- Negatively Charged N-Heterocyclic Carbene-Stabilized Pd and Au Nanoparticles and Efficient Catalysis in Water
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Herein we describe the synthesis of negatively charged N-heterocyclic carbene (NHC)-functionalized palladium and gold nanoparticles (NPs), which are stable in water for over 3 months. The formation of these NHC-NPs proceeds via an efficient ligand exchange procedure. This method was successfully applied to different negatively charged NHCs bearing sulfonate and carboxylate groups. The obtained PdNPs were investigated as catalysts in hydrogenation reactions and showed high catalytic activity (TON up to 2500 and TOF up to 2000 h-1).
- Ferry, Angélique,Schaepe, Kira,Tegeder, Patricia,Richter, Christian,Chepiga, Kathryn M.,Ravoo, Bart Jan,Glorius, Frank
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- Preparation of well-defined dendrimer encapsulated ruthenium nanoparticles and their application as catalyst and enhancement of activity when utilised as SCILL catalysts in the hydrogenation of citral
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Silica supported dendrimer encapsulated ruthenium nanoparticles were prepared and evaluated as catalysts in the hydrogenation of citral. The dendrimer encapsulated nanoparticles were prepared using the generation 4 (G4), generation 5 (G5) and generation 6 (G6) hydroxyl-terminated poly(amidoamine) (PAMAM-OH) dendrimers as templating agents with different Ru metal:dendrimer ratios. The effects of ionic liquids as catalyst coatings on the catalytic activity were investigated for the ionic liquids [BMIM][NTf2], [OMIM][NTf2], [BMIM][BF4], [BMIM][PF6], [EMIM][OcS] and [EMIM][EtS]. An enhancement in catalytic activity was observed when utilising [BMIM][NTf2] as an ionic liquid coating with selectivity towards citronellal.
- Antonels, Nathan Charles,Meijboom, Reinout
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- Quinolinium Fluorochromate (QFC), C9H7NH: An Improved Cr(VI)-Oxidant for Organic Substrates
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Yellow-orange crystalline quinolinium fluorochromate (QFC) is easily prepared in a nearly quantitative yield by the interaction of quinoline with CrO3 and hydrofluoric acid in 1:1.5:1 molar ratio.The reagent is stable.Compared with pyridinium fluorochromate (PFC), the new reagent is more soluble in organic solvents and less acidic.QFC in CH2Cl2 readily oxidizes primary, secondary, and allylic alcohols to the corresponding carbonyls, benzoin to benzil, and anthracene and phenanthrene to anthraquinone and 9,10-phenanthrenequinone, respectively.Oxidations work well also in a variety of sensitive environments, e.g. isopropylidene functionality and trimethylsilyl ethers.Organic sulfides are transformed to sulfoxides at room temperature.The facile oxidation of triphenylphosphine to triphenylphosphine oxide by QFC in CH2Cl2 or CH3CN provides a clear evidence for an oxygen-transfer reaction.The reduced product of QFC, isolated after such reactions, has been ascertained to be C9H7NH, a chromium(IV) species.The advantages of QFC have been highlighted.
- Chaudhuri, Mihir K.,Chettri, Shiv K.,Lyndem, Synjukta,Paul, Pradip C.,Srinivas, Pendyala
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- ENHANCEMENT OF THE HYDROLYSIS OF GERANYL PYROPHOSPHATE BY BIVALENT METAL IONS. A MODEL FOR ENZYMIC BIOSYNTHESIS OF CYCLIC MONOTERPENES
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Hydrolysis of geranyl pyrophosphate is catalyzed by salts of Mn2+ and involves C-O bond cleavage.The first order rate constants reach limiting values with 2+> 10E-2 M, and the most reactive species is GPP (Mn2+)2 at the optimum pH of 6.5-7.The products are similar to those from acid hydrolysis except that more cyclic hydrocarbons are formed in the presence of metal ions.Hydrolysis of geranyl phosphate is inhibited, and that of citronellyl pyrophosphate is weakly catalyzed by Mn2+.Other divalent metal cations catalyze the hydrolysis of geranyl pyrophosphate and the sequence of effectiveness is Cu2+>Mn2+>Co2+>Mg2+ Ca2+.
- Vial, M. V.,Rojas, C.,Portilla, G.,Chayet, L.,Perez,L. M.,et al.
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- A highly reduced graphene oxide/ZrOx-MnCO3 or -Mn2O3 nanocomposite as an efficient catalyst for selective aerial oxidation of benzylic alcohols
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Highly reduced graphene oxide (HRG) nanocomposites of manganese carbonate doped with (1%) zirconia (ZrOx) nanoparticles [ZrOx(1%)-MnCO3/(X%)HRG (where X = 0-7)] were prepared employing a facile coprecipitation method in which the percentage of HRG was varied. The resulting nanocomposite was calcined at 300°C. Further calcination of the catalyst at 500°C resulted in the conversion of manganese carbonate to manganese oxide [ZrOx(1%)-Mn2O3/(X%)HRG]. The effect of the inclusion of HRG on the catalytic activity along with its comparative performance between carbonates and their respective oxides was studied for the liquid-phase selective oxidation of benzylic alcohols into corresponding aldehydes using molecular oxygen as the eco-friendly oxidizing agent without adding any external additives or bases. The influence of different parameters such as different percentages of HRG, reaction times, calcination temperatures, catalyst dosages and reaction temperatures have also been systematically studied in order to optimize the catalyst composition and reaction conditions. The inclusion of HRG as a dopant remarkably enhanced the catalytic efficiency of ZrOx-MnCO3 nanocatalysts for the aerobic oxidation of alcohols. The as-prepared catalysts were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area analysis, Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR). The catalyst with composition ZrOx(1%)-MnCO3/(1%)HRG obtained by calcination at 300°C exhibited excellent specific activity (60.0 mmol g-1 h-1) with 100% benzyl alcohol conversion and more than 99% product selectivity within an extremely short time (4 min). The same catalyst is employed for the oxidation of a wide range of substituted benzylic and aliphatic alcohols. The catalyst i.e. ZrOx(1%)-MnCO3/(1%)HRG calcined at 300°C yielded corresponding aldehydes with complete convertibility and selectivity in short reaction times under mild conditions whereas the as-prepared catalyst exhibited high selectivity for aromatic alcohols over aliphatic alcohols. The catalyst was recycled and reused at least five times without any obvious loss in its activity or selectivity.
- Assal, Mohamed E.,Shaik, Mohammed Rafi,Kuniyil, Mufsir,Khan, Mujeeb,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.,Khan, Sohail M. A.,Tremel, Wolfgang,Tahir, Muhammad Nawaz,Adil, Syed Farooq
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- A highly selective Pd(OAc)2/pyridine/K2CO3 system for oxidation of terpenic alcohols by dioxygen
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Molecular sieves, complex organic bases and radical oxidants are commonly used in alcohols oxidation reactions. In this work, we have evaluated the beneficial effects of addition of K2CO3 to Pd(II)-catalyzed oxidation alcohols, which resulted in a remarkable increase in the oxidation reaction rates without selectivity losses. Herein, in a metallic reoxidant-free system, terpenic alcohols (β-citronellol, nerol and geraniol) were selectively converted into respective aldehydes from Pd(II)-catalyzed oxidation reactions in presence of dioxygen. High conversions and selectivities (greater than 90%) were achieved in the presence of the Pd(OAc)2/K2CO3 catalyst and pyridine excess. The exogenous role of others auxiliary anionic and nitrogen compounds was appraised. Graphical Abstract: Reaction conditions: β-citronellol (2.75 mmol); Pd(OAc)2 (0.05 mmol); pyridine (5.0 mmol); K 2CO3 (2.5 mmol); toluene (10 mL); MS3A (0.5 g); O2 (0.10 MPa); 60 °C.[Figure not available: see fulltext.]
- Carari, Danieli M.,Da Silva, Marcio J.
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- Oxidation of alcohols by [Cp*Rh(ppy)(OH)]+
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Rh(III) polypyridine complexes ([Cp*Rh(ppy)(H2O)]2+; ppy = 2,2′-bipyridine, 2,2′-bipyridine-4,4′-dicarboxylate, o-phenanthroline, tetrahydro-4,4′-dialkyl-bis-oxazole) oxidize in organic or aqueous alkaline solution primary and secondary alcohols to aldehydes or ketones and are thereby reduced to the Rh(I) complexes Cp*Rh(ppy). The Rh(III) form can be regenerated by oxidants like pyruvate or oxygen, making the reaction quasi-catalytic. The reaction follows an autocatalytic pathway; hydrogen transfer from the a-CH2 group of an alcoholate complex [Cp*Rh(ppy)(OR)]+ to Cp*Rh(I)(ppy) is suggested to yield the Rh(II) intermediate Cp*Rh(ppy)H as the key and rate determining step. The knowledge of Rh(III)/Rh(I) redox potentials allows to estimate the thermodynamic driving force of the reaction which is not more than about 300mV.
- Koelle, Ulrich,Fraenzl, Holger
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- Heterologous expression and characterization of the ene-reductases from Deinococcus radiodurans and Ralstonia metallidurans
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The Old Yellow Enzyme (OYE) homologues or ene-reductases (ER) from Deinococcus radiodurans (DrER) and Ralstonia metallidurans (RmER) were cloned and characterized. Sequence and phylogenetic analysis revealed both these enzymes to belong to the YqjM-like or "thermophilic-like" group of OYEs, both sharing more than 60% sequence similarity to the ER from Thermus scotoductus. This group of OYEs is characterized by a conserved cysteine residue modulating the redox potential of the flavin cofactor as well as a conserved tyrosine residue located at the N-terminus region involved in binding certain ligands. The genes were recombinantly expressed in Escherichia coli as functional soluble proteins. Both ERs have monomer molecular weights of approximately 40 kDa, with DrER a homodimer in solution and RmER a monomer. DrER and RmER are optimally active at pH 7-7.5 at 30 C and 35 C respectively. Although the enzymes showed comparable affinities towards the ubiquitous ER substrate 2-cyclohexenone, the specific activity and catalytic efficiency of DrER were more than twice those observed for RmER. Similar to other members of this subclass of ERs, no conversion was detected with cyclic Cβ substituted enones, and only DrER was able to convert citral. Both DrER and RmER were highly active at reducing N-phenyl substituted maleimides. The selectivity of the ERs was assessed using both the isomers of carvone, which were converted with high diastereomeric excesses. Ketoisophorone and 2-methylcyclopentenone were converted to their (R)- and (S)-enantiomeric products respectively. Finally, a light-driven cofactor regeneration system was used to drive enzymatic reduction in the absence of NAD(P)H.
- Litthauer,Gargiulo,Van Heerden,Hollmann,Opperman
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- Aerobic oxidation of monoterpenic alcohols catalyzed by ruthenium hydroxide supported on silica-coated magnetic nanoparticles
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Ruthenium hydroxide supported on silica-coated magnetic nanoparticles was shown to be an efficient heterogeneous catalyst for the liquid-phase oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant in the absence of co-catalysts or additives. The material was prepared through the loading of the amino modified support with ruthenium(III) ions from an aqueous solution of ruthenium(III) chloride followed by treatment with sodium hydroxide to form ruthenium hydroxide species. Characterizations suggest that ruthenium hydroxide is highly dispersed on the support surface, with no ruthenium containing crystalline phases being detected. Various carbonylic monoterpenoids important for fragrance and pharmaceutical industries can be obtained in good to excellent yields starting from biomass-based monoterpenic alcohols, such as isoborneol, perillyl alcohol, carveol, and citronellol. The catalyst undergoes no metal leaching and can be easily recovered by the application of an external magnet and re-used.
- Costa, Vinicius V.,Jacinto, Marcos J.,Rossi, Liane M.,Landers, Richard,Gusevskaya, Elena V.
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- Physically and chemically mixed TiO2-supported Pd and Au catalysts: unexpected synergistic effects on selective hydrogenation of citral in supercritical CO2
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The selective hydrogenation of citral was studied with various TiO2-supported monometallic and bimetallic Pd and Au catalysts and their physical mixtures in supercritical CO2 (scCO2). Significant synergistic effects appeared when active Pd species was chemically or physically mixed with less active Au species. The total rate of conversion was greatly enhanced and the selectivity to citronellal (CAL) was improved. The physical properties of those catalysts were characterized by TEM, HRTEM-EDS, XPS, and UV/Vis and their features of H2 desorption were examined by TPD. The physical and chemical characterization results were used to discuss the reasons for the unexpected synergistic effects observed. The same selective hydrogenation was also conducted in a conventional non-polar organic solvent of n-hexane to examine the roles of scCO2. The use of scCO2 was effective for accelerating the hydrogenation of citral and improving the selectivity to CAL.
- Liu, Ruixia,Yu, Yancun,Yoshida, Kazuki,Li, Guiming,Jiang, Haoxi,Zhang, Minhua,Zhao, Fengyu,Fujita, Shin-ichiro,Arai, Masahiko
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- Continuous selective hydrogenation of citral in a trickle-bed reactor using ionic liquid modified catalysts
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The influence of the ionic liquid [BMIM][N(CN)2] on the palladium catalyzed hydrogenation of citral in a trickle-bed reactor has been investigated. Applying the SCILL concept (solid catalyst with ionic liquid layer), it was possible to attain citronellal selectivities close to 100% at the cost of catalyst activity. However, the yield of this intermediate was approximately four times higher compared to the neat palladium catalyst. The latter and its SCILL counterpart both seem to have long-term stability, which is relevant for any future industrial application. This is the first time that SCILL systems have been compared directly to their IL-free equivalents in continuous mode.
- W?rz, Nicolai,Arras, Jürgen,Claus, Peter
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- Nature of catalyst deactivation during citral hydrogenation: A catalytic and ATR-IR study
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Deactivation of a 5 wt% Pd/Al2O3 catalyst during hydrogenation of citral (1) to citronellal (2), 3,7-dimethyl-2-octenal (3), and dihydrocitronellal (4) has been studied in a continuous-flow fixed-bed reactor. The reactions were carried out at 40 °C and 190 bar in hexane, supercritical CO2, or ethane as solvents. ATR-IR spectroscopic analysis of the solid/liquid interphase under reaction conditions at low pressure revealed that 1 and 3 decarbonylate on the Pd surface resulting in strongly adsorbed CO and CxHy-type hydrocarbon fragments. The absence of decarbonylation products from 2 and 4 and the excellent chemoselectivity for the hydrogenation of the C=C bonds are interpreted by adsorption of the molecules in a tilted position on Pd, π-bonded via one C=C bond (2) or di-π-bonded via the C=C-C=O fragment (1 and 3). A practically important observation is that a short reoxidation by air of the used Pd/Al2O3 under very mild conditions (40 °C, 6 bar) can circumvent further deactivation, but the original activity cannot be regained. All these observations indicate that the irreversible deactivation of Pd/Al2O3 cannot be traced to CO poisoning. We propose that site blocking caused by heavier oligomeric surface products is the major reason for the observed catalyst deactivation. Elsevier Inc. All rights reserved.
- Burgener, Marco,Wirz, Ronny,Mallat, Tamas,Baiker, Alfons
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- Iron-iron oxide core-shell nanoparticles are active and magnetically recyclable olefin and alkyne hydrogenation catalysts in protic and aqueous media
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We report for the first time the use of iron-iron oxide core-shell nanoparticles for the hydrogenation of olefins and alkynes under mild conditions in ethanol and in an aqueous medium. This catalyst proves robust towards the presence of oxidants, such as oxygen and water, is magnetically recoverable and shows selectivity towards the less activated double bonds. The Royal Society of Chemistry 2012.
- Hudson, Reuben,Riviere, Antoine,Cirtiu, Ciprian M.,Luska, Kylie L.,Moores, Audrey
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- Schiff base Cu(I) catalyst for aerobic oxidation of primary alcohols
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We report here new copper(I)-Schiff base complexes for the selective oxidation of primary alcohols to aldehydes under ambient conditions (with 2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO), N-methylimidazole (NMI), ambient air, acetonitril and RT). Particularly, the copper(I) complex bearing N-(4-fluorophenyl)-1-(furan-2-yl)methanimine (L2) showed high activity in the series and gave near- quantitative yields in the oxidations of benzyl alcohol (99% yield in 1 h) and 1-octanol (96% yield in 24 h). Based on the X-ray structure determination, the complex has a square pyramidal coordination accomplished by two L2 ligands and bromide as a counter anion. The oxidation reactions were monitored with UV–vis and in situ ATR-IR spectroscopy to study the changes in the catalytic structure and to elucidate the catalytic properties and the mechanistic details. Accordingly, detachment of one of the L2 ligands from the complexes is related to the oxidation activity.
- Lagerspets, Emi,Lagerblom, Kalle,Heli?vaara, Eeva,Hiltunen, Otto-Matti,Moslova, Karina,Nieger, Martin,Repo, Timo
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- Effect of the acid-base properties of the support on the performance of Pt catalysts in the partial hydrogenation of citral
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In this work, the effect that mesoporous solid materials, with different acid-base properties (Pt-1 wt%/acid or base) have over the product distribution during the partial hydrogenation of citral was evaluated. It was found that basic materials were the most active catalysts reaching a 100% citral conversion after 1 h of reaction. Regarding selectivity, in basic materials (Pt/MgAl-c and Pt/MgAl-r) citronellal was the main product, while nerol and geraniol were produced in acid solids (Pt/SiO2; Pt/SiO2-TiO2 and Pt/SiO2-ZrO2). The formation of unsaturated alcohols is related to the strength and density of the acid sites of the catalyst and in this sense the Pt/SiO2-ZrO2 gave a yield of 80%. The acidity trend is: Pt/SiO2-ZrO2 > Pt/SiO 2-TiO2 > Pt/SiO2 > Pt/MgAl-c.
- Santiago-Pedro, Smid,Tamayo-Galván, Victoria,Viveros-García, Tomas
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- Catalytic activity of nanoscale borides: Co2B and Ni7B3 in the liquid-phase hydrogenation of citral
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Metal borides are unconventional heterogeneous catalysts. Now, two compounds – the new phase Ni7B3 and well-known Co2B – were synthesized as well-defined, nanoscale material. After characterization (X-ray diffraction, scanning electron microscopy, nitrogen physisorption) they were tested for the liquid phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) in n-hexane at different temperatures. Hydrogenation products such as geraniol, nerol, citronellal and citronellol were analyzed. The Ni-free catalyst Co2B results in the formation of nerol and geraniol or citronellol selectively, depending on the reaction time. The new compound Ni7B3 yields citronellal or citronellol, depending on the temperature. Thus, the hydrogenation potential of borides – obtained as well-characterized, unsupported heterogeneous catalysts by a one-pot synthesis procedure and post-synthetic annealing – is demonstrated. The cobalt boride preferentially hydrogenates C[dbnd]O bonds, while the nickel boride is selective for C[dbnd]C double bonds.
- Kalyon,Hofmann,Malter,Lucas,Claus,Albert
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- Mimicking nature: Synthetic nicotinamide cofactors for C=C bioreduction using enoate reductases
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A series of synthetic nicotinamide cofactors were synthesized to replace natural nicotinamide cofactors and promote enoate reductase (ER) catalyzed reactions without compromising the activity or stereoselectivity of the bioreduction process. Conversions and enantioselectivities of >99% were obtained for C=C bioreductions, and the process was successfully upscaled. Furthermore, high chemoselectivity was observed when employing these nicotinamide cofactor mimics (mNADs) with crude extracts in ER-catalyzed reactions.
- Paul, Caroline E.,Gargiulo, Serena,Opperman, Diederik J.,Lavandera, Iván,Gotor-Fernández, Vicente,Gotor, Vicente,Taglieber, Andreas,Arends, Isabel W. C. E.,Hollmann, Frank
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- Pd nanoparticles immobilized on graphite oxide modified with a base: Highly efficient catalysts for selective hydrogenation of citral
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In this work, the Pd-based catalysts were designed via immobilizing Pd nanoparticles on graphite oxide (GO) modified with organic base, 1,1,3,3-tetramethylguanidine (TMG), which was used for the selective hydrogenation of citral. These catalysts were characterized by various techniques including IR, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the Pd particles with size less than 5 nm were uniformly distributed throughout the support, and they were in the electron-deficient state due to the strong interactions with the modified support. The resultant Pd-TMG/GO catalyst displayed high efficiency for the selective hydrogenation of citral with a turnover frequency of 7100 h-1 as well as superior selectivity to citronellal of 89.6%. Moreover, the catalyst can be reused for five times without obvious activity loss, which may result from its stable structure.
- Zhao, Yanfei,Zhang, Hongye,Huang, Changliang,Chen, Sha,Yu, Bo,Xu, Jilei,Liu, Zhimin
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- Microwave-assisted partial hydrogenation of citral by using ionic liquid-coated porous glass catalysts
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The microwave-assisted hydrogenation of citral (3,7-dimethylocta-2,6- dienal) to citronellal with molecular hydrogen as the reducing agent was investigated. Several polar and non-polar solvents were screened and imidazolium-based ionic liquids were applied as modifiers for the palladium-containing porous glass catalysts (Pd/TP). The best results were obtained with N-ethyl-N'-methylimidazolium dicyanamide, N-ethyl-N'- methylimidazolium acetate, or N-ethyl-N'-methylimidazolium trifluoroacetate, which were used to prepare supported catalysts with an ionic liquid layer (SCILL) on Pd/TP by wet-impregnation. The influence of pressure and temperature when using these ionic liquid-containing catalysts, as well as their long-term stabilities, were examined. Working with microwave-assisted heating, high yields of citronellal were achieved under mild conditions within short reaction times. Catalyst characterization was carried out by means of BET measurements, X-ray photoelectron spectroscopy (XPS) and thermo-gravimetric analyses. The influences of the ionic liquid layer were derived from experiments carried out before and after the reactions. Copyright
- Gallert, Thomas,Hahn, Martin,Sellin, Martin,Schm?ger, Christine,Stolle, Achim,Ondruschka, Bernd,Keller, Thomas F.,Jandt, Klaus D.
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- Room-temperature hydrogenation of citral catalyzed by palladium-silver nanocrystals supported on SnO2
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We have developed two strategies to optimize Pd catalysts. On one hand, Ag was introduced into Pd and then they were applied to the selective hydrogenation of citral under mild conditions. The addition of metallic Ag could tune the selectivity of Pd and made it suitable for the selective hydrogenation of the conjugated double bond. The selectivity of citronellal increased from 0 (for Pd/C and Pd0.7Ag0.3/C) to 96% (for Pd0.4Ag0.6/C) as the Ag content increased. On the other hand, the addition of SnO2 made the Pd catalysts more inclined to activate the C=O bond and gave better performance for the hydrogenation of the conjugated double bond compared with the corresponding Pd-Ag catalysts. The selectivity of citronellal increased from 0 (for Pd0.7Ag0.3/C) to 76% (for Pd0.7Ag0.3-SnO2/C was used) after the addition of SnO2. On the basis of these results, we developed a catalyst (Pd0.6Ag0.4-SnO2/C) with the best catalytic performance for the selective hydrogenation of citral (the conversion of citral reached 99%, and the selectivity was up to 96%). We have developed two strategies to optimize Pd catalysts for the selective hydrogenation of citral and exploited a catalyst (Pd0.6Ag0.4-SnO2/C) with the best catalytic performance (the conversion of citral reached 99%, and the selectivity was up to 96%).
- Wang, Shuo,Shen, Rongan,Chen, Zheng,Wang, Jiaxi,Wang, Dingsheng,Li, Yadong
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- Efficient, copper-catalyzed, aerobic oxidation of primary alcohols
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An additive is the key to success: Catalytic amounts of N-methylimidazole are crucial for the aerobic oxidation of primary aliphatic alcohols in the presence of CuCl, 1,10-phenanthroline (phen), and di-tert-butyl azodicarboxylate (DBAD). This reaction, under neutral conditions, yields the aldehydes quantitatively and selectively without overoxidation to the carboxylic acids.
- Marko, Istvan E.,Gautier, Arnaud,Dumeunier, Raphael,Doda, Kanae,Philippart, Freddi,Brown, Stephen M.,Urch, Christopher J.
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- The TEMPO/copper catalyzed oxidation of primary alcohols to aldehydes using oxygen as stoichiometric oxidant
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A catalytic system for the selective oxidation of primary alcohols to aldehydes under very mild conditions was developed. The catalytic system is based on TEMPO and Cu(II), which is generated in situ by oxidation of elemental copper and chelated by means of 2,2′-bipyridine. Compared to existing Cu/TEMPO oxidation methods we substantially lowered the amount of copper necessary and discovered that the reaction is dependent on pH. The catalytic system was also tested with polymer-bound TEMPO and new insights into the currently discussed mechanism were derived. Springer-Verlag 2005.
- Geisslmeir, David,Jary, Walther G.,Falk, Heinz
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- An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols
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Structure-guided directed evolution of choline oxidase has been carried out by using the oxidation of hexan-1-ol to hexanal as the target reaction. A six-amino-acid variant was identified with a 20-fold increased kcat compared to that of the wild-type enzyme. This variant enabled the oxidation of 10 mm hexanol to hexanal in less than 24 h with 100 % conversion. Furthermore, this variant showed a marked increase in thermostability with a corresponding increase in Tm of 20 °C. Improved solvent tolerance was demonstrated with organic solvents including ethyl acetate, heptane and cyclohexane, thereby enabling improved conversions to the aldehyde by up to 30 % above conversion for the solvent-free system. Despite the evolution of choline oxidase towards hexan-1-ol, this new variant also showed increased specific activities (by up to 100-fold) for around 50 primary aliphatic, unsaturated, branched, cyclic, benzylic and halogenated alcohols.
- Heath, Rachel S.,Birmingham, William R.,Thompson, Matthew P.,Taglieber, Andreas,Daviet, Laurent,Turner, Nicholas J.
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- PHOTO-OXIDATION OF ALCOHOLS CATALYSED BY PLATINISED TITANIUM DIOXIDE
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Irradiation of alcohols in benzene in the presence of platinised titanium dioxide provides a clean and convenient procedure for the synthesis of aldehydes and ketones on preparative scale.
- Hussein, Falah H.,Pattenden, Gerald,Rudham, Robert,Russell, James J.
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- Modified liquid–liquid interface cultivation system with floating microspheres and binder micro-pieces for slow-growing or unicellular microorganisms: Application to interfacial bioconversions with an actinomycete and yeasts
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Liquid–liquid interface bioreactor (L–L IBR) is a unique non-aqueous bioconversion system which comprises a hydrophobic organic solvent (upper phase), a fungal cells–floating microspheres (MS) layer (middle phase), and a liquid medium (lower phase). In this study, a modified L–L IBR with actinomycetes and yeasts was developed by using binder micro-pieces (BM) and estimated its availability through some bioconversions. This modified interface cultivation system was named a tacky liquid–liquid interface bioreactor (L–L IBRtac). After the detailed estimation of its characteristics, the system was applied to oxidation of citronellol to citronellal, 2-methylcyclohexanol to 2-methylcyclohexanone, and 2-octanol to 2-octanone with Rhodococcus hoagii NBRC 3730, oxidation of citronellal to citronellic acid with Candida viswanathii NBRC 10321, and transacetylation of citronellol by acetyl coenzyme A (acetyl-CoA) produced from glucose by Pichia kluyveri NBRC 1165. The accumulation of citronellal, 2-methylcyclohexanone, and 2-octanone reached 3.1 (16 days), 2.3 (12 days), and 32.9 g/l (12 days) in spite of strong biotoxicities of the substrates/products without collapse of a cells–MS–BM layer. On the other hand, 6.1 g/l of citronellic acid and 2.8 g/l of citronellyl acetate were produced from 5% citronellal and 10% citronellol for 12 days, respectively.
- Oda, Shinobu,Nakanishi, Mami,Ishikawa, Asako,Baba, Toshiki
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- Synthesis and Comparative Catalytic Study of Zirconia–MnCO3 or –Mn2O3 for the Oxidation of Benzylic Alcohols
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We report on the synthesis of the zirconia–manganese carbonate ZrOx(x %)–MnCO3 catalyst (where x=1–7) that, upon calcination at 500 °C, is converted to zirconia–manganese oxide ZrOx(x %)–Mn2O3. We also present a comparative study of the catalytic performance of the both catalysts for the oxidation of benzylic alcohol to corresponding aldehydes by using molecular oxygen as the oxidizing agent. ZrOx(x %)–MnCO3 was prepared through co-precipitation by varying the amounts of Zr(NO3)4 (w/w %) in Mn(NO3)2. The morphology, composition, and crystallinity of the as-synthesized product and the catalysts prepared upon calcination were studied by using scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and powder X-ray diffraction. The surface areas of the catalysts [133.58 m2 g?1 for ZrOx(1 %)–MnCO3 and 17.48 m2 g?1 for ZrOx(1 %)–Mn2O3] were determined by using the Brunauer–Emmett–Teller method, and the thermal stability was assessed by using thermal gravimetric analysis. The catalyst with composition ZrOx(1 %)–MnCO3 pre-calcined at 300 °C exhibited excellent specific activity (48.00 mmolg?1 h?1) with complete conversion within approximately 5 min and catalyst cyclability up to six times without any significant loss in activity. The specific activity, turnover number and turnover frequency achieved is the highest so far (to the best of our knowledge) compared to the previously reported catalysts used for the oxidation of benzyl alcohol. The catalyst showed selectivity for aromatic alcohols over aliphatic alcohols.
- Assal, Mohamed E.,Kuniyil, Mufsir,Khan, Mujeeb,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.,Tremel, Wolfgang,Nawaz Tahir, Muhammad,Adil, Syed Farooq
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- Studies on Transition Metal Peroxo Complexes. Part 8. The Nature of Peroxomolybdates and Peroxotungstates in Aqueous Solution
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The nature of the species formed in solutions of (2-) and (2-) (1-0.1 mol dm-3) in the presence of H2O2 (5-0.5 mol dm-3) from pH 12 to acid has been studied by Raman and i.r. spectroscopy and, for molybdenum-containing species, by (95)Mo n.m.r. spectroscopy.The polymerisation processes are far less complex in the presence of H2O2 than in its absence.The principal species are likely to be (2-), (2-), (2-) and, at lower pH, complexes containing the (2+) unit.Vibrational assignments are proposed for K2*2H2O (M = Mo or W) using (18)O and (2)H substitution.Parallel studies on the oxidation of alcohols and alkenes by (2-) in excess of H2O2 from pH 7 to 0.5 suggest that (2-) is the most effective oxidising species.Stoicheiometric oxidations of primary alcohols to aldehydes, of secondary alcohols to ketones, and of cyclohexene to its epoxide by 2 are briefly reported.
- Campbell, Nicholas J.,Dengel, Andrew C.,Edwards, Catherine J.,Griffith, William P.
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- Kinetic influences on enantioselectivity in asymmetric catalytic hydrogenation
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The influence of reaction conditions on enantioselectivity in the RuII-(binap)-catalyzed asymmetric hydrogenation of allylic alcohols is discussed. This work highlights the importance of considering kinetic influences in addition to the stereochemical aspects of the chiral catalytic environment in interpreting catalytic behavior in asymmetric hydrogenation reactions.
- Sun, Yongkui,Wang, Jian,LeBlond, Carl,Reamer, Robert A.,Laquidara, Joseph,Sowa Jr., John R.,Blackmond, Donna G.
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- Organic Chemistry by Infrared Lasers. 4. Laser-Induced Reactions of γ-Unsaturated Alcohols
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The laser-induced chemistry of 3-buten-1-ol (1), 3-butyn-1-ol (2), 3,4-pentadien-1-ol (3), 2-isopropenyl-5-methylcyclohexanol (l-isopulegol; 4), and 1,5-hexadien-3-ol (5) is described.Retro-ene reactions occur in all cases, though with compound 5 a competitive oxy-Cope reaction is also observed.The reactions are generally clean and give rise to conversions in the range of 48-78 percent after 300-500 pulses.In these reactions between 2-10 photons are absorbed per molecule per pulse, and in some instances as much as 40 percent conversion is obtained after five pulses.The laser-induced chemistry seems to follow the known thermal chemistries of these systems.
- Madison, Stephen A.,Chen, Ruth,Keehn, Philip M.
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- A remarkably simple α-oximation of aldehydes via organo-SOMO catalysis
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A novel α-oximation reaction of unactivated aldehydes has been achieved in excellent yields by reaction with NaNO2-FeCl3 couple and in the presence of pyrrolidine as organocatalyst.
- Gentili, Patrizia,Pedetti, Silvia
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- Engineering a nicotinamide mononucleotide redox cofactor system for biocatalysis
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Biological production of chemicals often requires the use of cellular cofactors, such as nicotinamide adenine dinucleotide phosphate (NADP+). These cofactors are expensive to use in vitro and difficult to control in vivo. We demonstrate the development of a noncanonical redox cofactor system based on nicotinamide mononucleotide (NMN+). The key enzyme in the system is a computationally designed glucose dehydrogenase with a 107-fold cofactor specificity switch toward NMN+ over NADP+ based on apparent enzymatic activity. We demonstrate that this system can be used to support diverse redox chemistries in vitro with high total turnover number (~39,000), to channel reducing power in Escherichia coli whole cells specifically from glucose to a pharmaceutical intermediate, levodione, and to sustain the high metabolic flux required for the central carbon metabolism to support growth. Overall, this work demonstrates efficient use of a noncanonical cofactor in biocatalysis and metabolic pathway design.
- Black, William B.,Zhang, Linyue,Mak, Wai Shun,Maxel, Sarah,Cui, Youtian,King, Edward,Fong, Bonnie,Sanchez Martinez, Alicia,Siegel, Justin B.,Li, Han
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- Catalytic activity dependency on catalyst components in aerobic copper-TEMPO oxidation
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The influence of catalyst components in the copper-TEMPO (2,2,6,6-tetramethylpiperidine N-oxide) catalysed aerobic oxidation of alcohols was investigated. The type and amount of base greatly influences reactivity. The bipyridyl ligand concentration had no major influence on catalysis, but ex-cessive amounts led to a decrease in activity for longer reaction times. The kinetic dependency for TEMPO was found to be 1.15, and for copper 2.25, which is an indication of a binuclear catalytic system. Optimised conditions with various allylic and aliphatic alcohols give good to excellent rapid oxidations.
- Kumpulainen, Esa T. T.,Koskinen, Ari M. P.
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- Regioselective catalytic hydrogenation of citral with ionic liquids as reaction modifiers
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Silica and polyaniline supported palladium catalysts prepared by different techniques (incipient-wetness impregnation, deposition precipitation) using Pd(OAc)2 or H2PdCl4 as precursors were studied in the liquid-phase hydrogenation of citral under addition of several ionic liquids ([BMIM][NTf2], [BMIM][PF6], [BMPL][NTf 2], [BMIM][DCA], [BMPL][DCA], [B3MPYR][DCA]) either as catalyst coating or as additive. By an incipient-wetness technique, the catalysts were coated with a mixture of IL in acetone. The catalysts were characterized by nitrogen physisorption, whereby a decrease of surface area and pore volume was detected by the IL coated catalysts. Furthermore, ICP-OES, TEM and IR spectroscopy were performed to analyze metal content, particle size and coverage of the catalyst with ionic liquid. Citral hydrogenation was performed at 323 K and under 2.0 MPa H2 in an autoclave with off-line GC analysis of the product mixtures. Beside stirrer speed, catalyst mass and citral concentration, the type and quantity of ionic liquid were also varied to elucidate their influence on activity and selectivity of the Pd/SiO2 catalysed citral hydrogenation. The results show that treatment of the catalyst with ionic liquids - independent of catalyst coating or additive - leads to a selectivity enhancement of the desired product, citronellal. With [PF6] - or [NTf2]- as the IL anion, maximum selectivities were (60 ± 2)% at 70% conversion. In particular, dicyanamide (DCA) containing ionic liquids allow, under optimised conditions, the quantitative one-pot synthesis of citronellal, at least if the Pd/SiO 2 catalyst was coated with 29 wt% [B3MPYR][DCA]. By using polyaniline supported Pd catalysts and [BMIM][DCA] as additive, the consecutive hydrogenation towards dihydrocitronellal was less pronounced and the influence of metal precursor, support material and preparation technique of the catalyst could be excluded. Hydrogenation of pure citral on [BMIM][DCA] coated palladium catalysts offers a solvent-free, green route to citronellal in reasonable selectivities (S = 86%).
- Arras, Juergen,Steffan, Martin,Shayeghi, Yalda,Ruppert, Dominik,Claus, Peter
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- Metals in Biotechnology: Cr-Driven Stereoselective Reduction of Conjugated C=C Double Bonds
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Elemental metals are shown to be suitable sacrificial electron donors to drive the stereoselective reduction of conjugated C=C double bonds using Old Yellow Enzymes as catalysts. Both direct electron transfer from the metal to the enzyme as well as mediated electron transfer is feasible, although the latter excels by higher reaction rates. The general applicability of this new chemoenzymatic reduction method is demonstrated, and current limitations are outlined.
- Rauch, Marine C. R.,Gallou, Yann,Delorme, Léna,Paul, Caroline E.,Arends, Isabel W. C. E.,Hollmann, Frank
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- Shape controlled synthesis of palladium nanocrystals by combination of oleylamine and alkylammonium alkylcarbamate and their catalytic activity
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The shape of Pd nanocrystals (NCs) can be controlled by combination of oleylamine (OAm) and alkylammonium alkylcarbamate (AAAC), and Pd spheres, tetrahedra and multipods have been synthesized. The multipods and tetrahedra are much more active than the sph
- Hu, Baoji,Ding, Kunlun,Wu, Tianbin,Zhou, Xiaosi,Fan, Honglei,Jiang, Tao,Wang, Qian,Han, Buxing
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- Zr-CATALYZED OXIDATION OF ALCOHOLS TO ALDEHYDES IN THE PRESENCE OF t-BuOOH. HIGH REACTIVITY FOR PRIMARY AND ALLYLIC HYDROXYL FUNCTIONS
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ZrO(OAc)2 catalyzes selective oxidation of primary alcohols to aldehydes without formation of carboxylic acids and also chemoselective oxidation of allylic alcohols to α,β-unsaturated aldehydes in the presence of t-BuOOH.
- Kaneda, Kiyotomi,Kawanishi, Yasuyuki,Teranishi, Shiichiro
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- Selective hydrogenation of citral over Au-based bimetallic catalysts in supercritical carbon dioxide
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Selective hydrogenation of citral was investigated over Au-based bimetallic catalysts in the environmentally benign supercritical carbon dioxide (scCO 2) medium. The catalytic performances were different in citral hydrogenation when Pd or Ru was mixed (physically and chemically) with Au. Compared with the corresponding monometallic catalyst, the total conversion and the selectivity to citronellal (CAL) were significantly enhanced over TiO 2 supported Pd and Au bimetallic catalysts (physically and chemically mixed); however, the conversion and selectivity did not change when Ru was physically mixed with Au catalyst compared to the monometallic Ru/TiO 2, and the chemically mixed Ru-Au/TiO2 catalyst did not show any activity. The effect of CO2 pressure on the conversion of citral and product selectivity was significantly different over the Au/TiO 2, Pd-Au/TiO2, and Pd/TiO2 catalysts. It was assumed to be ascribed to the difference in the interactions between Au, Pd nanoparticles and CO2 under different CO2 pressures.
- Liu, Ruixia,Zhao, Fengyu
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- A TEMPO-free copper-catalyzed aerobic oxidation of alcohols
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The copper-catalyzed aerobic oxidation of primary and secondary alcohols without an external N-oxide co-oxidant is described. The catalyst system is composed of a Cu/diamine complex inspired by the enzyme tyrosinase, along with dimethylaminopyridine (DMAP) or N-methylimidazole (NMI). The Cu catalyst system works without 2,2,6,6-tetramethyl-l-piperidinoxyl (TEMPO) at ambient pressure and temperature, and displays activity for un-activated secondary alcohols, which remain a challenging substrate for catalytic aerobic systems. Our work underscores the importance of finding alternative mechanistic pathways for alcohol oxidation, which complement Cu/TEMPO systems, and demonstrate, in this case, a preference for the oxidation of activated secondary over primary alcohols.
- Xu, Boran,Lumb, Jean-Philip,Arndtsen, Bruce A.
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- Oxoammonium resins as metal-free, highly reactive, versatile polymeric oxidation reagents
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Polymer-supported oxidation of alcohols was conducted very efficiently by employing oxoammonium salts, the reactive intermediates in TEMPO oxidations (TEMPO = 2,2,6,6-tetramethylpiperidinoxyl). These highly reactive salts (see scheme; X = Br, C1) could be prepared and isolated on the polymeric support, and were used for the conversion of single compounds as well as of complex mixtures of alcohols.
- Weik, Steffen,Nicholson, Graeme,Jung, Gnther,Rademann, Jrg
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- Kinetic study of the hydrogenation of citral on ir promoted Au/Tio 2 catalyst
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A kinetic study of citral hydrogenation over an Au-Ir/TiO2 catalyst was performed with the aim to understand the effect of iridium on gold in this catalytic system. Au-Ir/TiO2 catalyst was prepared by co-deposition precipitation in an atomic ratio of 3/1. The effect of citral concentration, hydrogen pressure and temperature effect were also studied. The product distribution obtained is related with the proportion of Meδ+/Me0 sites. The deactivation of the catalyst occurs in the whole studied temperature range, 363 to 403 K, being more drastic as temperature increases due to the irreversible adsorbed CO blocks principally Ir0 sites. From initial reaction rates treatment an apparent global order close to 1 was determined. A Langmuir-Hinshelwood-type kinetic model involving the surface reaction as the rate limiting step between adsorbed citral and hydrogen on active sites with different nature shows good agreement with experimental initial reaction rates.
- Martinez, Jose J.,Rojas, Hugo,Reyes, Patricio
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- 3,5-dimethylpyrazolium chlorochromate(VI): An efficient reagent for solvent-free oxidation of organic substrates
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A new chromium(VI) reagent 3,5-dimethylpyrazolium chlorochromate, C 5H8N2H[CrO3Cl] (DmpzHCC), was synthesized and used for the selective oxidation of various organic compounds under solvent-free conditions with high efficiency. This new compound has certain advantages over its companion analogues in terms of controlled acidity, amount of oxidant, lack of solvent, short reaction times, and high yields.
- Canbulat, Melek,Oezguen, Beytiye
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- Cell-free protein engineering of Old Yellow Enzyme 1 from Saccharomyces pastorianus
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In protein engineering, cell-free transcription/translation of linear mutagenic DNA templates can tremendously accelerate and simplify the screening of enzyme variants. Using the RApid Parallel Protein EvaluatoR (RAPPER) protocol, we have evaluated the impact of amino acid substitutions and loop truncations on substrate specificity and stereoselectivity of Old Yellow Enzyme 1 from Saccharomyces pastorianus. Our study demonstrates the benefit of systematically assessing amino acid variations including substrate profiling to explore sequence-function space.
- Quertinmont, Leann T.,Lutz, Stefan
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- Carbon-carbon double bond versus carbonyl group hydrogenation: Controlling the intramolecular selectivity with polyaniline-supported platinum catalysts
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The use of polyaniline (PANI) as catalyst support for heterogeneous catalysts and their application in chemical catalysis is hitherto rather poorly known. We report the successful synthesis of highly dispersed PANI-supported platinum catalysts (particle sizes between 1.7 and 3.7 nm as revealed by transmission electron microscopy, TEM) choosing two different approaches, namely (i) deposition-precipitation of H2PtCl6 onto polyaniline, suspended in basic medium (DP method) and, (ii) immobilization of a preformed nanoscale platinum colloid on polyaniline (sol-method). The PANI-supported platinum catalysts were applied in the selective hydrogenation of the α,β-unsaturated aldehyde citral. In order to benchmark their catalytic performance, citral hydrogenation was also carried out by using platinum supported on the classical support materials silica (SiO2), alumina (Al2O3), active carbon and graphite. The relations of the structural characteristics and surface state of the catalysts with respect to their hydrogenation properties have been probed by EXAFS and XPS. It is found that the DP method yields chemically prepared PtO2 on polyaniline and, thus, produces a highly dispersed and immobilized Adams catalyst (in the β-PtO2 form) which is able to efficiently hydrogenate the conjugated C=C bond of citral (selectivity to citronellal=87%), whereas reduction of the C=O group occurs with polyanilinesupported platinum (selectivity to geraniol/nerol=78%) prepared via the sol-method. The complete reversal of the selectivity between the preferred hydrogenation of the conjugated C=C or C=O group is not only particularly useful for the selective hydrogenation of α,β-unsaturated aldehydes but also unveils the great potential of conducting polymer-supported precious metals in the field of hitherto barely investigated chemical catalysis.
- Steffan, Martin,Klasovsky, Florian,Arras, Juergen,Roth, Christina,Radnik, Joerg,Hofmeister, Herbert,Claus, Peter
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- Imprinted Naked Pt Nanoparticles on N-Doped Carbon Supports: A Synergistic Effect between Catalyst and Support
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A synergistic effect resulting from the interaction of small (2.4–3.1 nm) naked Pt nanoparticles (NPs) imprinted on N-doped carbon supports is evidenced by structural, electronic and electrochemical characterization. The size and distribution of the sputtered Pt NPs are found to be related to the nature of the support because Pt NPs are preferentially located at Ngraphitic sites. In addition, Rutherford backscattering shows that a deeper penetration of the Pt NPs is obtained in the N-doped carbon support with larger pore diameters. The ligand effect of the N-doped carbon supports is found to occur by electron donation from Npyrrolic and Ngraphitic sites to the Pt NPs and the electron acceptor behavior of the C=Npyridinic sites. The carbon matrix acquires a basic characteristic (electron-richer, metallic behavior) capable of interacting with metallic NPs akin to a bimetallic-like system. The imprinted Pt NPs are active catalysts for oxidation, although displaying poor catalytic activity for reduction reactions. The catalyst N-doped carbon supports play an important role in the overall catalytic process, rather than only acting as a simple active phase carrier.
- Bolzan, Gustavo R.,Abarca, Gabriel,Gon?alves, Wellington D. G.,Matos, Carolina F.,Santos, Marcos J. L.,Dupont, Jairton
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- Selective hydrogenation of citral catalyzed with palladium nanoparticles in CO2-in-water emulsion
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CO2-in-Water (C/W) emulsion was formed by using a nonionic surfactant of poly (ethylene oxide)-poly (propylene oxide)-poly (ethylene oxide) (P123), and palladium nanoparticles were synthesized in situ in the present work. The catalytic performa
- Liu, Ruixia,Wu, Chaoyong,Wang, Qiang,Ming, Jun,Hao, Yufen,Yu, Yancun,Zhao, Fengyu
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- Structural insights into stereospecific reduction of α, β-unsaturated carbonyl substrates by old yellow enzyme from Gluconobacter oxydans
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We report the crystal structure of old yellow enzyme (OYE) family protein Gox0502 (a.a 1-315) in free form at 3.3 ?. Detailed structural analysis revealed the key residues involved in stereospecific determination of Gox0502, such as Trp66 and Trp100. Structure-based computational analysis suggested the bulky side chains of these tryptophan residues may play important roles in product stereoselectivity. The introduction of Ile or Phe or Tyr mutation significantly reduced the product diastereoselectivity. We hypothesized that less bulky side chains at these critical residues could create additional free space to accommodate intermediates with different conformations. Notably, the introduction of Phe mutation at residue Trp100 increased catalytic activity compared to wild-type Gox0502 toward a set of substrates tested, which suggests that a less bulky Phe side chain at residue W100F may facilitate product release. Therefore, Gox0502 structure could provide useful information to generate desirable OYEs suitable for biotechnological applications in industry.
- Yin, Bo,Deng, Jian,Lim, Lirong,Yuan, Y. Adam,Wei, Dongzhi
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- Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
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One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
- Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
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- ORGANIC COMPOUNDS
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Disclosed are TRPM8 modulators as defined by formula (I) for achieving a cooling effect on skin and mucousa.
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Page/Page column 66; 125
(2021/06/04)
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- A new catalytic approach for aerobic oxidation of primary alcohols based on a Copper(I)-thiophene carbaldimines
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We report here novel Cu(I) thiophene carbaldimine catalysts for the selective aerobic oxidation of primary alcohols to their corresponding aldehydes and various diols to lactones or lactols. In the presence of the in situ generated Cu(I) species, a persistent radical (2,2,6,6-tetramethylpiperdine-N-oxyl (TEMPO)) and N-methylimidazole (NMI) as an auxiliary ligand, the reaction proceeds under aerobic conditions and at ambient temperature. Especially the catalytic system of 1-(thiophen-2-yl)-N-(4-(trifluoromethoxy)phenyl)methanimine (ligand L2) with copper(I)-iodide showed high reactivity for all kind of alcohols (benzylic, allylic and aliphatic). In the case of benzyl alcohol even 2.5 mol% of copper loading gave quantitative yield. Beside high activity under aerobic conditions, the catalysts ability to oxidize 1,5-pentadiol to the corresponding lactol (86% in 4 h) and N-phenyldiethanolamine to the corresponding morpholine derivate lactol (86% in 24 h) is particularly noteworthy.
- Lagerspets, Emi,Valbonetti, Evelyn,Eronen, Aleksi,Repo, Timo
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- B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of: In situ -formed enamines
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A highly efficient B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of in situ-formed enamines in the presence of water and pinacolborane was developed. Regioselective β-deuteration of tertiary amines was achieved with high chemo- and regioselectivity. D2O was used as a readily available and cheap source of deuterium. Mechanistic studies indicated that B(C6F5)3 could activate water to promote the protonation and reduction of enamines. This journal is
- Wu, Rongpei,Gao, Ke
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supporting information
p. 4032 - 4036
(2021/05/19)
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- Rhodium-Catalyzed Remote Isomerization of Alkenyl Alcohols to Ketones
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We develop herein an efficient rhodium-catalyzed remote isomerization of aromatic and aliphatic alkenyl alcohols into ketones. This catalytic process, with a commercially available catalyst and ligand ([RhCl(cod)]2 and Xantphos), features high efficiency, low catalyst loading, good functional group tolerance, a broad substrate scope, and no (sub)stoichiometric additive. Preliminary mechanistic studies suggest that this transformation involves an iterative dissociative β-hydride elimination-migration insertion process.
- Dong, Wenke,Yang, Hongxuan,Yang, Wen,Zhao, Wanxiang
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supporting information
(2020/02/28)
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- Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
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The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
- López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
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p. 342 - 350
(2020/02/04)
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- Macromolecule-loaded oxidizing agent containing iodine with high valence, and preparation method and application thereof
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The invention discloses a macromolecule-loaded oxidizing agent containing iodine with high valence, and a preparation method and an application thereof. 2-iodobenzoic acid is used as a raw material and is loaded on chloromethyl polystyrene resin under an alkaline condition, and iodine is oxidized into high valence by using potassium monopersulfate. The macromolecule-loaded oxidizing agent containing iodine with high valence, prepared through the method can oxidize primary alcohol into aldehyde and, secondary alcohol into ketone, and a reaction byproduct is water; the reaction conditions are mild, the post-treatment is convenient, and the macromolecular-loaded oxidizing agent containing iodine with high valence can be separated from the reaction system only by simple filtration; and the macromolecule-loaded oxidizing agent containing iodine with high valence can be recycled for multiple times, so that the influence on the environment and the production cost are reduced. Besides, the macromolecular-loaded oxidizing agent containing iodine with high valence is simple and convenient to prepare, effectively solves the problems of stability and high cost of a micromolecular iodine-containing oxidizing agent, and has a wide application prospect in the field of fine chemical engineering.
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Paragraph 0017; 0021-0022; 0025-0026
(2020/05/30)
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- Efficient aerial oxidation of different types of alcohols using ZnO nanoparticle–MnCO3-graphene oxide composites
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Graphene–metal nanocomposites have been found to remarkably enhance the catalytic performance of metal nanoparticle-based catalysts. In continuation of our previous report, in which highly reduced graphene oxide (HRG)-based nanocomposites were synthesized and evaluated, we present nanocomposites of graphene oxide (GRO) and ZnO nanoparticle-doped MnCO3 ([ZnO–MnCO3/(1%)GRO]) synthesized via a facile, straightforward co-precipitation technique. Interestingly, it was noticed that the incorporation of GRO in the catalytic system could noticeably improve the catalytic efficiency compared to a catalyst (ZnO–MnCO3) without GRO, for aerial oxidation of benzyl alcohol (BzOH) employing O2 as a nature-friendly oxidant under base-free conditions. The impacts of various reaction factors were thoroughly explored to optimize reaction conditions using oxidation of BzOH to benzaldehyde (BzH) as a model substrate. The catalysts were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. The (1%)ZnO–MnCO3/(1%)GRO exhibited significant specific activity (67 mmol.g?1.hr?1) with full convversion of BzOH and >99% BzH selectivity within just 6 min. The catalytic efficiency of the (1%)ZnO–MnCO3/(1%)GRO nanocomposite was significantly better than the (1%)ZnO–MnCO3/(1%)HRG and (1%)ZnO–MnCO3 catalysts, presumably due to the existence of oxygen-possessing groups on the GRO surface and as well as a very high surface area that could have been instrumental in uniformly dispersing the active sites of the catalyst, i.e., ZnO–MnCO3. Under optimum circumstances, various kinds of alcohols were selectively transformed to respective carbonyls with full convertibility over the (1%)ZnO–MnCO3/(1%)GRO catalyst. Furthermore, the highly effective (1%)ZnO–MnCO3/(1%)GRO catalyst could be successfully reused and recycled over five consecutive runs with a marginal reduction in its performance and selectivity.
- Adil, Syed Farooq,Assal, Mohamed E.,Shaik, Mohammed Rafi,Kuniyil, Mufsir,Hashmi, Azhar,Khan, Mujeeb,Khan, Aslam,Tahir, Muhammad Nawaz,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.
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- Selective Hydrogenation of Citral on Pt-Containing Catalysts at Room Temperature and Atmospheric Pressure
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Abstract: It is shown that the 1% Pt/CeO2–ZrO2 (1% Pt/CZ) catalytic system allows selective hydrogenation of citral with a 94% conversion and a selectivity towards unsaturated alcohols of 59% at room temperature and atmospheric pressure. The effect of addition of alkali to the reaction mixture on the yield of the target products is studied, and the optimum conditions of the reaction are determined.
- Vikanova,Redina
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p. 2566 - 2569
(2019/12/30)
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- Novel Old Yellow Enzyme Subclasses
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Many drug candidate molecules contain at least one chiral centre, and consequently, the development of biocatalytic strategies to complement existing metal- and organocatalytic approaches is of high interest. However, time is a critical factor in chemical process development, and thus, the introduction of biocatalytic steps, even if more suitable, is often prevented by the limited availability of off-the-shelf enzyme libraries. To expand the biocatalytic toolbox with additional ene reductases, we screened 19 bacterial strains for double bond reduction activity by using the model substrates cyclohexanone and carvone. Overall, we identified 47 genes coding for putative ene reductases. Remarkably, bioinformatic analysis of all genes and the biochemical characterization of four representative novel ene reductases led us to propose the existence of two new Old Yellow Enzyme subclasses, which we named OYE class III and class IV. Our results demonstrate that although, on a DNA level, each new OYE subclass features a distinct combination of sequence motifs previously known from the classical and the thermophilic-like group, their substrate scope more closely resembles the latter subclass.
- Peters, Christin,Frasson, David,Sievers, Martin,Buller, Rebecca
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p. 1569 - 1577
(2019/05/15)
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- Method for selectively hydrogenating alpha, beta-unsaturated carbonyl compound by cobalt complex
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The invention provides a method for selectively hydrogenating an alpha, beta-unsaturated carbonyl compound. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound comprises the steps that first, a cobalt metal precursor and a carbene ligand are coordinated in a solution to obtain a cobalt complex, and the cobalt complex selectively enables the alpha, beta-unsaturated carbonyl compound to be reduced into a corresponding saturated carbonyl compound in a hydrogen atmosphere under the activation of an activator. The method for selectively hydrogenating the alpha, beta-unsaturated carbonyl compound has the main advantages that cobalt is used as a catalyst, and metal cobalt is cheap and easy to obtain relative to noble metal such as palladium, ruthenium, osmium, iridium and platinum, and the catalyst cost is greatly reduced; secondly, the carbene ligand used in the method has the advantages of simple structure, low price, strong coordination ability with cobalt atoms compared with a commonly used phosphine ligand; and finally, the addition of the activator can further significantly increase the activity of the cobalt catalyst. The hydrogenation reaction condition is mild, the reaction rate is high, substantially no carbonyl hydrogenation side reaction occurs, and the carbonyl compound can be obtained in a high yield.
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Paragraph 0070-0072
(2019/11/20)
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- Biocatalytic N-Alkylation of Amines Using Either Primary Alcohols or Carboxylic Acids via Reductive Aminase Cascades
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The alkylation of amines with either alcohols or carboxylic acids represents a mild and safe alternative to the use of genotoxic alkyl halides and sulfonate esters. Here we report two complementary one-pot systems in which the reductive aminase (RedAm) from Aspergillus oryzae is combined with either (i) a 1° alcohol/alcohol oxidase (AO) or (ii) carboxylic acid/carboxylic acid reductase (CAR) to affect N-alkylation reactions. The application of both approaches has been exemplified with respect to substrate scope and also preparative scale synthesis. These new biocatalytic methods address issues facing alternative traditional synthetic protocols such as harsh conditions, overalkylation and complicated workup procedures.
- Ramsden, Jeremy I.,Heath, Rachel S.,Derrington, Sasha R.,Montgomery, Sarah L.,Mangas-Sanchez, Juan,Mulholland, Keith R.,Turner, Nicholas J.
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p. 1201 - 1206
(2019/01/21)
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- On-the-fly Catalyst Accretion and Screening in Chemoselective Flow Hydrogenation
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Herein, it is reported an on-the-fly accretion/reaction protocol to evaluate the structure-performance relationship in the chemoselective flow citral hydrogenation over Ni-based catalysts. Based on the methodology one was able to determine Ni nanoparticles ideal average size (ca. 9 nm), in a rapid and facile manner. The methodology offers a simple workflow, cost-effective and adaptable strategy for process intensification and optimization.
- Giziński, Damian,B?achucki, Wojciech,?r?bowata, Anna,Zienkiewicz-Machnik, Ma?gorzata,Goszewska, Ilona,Matus, Krzysztof,Lisovytskiy, Dmytro,Pisarek, Marcin,Szlachetko, Jakub,Sá, Jacinto
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p. 3641 - 3646
(2018/08/07)
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- Nerol and geraniol preparation method
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The invention discloses a nerol and geraniol solid-phase method production technology. The technology adopts citral, paraformaldehyde and sodium hydroxide as raw materials, adds quaternary phosphoniumsalt as an auxiliary agent, and performs a solid-phase reaction in a ball mill reactor. After completion of the reaction, the obtained slurry is subjected to sieving, centrifugation, washing, and finally distilled to obtain nerol and geraniol products. The process is the green and solid-phase synthesis process, the product is easy to separate and purify, and the by-product sodium formate is highin purity and can be directly sold. The process overcomes the disadvantages of more step, low yield, large amount of three wastes, and many impurities in products in a traditional process route, and has industrial value.
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Paragraph 0032-0052
(2019/01/08)
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- ATP3 and MTP3: Easily Prepared Stable Perruthenate Salts for Oxidation Applications in Synthesis
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The Ley–Griffith tetra-n-propylammonium perruthenate (TPAP) catalyst has been widely deployed by the synthesis community, mainly for the oxidation of alcohols to aldehydes and ketones, but also for a variety of other synthetic transformations (e.g. diol cleavage, isomerizations, imine formation and heterocyclic synthesis). Such popularity has been forged on broad reaction scope, functional group tolerance, mild conditions, and commercial catalyst supply. However, the mild instability of TPAP creates preparation, storage, and reaction reproducibility issues, due to unpreventable slow decomposition. In search of attributes conducive to catalyst longevity an extensive range of novel perruthenate salts were prepared. Subsequent evaluation unearthed a set of readily synthesized, bench stable, phosphonium perruthenates (ATP3 and MTP3) that mirror the reactivity of TPAP, but avoid storage decomposition issues.
- Moore, Peter W.,Read, Christopher D. G.,Bernhardt, Paul V.,Williams, Craig M.
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supporting information
p. 4556 - 4561
(2018/03/13)
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- Selective Aerobic Oxidation of Alcohols with NO3? Activated Nitroxyl Radical/Manganese Catalyst System
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A homogeneous Mn(NO3)2/2,2,6,6-tetramethylpiperidin-1-yl)oxyl/2-picolinic acid catalyst system is highly active and versatile for the selective aerobic oxidation of alcohols (2,2,6,6-tetramethylpiperidin-1-yl)oxyl=TEMPO, 2-picolinic acid=PyCOOH). The catalytic method enables near quantitative conversion of various primary alcohols to the respective aldehydes using a very simple reaction setup and workup. This study presents findings on the catalyst stability and mechanisms of deactivation. The results show that NO3? plays a crucial catalytic role in the reaction as a source of oxygen activating NOx species. Yet, disproportionation of NO3? to the volatile NO2 during the reaction leads to catalyst deactivation under open air conditions. Catalyst deactivation through this route can be overcome by adding a catalytic amount of nitrate salt, for example NaNO3 into the reaction. This stabilizes the Mn(NO3)2/TEMPO/PyCOOH catalyst and enables oxidation of various primary alcohols to the respective aldehydes using low catalyst loadings under ambient conditions. Secondary alcohols can be oxidized with a modified catalyst utilizing sterically accessible nitroxyl radical 9-azabicyclo[3.3.1]nonane N-oxyl (ABNO) instead of TEMPO. At the end of the alcohol oxidation, pure carbonyl products and the reusable catalyst can be recovered simply by extracting with organic solvent and dilute aqueous acid, followed by evaporation of both phases.
- Lagerblom, Kalle,Keskiv?li, Juha,Parviainen, Arno,Mannisto, Jere,Repo, Timo
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p. 2908 - 2914
(2018/05/03)
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- A Highly Selective Na2WO4-Catalyzed Oxidation of Terpenic Alcohols by Hydrogen Peroxide
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Sodium tungstate was found to be an active and highly selective catalyst to oxidation of various primary or secondary origin renewable alcohols by hydrogen peroxide as green oxidant. Borneol, nerol, geraniol and β-citronellol were efficiently and selectively converted to respective carbonyl derivatives by hydrogen peroxide. ATR/FT-IR measurements confirmed that Na2W(O2)4 was the specie active catalytically. The role of the main reaction variables, including temperature, reactants and catalyst concentration, solvent, and nature of substrate were also assessed. In addition to use a green oxidant, this simple and environmentally friendly catalyst system did not require additive to control pH, molecular sieves or phase transfer catalyst. Graphical Abstract: [Figure not available: see fulltext.].
- Viana, Luna Andrade Silva,da Silva, Giovanna Rodrigues Nobile,da Silva, Márcio Jose
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p. 374 - 382
(2017/12/04)
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- Diazaphospholene Precatalysts for Imine and Conjugate Reductions
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The first examples of 1,3,2-diazaphospholene-catalyzed imine reduction and conjugate reduction reactions are reported. This approach employs readily synthesized alkoxydiazaphospholene precatalysts that can be handled in open air. Reduction of substrates containing Lewis basic functionality, isolated unsaturation, and protic functional groups was accomplished. The synthetic utility of this approach is demonstrated by the synthesis of the important antiparkinson medicine rasagiline and the natural product zingerone.
- Adams, Matt R.,Tien, Chieh-Hung,Huchenski, Blake S. N.,Ferguson, Michael J.,Speed, Alexander W. H.
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supporting information
p. 6268 - 6271
(2017/05/19)
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- A process for preparing optically active aldehyde or ketone method (by machine translation)
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The present invention provides an asymmetric hydrogenation process for preparing optically active aldehyde or ketone of the method. The invention using transition metal catalyst and amino acid ester catalyst, so that the α, β - unsaturated aldehyde or ketone by selective asymmetric hydrogenation and the preparation of optically active aldehyde or ketone, reaction selectivity is greatly improved, the optical purity of the product can be as high as 99ee %. (by machine translation)
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-
Paragraph 0107; 0108; 0109
(2017/07/19)
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- Highly efficient aqueous phase chemoselective hydrogenation of α,β-unsaturated aldehydes catalysed by phosphine-decorated polymer immobilized IL-stabilized PdNPs
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Phosphino-decorated polymer immobilised ionic liquid phase stabilised palladium nanoparticles (PdNP@PPh2-PIILP) and their PEGylated counterparts (PdNP@PPh2-PEGPIILP) are remarkably active and exceptionally selective catalysts for the aqueous phase hydrogenation of α,β-unsaturated aldehydes, ketones, esters and nitriles with PdNP@PPh2-PEGPIILP giving complete conversion and 100% selectivity for reduction of the CC bond, under mild conditions. This is the most selective PdNP-based system to be reported for the aqueous phase hydrogenation of this class of substrates.
- Doherty,Knight,Backhouse,Abood,Alshaikh,Fairlamb,Bourne,Chamberlain,Stones
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supporting information
p. 1635 - 1641
(2017/06/05)
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- Practical Aerobic Oxidation of Alcohols: A Ligand-Enhanced 2,2,6,6-Tetramethylpiperidine-1-oxy/Manganese Nitrate Catalyst System
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A highly efficient, ligand-enhanced 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO)/Mn(NO3)2 catalyst system for the aerobic oxidation of alcohols is described. From the series of coordinating ligands studied herein, 2-picolinic acid (PyCOOH) improves the catalytic activity of TEMPO/Mn(NO3)2 remarkably. Under ambient air at room temperature in acetic acid, the ligand-enhanced catalyst converts aliphatic and benzylic primary alcohols that bear various functional groups into their respective aldehydes with near quantitative conversions. The applicability of the catalyst for convenient preparative synthesis was demonstrated by conducting oxidations on a gram scale. A change of TEMPO to the sterically less demanding 9-azabicyclo[3.3.1]nonane N-oxyl results in a Mn catalyst that is also able to oxidize secondary alcohols to ketones. Mechanistic studies showed that alcohols are oxidized by the oxoammonium cation derived from the nitroxyl radical. The active oxidant is regenerated by Mn(NO3)2, and this process is greatly promoted by the coordination of PyCOOH to Mn.
- Lagerblom, Kalle,Lagerspets, Emi,Keskiv?li, Juha,Cook, Chris,Ekholm, Filip,Parviainen, Arno,Repo, Timo
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p. 3880 - 3887
(2017/09/28)
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- Dehydrogenation of primary aliphatic alcohols by Au/TiO2 photocatalysts
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Dehydrogenation reaction of primary aliphatic alcohols to aldehydes and molecular hydrogen was achieved under UV-vis light irradiation in the presence of gold-loaded titanium dioxide (Au/TiO2) photocatalysts.
- Shibata, Masaki,Nagata, Ryoko,Saito, Susumu,Naka, Hiroshi
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supporting information
p. 580 - 582
(2017/04/03)
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- Synthesis, Characterization, and Relative Study on the Catalytic Activity of Zinc Oxide Nanoparticles Doped MnCO3, -MnO2, and -Mn2O3 Nanocomposites for Aerial Oxidation of Alcohols
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Zinc oxide nanoparticles doped manganese carbonate catalysts [X% ZnOx-MnCO3] (where X = 0-7) were prepared via a facile and straightforward coprecipitation procedure, which upon different calcination treatments yields different manganese oxides, that is, [X% ZnOx-MnO2] and [X% ZnOx-Mn2O3]. A comparative catalytic study was conducted to evaluate the catalytic efficiency between carbonates and oxides for the selective oxidation of secondary alcohols to corresponding ketones using molecular oxygen as a green oxidizing agent without using any additives or bases. The prepared catalysts were characterized by different techniques such as SEM, EDX, XRD, TEM, TGA, BET, and FTIR spectroscopy. The 1% ZnOx-MnCO3 calcined at 300°C exhibited the best catalytic performance and possessed highest surface area, suggesting that the calcination temperature and surface area play a significant role in the alcohol oxidation. The 1% ZnOx-MnCO3 catalyst exhibited superior catalytic performance and selectivity in the aerial oxidation of 1-phenylethanol, where 100% alcohol conversion and more than 99% product selectivity were obtained in only 5 min with superior specific activity (48 mmol·g-1·h-1) and 390.6 turnover frequency (TOF). The specific activity obtained is the highest so far (to the best of our knowledge) compared to the catalysts already reported in the literatures used for the oxidation of 1-phenylethanol. It was found that ZnOx nanoparticles play an essential role in enhancing the catalytic efficiency for the selective oxidation of alcohols. The scope of the oxidation process is extended to different types of alcohols. A variety of primary, benzylic, aliphatic, allylic, and heteroaromatic alcohols were selectively oxidized into their corresponding carbonyls with 100% convertibility without overoxidation to the carboxylic acids under base-free conditions.
- Assal, Mohamed E.,Kuniyil, Mufsir,Shaik, Mohammed Rafi,Khan, Mujeeb,Al-Warthan, Abdulrahman,Siddiqui, Mohammed Rafiq H.,Adil, Syed Farooq
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- Manufacture of Citronellal by the Rhodium-Catalyzed Homogeneous Hydrogenation of Neral
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The highly chemoselective hydrogenation of neral affording citronellal is described. The reaction has been conducted with homogeneous rhodium complexes. Among the set of ancillary diphosphane ligands tested, Xantphos was found to be superior. The relevant precatalyst has been generated from neutral metal sources such as Rh(acac)(CO)2 or the carbon monoxide-free rhodium source Rh(acac)(cod) in the absence of any base. A high activity and chemoselectivity in favor of the desired citronellal is achieved at 0.1 MPa and room temperature. Under the same conditions, geranial is also reduced to citronellal. The addition of carbon monoxide to the hydrogen stream as used in an industrial process is not necessary. (Figure presented.).
- Holz, Jens,Doerfelt, Stephan,B?rner, Armin
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p. 4379 - 4387
(2017/12/26)
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- Enhanced Ene-Reductase Activity through Alteration of Artificial Nicotinamide Cofactor Substituents
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The reduction of activated C=C double bonds is an important reaction in synthetic chemistry owing to the potential formation of up to two new stereogenic centers. Artificial nicotinamide cofactors were recently presented as alternative suppliers of hydride equivalents needed for alkene reduction. To study the effect of cofactors on the reduction of activated alkenes, a set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthetic cofactors on enzyme activity of four ene reductases are outlined in this study, where the cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH. Artificial nicotinamide cofactor substituents: A set of N-substituted synthetic nicotinamide cofactors with differing oxidation potentials were synthesized and their electrochemical and kinetic behavior was studied. The effects of the synthesized cofactors on the enzyme activity of four ene reductases are outlined. The cofactor mimic with an N-substituted 4-hydroxy-phenyl residue led to a sixfold higher vmax relative to the natural cofactor NADH.
- L?w, Sebastian A.,L?w, Isabell M.,Weissenborn, Martin J.,Hauer, Bernhard
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p. 911 - 915
(2016/03/15)
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- Method for preparing chiral citronellal through citral catalytic asymmetric hydrogenation
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The invention relates to a method for preparing chiral citronellal through citral catalytic asymmetric hydrogenation in the technical field of chemical engineering. Under the effect of additives such as sodium iodide, tetraoctyl ammonium bromide and phenyltriethylammonium chloride, E-type and/or Z-type citral is catalyzed by chiral rhodium complex and asymmetrically hydrogenated into R or S chiral citronellal. In addition, E-type or Z-type citral can be catalyzed into chiral citronellal of the same required structure by changing chirality of chiral catalysts. Thus, citral of all structures can be completely converted into chiral rhodium of one required structure. The reaction method is mild in condition, easy and convenient to operate, capable of achieving good reaction yield and reaction efficiency and good in application effect.
- -
-
Paragraph 0154; 0155
(2016/10/07)
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- Surface Lewis acid-promoted copper-based nanocatalysts for highly efficient and chemoselective hydrogenation of citral to unsaturated allylic alcohols
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Chemoselective hydrogenation of α,β-unsaturated aldehydes or ketones to unsaturated alcohols (UAs) is one of the key processes for the production of various important intermediate chemicals. In the present work, well-dispersed ZnO-promoted supported copper nanocatalysts were generated from Cu-Zn-Al layered double hydroxide (CuZnAl-LDH) precursors for liquid-phase chemoselective hydrogenation of citral to allylic alcohols (geraniol and nerol isomers). A series of characterizations including XRD, TEM, STEM, XPS, H2-TPR, and Py-IR demonstrated that the microstructure and catalytic performance of as-formed Cu-based nanocatalysts were significantly affected by the incorporation of Zn into catalyst precursors. It was found that the addition of more ZnO to catalysts could result in better metal dispersion and an increase in the surface Cu+/(Cu+ + Cu0) ratio and surface Lewis acid sites. In liquid-phase chemoselective hydrogenation of citral, a high selectivity toward allylic alcohols (>75%) at complete citral conversion was achieved successfully on as-formed non-noble-metal Cu-based nanocatalysts with a Cu/Zn molar ratio of 2:1 under mild reaction conditions (e.g. 80°C, 1.0 MPa). The high efficiency of the catalysts was attributed mainly to both the synergism between Cu0 and Cu+ species and the promotion of surface Lewis acid sites, thereby improving the dissociation of hydrogen and facilitating the adsorption of the citral molecule and the following activation of the carbonyl group during the citral hydrogenation.
- Li, Wei,Fan, Guoli,Yang, Lan,Li, Feng
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p. 2337 - 2348
(2016/04/26)
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- Synthesis of Co-Sn intermetallic nanocatalysts toward selective hydrogenation of citral
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In this work, three supported Co-Sn intermetallic compound (IMC) catalysts (Co2.9Sn2, CoSn and CoSn2) with a particle size of ~20 nm were prepared via a facile hydrotalcite approach, and their catalytic performances were evaluated in the selective hydrogenation of citral to unsaturated alcohols (geraniol and nerol). EXAFS, in situ CO-FTIR and DFT calculation results reveal that the introduction of Sn in Co-Sn IMCs dramatically optimizes the geometric and electronic structures of active Co, in which Sn isolates the Co active-site and electron transfer occurs from Sn to the Co atom. H2-TPD measurements indicate the presence of four different Co sites (labeled as α, β, γ and σ) on the surface of these IMCs; the sample of CoSn IMC shows the largest β/(γ + σ) ratio, which results in the highest selectivity toward unsaturated alcohols (SUA: 67.6%). DFT studies prove that the geometric and electronic effects of the CoSn IMC weaken the hydrogenation of the CC group, accounting for the largely enhanced hydrogenation selectivity of citral to unsaturated alcohols.
- Zhou, Junyao,Yang, Yusen,Li, Changming,Zhang, Shitong,Chen, Yudi,Shi, Shuxian,Wei, Min
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p. 12825 - 12832
(2018/06/26)
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- Long-chain NHC-stabilized RuNPs as versatile catalysts for one-pot oxidation/hydrogenation reactions
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The synthesis and catalytic activity of long-chain NHC-stabilized RuNPs are presented. Full characterization of these novel nanostructures including surface state studies show that the ligand influences the number and the location of Ru active sites which impacts the NP catalytic activity, especially in hydrogenation reactions. The high stability and versatility of these nanosystems make them successful catalysts for both oxidation and hydrogenation reactions that can even be performed successively in a one pot-fashion.
- Martínez-Prieto,Ferry,Rakers,Richter,Lecante,Philippot,Chaudret,Glorius
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supporting information
p. 4768 - 4771
(2016/04/09)
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- Two "classical" Old Yellow Enzymes from Chryseobacterium sp. CA49: Broad substrate specificity of Chr-OYE1 and limited activity of Chr-OYE2
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Two putative Old Yellow Enzyme (OYE) homologues, Chr-OYE1 and Chr-OYE2, were identified from the genome of Chryseobacterium sp. CA49 as new members of the "classical" subfamily. Chr-OYE1 and Chr-OYE2 were most closely related to the SYE4 from Shewanella oneidensis and NerA from Agrobacterium radiobacter with 41% and 45% identity, respectively. Both enzymes were expressed in Escherichia coli in soluble form, but their catalytic abilities as ene-reductases were quite different. Among the 19 substrate tested, Chr-OYE1 could catalyze the reduction of 18 of them including an ynone with excellent stereoselectivity for several prochiral ones, and its specific activity was roughly 1100-fold high than Chr-OYE2, which only catalyzed 3 of the substrates. After restoring the conserved tyrosine, Chr-OYE2 remained the same substrate spectrum, but showed significantly enhanced activity and stereoselectivity.
- Pei, Xiao-Qiong,Xu, Meng-Yu,Wu, Zhong-Liu
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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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- Selective hydrogenation of citral by noble metals supported on carbon xerogels: Catalytic performance and stability
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A series of monometallic Pt, Ir and Ru-catalysts deposited on carbon xerogel microspheres was prepared, exhaustively characterized and used in the selective hydrogenation of citral. A similar metal particle size is obtained in all cases after He-pretreatment, allowing the comparison between metals; the catalytic activity increases in the sense Ir 2-flow leading to an important loss of activity, especially for Ru-catalysts. Pt and Ir-catalysts are more selective than Ru-catalysts, reaching selectivity values to unsaturated alcohols of around 80%. Thus, in terms of yields to these valuable products Pt-catalysts seem to be the most appropriate active phase. Nevertheless, reutilization experiments showed that Ir-catalyst maintained a good performance while a severe deactivation is observed for Pt-catalysts. This fact is discussed on the basis of the different nature of the deposits formed during reaction.
- Bailón-García, Esther,Carrasco-Marín, Francisco,Pérez-Cadenas, Agustín F.,Maldonado-Hódar, Francisco J.
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- Effect of 2-propanol on the transfer hydrogenation of aldehydes by aqueous sodium formate using a rhodium(i)-sulfonated triphenylphosphine catalyst
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In water/2-propanol mixtures [RhCl(mtppms)3] (mtppms = monosulfonated triphenylphosphine) was an efficient catalyst for the selective C=C reduction of trans-3-phenyl-2-propenal (trans-cinnamaldehyde) by hydrogen transfer from formate at temperatures as low as 30 °C. An outstandingly high catalyst turnover frequency of 1214 h-1 was determined at 70 °C. A possible mechanism of the reaction is suggested on the basis of kinetic studies and 1H- and 31P-NMR spectroscopic identification of the major Rh(i) species in the reaction mixtures as cis-mer-[H2RhX(mtppms)3] (X = HCOO- or H2O). It was established that a large part but not all of the rate increase observed in water/2-propanol mixtures in comparison with systems with neat water as solvent was the consequence of complete dissolution of trans-cinnamaldehyde on the effect of the co-solvent. Nevertheless, the rate showed a significant further increase with increasing 2-propanol concentration even in homogeneous solution and this was ascribed to changes in the solvent structure. The high catalyst activity in this solvent mixture allowed the transfer hydrogenation of citral. Although good to excellent conversions were observed at 30-70 °C, a useful degree of selectivity in hydrogenation of C=C vs. C=O bonds could not be achieved.
- Kathó, ágnes,Szatmári, Imre,Papp, Gábor,Joó, Ferenc
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p. 339 - 344
(2015/11/24)
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- Direct synthesis of hybrid layered double hydroxide-carbon composites supported Pd nanocatalysts efficient in selective hydrogenation of citral
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This present study reports a facile one-pot strategy for the direct synthesis of hybrid layered double hydroxide (LDH)-carbon composites supported palladium nanocatalysts by the in situ reduction of PdCl42--intercalated MgAl-LDH combined with amorphous carbon under mild hydrothermal conditions. The results demonstrated that most of the Pd(II) species intercalated in the interlameller space of MgAl-LDH could be reduced in situ to metallic Pd0 species, and simultaneously, the hybrid structure of the LDH-C composites facilitated the formation of uniform Pd nanoparticles with small diameter, as well as the strong metal-support interactions. Furthermore, with the decreasing proportion of the LDH component in LDH-C composites, the average diameter of Pd nanoparticles decreased progressively and the metal-support interactions were weakened. The as-formed supported Pd nanocatalyst with Pd loading of 5.5 wt% was found to show a superior catalytic activity in the liquid-phase selective hydrogenation of citral than other supported Pd nanocatalysts, while the one with the Pd loading of 2.7 wt% yielded a much higher yield of citronellal (~80.0%) at 100% conversion. The catalytic performance of Pd nanocatalysts was proposed to be mainly related to both the metal-support interactions and the compositions of hybrid LDH-C composite supports.
- Han, Ruirui,Nan, Chunshi,Yang, Lan,Fan, Guoli,Li, Feng
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p. 33199 - 33207
(2015/04/27)
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- N,N,N′,N′-Tetramethylenediamine dioxide (TMEDAO2) facilitates atom economical/open atmosphere Ley-Griffith (TPAP) tandem oxidation-Wittig reactions
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N,N,N′,N′-Tetramethylethylenediamine dioxide (TMEDAO2) was explored as a more atom economical co-oxidant for the Ley-Griffith oxidation of alcohols to aldehydes. TMEDAO2 was found to selectivity oxidise benzylic and allylic alcohols in comparable yields to that of the standard Ley-Griffith co-oxidant (NMO). Importantly TMEDAO2 facilitated tandem Ley-Griffith-Wittig reactions with stabilised ylides, in good to excellent yields, without the requirement of anhydrous conditions.
- Read, Christopher D. G.,Moore, Peter W.,Williams, Craig M.
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supporting information
p. 4537 - 4540
(2015/09/15)
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- High density monolayer of diisocyanide on gold surface as a platform of supported Rh-catalyst for selective 1,4-hydrogenation of α,β- unsaturated carbonyl compounds
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A high density monolayer of diisocyanide on gold surface was utilized as a platform of supported Rh catalyst for selective 1,4-hydrogenation of α,β-unsaturated carbonyl compounds. The catalyst exhibited high turnover numbers in a range of 50-000 to 150-000 per Rh atom and showed steady catalyst performance over six recycle usages.
- Jagtap,Kaji,Fukuoka,Hara
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supporting information
p. 5046 - 5048
(2014/05/06)
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