (19%) was obtained in the case of n-butane. The selectivity parameters measured for the oxidation of linear and branched alkanes are low, the reaction with cis- and trans-1,2-dimethylcyclohexanes is not stereoselective. These facts lead us to conclude that the oxidation occurs with the formation of hydroxyl radicals in the crucial step.
- Shul'pina, Lidia S.,Kirillova, Marina V.,Pombeiro, Armando J.L.,Shul'pin, Georgiy B.
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experimental part
p. 2424 - 2429
(2009/07/25)
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- Catalytic activity dependency on catalyst components in aerobic copper-TEMPO oxidation
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The influence of catalyst components in the copper-TEMPO (2,2,6,6-tetramethylpiperidine N-oxide) catalysed aerobic oxidation of alcohols was investigated. The type and amount of base greatly influences reactivity. The bipyridyl ligand concentration had no major influence on catalysis, but ex-cessive amounts led to a decrease in activity for longer reaction times. The kinetic dependency for TEMPO was found to be 1.15, and for copper 2.25, which is an indication of a binuclear catalytic system. Optimised conditions with various allylic and aliphatic alcohols give good to excellent rapid oxidations.
- Kumpulainen, Esa T. T.,Koskinen, Ari M. P.
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experimental part
p. 10901 - 10911
(2010/04/05)
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- Ruthenium-catalyzed redox isomerization/transfer hydrogenation in organic and aqueous media: A one-pot tandem process for the reduction of allylic alcohols
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The hexamethylbenzene-ruthenium(ii) dimer [{RuCl(μ-Cl) (η6-C6Me6)}2] 1 and the mononuclear bis(allyl)-ruthenium(iv) complex [RuCl2(η 3:η2:η3-C12H 18)]2, associated with base and a hydrogen donor, were found to be active catalysts for the selective reduction of the CC bond of allylic alcohols both in organic and aqueous media. The process, which proceeds in a one-pot manner, involves a sequence of two independent reactions: (i) the initial redox-isomerization of the allylic alcohol, and (ii) subsequent transfer hydrogenation of the resulting carbonyl compound. The highly efficient transformation reported herein represents, not only an illustrative example of auto-tandem catalysis, but also an appealing alternative to the classical transition-metal catalyzed CC hydrogenations of allylic alcohols. The process has been successfully applied to aromatic as well as aliphatic substrates affording the corresponding saturated alcohols in 45-100% yields after 1.5-24 h. The best performances were reached using (i) 1-5 mol% of 1 or 2, 2-10 mol% of Cs2CO3, and propan-2-ol or (ii) 1-5 mol% of 1 or 2, 10-15 equivalents of NaO2CH, and water. The catalytic efficiency is strongly related to the structure of the allylic alcohol employed. Thus, in propan-2-ol, the reaction rate essentially depends on the steric requirement around the CC bond, therefore decreasing with the increasing number of substituents. On other hand, in water the transformation is favoured for primary allylic alcohols vs. secondary ones.
- Cadierno, Victorio,Crochet, Pascale,Francos, Javier,Garcia-Garrido, Sergio E.,Gimeno, Jose,Nebra, Noel
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scheme or table
p. 1992 - 2000
(2010/06/19)
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- Reusable gold(I) catalysts with unique regioselectivity for intermolecular hydroamination of alkynes
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Two gold(I) phosphine complexes bearing the low-coordinating bis(trifluoromethanesulfonyl)- imidate ligand, namely AuSPhosNTf2 and AuPPh3NTf2, are active catalysts for the regioselective intermolecular hydroamination of both internal and terminal alkynes under mild reaction conditions. The catalysts show a regioselectivity based on electronic rather than steric factors, which allow the preferential synthesis of regioisomers opposite to those described previously. This subtle chemo- and regiose-lectivity depends on the catalyst, substrates and reaction conditions employed, and allows one to perform new tandem reactions. These gold(I) complexes operate under free-solvent conditions, without exclusion of air, without addition of acidic promoters and can be quantitatively recovered and reused by simple precipitation in hexane.
- Leyva, Antonio,Corma, Avelino
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supporting information; experimental part
p. 2876 - 2886
(2010/03/25)
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- Oxidation of organic substrates using two triethylammonium halochromates(VI), (C2H5)3NH[CrO3X], (X=F, Cl) supported on silica gel
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Triethylammonium fluorochromate(VI), (C2H5) 3NHCrO3F, TriEAFC and triethylammonium chlorochromate(VI), (C2H5)3NHCrO3Cl, TriEACC were prepared, supported on silica gel and used to quantitatively oxidize a number of organic substrates. These supported triethylammonium halochromates are versatile reagents ensuring effective oxidation of organic compounds, in particular of alcohols, under mild conditions. The durability, ease of work up and efficiency of TriEAFC and TriEACC are considerably increased upon their absorption on silica gel.
- Ghammamy, Shahriare,Dastpeyman, Samaneh
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scheme or table
p. 229 - 232
(2009/04/06)
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- Microwave- and ultrasound-accelerated green oxidation of alcohols by potassium permanganate absorbed on copper(II) sulfate pentahydrate
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The solvent-free potassium permanganate (KMnO4)-promoted oxidation of alcohols into the corresponding carbonyl derivatives has been examined in detail with respect to the importance of supporting materials and supporting irradiation. Secondary alcohols are oxidized very efficiently to the corresponding ketones at ambient temperature by KMnO4 absorbed on a fourfold molar amount of copper(II) sulfate pentahydrate. The reaction is accelerated considerably by ultrasonic irradiation and drastically by microwave irradiation. Under the latter conditions, also hydroquinone can be converted 100% into p-benzoquinone within 4.5 min. Benzylic alcohols are oxidized most efficiently to the corresponding benzaldehydes under heterogeneous reaction conditions. Copyright Taylor & Francis Group, LLC.
- Luu, Thi Xuan Thi,Christensen, Peter,Duus, Fritz,Le, Thach Ngoc
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p. 2011 - 2024
(2008/09/21)
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