- Independent generation of triplet 1,4-biradical intermediates implicated in the photochemical cycloaddition reaction between 2-cyclopentenone and acrylonitrile
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Norrish Type 1 photochemistry of 3-cyanobicyclo[3.3.0]octane-2,6-dione and 3-cyanobicyclo[3.3.0]octane-2,8-dione is used to generate triplet 1,4-biradicals implicated in the photochemical cycloaddition reaction of 2-cyclopentenone with acrylonitrile. The fates of these biradicals have been determined and they suggest that the photocycloaddition reaction regiochemistry is governed by competition between closure of the biradicals to product and their reversion to ground state starting materials. This provides further evidence against the long-held view that the relative rates of formation of the biradicals mediated by an oriented triplet exciplex governs the reaction regiochemistry. It is also found that the regiochemistry of the photochemical cycloaddition reaction between cyclopentenone and acrylonitrile is reversed from that obtained in the addition of acrylonitrile to 2-cyclohexenone.
- Krug,Rudolph,Weedon
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Read Online
- Electrochemically driven desaturation of carbonyl compounds
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Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
- Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
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p. 367 - 372
(2021/03/31)
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- g-C3N4/metal halide perovskite composites as photocatalysts for singlet oxygen generation processes for the preparation of various oxidized synthons
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g-C3N4/metal halide perovskite composites were prepared and used for the first time as photocatalysts forin situ1O2generation to perform hetero Diels-Alder, ene and oxidation reactions with suitable dienes and alkenes. The standardized methodology was made applicable to a variety of olefinic substrates. The scope of the method is finely illustrated and the reactions afforded desymmetrized hydroxy-ketone derivatives, unsaturated ketones and epoxides. Some limitations were also observed, especially in the case of the alkene oxidations, and poor chemoselectivity was somewhere observed in this work which is the first application of MHP-based composites forin situ1O2generation. The experimental protocol can be used as a platform to further expand the knowledge and applicability of MHPs to organic reactions, since perovskites offer a rich variety of tuning strategies which may be explored to improve reaction yields and selectivities.
- Corti, Marco,Chiara, Rossella,Romani, Lidia,Mannucci, Barbara,Malavasi, Lorenzo,Quadrelli, Paolo
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p. 2292 - 2298
(2021/04/12)
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- Reductive Electrochemical Activation of Molecular Oxygen Catalyzed by an Iron-Tungstate Oxide Capsule: Reactivity Studies Consistent with Compound i Type Oxidants
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The reductive activation of molecular oxygen catalyzed by iron-based enzymes toward its use as an oxygen donor is paradigmatic for oxygen transfer reactions in nature. Mechanistic studies on these enzymes and related biomimetic coordination compounds designed to form reactive intermediates, almost invariably using various "shunt" pathways, have shown that high-valent Fe(V)=O and the formally isoelectronic Fe(IV) =O porphyrin cation radical intermediates are often thought to be the active species in alkane and arene hydroxylation and alkene epoxidation reactions. Although this four decade long research effort has yielded a massive amount of spectroscopic data, reactivity studies, and a detailed, but still incomplete, mechanistic understanding, the actual reductive activation of molecular oxygen coupled with efficient catalytic transformations has rarely been experimentally studied. Recently, we found that a completely inorganic iron-tungsten oxide capsule with a keplerate structure, noted as {Fe30W72}, is an effective electrocatalyst for the cathodic activation of molecular oxygen in water leading to the oxidation of light alkanes and alkenes. The present report deals with extensive reactivity studies of these {Fe30W72} electrocatalytic reactions showing (1) arene hydroxylation including kinetic isotope effects and migration of the ipso substituent to the adjacent carbon atom ("NIH shift"); (2) a high kinetic isotope effect for alkyl C - H bond activation; (3) dealkylation of alkylamines and alkylsulfides; (4) desaturation reactions; (5) retention of stereochemistry in cis-alkene epoxidation; and (6) unusual regioselectivity in the oxidation of cyclic and acyclic ketones, alcohols, and carboxylic acids where reactivity is not correlated to the bond disassociation energy; the regioselectivity obtained is attributable to polar effects and/or entropic contributions. Collectively these results also support the conclusion that the active intermediate species formed in the catalytic cycle is consistent with a compound I type oxidant. The activity of {Fe30W72} in cathodic aerobic oxidation reactions shows it to be an inorganic functional analogue of iron-based monooxygenases.
- Bugnola, Marco,Shen, Kaiji,Haviv, Eynat,Neumann, Ronny
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p. 4227 - 4237
(2020/05/05)
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- K2S2O8-promoted C-Se bond formation to construct α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds
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A novel K2S2O8-promoted C-Se bond formation from cross-coupling under neutral conditions has been developed. A variety of aldehydes and ketones react well using K2S2O8 as the oxidant in the absence of catalyst and afford desired products in moderate to excellent yields. This protocol provides a very simple route for the synthesis of α-phenylseleno carbonyl compounds and α,β-unsaturated carbonyl compounds.
- Yang, Xue-Yan,Wang, Ruizhe,Wang, Lu,Li, Jianjun,Mao, Shuai,Zhang, San-Qi,Chen, Nanzheng
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p. 28902 - 28905
(2020/08/25)
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- A gradient reduction strategy to produce defects-rich nano-twin Cu particles for targeting activation of carbon-carbon or carbon-oxygen in furfural conversion
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Complexity of chemical linkages (C-C/C-H/C-O, C=C/C=O, or C-O-H/C-O-C) in biomass-derived molecules makes the selective activation of targeted bonds much more challenging, expecting well-defined catalysts and definite catalytically-active sites. This work demonstrates an effective gradient reduction strategy to control the definite structure of catalytically-active sites, affording defects-rich nano-twin Cu particles. This strategy just involves the reduction (calcination under H2) of CuII-containing layered double hydroxides (LDHs) simply with controlling the reduction gradient (interval time) of CuII species in two chemical micro-environments (CuII-O-CuII and CuII-O-MII/III/IV (M ≠ Cu)) in the brucite-like layer of LDHs. The nano-twin Cu particles efficiently promote the target activation of C-O and C=C in the conversion of furfural to cyclopentanone (CPO). With ~100% furfural conversion, the defects-rich nano-twin Cu particles afford a CPO selectivity of 92%, 50% higher than regular spherical Cu particles. The multi-stepped defect sites, originating from the planar defects, play a decisive role in promoting the CPO selectivity by facilitating the hydro-deoxygenation to C-O of 4-hydroxycyclopentenone (HCP) and hydrogenation to C=C of HCP or cyclopentenone.
- An, Zhe,Guo, Shaowei,He, Jing,Ma, Xiaodan,Shu, Xin,Song, Hongyan,Xiang, Xu,Zhang, Jian,Zhu, Yanru
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- Quantitative production of butenes from biomass-derived γ-valerolactone catalysed by hetero-atomic MFI zeolite
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The efficient production of light olefins from renewable biomass is a vital and challenging target to achieve future sustainable chemical processes. Here we report a hetero-atomic MFI-type zeolite (NbAlS-1), over which aqueous solutions of γ-valerolactone (GVL), obtained from biomass-derived carbohydrates, can be quantitatively converted into butenes with a yield of >99% at ambient pressure under continuous flow conditions. NbAlS-1 incorporates simultaneously niobium(v) and aluminium(iii) centres into the framework and thus has a desirable distribution of Lewis and Br?nsted acid sites with optimal strength. Synchrotron X-ray diffraction and absorption spectroscopy show that there is cooperativity between Nb(v) and the Br?nsted acid sites on the confined adsorption of GVL, whereas the catalytic mechanism for the conversion of the confined GVL into butenes is revealed by in situ inelastic neutron scattering, coupled with modelling. This study offers a prospect for the sustainable production of butene as a platform chemical for the manufacture of renewable materials.
- Lin, Longfei,Sheveleva, Alena M.,da Silva, Ivan,Parlett, Christopher M. A.,Tang, Zhimou,Liu, Yueming,Fan, Mengtian,Han, Xue,Carter, Joseph H.,Tuna, Floriana,McInnes, Eric J. L.,Cheng, Yongqiang,Daemen, Luke L.,Rudi?, Svemir,Ramirez-Cuesta, Anibal J.,Tang, Chiu C.,Yang, Sihai
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- Double-metal cyanide as an acid and hydrogenation catalyst for the highly selective ring-rearrangement of biomass-derived furfuryl alcohol to cyclopentenone compounds
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Herein, novel green synthetic routes to 4-hydroxy-2-cyclopentenone (HCP) and 2-cyclopentenone (CPE) from biomass-derived furfuryl alcohol via double-metal cyanide catalysis are proposed. For the synthesis of HCP, in comparison to conventional solid acids (i.e., Amberlyst-15), MOFs with coordinatively unsaturated metal ions as pure Lewis acid sites exhibit advantageous catalytic selectivity in the reaction under an N2 atmosphere in a bi-phasic water/n-hexane solvent system. FeZn and FeZn-P result in an HCP yield of 77.4% and 88.2%, respectively. For the CPE synthesis, the reaction conditions are the same as those for HCP, except a mono-phasic water solvent system and H2 atmosphere were employed. In addition to the acid-catalyzed rearrangement reaction, FeZn-DMC exhibits catalytic hydrogenation capability via heterolytic cleavage of the H-H bond over Zn-N frustrated Lewis pairs, and a CPE yield of 61.5% is obtained. The DFT simulation indicates that the acid sites and catalytic acid sites are ascribed to the tri-coordinatively unsaturated Zn2+ site (Zn(N)3) on the catalyst surface. Moreover, the DMC catalyst shows excellent stability and recycling performance. This work not only provides an efficient and green catalytic system for CPE and HCP preparation but also demonstrates the interesting bifunctional catalysis of both acid and hydrogenation catalysis over DMC.
- Deng, Qiang,Deng, Shuguang,Gao, Rui,Li, Xiang,Lu, Chenxi,Tong, Zhikun,Wang, Jun,Yu, Lian,Zeng, Zheling,Zou, Ji-Jun
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p. 2549 - 2557
(2020/05/28)
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- Rediscovering aminal chemistry: Copper(ii) catalysed formation under mild conditions
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Aminals, the N,N analogues of acetals, have been thoroughly explored in organic chemistry, with a particular focus on heteroaromatic aldehyde lithiation. Nevertheless, the existing methodologies for their formation typically employ harsh conditions limiting their usefulness. In this work, we present an efficient and mild methodology for the preparation of aminals from aromatic aldehydes, including furanic platforms. These mild conditions allowed ease of access to a plethora of aminals and as such we set out to explore previously unaccessible potential applications. By studying the stability of various aminals, we were able to develop a simple aldehyde protecting group based on a commercial diamine which is deprotected under mind conditions. We developed a protocol for the scavenging of genotoxic aldehydes by taking advantage of our methodology and a diamine resin, as well as early studies on the development of a stimuli-responsive release system using a salycil aldehyde derived aminal. This journal is
- Afonso, Carlos A. M.,António, Jo?o P. M.,Gomes, Rafael F. A.,Mendon?a, Ricardo,Pereira, Juliana G.
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supporting information
p. 7484 - 7490
(2020/11/18)
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- Continuous synthesis method of 2-cyclopentene-1-ketone
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The invention provides a continuous synthesis method of 2-cyclopentene-1-ketone. The continuous synthesis method comprises the steps that a continuous reaction device is loaded with a catalyst, then cyclopentene, an oxidizing agent and a solvent are continuously conveyed into the continuous reaction device for an oxidation reaction, and the 2-cyclopentene-1-ketone is continuously discharged. The continuous synthesis method of the 2-cyclopentene-1-ketone has the advantages that in the presence of the catalyst and the solvent, the cyclopentene is used as a starting material, and the cyclopenteneand the oxidizing agent are directly subjected to the oxidation reaction, which can avoid the generation of a large amount of halogen-containing three wastes; the entire continuous synthesis processcan effectively inhibit the occurrence of safety risks during scale-up production in the continuous reaction device; in addition, after the reaction is completed, a product system of the oxidation reaction is simply concentrated to obtain the target product (2-cyclopentene-1-ketone), thereby greatly improving the purity ( up to 98% or above) and separation rate (up to 79%) of the product, and making the scale-up production easy.
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Paragraph 0031-0047
(2019/11/20)
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- PINO/NHPI-mediated selective oxidation of cycloalkenes to cycloalkenones: Via a photo-electrochemical method
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The selective photo-electrochemical oxidation of cyclohexene to 2-cyclohexene-1-one was successfully performed with excellent Faraday efficiency (>99%) via indirect oxidation with a PINO/NHPI mediator and O2 on a BiVO4/WO3 photoanode under low applied bias.
- Tateno, Hiroyuki,Miseki, Yugo,Sayama, Kazuhiro
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p. 9339 - 9342
(2019/08/08)
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- Efficient and Selective Ni/Al2O3–C Catalyst Derived from Metal–Organic Frameworks for the Hydrogenation of Furfural to Furfuryl Alcohol
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Abstract: Currently, precious metal catalysts or toxic copper-chromium catalysts are widely used in the catalytic hydrogenation of furfural. In this study, the selective hydrogenation of furfural to furfuryl alcohol was performed over alumina-carbon matrix embedded Ni nanoparticles catalyst. The Ni-loaded metal organic framework precursors were synthesized by reverse microemulsion method (water in oil), then the Ni/Al2O3–C catalysts were obtained by pyrolysis under a nitrogen atmosphere. Various characterizations including XRD, XPS, SEM, TEM, TPR, TPD and TG were carried out to reveal the microstructure and chemical composition of the prepared samples. The results showed that the hexagonal platelet structure and the smaller nickel nanoparticle size(~ 8?nm) benefits from the alumina–carbon matrix support, which helped the uniform dispersion and prevented it from accumulation at high temperatures. In addition, the catalyst performance was greatly affected by the calcination conditions and metal loading. At optimized operating conditions, 98.7% conversion of furfural and 92% yield of furfuryl alcohol could be achieved over Ni0.15/Al2O3–C catalyst in the liquid phase hydrogenation reaction with a good reusability. Graphical Abstract: [Figure not available: see fulltext.].
- Hu, Feng,Wang, Yuan,Xu, Siquan,Zhang, Zongqi,Chen, Yuan,Fan, Jingdeng,Yuan, Hui,Gao, Lijing,Xiao, Guomin
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- Method for cyclization conversion of furfuryl alcohol to form cyclopentenone
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The invention discloses a method for cyclization conversion of furfuryl alcohol to form cyclopentenone. The method comprises the following steps: mixing furfuryl alcohol with a solvent mixture according to a mass ratio of 1:(20-60) g/ml, and adding Lewis solid acid as a catalyst to carry out a reaction in an inert gas or hydrogen environment, wherein the reaction temperature is 120-160 DEG C. Through adoption of the technical scheme, 4-hydroxy-2-cyclopentenone/2-cyclopentenone is obtained by adopting a rearranging hydrolysis/hydrogenolysis method, so that the process is simple, operation is convenient, reaction conditions are mild, and the catalyst is cheap and easily available and can be recycled for multiple times. The method is easy to industrialize, excessive dependence on petroleum isreduced by the raw materials, and the environmental problems of halogen pollution are reduced. When the conversion rate of furfuryl alcohol for synthesizing 4-hydroxy-2-cyclopentenone reaches 95.2%,the yield is up to 88.2%; and when the conversion rate of furfuryl alcohol for synthesizing 2-cyclopentenone is up to 96%, the yield is up to 52.3%.
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Paragraph 0025-0030
(2019/10/01)
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- Highly efficient oxidation of cyclopentene catalyzed by magnetically recoverable Ca–Co ferrite spinels with high solvent selectivity
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The calcium doped CoFe2O4 spinels CaxCo1?xFe2O4 (x = 0, 0.1, 0.3, 0.5 and 0.7) were prepared by simple sol–gel auto-combustion method. The samples were characterized by X-ray diffractometry, Raman spectrometry, scanning and transmission electron microscopy, N2-physisorption and inductive coupled plasma-atomic emission spectroscopy. The samples have shown prominent activities in oxidation of cyclopentene using 30% hydrogen peroxide as oxidant. When compared to the pristine CoFe2O4, the Ca-doped ones were more efficient having a conversion ranging from 72.1% to 100% and a H2O2 utilization efficiency range of 80.0–84.7%. When the calcium content was 0.3 and above, the cyclopentene was quantitatively converted to cyclopentenone at 60 °C for 8 h reaction. More interestingly, the catalyst has shown great solvent selectivity with respect to the product distribution. Finally, the catalyst can be easily separated magnetically for reuse and no obvious loss of activity was observed after five consecutive runs.
- Bo, Lili,Hu, Yusen,Zhang, Zhixia,Balanay, Mannix,Fan, Haiyan,Tong, Jinhui
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p. 182 - 188
(2018/08/17)
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- IBX as a catalyst for dehydration of hydroperoxides: Green entry to α,β-unsaturated ketones: Via oxygenative allylic transposition
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A catalytic transformation of allylic hydroperoxides into α,β-unsaturated carbonyl compounds using IBX as a dehydration catalyst is described. The combination of a singlet oxygen ene reaction and the IBX-catalyzed dehydration provides α,β-unsaturated carbonyl compounds from alkenes via oxygenative allylic transposition with H2O as the only byproduct.
- Kuga, Tetsuya,Sasano, Yusuke,Iwabuchi, Yoshiharu
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supporting information
p. 798 - 801
(2018/02/06)
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- Synthesis of Enones and Enals via Dehydrogenation of Saturated Ketones and Aldehydes
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A general, efficient and economic palladium-catalyzed dehydrogenation to form enones or enals has been developed. The approach possesses extremely broad substrate scope including various linear or cyclic saturated ketones and aldehydes. The protocol is ligand-free, and molecular oxygen is used as the sole clean oxidant in the reaction. Due to mild reaction conditions, good functional group compatibility, and versatile utilities of enones and enals, the method can be applied in the late-stage synthesis of natural products, pharmaceuticals and fine chemicals. (Figure presented.).
- Pan, Gao-Fei,Zhu, Xue-Qing,Guo, Rui-Li,Gao, Ya-Ru,Wang, Yong-Qiang
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p. 4774 - 4783
(2018/11/10)
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- Preparation of Cyclobutene Acetals and Tricyclic Oxetanes through Photochemical Tandem and Cascade Reactions
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We describe a photochemical reaction using two starting materials, a cyclopent-2-enone and an alkene, which are transformed in a controlled manner via the initial [2+2]-photocycloaddition adducts into cyclobutene aldehydes (conveniently trapped as stable acetals) or unprecedented angular tricyclic 4:4:4 oxetane-containing skeletons. These compounds are formed through tandem or triple cascade photochemical reaction processes, respectively. Small libraries of each compound class were prepared, thus suggesting that this photochemistry approach opens new opportunities for synthesis design and for widening molecular diversity.
- Buendia, Julien,Chang, Zong,Eijsberg, Hendrik,Guillot, Régis,Frongia, Angelo,Secci, Francesco,Xie, Juan,Robin, Sylvie,Boddaert, Thomas,Aitken, David J.
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p. 6592 - 6596
(2018/04/30)
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- Efficient conversion of furfural into cyclopentanone over high performing and stable Cu/ZrO2 catalysts
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Currently, biomass transformation to produce high value-added chemicals and liquid biofuels is attracting more and more interest by the virtue of its importance in the sustainable development of human society. Herein, we reported the conversion of furfural (FFA) into cyclopentanone (CPO) in water over high performing and stable Cu/ZrO2 catalysts prepared by our developed one-pot reduction-oxidation method. It was demonstrated that surface structures and catalytic performances of catalysts could be delicately adjusted by varying the calcination temperatures for catalyst precursors. Especially, an appropriate calcination temperature of 500 °C could significantly enhance the interactions between surface Cu species and the ZrO2 support, thus greatly facilitating the formation of Cu+-O-Zr-like structure at the metal-support interface, and the resulting Cu/ZrO2 catalyst showed a superior catalytic performance with a high CPO yield of 91.3% under mild reaction conditions (i.e. a low hydrogen pressure of 1.5 MPa and 150 °C) to other metal oxides supported copper catalysts prepared by the conventional impregnation. It was revealed that in addition to surface acidic sites, surface Cu+/(Cu°+Cu+) ratio also played a key role in promoting the formation of CPO in the present Cu/ZrO2 catalytic system.
- Zhang, Yifeng,Fan, Guoli,Yang, Lan,Li, Feng
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p. 117 - 126
(2018/06/01)
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- Hydrodeoxygenation of cellulose pyrolysis model compounds using molybdenum oxide and low pressure hydrogen
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A molybdenum oxide catalyst in a low pressure hydrogen atmosphere was used for the hydrodeoxygenation (HDO) of pulsed injections of cellulose pyrolysis model compounds to examine reaction products. Higher catalyst loadings (≥20: 1 catalyst: cellulose injection) in the HDO reactor were found to preferentially produce alkanes, while at lower loadings (≤10: 1 catalyst: cellulose injection) alkene selectivity was increased. However, as the amount of catalyst was decreased, the pyrolysis vapors were not completely deoxygenated. The HDO of monofunctional oxygenated C4 compounds found hydroxyl groups to be the most readily reacted and ether linkages to be the most recalcitrant. In general, the reactivity towards deoxygenation of the tested oxygen-containing functional groups was observed to be C-OH > C=O > C-OC. Several cellulose pyrolysis model compounds were also tested, including methyl glyoxal, glycolaldehyde, furfural, 5-hydroxymethylfurfural, and levoglucosan, and found the same general trend to occur, except for levoglucosan, which was totally reacted and did not yield any oxygenated low molecular weight compounds despite containing two ether linkages. Across the compounds, the general reaction pathway was observed to include carbonyl/alcohol hydrogenation/dehydrogenation, deoxygenation, and alkene isomerization and hydrogenation.
- Nolte, Michael W.,Saraeian, Alireza,Shanks, Brent H.
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supporting information
p. 3654 - 3664
(2017/08/10)
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- Rhodium-Catalyzed Intermolecular Carbonylative [2 + 2 + 1] Cycloaddition of Alkynes Using Alcohol as the Carbon Monoxide Source for the Formation of Cyclopentenones
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A highly regioselective rhodium-catalyzed intermolecular carbonylative [2 + 2 + 1] cycloaddition of alkynes using alcohol as a CO surrogate to access 4-methylene-2-cyclopenten-1-ones has been developed. In this transformation, the alcohol performs multiple roles, including generating the Rh-H intermediate, functioning as the CO source, and assisting in the isomerization of the alkyne. Alkynes can act as both the olefin and the alkyne partner in the cyclopentenone core.
- Kim, Ju Hyun,Song, Taemoon,Chung, Young Keun
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supporting information
p. 1248 - 1251
(2017/03/14)
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- Effect of Cp*Iridium(III) Complex and acid co-catalyst on conversion of furfural compounds to cyclopentanones or straight chain ketones
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In this paper, Cp*Ir (III) Complex and acid co-catalyst system was developed. By using Cp*Ir and γ-Al2O3 (Lewis acid), 5-hydroxymethylfurfural (5-HMF) can be converted efficiently to 3-hydroxymethyl cyclopentanone (HCPN). Meanwhile, Cp*Ir and Br?nsted acid can promote conversion of 5-HMF to 1-Hydroxy-2,5-hexanedione (HHD). The effect of Lewis acid and Br?nsted acid on the hydrogenation of furan derivatives was studied. Mechanism of conversion of 5-HMF to HCPN was discussed in detail and mechanism proposed by our predecessors was revised. Instead of being an intermediate for the formation of HCPN, it is believed that, HHD is a product of another reaction pathway. HHD condensed via Aldol reaction to produce 3-methylcyclopenten-2-ol-1-one (MCP) instead of HCPN. Under the promotion of Lewis acid, 5-HMF firstly convert to the precursor of HHD. After that, the reaction is through 4 π-electrocyclic ring closure process and HCPN was formed ultimately. Furthermore, we found that our Cp*Ir and acid co-catalyst system is suitable for a variety of furfural compounds. By using Cp*Ir, Br?nsted acid can promote conversion of furfural compounds to straight chain ketones and Lewis acid can promote the rearrangement of furfural compounds to cyclopentanone derivatives.
- Xu, Yong-Jian,Shi, Jing,Wu, Wei-Peng,Zhu, Rui,Li, Xing-Long,Deng, Jin,Fu, Yao
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p. 266 - 273
(2017/07/13)
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- Selective oxidation of styrene catalyzed by cerium-doped cobalt ferrite nanocrystals with greatly enhanced catalytic performance
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The rare earth metal Ce-doped cobalt ferrite samples CexCo1?xFe2O4 (x?=?0.1, 0.3, 0.5) were prepared by the sol–gel autocombustion route. The as-prepared samples were characterized by X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, ICP–atomic emission spectroscopy, and N2 physisorption. Their catalytic performance was evaluated in oxidation of styrene using hydrogen peroxide (30%) as oxidant. Compared with pristine CoFe2O4, the Ce-doped samples were found to be more efficient catalysts for the oxidation of styrene to benzaldehyde, with greatly enhanced catalytic performance. Especially, when Ce0.3Co0.7Fe2O4 was used as catalyst, 90.3% styrene conversion and 91.5% selectivity for benzaldehyde were obtained at 90?°C for 9?h reaction. The catalyst can be magnetically separated easily for reuse, and no obvious loss of activity was observed when it was reused in five consecutive runs.
- Tong, Jinhui,Li, Wenyan,Bo, Lili,Wang, Huan,Hu, Yusen,Zhang, Zhixia,Mahboob, Abdulla
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p. 474 - 481
(2016/11/18)
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- Towards quantitative and scalable transformation of furfural to cyclopentanone with supported gold catalysts
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Given the vital importance of furfural (FFA) upgrading towards a sustainable bio-based economy, an eco-friendly aqueous route to produce a sole valuable product from FFA is highly desirable. We herein describe an efficient approach to quantitatively convert FFA into cyclopentanone (CPO) in neat water, employing H2 as the clean reductant and supported gold nanoparticles as a simple yet versatile catalyst. The use of anatase TiO2 featuring only mild Lewis acidic sites as the underlying support is essential, not only for preventing undesirable side reactions, but also for attaining high CPO selectivity. The feasibility of using biogenic CPO and CO2 as benign carbon sources to synthesize the industrially important feedstock dimethyl adipate is also demonstrated.
- Zhang, Gao-Shuo,Zhu, Ming-Ming,Zhang, Qi,Liu, Yong-Mei,He, He-Yong,Cao, Yong
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p. 2155 - 2164
(2016/04/19)
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- Sequential Enzymatic Conversion of α-Angelica Lactone to γ-Valerolactone through Hydride-Independent C=C Bond Isomerization
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A case of hydride-independent reaction catalyzed by flavin-dependent ene-reductases from the Old Yellow Enzyme (OYE) family was identified. α-Angelica lactone was isomerized to the conjugated β-isomer in a nicotinamide-free and hydride-independent process. The catalytic cycle of C=C bond isomerization appears to be flavin-independent and to rely solely on a deprotonation–reprotonation sequence through acid–base catalysis. Key residues in the enzyme active site were mutated and provided insight on important mechanistic features. The isomerization of α-angelica lactone by OYE2 in aqueous buffer furnished 6.3 mm β-isomer in 15 min at 30 °C. In presence of nicotinamide adenine dinucleotide (NADH), the latter could be further reduced to γ-valerolactone. This enzymatic tool was successfully applied on semi-preparative scale and constitutes a sustainable process for the valorization of platform chemicals from renewable resources.
- Turrini, Nikolaus G.,Eger, Elisabeth,Reiter, Tamara C.,Faber, Kurt,Hall, Mélanie
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p. 3393 - 3396
(2016/12/27)
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- Production of 2,5-hexanedione and 3-methyl-2-cyclopenten-1-one from 5-hydroxymethylfurfural
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A novel approach for the production of 2,5-hexanedione (HDN) and 3-methyl-2-cyclopenten-1-one (3-MCO) from 5-hydroxymethylfurfural (HMF) by water splitting with Zn is reported for the first time. The use of high temperature water (HTW) conditions is the key for the efficient conversion of HMF to HDN and 3-MCO. Parameters regarding the Zn amount, temperature and reaction time are optimized and HDN and 3-MCO are produced in 27.3% and 30.5% yields, respectively. The roles of HTW and ZnO obtained by oxidation of Zn in water for the conversion of HMF, together with intermediate structures, are discussed to understand the mechanism of the reaction.
- Ren, Dezhang,Song, Zhiyuan,Li, Lu,Liu, Yunjie,Jin, Fangming,Huo, Zhibao
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supporting information
p. 3075 - 3081
(2016/06/06)
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- Bismuth-substituted "sandwich" type polyoxometalate catalyst for activation of peroxide: Umpolung of the peroxo intermediate and change of chemoselectivity
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The epoxidation of alkenes with peroxides by WVI, MoVI, VV, and TiIV compounds is well established, and it is well accepted that the active intermediate peroxo species are electrophilic toward nucleophilic substrates. Polyoxotungstates, for example, those of the "sandwich" structure, [WZn(TM-L)2(ZnW9O34)2]q- in which TM = transition metal and L = H2O, have in the past been found to be excellent epoxidation catalysts. It has now been found that substituting the Lewis basic BiIII into the terminal position of the "sandwich" polyoxometalate structure to yield [Zn2BiIII2(ZnW9O34)2]14- leads to an apparent umpolung of the peroxo species and formation of a nucleophilic peroxo intermediate. There are two lines of evidence that support the formation of a reactive nucleophilic peroxo intermediate: (1) More electrophilic sulfoxides are more reactive than more nucleophilic sulfides, and (2) nonfunctionalized aliphatic alkenes and dienes showed ene type reactivity rather than epoxidation pointing toward "dark" formation of singlet oxygen from the nucleophilic intermediate peroxo species. Allylic alcohols reacted much faster than alkenes but showed chemoselectivity toward C-H bond activation of the alcohol and formation of aldehydes or ketones rather than epoxidation. This explained via alkoxide formation at the BiIII center followed by oxidative β-elimination.
- Amanchi, Srinivasa Rao,Khenkin, Alexander M.,Diskin-Posner, Yael,Neumann, Ronny
-
p. 3336 - 3341
(2015/06/16)
-
- Selective conversion of furfural to cyclopentanone or cyclopentanol using different preparation methods of Cu-Co catalysts
-
Cu-Co catalysts, prepared by a co-precipitation method (CP) and an oxalate sol-gel method (OG), can selectively convert furfural (FFA) to cyclopentanone (CPO) or cyclopentanol (CPL), respectively. The conversion of FFA to CPO or CPL by Cu-Co catalysts were studied in aqueous solutions. We found that the product distribution was influenced by the catalyst support, Cu loading, calcination temperature, hydrogen pressure, the number of times the catalyst was reused and the preparation method of the catalyst. The surface morphology, surface area and composition of the catalysts were studied by XRD, XPS, BET, ICP-AES and TEM characterization. We found that there was a strong interaction between Cu and Co. Cu0, Cu2O and Co0 were the main active catalyst phases on the surfaces of the catalysts, but the amounts were different in the different catalysts. Cu0, Co0 and Cu2O were the active hydrogenation species, and Cu2O also played the role of an electrophile or Lewis acid to polarize the CO bond via lone pair electrons on the oxygen atom. According to XRD and XPS, the main phases on the surface of the CP catalysts were Cu0 and Cu2O. The hydrogenation activity of the CP catalyst was relatively weak and the main product was CPO. In contrast, the hydrogenation activity of the OG catalyst was high and the main product was the fully hydrogenated product CPL due to the main active phases of Co0 and Cu2O on the surface of the OG catalyst. At lower hydrogen pressure (2 MPa) and lower Cu loadings (2% for OG, 5% for CP), we obtained the highest yield of 67% CPO and 68% CPL, respectively. This journal is
- Li, Xing-Long,Deng, Jin,Shi, Jing,Pan, Tao,Yu,Xu, Hua-Jian,Fu, Yao
-
p. 1038 - 1046
(2015/03/04)
-
- One-pot synthesis of a hierarchical microporous-mesoporous phosphotungstic acid-HKUST-1 catalyst and its application in the selective oxidation of cyclopentene to glutaraldehyde
-
A hierarchical microporous-mesoporous metal-organic framework of HKUST-1(Cu)-encapsulated phosphotungstic acid (HPW) material, referred to as HPWs@Meso-HKUST-1, is prepared by a one-pot synthesis method using cetyltrimethylammonium bromide as the supramolecular template. The addition of HPWs to the synthesis mixture of hierarchical porous HKUST-1 results in the direct encapsulation of HPWs inside the mesopores of the HKUST-1 structure, with a homogeneous distribution over the HKUST-1 crystals, which is confirmed by XRD, FT-IR, N2 adsorption, UV-Vis DRS, and TEM. FT-IR-CO adsorption experiments indicated that additional Lewis acid sites were present in the HPWs@Meso-HKUST-1 sample. The novel heterogeneous catalyst demonstrates excellent catalytic performance for the selective oxidation of cyclopentene (CPE) to glutaraldehyde (GA) using tert-butyl hydroperoxide and acetonitrile (MeCN) as the oxidant and solvent, respectively. The high activity of the catalyst is attributed to the mesostructure of the catalyst and the nature and appropriate abundance of the HPWs - being highly dispersed with the addition of Lewis sites. After a reaction for 36 h, the 30% wt% HPWs@Meso-HKUST-1 catalyst exhibits a CPE conversion of 92.5% and a high GA yield of 73%. Furthermore, the HPWs@Meso-HKUST-1 material is sufficiently stable to prevent the leaching of HPWs, and behaves as a true heterogeneous catalyst that can be repeatedly recycled without sustaining a loss of activity and selectivity in the selective oxidation of CPE.
- Yang, Xinli,Qiao, Liming,Dai, Weilin
-
p. 1875 - 1885
(2015/11/17)
-
- Synthesis of α,β-unsaturated carbonyl compounds via a visible-light-promoted organocatalytic aerobic oxidation
-
α,β-Unsaturated ketones and aldehydes have been synthesized from their corresponding silyl enol ethers in a straightforward protocol involving a visible-light promoted organocatalytic, aerobic oxidation reaction. A cheap organic dye was used catalytically in these reactions as the photosensitizer.
- Zhang, Junlin,Wang, Leming,Liu, Qi,Yang, Zhen,Huang, Yong
-
p. 11662 - 11664
(2013/12/04)
-
- Conversion of furfural into cyclopentanone over Ni-Cu bimetallic catalysts
-
The conversion of furfural into cyclopentanone over Ni-Cu bimetallic catalysts was studied under hydrogen atmosphere. Furfuryl alcohol, 4-hydroxy-2-cyclopentenone and 2-cyclopentenone were verified as three key intermediates. Rearrangement of the furan ring was independent of hydrogenation, starting from furfuryl alcohol rather than furfural. The opening and closure of the furan ring were closely related to the attack of a H2O molecule on the 5-position of furfuryl alcohol. Prior hydrogenation of the aldehyde group accounted for the different reactivity of furfural and furfuryl alcohol. The high selectivity of cyclopentanone was ascribed to the presence of 2-cyclopentenone.
- Yang, Yanliang,Du, Zhongtian,Huang, Yizheng,Lu, Fang,Wang, Feng,Gao, Jin,Xu, Jie
-
p. 1932 - 1940
(2013/09/24)
-
- Mesoporous carbon nitride synthesized by nanocasting with urea/formaldehyde and metal-free catalytic oxidation of cyclic olefins
-
Mesostructured carbon nitride has been synthesized by nanocasting method with urea/formaldehyde as carbon and nitrogen sources by using disk-shaped 2D hexagonal mesoporous silica (INC-2) as a hard template. The resulted mesoporous carbon nitride (UF-MCN) was characterized as a graphitic structure with hexagonal pores of 3-4 nm and short channels in the submicron range. The catalytic oxidation ability of UF-MCN was demonstrated in the metal-free oxidation of cyclic olefins with hydrogen peroxide. The conversions for cyclopentene, cyclohexene and cis-cyclooctene were obtained in the range of 65-80% and selectivities onto epoxides were 40-90%, respectively. The UF-MCN could illustrate the considerable catalytic oxidation activities due to the existence of surface oxygen species.
- Min, Byung-Hoon,Ansari, Mohd Bismillah,Mo, Yong-Hwan,Park, Sang-Eon
-
p. 156 - 163
(2013/08/24)
-
- Aerobic oxidation of cycloalkenes catalyzed by iron metal organic framework containing N-hydroxyphthalimide
-
Iron metal organic framework [Fe(BTC)] loaded with N-hydroxyphthalimide (NHPI) promotes the aerobic oxidation of (cyclo)alkenes to give variable percentages of allylic oxidation products and the corresponding epoxide, dependidng on the nature of the substrate. In the case of cyclopentene and cyclohexene, aerobic oxidation catalyzed by NHPI/Fe(BTC) renders their corresponding unsaturated cyclic alcohol and ketone with 97% selectivity in 5 h at 6% and 12% conversion, respectively. Under the same experimental conditions, cyclooctene exhibited 95% selectivity toward the formation of cyclooctene oxide with 2% of cyclooctenol/one at 4 h. Cycloheptene as susbstrate exhibits an intermediate behavior, and the aerobic oxidation catalyzed by NHPI/Fe(BTC) leads to the formation of cycloheptenol/cycloheptenone with 77% selectivity, accompanied by 23% of cycloheptene oxide at 4 h. Further experiments with non-symmetric olefins exhibited also a mixture of products including epoxides and allyic products. A mechanism to explain these experimental results has been proposed.
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
-
experimental part
p. 259 - 265
(2012/06/01)
-
- L-Proline-derived ligands to mimic the '2-His-1-carboxylate' triad of the non-haem iron oxidase active site
-
Non-haem iron(II) oxidases (NHIOs) catalyse a variety of oxidative transformations in biology. The iron-binding environment of the NHIO active site typically incorporates a '2-His-1-carboxylate' facial triad of amino acid side-chains, a motif that has emerged as a defining feature of the enzyme family. Towards the goal of biomimetic, iron-mediated C-H activation we have synthesized a series of peptidomimetic ligands from l-proline. By coupling l-proline to 2,6-bis(bromomethyl)pyridine, 2-(bromomethyl)-6-((tert- butyldimethylsilyloxy)methyl)pyridine and picolinic acid, we have generated several new ligand architectures designed to complex with iron(II) and mimic the NHIO active site. The resulting iron complexes promote modest levels of alkene dihydroxylation and allylic oxidation using hydrogen peroxide as oxidant.
- Dungan, Victoria J.,Wong, Shwo Mun,Barry, Sarah M.,Rutledge, Peter J.
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experimental part
p. 3231 - 3236
(2012/06/01)
-
- CO2 activation and promotional effect in the oxidation of cyclic olefins over mesoporous carbon nitrides
-
Mesoporous carbon nitrides (MCN) were prepared by a nano-casting method using mesoporous silica as a template with different carbon and nitrogen sources like melamine only (MS-MCN), urea-formaldehyde (UF-MCN) and melamine-glyoxal (MG-MCN). These mesoporous carbon nitride materials possess nitrogen moieties which behave like a CO2-philic surface facilitating oxidation of cyclic olefins by molecular oxygen in the co-presence of CO2 below supercritical conditions. The co-presence of CO2 augmented the conversions of cyclic olefins at low pressures of CO2, depicting a promotional effect. Approaches towards quantification of promotional effects and insights into the promotional aspects have been studied.
- Ansari, Mohd Bismillah,Min, Byung-Hoon,Mo, Yong-Hwan,Park, Sang-Eon
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experimental part
p. 1416 - 1421
(2011/08/03)
-
- Old yellow enzyme-catalyzed dehydrogenation of saturated ketones
-
Enzymes from extremophiles have always been of great interest for biotechnology because of their ruggedness against various stress factors. We have isolated, cloned, heterologously expressed and characterized a thermostable old yellow enzyme (OYE) from Geobacillus kaustophilus. In addition to the expected 'enone' reduction, GkOYE also catalyzes the reverse reaction, i.e., the desaturation of C-C bonds adjacent to a carbonyl to give the corresponding α,β-unsaturated ketone. The reaction proceeds at the expense of molecular oxygen without the need for a nicotinamide cofactor and represents an environmentally benign alternative to known chemical dehydrogenation methods.
- Schittmayer, Matthias,Glieder, Anton,Uhl, Michael K.,Winkler, Andreas,Zach, Simone,Schrittwieser, Joerg H.,Kroutil, Wolfgang,MacHeroux, Peter,Gruber, Karl,Kambourakis, Spiros,Rozzell, J. David,Winkler, Margit
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experimental part
p. 268 - 274
(2011/04/22)
-
- Vanadium phosphorus oxide modified by silver doping: A highly effective catalyst for allylic oxidation of cycloolefins
-
Allylic oxidation of cycloolefins was carried out over Ag-VPO catalyst using tert-butyl hydroperoxide (TBHP) as oxidant in argon atmosphere, under our reaction conditions, attack of the activated C-H bonds was preferred instead of the epoxidation of C=C bond and corresponding α, β-enones were obtained as the main products. It is a high yielding, safe and eco-friendly method.
- Liu, Junhua,Wang, Fang,Ma, Zhenmao,Lin, Jun,Gu, Zhenggui
-
experimental part
p. 103 - 107
(2012/03/09)
-
- Cu(II) bromide catalyzed oxidation of aldehydes and alcohols
-
A variety of aromatic, aliphatic and conjugated aldehydes and alcohols were transformed to the corresponding carboxylic acids and ketones with a quantitative conversion in high yields with 70% t-BuOOH solution in water in the presence of catalytic (5 mol%) amounts of CuBr2 under room temperature conditions. The conversion of 4-methoxybenzaldehyde to 4-methoxybenzoic acid is extremely facile in MeCN at ambient temperature in the presence of 5 mol% CuBr2 and 2 equiv. 70% t-BuOOH (water) as the oxidant. Oxidation with t-BuOOH (water) alone in MeCN was found to be negligible. The scope of our catalytic system is applicable for a wide range of aromatic, conjugated and aliphatic substrates. These aldehydes were converted to the corresponding carboxylic acids in good isolated yields in reasonable times. It is pertinent to mention here that mild halogenic oxidants like hypochlorites, chlorites and NBS are not suitable for substrates with electron-rich aromatic rings, olefinic bonds and secondary hydroxyl groups. Substitutions at different positions on the phenyl ring do not hinder the reaction, although the reaction time is affected. Oxidation of α,β unsaturated derivatives resulted in the formation of the expected acid in good yield. In addition, the transformation of secondary alcohols to ketones is extremely facile. No recemization was observed for menthone. This method possesses a wide range of capabilities since it can be used with other functional groups which may not tolerate oxidative conditions, involves fairly simple method for work-up, exhibits chemoselectivity and proceeds under ambient conditions. The resulting products are obtained in good yields within reasonable time.
- Das, Rima,Chakraborty, Debashis
-
experimental part
p. 437 - 442
(2012/01/30)
-
- Rate coefficients and products for gas-phase reactions of chlorine atoms with cyclic unsaturated hydrocarbons at 298 K
-
Rate coefficients for the reaction of Cl atoms with cycloalkenes have been determined using the relative rate method, at 298 K and atmospheric pressure of N2. Reference molecule was n -hexane, and the concentrations of the organics were followed by gas chromatographic analysis. Cl atoms were prepared by photolysis of trichloroacetyl chloride at 254 nm. The relative rates of reactions of Cl atoms with cycloalkenes, with, respect to M-hexane, are measured as 1.12 ±0.38, 1.31 ±0.14, and 1.69±0.18forcyclopentene, cyclohexene, and cycloheptene, respectively. Considering the absolute value of the rate coefficient of the reaction of Cl atom with n-hexane as 3.03 ± 0.06 × 10-10 cm3 molecule-1 s -1, the rate coefficient values for cyclopentene, cyclohexene, and cycloheptene are calculated, to be (3.39 ± 1.08) × 10 -10, (3.97 ±0.43) × 10-10, and (5.12 ± 0.55) × 10-10 cm3 molecule-1 S -1', respectively. The experiments for each, molecule were repeated six to eight times, and the slopes and the rate coefficients given above are the average values of these measurements, and the quoted error includes 2σ as well as all other uncertainties in the measurement and calculations. The rate coefficient increases linearly with the number of carbon atoms, with an increment per additional CH2 group being (8.7 ± 1.6) × 11-12 cm3 molecule-1 s-1. Chloroketones and chloroalcohols, along with unsaturated, ketones and alcohols, were found to be the major products of Cl-atom-initiated oxidation of cycloalkenes in the presence of air. The atmospheric implications of these results are discussed, along with a comparison with the reported structure activity relationships.
- Sharma,Pushpa,Dhanya,Naik,Bajai
-
body text
p. 98 - 105
(2011/06/21)
-
- Retro-diels-alder reactions of masked cyclopentadienones catalyzed by heterogeneous Bronsted acids
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The zeolite H-Beta catalyzes the retro-Diels-Alder reaction of a range of cyclopentadiene cyclo-adducts at moderate temperatures and ambient pressure, in the presence of an active dienophile. The active catalyst was identified and optimum reaction conditions established after screening a range of zeolites in the retro-Diels-Alder reaction of the cyclopentadiene adduct of cyclopentenone. Our results suggest that retro-Diels-Alder reactions of tricyclodecadienones are catalyzed by Bronsted acids and the high catalytic performance of H-Beta catalysts can be ascribed to the optimal balance between the number of acid sites and their strength as well as to the accessibility of these sites. The methodology was then applied to a series of alkyl derivatives of cyclopentadienylcyclopentenones to provide a viable alternative synthetic route to 4-alkylcyclopentenones and the versatility of the approach was demonstrated by the successful cycloreversion of N-cyclohexyl-2-azanorborn-5-ene. Copyright
- Demuynck, Anneleen L. W.,Levecque, Pieter,Kidane, Aklilu,Gammon, David W.,Sickle, Eugene,Jacobs, Pierre A.,De Vos, Dirk E.,Sels, Bert F.
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experimental part
p. 3419 - 3430
(2011/02/23)
-
- METHOD FOR PRODUCING CARBONYL COMPOUND AN PRO-OXIDANT USED FOR PRODUCTION OF CARBONYL COMPOUND
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The invention provides a process for the preparation of a carbonyl compound in high efficiency by oxidizing an alcohol. The process for the preparation of a carbonyl compound of the present invention includes a step of oxidizing an alcohol in the presence of a compound of the formula (I) or a derivative or a salt thereof, and an oxidant, wherein R1 and R2 independently represent hydrogen, a halogen, a nitro or acidic group, or an alkyl or alkoxy group, each of which optionally has a substituent, or R1 and R2 combine the two carbon atoms to which they are boned to form an aromatic ring.
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Page/Page column 15-16
(2009/08/16)
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- 2-iodoxybenzenesulfonic acid as an extremely active catalyst for the selective oxidation of alcohols to aldehydes, ketones, carboxylic acids, and enones with oxone
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Electron-donating group-substituted 2-iodoxybenzoic acids (IBXs) such as5-Me-IBX (1g), 5-MeO-IBX (1h), and 4,5-Me2-IBX were superior to IBX 1a as catalysts for the oxidation of alcohols with Oxone (a trad emark of DuPont) under nonaqueous conditions, although Oxone was almost insoluble in most organic solvents. The catalytic oxidation proceeded more rapidly and cleanly in nitromethane. Furthermore, 2-iodoxybenzenesulfonic acid (IBS, 6a) was much more active than modified IBXs. Thus, we established a highly efficient and selective method for the oxidation of primary and secondary alcohols to carbonyl compounds such as aldehydes, carboxylic acids, and ketones with Oxone in nonaqueous nitromethane, acetonitrile, or ethyl acetate in the presence of 0.05-5molpercentof 6a, which was generated in situ from 2-iodobenzenesulfonic acid (7a) or its sodium salt. Cycloalkanones could be further oxidized to α,β- cycloalkenones or lactones by controlling the amounts of Oxone under the same conditions as above. When Oxone was used under nonaqueous conditions, Oxone wastes could be removed by simple filtration. Based on theoretical calculations, we considered that the relatively ionic character of the intramolecular hypervalent iodine-OSO2 bond of IBS might lower the twisting barrier of the alkoxyperiodinane intermediate 16.
- Uyanik, Muhammet,Akakura, Matsujiro,Ishihara, Kazuaki
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supporting information; experimental part
p. 251 - 262
(2009/06/28)
-
- Cage escape competes with geminate recombination during alkane hydroxylation by the diiron oxygenase AlkB
-
(Chemical Presented) AlkBstops the radical clock: Three structurally analogous radical-clock substrates with a large span in their rearrangement rates are hydroxylated by AlkB to afford similar amounts of rearranged (2) and unrearranged products (1). Such a result is in accord with radical rebound competing with cage escape of the geminate substrate radical. The results show that radical clocks can measure both the radical lifetime and the kinetics of cage escape.
- Austin, Rachel N.,Luddy, Kate,Erickson, Karla,Pender-Cudlip, Marilla,Bertrand, Erin,Deng, Dayi,Buzdygon, Ryan S.,Van Beilen, Jan B.,Groves, John T.
-
supporting information; experimental part
p. 5232 - 5234
(2009/04/04)
-
- An efficient procedure for the TEMPO-catalyzed oxidation of alcohols to aldehydes and ketones using ferric chloride hexahydrate as terminal oxidant
-
A simple, efficient procedure for the oxidation of alcohols by catalytic 2,2,6,6-tetramethyl-piperidyl-l-oxy (TEMPO) was developed using FeCl 3·6H2O as the terminal oxidant. The reaction gives high yield of the corresponding aldehydes and ketones with no over oxidation to the acid.
- Kumar, R. Senthil,Karthikeyan,Perumal, Paramasivan T.
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p. 720 - 725
(2008/09/21)
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- Studies towards the synthesis of the bicyclic 3,8-secotaxane diterpenoid system using a ring closing metathesis strategy
-
Molecular modelling studies on the interations between taxanes and tubulins, developed by us, revealed that modified Taxuspines U and X could adopt a conformation similar to that of the bioactive conformation of paclitaxel and could be well accommodated within the proposed model. Accordingly, simplified Taxuspine U and X analogues have been rationally designed and their bicyclic 3,8-secotaxane diterpenoids intermediates have been synthesized through an approach that involves ring closing metathesis (RCM) as the key step for the macrocycle formation. Extensive studies on RCM have been performed using chemically diverse substrates, outlining the influence in the macrocyclization of the presence and position of functionalities, the molecular constraints and the importance of the site of ring closure.
- Renzulli, Michela L.,Rocheblave, Luc,Avramova, Stanislava I.,Galletti, Elena,Castagnolo, Daniele,Tafi, Andrea,Corelli, Federico,Botta, Maurizio
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p. 497 - 509
(2007/10/03)
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- Process development of (1S,2S,5R,6S)-spiro[bicyclo[3.1.0]hexane-2′, 5′-dioxo-2,4′-imidazolidine]-6-carboxylic acid, (R)-α- methylbenzenemethanamine salt (LSN344309)
-
Process development and a pilot-plant process for the synthesis of 4 and its resolution to obtain (1S,2S,5R,6S)-spiro[bicyclo[3.1.0]hexane-2′, 5′-dioxo-2,4′-imidazolidine]-6-carboxylic acid, (R)-α- methylbenzenemethanamine salt (5) are described. Starting from the inexpensive raw 2-cyclopenten-1-one and sulfur ylide 1 the racemic bicyclo keto ester 2 was synthesized. Reaction of 2 with potassium cyanide and ammonium carbonate under Buecherer-Berg's reaction conditions affords racemic 3 in 80% yield. Hydrolysis of 3 followed by the resolution with (R)-(+)-α- methylbenzylamine gave 4 in excellent yield and purity under optimized conditions. The improvement of the original discovery process to accommodate safety and environmental requirements for scale-up in manufacturing facilities is also discussed.
- Rasmy, Ossama M.,Vaid, Radhe K.,Semo, Michael J.,Chelius, Erik C.,Robey, Roger L.,Alt, Charles A.,Rhodes, Gary A.,Vicenzi, Jeffery T.
-
-
- CATALYTICALLY ACTIVE COMPOSITION AND THE USE THEREOF IN DEHYDRATION METHODS
-
The invention relates to a catalytically active composition containing Pd and Bi as active constituents, and at least one element selected from the group (a) consisting of Rh, Au, Sb, V, Cr, W, Mn, Fe, Co, Ni, Na, Cs and Ba; or Pd, Rh and Bi, and optionally an element selected from the group (a') consisting of Au, Sb, V, Cr, W, Mn, Fe, Co, Ni, Pt, Cu, Ag, Na, Cs, Mg, Ca and Ba. The invention also relates to a method for dehydrating hydrocarbons, preferably oxofunctionalised hydrocarbons such as cyclopentanone, cyclohexanone and isovaleraldehyde, by means of the catalytically active composition.
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Page/Page column 33-34
(2008/06/13)
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- METHOD FOR DEHYDROGENATION OF CARBONYL COMPOUNDS
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A method for the production of alpha, beta unsaturated acyclic or cyclic carbonyl compounds by hydrogenation of corresponding saturated carbonyl compounds in a gaseous phase on a heterogeneous dehydrogenation catalyst, characterized in that the dehydrogenation catalyst contains platinum and/or palladium and tin on an oxidic carrier.
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Page/Page column 21; 22
(2010/02/10)
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- Pd(OH)2/C-mediated selective oxidation of silyl enol ethers by tert-butylhydroperoxide, a useful method for the conversion of ketones to α,β-enones or β-Silyloxy-α,β-enones
-
(Chemical Equation Presented) Pd(OH)2-catalyzed oxidation of silyl enol ethers by t-BuOOH gives either β-silyloxy-α,β-enones or α,β-enones in good yields depending on the base used.
- Yu, Jin-Quan,Wu, Hai-Chen,Corey
-
p. 1415 - 1417
(2007/10/03)
-
- Semivolatile and volatile compounds in combustion of polyethylene
-
The evolution of semivolatile and volatile compounds in the combustion of polyethylene (PE) was studied at different operating conditions in a horizontal quartz reactor. Four combustion runs at 500 and 850°C with two different sample mass/air flow ratios and two pyrolytic runs at the same temperatures were carried out. Thermal behavior of different compounds was analyzed and the data obtained were compared with those of literature. It was observed that α,ω-olefins, α-olefins and n-paraffins were formed from the pyrolytic decomposition at low temperatures. On the other hand, oxygenated compounds such as aldehydes were also formed in the presence of oxygen. High yields were obtained of carbon oxides and light hydrocarbons, too. At high temperatures, the formation of polycyclic aromatic hydrocarbons (PAHs) took place. These compounds are harmful and their presence in the combustion processes is related with the evolution of pyrolytic puffs inside the combustion chamber with a poor mixture of semivolatile compounds evolved with oxygen. Altogether, the yields of more than 200 compounds were determined. The collection of the semivolatile compounds was carried out with XAD-2 adsorbent and were analyzed by GC-MS, whereas volatile compounds and gases were collected in a Tedlar bag and analyzed by GC with thermal conductivity and flame ionization detectors.
- Font, Rafael,Aracil, Ignacio,Fullana, Andrés,Conesa, Juan A.
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p. 615 - 627
(2007/10/03)
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- Process for preparing cyclopentenone
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A process for the preparation of 2-cyclopentenones comprises reaction of hexendioic acids and/or their esters at 150-450 degrees C in the presence of solid oxide catalysts comprising 0.01-5 wt.% of at least one alkali oxide on an oxide support. A process for the preparation of 2-cyclopentenones of formula (1) comprises reaction of hexendioic acids and/or their esters of formula (2) or (3) at 150-450 degrees C in the presence of solid oxide catalysts comprising 0.01-5 wt.% of at least one alkali oxide on an oxide support. R1-R4 = H, 1-12C alkyl or alkenyl, 5-7C cycloalkyl or cycloalkenyl, aralkyl or aryl; R5, R6 = H, 1-12C alkyl, 5-7C cycloalkyl, aralkyl or aryl.
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-
-
- Process for producing 2-bromocyclopentanone
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There is provided a process for producing 2-bromocyclopentanone which process is characterized in that cyclopentanone is reacted with bromine in a biphasic mixture of water and an organic solvent.
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Page column 4
(2008/06/13)
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