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Catalysts, Volume 5, Issue 4 (December 2015), Pages 1636-2323

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Open AccessArticle Switching off H2O2 Decomposition during TS-1 Catalysed Epoxidation via Post-Synthetic Active Site Modification
Catalysts 2015, 5(4), 2309-2323; https://doi.org/10.3390/catal5042309
Received: 28 October 2015 / Revised: 9 December 2015 / Accepted: 16 December 2015 / Published: 21 December 2015
Cited by 5 | PDF Full-text (464 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Despite its widespread use, the Lewis acidic zeolite, TS-1, still exhibits several unfavourable properties, such as excessive H2O2 decomposition, which decrease its overall performance. In this manuscript, we demonstrate that post-synthetic modification of TS-1 with aqueous NH4HF2
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Despite its widespread use, the Lewis acidic zeolite, TS-1, still exhibits several unfavourable properties, such as excessive H2O2 decomposition, which decrease its overall performance. In this manuscript, we demonstrate that post-synthetic modification of TS-1 with aqueous NH4HF2 leads to modifications in epoxidation catalysis, which both improves the levels of epoxide selectivity obtained, and drastically minimises undesirable H2O2 decomposition. Through in situ spectroscopic study with UV-resonance enhanced Raman spectroscopy, we also observe a change in Ti site speciation, which occurs via the extraction of mononuclear [Ti(OSi)4] atoms, and which may be responsible for the changes in observed activity. Full article
(This article belongs to the Special Issue Zeolite Catalysis) Printed Edition available
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Open AccessArticle Experimental and Modeling Studies on the Conversion of Inulin to 5-Hydroxymethylfurfural Using Metal Salts in Water
Catalysts 2015, 5(4), 2287-2308; https://doi.org/10.3390/catal5042287
Received: 24 October 2015 / Revised: 12 December 2015 / Accepted: 14 December 2015 / Published: 21 December 2015
Cited by 2 | PDF Full-text (1021 KB) | HTML Full-text | XML Full-text
Abstract
Inulin, a plant polysaccharide consisting of mainly d-fructose units, is considered an interesting feed for 5-hydroxymethylfurfural (HMF), a top 12 bio-based chemical. We here report an exploratory experimental study on the use of a wide range of homogeneous metal salts as catalysts
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Inulin, a plant polysaccharide consisting of mainly d-fructose units, is considered an interesting feed for 5-hydroxymethylfurfural (HMF), a top 12 bio-based chemical. We here report an exploratory experimental study on the use of a wide range of homogeneous metal salts as catalysts for the conversion of inulin to HMF in water. Best results were obtained using CuCl2. Activity-pH relations indicate that the catalyst activity of CuCl2 is likely related to Lewis acidity and not to Brönsted acidity. The effects of process conditions on HMF yield for CuCl2 were systematically investigated and quantified using a central composite design (160–180 °C, an inulin loading between 0.05 and 0.15 g/mL, CuCl2 concentration in range of 0.005–0.015 M, and a reaction time between 10 and 120 min). The highest experimental HMF yield in the process window was 30.3 wt. % (39 mol %, 180 °C, 0.05 g/mL inulin, 0.005 M CuCl2 and a reaction time of 10 min). The HMF yields were modelled using non-linear, multi variable regression and good agreement between experimental data and model were obtained. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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Open AccessArticle Washcoat Deposition of Ni- and Co-ZrO2 Low Surface Area Powders onto Ceramic Open-Cell Foams: Influence of Slurry Formulation and Rheology
Catalysts 2015, 5(4), 2271-2286; https://doi.org/10.3390/catal5042271
Received: 29 September 2015 / Revised: 20 November 2015 / Accepted: 24 November 2015 / Published: 18 December 2015
Cited by 2 | PDF Full-text (844 KB) | HTML Full-text | XML Full-text
Abstract
The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams) was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while
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The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams) was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while a dip-coating technique was chosen for washcoat deposition on 30 PPI ceramic open-cell foams. The rheological behavior was explained on the bases of both porosity and actual powder density. It was proved that the use of multiple dippings fulfills flexibility requirements for washcoat load management. Multiple depositions with intermediate flash drying steps at 350 °C were carried out. Washcoat loads in the 2.5 to 22 wt. % range were obtained. Pore clogging was seldom observed in a limited extent in samples with high loading (>20 wt. %). Adhesion, evaluated by means of accelerated stress test in ultrasound bath, pointed out good results of all the deposited layers. Full article
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Open AccessArticle Heterogeneous Ru-Based Catalysts for One-Pot Synthesis of Primary Amines from Aldehydes and Ammonia
Catalysts 2015, 5(4), 2258-2270; https://doi.org/10.3390/catal5042258
Received: 10 November 2015 / Revised: 9 December 2015 / Accepted: 10 December 2015 / Published: 16 December 2015
Cited by 4 | PDF Full-text (169 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The direct reductive amination of carbonyl compounds with NH3 and H2 is an alternative route to produce primary amines in practical production. The search for efficient and selective catalysts has attracted great interest. In the present work, the reductive amination of heptaldehyde with
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The direct reductive amination of carbonyl compounds with NH3 and H2 is an alternative route to produce primary amines in practical production. The search for efficient and selective catalysts has attracted great interest. In the present work, the reductive amination of heptaldehyde with NH3 was investigated over a Ru-based catalyst. The product selectivities were found to be related with the supports of Ru. The alumina with spinel structure (γ-Al2O3, θ-Al2O3)-supported Ru catalysts exhibited selectivity favoring primary amines (94% yield) at 100% heptaldehyde conversion under optimal conditions. Purely basic (MgO, CaO) and relative acidic (Nb2O5, SnO2, MCM-41, HZSM-5) supports showed relatively poor selectivity towards primary amines (0%–53% yield). The reductive amination mechanism was also proposed. The Schiff base N-[heptylene]heptyl-1-amine was a key intermediate. Ru/γ-Al2O3 was shown to be an excellent hydrogenolysis catalyst to selectively produce primary amine by amination and hydrogenolysis of N-[heptylene]heptyl-1-amine. Full article
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Open AccessArticle High-Throughput Screening of Heterogeneous Catalysts for the Conversion of Furfural to Bio-Based Fuel Components
Catalysts 2015, 5(4), 2244-2257; https://doi.org/10.3390/catal5042244
Received: 15 November 2015 / Revised: 7 December 2015 / Accepted: 8 December 2015 / Published: 16 December 2015
Cited by 5 | PDF Full-text (301 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The one-pot catalytic reductive etherification of furfural to 2-methoxymethylfuran (furfuryl methyl ether, FME), a valuable bio-based chemical or fuel, is reported. A large number of commercially available hydrogenation heterogeneous catalysts based on nickel, copper, cobalt, iridium, palladium and platinum catalysts on various support
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The one-pot catalytic reductive etherification of furfural to 2-methoxymethylfuran (furfuryl methyl ether, FME), a valuable bio-based chemical or fuel, is reported. A large number of commercially available hydrogenation heterogeneous catalysts based on nickel, copper, cobalt, iridium, palladium and platinum catalysts on various support were evaluated by a high-throughput screening approach. The reaction was carried out in liquid phase with a 10% w/w furfural in methanol solution at 50 bar of hydrogen. Among all the samples tested, carbon-supported noble metal catalysts were found to be the most promising in terms of productivity and selectivity. In particular, palladium on charcoal catalysts show high selectivity (up to 77%) to FME. Significant amounts of furfuryl alcohol (FA) and 2-methylfuran (2-MF) are observed as the major by-products. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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Open AccessArticle Zeolite Catalysts for Phenol Benzoylation with Benzoic Acid: Exploring the Synthesis of Hydroxybenzophenones
Catalysts 2015, 5(4), 2223-2243; https://doi.org/10.3390/catal5042223
Received: 14 November 2015 / Revised: 5 December 2015 / Accepted: 9 December 2015 / Published: 16 December 2015
Cited by 4 | PDF Full-text (807 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites
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In this paper, we report on the reaction of phenol benzoylation with benzoic acid, which was carried out in the absence of solvent. The aim of this reaction is the synthesis of hydroxybenzophenones, which are important intermediates for the chemical industry. H-beta zeolites offered superior performance compared to H-Y, with a remarkably high conversion of phenol and high yields to the desired compounds, when using a stoichiometric amount of benzoic acid. It was found that the reaction mechanism did not include the intramolecular Fries rearrangement of the primary product phenyl benzoate, but indeed, the bimolecular reaction between phenyl benzoate and phenol mainly contributed to the formation of hydroxybenzophenones. The product distribution was greatly affected by the presence of Lewis-type acid sites in H-beta; it was suggested that the interaction between the aromatic ring and the electrophilic Al3+ species led to the preferred formation of o-hydroxybenzophenone, because of the decreased charge density on the C atom at the para position of the phenolic ring. H-Y zeolites were efficient than H-beta in phenyl benzoate transformation into hydroxybenzophenones. Full article
(This article belongs to the Special Issue Zeolite Catalysis) Printed Edition available
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Open AccessReview Zeolite Membranes in Catalysis—From Separate Units to Particle Coatings
Catalysts 2015, 5(4), 2161-2222; https://doi.org/10.3390/catal5042161
Received: 31 October 2015 / Revised: 2 December 2015 / Accepted: 4 December 2015 / Published: 16 December 2015
Cited by 13 | PDF Full-text (1733 KB) | HTML Full-text | XML Full-text
Abstract
Literature on zeolite membranes in catalytic reactions is reviewed and categorized according to membrane location. From this perspective, the classification is as follows: (i) membranes spatially decoupled from the reaction zone; (ii) packed bed membrane reactors; (iii) catalytic membrane reactors and (iv) zeolite
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Literature on zeolite membranes in catalytic reactions is reviewed and categorized according to membrane location. From this perspective, the classification is as follows: (i) membranes spatially decoupled from the reaction zone; (ii) packed bed membrane reactors; (iii) catalytic membrane reactors and (iv) zeolite capsuled catalyst particles. Each of the resulting four chapters is subdivided by the kind of reactions performed. Over the whole sum of references, the advantage of zeolite membranes in catalytic reactions in terms of conversion, selectivity or yield is evident. Furthermore, zeolite membrane preparation, separation principles as well as basic considerations on membrane reactors are discussed. Full article
(This article belongs to the Special Issue Zeolite Catalysis) Printed Edition available
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Open AccessArticle Jet-Fuel Range Hydrocarbons from Biomass-Derived Sorbitol over Ni-HZSM-5/SBA-15 Catalyst
Catalysts 2015, 5(4), 2147-2160; https://doi.org/10.3390/catal5042147
Received: 10 November 2015 / Revised: 7 December 2015 / Accepted: 8 December 2015 / Published: 15 December 2015
Cited by 11 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Aromatics and cyclic-hydrocarbons are the significant components of jet fuel with high energy-density. However, conventional technologies for bio-fuel production cannot produce these products without further aromatization and isomerization. In this work, renewable liquid fuel with high content of aromatics and cyclic-hydrocarbons was obtained
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Aromatics and cyclic-hydrocarbons are the significant components of jet fuel with high energy-density. However, conventional technologies for bio-fuel production cannot produce these products without further aromatization and isomerization. In this work, renewable liquid fuel with high content of aromatics and cyclic-hydrocarbons was obtained through aqueous catalytic conversion of biomass sorbitol over Ni-HZSM-5/SBA-15 catalyst. Texture characteristics of the catalyst were determined by physisorption of N2, which indicated its bimodal pore structures were microporous (HZSM-5, pore width: 0.56 nm) and mesoporous (SBA-15, pore width: 8 nm). The surface acidity included weak and strong acid sites, predominantly Lewis type, and was further confirmed by the NH3-TPD and Py-IR analysis. The catalytic performances were tested in a fixed-bed reactor under the conditions of 593 K, WHSV of 0.75 h−1, GHSV of 2500 h−1 and 4.0 MPa of hydrogen pressure, whereby oil yield of 40.4 wt. % with aromatics and cyclic-hydrocarbons content of 80.0% was obtained. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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Open AccessArticle Facile Synthesis of Yolk/Core-Shell Structured TS-1@Mesosilica Composites for Enhanced Hydroxylation of Phenol
Catalysts 2015, 5(4), 2134-2146; https://doi.org/10.3390/catal5042134
Received: 26 October 2015 / Revised: 23 November 2015 / Accepted: 23 November 2015 / Published: 14 December 2015
Cited by 6 | PDF Full-text (719 KB) | HTML Full-text | XML Full-text
Abstract
In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process,
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In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, while the yolk-shell TS-1@mesosilica composite was prepared using a resorcinol-formaldehyde resin (RF) middle-layer as the sacrificial template. The obtained materials were characterized by X-ray diffraction (XRD), N2 sorption, Fourier transform infrared spectoscopy (FT-IR) UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results showed that these samples possessed highly uniform yolk/core-shell structures, high surface area (560–700 m2 g−1) and hierarchical pore structures from oriented mesochannels to zeolite micropores. Importantly, owing to their unique structural properties, these composites exhibited enhanced activity, and also selectivity in the phenol hydroxylation reaction. Full article
(This article belongs to the Special Issue Zeolite Catalysis) Printed Edition available
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Open AccessArticle Selective Production of Aromatics from 2-Octanol on Zinc Ion-Exchanged MFI Zeolite Catalysts
Catalysts 2015, 5(4), 2122-2133; https://doi.org/10.3390/catal5042122
Received: 13 November 2015 / Revised: 30 November 2015 / Accepted: 30 November 2015 / Published: 10 December 2015
Cited by 1 | PDF Full-text (358 KB) | HTML Full-text | XML Full-text
Abstract
The aromatization of 2-octanol derived from castor oil as a byproduct in the formation of sebacic acid was investigated on various zeolite catalysts. Zn ion-exchanged MFI (ZSM-5) zeolites with small silica/alumina ratios and zinc contents of 0.5 to 2.0 wt. % were determined
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The aromatization of 2-octanol derived from castor oil as a byproduct in the formation of sebacic acid was investigated on various zeolite catalysts. Zn ion-exchanged MFI (ZSM-5) zeolites with small silica/alumina ratios and zinc contents of 0.5 to 2.0 wt. % were determined to exhibit good and stable activity for the reaction at 623 to 823 K. The yield of aromatics was 62% at 773 K and the space velocity 350 to 1400 h−1. The temperature and contact time dependences of the product distributions indicated the reaction pathways of 2-octanol→dehydration to 2-octene→decomposition to C5 and C3 compounds→further decomposition to small alkanes and alkenes→aromatization with dehydrogenation. Alcohols with carbon numbers of 5 to 8 exhibited similar distributions of products compared to 2-octanol, while corresponding carbonyl compounds demonstrated different reactivity. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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Open AccessEditorial Electrocatalysis in Fuel Cells
Catalysts 2015, 5(4), 2115-2121; https://doi.org/10.3390/catal5042115
Received: 1 December 2015 / Revised: 4 December 2015 / Accepted: 7 December 2015 / Published: 9 December 2015
Cited by 3 | PDF Full-text (133 KB) | HTML Full-text | XML Full-text
Abstract
Low temperature fuel cells are expected to come into widespread commercial use in the areas of transportation and stationary and portable power generation, and thus will help solve energy shortage and environmental issues. [...] Full article
(This article belongs to the Special Issue Electrocatalysis in Fuel Cells) Printed Edition available
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Open AccessArticle Adsorption and Diffusion of Xylene Isomers on Mesoporous Beta Zeolite
Catalysts 2015, 5(4), 2098-2114; https://doi.org/10.3390/catal5042098
Received: 31 October 2015 / Revised: 25 November 2015 / Accepted: 30 November 2015 / Published: 8 December 2015
Cited by 4 | PDF Full-text (396 KB) | HTML Full-text | XML Full-text
Abstract
A systematic and detailed analysis of adsorption and diffusion properties of xylene isomers over Beta zeolites with different mesoporosity was conducted. Adsorption isotherms of xylene isomers over microporous and mesoporous Beta zeolites through gravimetric methods were applied to investigate the impact of mesopores
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A systematic and detailed analysis of adsorption and diffusion properties of xylene isomers over Beta zeolites with different mesoporosity was conducted. Adsorption isotherms of xylene isomers over microporous and mesoporous Beta zeolites through gravimetric methods were applied to investigate the impact of mesopores inside Beta zeolites on the adsorption properties of xylene isomers in the pressure range of lower 20 mbar. It is seen that the adsorption isotherms of three xylene isomers over microporous and mesoporous Beta zeolites could be successfully described by the single-site Toth model and the dual-site Toth model, respectively. The enhanced adsorption capacities and decreased Henry’s constants (KH) and the initial heats of adsorption (Qst) for the all xylene isomers are observed after the introduction of mesopores in the zeolites. For three xylene isomers, the order of Henry’s constant is o-xylene > m-xylene > p-xylene, whereas the adsorption capacities of Beta zeolite samples for xylene isomers execute the following order of o-xylene > p-xylene > m-xylene, due to the comprehensive effects from the molecular configuration and electrostatic interaction. At the same time, the diffusion properties of xylene isomers in the mesoporous Beta zeolites were also studied through the desorption curves measured by the zero length column (ZLC) method at 333–373 K. It turned out that the effective diffusion time constant (Deff/R2) is a growing trend with the increasing mesoporosity, whereas the tendency of the activation energy is just the reverse, indicating the contribution of mesopores to facilitate molecule diffusion by shortening diffusion paths and reducing diffusion resistances. Moreover, the diffusivities of three xylene isomers in all Beta zeolites follow an order of p-xylene > m-xylene > o-xylene as opposed to KH, conforming the significant effects of adsorbate-adsorbent interaction on the diffusion. Full article
(This article belongs to the Special Issue Zeolite Catalysis) Printed Edition available
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Open AccessArticle Co-Pyrolysis Behaviors of the Cotton Straw/PP Mixtures and Catalysis Hydrodeoxygenation of Co-Pyrolysis Products over Ni-Mo/Al2O3 Catalyst
Catalysts 2015, 5(4), 2085-2097; https://doi.org/10.3390/catal5042085
Received: 4 October 2015 / Revised: 11 November 2015 / Accepted: 11 November 2015 / Published: 8 December 2015
Cited by 6 | PDF Full-text (316 KB) | HTML Full-text | XML Full-text
Abstract
The doping of PP (polypropylene) with cotton straw improved the bio-oil yield, which showed there was a synergy in the co-pyrolysis of the cotton straw and PP at the range of 380–480 °C. In a fixed-bed reactor, model compounds and co-pyrolysis products were
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The doping of PP (polypropylene) with cotton straw improved the bio-oil yield, which showed there was a synergy in the co-pyrolysis of the cotton straw and PP at the range of 380–480 °C. In a fixed-bed reactor, model compounds and co-pyrolysis products were used for reactants of hydrodeoxygenation (HDO) over Ni-Mo/Al2O3. The deoxygenation rate of model compounds decreased over Ni-Mo/Al2O3 in the following order: alcohol > aldehyde > acetic acid > ethyl acetate. The upgraded oil mainly consisted of C11 alkane. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass)
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Open AccessArticle Microbial Stereoselective One-Step Conversion of Diols to Chiral Lactones in Yeast Cultures
Catalysts 2015, 5(4), 2068-2084; https://doi.org/10.3390/catal5042068
Received: 5 November 2015 / Revised: 25 November 2015 / Accepted: 30 November 2015 / Published: 8 December 2015
Cited by 1 | PDF Full-text (216 KB) | HTML Full-text | XML Full-text
Abstract
It has been shown that whole cells of different strains of yeast catalyze stereoselective oxidation of meso diols to the corresponding chiral lactones. Among screening-scale experiments, Candida pelliculosa ZP22 was selected as the most effective biocatalyst for the oxidation of monocyclic diols 3a–b
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It has been shown that whole cells of different strains of yeast catalyze stereoselective oxidation of meso diols to the corresponding chiral lactones. Among screening-scale experiments, Candida pelliculosa ZP22 was selected as the most effective biocatalyst for the oxidation of monocyclic diols 3a–b with respect to the ratio of high conversion to stereoselectivity. This strain was used in the preparative oxidation, affording enantiomerically-enriched isomers of lactones: (+)-(3aR,7aS)-cis-hexahydro-1(3H) -isobenzofuranone (2a) and (+)-(3aS,4,7,7aR)-cis-tetrahydro-1(3H)-isobenzofuranone (2b). Scaling up the culture growth, as well as biotransformation conditions has been successfully accomplished. Among more bulky substrates, bicyclic diol 3d was totally converted into enantiomerically-pure exo-bridged (+)-(3aR,4S,7R,7aS)-cis-tetrahydro-4,7-methanoisobenzofuran -1(3H)-one (2d) by Yarrovia lipolytica AR71. Microbial oxidation of diol 3f by Candida sake AM908 and Rhodotorula rubra AM4 afforded optically-pure cis-3-butylhexahydro-1(3H) -isobenzofuranone (2f), however with low conversion. Full article
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Open AccessCommunication Ionic Liquids as Carbene Catalyst Precursors in the One-Pot Four-Component Assembly of Oxo Triphenylhexanoates (OTHOs)
Catalysts 2015, 5(4), 2052-2067; https://doi.org/10.3390/catal5042052
Received: 24 October 2015 / Revised: 18 November 2015 / Accepted: 18 November 2015 / Published: 27 November 2015
Cited by 3 | PDF Full-text (335 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Ionic liquids (ILs) are a convenient and inexpensive source of N-heterocyclic carbenes (NHCs). In this study, dialkyl imidazolium-based ILs are used as carbene precursors in a four-component synthesis of oxo triphenylhexanoates (OTHOs), where it was found that IL outperformed commonly used NHC precatalysts
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Ionic liquids (ILs) are a convenient and inexpensive source of N-heterocyclic carbenes (NHCs). In this study, dialkyl imidazolium-based ILs are used as carbene precursors in a four-component synthesis of oxo triphenylhexanoates (OTHOs), where it was found that IL outperformed commonly used NHC precatalysts in terms of reaction efficiency. The reaction is highly stereoselective, delivering the anti-diastereomer (20:1 dr), and the OTHOs can be obtained in high-to-excellent yields. By virtue of the four-component reaction-setup, facile construction of the OTHO scaffold with a diverse set of functional groups (21 examples) can be achieved. In the context of sustainability, the IL can be recovered and reused several times without affecting selectivity or yield. Moreover, most compounds can be isolated by precipitation and filtration, mitigating the use of solvent-demanding chromatography. Full article
(This article belongs to the Special Issue Ionic Liquids in Catalysis 2015)
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