- Nickel-Catalyzed Arylation of C(sp3)-O Bonds in Allylic Alkyl Ethers with Organoboron Compounds
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A nickel-catalyzed cross-coupling of allylic alkyl ethers with organoboron compounds through the cleavage of the inert C(sp3)-O(alkyl) bonds is described. Several types of allylic alkyl ethers can be coupled with various boronic acids or their derivatives to give the corresponding products in good to excellent yields with wide functional group tolerance and excellent regioselectivity. The gram-scale reaction and late-stage modification of biologically active compounds further prove the practicality of this synthetic method.
- Li, Xiaowei,Li, Yuxiu,Zhang, Zhong,Shi, Xiaolin,Liu, Ruihua,Wang, Zemin,Li, Xiangqian,Shi, Dayong
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supporting information
p. 6612 - 6616
(2021/09/02)
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- Pauson-Khand Reactions with Concomitant C?O Bond Cleavage for the Preparation of 5,5- 5,6- and 5,7-Bicyclic Ring Systems
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Pauson-Khand reactions (PKR) with concomitant C?O bond cleavage have been developed for construction of 5,5- 5,6- and 5,7-bicyclic ring systems bearing complex stereochemistry. The chemistry generates intermolecular PKR-type products in an absolute regio- and stereochemical control which is hardly achievable through real intermolecular Pauson-Khand reactions. A mechanism for this Pauson-Khand reaction has been proposed based on deuterium labelling experiments. (Figure presented.).
- Ma, Ding,Hu, Naifeng,Ao, Junli,Zang, Shaoli,Yu, Guo,Liang, Guangxin
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supporting information
p. 1887 - 1891
(2021/02/26)
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- Discovery and Engineering of Bacterial (?)-Isopiperitenol Dehydrogenases to Enhance (?)-Menthol Precursor Biosynthesis
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Microbial synthesis of (?)-menthol, a compound of plant origin, is of great importance because of the high demand for this product and related sustainability issues. However, the total biosynthesis of (?)-menthol from easily available feedstocks like (?)-limonene by engineered microbial hosts is stalled by the poor protein expression or activity of several enzymes from the native (?)-menthol biosynthesis pathway of mint (Mentha piperita). Among these unsatisfied steps, (?)-isopiperitenol dehydrogenase (IPDH) catalyzed oxidation reaction of (?)-trans-isopiperitenol was one of the bottlenecks that need to be optimized. In this work, two novel bacterial enzymes with IPDH activity were discovered to replace their inefficient counterpart from plant cells in microbial (?)-menthol synthesis. Two key residues in PaIPDH from Pseudomonas aeruginosa were mutated to PaIPDHE95F/Y199V with 4.4-fold improved specific activity than PaIPDH. The mechanism for the beneficial mutations was elucidated by molecular dynamics simulations. PaIPDHE95F/Y199V was used to synthesize (?)-isopiperitenone from (?)-limonene in vivo via a self-sufficient cofactor cascade enzyme reaction, affording a 3.7-fold enhanced titer of (?)-isopiperitenone compared with that obtained using the original mint IPDH (MpIPDH). The bacterial enzyme PaIPDHE95F/Y199V can be applied in the future for constructing a more efficient artificial pathway to biosynthesize (?)-menthol in a microbial whole-cell system. (Figure presented.).
- Zhan, Jing-Ru,Shou, Chao,Zheng, Yu-Cong,Chen, Qi,Pan, Jiang,Li, Chun-Xiu,Xu, Jian-He
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supporting information
p. 3973 - 3982
(2021/07/02)
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- Tuning of α-Silyl Carbocation Reactivity into Enone Transposition: Application to the Synthesis of Peribysin D, E-Volkendousin, and E-Guggulsterone
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A reliable method for enone transposition has been developed with the help of silyl group masking. Enantio-switching, substituent shuffling, and Z-selectivity are the highlights of the method. The developed method was applied for the first total synthesis of peribysin D along with its structural revision. Formal synthesis of E-guggulsterone and E-volkendousin was also claimed using a short sequence.
- Athawale, Paresh R.,Zade, Vishal M.,Rama Krishna, Gamidi,Reddy, D. Srinivasa
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p. 6642 - 6647
(2021/09/02)
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- A sustainable approach towards solventless organic oxidations catalyzed by polymer immobilized Nb(V)-peroxido compounds with H2O2 as oxidant
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New heterogeneous catalysts comprising of peroxidoniobium(V) complexes immobilized on amino acid grafted cross-linked poly(styrene-divinylbenzene) resin has been developed. Results of FTIR, Raman, NMR, XPS, XRD, EDX, SEM, BET, TGA, and elemental analysis confirmed the successful anchoring of triperoxidoniobium(V), [Nb(O2)3]? species to the host polymer via the pendant amino acid groups. The supported catalysts exhibited excellent performance in epoxidation of styrene and a range of cyclic and terpenic compounds under environmentally acceptable solvent-free condition, with aqueous H2O2 as oxidant. The catalytic protocols provided excellent conversion to the desired epoxide (up to 100%) with selectivity > 99%, TON as high as 1000, and high H2O2 utilization efficiency (92–97%). Moreover, the catalysts efficiently facilitated chemoselective solvent-free oxidation of a variety of thioethers to sulfones at room temperature. Simple operational strategy, easy recyclability for multiple reaction cycles with the consistent activity-selectivity profile are the additional significant attributes of the developed catalytic processes.
- Ahmed, Kabirun,Gogoi, Sandhya Rani,Islam, Nashreen S.,Saikia, Gangutri,Sultana, Sazida Yasmin,Talukdar, Hiya
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- Tailoring Lewis/Br?nsted acid properties of MOF nodesviahydrothermal and solvothermal synthesis: simple approach with exceptional catalytic implications
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The Lewis/Br?nsted catalytic properties of the Metal-Organic Framework (MOF) nodes can be tuned by simply controlling the solvent employed in the synthetic procedure. In this work, we demonstrate that Hf-MOF-808 can be prepared from a material with a higher amount of Br?nsted acid sites,viamodulated hydrothermal synthesis, to a material with a higher proportion of unsaturated Hf Lewis acid sites,viamodulated solvothermal synthesis. The Lewis/Br?nsted acid properties of the resultant metallic clusters have been studied by different characterization techniques, including XAS, FTIR and NMR spectroscopies, combined with a DFT study. The different nature of the Hf-MOF-808 materials allows their application as selective catalysts in different target reactions requiring Lewis, Br?nsted or Lewis-Br?nsted acid pairs.
- Bohigues, Benjamin,Boronat, Mercedes,Corma, Avelino,Lopes, Christian W.,Meira, Débora M.,Moliner, Manuel,Rojas-Buzo, Sergio
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p. 10106 - 10115
(2021/08/04)
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- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
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Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
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supporting information
p. 247 - 257
(2020/02/04)
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Artificial Light-Harvesting Complexes Enable Rieske Oxygenase Catalyzed Hydroxylations in Non-Photosynthetic cells
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In this study, we coupled a well-established whole-cell system based on E. coli via light-harvesting complexes to Rieske oxygenase (RO)-catalyzed hydroxylations in vivo. Although these enzymes represent very promising biocatalysts, their practical applicability is hampered by their dependency on NAD(P)H as well as their multicomponent nature and intrinsic instability in cell-free systems. In order to explore the boundaries of E. coli as chassis for artificial photosynthesis, and due to the reported instability of ROs, we used these challenging enzymes as a model system. The light-driven approach relies on light-harvesting complexes such as eosin Y, 5(6)-carboxyeosin, and rose bengal and sacrificial electron donors (EDTA, MOPS, and MES) that were easily taken up by the cells. The obtained product formations of up to 1.3 g L?1 and rates of up to 1.6 mm h?1 demonstrate that this is a comparable approach to typical whole-cell transformations in E. coli. The applicability of this photocatalytic synthesis has been demonstrated and represents the first example of a photoinduced RO system.
- Bloh, Jonathan Z.,Burek, Bastien O.,Feyza ?zgen, F.,Kourist, Robert,Runda, Michael E.,Schmidt, Sandy,Wied, Peter
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p. 3982 - 3987
(2020/02/04)
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- Selective Catalytic Synthesis of 1,2- and 8,9-Cyclic Limonene Carbonates as Versatile Building Blocks for Novel Hydroxyurethanes
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The selective catalytic synthesis of limonene-derived monofunctional cyclic carbonates and their subsequent functionalisation via thiol–ene addition and amine ring-opening is reported. A phosphotungstate polyoxometalate catalyst used for limonene epoxidation in the 1,2-position is shown to also be active in cyclic carbonate synthesis, allowing a two-step, one-pot synthesis without intermittent epoxide isolation. When used in conjunction with a classical halide catalyst, the polyoxometalate increased the rate of carbonation in a synergistic double-activation of both substrates. The cis isomer is shown to be responsible for incomplete conversion and by-product formation in commercial mixtures of 1,2-limomene oxide. Carbonation of 8,9-limonene epoxide furnished the 8,9-limonene carbonate for the first time. Both cyclic carbonates underwent thiol–ene addition reactions to yield linked di-monocarbonates, which can be used in linear non-isocyanate polyurethanes synthesis, as shown by their facile ring-opening with N-hexylamine. Thus, the selective catalytic route to monofunctional limonene carbonates gives straightforward access to monomers for novel bio-based polymers.
- Maltby, Katarzyna A.,Hutchby, Marc,Plucinski, Pawel,Davidson, Matthew G.,Hintermair, Ulrich
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supporting information
p. 7405 - 7415
(2020/05/25)
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- Selective Allylic Oxidation of Terpenic Olefins Using Co-Ag Supported on SiO2 as a Novel, Efficient, and Recyclable Catalyst
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Co-Ag supported on the SiO2 catalyst was synthesized by the sol-gel method and characterized using XRD, FT-IR, TG-DTG, BET, CV, and SEM/EDX analysis. The catalytic performance of the resulting catalyst was examined by the oxidation of mono and sesquiterpenic olefins using hydrogen peroxide and tert-butyl peroxide as oxidant agents. Various parameters such as catalyst amount, temperature, and solvents have been studied. The Co-Ag supported on the SiO2 catalyst showed a high activity, selectivity, and recyclability for the selected oxidation reaction.
- Aberkouks, Abderrazak,Mekkaoui, Ayoub Abdelkader,Ait Ali, Mustapha,El Firdoussi, Larbi,El Houssame, Soufiane
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- Phosphonate functionalized carbon spheres as Br?nsted acid catalysts for the valorization of bio-renewable a-pinene oxide totrans-carveol
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Herein, we report a simple route for the synthesis of phosphonate functionalized Br?nsted solid acid carbon spheres as heterogeneous catalyst for the valorization of bio-derived a-pinene oxide. The Br?nsted acidity was generatedviatwo steps; hydrothermal carbonization of sugar to produce carbon microspheres followed by PCl3treatment to form phosphonate functionalized carbon. The presence of phosphonate was confirmed by CP-MAS31P and13C NMR. In addition, the presence of the P-C, O-P-C and HO-P?O bonds of the phosphonate group was confirmed by FT-IR,31P NMR, and XPS. SEM-EDAX analysis revealed the presence of a phosphorus content of ~1.71 wt% on the surface of the catalyst while elemental mapping showed a uniform dispersion of phosphorus over the carbon spheres. The as-synthesized Br?nsted solid acid catalyst was used for the isomerization of a-pinene oxide which gave 100% conversion with 67%trans-carveol selectivity in highly polar basic solvent in 1 h reaction time. Also, the catalyst showed good recyclable activity even after five cycles.
- Advani, Jacky H.,Biradar, Ankush V.,Singh, Amravati S.
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supporting information
p. 7210 - 7217
(2020/06/04)
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- Engineering a Highly Defective Stable UiO-66 with Tunable Lewis-Br?nsted Acidity: The Role of the Hemilabile Linker
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The stability of metal-organic frameworks (MOFs) typically decreases with an increasing number of defects, limiting the number of defects that can be created and limiting catalytic and other applications. Herein, we use a hemilabile (Hl) linker to create up to a maximum of six defects per cluster in UiO-66. We synthesized hemilabile UiO-66 (Hl-UiO-66) using benzene dicarboxylate (BDC) as linker and 4-sulfonatobenzoate (PSBA) as the hemilabile linker. The PSBA acts not only as a modulator to create defects but also as a coligand that enhances the stability of the resulting defective framework. Furthermore, upon a postsynthetic treatment in H2SO4, the average number of defects increases to the optimum of six missing BDC linkers per cluster (three per formula unit), leaving the Zr-nodes on average sixfold coordinated. Remarkably, the thermal stability of the materials further increases upon this treatment. Periodic density functional theory calculations confirm that the hemilabile ligands strengthen this highly defective structure by several stabilizing interactions. Finally, the catalytic activity of the obtained materials is evaluated in the acid-catalyzed isomerization of α-pinene oxide. This reaction is particularly sensitive to the Br?nsted or Lewis acid sites in the catalyst. In comparison to the pristine UiO-66, which mainly possesses Br?nsted acid sites, the Hl-UiO-66 and the postsynthetically treated Hl-UiO-66 structures exhibited a higher Lewis acidity and an enhanced activity and selectivity. This is further explored by CD3CN spectroscopic sorption experiments. We have shown that by tuning the number of defects in UiO-66 using PSBA as the hemilabile linker, one can achieve highly defective and stable MOFs and easily control the Br?nsted to Lewis acid ratio in the materials and thus their catalytic activity and selectivity.
- De Geyter, Nathalie,De Vos, Dirk E.,Feng, Xiao,Hajek, Julianna,Hoffman, Alexander E. J.,Jena, Himanshu Sekhar,Leus, Karen,Leyssens, Karen,Marquez, Carlos,Meynen, Vera,Morent, Rino,Van Der Voort, Pascal,Van Speybroeck, Veronique,Veerapandian, Savita K. P.,Wang, Guangbo
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p. 3174 - 3183
(2020/03/10)
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- Limonene oxyfunctionalization over Cu-modified silicates employing hydrogen peroxide and t-Butyl hydroperoxide: Reaction pathway analysis
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Limonene oxidation over Cu-nanostructured mesoporous materials was studied. Three solids with different copper content were synthesized employing the template-ion exchange method, and physically-chemically analyzed by a multi-technical characterization. The performance of the molecular sieves as catalysts in the liquid phase oxyfunctionalization of limonene, employing hydrogen peroxide (H2O2) or t-butyl hydroperoxide (TBHP) as oxidants was evaluated. All synthesized Cu-MCM materials were active in the reaction. The obtained results showed that the used oxidant had an important influence on the products distribution under the employed conditions. With H2O2, compounds of high added value such as limonene oxide, carveol and carvone were mainly obtained. Meanwhile, with TBHP, limonene hydroperoxide turned out to be the major product. Finally, a reaction mechanism was proposed for each oxidant.
- Vaschetti, Virginia M.,Cánepa, Analía L.,Barrera, Deicy,Sapag, Karim,Eimer, Griselda A.,Casuscelli, Sandra G.
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- Heteropoly acid catalysts in upgrading of biorenewables: Synthesis of para-menthenic fragrance compounds from α-pinene oxide
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The isomerization of α-pinene oxide in the presence of Cs2.5H0.5PW12O40 (CsPW) heteropolysalt as solid acid catalyst is reported. The reactions were performed in various solvents, which allowed to obtain trans-carveol, trans-sobrerol and pinol in 60–80% yield each, which exceed the yields reported so far. The CsPW catalyst could be recovered and reused without loss of its activity and selectivity.
- Ribeiro, Cláudio J.A.,Pereira, Matheus M.,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.,Gusevskaya, Elena V.,da Silva Rocha, Kelly A.
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p. 166 - 170
(2019/01/04)
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- A Cu-Doped ZIF-8 metal organic framework as a heterogeneous solid catalyst for aerobic oxidation of benzylic hydrocarbons
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Mixed-metal metal organic frameworks have received considerable attention in recent years and it has been shown that the activity of the parent metal organic framework (MOF) is often enhanced upon doping with external metal ions within the framework. In this context, Cu2+ ions with different loadings were incorporated within the ZIF-8 framework to obtain a series of Cu-doped ZIF-8 materials and their activity was examined in the aerobic oxidation of hydrocarbons. The as-synthesized Cu-doped solids were characterized by powder X-ray diffraction (XRD), ultraviolet diffuse reflectance spectroscopy (UV-DRS), scanning electron microscopy (SEM), Fourier Transform infrared (FT-IR), electron paramagnetic resonance (EPR) and inductively coupled plasma (ICP) analysis. The experimental results revealed that the activity of Cu-doped ZIF-8 is much higher than that of the parent ZIF-8 in all the tested substrates at 120 °C. Furthermore, the activity of the Cu-doped ZIF-8 with the highest Cu loading was eight fold higher than that of the parent ZIF-8 in the aerobic oxidation of cyclooctane (1) at 120 °C with more than 80% selectivity to the corresponding cyclooctanol/cyclooctanone (ol/one) mixture. Cu-doped ZIF-8 was reused two times with no significant drop in its activity under identical conditions. Furthermore, comparison of the two times reused solid with that of the fresh solid by powder XRD and SEM analysis revealed identical structural integrity and morphology, respectively during the oxidation reactions.
- Nagarjun, Nagarathinam,Dhakshinamoorthy, Amarajothi
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p. 18702 - 18712
(2019/12/09)
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- Bimetallic Radical Redox-Relay Catalysis for the Isomerization of Epoxides to Allylic Alcohols
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Organic radicals are generally short-lived intermediates with exceptionally high reactivity. Strategically, achieving synthetically useful transformations mediated by organic radicals requires both efficient initiation and selective termination events. Here, we report a new catalytic strategy, namely, bimetallic radical redox-relay, in the regio- and stereoselective rearrangement of epoxides to allylic alcohols. This approach exploits the rich redox chemistry of Ti and Co complexes and merges reductive epoxide ring opening (initiation) with hydrogen atom transfer (termination). Critically, upon effecting key bond-forming and -breaking events, Ti and Co catalysts undergo proton transfer/electron transfer with one another to achieve turnover, thus constituting a truly synergistic dual catalytic system.
- Ye, Ke-Yin,Mccallum, Terry,Lin, Song
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supporting information
(2019/06/24)
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- Chemoselective Luche-Type Reduction of α,β-Unsaturated Ketones by Magnesium Catalysis
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The chemoselective reduction of α,β-unsaturated ketones by use of an economic and readily available Mg catalyst has been developed. Excellent yields for a wide range of ketones have been achieved under mild reaction conditions, short times, and low catalyst loadings (0.2-0.5 mol %).
- Jang, Yoon Kyung,Magre, Marc,Rueping, Magnus
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supporting information
p. 8349 - 8352
(2019/10/16)
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- Cucurbit[5]uril-mediated electrochemical hydrogenation of α,β-unsaturated ketones
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The potential of cucurbit[5]uril to be used as inverse phase transfer catalyst in electrocatalytic hydrogenation of α,β-unsaturated ketones is illustrated. The interaction behavior among isophorone and cucurbit[5]uril was also investigated using cyclic voltammetry and UV/vis absorption spectroscopy. The results concerning to both techniques revealed an enhancement in the intensity of the absorption peak and also in the current cathodic peak of isophorone in presence of cucurbit[5]uril. This achievement is related to the increase of the isophorone solubility in the medium being an indicative of a host-guest complex formation. The electrochemical hydrogenation of isophorone using cucurbit[5]uril was more efficient than others well-stablish methodologies. Regarding to (R)-(+)-pulegone and (S)-(+)-carvone, the use of cucurbit[5]uril leads to an increase of 17% and 9%, on average, respectively, in the yields when compared to the control reaction. The efficiency of selective C=O bond hydrogenation of 1-acetyl-1-cyclohexene was evaluated. The presence of cucurbit[5]uril increased by 12% the hydrogenations yields of 1-acetyl-1-cyclohexene when compared to the control reaction. In this sense, these results open up an opportunity to carry out electrocatalytic reactions within the cucurbit[5]uril environment.
- Sales, Ayrlane,de Oliveira e Castro, Isabela Andrade,de Menezes, Frederico Duarte,Selva, Thiago Matheus Guimar?es,Vilar, Márcio
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p. 295 - 305
(2019/09/03)
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- Exploring the substrate specificity of Cytochrome P450cin
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Cytochromes P450 are enzymes that catalyse the oxidation of a wide variety of compounds that range from small volatile compounds, such as monoterpenes to larger compounds like steroids. These enzymes can be modified to selectively oxidise substrates of interest, thereby making them attractive for applications in the biotechnology industry. In this study, we screened a small library of terpenes and terpenoid compounds against P450cin and two P450cin mutants, N242A and N242T, that have previously been shown to affect selectivity. Initial screening indicated that P450cin could catalyse the oxidation of most of the monoterpenes tested; however, sesquiterpenes were not substrates for this enzyme or the N242A mutant. Additionally, both P450cin mutants were found to be able to oxidise other bicyclic monoterpenes. For example, the oxidation of (R)- and (S)-camphor by N242T favoured the production of 5-endo-hydroxycamphor (65–77% of the total products, dependent on the enantiomer), which was similar to that previously observed for (R)-camphor with N242A (73%). Selectivity was also observed for both (R)- and (S)-limonene where N242A predominantly produced the cis-limonene 1,2-epoxide (80% of the products following (R)-limonene oxidation) as compared to P450cin (23% of the total products with (R)-limonene). Of the three enzymes screened, only P450cin was observed to catalyse the oxidation of the aromatic terpene p-cymene. All six possible hydroxylation products were generated from an in vivo expression system catalysing the oxidation of p-cymene and were assigned based on 1H NMR and GC-MS fragmentation patterns. Overall, these results have provided the foundation for pursuing new P450cin mutants that can selectively oxidise various monoterpenes for biocatalytic applications.
- Stok, Jeanette E.,Giang, Peter D.,Wong, Siew Hoon,De Voss, James J.
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- Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
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In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
- Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
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supporting information
p. 80 - 84
(2019/01/04)
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- Stereodivergent Synthesis of Carveol and Dihydrocarveol through Ketoreductases/Ene-Reductases Catalyzed Asymmetric Reduction
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Chiral carveol and dihydrocarveol are important additives in the flavor industry and building blocks in the synthesis of natural products. Despite the remarkable progress in asymmetric catalysis, convenient access to all possible stereoisomers of carveol and dihydrocarveol remains a challenge. Here, we present the stereodivergent synthesis of carveol and dihydrocarveol through ketoreductases/ene-reductases catalyzed asymmetric reduction. By directly asymmetric reduction of (R)- and (S)-carvone using ketoreductases, which have Prelog or anti-Prelog stereopreference, all four possible stereoisomers of carveol with medium to high diastereomeric excesses (up to >99 %) were first observed. Then four stereoisomers of dihydrocarvone were prepared through ene-reductases catalyzed diastereoselective synthesis. Asymmetric reduction of obtained dihydrocarvone isomers by ketoreductases further provide access to all eight stereoisomeric dihydrocarveol with up to 95 % de values. In addition, the absolute configurations of dihydrocarveol stereoisomers were determined by using modified Mosher's method.
- Guo, Jiyang,Zhang, Rui,Ouyang, Jingping,Zhang, Feiting,Qin, Fengyu,Liu, Guigao,Zhang, Wenhe,Li, Hengyu,Ji, Xiaohong,Jia, Xian,Qin, Bin,You, Song
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p. 5496 - 5504
(2018/11/30)
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- Selective Base-free Transfer Hydrogenation of α,β-Unsaturated Carbonyl Compounds using iPrOH or EtOH as Hydrogen Source
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Commercially available Ru-MACHOTM-BH is an active catalyst for the hydrogenation of several functional groups and for the dehydrogenation of alcohols. Herein, we report on the new application of this catalyst to the base-free transfer hydrogenation of carbonyl compounds. Ru-MACHOTM-BH proved to be highly active and selective in this transformation, even with α,β-unsaturated carbonyl compounds as substrates. The corresponding aliphatic, aromatic and allylic alcohols were obtained in excellent yields with catalyst loadings as low as 0.1–0.5 mol % at mild temperatures after very short reaction times. This protocol tolerates iPrOH and EtOH as hydrogen sources. Additionally, scale up to multi-gram amounts was performed without any loss of activity or selectivity. An outer-sphere mechanism has been proposed and the computed kinetics and thermodynamics of crotonaldehyde and 1-phenyl-but-2-en-one are in perfect agreement with the experiment.
- Farrar-Tobar, Ronald A.,Wei, Zhihong,Jiao, Haijun,Hinze, Sandra,de Vries, Johannes G.
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supporting information
p. 2725 - 2734
(2018/02/28)
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- Creating Hierarchical Pores by Controlled Linker Thermolysis in Multivariate Metal-Organic Frameworks
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Sufficient pore size, appropriate stability, and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization, and catalysis involving large molecules. Herein, we report a powerful and general strategy, linker thermolysis, to construct ultrastable hierarchically porous metal-organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxylation process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultrasmall metal oxide nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid-catalyzed reactions. Most importantly, this work provides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on probing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.
- Feng, Liang,Yuan, Shuai,Zhang, Liang-Liang,Tan, Kui,Li, Jia-Luo,Kirchon, Angelo,Liu, Ling-Mei,Zhang, Peng,Han, Yu,Chabal, Yves J.,Zhou, Hong-Cai
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supporting information
p. 2363 - 2372
(2018/02/19)
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- Pt/Ferric Hydroxyphosphate: An Effective Catalyst for the Selective Hydrogenation of Α,Β-Unsaturated Aldehydes (Ketones) into Α,Β-Unsaturated Alcohols
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Abstract: Four micro (nano)-sized mesoporous ferric hydroxyphosphates (FHP) are synthesized by a reverse microemulsion-solvothermal method, and then are used as supports to prepare supported Pt catalysts. The mean particle diameter of Pt nanoparticles (NPs) was 4.5–4.6?nm. When the four different Pt/FHP catalysts were used into the hydrogenation of α,β-unsaturated aldehydes (ketones) to their corresponding unsaturated alcohols, Pt/FHP (c) catalyst showed better catalytic performance than the other three partners. Under the optimal experimental conditions, several tested α,β-unsaturated aldehydes could be effectively transformed into corresponding unsaturated alcohols over Pt/FHP (c) catalyst. The catalyst could be recycled and reused several times without activity loss. We propose the stronger interaction between the Pt NPs and ferric ions of the FHP (c) are responsible for its good catalytic performance, and this stronger interaction should be rooted in its enhanced Lewis acid strength.
- Liu, Cheng,Luo, Wei,Liu, Junhua,Sun, Lei,Yang, Yue,Liu, Gui,Wang, Fang,Zhong, Wei,Guild, Curtis,Suib, Steven L.
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p. 555 - 563
(2018/01/11)
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- OXIDATION OF LIMONENE
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The invention discloses a process for the oxidation of limonene, comprising the reaction of limonene with hydrogen peroxide in the presence of a catalyst containing atoms and/or ions of at least one metal, selected from the group consisting of molybdenum, tungsten, scandium, vanadium, titanium, lanthanum, zirconium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, erbium or ytterbium, characterised in that the molecular weight of the catalyst is less than 2,000 g/mol and that the reaction is performed at a pH value of more than 7.5.
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Paragraph 0043; 0045; 0046
(2018/06/15)
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- Synthesis of Fencholenic Aldehyde from α-pinene Epoxide on Modified Clays
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The conditions for isomerization of α-pinene epoxide (2,3-epoxypinane) on modified clays that gave comparatively high contents (33.0%) of fencholenic (iso-campholenic) aldehyde in the product mixture were determined. An effective method for isolating it w
- Sidorenko, A. Yu.,Ignatovich, Zh. V.,Ermolinskaya,Kravtsova,Baranovskii,Koroleva,Agabekov
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p. 893 - 897
(2018/09/27)
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- Method of alcoholization of D-carvone and separation of enantiomer
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The invention discloses a method of reduction alcoholization of D-carvone and resolution of an enantiomer by biocatalysis. The D-carvone is taken as a raw material and subjected to reduction with sodium borohydride to obtain a compound II, the compound II is subjected to enzymatic kinetic resolution reaction to obtain a compound III and a compound IV, or the compound II is subjected to dynamic kinetic resolution to obtain the compound III of which the yield is higher than 90%, and a compound V can be obtained by hydrolyzing the compound III. The method further changes a prochiral ketone group in the D-carvone into a chiral hydroxyl center and carries out further resolution; and the method has the characteristics of simplicity of operation, high yield of product, good optical purity and the like.
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- Photoinduced Carboborative Ring Contraction Enables Regio- and Stereoselective Synthesis of Multiply Substituted Five-Membered Carbocycles and Heterocycles
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We report herein a photoinduced carboborative ring contraction of monounsaturated six-membered carbocycles and heterocycles. The reaction produces substituted five-membered ring systems stereoselectively and on preparative scales. The products feature multiple stereocenters, including contiguous quaternary carbons. We show that the reaction can serve as a synthetic platform for ring system alteration of natural products. The reaction can also be used in natural product synthesis. A concise total synthesis of artalbic acid has been enabled by a sequence of photoinduced carboborative ring contraction, Rauhut-Currier reaction, and nitrilase-catalyzed hydrolysis. The synthetic utility of the reaction has been further demonstrated by converting the intermediate organoboranes to alcohols, amines, and alkenes.
- Jin, Shengfei,Nguyen, Vu T.,Dang, Hang T.,Nguyen, Dat P.,Arman, Hadi D.,Larionov, Oleg V.
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supporting information
p. 11365 - 11368
(2017/08/30)
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- Hydrogenation of Carbonyl Derivatives with a Well-Defined Rhenium Precatalyst
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The first efficient and general rhenium-catalyzed hydrogenation of carbonyl derivatives was developed. The key to the success of the reaction was the use of a well-defined rhenium complex bearing a tridentate diphosphinoamino ligand as the catalyst (0.5 mol %) at 70 °C in the presence of H2 (30 bar). The mechanism of the reaction was investigated by DFT(PBE0-D3) calculations.
- Wei, Duo,Roisnel, Thierry,Darcel, Christophe,Clot, Eric,Sortais, Jean-Baptiste
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-
- Selective Hydrogenation of α,β-Unsaturated Aldehydes and Ketones by Air-Stable Ruthenium NNS Complexes
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The selective hydrogenation of the carbonyl functionality of α,β-unsaturated aldehydes and ketones is catalysed by ruthenium dichloride complexes bearing a tridentate NNS ligand as well as triphenylphosphine. The tridentate ligand backbone is flexible, as evidenced by the equilibrium observed in solution between the cis- and trans-isomers of the dichloride precatalysts, as well as crystal structures of several of these complexes. The complexes are activated by base in the presence of hydrogen and readily hydrogenate carbonyl functionalities under mild conditions. Despite the activation by base, side reactions are negligible, even for aldehyde substrates, because of the low amount of base. Thus, the corresponding allylic alcohols can be isolated in very good yields on a 10–25 mmol scale. Turnover numbers up to 200 000 were achieved.
- Puylaert, Pim,van Heck, Richard,Fan, Yuting,Spannenberg, Anke,Baumann, Wolfgang,Beller, Matthias,Medlock, Jonathan,Bonrath, Werner,Lefort, Laurent,Hinze, Sandra,de Vries, Johannes G.
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p. 8473 - 8481
(2017/06/28)
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- Zeolite Y encaged Ru(III) and Fe(III) complexes for oxidation of styrene, cyclohexene, limonene, and α-pinene: An eye-catching impact of H2SO4 on product selectivity
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A novel Ru(III) and Fe(III) complexes of ligands 1 and/or 2 {where 1 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene))diphenol and 2 = 2,2'-((1E,1'E)-((azanediylbis(ethane-2,1-diyl))bis(azanylylidene))bis(methanylylidene)) bis(4-nitrophenol)} have been synthesized as ‘neat’ and zeolite Y encapsulated complexes. These catalysts are characterized by various analytical tools such as FTIR, UV–vis, elemental analysis, ICP-AES, molar conductivity, 1H- and 13C NMR, TGA, SEM, AAS, BET, magnetic susceptibility and powder XRD to endorse the complex formation, absence of peripheral redundant ligands and complexes, conservation of zeolite Y morphology and crystallinity, and the encapsulation of complexes without devastation in the zeolite Y framework. Out of these synthesized catalysts, 5Y is found to be a potent candidate for styrene (Conv. 76.1%, TOF: 2130 h?1), cyclohexene (Conv. 84.4%, TOF: 2351 h?1), limonene (Conv. 81.6%, TOF: 2273 h?1), and α-pinene (Conv. 72.6%, TOF: 2023 h?1) oxidation with high selectivity of respective allylic products excluding the styrene oxidation, which undergoes epoxidation only. The addition of H2SO4 in an identical reaction catalyzed by 5Y not only surge the conversion up to 100% in a short time span with high TOF but also increase the selectivity of respective epoxidation products. This switchover in the selectivities could be credited to the presence of H2SO4 that facilitates the heterolytic [sbnd]O[sbnd]O[sbnd] bond cleavage of metal hydroperoxide and stimulates the epoxidation over allylic oxidation. Furthermore, the results establish that the heterogeneous systems are effortlessly recovered and reused without ample drop in the activity and selectivity.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
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p. 223 - 237
(2016/12/09)
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- Preparation method of carvone
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The invention relates to a preparation method of carvone. The carvone is prepared by using easily-obtained alpha-pinene as a raw material and performing three-step reaction of epoxidation- isomerism-oxidization. The epoxidation- isomerism reaction can be carried out continuously; after finishing the epoxidation reaction, ligand, free radical initiator and transition metal additive are added to perform isomerism reaction and generate carvone; furthermore, the carvone is prepared through oxidization reaction. The method is simple in process, easy to obtain pinene raw material; the method avoids the shortcomings of low yield, poor selectivity, difficult separation, and massive hardly-disposed waste water of a traditional process, and is applicable to the industrial production.
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-
Paragraph 0025; 0060; 0061; 0065; 0068; 0071; 0074; 0077
(2017/08/31)
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- Synthesis, characterization and catalytic application of a new organometallic oligomer based on polyhedral oligomeric silsesquioxane
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Although homogeneous catalysts provide high performance and selectivity, the difficulty of separation and recycling of these catalysts has bothered the scientific community worldwide. Therefore, the demand for heterogeneous catalysts that possess the advantages of homogeneous ones, with ease of separation and recyclability remains a topic of major impact. The oligomeric catalyst synthesized in this work was characterized using elemental analysis, Fourier transform infrared, 13C NMR, 29Si NMR and energy-dispersive X-ray spectroscopies, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and Brunauer–Emmett–Teller analysis and compared to its homogeneous counterpart [W(CO)3Br2(ATC)] in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene. The results showed that the percentage conversion for the homogeneous species [W(CO)3Br2(ATC)] was slightly higher than for the oligomeric catalyst (POSS-ATC-[W(CO)3Br2]). Furthermore, the selectivity for epoxide of the oligomeric catalyst was greater than that of the homogeneous catalyst by about 25% when (S)-limonene was used. Great conversions (yields) of products were obtained with a wide range of substrates and the catalyst was recycled many times without any substantial loss of its catalytic activity.
- Vieira, Eduardo Guimar?es,Silva, Rafael Oliveira,Junior, Enes Furlani,Dias Filho, Newton Luiz
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- Synthesis and properties of novel chiral imidazolium-based ionic liquids derived from carvone
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A large series of novel chiral imidazolium ionic liquids were synthesized using the terpenoid carvone as the chiral substrate. Their specific rotations were characterized and their potential use in chiral recognition was demonstrated by studying interactions with racemic Mosher's acid salt.
- Santamarta, Francisco,Vilas, Miguel,Tojo, Emilia,Fall, Yagamare
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p. 31177 - 31180
(2016/04/08)
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- A General CuCl2-Promoted Alkene Aminochlorination Reaction
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A CuCl2-promoted alkene aminochlorination reaction has been developed. A variety of anilides that contain a mono-, di-, or trisubstituted alkenyl moiety readily participated in this reaction to afford structurally diverse vicinal chloroamines. Studies suggest that the process proceeds by a radical-type mechanism and that CuCl2serves as both the oxidant to generate the amidyl radical as well as the chloride source.
- Li, Shu-Qi,Xiong, Peng,Zhu, Lin,Qian, Xiang-Yang,Xu, Hai-Chao
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supporting information
p. 3449 - 3455
(2016/07/23)
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- The studies on the limonene oxidation over the microporous TS-1 catalyst
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The studies on the oxidation of limonene with 60 wt% hydrogen peroxide over the titanium silicalite TS-1 catalyst were carried out. The influence of the following parameters was examined: the temperature 0-120 °C, the molar ratio of limonene/H2O2 = 1:2-5:1, methanol concentration 60-95 wt%, TS-1 content 0.25-8 wt% and the reaction time 15 min to 11 days. The studies showed that the most beneficial conditions for the obtaining of high selectivity of 1,2-epoxylimonene, at simultaneously high values of the conversion of reactants and the efficiency of hydrogen peroxide, are as follows: the temperature 80 °C, the molar ratio of limonene/H2O2 = 1:1, the methanol concentration 80 wt%, the TS-1 content 3 wt% and the reaction time 10 days. Moreover, the research showed that the process of limonene oxidation is very complicated, because during this process also other very useful oxygenated derivatives of limonene can be obtained, for example: perillyl alcohol, carveol, carvone and 1,2-epoxylimonene diol. The studies on the reuse of the TS-1 catalyst showed that it is very stable catalyst at the studied conditions and it can be recycled to the oxidation process at least three times.
- Wróblewska, Agnieszka,Makuch, Edyta,Miadlicki, Piotr
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p. 121 - 129
(2016/04/26)
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- Chemoselective reduction of α,β-unsaturated carbonyl compounds with UiO-66 materials
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Allylic alcohols, important intermediates in fine chemical industry, are typically obtained through chemoselective hydrogenation of α,β-unsaturated aldehydes. Here we show that UiO-66, a zirconium-based metal-organic framework can be used in the chemoselective hydrogenation of cinnamaldehyde, both under high hydrogen pressure as silver nanoparticle support, and as transfer hydrogenation catalyst in the Meerwein-Ponndorf-Verley (MPV) reduction. A recyclable 10 wt% Ag/UiO-66 catalyst reached complete conversion after 6 h and 50 bar of H2 with 66% selectivity for cinnamyl alcohol in the inert solvent N,N-dimethylacetamide (DMA). Pure UiO-66 as MPV catalyst with isopropanol reached complete conversion with >90% selectivity after 24 h at 120 °C. The substrate scope was extended to citral and carvone, two α,β-unsaturated carbonyl compounds that are harder to reduce selectively. Introduction of a NO2-functional group into the UiO-66 linker to increase the Lewis acidity was clearly beneficial for the conversion of carvone.
- Plessers, Eva,De Vos, Dirk E.,Roeffaers, Maarten B.J.
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p. 136 - 143
(2016/07/06)
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- Zeolite-Y immobilized Metallo-ligand complexes: A novel heterogenous catalysts for selective oxidation
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Transition metal [M?=?Co(II), Cu(II)] complexes of H2L1 and H2L2 ligands have been prepared as neat and nanohybrid zeolite-Y immobilized complexes. The various analytical tools such as FTIR, ICP-AES, elemental analysis, UV–vis, Brunauer, Emmett and Teller (BET) surface area analysis, Thermal analysis, scanning electron micrographs, Powder XRD, conductivity, magnetic moment, and AAS were employed for the characterization of the prepared catalysts. Among all catalysts, the [Cu(L1)]-Y (heterogeneous) and [Cu(L1)] (homogeneous) have offered high activity and selectivity over oxidation of cyclohexene. Moreover, the [Cu(L1)] and [Cu(L1)]-Y were employed as catalyst over various organic substrates at identical reaction condition. The immobilized catalyst [Cu(L1)]-Y is found to be moderate active over oxidation of cyclohexane (75.2%,), benzene (8.21%), phenol (14.5%), styrene (87.5), benzyl alcohol (21.5%), limonene (11.2%), α-pinene (9.15%), and cyclooctane (76.8%) with high TON values (21942-2054). The mechanistic study using UV–vis and FTIR suggests the participation of active metalperoxo species, which is reinforced by its high catalytic activity over limonene (16.3%) in the absence oxidant.
- Godhani, Dinesh R.,Nakum, Haresh D.,Parmar, Digvijaysinh K.,Mehta, Jignasu P.,Desai, Nisheeth C.
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p. 105 - 116
(2016/09/07)
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- Photoredox Activation of SF6for Fluorination
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We report the first practical use of SF6as a fluorinating reagent in organic synthesis. Photoredox catalysis enables the in situ conversion of SF6, an inert gas, into an active fluorinating species by using visible light. Under these conditions, deoxyfluorination of allylic alcohols is effected with high chemoselectivity and is tolerant of a wide range of functional groups. Application of the methodology in a continuous-flow setup achieves comparable yields to those obtained with a batch setup, while providing drastically increased material throughput of valuable allylic fluoride products.
- McTeague, T. Andrew,Jamison, Timothy F.
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supporting information
p. 15072 - 15075
(2016/11/25)
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- Fe/EuroPh catalysts for limonene oxidation to 1,2-epoxylimonene, its diol, carveol, carvone and perillyl alcohol
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The catalysts in the form of an activated carbon EuroPh supported Fe were prepared and characterized structurally and chemically by XRD, nitrogen sorption, FESEM, EDX, and ICP-AES methods. The active phase was magnetite Fe3O4. The concentration of Fe in the catalysts was equal to 0.68, 1.32, 2.64 wt%. The catalytic activity of the obtained catalysts was examined in limonene oxidation with hydrogen peroxide and tert-butyl hydroperoxide as oxidants. The studies were carried out in a batch reactor. The catalytic activity of the recovered catalysts was also tested. The research showed that all from the studied catalysts were active in the limonene oxidation. As a result of limonene oxidation the following products were mainly obtained: 1,2-epoxylimonene diol, carveol, carvone and perillyl alcohol - products with a great importance. The reused catalysts were characterized by considerably lover activity in the limonene oxidation than in the first run, especially when the oxidation was performed with t-butyl hydroperoxide.
- Mlodzik, Jacek,Wrblewska, Agnieszka,Makuch, Edyta,Wrbel, Rafal J.,Michalkiewicz, Beata
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p. 111 - 120
(2016/04/26)
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- Metal oxide-triazole hybrids as heterogeneous or reaction-induced self-separating catalysts
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The hybrid metal oxide-triazole materials [MoO3(trz)0.5] (1) and [W2O6(trz)] (2) (trz?=?1,2,4-triazole) have been hydrothermally synthesized and characterized by different techniques (TGA, SEM, 1H and 13C MAS NMR, FT-IR spectroscopy, and structure determination by Rietveld analysis of high resolution synchrotron powder XRD data). Materials 1 and 2 display distinct behaviors when applied as catalysts for oxidation reactions with alcohol, aldehyde, olefin and sulfide substrates, and are more effective with hydrogen peroxide as the oxidant than with tert-butylhydroperoxide. The MoVI hybrid 1 transforms into soluble active species during cis-cyclooctene epoxidation with H2O2. When consumption of H2O2 reaches completion, spontaneous reassembly of the 2-dimensional molybdenum oxide network of 1 takes place and the hybrid precipitates as a microcrystalline solid that can be easily separated and recycled. Reaction-induced self-separation behavior occurs with 1, H2O2 and other substrates such as methyl oleate and methylphenylsulfide. The WVI hybrid 2 behaves differently, preserving its structural features throughout the heterogeneous catalytic process.
- Amarante, Tatiana R.,Neves, Patrícia,Valente, Anabela A.,Paz, Filipe A. Almeida,Pillinger, Martyn,Gon?alves, Isabel S.
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p. 354 - 367
(2016/07/06)
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- Biologically Inspired and Magnetically Recoverable Copper Porphyrinic Catalysts: A Greener Approach for Oxidation of Hydrocarbons with Molecular Oxygen
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An efficient synthetic method for magnetically recoverable hybrid copper porphyrinic nanomaterials is reported. These functionalized magnetic materials prove to be efficient bioinspired oxidation catalysts of olefins and thiols, using molecular oxygen as oxidant, in total absence of reductants and solvents, with the highest TON (turnover number) yet achieved for this reaction (≈200 000). A comparative study between homogeneous and heterogeneous oxidation of cyclohexene is discussed, revealing the heterogeneous system to be the most promising concerning stability and reusability of the catalysts. The full characterization of the magnetic hybrid porphyrinic nanomaterials, by transmission electron microscopy, flame atomic absorption spectrometry, thermogravimetry, N2 sorption, and infrared spectroscopy, is also described.
- Henriques, César A.,Fernandes, Auguste,Rossi, Liane M.,Ribeiro, M. Filipa,Calvete, Mário J. F.,Pereira, Mariette M.
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p. 3359 - 3368
(2016/06/06)
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- TERPENE AND TERPENOID DERIVATIVES CONTAINING VINYL GROUPS FOR THE PREPARATION OF POLYMERS
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The invention relates to a method for producing functionalised monomers, the method comprising: a) providing a starting material selected from terpenes and terpenoids; b) forming a derivative of the starting material by incorporation of a hydroxyl group; c) esterifying the hydroxyl group of the derivative to introduce a moiety containing a vinyl group, so as to produce a functionalised monomer. The functionalised monomer can be polymerised to obtain a bio-derived polymer.
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Page/Page column 57; 58
(2015/11/10)
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- Comparative anticonvulsant study of epoxycarvone stereoisomers
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Stereoisomers of the monoterpene epoxycarvone (EC), namely (+)-cis-EC, (-)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC, were comparatively evaluated for anticonvulsant activity in specific methodologies. In the pentylenetetrazole (PTZ)-induced anticonvulsant test, all of the stereoisomers (at 300 mg/kg) increased the latency to seizure onset, and afforded 100% protection against the death of the animals. In the maximal electroshock-induced seizures (MES) test, prevention of tonic seizures was also verified for all of the isomers tested. However, the isomeric forms (+) and (-)-Trans-EC showed 25% and 12.5% inhibition of convulsions, respectively. In the pilocarpine-induced seizures test, all stereoisomers demonstrated an anticonvulsant profile, yet the stereoisomers (+) and (-)-Trans-EC (at 300 mg/kg) showed a more pronounced effect. A strychnine-induced anticonvulsant test was performed, and none of the stereoisomers significantly increased the latency to onset of convulsions; the stereoisomers probably do not act in this pathway. However, the stereoisomers (+)-cis-EC and (+)-Trans-EC greatly increased the latency to death of the animals, thus presenting some protection. The four EC stereoisomers show promise for anticonvulsant activity, an effect emphasized in the isomers (+)-cis-EC, (+)-Trans-EC, and (-)-Trans-EC for certain parameters of the tested methodologies. These results serve as support for further research and development of antiepileptic drugs from monoterpenes.
- Salgado, Paula Regina Rodrigues,Da Fonsêca, Diogo Vilar,Braga, Renan Marinho,De Melo, Cynthia Germoglio Farias,Andrade, Luciana Nalone,De Almeida, Reinaldo Nóbrega,De Sousa, Dami?o Pergentino
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p. 19660 - 19673
(2015/12/23)
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- Engineering Rieske Non-Heme Iron Oxygenases for the Asymmetric Dihydroxylation of Alkenes
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The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non-heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono- and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio- and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild-type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins. Modulation by mutation: Rieske non-heme iron oxygenases can be used as efficient biocatalysts for the selective oxyfunctionalization of various olefins yielding vicinal cis-diols and allylic alcohols. Introduction of a single amino acid substitution in the active sites of two selected oxygenases resulted in variants with improved stereoselectivities and product formations.
- Gally, Christine,Nestl, Bettina M.,Hauer, Bernhard
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supporting information
p. 12952 - 12956
(2015/11/02)
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- Eco-friendly stereoselective reduction of α,β-unsaturated carbonyl compounds by Er(OTf)3/NaBH4 in 2-MeTHF
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An operationally simple and environmentally benign catalytic procedure has been developed to selectively reduce different α,β-unsaturated ketones. The corresponding allylic alcohols are obtained with high chemo- and diastereoselectivity using Er(OTf)3 and NaBH4 in 2-MeTHF. This protocol reduces the amount of catalyst and NaBH4 needed, compared to classical procedures and the stages of extraction/purification are carried out in aqueous solutions avoiding the use of toxic solvents. Taking into account that Er(OTf)3 can be considered even less toxic than table salt and the 'greenness' of 2-MeTHF as a solvent, the system Er(OTf)3/2-MeTHF can be proposed as a cheap, efficient, and environmentally sustainable reduction system for the synthesis of allylic alcohols.
- Nardi, Monica,Sindona, Giovanni,Costanzo, Paola,Oliverio, Manuela,Procopio, Antonio
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p. 1132 - 1135
(2015/02/19)
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- Borinic Acid Catalyzed, Regioselective Chloroacylations and Chlorosulfonylations of 2,3-Epoxy Alcohols
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In the presence of a borinic acid derived catalyst, 2,3-epoxy alcohols undergo couplings with acyl and sulfonyl chlorides. This transformation directly generates O-acylated or O-sulfonylated chlorohydrin diols, with significant levels of regioselectivity for both the ring-opening and O-functionalization steps.
- Tanveer, Kashif,Jarrah, Kareem,Taylor, Mark S.
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supporting information
p. 3482 - 3485
(2015/07/28)
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- Continuous flow photooxygenation of monoterpenes
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Photooxygenation of monoterpenes was conducted in two continuous flow reactors. The first, suitable for lab-scale research, had a maximum yield of 99.9%, and the second, focused on industrial applications, showed a daily output that was 270.0-fold higher than that in batch systems. The use of sunlight instead of an LED lamp gave 68.28% conversion.
- Park, Chan Yi,Kim, Young Joon,Lim, Hyo Jin,Park, Jeong Hyeon,Kim, Mi Jin,Seo, Seung Woo,Park, Chan Pil
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p. 4233 - 4237
(2015/02/19)
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