- Ruthenium complexes with dendritic ferrocenyl phosphanes: Synthesis, characterization, and application in the catalytic redox isomerization of allylic alcohols
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An efficient system for the catalytic redox isomerization of the allylic alcohol 1-octen-3-ol to 3-octanone is presented. The homogeneous ruthenium(II) catalyst contains a monodentate phosphane ligand with a ferrocene moiety in the backbone and provides 3-octanone in quantitative yields. The activity is increased by nearly 90 % with respect to the corresponding triphenyl phosphane ruthenium(II) complex. By grafting the catalyst at the surface of a dendrimer, the catalytic activity is further increased. By introducing different spacers between ferrocene and phosphorus, the influence on the electronic properties of the complexes is shown by evaluating the electrochemical behavior of the compounds.
- Neumann, Paul,Dib, Hanna,Sournia-Saquet, Alix,Grell, Toni,Handke, Marcel,Caminade, Anne-Marie,Hey-Hawkins, Evamarie
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- A tandem allylic alcohol isomerization-aldol condensation catalyzed by Rh and Ru complexes
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Allylic alcohols react with aldehydes, in an atom economy aldol-type reaction, in the presence of catalytic amounts of various rhodium and ruthenium complexes. This reaction occurs with total regiocontrol under mild conditions, but varying amounts of ketone derived from the competing isomerization reaction are also observed.
- Uma, Ramalinga,Davies, Maxwell,Crévisy, Christophe,Grée, René
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- Symmetric triazolylidene Ni(II) complexes applied as oxidation catalysts
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A set of related Ni(II) complexes of N-heterocyclic carbene ligands (NHC) [trans-X2Ni(NHC)2] (X = Cl, I) bearing linear straight chain alkyl wingtip substituents have been synthesised and fully characterised. Single crystal XRD data revealed symmetrically aligned Ni(II) centres within square planar coordination of trans halide, trans NHC ligands. The complexes were used for the catalytic oxidation of alkanes under mild conditions in conjunction with tert-butyl hydroperoxide as an oxidant. Under optimised reaction conditions, the catalytic results pointed to good activities of circa 15% and 19% for cyclohexane and n-octane respectively. Furthermore, the catalytic systems are shown to be very efficient for the oxidation of linear alcohols to corresponding ketones.
- Mncube, Siyabonga G.,Bala, Muhammad D.
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- Enzymatic hydrogenation of trans-2-nonenal in barley
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Conversion of undesirable, taste-active compounds is crucial for using barley as a suitable raw material for beer production. Here, ALH1, a barley alkenal hydrogenase enzyme that reduced the α,β-unsaturated double bond of aldehydes and ketones, was found to convert trans-2-nonenal (T2N), a major contributor to the cardboard-like flavor of aged beer. Although the physiological function of ALH1 in barley development remains elusive, it exhibited high specificity with NADPH as a cofactor in the conversion of several oxylipins-including T2N, trans-2-hexenal, traumatin, and 1-octen-3-one. ALH1 action represents a previously unknown mechanism for T2N conversion in barley. Additional experimental results resolved the genomic sequence for barley ALH1, as well as the identification of a paralog gene encoding ALH2. Interestingly, T2N was not converted by purified, recombinant ALH2. The possibility to enhance ALH1 activity in planta is discussed-not only with respect to the physiological consequences thereof-but also in relation to improved beer quality.
- Hambraeus, Gustav,Nyberg, Nils
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- Selective Synthesis of Alkynes by Catalytic Dehydrogenation of Alkenes over Polymer-supported Palladium Acetate in the Liquid Phase
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A heterogenized palladium acetate catalyst, in the presence of oxygen and perchloric acid in ethanol-water caused the direct conversion of terminal and internal monoalkenes into the corresponding alkynes, under mild conditions and in high yields; Wacker-type ketonization occurs with the same reagents in dioxane-water.
- Cum, Giampietro,Gallo, Raffaele,Ipsale, Salvatore,Spadaro, Agatino
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- Defect-Engineered Ruthenium MOFs as Versatile Heterogeneous Hydrogenation Catalysts
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Ruthenium MOF [Ru3(BTC)2Yy] ? Gg (BTC=benzene-1,3,5-tricarboxylate; Y=counter ions=Cl?, OH?, OAc?; G=guest molecules=HOAc, H2O) is modified via a mixed-linker approach, using mixtures of BTC and pyridine-3,5-dicarboxylate (PYDC) linkers, triggering structural defects at the distinct Ru2 paddlewheel (PW) nodes. This defect-engineering leads to enhanced catalytic properties due to the formation of partially reduced Ru2-nodes. Application of a hydrogen pre-treatment protocol to the Ru?MOFs, leads to a further boost in catalytic activity. We study the benefits of (1) defect engineering and (2) hydrogen pre-treatment on the catalytic activity of Ru?MOFs in the Meerwein-Ponndorf-Verley reaction and the isomerization of allylic alcohols to saturated ketones. Simple solvent washing could not avoid catalyst deactivation during recycling for the latter reaction, while hydrogen treatment prior to each catalytic run proved to facilitate materials recyclability with constant activity over five runs.
- Epp, Konstantin,Luz, Ignacio,Heinz, Werner R.,Rapeyko, Anastasia,Llabrés i Xamena, Francesc X.,Fischer, Roland A.
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- Arachidonic acid-dependent carbon-eight volatile synthesis from wounded liverwort (Marchantia polymorpha)
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Eight-carbon (C8) volatiles, such as 1-octen-3-ol, octan-3-one, and octan-3-ol, are ubiquitously found among fungi and bryophytes. In this study, it was found that the thalli of the common liverwort Marchantia polymorpha, a model plant species, emitted high amounts of C8 volatiles mainly consisting of (R)-1-octen-3-ol and octan-3-one upon mechanical wounding. The induction of emission took place within 40 min. In intact thalli, 1-octen-3-yl acetate was the predominant C8 volatile while tissue disruption resulted in conversion of the acetate to 1-octen-3-ol. This conversion was carried out by an esterase showing stereospecificity to (R)-1-octen-3-yl acetate. From the transgenic line of M. polymorpha (des6KO) lacking arachidonic acid and eicosapentaenoic acid, formation of C8 volatiles was only minimally observed, which indicated that arachidonic and/or eicosapentaenoic acids were essential to form C8 volatiles in M. polymorpha. When des6KO thalli were exposed to the vapor of 1-octen-3-ol, they absorbed the alcohol and converted it into 1-octen-3-yl acetate and octan-3-one. Therefore, this implied that 1-octen-3-ol was the primary C8 product formed from arachidonic acid, and further metabolism involving acetylation and oxidoreduction occurred to diversify the C8 products. Octan-3-one was only minimally formed from completely disrupted thalli, while it was formed as the most abundant product in partially disrupted thalli. Therefore, it is assumed that the remaining intact tissues were involved in the conversion of 1-octen-3-ol to octan-3-one in the partially disrupted thalli. The conversion was partly promoted by addition of NAD(P)H into the completely disrupted tissues, suggesting an NAD(P)H-dependent oxidoreductase was involved in the conversion.
- Kihara, Hirotomo,Tanaka, Maya,Yamato, Katsuyuki T.,Horibata, Akira,Yamada, Atsushi,Kita, Sayaka,Ishizaki, Kimitsune,Kajikawa, Masataka,Fukuzawa, Hideya,Kohchi, Takayuki,Akakabe, Yoshihiko,Matsui, Kenji
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- Base free transfer hydrogenation using a covalent triazine framework based catalyst
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Isomerisation of allylic alcohols to saturated ketones can be efficiently catalysed by a heterogeneous molecular system resulting from IrIIICp? anchoring to a covalent triazine framework. The obtained catalysts are active, selective, and fully recyclable.
- Bavykina,Mautscke,Makkee,Kapteijn,Gascon,Llabrési Xamena
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- Biocatalytic oxidative kinetic resolution of sec-alcohols: Stereocontrol through substrate-modification
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Whole lyophilised cells of Rhodococcus ruber DSM 44541 were employed for the oxidative kinetic resolution of sec-alcohols using acetone as hydrogen acceptor. The enantioselectivity of this process could be controlled effectively by introducing C-C multiple bonds into substrates, which were inefficiently recognised, in particular short-chain (ω-1)-alcohols and (ω-2)-analogs. Thus, the enantioselectivities of rac-2-pentanol (E=16.8) and rac-3-octanol (E=13.3) were significantly improved by introducing a C=C bond adjacent to the alcohol moiety to give racemic (E)-pent-3-en-2-ol and 4-(E)-octen-3-ol, which were resolved with excellent selectivities (E >100 and 50, respectively). In addition, it was found that high stereodifferentiation between the E- and Z-configured double bonds occurred, as the corresponding (Z)-isomers were not converted. Similar selectivity-enhancing effects were observed with acetylenic analogs.
- Stampfer, Wolfgang,Kosjek, Birgit,Faber, Kurt,Kroutil, Wolfgang
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- Development of new iron catalysts for the tandem isomerization-aldol condensation of allylic alcohols
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(bda)Fe(CO)3 and (COT)Fe(CO)3 are shown to be excellent catalysts for the tandem isomerization-aldol reaction of allylic alcohols with aldehydes and to significantly increase the scope of this aldolization process, especially, in the
- Uma, Ramalinga,Gouault, Nicolas,Crévisy, Christophe,Grée, René
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- Vanadium phosphorus oxide as an efficient catalyst for hydrocarbon oxidations using hydrogen peroxide
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Calcined vanadium phosphorus oxide (VPO) prepared by an organic route is found to be an active and effective catalyst for the oxidation of various alkanes such as cyclopentane, cyclohexane, n-hexane, cycloheptane, cyclooctane, cyclodecane and adamantane in acetonitrile solvent using the environmentally benign oxidant, hydrogen peroxide, where the oxidation mechanism is believed to involve a reversible V4+/V5+ redox cycle.
- Pillai, Unnikrishnan R.,Sahle-Demessie, Endalkachew
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- Number of terminal groups versus generation of the dendrimer, which criteria influence the catalytic properties?
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We report the synthesis of a dense dendrimer ended by the PTA ligand (1,3,5-triaza-7-phosphaadamantane), and the use of the corresponding Rh and Ru complexes for catalysis. The catalytic properties of these dendrimers are compared with those of two other dendrimers: a dendrimer of the same generation but having half the number of ligands, and a dendrimer of the next generation, but having the same number of ligands. The positive influence of the density of catalytic sites on the surface of these dendrimers for alcohol isomerization in water has been evidenced.
- Servin, Paul,Laurent, Régis,Dib, Hanna,Gonsalvi, Luca,Peruzzini, Maurizio,Majoral, Jean-Pierre,Caminade, Anne-Marie
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- μ-Chlorido-bridged dimanganese(II) complexes of the schiff base derived from [2+2] condensation of 2,6-diformyl-4-methylphenol and 1,3-bis(3- aminopropyl)tetramethyldisiloxane: Structure, magnetism, electrochemical behaviour, and catalytic oxidation of secondary alcohols
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The reaction of 2,6-diformyl-4-methylphenol with 1,3-bis(3-aminopropyl) tetramethyldisiloxane in the presence of MnCl2 in a 1:1:2 molar ratio in methanol afforded a dinuclear μ-chlorido-bridged manganese(II) complex of the macrocyclic [2+2] condensation product (H2L), namely, [Mn 2Cl2(H2L)(HL)]Cl·3H2O (1). The latter afforded a new compound, namely, [Mn2Cl2(H 2L)2][MnCl4]·4CH3CN·0. 5CHCl3·0.4H2O (2), after recrystallisation from 1:1 CHCl3/CH3CN. The co-existence of the free and complexed azomethine groups, phenolato donors, μ-chlorido bridges, and the disiloxane unit were well evidenced by ESI mass spectrometry and FTIR spectroscopy and confirmed by X-ray crystallography. The magnetic measurements revealed an antiferromagnetic interaction between the two high-spin (S = 5/2, g = 2) manganese(II) ions through the μ-chlorido bridging ligands. The electrochemical behaviour of 1 and 2 has been studied, and details of their redox properties are reported. Both compounds act as catalysts or catalyst precursors in the solvent-free low-power microwave-assisted oxidation of selected secondary alcohols, for example, 1-phenylethanol, cyclohexanol, 2- and 3-octanol, to the corresponding ketones in the absence of solvent. The highest yield of 72 % was achieved for 1-phenylethanol by using a maximum of 1 % molar ratio of catalyst relative to substrate. Copyright
- Alexandru, Mihaela,Cazacu, Maria,Arvinte, Adina,Shova, Sergiu,Turta, Constantin,Simionescu, Bogdan C.,Dobrov, Anatolie,Alegria, Elisabete C. B. A.,Martins, Luísa M. D. R. S.,Pombeiro, Armando J. L.,Arion, Vladimir B.
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- Liquid phase oxidation of n-octane to C8 oxygenates over modified Fe-MOF-5 catalysts
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The Metal Organic Framework materials Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 were prepared. The XRD results showed the expected pattern of MOF-5 with a very sharp peak at a 2θ value below 10° which indicate that the material is highly crystalline. The SEM and TEM images showed that the catalysts are cubic in shape. The synthesised Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 were tested in the oxidation of n-octane using H 2O2 as an oxidant in acetonitrile as solvent. Conversions of 10.5, 4.2 and 3.6% were obtained for Fe4-MOF-5, Fe 2-Zn2-MOF-5 and Fe0.9-Zn3. 1-MOF-5 respectively. It was observed that primary carbon activation increased with decreasing Fe content, as C-1 selectivities of 9.5, 12.9 and 19.8% were achieved for Fe4-MOF-5, Fe2-Zn 2-MOF-5 and Fe0.9-Zn3.1-MOF-5 respectively. Only C8 oxygenate products were observed, which include 1-octanol, 2-octanol, 3-octanol, 4-octanol, octanal, 2-octanone, 3-octanone, 4-octanone and octanoic acid. Furthermore, these catalysts were tested in the oxidation of cyclohexane using H2O2 in acetonitrile. Selectivities of 48.3% for cyclohexanol, 47.1% for cyclohexanone and 4.6% for hydroperoxycyclohexane were recorded at a conversion of 40% using Fe 4-MOF-5 as a catalyst.
- Cele, Mduduzi N.,Friedrich, Holger B.,Bala, Muhammad D.
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- Catalytic Double Bond Isomerization by Polystyrene-Anchored RuCl2(PPh3)3
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Dichlorotris(triphenylphosphine)ruthenium has been anchored to diphenylphosphinated styrene-divinylbenzene copolymer.The resulting leaching-resistant catalyst was employed successfully for the isomerization of allylbenzenes and allyl alcohols in numerous turnovers.The stability of the catalyst was examined in different media, and its performances were compared with those of homogeneous RuCl2(PPh3)3 and with those of polymer-bound as well as of free RhCl(PPh3)3 and IrCl(CO)(PPh3)2
- Zoran, Amikam,Sasson, Yoel,Blum, Jochanan
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- Copper oxide as efficient catalyst for oxidative dehydrogenation of alcohols with air
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The oxidative dehydrogenation of alcohols to carbonyl compounds was studied using CuO nanoparticle catalysts prepared by solution synthesis in buffered media. CuO nanoparticles synthesized in N-cyclohexyl-3-aminopropanesulfonic acid buffer showed high catalytic activity for the oxidation of benzylic, alicyclic and unsaturated alcohols to their corresponding carbonyl compounds with excellent selectivities. The observed trend in activity for conversion of substituted alcohols suggested a β-H elimination step to be involved, thus enabling a possible reaction mechanism for oxidative dehydrogenation of benzyl alcohols to be proposed. The use of CuO as an inexpensive and efficient heterogeneous catalyst under aerobic conditions provides a new noble metal-free and green reaction protocol for carbonyl compound synthesis. This journal is
- Poreddy, Raju,Engelbrekt, Christian,Riisager, Anders
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- Wacker-type oxidation of internal olefins using a PdCl2/N,N- dimethylacetamide catalyst system under copper-free reaction conditions
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(Figure Presented) A simple catalyst system consisting of PdCl2 and N,N-dimethylacetamide (DMA) as the solvent can successfully promote Wacker-type oxidation of internal olefins. This catalyst system does not require copper compounds and is tolerant of a wide range of substrates having internal olefins.
- Mitsudome, Takato,Mizumoto, Keiichi,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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- A Novel Oxidative Desulfonylation. Facile Conversion of Sulfones to Aldehydes or Ketones
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Alkyl, allylic, benzylic, and cycloalkyl sulfones can be converted to aldehydes or ketones in good-to-excellent yields by treatment with n-BuLi followed by Me3SiOOSiMe3.Preparation of 18O-labeled carbonyl compounds with Me3Si18O18OSiMe3 was also successful.
- Hwu, Jih Ru
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- Utilisation of new NiSNS pincer complexes in paraffin oxidation
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Two series of closely related SNS pincer ligands (L) were synthesised with the major structural variation on the nitrogen backbone containing either the methyl [L = (RSCH2CH2)2NMe: where R = Me (1), Et (2), Bu (3)] or the phenyl [L = (RSCH2CH2)2NPh: where R = Me (4), Et (5), Cy (6)] functional group. When ligands 1–3 were complexed to Ni by reaction with Ni(DME)Cl2 (DME = dimethoxyethane), they respectively yielded three new cationic dimeric [LNi(μ-Cl)3NiL]+ complexes (7–9), whilst ligands 4–6 on reaction with Ni(PPh3)2Br2 respectively yielded neutral mononuclear (LNiBr2) complexes 10–12. All the new compounds were characterised by IR, HRMS, elemental analysis and in addition, single crystal X-ray diffraction for complexes 9–12. X-ray structural data of 9 revealed an unusual three chlorido-bridged Ni dimer with the SNS ligand coordinated in a facial binding mode to the two pseudo-octahedral Ni centres. Molecular structures of complexes 10, 11 and 12 each displayed five-coordinate distorted trigonal bipyramidal geometry around the nickel(II) metal centres. When utilised as catalysts in the tert-butyl hydroperoxide oxidation of n-octane, all the complexes showed activity to mainly products of internal carbon activation (octanones and secondary octanols) with 11 as the most active (10% total substrate to oxygenates yield), whereas 10 was the least active, but most selective towards alcohols (alcohol/ketone = 2.13).
- Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.
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- Continuous-flow homogeneous catalysis using the temperature-controlled solvent properties of supercritical carbon dioxide
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A fully integrated continuous process for homogeneous catalysed reactions in scCO2 has been developed exploiting the tunable solvent properties of scCO2. A heated condenser situated above the reaction zone leads to a phase split under isobaric conditions resulting in efficient catalyst retention and recirculation. Continuous isomerisation of allylic alcohols was carried out for over 200 hours time-on-stream demonstrating the viability of this approach.
- Harwardt, Thomas,Francio, Giancarlo,Leitner, Walter
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- In Situ Spectroscopic Investigation of the Rhenium-Catalyzed Deoxydehydration of Vicinal Diols
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The mechanism of the CH3ReO3-catalyzed deoxydehydration of a vicinal diol to an alkene driven by oxidation of a secondary alcohol was investigated by time-resolved, in situ IR spectroscopy and was found to occur in three steps: 1) reduction of the catalytically active methyltrioxorhenium(VII) to a rhenium(V) complex (the rate-limiting step), 2) condensation of the diol and the rhenium(V) complex to a rhenium(V) diolate, and 3) extrusion of the alkene accompanied by oxidation of the Re center and thus regeneration of CH3ReO3. The reaction follows zero-order kinetics initially but, unexpectedly, accelerates towards the end, which is explained in terms of a deactivating pre-equilibrium, in which the catalytically active CH3ReO3 condenses reversibly with the diol to form an inactive rhenium(VII) diolate. This conclusion is supported by the direct observation of a catalytically inactive species as well as DFT calculations of the IR spectra of the relevant compounds.
- Dethlefsen, Johannes R.,Fristrup, Peter
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- Polystyrene-supported RhCl3-quaternary ammonium ion pair as a long-lived, efficient and recyclable catalyst
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Polymer-supported ion pair, generated from RhCl3 and Dowex(R) 1 anion exchanger was found to be a highly stable, efficient and recyclable catalyst for isomerization of allylic compounds, disproportionation of cyclic 1,3-dienes and trimerization of alkynes.
- Setty-Fichman, Merav,Blum, Jochanan,Sasson, Yoel,Eisen, Moris
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- A collaborative effect between gold and a support induces the selective oxidation of alcohols
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Ceria nanoparticles as a support stabilize positive gold species and provide oxygen vacancies. The resulting solid exhibits an exceedingly high efficiency for the solventless aerobic oxidation of primary and secondary alcohols to carbonyl compounds (see picture). (Chemical Equation Presented)
- Abad, Alberto,Concepcion, Patricia,Corma, Avelino,Garcia, Hermenegildo
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- Redox isomerization of allylic alcohols and amides using Grubbs' catalyst
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Commercially available Grubbs' catalyst was found to catalyze the redox isomerization of allylic alcohols and amides under mild conditions.
- Greenwood,Parsons,Young
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- Aerobic oxidation of primary aliphatic alcohols to aldehydes catalyzed by a palladium(II) polyoxometalate catalyst
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A hexadecyltrimethylammonium salt of a "sandwich" type polyoxometalate has been used as a ligand to attach a palladium(II) center. This Pd-POM compound was an active catalyst for the fast aerobic oxidation of alcohols. The unique property of this catalyst is its significant preference for the oxidation of primary versus secondary aliphatic alcohols. Since no kinetic isotope effect was observed for the dehydrogenation step, this may be the result of the intrinsically higher probability for oxidation of primary alcohols attenuated by steric factors as borne out by the higher reactivity of 1-octanol versus 2-ethyl-1-hexanol. The reaction is highly selective to aldehyde with little formation of carboxylic acid; autooxidation is inhibited. No base is required to activate the alcohol. The fast reactions appear to be related to the electron-acceptor nature of the polyoxometalate ligand that may also facilitate alcohol dehydrogenation in the absence of base.
- Barats, Delina,Neumann, Ronny
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- Synthesis and Occurrence of Oxoaldehydes in Used Frying Oils
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As part of our efforts to identify volatile decomposition products in used frying oils, a series of 4- and 5-oxoaldehydes were synthesized, purified, and characterized by gas chromatography, gas chromatography-mass spectrometry, gas-chromatography-Fourier transform infrared spectrometry, and nuclear magnetic resonance spectrometry.Oxoaldehydes have been proposed as possible precursors of alkylfurans, which have potential anticancer effects.In a model reaction 4-oxononanal was refluxed in hexane for 40 days and only trace amounts of 2-pentylfuran were produced, suggesting that it is not a major precursor of the furan.The volatile constituents of used frying oils obtained from commercial food processors were studied, and 4-oxohexanal, 4-oxooctanal, 4-oxononanal, and 4-oxodecanal were identified.Keywords: Oxoaldehydes; odor threshold; frying oil
- Takeoka, Gary R.,Buttery, Ron G.,Perrino, Charles T.
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- Studies on the Catalytic Oxidation of Alkanes and Alkenes by Titanium Silicates
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Titanium containing, aluminum-free ZSM-5 (TS-1) and amorphous TiO2-SiO2 coprecipitate are investigated as catalysts for the selective oxidation of alkanes and alkenes using a variety of oxidants at temperatures below 100 deg C. Comparisons between the activities of TS-1 and the TiO2-SiO2 coprecipitate for alkane oxidation and alkene epoxidation using nonaqueous H2O2 indicate that the absence of water is crucial for the catalytic activity of silica-supported titanium. Due to the hydrophobicity of TS-1, the concentration of water surrounding the titanium is maintained at a low value, and thus TS-1 can be used as an oxidation catalyst with aqueous H2O2 as oxidant. Alkyl hydroperoxides are active as oxidants for alkene epoxidation on the TiO2-SiO2 coprecipitate but not for alkane oxidation reactions on both TS-1 and the TiO2-SiO2 coprecipitate. A plausible explanation for the above results is provided. The presence of stereoscrambling without any "radical clock" rearrangement during alkane oxidation on TS-1 indicates that the radicals formed may have a very short life-time, or their movements are restricted such that no rearrangement can occur. A proposal for the mechanism of alkane oxidation on TS-1 is given and compared to a mechanism suggested for alkene epoxidation on TS-1 and the TiO2-SiO2 coprecipitate.
- Khouw, C. B.,Dartt, C. B.,Labinger, J. A.,Davis, M. E.
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- Atmospheric hydrogenation of Α Β-unsaturated ketones catalyzed by highly efficient and recyclable Pd nanocatalyst
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A thermoregulated phase-transfer Pd nanocatalyst was explored firstly and shown to be highly efficient and recyclable in the atmospheric hydrogenation of α β-unsaturated ketones. Under optimized reaction conditions, the conversion of chalcone and the selectivity of dihydrochalcone were 99% and 98%, respectively. The catalyst can be easily separated from the product and used directly for four times without evident loss in activity and selectivity. The turnover frequency (TOF) for the atmospheric hydrogenation of chalcone was 870 h?1, which to the best of our knowledge was the highest value ever reported among transition metal nanocatalysts.
- Chen, Pu,Li, Wenjiang,Wang, Yanhua
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- Catalytic transformation of aliphatic alcohols to corresponding esters in o2 under neutral conditions using visible-light irradiation
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Selective oxidation of aliphatic alcohols under mild and base-free conditions is a challenging process for organic synthesis. Herein, we report a one-pot process for the direct oxidative esterification of aliphatic alcohols that is significantly enhanced by visible-light irradiation at ambient temperatures. The new methodology uses heterogenerous photocatalysts of gold-palladium alloy nanoparticles on a phosphate-modified hydrotalcite support and molecular oxygen as a benign oxidant. The alloy photocatalysts can absorb incident light, and the light-excited metal electrons on the surface of metal nanoparticles can activate the adsorbed reactant molecules. Tuning the light intensity and wavelength of the irradiation can remarkably change the reaction activity. Shorter wavelength light (550 nm) drives the reaction more efficiently than light of longer wavelength (e.g., 620 nm), especially at low temperatures. The phosphate-exchanged hydrotalcite support provides sufficient basicity (and buffer) for the catalytic reactions; thus, the addition of base is not required. The photocatalysts are efficient and readily recyclable. The findings reveal the first example of using "green" oxidants and light energy to drive direct oxidative esterification of aliphatic alcohols under base-free, mild conditions.
- Xiao, Qi,Liu, Zhe,Bo, Arixin,Zavahir, Sifani,Sarina, Sarina,Bottle, Steven,Riches, James D.,Zhu, Huaiyong
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- Microsome-bound alcohol oxidase catalyzed production of carbonyl compounds from alcohol substrates
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High yield conversion of a wide range of alcohol substrates to their corresponding aldehydes was demonstrated using a microsomal alcohol oxidase (AOx) from Aspergillus terreus. The microsome bound AOx preparation was then immobilized into polyurethane foam matrix following a simple adsorption technique. The successful immobilization of the enzyme into the foam matrix was demonstrated microscopically and by biological staining. The enzyme loading was measured as ~2.02 U mg-1 (76.6 mg protein %) of polyurethane foam. The optimum activity of the immobilized enzyme was detected in the pH range 7.0-8.0. The catalytic activity of the immobilized AOx was utilized for the production of n-heptanal. A maximum n-heptanal yield of 20.7 ± 1.2% (w/w) was achieved at a substrate concentration of 10 mM n-heptanol; beyond this concentration substrate dependent inhibition of the catalytic reaction was observed. The operational stability of the immobilized enzyme was determined and found to be ~60% of the initial activity till the fifth reaction cycle, thus providing high cumulative yield of the product. The deactivation (k d) and half-life time (t1/2) of the immobilized enzyme were 5.17 × 10-5 min-1 and ~9 days, respectively. The results demonstrated the potential application of the polyurethane foam immobilized microsomal AOx-based environmentally benign biocatalytic process for the production of industrially important n-heptanal.
- Kakoti, Ankana,Kumar, Adepu Kiran,Goswami, Pranab
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- Efficient isomerization of allylic alcohols to saturated carbonyl compounds by activated rhodium and ruthenium complexes
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A range of readily available rhodium complexes of the general structures Rh(PPh3)3+ PF6- and RhX(PPh3)3 (X = H, Me, Ph) have been prepared and used in situ for the isomerization of allylic alcohols to their corresponding saturated carbonyl compounds. The isomerization of octen-3-ol, selected as a model, yielded octan-3-one in good yield. This reaction has been extended to the corresponding ruthenium complexes of the general structures [RuCl(PPh3)3]+ PF6-, RuXCl(PPh3)3 and RuX2(PPh3)3 (X = H, Me, Ph). It is noteworthy that many of these complexes have not been employed previously for this isomerization. The scope and efficiency of the process has been demonstrated by four representative complexes [RhH(PPh3)3, RuH2(PPh3)3, RuPh2(PPh3)3, RuCl(PPh3)3+ PF6-] with a wide variety of allylic alcohols. The reaction of primary allylic alcohols in the presence of RuCl(PPh3)3+ PF6- in methanol yields aldehydes protected as their methyl acetals. Deuterium labelling experiments are in agreement with a 1,3-hydride shift mechanism.
- Uma, Ramalinga,Davies, Maxwell K.,Crevisy, Christophe,Gree, Rene
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- Gold nanoparticles onto cerium oxycarbonate as highly efficient catalyst for aerobic allyl alcohol oxidation
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Au nanoparticles, generated by the metal vapor synthesis technique, were supported onto cerium oxycarbonate monohydrate (Ce2O(CO3)2·H2O) giving Au@Ce2O(CO3)2·H2O. The obtained heterogeneous catalyst was used in the aerobic allyl alcohol oxidation reaction performed in toluene, showing a notably higher catalytic substrate conversion and isomerization activity compared to Au onto ceria, which is the reference catalyst for this type of catalysis. Results originating from catalytic recycling experiments and PXRD, HRTEM and XPS measurements carried out on recovered Au@Ce2O(CO3)2·H2O, confirmed the stability of the catalyst under aerobic oxidation reaction conditions and hence its recyclability, without the need of a regeneration step.
- Oberhauser, Werner,Evangelisti, Claudio,Marelli, Marcello,Santo, Vladimiro Dal,Cepek, Cinzia,Bellini, Marco
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- Flexible SNS pincer complexes of copper: Synthesis, structural characterisation and application in n-octane oxidation
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Two new tridentate SNS ligands based on a flexible, straight chain amine backbone were prepared and in combination with three related but previously reported ligands were reacted with CuCl2 to yield new tridentate pincer-type copper(II) complexes. The molecular structures of the new ligands bis(cyclohexylthioethyl)methylamine (L1d), bis(t-butylthioethyl)methylamine (L1e), and all the complexes Cu[bis(Rthioethyl)methylamine]Cl2 (1) where R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e); were confirmed by a range of spectroscopic and analytical techniques. Single crystal X-ray diffraction analysis determined the solid-state structures of the salt of L1e and the complexes. Complexes 1a-e all exhibited five-coordinate ligand geometry around each Cu(II) centre defined by the tridentate SNS and two chlorido donors. The complexes were applied as catalysts in the oxidation of n-octane using t-butyl hydroperoxide and hydrogen peroxide (H2O2) as oxidants. The H2O2 based systems yielded up to 36% conversion of n-octane to C-8 oxygenates with very high alcohol selectivity of up to 78%.
- Soobramoney, Lynette,Bala, Muhammad D.,Friedrich, Holger B.,Pillay, Michael N.
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- New Polymer Colloidal and Carbon Nanospheres: Stabilizing Ultrasmall Metal Nanoparticles for Solvent-Free Catalysis
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Herein, we report the synthesis of new colloidal polydiaminopyridine (PDAP) nanospheres with uniform particle size tuned from 76 to 331 nm. The polymer colloidal nanospheres and thin films assembled by the nanospheres exhibit amphiphilic or superhydrophilic properties, originated from the different polymer surfactants. In addition, the polymer nanospheres can be easily carbonized into microporous carbon nanospheres with high N content up to 24 wt %, thus enabling a preferred basicity for CO2 adsorption. As-synthesized PDAP show good compatibility that can not only encapsulate typical nanoparticles to form core-shell composite nanospheres but also stabilize noble metal ions to obtain ultrasmall metal nanoparticles (e.g., Pd and Au) during the thermal reduction process by the nitrogen sites from sphere frameworks. The nanocomplex Pd/PDAP-500 shows exceptional activity and high selectivity in the solvent-free oxidation of alcohols with O2.
- Wang, Tao,Zhang, Pengfei,Sun, Yan,Liu, Bing,Liu, Yunling,Qiao, Zhen-An,Huo, Qisheng,Dai, Sheng
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- Oxidation of Alkanes by Periodate Using a MnV Nitrido Complex as Catalyst
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The design of catalytic systems that can selectively oxidize unactivated C?H bonds under mild conditions is a challenge to chemists. We report here that the manganese(V) nitrido complex [MnV(N)(CN)4]2? is a highly efficient catalyst for the oxidation of alkanes by periodate (IO4 ?) at ambient conditions. Excellent yields of alcohols and ketones (>95 %) are obtained with a maximum turnover number (TON) of 3000.
- Ma, Li,Chen, Lingjing,Lau, Tai-Chu
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- Reactivity of the Dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (C10H16 = 2,7-Dimethylocta-2,6-diene-1,8-diyl) toward Guanidines: Access to Ruthenium(IV) and Ruthenium(II) Guanidinate Complexes
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The novel bis(allyl)ruthenium(IV) guanidinate complexes [RuCl{κ2(N,N′)-C(NR)(NiPr)-NHiPr}(η3:η3-C10H16)] (C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl; R = Ph (3a), 4-C6H4F (3b), 4-C6H4Cl (3c), 4-C6H4Me (3d), 3-C6H4Me (3e) 4-C6H4tBu (3f)) have been synthesized by treatment of the dimeric precursor [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (1) with 4 equiv of the corresponding guanidine (iPrHN)2C=NR (2a-f). The easily separable guanidinium chloride salts [(iPrHN)2C(NHR)][Cl] (4a-f) are also formed in these reactions. Attempts to generate analogous Ru(IV) guanidinate complexes from (iPrHN)2C=NR (R = 2-C6H4Me (2g), 2,4,6-C6H2Me3 (2h), 2,6-C6H3iPr2 (2i)) failed, due probably to the steric hindrance associated with the aryl group in these guanidines. On the other hand, the reaction of the dimer [{RuCl(μ-Cl)(η3:η3-C10H16)}2] (1) with (iPrHN)2C=N-4-C6H4C≡N (2j) led to the selective formation of the mononuclear derivative [RuCl2(η3:η3-C10H16){N≡C-4-C6H4-N=C(NHiPr2)2}] (5), in which the guanidine coordinates to ruthenium through the pendant nitrile unit. This result contrasts with that obtained by employing the related Ru(II) dimer [{RuCl(μ-Cl)(η6-p-cymene)}2] (6), whose reaction with 2j afforded the expected guanidinate complex [RuCl{κ2(N,N′)-C(N-4-C6H4C≡N)(NiPr)-NHiPr}(η6-p-cymene)] (7). Treatment of 7 with dimer 1 yielded the dinuclear Ru(II)/Ru(IV) derivative 8, via cleavage of the chloride bridges of 1 by the C≡N group of 7. Reductive elimination of the 2,7-dimethylocta-2,6-diene-1,8-diyl chain in [RuCl{κ2(N,N′)-C(NR)(NiPr)-NHiPr}(η3:η3-C10H16)] (3a-f) readily took place in the presence of an excess of 2,6-dimethylphenyl isocyanide, thus allowing the high-yield preparation of the octahedral ruthenium(II) compounds mer-[RuCl{κ2(N,N′)-C(NR)(NiPr)-NHiPr}(CN-2,6-C6H3Me2)3] (9a-f). The structures of [RuCl{κ2(N,N′)-C(N-4-C6H4Me)(NiPr)-NHiPr}(η3:η3-C10H16)] (3d), [RuCl{κ2(N,N′)-C(N-4-C6H4C≡N)(NiPr)-NHiPr}(η6-p-cymene)] (7), and mer-[RuCl{κ2(N,N′)-C(N-4-C6H4tBu)(NiPr)-NHiPr}(CN-2,6-C6H3Me2)3] (9f), as well as those of the guanidinium chloride salts 4a-c, were unequivocally confirmed by X-ray diffraction methods. In addition, the catalytic behavior of the guanidinate complexes 3a-f and 9a-f in the redox isomerization of allylic alcohols was also explored.
- Menéndez-Rodríguez, Lucía,Tomás-Mendivil, Eder,Francos, Javier,Crochet, Pascale,Cadierno, Victorio,Anti?olo, Antonio,Fernández-Galán, Rafael,Carrillo-Hermosilla, Fernando
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- Redox control of a dendritic ferrocenyl-based homogeneous catalyst
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The application of a dendrimer in a redox-switchable catalytic process is reported. A monomeric and the corresponding dendritic ferrocenylphosphane ligand were used to develop well-defined controllable catalysts with distinct redox states. The corresponding ruthenium(II) complexes catalyze the isomerization of the allylic alcohol 1-octen-3-ol. By adding a chemical oxidant or reductant, it was possible to reversibly switch the catalytic activity of the complexes. On oxidation, the ferrocenium moiety withdraws electron density from the phosphane, thereby lowering its basicity. The resulting electron-poor ruthenium center shows much lower activity for the redox isomerization and the reaction rate is markedly reduced.
- Neumann, Paul,Hey-Hawkins, Evamarie,Dib, Hanna,Caminade, Anne-Marie
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- Effect of the functionalisation route on a Zr-MOF with an Ir-NHC complex for catalysis
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A new iridium N-heterocyclic carbene (NHC) metallolinker has been synthesised and introduced into a metal-organic framework (MOF), for the first time, via two different routes: direct synthesis and postsynthetic exchange (PSE). The two materials were compared in terms of the Ir loading and distribution using X-ray energy dispersive spectroscopy (EDS), the local Ir structure using X-ray absorption spectroscopy (XAS) and the catalytic activity. The materials showed good activity and recyclability as catalysts for the isomerisation of an allylic alcohol.
- Carson, Fabian,Martínez-Castro, Elisa,Marcos, Rocío,Miera, Greco González,Jansson, Kjell,Zou, Xiaodong,Martín-Matute, Belén
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- Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
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A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
- Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
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- Synthesis and characterization of Co3O4 immobilized on dipeptide-functionalized silica-coated magnetite nanoparticles as a catalyst for the selective aerobic oxidation of alcohols
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Synthesis and characterization of a new silica-coated magnetite nanocatalyst are described. This catalyst was prepared through a multistep procedure consisting of surface modification, functionalization with the product of an Ugi multicomponent reaction, and immobilization of Co3O4 on silica-coated magnetite nanoparticles. The prepared nanocatalyst was characterized using various techniques such as Fourier-transform infrared and energy-dispersive X-ray spectroscopies, thermal and elemental analyses, X-ray diffraction, and field-emission scanning and transmission electron microscopies. The catalyst showed high catalytic activity for the aerobic oxidation of alcohols in acetonitrile as the solvent at mild temperatures and reusability for five repeated runs without loss of its activity.
- Khodaei, Mohammad Mehdi,Dehghan, Mahsa
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- Commercial Gold(I) and Gold(III) Compounds Supported on Carbon Materials as Greener Catalysts for the Oxidation of Alkanes and Alcohols
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Strategies are presented for single-pot efficient oxidative functionalization of cyclohexane and alcohols, under mild conditions, catalysed by Au(I) or Au(III) compounds supported on different carbon materials with three different surface treatments. The obtained materials were tested for the oxidation of cyclohexane under mild conditions (room temperature and atmospheric pressure), using an environmentally friendly oxidant (tert-butyl hydroperoxide, TBHP, 70 % aqueous solution). All materials were very selective to the production of cyclohexanol and cyclohexanone with no trace of by-products detected. The catalysts were also tested in the selective oxidation of methyl benzyl alcohol, cyclohexanol, and 2-octanol with TBHP, under microwave irradiation, to the corresponding aldehydes or ketones. In general, better results are obtained for the heterogenised complexes and that the most efficient support is CNT-ox-Na. This is the first report on the oxidation of C?H bonds using the mononuclear gold complexes used; only the oxidation of unsaturated units had been reported previously. The sp3-C?H activation is much more difficult than the oxidation of unsaturated molecules with molecular oxidants.
- Carabineiro, Sónia A. C.,Martins, Luísa M. D. R. S.,Pombeiro, Armando J. L.,Figueiredo, José L.
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- Oxygen transfer from sulfoxides: Selective oxidation of alcohols catalyzed by polyoxomolybdates
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Benzylic, allylic, and aliphatic alcohols are oxidized to aldehydes and ketones in a reaction catalyzed by Keggin-type polyoxomolybdates, PVxMo(12-x)O40-(3+x) (x = 0, 2), with DMSO as a solvent. The oxidation of benzylic alcohols is quantitative within hours and selective, whereas that of allylic alcohols is less selective. Oxidation of aliphatic alcohols is slower but selective. Further mechanistic studies revealed that, for H3PMo12O40 as a catalyst and benzylic alcohols as substrates, the sulfoxide is in fact an oxygen donor in the reaction. Postulated reaction steps as determined from isotopelabeling experiments, kinetic isotope effects, and Hammett plots include (a) sulfoxide activation by complexation to the polyoxometalate and (b) oxygen transfer from the activated sulfoxide and elimination of water from the alcohol. The mechanism is supported by the reaction kinetics.
- Khenkin, Alexander M.,Neumann, Ronny
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- From DNA to catalysis: A thymine-acetate ligated non-heme iron(III) catalyst for oxidative activation of aliphatic C-H bonds
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A non-heme, iron(iii)/THA(thymine-1-acetate) catalyst together with H2O2 as an oxidant is efficient in oxidative C-H activation of alkanes. Although having a higher preference for tertiary C-H bonds, the catalyst also oxidizes aliphatic secondary C-H bonds into carbonyl compounds with good to excellent conversions. Based on the site selectivity of the catalyst and our mechanistic studies the reaction proceeds via an Fe-oxo species without long lived carbon centered radicals.
- Al-Hunaiti, Afnan,R?is?nen, Minn?,Repo, Timo
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- A convenient synthesis of a porphyrin cross-linked polymer, its application as a size selective heterogeneous catalyst and a comparison with a porphyrin-cored hyperbranched polymer
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This paper describes how the polymeric structure and environment surrounding supported catalysts can be used to affect the product outcome from a reaction. As well as reporting a size/shape selectivity, we also describe a significant effect on product distribution. Specifically, how the polymeric environment can favour or disfavour particular products. As such, these results illustrate how it may be possible to target more or less of a specific compound (from a possible mix) by careful choice of the polymer architecture surrounding a catalyst.
- Twyman, Lance J.,Zheng, Xinwei
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- Coordination chemistry and catalytic applications of Pd(II)–, and Ni(II)–sulfosalan complexes in aqueous media
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With the aim of identifying new types of water-soluble catalyst precursors for modification of biological membranes by homogeneous hydrogenation in aqueous solution and under mild conditions, we have performed detailed equilibrium and spectroscopic charac
- Lihi, Norbert,Bunda, Szilvia,Udvardy, Antal,Joó, Ferenc
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- Thermoregulated phase-transfer iridium nanoparticle catalyst: Highly selective hydrogenation of the CO bond for α,β-unsaturated aldehydes and the CC bond for α,β-unsaturated ketones
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In the same catalytic system, thermoregulated ligand Ph2P(CH2CH2O)22CH3-stabilized iridium nanoparticles exhibited a totally different orientation for the hydrogenation of unsaturated carbonyl compounds, namely, highly selective hydrogenation of the CO bond for α,β-unsaturated aldehydes and the CC bond for α,β-unsaturated ketones.
- Li, Wenjiang,Wang, Yanhua,Chen, Pu,Zeng, Min,Jiang, Jingyang,Jin, Zilin
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- Catalytic redox isomerization of allylic alcohols with rhodium and iridium complexes with ferrocene phosphine-thioether ligands
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Complexes [M(P,SR)(diene)X] where (P,SR) = CpFe[1,2-C5H3(PPh2)(CH2SR)] (M = Ir, R = tBu or Bn diene = cod, X = Cl; M = Rh, diene = cod or nbd; X = BF4 or Cl) were used as precatalysts for the redox isomerization of various allylic alcohols (7a–e) to the corresponding saturated ketones (8a–e) and or hydrogenation to the saturated alcohol (9a–e). In optimization studies using 1-phenyl-2-propen-1-ol (7a) in THF and in iPrOH/MeONa, the only observed product was the saturated alcohol 1-phenyl-1-propanol (9a) when working under a 30 bar H2 pressure, but activation for only 1 min under H2 pressure and then continuation under 1 bar of H2 or Ar led to increasing amounts of the allylic isomerization product propiophenone (8a). Continued reaction under H2 converted (8a) into (9a). The Rh precatalysts were more active than the Ir analogues. For the rhodium precatalysts (3) and (4), the redox isomerization reaction could be carried out after precatalyst activation in iPrOH/MeONa under Ar at 82 °C (without H2) with complete conversion in 1 h (1% catalyst loading). However, longer reaction times resulted in slow transfer hydrogenation of (8a) leading to (9a) with low enantiomeric excess. Extension of the H2-free activation of the Rh precatalysts in iPrOH to other allylic alcohol substrates (7b–d) yielded the corresponding ketones with good to excellent yields and excellent chemoselectivities under appropriate conditions.
- Titova, Ekaterina M.,Rahaman, S.M. Wahidur,Shubina, Elena S.,Poli, Rinaldo,Belkova, Natalia V.,Manoury, Eric
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- The effects of metals and ligands on the oxidation of n-octane using iridium and rhodium “PNP” aminodiphosphine complexes
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Ir and Rh “PNP” complexes with different ligands are utilized for the oxidation of n-octane. Based on the obtained conversion, selectivity, and the characterized recovered catalysts, it is found that the combination of Ir and the studied ligands does not promote the redox mechanism that is known to result in selective formation of oxo and peroxo compounds [desired species for C(1) activation]. Instead, they support a deeper oxidation mechanism, and thus higher selectivity for ketones and acids is obtained. In contrast, these ligands seem to tune the electron density around the Rh (in the Rh-PNP complexes), and thus result in a higher n-octane conversion and improved selectivity for the C(1) activated products, with minimized deeper oxidation, in comparison to Ir-PNP catalysts.
- Naicker, Dunesha,Alapour, Saba,Friedrich, Holger B
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p. 282 - 289
(2020/12/01)
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- Flexible pincer backbone revisited: CuSNS complexes as efficient catalysts in paraffin oxidation
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New Cu(II) complexes containing a set of tridentate hybrid SNS ligands were synthesised and fully characterised by IR, HRMS, elemental analysis and single-crystal X-ray diffraction. The complexes with the general formula Cu[bis(Rthioethyl)phenylamine]Cl2 (1); [R = methyl (a); ethyl (b); butyl (c); cyclohexyl (d) and t-butyl (e)] exhibited five-coordinate trigonal bipyramidal geometry around each Cu(II) centre in the solid-state with the S-donor atoms occupying the axial positions. However, complex 1b crystallised as a dimer bridged through a cuprate anion denoted as [1b(μ-CuCl4)1b]. Their application as catalysts in the oxidation of n-octane with hydrogen peroxide (H2O2) as an oxidant gave high substrate conversions to C-8 oxygenate products, mainly octanols, after reduction with PPh3. Notably, complex 1d produced the highest yield of 57% in 1 h reaction time at a catalyst concentration of 1 mol%. In general, high turnover numbers (2830–3180) were recorded for the 1/H2O2 catalytic systems with substantially high combined selectivity of 22–27% to 1-octanol and octanoic acid, which are the more desired products of n-octane oxidation resulting from its terminal carbon (C(1)) activation. The high activity of the catalysts is attributed to metal–ligand cooperative catalysis involving CuII-OOH intermediates as the active species modulated by the tridentate SNS ligands. In comparison with related complexes bearing N-donor atoms, the excellent catalytic performance of these series of CuSNS complexes highlights the critical role of the phenylamine N-donor atom.
- Bala, Muhammad D.,Friedrich, Holger B.,Soobramoney, Lynette
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supporting information
(2021/07/16)
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- Expanding the Biocatalytic Toolbox with a New Type of ene/yne-Reductase from Cyclocybe aegerita
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This study introduces a new type of ene/yne-reductase from Cyclocybe aegerita with a broad substrate scope including aliphatic and aromatic alkenes/alkynes from which aliphatic C8-alkenones, C8-alkenals and aromatic nitroalkenes were the preferred substrates. By comparing alkenes and alkynes, a ~2-fold lower conversion towards alkynes was observed. Furthermore, it could be shown that the alkyne reduction proceeds via a slow reduction of the alkyne to the alkene followed by a rapid reduction to the corresponding alkane. An accumulation of the alkene was not observed. Moreover, a regioselective reduction of the double bond in α,β-position of α,β,γ,δ-unsaturated alkenals took place. This as well as the first biocatalytic reduction of different aliphatic and aromatic alkynes to alkanes underlines the novelty of this biocatalyst. Thus with this study on the new ene-reductase CaeEnR1, a promising substrate scope is disclosed that describes conceivably a broad occurrence of such reactions within the chemical landscape.
- Karrer, Dominik,Gand, Martin,Rühl, Martin
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p. 2191 - 2199
(2021/02/26)
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- Oxidation of Alkenes by Water with H2 Liberation
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Oxidation by water with H2 liberation is highly desirable, as it can serve as an environmentally friendly way for the oxidation of organic compounds. Herein, we report the oxidation of alkenes with water as the oxidant by using a catalyst combination of a dearomatized acridine-based PNP-Ru complex and indium(III) triflate. Compared to traditional Wacker-type oxidation, this transformation avoids the use of added chemical oxidants and liberates hydrogen gas as the only byproduct.
- Ben-David, Yehoshoa,Milstein, David,Tang, Shan
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supporting information
p. 5980 - 5984
(2020/04/27)
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- Regioselective Wacker-Type Oxidation of Internal Olefins in tBuOH Using Oxygen as the Sole Oxidant and tBuONO as the Organic Redox Cocatalyst
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A regioselective Wacker-Tsuji oxidation of internal olefins in tBuOH has been developed using oxygen as the terminal oxidant and tert-butyl nitrite as the simple organic redox cocatalyst without the involvement of hazardous cocatalysts or harsh reaction conditions. A series of internal olefins bearing various functional groups can be oxidized to the corresponding substituted ketones in generally good yields with high regioselectivities.
- Huang, Qing,Li, Ya-Wei,Ning, Xiao-Shan,Jiang, Guo-Qing,Zhang, Xiao-Wei,Qu, Jian-Ping,Kang, Yan-Biao
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supporting information
p. 965 - 969
(2020/02/15)
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- Application of new Ru (II) pyridine-based complexes in the partial oxidation of n-octane
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Tridentate and bidentate Ru (II) complexes were prepared through reaction of four pyridine-based ligands: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} with the [(η6-C6H6)Ru(μ-Cl)Cl]2 dimer. Crystal structures of the new terdentate Ru (II) complexes [Ru{pyCH2N(R)CH2py}C6H6](PF6)2 (R = C3H7 (1), C (CH3)3 (2), C6H11 (3) and the bidentate Ru (II) complex [Ru{pyCH2N(R)}C6H6]PF6 (R = C6H5 (4)) are reported. It was found that complexes 1, 2, 3 and 4 crystallised as mono-metallic species, with a piano stool geometry around each Ru centre. All complexes were active in the selective oxidation of n-octane using t-BuOOH and H2O2 as oxidants. Complexes 2 and 4 reached a product yield of 12% with t-BuOOH as oxidant, however, superior yields (23–32%) were achieved using H2O2 over all systems. The selectivity was predominantly towards alcohols (particularly 2-octanol) over all complexes using t-BuOOH and H2O2 after reduction of the formed alkylhydroperoxides in solution by PPh3. High TONs of up to 2400 were achieved over the Ru/H2O2 systems.
- Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
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- A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for aerobic oxidation of alcohols
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A sodium trifluoromethanesulfinate-mediated photocatalytic strategy for the aerobic oxidation of alcohols has been developed for the first time, and the photoredox aerobic oxidation of secondary and primary alcohols provided the corresponding ketones and carboxylic acids, respectively, in high to excellent yields.
- Zhu, Xianjin,Liu, Can,Liu, Yong,Yang, Haijun,Fu, Hua
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p. 12443 - 12446
(2020/10/30)
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- Synthesis of Co(II) NNN-pyridine based complexes and their activity in the partial oxidation of n-octane
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A series of four NNN-pyridine based ligands of the general form: pyCH2N(R)CH2py {R = propyl, tert-butyl, cyclohexyl and phenyl; py = pyridine} were synthesised and characterised. Complexation of each ligand to CoCl2?6H2O afforded new Co(II) complexes [Co{pyCH2N(R)CH2py}Cl2] (R = C3H7 (1), C(CH3)3 (2), C6H11 (3) and C6H5 (4)). Single crystal X-ray diffraction data confirmed that complex 1 crystallised as a mononuclear unit and was characterised by a distorted trigonal bipyramidal arrangement of ligands around Co. As catalysts in the oxidation of n-octane using t-BuOOH as oxidant, 2 (10% product yield) was found to be most efficient and the selectivity over 1–4 was predominantly towards 2-octanol, after reduction of alkylhydroperoxides by PPh3. All catalysts were significantly more active in the activation of n-octane using hydrogen peroxide, with a yield of 45% observed over catalyst 3. Furthermore, with H2O2, all catalysts produced a high concentration of alkylhydroperoxides, with catalyst 4 giving up to 91% alcohols after workup. TONs of up to 1100 were achieved over the Co/H2O2 systems.
- Chanerika, Revana,Friedrich, Holger B.,Shozi, Mzamo L.
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- Divergent Multistep Continuous Synthetic Transformations of Allylic Alcohol Enabled by Catalysts Immobilized in Ionic Liquid Phases.
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Two individual catalytic platforms (metal- and organo-catalyzed) based on the use of an ionic liquid phase were successfully integrated for the synthesis of α-cyano-amine and cyanohydrin trimethylsilyl ethers from allylic alcohol. The right combination of continuous flow processes enabled access to the divergent preparation of two alternative and interesting intermediate compounds from the same starting material.
- Peris, Edgar,Porcar, Raúl,García-álvarez, Joaquín,Burguete, María Isabel,García-Verdugo, Eduardo,Luis, Santiago V.
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p. 1684 - 1691
(2019/04/03)
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- Additive-Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
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Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base increases the speed of the reaction drastically. Although some evidence was obtained supporting a dehydrogenation–hydrogenation mechanism, it was proven that this is not the major mechanism. Instead, the cobalt hydride complex formed by dehydrogenation of ethanol is capable of double-bond isomerization through alkene insertion–elimination.
- Spiegelberg, Brian,Dell'Acqua, Andrea,Xia, Tian,Spannenberg, Anke,Tin, Sergey,Hinze, Sandra,de Vries, Johannes G.
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supporting information
p. 7820 - 7825
(2019/05/22)
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- Manganese PNP-pincer catalyzed isomerization of allylic/homo-allylic alcohols to ketones-activity, selectivity, efficiency
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We report the first manganese catalyzed isomerization of allylic alcohols to produce the corresponding carbonyl compounds. The ligand plays a decisive role in the efficiency of this reaction. Very high conversions could be obtained using a solvent-free reaction system. A detailed DFT study reveals a self-dehydrogenation/hydrogenation reaction mechanism which was verified by the isolation of the α,β-unsaturated ketone as intermediate and a deuterium labeling experiment. It also provided a rationale for the observed selectivity and the higher efficiency of phenyl over isopropyl substitution.
- Xia, Tian,Spiegelberg, Brian,Wei, Zhihong,Jiao, Haijun,Tin, Sergey,Hinze, Sandra,De Vries, Johannes G.
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p. 6327 - 6334
(2019/11/20)
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- Ruthenium-Catalyzed Redox Isomerizations inside Living Cells
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Tailored ruthenium(IV) complexes can catalyze the isomerization of allylic alcohols into saturated carbonyl derivatives under physiologically relevant conditions, and even inside living mammalian cells. The reaction, which involves ruthenium-hydride intermediates, is bioorthogonal and biocompatible, and can be used for the "in cellulo" generation of fluorescent and bioactive probes. Overall, our research reveals a novel metal-based tool for cellular intervention, and comes to further demonstrate the compatibility of organometallic mechanisms with the complex environment of cells.
- Vidal, Cristian,Tomás-Gamasa, María,Gutiérrez-González, Alejandro,Mascarenas, José L.
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supporting information
p. 5125 - 5129
(2019/03/29)
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- Evaluation of the Catalytic Capability of cis- and trans-Diquinoxaline Spanned Cavitands
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Three new cis-diquinoxaline spanned cavitands were successfully synthesized. These cis-diphosphinated derivatives were applied in homogeneous gold-catalyzed dimerization and hydration of alkynes as well as rhodium-catalyzed styrene hydroformylation. The results were ranked with those obtained with their trans-diphosphinated isomeric analogues. The structure-activity relationship employing these two cavitands reveals that the cis- or trans-positioning of the catalyst centers directly influences cooperation between the two metallic atoms to control catalytic activity, reaction profile, and product selectivity. This comparative study provides us an intellectual basis for future catalytic cavitand chemistry and homogeneous catalysis.
- Inoue, Mami,Kamiguchi, Shinsuke,Ugawa, Katto,Hkiri, Shaima,Bouffard, Jules,Sémeril, David,Iwasawa, Tetsuo
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p. 6261 - 6268
(2019/11/05)
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- Phosphine-free cobalt catalyst precursors for the selective hydrogenation of olefins
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Cobalt(ii) complexes bearing phosphine-free tridentate NNS ligands were prepared. Depending on the ligand, dimeric or monomeric complexes were isolated. Monomeric Co(NNMeS)Cl2 selectively catalysed the hydrogenation of olefins in the presence of reducible moieties such as ketones. Further investigation showed that this complex functions as a nanoparticle precursor under the reaction conditions.
- Puylaert, Pim,Dell'Acqua, Andrea,El Ouahabi, Fatima,Spannenberg, Anke,Roisnel, Thierry,Lefort, Laurent,Hinze, Sandra,Tin, Sergey,De Vries, Johannes Gerardus
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- A Straightforward Deracemization of sec-Alcohols Combining Organocatalytic Oxidation and Biocatalytic Reduction
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An efficient organocatalytic oxidation of racemic secondary alcohols, mediated by sodium hypochlorite (NaOCl) and 2-azaadamantane N-oxyl (AZADO), has been conveniently coupled with a highly stereoselective bioreduction of the intermediate ketone, catalyzed by ketoreductases, in aqueous medium. The potential of this one-pot two-step deracemization process has been proven by a large set of structurally different secondary alcohols. Reactions were carried out up to 100 mm final concentration enabling the preparation of enantiopure alcohols with very high isolated yields (up to 98 %). When the protocol was applied to the stereoisomeric rac/meso mixture of diols, these were obtained with very high enantiomeric excesses and diastereomeric ratios (95 % yield, >99 % ee, >99: 1 dr).
- Liardo, Elisa,Ríos-Lombardía, Nicolás,Morís, Francisco,González-Sabín, Javier,Rebolledo, Francisca
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supporting information
p. 3031 - 3035
(2018/06/27)
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- Rational Design of a Metallocatalytic Cavitand for Regioselective Hydration of Specific Alkynes
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The synthesis of a functionalized supramolecular cavitand with inwardly oriented AuI and P=O moieties was explored, including its catalytic proclivity in the selective hydration of internal alkynes. The cavitand works as a supramolecular flask device: AuI coordinates to the triple bond, the P=O moiety connects with a H2O molecule, and the cavity favors folding of a single alkynyl side chain. Several tests of different substrate patterns indicated that the cavity was substrate specific, similar to enzymatic catalysis.
- Endo, Naoki,Inoue, Mami,Iwasawa, Tetsuo
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supporting information
p. 1136 - 1140
(2018/03/13)
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- Selective Catalytic Hydration of Alkynes in the Presence of Au-Cavitands: A Study in Structure–Activity Relationships
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The effects of the catalytic cavities in gold-functionalized cavitands in the hydration of internal alkynes have been studied. Variations on cavitand structures revealed the importance of two features that were studied: (1) flanking aromatic rings, and (2) an adjacent P=O moiety. The di-quinoxaline-spanned resorcin[4]arene system provides a well-defined compartment, in which a cationic Au ion activates an internal alkyne for conversion into a ketone by delivery of water that has also been activated, this time by a P=O moiety. We synthesized four variations on our parent cavitand. Variations of the cavitand walls include replacement of quinoxaline components with pyrazine or methylene units. Variation of the P=O center was accomplished with methylene or quinoxaline moieties. All variants displayed lower catalytic activity or selectivity, allowing us to confirm the significance both of an internal cavity and of an activation site for water.
- Inoue, Mami,Ugawa, Katto,Maruyama, Tomoyuki,Iwasawa, Tetsuo
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p. 5304 - 5311
(2018/09/12)
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- Isomerization of Allylic Alcohols to Ketones Catalyzed by Well-Defined Iron PNP Pincer Catalysts
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[Fe(PNP)(CO)HCl] (PNP=di-(2-diisopropylphosphanyl-ethyl)amine), activated in situ with KOtBu, is a highly active catalyst for the isomerization of allylic alcohols to ketones without an external hydrogen supply. High reaction rates were obtained at 80 °C, but the catalyst is also sufficiently active at room temperature with most substrates. The reaction follows a self-hydrogen-borrowing mechanism, as verified by DFT calculations. An alternative isomerization through alkene insertion and β-hydride elimination could be excluded on the basis of a much higher barrier. In alcoholic solvents, the ketone product is further reduced to the saturated alcohol.
- Xia, Tian,Wei, Zhihong,Spiegelberg, Brian,Jiao, Haijun,Hinze, Sandra,de Vries, Johannes G.
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supporting information
p. 4043 - 4049
(2018/01/27)
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- Aggregation of catalytically active Ru nanoparticles to inactive bulk, monitored in situ during an allylic isomerization reaction. Influence of solvent, surfactant and stirring
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The exploration of catalytic isomerization reactions of an allylic alcohol to ketone, in the presence of μ-oxo-triruthenium acetate as a precatalyst in alcohol solvents, has established that the catalyst is heterogeneous in nature and proceeds by means of the in situ formed Ru0 nanoparticles (Ru0NPs). This reaction is used as an indicator for evaluating the kinetics and mechanism for metallic NP formation and self-assembly. In ethanol, complete conversion of the reactant is achieved under all experimental conditions tested. Conversely, in iso-propanol or n-pentanol the catalytic particles swiftly lose activity and the reaction arrests after partial conversion. We conclude that, in ethanol the process of NP self-assembly results in the formation of active and stable NPs of a specific size, named C-particles. Consequently, we propose an additional step for the established mechanism of NP self-assembly, namely the aggregation of C-NPs to inactive bulk-metal, labeled as D (C + C → D). D-particles differ from other NPs present in the catalytic cycle in size and in the catalytic activity. The effect of surfactant and mixing is also explored and the acquired observations strongly support the proposed mechanism of catalyst formation and decay. Addition of surfactants and/or mixing slowed down the reaction rate but dramatically improved the lifetime of the catalyst and the observed conversions. We attribute this phenomenon to the inhibition of the aggregation step of the active C-NPs to inactive D bulk-metal. The aggregation step of C-NPs to inactive D-bulk is assumed for the first time. This assumption prompts all the experimental data to be consistent. Introduction of the new kinetic step enables the use of the proposed mechanism with the reactions, where the catalyst loses its activity in the course of the reaction, and it converts the mechanism of the metal NP self-assembly into the more universal form.
- Hitrik,Sasson
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p. 1481 - 1492
(2018/01/17)
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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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- Water as a catalytic switch in the oxidation of aryl alcohols by polymer incarcerated rhodium nanoparticles
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One of the major goals in the oxidation of organic substrates, and especially for alcohol oxidation, is the use of molecular oxygen as the oxidant under mild conditions. Here we report the synthesis and testing of Rh polymer incarcerated catalysts, using a metal so far not used for alcohol oxidation reactions, in which the catalytic activity towards aryl alcohol oxidation, for substrates like 1-phenylethanol and benzyl alcohol, is switched on by the addition of water as co-solvent in toluene. This is done by using air as oxidant at atmospheric pressure, in one of the mildest reaction conditions reported for this class of reaction. The promoting effect of water to higher conversions was observed also for rhodium over alumina supported catalysts, which were used as a benchmark allowing in all cases high conversion and selectivity to the ketone or the aldehyde within a short reaction time. The effect of water was explained as a medium capable to promote the oxidation of the alcohol to the ketone in a biphasic system assisted by phase transfer catalysis. This is particularly relevant for alcohols like 1-phenylethanol or benzyl alcohol that are not soluble in water at room temperature, and for which alternative oxidation routes are needed, as well as to switch on the catalytic activity of metal nanoparticles in a facile and green manner for the activation of molecular oxygen. Aliphatic alcohols like 1-octanol and 3-octanol were also tested, still showing Rh based catalysts as promising materials for this reaction if toluene only was used as solvent instead.
- Weston, Jack O.,Miyamura, Hiroyuki,Yasukawa, Tomohiro,Sutarma, Dedi,Baker, Chloe A.,Singh, Preabjot K.,Bravo-Sanchez, Mariela,Sano, Naoko,Cumpson, Peter J.,Ryabenkova, Yulia,Kobayashi, Shu,Conte, Marco
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p. 3985 - 3998
(2017/09/25)
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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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- 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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supporting information
p. 5864 - 5871
(2017/07/10)
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- One-pot sustainable synthesis of tertiary alcohols by combining ruthenium-catalysed isomerisation of allylic alcohols and chemoselective addition of polar organometallic reagents in deep eutectic solvents
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Ru(iv)-Catalysed redox isomerisation of allylic alcohols has, for the first time, been successfully assembled with the chemoselective addition of organolithium or organomagnesium reagents to the in situ formed ketones, en route to tertiary alcohols, employing deep eutectic solvents as environmentally friendly reaction media. The overall transformation, which formally involves three consecutive and different steps such as (i) the reduction of a C-C double bond, (ii) the oxidation of a secondary carbinol moiety, and (iii) a chemoselective C-C bond formation, takes place in protic and biorenewable eutectic mixtures in a sequential one-pot fashion using a commercially and easily available catalytic system, with excellent conversions (up to 99% yield), at room temperature and under air in the last step, with no concomitant reduction or enolisation processes, and with high atom economy, in agreement with the principles of the so-called green chemistry.
- Cicco, Luciana,Rodríguez-álvarez, María J.,Perna, Filippo M.,García-álvarez, Joaquín,Capriati, Vito
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supporting information
p. 3069 - 3077
(2017/07/24)
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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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p. 4138 - 4146
(2017/09/28)
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- Methods to produce fuels
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The present disclosure generally relates to the catalytic conversion of alcohols into hydrocarbon ketones suitable for use as fuels. More specifically, the present disclosure relates to the catalytic conversion of a mixture of isopropanol-butanol-ethanol (IBE) or acetone-butanol-ethanol (ABE), into ketones suitable for use as fuels. The ABE or IBE mixtures may be obtained from the fermentation of biomass or sugars.
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Page/Page column 43; 44
(2018/02/28)
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- Base metal Schiff base complexes applied as catalysts for the oxidation of n-octane
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The catalytic oxidation of n-octane to value-added oxygenates has been studied with a series of salen-type complexes of iron. The four iron Schiff base complexes N,N′-bis(salicylidene)-L-iron(III) chloride [L?=?1,2-phenylenediamine (5); ethylenediamine (6); propylenediamine (7) and butylenediamine (8)] were synthesised by variation of the bridging diamine backbone. All the complexes are fully characterised and the crystal structure of 7 is for the first time reported as a centrosymmetric dimer observed to crystallise in the triclinic P1 ̄ system. The application of 5–8 in this oxidation reaction represents a rare example of the systematic use of iron-salen complexes for the liquid-phase functionalisation of Csp3–H bonds of straight chain alkanes. All catalysts displayed activity with H2O2 and TBHP as oxidants that resulted in a mixture of oxygenated products dominated by the ketones (2-, 3- and 4-octanones). Observed trends and variations in catalytic activities of the complexes is related to differences in chemical/structural features and changes in reaction conditions. A detailed analysis of selectivity parameters of the complexes to the variety of oxygenates is also presented and rationalised.
- Kadwa, Ebrahim,Friedrich, Holger B.,Bala, Muhammad D.
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p. 112 - 117
(2017/04/27)
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- Alkane oxidation catalysed by a self-folded multi-iron complex
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A preorganised ligand scaffold is capable of coordinating multiple Fe(II) centres to form an electrophilic CH oxidation catalyst. This catalyst oxidises unactivated hydrocarbons including simple, linear alkanes under mild conditions in good yields with selectivity for the oxidation of secondary CH bonds. Control complexes containing a single metal centre are incapable of oxidising unstrained linear hydrocarbons, indicating that participation of multiple centres aids the CH oxidation of challenging substrates.
- Mettry, Magi,Moehlig, Melissa Padilla,Gill, Adam D.,Hooley, Richard J.
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p. 120 - 128
(2016/11/09)
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- Selective Oxidation of Aliphatic Alcohols using Molecular Oxygen at Ambient Temperature: Mixed-Valence Vanadium Oxide Photocatalysts
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Here we report a class of photocatalysts: mixed-valence vanadium oxide particles grafted onto a variety of oxide supports. In these catalysts V6O13 species with mixed oxidation states (V4+ or V5+) are believed to be catalytically active sites. These catalysts successfully enable alcohol oxidation to selectively produce aldehydes and ketones using O2 as the oxidant. The catalytic process is driven by visible light irradiation at room temperature and, most importantly, progresses with negligible overoxidation. The catalysts can even selectively oxidize aliphatic alcohols, which are much more challenging to control in comparison to aromatic analogues. They can also be applied to the activation and oxidation of the otherwise stable C-H bonds of saturated aromatic hydrocarbons, such as toluene and xylene, under irradiation. Both experimental results and density functional theory (DFT) simulations suggest the formation of V6O13-alkoxide species as the initial step in the catalytic cycle. The V6O13-alkoxide then acts as the light harvester, being excited by light of wavelength shorter than 550 nm. Facile room-temperature C-H bond cleavage in the excited state V6O13-alkoxide in the presence of O2 leads to the carbonyl-containing products. These findings demonstrate an example of light-driven selective oxidation of diverse alcohols via in situ formation of photoresponsive V6O13-alkoxide species. This catalytic process is especially valuable for the synthesis of temperature-sensitive products and represents an alternative pathway to many conventional thermal oxidation reactions.
- Zavahir, Sifani,Xiao, Qi,Sarina, Sarina,Zhao, Jian,Bottle, Steven,Wellard, Mark,Jia, Jianfeng,Jing, Liqiang,Huang, Yiming,Blinco, James P.,Wu, Haishun,Zhu, Huai-Yong
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p. 3580 - 3588
(2016/07/06)
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- Non-plasmonic metal nanoparticles as visible light photocatalysts for the selective oxidation of aliphatic alcohols with molecular oxygen at near ambient conditions
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Nanoparticles (NPs) of Pd and Pt were used for the selective oxidation of aliphatic alcohols with molecular oxygen as an oxidant at near ambient temperatures under visible light irradiation. Distinct final products were obtained under identical reaction conditions, aliphatic esters formed over the Pd NPs while aldehydes formed over the Pt NPs. The reason for this different product selectivity is proven to be due to the much stronger interaction of Pd NPs with alcohol and aldehyde compared to Pt NPs. The photocatalytic activity is tuneable by light intensity or a moderate change in the reaction temperature.
- Tana, Tana,Guo, Xiao-Wei,Xiao, Qi,Huang, Yiming,Sarina, Sarina,Christopher, Phillip,Jia, Jianfeng,Wu, Haishun,Zhu, Huaiyong
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p. 11567 - 11570
(2016/10/03)
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- Visible-Light-Induced Efficient Selective Oxidation of Nonactivated Alcohols over {001}-Faceted TiO2 with Molecular Oxygen
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In the presence of molecular oxygen, a {001}-faceted nanocrystalline anatase TiO2 catalyst enabled the selective oxidation of nonactivated aliphatic alcohols to the corresponding aldehydes or ketones under visible light. The reaction shows excellent conversion and selectivity towards the formation of the carbonyl products without over-oxidation to the corresponding carboxylic acids. The exceptional reactivity of the catalyst is possibly due to the absorption of visible light originating from a stronger interaction of alcohol with the {001} facet, which facilitates the modification of the band structure of TiO2, thus facilitating the photogenerated hole transfer and subsequent oxidation processes. The experimental results have also been corroborated by first-principles quantum chemical DFT calculations.
- Vadakkekara, Raji,Biswas, Abul Kalam,Sahoo, Tapan,Pal, Provas,Ganguly, Bishwajit,Ghosh, Subhash Chandra,Panda, Asit Baran
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supporting information
p. 3084 - 3089
(2016/11/13)
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- Sodium hypochlorite pentahydrate (NaOCl·5H2O) crystals; An effective re-oxidant for TEMPO oxidation
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The novel oxidant of sodium hypochlorite pentahydrate (NaOCl·5H2O), which is now available for industrial and laboratory use has several advantageous properties. The crystalline material has 44% of NaOCl, contains minimal sodium hydroxide and sodium chloride, and the aqueous solution indicates pH 11-12. Herein, NaOCl·5H2O crystals are examined for use as an oxidant for primary and secondary alcohols, with or without nitroxyl radicals, in the presence or absence of phase-transfer catalysts. The pentahydrate crystals alone (without nitroxyl radicals) demonstrate a powerful oxidizing ability, converting secondary alcohols to the corresponding ketones. In the presence of TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) or 1-Me-AZADO (1-methyl-2-azaadamantane N-oxy radical), sterically hindered secondary alcohols are oxidized without pH adjustment. A proposed mechanism for the oxidation is discussed.
- Okada, Tomohide,Asawa, Tomotake,Sugiyama, Yukihiro,Iwai, Toshiaki,Kirihara, Masayuki,Kimura, Yoshikazu
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p. 2818 - 2827
(2016/05/19)
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- From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction
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The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning.
- Ríos-Lombardía, Nicolás,Vidal, Cristian,Liardo, Elisa,Morís, Francisco,García-álvarez, Joaquín,González-Sabín, Javier
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supporting information
p. 8691 - 8695
(2016/07/21)
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