- High catalytic activity of silicalite in gas-phase ketonisation of propionic acid
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Amorphous silica and crystalline silicalite (MFI structure) are demonstrated to be active and environmentally benign catalysts for propionic acid ketonisation at 450-500 °C to form 3-pentanone. The silicalite is particularly efficient, and its ketonisation selectivity is increased by base modification probably through generation of silanol nests.
- Bayahia, Hossein,Kozhevnikova, Elena,Kozhevnikov, Ivan
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- Synthesis, crystal structure and catalytic activity of ruthenium(II) carbonyl complexes containing ONO and ONS donor ligands
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Diamagnetic ruthenium(II) complexes of the type [Ru(L)(CO)(B)(EPh3)] [where E = As, B = AsPh3; E = P, B = PPh3, py (or) pip and L = dibasic tridentate ligands dehydroacetic acid semicarbazone (abbreviated as dhasc) or dehydroacetic acid phenyl thiosemicarbazone (abbreviated as dhaptsc)] were synthesized from the reaction of [RuHCl(CO)(B)(EPh3)2] (where E = As, B = AsPh3; E = P, B = PPh3, py (or) pip) with different tridentate chelating ligands derived from dehydroacetic acid with semicarbazide or phenylthiosemicarbazide. All the complexes have been characterized by elemental analysis, FT-IR, UV-Vis and 1H NMR spectral methods. The coordination mode of the ligands and the geometry of the complexes were confirmed by single crystal X-ray crystallography of one of the complexes [Ru(dhaptsc)(CO)(PPh3)2] (5). All the complexes are redox active and are monitored by cyclic voltammetric technique. Further, the catalytic efficiency of one of the ruthenium complexes (5) was determined in the case of oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine-N-oxide.
- Ulaganatha Raja,Gowri,Ramesh
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- Production of renewable 1,3-pentadiene over LaPO4 via dehydration of 2,3-pentanediol derived from 2,3-pentanedione
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1,3-Pentadiene plays an extremely important role in the production of polymers and fine chemicals. Herein, the LaPO4 catalyst exhibits excellent catalytic performance for the dehydration production of 1,3-pentadiene with 2,3-pentanediol, a C5 diol platform compound that can be easily obtained by hydrogenation of bio-based 2,3-pentanedione. The relationships of catalyst structure-acid/base properties-catalytic performance was established, and an acid-base synergy effect was disclosed for the on-purpose synthesis of 1,3-pentadiene. Thus, a balance between acid and base sites was required, and an optimized LaPO4 with acid/base ratio of 2.63 afforded a yield of 1,3-pentadiene as high as 61.5% at atmospheric pressure. Notably, the Br?nsted acid sites with weak or medium in LaPO4 catalyst can inhibit the occurrence of pinacol rearrangement, resulting in higher 1,3-pentadiene production. In addition, the investigation on reaction pathways demonstrated that the E2 mechanism was dominant in this dehydration reaction, accompanied by the assistance of E1 and E1cb.
- Bai, Chenxi,Cui, Long,Dai, Quanquan,Feng, Ruilin,Liu, Shijun,Qi, Yanlong
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- CeO2 Facet-Dependent Surface Reactive Intermediates and Activity during Ketonization of Propionic Acid
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CeO2 rods, octahedrons, and cubes exposing well-defined (110), (111), and (100) surfaces, respectively, were synthesized and investigated for the catalytic ketonization of propionic acid. The intrinsic ketonization rates at 350 °C on the rods, octahedrons, and cubes are 54.3, 40.4, and 25.1 mmol·m-2·h-1, respectively, indicating that the (110) facet is the most active surface for ketonization. The reaction was tracked by both in situ infrared and mass spectroscopies under transient conditions, and the results showed that monodentate propionate, a minority surface species, is responsible for the formation of 3-pentanone. In contrast, bidentate propionate, a dominant species on all three surfaces, appears to a spectator for ketonization. Moreover, the ketonization activity can be correlated with relative concentration of monodentate propionate. A density functional theory study showed that the relative concentration of monodentate propionate (or the adsorption energy difference between monodentate and bidentate configurations) at high coverages is strongly dependent on the surface geometry. The stability of monodentate propionate on the (110) surface exposing both the O and Ce sites in the outermost layer with the well-separated Ce sites exhibits little dependence on the propionate coverage. In contrast, strong steric hindrance due to the top layer O atom and the closely packed Ce atoms in (111) destabilizes monodentate propionate significantly at high coverages. This study demonstrates that the surface geometrical structure of CeO2 can determine the abundance of the active monodentate propionate, which, in turn, will determine the catalytic activity of CeO2 for ketonization.
- Guo, Yonghua,Qin, Yuyao,Liu, Huixian,Wang, Hua,Han, Jinyu,Zhu, Xinli,Ge, Qingfeng
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p. 2998 - 3012
(2022/03/03)
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- Synthesis of Chiral Amines via a Bi-Enzymatic Cascade Using an Ene-Reductase and Amine Dehydrogenase
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Access to chiral amines with more than one stereocentre remains challenging, although an increasing number of methods are emerging. Here we developed a proof-of-concept bi-enzymatic cascade, consisting of an ene reductase and amine dehydrogenase (AmDH), to afford chiral diastereomerically enriched amines in one pot. The asymmetric reduction of unsaturated ketones and aldehydes by ene reductases from the Old Yellow Enzyme family (OYE) was adapted to reaction conditions for the reductive amination by amine dehydrogenases. By studying the substrate profiles of both reported biocatalysts, thirteen unsaturated carbonyl substrates were assayed against the best duo OYE/AmDH. Low (5 %) to high (97 %) conversion rates were obtained with enantiomeric and diastereomeric excess of up to 99 %. We expect our established bi-enzymatic cascade to allow access to chiral amines with both high enantiomeric and diastereomeric excess from varying alkene substrates depending on the combination of enzymes.
- Fossey-Jouenne, Aurélie,Jongkind, Ewald P. J.,Mayol, Ombeline,Paul, Caroline E.,Vergne-Vaxelaire, Carine,Zaparucha, Anne
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- Palladium mediated one-pot synthesis of 3-aryl-cyclohexenones and 1,5-diketones from allyl alcohols and aryl ketones
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One-pot synthesis of Robinson annulated 3-aryl-cyclohexenones from allyl alcohols and ketones using palladium is reported. Long chain aliphatic or aryl substitutions at the C1 position of allyl alcohol result in the formation of 1,5-diketone products. This simple one-pot method avoids the use of highly electrophilic vinyl ketones.
- Samser, Shaikh,Biswal, Priyabrata,Meher, Sushanta Kumar,Venkatasubbaiah, Krishnan
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p. 1386 - 1394
(2021/02/27)
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- Merging N-Hydroxyphthalimide into Metal-Organic Frameworks for Highly Efficient and Environmentally Benign Aerobic Oxidation
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Two highly efficient metal-organic framework catalysts TJU-68-NHPI and TJU-68-NDHPI have been successfully synthesized through solvothermal reactions of which the frameworks are merged with N-hydroxyphthalimide (NHPI) units, resulting in the decoration of pore surfaces with highly active nitroxyl catalytic sites. When t-butyl nitrite (TBN) is used as co-catalyst, the as-synthesized MOFs are demonstrated to be highly efficient and recyclable catalysts for a novel three-phase heterogeneous oxidation of activated C?H bond of primary and secondary alcohols, and benzyl compounds under mild conditions. Based on the high efficiency and selectivity, an environmentally benign system with good sustainability, mild conditions, simple work-up procedure has been established for practical oxidation of a wide range of substrates.
- Wang, Man,Liang, Gan,Wang, Yunhao,Fan, Tao,Yuan, Baoling,Liu, Mingxian,Yin, Ying,Li, Liangchun
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supporting information
p. 9674 - 9685
(2021/06/09)
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- Chromium-Catalyzed Production of Diols From Olefins
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Processes for converting an olefin reactant into a diol compound are disclosed, and these processes include the steps of contacting the olefin reactant and a supported chromium catalyst comprising chromium in a hexavalent oxidation state to reduce at least a portion of the supported chromium catalyst to form a reduced chromium catalyst, and hydrolyzing the reduced chromium catalyst to form a reaction product comprising the diol compound. While being contacted, the olefin reactant and the supported chromium catalyst can be irradiated with a light beam at a wavelength in the UV-visible spectrum. Optionally, these processes can further comprise a step of calcining at least a portion of the reduced chromium catalyst to regenerate the supported chromium catalyst.
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Paragraph 0111
(2021/03/19)
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- Linkage engineering mediated carriers transfer and surface reaction over carbon nitride for enhanced photocatalytic activity
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Rational tailoring of the atomic structure of photocatalysts with multiple functions to enhance the carrier transfer efficiency and surface activation of carbon nitride (C3N4) is promising and a challenge. Here, we make the first report of a facile strategy to construct amphiphilic carbon and C-O-C chain linked terminal melem units in functional carbon nitride (COCN)viacopolymerizing formaldehyde with melem. By integrating the amphiphilic carrier bridge of carbon and C-O-C chains into the framework, the photogenerated carrier mobility and activated species (superoxide radicals, singlet oxygen) as well as surface interaction are significantly improved. Consequently, the optimal tailoring of C3N4attains superior photocatalytic activity for hydrogen production (34.9 μmol h?1) and selective oxidation of sulfide to sulfoxide using air (nearly 100% conversion and selectivity after 3 h of illumination), which is about 7 times higher than that of pristine C3N4. This study provides deep insight into and strategies for the atomic tailoring of carrier transfer and surface reaction over organic-based photocatalysts.
- Chen, Peng,Li, Gen,Liu, Fei,Wang, Qian,Wang, Qiuchen,Yang, Shilian,Yin, Shuang-Feng,Zhao, Tianxiang
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p. 21732 - 21740
(2021/10/14)
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- METHOD FOR PRODUCING CARBONATE DERIVATIVE
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The objective of the present invention is to provide a method for producing a polycarbonate safely and efficiently even without using a base. The method for producing a carbonate derivative according to the present invention is characterized in comprising the step of irradiating a high energy light to a composition comprising the halogenated methane and the hydroxy group-containing compound in the presence of oxygen, wherein a molar ratio of a total usage amount of the hydroxy group-containing compound to 1 mole of the halogenated methane is 0.05 or more.
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Paragraph 0122-0123
(2022/01/04)
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- Fast Addition of s-Block Organometallic Reagents to CO2-Derived Cyclic Carbonates at Room Temperature, Under Air, and in 2-Methyltetrahydrofuran
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Fast addition of highly polar organometallic reagents (RMgX/RLi) to cyclic carbonates (derived from CO2 as a sustainable C1 synthon) has been studied in 2-methyltetrahydrofuran as a green reaction medium or in the absence of external volatile organic solvents, at room temperature, and in the presence of air/moisture. These reaction conditions are generally forbidden with these highly reactive main-group organometallic compounds. The correct stoichiometry and nature of the polar organometallic alkylating or arylating reagent allows straightforward synthesis of: highly substituted tertiary alcohols, β-hydroxy esters, or symmetric ketones, working always under air and at room temperature. Finally, an unprecedented one-pot/two-step hybrid protocol is developed through combination of an Al-catalyzed cycloaddition of CO2 and propylene oxide with the concomitant fast addition of RLi reagents to the in situ and transiently formed cyclic carbonate, thus allowing indirect conversion of CO2 into the desired highly substituted tertiary alcohols without need for isolation or purification of any reaction intermediates.
- Elorriaga, David,de la Cruz-Martínez, Felipe,Rodríguez-álvarez, María Jesús,Lara-Sánchez, Agustín,Castro-Osma, José Antonio,García-álvarez, Joaquín
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p. 2084 - 2092
(2021/04/02)
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- Manganese-Mediated C-C Bond Formation: Alkoxycarbonylation of Organoboranes
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Alkoxycarbonylations are important and versatile reactions that result in the formation of a new C-C bond. Herein, we report on a new and halide-free alkoxycarbonylation reaction that does not require the application of an external carbon monoxide atmosphere. Instead, manganese carbonyl complexes and organo(alkoxy)borate salts react to form an ester product containing the target C-C bond. The required organo(alkoxy)borate salts are conveniently generated from the stoichiometric reaction of an organoborane and an alkoxide salt and can be telescoped without purification. The protocol leads to the formation of both aromatic and aliphatic esters and gives complete control over the ester's substitution (e.g., OMe, OtBu, OPh). A reaction mechanism was proposed on the basis of stoichiometric reactivity studies, spectroscopy, and DFT calculations. The new chemistry is particularly relevant for the field of Mn(I) catalysis and clearly points to a potential pathway toward irreversible catalyst deactivation.
- Van Putten, Robbert,Filonenko, Georgy A.,Krieger, Annika M.,Lutz, Martin,Pidko, Evgeny A.
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supporting information
p. 674 - 681
(2021/04/02)
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- An In-Situ Self-regeneration Catalyst for the Production of Renewable Penta-1,3-diene
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Catalyst deactivation is a problem of great concern for many heterogeneous reactions. Here, an urchin-like LaPO4 catalyst was easily developed for pentane-2,3-diol dehydration; it has an impressive ability to restore the activity in situ by itself during the reaction, accounting for its high stability. This facilitates the efficient production of renewable penta-1,3-diene from pentane-2,3-dione via a novel approach, where penta-2,3-diol was obtained as an intermediate in 95 % yield under mild conditions.
- Feng, Ruilin,Qi, Yanlong,Liu, Shijun,Cui, Long,Dai, Quanquan,Bai, Chenxi
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supporting information
p. 9495 - 9498
(2021/05/27)
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- Single-atom Ru catalyst for selective synthesis of 3-pentanone: Via ethylene hydroformylation
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A Ru single-atom (Ru SA) catalyst supported on activated carbon was adopted to synthesize 3-pentanone with 83.3% selectivity via heterogeneous ethylene hydroformylation, while 52.1% ethane selectivity was obtained for Ru nanoparticles (Ru NPs). The atomically dispersed Ru species with oxidation state (Ruδ+) and Ru-C4O coordination structure were identified as the active sites for efficient C-C coupling to generate 3-pentanone, while metallic Ru nanoparticles exhibited high activity for ethylene hydrogenation to ethane. Density functional theory (DFT) calculation revealed that the energy barrier of the direct coupling of C2H5CO? with C2H5? to form 3-pentanone on Ru SA was much lower than that on Ru NPs. As a result, the formation of 3-pentanone over Ru SA was more favourable than propanal, which was admittedly generated via coupling of C2H5CO? and H?. This strategy may provide a potential green route for the one-pot synthesis of 3-pentanone with high atomic economy.
- Dang, Yaru,Jiang, Zheng,Li, Shenggang,Li, Xiao,Lin, Tiejun,Mei, Bingbao,Qin, Tingting,Sun, Yuhan,Tang, Zhiyong,Wu, Bo,Zhong, Liangshu
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supporting information
p. 9038 - 9047
(2021/11/30)
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- Long-Range Self-Assembly of an Electron-Deficient Hexaazatrinaphthylene with Out-of-Plane Substituents
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The unprecedented time-dependent long-range supramol-ecular assembly of electron-deficient hexaazatrinaphthylene (HATN) core based on peripheral crowding with three out-of-plane cyclic ketals is reported. The single-crystal X-ray structure of the diethyl derivative provided detailed information as to how four molecules in a repeating unit were packed in order to avoid steric crowding of the out-of-plane cyclic ketal side chain, providing locking and fastening for stabilizing the self-assembled structure. The polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) did not instantaneously show any phase transition upon the cooling process. To our surprise, POM images showed a nucleation of spherulite up to 100 μm after 24 hour later. X-ray diffraction data further confirmed that these soft crystal formed a hexagonal-like crystal. The long-range self-assembly of the new material showed a slight red shift in the UV-vis absorption spectra and further substantiated by computational method.
- Chen, Yi-Ru,Zhang, Yong-Yun,Yeh, Ming-Che,Luo, Ying-Ting,Ong, Chi Wi
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p. 613 - 618
(2019/12/24)
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- Metal-Organic Framework Based on Heptanuclear Cu-O Clusters and Its Application as a Recyclable Photocatalyst for Stepwise Selective Catalysis
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Visible-light driven photoreactions using metal-organic frameworks (MOFs) as catalysts are promising with regard to their environmental friendly features such as the use of renewable and sustainable energy of visible light and potential catalyst recyclability. To develop potential heterogeneous photocatalysts, a family of three copper(II) coordination polymers bearing different Cu-O assemblies have been synthesized with the ligand 4,4-disulfo-[1,1-biphenyl]-2,2-dicarboxylate acid (H4DSDC), namely, {[Cu7(DSDC)2(OH)6(H2O)10]·xH2O}n (1), {[Cu4(DSDC)(4,4-bpy)2(OH)4]·2H2O}n (2), and {Cu2(DSDC)(phen)2(H2O)2}n (3) (4,4-bpy = 4,4-bipyridine and phen = 1,10-phenanthroline). Complex 1 represents a metal-organic framework featuring a NbO type topology constructed from the infinite linkage of heptanuclear [Cu7(μ3-OH)6(H2O)10]8+ clusters by deprotonated DSDC4- ligands, comprising one-dimensional hexagonal channels of a diameter around 11 ? that are filled with water molecules. The infinite waving {[Cu2(OH)2]2+}n ladderlike chains in complex 2 are bridged by DSDC4- and 4,4-bpy ligands into a three-dimensional framework. A two-dimensional layered structure is formed in complex 3 due to the existence of terminal phenanthroline ligands. All of the coordination polymers 1-3 are able to catalyze the visible-light driven oxidation of alcohols at mild conditions using hydrogen peroxide as an oxidant, in which complex 1 demonstrates satisfactory efficiency. Significantly for this photoreaction catalyzed by 1, the extent of oxidation over aryl primary alcohols is fully controllable with time-resolved product selectivity, giving either corresponding aldehydes or carboxylate acids in good yields. It is also remarkable that the photocatalyst could be recovered almost quantitatively on completion of the catalytic cycle without any structure change, and could be recycled for catalytic use for at least five cycles with constant efficiency. This photocatalyst with time-resolved selectivity for different products may provide new insight into the design and development of novel catalytic systems.
- Zhou, Jie,Huang-Fu, Xu,Huang, Yang-Ying,Cao, Chu-Ning,Han, Jie,Zhao, Xiao-Li,Chen, Xu-Dong
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p. 254 - 263
(2019/12/04)
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- Base-free oxidation of alcohols enabled by nickel(ii)-catalyzed transfer dehydrogenation
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An efficient nickel(ii)-catalyzed transfer dehydrogenation oxidation of alcohols is reported that relies on cyclohexanone as the formal oxidant and does not require the use of an external base. The synthetic utility of this protocol is demonstratedviathe facile oxidation of structurally complicated natural products.
- Ye, Danfeng,Liu, Zhiyuan,Sessler, Jonathan L.,Lei, Chuanhu
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supporting information
p. 11811 - 11814
(2020/10/13)
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- Superelectrophilic Fe(III)-Ion Pairs as Stronger Lewis Acid Catalysts for (E)-Selective Intermolecular Carbonyl-Olefin Metathesis
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An intermolecular carbonyl-olefin metathesis reaction is described that relies on superelectrophilic Fe(III)-based ion pairs as stronger Lewis acid catalysts. This new catalytic system enables selective access to (E)-olefins as carbonyl-olefin metathesis products. Mechanistic investigations suggest the regioselective formation and stereospecific fragmentation of intermediate oxetanes to be the origin of this selectivity. The optimized conditions are general for a variety of aryl aldehydes and trisubstituted olefins and are demonstrated for 28 examples in up to 64% overall yield.
- Albright, Haley,Schindler, Corinna S.,Vonesh, Hannah L.
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supporting information
p. 3155 - 3160
(2020/04/21)
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- Catalytic Oxidative Deamination by Water with H2Liberation
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Selective oxidative deamination has long been considered to be an important but challenging transformation, although it is a common critical process in the metabolism of bioactive amino compounds. Most of the synthetic methods developed so far rely on the use of stoichiometric amounts of strong and toxic oxidants. Here we present a green and efficient method for oxidative deamination, using water as the oxidant, catalyzed by a ruthenium pincer complex. This unprecedented reaction protocol liberates hydrogen gas and avoids the use of sacrificial oxidants. A wide variety of primary amines are selectively transformed to carboxylates or ketones in good to high yields. It is noteworthy that mechanistic experiments and DFT calculations indicate that in addition to serving as the oxidant, water also plays an important role in assisting the hydrogen liberation steps involved in amine dehydrogenation.
- Tang, Shan,Rauch, Michael,Montag, Michael,Diskin-Posner, Yael,Ben-David, Yehoshoa,Milstein, David
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supporting information
p. 20875 - 20882
(2020/12/23)
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- Ethylene Hydroformylation in the Presence of Rhodium Catalysts in Hydrocarbon-Rich Media: The Stage of Combined Conversion of Refinery Gases to Oxygenates
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Abstract: The feature of hydroformylation of model gas mixtures with different ethylene, hydrogen, and methane concentrations in the presence of rhodium catalysts have been studied. The effect of the initial pressure in the reactor and the reaction temperature on the reaction rate and selectivity has been determined. It has been shown that ethylene hydroformylation occurs with a high propanal selectivity (up to 99%), with the turnover frequency of the reaction reaching 9500 h–1. It has been proposed that various phosphine ligands should be used to implement alternative methods of separating the catalyst system from the reaction products.
- Gorbunov,Nenasheva,Matsukevich,Terenina,Putilin,Kardasheva, Yu. S.,Maksimov,Karakhanov
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p. 1009 - 1016
(2019/10/19)
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- Sustainable hydrocarbon production via simultaneous condensation-hydrodeoxygenation of propionic acid with furfural over red mud-supported noble metal catalysts
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A new catalytic system for single-step alkane synthesis from furans and carboxylic acids was investigated using noble metals-supported red mud (RM) catalysts. Maximum alkane selectivities were 100%, 87%, and 56% over Pt/RM, Pd/RM, and Ru/RM respectively. Potassium doping prolonged the catalyst life by suppressing methanation reaction, decreased coking, and enhancing the stability of noble metals towards oxidation. Five functionalities were accomplished on the modified catalysts: partial reduction of propionic acid on noble metals; moderating coking reactions on K, suppressing methanation on K, ketonization of acid on RM, and condensation-hydrodeoxygenation reaction on RM. Magnetite played significant role in catalyzing ketonization reaction.
- Castille, Antonie,Bessette, Claudie,Thomas, Francois,Etemad, Mania
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- Additive-Free Isomerization of Allylic Alcohols to Ketones with a Cobalt PNP Pincer Catalyst
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Catalytic isomerization of allylic alcohols in ethanol as a green solvent was achieved by using air and moisture stable cobalt (II) complexes in the absence of any additives. Under mild conditions, the cobalt PNP pincer complex substituted with phenyl groups on the phosphorus atoms appeared to be the most active. High rates were obtained at 120 °C, even though the addition of one equivalent of base increases the speed of the reaction drastically. Although some evidence was obtained supporting a dehydrogenation–hydrogenation mechanism, it was proven that this is not the major mechanism. Instead, the cobalt hydride complex formed by dehydrogenation of ethanol is capable of double-bond isomerization through alkene insertion–elimination.
- Spiegelberg, Brian,Dell'Acqua, Andrea,Xia, Tian,Spannenberg, Anke,Tin, Sergey,Hinze, Sandra,de Vries, Johannes G.
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supporting information
p. 7820 - 7825
(2019/05/22)
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- Efficient acceptorless photo-dehydrogenation of alcohols and: N -heterocycles with binuclear platinum(ii) diphosphite complexes
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Although photoredox catalysis employing Ru(ii) and Ir(iii) complexes as photocatalysts has emerged as a versatile tool for oxidative C-H functionalization under mild conditions, the need for additional reagents acting as electron donor/scavenger for completing the catalytic cycle undermines the practicability of this approach. Herein we demonstrate that photo-induced oxidative C-H functionalization can be catalysed with high product yields under oxygen-free and acceptorless conditions via inner-sphere atom abstraction by binuclear platinum(ii) diphosphite complexes. Both alcohols (51 examples), particularly the aliphatic ones, and saturated N-heterocycles (24 examples) can be efficiently dehydrogenated under light irradiation at room temperature. Regeneration of the photocatalyst by means of reductive elimination of dihydrogen from the in situ formed platinum(iii)-hydride species represents an alternative paradigm to the current approach in photoredox catalysis.
- Zhong, Jian-Ji,To, Wai-Pong,Liu, Yungen,Lu, Wei,Che, Chi-Ming
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p. 4883 - 4889
(2019/05/16)
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- Synergistic hydrogen atom transfer with the active role of solvent: Preferred one-step aerobic oxidation of cyclohexane to adipic acid by N-hydroxyphthalimide
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In this work, we developed an one-step aerobic oxidation of cyclohexane to prepare adipic acid, catalyzed by N-hydroxyphthalimide (NHPI) under promoter- and metal-free conditions. A significant beneficial solvent effect for synergistic reaction is observed with varying polarity and hydrogen-bonding strength: detailed study reveals that the solvent environments manipulate catalytic activity and adipic acid selectivity. Cyclic voltammetry measurements and UV–visible spectra of the NHPI catalyst are examined in various solvent environments to understand the active role of solvent in influencing the catalytic-site structure (>NOH) of the molecule. Analysis of the UV–visible spectra reveals that these differences can be rationalized by considering hydrogen-bonding with solvent molecules, which modifies the catalytic-site structure. This observation is in agreement with cyclic voltammetry results: the different reversibility of the catalytic-site (>NOH/>NO[rad]) wave shows that the catalytic activity of NHPI is related to the formation of hydrogen bonds with the active participation of solvents. Computational studies presented herein have furnished mechanistic insights into the effect of solvent environments. Specifically, we present the structures, dissociation energies, and reaction barriers from DFT studies of the reactants and reaction intermediates involved in the two types of H-abstraction on >NO[rad] catalytic-sites for the rate-determining step. The results of modeling the solvent effects using the PCM continuum solvent method predict that the resulting reaction barrier of the rate-controlling H-abstraction for cyclohexane and cyclohexanone is modified significantly: the transition state barrier of H-abstraction for cyclohexane decreases from 22.36 (in benzene) to 20.78 kcal?mol?1 (in acetonitrile); the α-H-abstraction barrier for cyclohexanone decreases from 21.45 to 20.53 kcal?mol?1. The active participation of solvent molecule results in a strong interaction between pre-reaction complex (PINO???H???C NO[rad] catalytic-sites at the transition state. The lower calculated barriers of H-abstraction for cyclohexanone oxidation approximate more closely the experimental results of the higher adipic acid selectivity. Our work provides a dimension of sustainable chemistry for the metal-free preparation of adipic acid: a conversion of 27% with 79% adipic acid selectivity is achieved over use of NHPI catalysts in CH3CN solvent.
- Liang, Futong,Zhong, Wenzhou,Xiang, Liping,Mao, Liqiu,Xu, Qiong,Kirk, Steven Robert,Yin, Dulin
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p. 256 - 269
(2019/09/30)
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- Synthesis of 2 h-chromenes via hydrazine-catalyzed ring-closing carbonyl-olefin metathesis
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The catalytic ring-closing carbonyl-olefin metathesis (RCCOM) of O-Allyl salicylaldehydes to form 2H-chromenes is described. The method utilizes a [2.2.1]-bicyclic hydrazine catalyst and operates via a [3 + 2]/retro-[3 + 2] metathesis manifold. The nature of the allyl substitution pattern was found to be crucial, with sterically demanding groups such as adamantylidene or diethylidene offering optimal outcomes. A survey of substrate scope is shown along with a discussion of mechanism supported by DFT calculations. Steric pressure arising from syn-pentane minimization of the diethylidene moiety is proposed to facilitate cycloreversion.
- Jermaks, Janis,Lambert, Tristan H.,Macmillan, Samantha N.,Zhang, Yunfei
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p. 9259 - 9264
(2019/10/08)
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- Photolysis of Tp′Rh(CNneopentyl)(PhNCNneopentyl) in the presence of ketones and esters: Kinetic and thermodynamic selectivity for activation of different aliphatic C-H bonds
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The active fragment [Tp′Rh(CNneopentyl)], generated from the precursor Tp′Rh(CNneopentyl)(PhNCNneopentyl), underwent oxidative addition of substituted ketones and esters resulting in Tp′Rh(CNneopentyl)(R)(H) complexes (Tp′ = tris-(3,5-dimethylpyrazolyl)borate). These C-H activated complexes underwent reductive elimination at varying temperatures (24-70 °C) in C6D6 or C6D12. Using previously established kinetic techniques, the relative Rh-C bond strengths were calculated. Analysis of the relative Rh-C bond strengths vs. C-H bond strengths shows a linear correlation with slope RM-C/C-H = 1.22 (12). In general, α-substituents increase the relative Rh-C bond strengths compared to the C-H bond that is broken.
- Jones, William D.,Parsons, Astrid M.
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supporting information
p. 10945 - 10952
(2019/08/01)
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- Ce/MgAl mixed oxides derived from hydrotalcite LDH precursors as highly efficient catalysts for ketonization of carboxylic acid
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Ketonization of carboxylic acids provides an attractive way for upgrading biomass feedstocks into biofuels. Here, a series of Mg-Al hydrotalcite (HT) catalysts doped with different Ce contents were prepared and used for the ketonization of propionic acid. Mg3Al0.9Ce0.1 displayed the highest ketonization activity (90.6% conversion of propionic acid) under mild reaction conditions (350 °C). By applying SEM, TEM, H2-TPR, CO2/NH3-TPD, XPS, etc., the mechanism for the improvement of catalytic activity and stability was obtained. When the doping content of Ce is low, such as in Mg3Al0.9Ce0.1, cerium oxide is uniformly dispersed on the HT support. At the same time, the strong interaction between the CeO2 species and Mg-Al hydrotalcite led to the improvement of redox properties and modified acid-base sites, which is beneficial for the ketonization reaction. However, the structure of the HT support is destroyed by the agglomerated cerium oxide when a more doped Ce is employed, and the specific surface area and the surface Ce3+ ratio are remarkably lowered, thereby causing a significant decrease in the ketonization activity. By using the temperature programmed surface reaction (TPSR) technique, a deeper insight into the mechanism of reaction pathways over different catalysts is gained. The significant improvement in the reaction stability of the ketonization reaction over Mg3Al0.9Ce0.1 as compared to unmodified catalysts could be ascribed to the strengthening of the M-O bond of the catalyst after the introduction of Ce.
- Jiang, Binbo,Xi, Zhixiang,Lu, Feipeng,Huang, Zhengliang,Yang, Yao,Sun, Jingyuan,Liao, Zuwei,Wang, Jingdai,Yang, Yongrong
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p. 6335 - 6344
(2019/11/20)
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- Insights into the improvement effect of Fe doping into the CeO2 catalyst for vapor phase ketonization of carboxylic acids
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The conversion of carboxylic acid through ketonization process reduces O-atoms and increases C[sbnd]C bonds, which can provide attractive routes for upgrading biomass feedstocks into biofuels. The key factors influencing the surface ketonization activity over CeO2-based oxides catalysts remain matters of active discourse. Here, a series of Ce1-xFexO2-δ catalysts were investigated for vapor-phase ketonization of acetic and propionic acid. The catalysts were characterized in detail using various physico-chemical techniques both before and after reaction to gain understanding of the ketonization process. The turnover frequency (TOF) based on the basic sites changed with the Fe content. The Ce0.8Fe0.2O2-δ sample showed the prominent ketonization activity with the highest TOF value. On one hand, for samples with a lower Fe addition (x 2-like solid solution with numerous Ce-O-Fe species showed a dramatic increase in surface oxygen vacancies. These oxygen vacancies were beneficial to catalytic performance. Moreover, the superior redox properties with weaken M[sbnd]O bonds of Ce-O-Fe species thereby promote the ketonization activity. On the other hand, the higher Fe addition (x > 0.3) caused the damage of the Ce-O-Fe structure, thus reducing ketonization activity. Notably, the investigation of the reaction temperature regime of Ce0.8Fe0.2O2-δ sample directly proved the existence of surface redox cycle during the ketonization process.
- Lu, Feipeng,Jiang, BinBo,Wang, Jingdai,Huang, Zhengliang,Liao, Zuwei,Yang, Yongrong
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- Rational Design of a Metallocatalytic Cavitand for Regioselective Hydration of Specific Alkynes
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The synthesis of a functionalized supramolecular cavitand with inwardly oriented AuI and P=O moieties was explored, including its catalytic proclivity in the selective hydration of internal alkynes. The cavitand works as a supramolecular flask device: AuI coordinates to the triple bond, the P=O moiety connects with a H2O molecule, and the cavity favors folding of a single alkynyl side chain. Several tests of different substrate patterns indicated that the cavity was substrate specific, similar to enzymatic catalysis.
- Endo, Naoki,Inoue, Mami,Iwasawa, Tetsuo
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supporting information
p. 1136 - 1140
(2018/03/13)
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- Utilization of hexabromoacetone for protection of alcohols and aldehydes and deprotection of acetals, ketals, and oximes under UV irradiation
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Hexabromoacetone (HBA) was efficiently used for the protection of alcohols and aldehydes and deprotection of benzaldehyde dimethyl acetal, solketal, and other acetals and ketals. In only 10?min, the protection of glycerol yielded 90% of solketal and protection of benzaldehyde gave 95% of benzaldehyde dimethyl acetal. The deprotection of benzaldehyde dimethyl acetal under UV irradiation gave over 90% yield of benzaldehyde within 15?s using only 2.5?mol% of HBA. HBA was also successfully used for deoximation. Solvent was found to play an important role in the efficiency of HBA for these reactions.
- Chaiseeda, Kittichai,Chantharadet, Ladawan,Chavasiri, Warinthorn
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p. 1305 - 1323
(2017/10/30)
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- Acid-Promoter-Free Ethylene Methoxycarbonylation over Ru-Clusters/Ceria: The Catalysis of Interfacial Lewis Acid-Base Pair
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The interface of metal-oxide plays pivotal roles in catalytic reactions, but its catalytic function is still not clear. In this study, we report the high activity of nanostructured Ru/ceria (Ru-clusters/ceria) in the ethylene methoxycarbonylation (EMC) re
- An, Jinghua,Wang, Yehong,Lu, Jianmin,Zhang, Jian,Zhang, Zhixin,Xu, Shutao,Liu, Xiaoyan,Zhang, Tao,Gocyla, Martin,Heggen, Marc,Dunin-Borkowski, Rafal E.,Fornasiero, Paolo,Wang, Feng
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supporting information
p. 4172 - 4181
(2018/03/29)
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- A H2O2/HBr system-several directions but one choice: oxidation-bromination of secondary alcohols into mono- or dibromo ketones
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In this work we found that a H2O2-HBr(aq) system allows synthesis of α-monobromo ketones and α,α′-dibromo ketones from aliphatic and secondary benzylic alcohols with yields up to 91%. It is possible to selectively direct the process toward the formation of mono- or dibromo ketones by varying the amount of hydrogen peroxide and hydrobromic acid. The convenience of application, simple equipment, multifaceted reactivity, and compliance with green chemistry principles make the application of the H2O2-HBr(aq) system very attractive in laboratories and industry. The proposed oxidation-bromination process is selective in spite of known properties of ketones to be oxidized by the Baeyer-Villiger reaction or peroxidated with the formation of compounds with the O-O moiety in the presence of hydrogen peroxide and Bronsted acids.
- Nikishin, Gennady I.,Kapustina, Nadezhda I.,Sokova, Liubov L.,Bityukov, Oleg V.,Terent'ev, Alexander O.
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p. 28632 - 28636
(2018/08/31)
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- Method for preparing aldehydes or ketones through olefin oxidation
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The invention relates to a method for preparing aldehydes or ketones through catalytic oxidation of olefins by taking chiral tetradentate nitrogen organic compounds as ligands and taking metallic compounds as catalysts. According to the technical scheme, the method comprises the following steps: by taking four-tooth nitrogen organic compounds and metallic compounds as a catalytic system, and taking olefins as a substrate, reacting in the presence of an oxidizing agent, thereby obtaining the product aldehydes or ketones. The reaction temperature is 25-120 DEG C, the reaction time is 1-12 hours,the molar ratio of the chiral four-tooth nitrogen organic ligands to metal elements is 1:10 to 10:1, the molar ratio of the chiral four-tooth nitrogen organic ligands to the substrate olefins is 1:3000 to 1:100, and the molar ratio of the olefins to the oxidizing agent is 1:10 to 1:1. The method for preparing aldehydes or ketones through olefin oxidation provided by the invention is simple to operate, has high catalytic activity and selectivity and also has great industrialized application prospects.
- -
-
Paragraph 0030-0031
(2018/06/16)
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- Experimental and theoretical assessment of the mechanism and site requirements for ketonization of carboxylic acids on oxides
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Ketonization of carboxylic acids removes O-atoms and forms new CC bonds, thus providing routes from sustainable carbon feedstocks to fuels and chemicals. The elementary steps involved and their kinetic relevance, as well as the number and nature of the active sites on active TiO2 and ZrO2 catalysts, remain matters of active discourse. Here, site titrations demonstrate the requirement for coordinatively-unsaturated M-O-M sites (M?=?Ti, Zr) with specific geometry and intermediate acid-base strength. The measured site densities allow rigorous reactivity comparisons among catalysts based on turnover rates and activation free energies, as well as the benchmarking of mechanistic proposals against theoretical assessments. Kinetic, isotopic, spectroscopic, and theoretical methods show that C2C4 acids react on anatase TiO2 via kinetically-relevant CC coupling between 1-hydroxy enolate species and coadsorbed acids bound at vicinal acid-base pairs saturated with active monodentate carboxylates. Smaller TiTi distances on rutile TiO2 lead to the prevalence of unreactive bidentate carboxylates and lead to its much lower ketonization reactivity than anatase. The prevalent dense monolayers of chemisorbed acid reactants reflect their strong binding at acid-base pairs and their stabilization by H-bonding interactions with surface OH groups derived from the dissociation of the carboxylic acids or the formation of 1-hydroxy enolates; these interactions also stabilize CC coupling transition states preferentially over their carboxylate precursors; high coverages favor sequential dehydration routes of the α-hydroxy-γ-carboxy-alkoxide CC coupling products over previously unrecognized concerted six-membered-ring transition states. Infrared spectra show that ubiquitous deactivation, which has precluded broader deployment of ketonization in practice and unequivocal mechanistic inquiries, reflects the gradual formation of inactive bidentate carboxylates. Their dehydration to ketene-like gaseous species is faster on anatase TiO2 than on ZrO2 and allows the effective scavenging of bidentate carboxylates via ketene hydrogenation to alkanals/alkanols on a Cu function present within diffusion distances. These strategies make anatase TiO2, a more effective catalyst than ZrO2, in spite of its slightly lower initial turnover rates. This study provides details about the mechanism of ketonization of C2C4 carboxylic acids on TiO2 and a rigorous analysis of the sites required and of active and inactive bound species on TiO2 and ZrO2. The preference for specific distances and for intermediate acid-base strength in M-O-M species is consistent with the structure and energy of the proposed transition states and intermediates; their relative stabilities illustrate how densely-covered surfaces, prevalent during ketonization catalysis, represent an essential requirement for the achievement of practical turnover rates.
- Wang, Shuai,Iglesia, Enrique
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p. 183 - 206
(2016/12/16)
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- Conversion of propionic acid and 3-pentanone to hydrocarbons on ZSM-5 catalysts: Reaction pathway and active site
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Conversion of propionic acid to gasoline-range molecules was investigated at 350?°C on a series of ZSM-5 catalysts with varying density of Br?nsted acid sites (BAS), achieved by ion exchange of proton with Na+. Ketonization of propionic acid to 3-pentanone is the primary reaction, with the sequential aldol condensation to dipentanone alcohol being the secondary. The major reaction pathway for forming the aromatics involves dehydration, cyclization, dehydration and hydride transfer from dipentanone alcohol, leading to the formation of C10 aromatics before being dealkylated to lighter aromatics. Temperature programmed desorption of propionic acid indicates that the reaction initiates with acylium cation formation on BAS through dehydration. Comparing the turnover frequencies of ketonization and aldol condensation on ZSM-5 with varying density of BAS indicates that BAS is the active site for both reactions. The propionic acid feed deactivates the catalyst faster than the 3-pentantone feed due to a stronger adsorption of propionic acid on the acid sites of ZSM-5.
- Wang, Xuefen,Ding, Shuang,Wang, Hua,Liu, Xiao,Han, Jinyu,Ge, Qingfeng,Zhu, Xinli
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- Mixed-valence μ3-oxo-centered triruthenium cluster [Ru3(II,III,III)(μ3-O)(μ-CH3CO2)6(H2O)3]·2H2O: Synthesis, structural characterization, valence-state delocalization and catalytic behavior
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The oxo-centered, trinuclear, mixed valence [Ru3(II,III,III)O(CH3CO2)6(H2O)3]·2H2O (2) acetate complex has been prepared with high yield through reduction of [Ru3(III,III,III)O(CH3CO2)6(CH3OH)3]·CH3CO2precursor compound in presence of muccic acid under hydrothermal conditions. The crystalline trinuclear oxo-cluster has been obtained as crystalline powder and characterized by single-crystal and powder X-ray diffraction, elemental analysis, SEM, TGA, IR spectroscopy. Complex 2 composes of μ3-oxocentered trinuclear ruthenium array and exhibits the oxidation state delocalization between three Ru atoms at 293 K. Accurate single-crystal analysis along with valence bond calculations reveal trapped-valence state delocalization at room temperature, whereas three-site relaxation occurs at 100 K leading to Ru(II) and Ru2(III) formal states. Moreover, the mixed valence of RuIIRu2IIIunit in compound 2 has been confirmed by XANES spectroscopy. The catalytic behavior of oxo-centered triruthenium complex 2 has been examined in hydration of nitriles and isomerization of allylic alcohols reactions both realized in aqueous media.
- Dikhtiarenko, Alla,Khainakov, Sergei,García, José R.,Gimeno, José
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p. 107 - 116
(2016/11/19)
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- Catalytic redox isomerization of allylic alcohols with rhodium and iridium complexes with ferrocene phosphine-thioether ligands
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Complexes [M(P,SR)(diene)X] where (P,SR) = CpFe[1,2-C5H3(PPh2)(CH2SR)] (M = Ir, R = tBu or Bn diene = cod, X = Cl; M = Rh, diene = cod or nbd; X = BF4 or Cl) were used as precatalysts for the redox isomerization of various allylic alcohols (7a–e) to the corresponding saturated ketones (8a–e) and or hydrogenation to the saturated alcohol (9a–e). In optimization studies using 1-phenyl-2-propen-1-ol (7a) in THF and in iPrOH/MeONa, the only observed product was the saturated alcohol 1-phenyl-1-propanol (9a) when working under a 30 bar H2 pressure, but activation for only 1 min under H2 pressure and then continuation under 1 bar of H2 or Ar led to increasing amounts of the allylic isomerization product propiophenone (8a). Continued reaction under H2 converted (8a) into (9a). The Rh precatalysts were more active than the Ir analogues. For the rhodium precatalysts (3) and (4), the redox isomerization reaction could be carried out after precatalyst activation in iPrOH/MeONa under Ar at 82 °C (without H2) with complete conversion in 1 h (1% catalyst loading). However, longer reaction times resulted in slow transfer hydrogenation of (8a) leading to (9a) with low enantiomeric excess. Extension of the H2-free activation of the Rh precatalysts in iPrOH to other allylic alcohol substrates (7b–d) yielded the corresponding ketones with good to excellent yields and excellent chemoselectivities under appropriate conditions.
- Titova, Ekaterina M.,Rahaman, S.M. Wahidur,Shubina, Elena S.,Poli, Rinaldo,Belkova, Natalia V.,Manoury, Eric
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p. 376 - 380
(2016/12/16)
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- Facile synthesis of [Ru(η2-O2CO)(pta)(η6-p-cymene)], an outstandingly active Ru(II) half-sandwich complex for redox isomerization of allylic alcohols
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The water-soluble [RuCl2(pta)(η6-p-cymene)] (pta = 1,3,5-triaza-7-phosphaadamantane) was applied as catalyst in the transposition of allylic alcohols, such as oct-1-en-3-ol in aqueous media. The isomerisation of oct-1-en-3-ol to octan-3-one took place only at pH > 10 buffer solutions or in the presence of alkali metal carbonates. The aqueous solution of “in situ” catalyst ([RuCl2(pta)(η6-p-cymene)] + 2 eq Na2CO3) could be reused in the biphasic isomerization of oct-1-en-3-ol for at least five times without a significant loss of the catalytic activity. It was demonstrated that carbonate is not only a base in this reaction but leads to formation of a highly active catalyst, [Ru(η2-O2CO)(pta)(η6-p-cymene)]. This compound was isolated as crystalline solid and characterized in detail (including X-ray diffraction).
- Bolyog-Nagy, Evelin,Udvardy, Antal,Barczáné-Bertók, ágnes,Joó, Ferenc,Kathó, ágnes
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p. 514 - 520
(2016/12/02)
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- Water and catalytic isomerization of linear allylic alcohols by [RuCp(H2O-κO)(PTA)2]+ (PTA = 1,3,5-triaza-7-phosphaadamantane)
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A new water soluble complex [RuCp(H2O-κO)(PTA)2]+ (1) (PTA = 1,3,5-triaza-7-phosphaadamantane) has been synthesized and fully characterized by NMR and IR. The crystal structure of 1(CF3SO3)·3.5H2O was characterized by single crystal X-ray determination. The catalytic activity of this complex was evaluated for the isomerisation of linear allylic alcohols from 3-buten-2-ol to 1-octen-3-ol into the correspondent ketones under both an inert atmosphere and in air, using as solvents: water, the substrate, mixtures of water/substrate, MeOH and mixtures of MeOH/water. An isomerization experiment on a mixture of all the studied allylic alcohols was also carried out.
- Scalambra, Franco,Serrano-Ruiz, Manuel,Romerosa, Antonio
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supporting information
p. 5864 - 5871
(2017/07/10)
-
- Mononuclear Ruthenium and Osmium Complexes with a Bicyclic Guanidinate Ligand: Synthesis and Catalytic Behavior in Olefin Isomerization Processes
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The preparation of the first mononuclear RuII, RuIV, and OsII complexes containing the anion of the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (Hhpp) as a chelating ligand, namely [RuX{κ2-(N,N′)-hpp}(η6-arene)] [arene = p-cymene, X = Cl (2a), Br (2b), I (2c); arene = C6Me6, X = Cl (7)], [RuCl{κ2-(N,N′)-hpp}(η3:η3-C10H16)] (9; C10H16 = 2,7-dimethylocta-2,6-diene-1,8-diyl), and [OsCl{κ2-(N,N′)-hpp}(η6-p-cymene)] (11), is described. Compounds 2a–c, 7, 9, and 11 have been fully characterized by elemental analysis, HRMS, IR and NMR spectroscopy. In addition, the structure of 2a has been unequivocally confirmed by single-crystal X-ray diffraction methods. The catalytic behavior of these metal guanidinate complexes in the base-free redox isomerization of allylic alcohols is explored, with the ruthenium(IV) derivative 9 showing the best performance (TOF up to 5940 h–1). All of the synthesized complexes have also proven to be active in the isomerization of the allylbenzene estragole into the industrially relevant 1-propenylbenzene anethole, with a trans selectivity of up to 95 %.
- Gámez-Rivera, Sebastián A.,Francos, Javier,Borge, Javier,Cadierno, Victorio
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p. 4138 - 4146
(2017/09/28)
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- Synthesis and characterization of some new half-sandwich ruthenium(II) complexes with bidentate N,N′-ligands and their application in alcohol oxidation
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A series of eight new (η6-arene)ruthenium(II) complexes were prepared by the reaction of pyridyl-imine ligands and the ruthenium(II) precursors of the general formula [(η6-arene)Ru(μ-Cl)Cl]2, where arene = p-cymene (1) and C6H6(2), to form the complexes [(η6-arene)RuCl(C5H4N-2-CH[dbnd]N-Ar)]PF6(where Ar = 2,4,6-trimethylphenyl (a), 2,4-dimethylphenyl (b), 2-methoxyphenyl (c), 2,6-diisopropylphenyl (d)).These complexes were characterized using 1H NMR, 13C NMR, 31P NMR, IR, UV–Vis, HRMS, and TGA. The molecular structures for the complexes 1a,1d, 2a and 2d were determined by single crystal crystallography, revealing a pseudo-octahedral piano stool geometry. In this arrangement, the ruthenium metal is coordinated to the arene ligand at the apex of the stool with one chloride and the N,N-ligand as the base. These complexes were applied as catalysts in the oxidation of cyclic, aliphatic and aromatic alcohols with NaIO4as oxidant and the complexes showed good conversions and yields to the corresponding carbonyl products.
- Gichumbi, Joel M.,Friedrich, Holger B.,Omondi, Bernard
-
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- NaBrO3/bmim[HSO4]: a versatile system for the selective oxidation of 1,2-diols, α-hydroxyketones, and alcohols
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Abstract: Sodium bromate with bmim[HSO4] has been found to be an excellent oxidizing agent in aqueous medium. NaBrO3:bmim[HSO4] oxidized 1,2-diols, α-hydroxyketones, and alcohols to the corresponding carbonyl compounds in excellent yields. This method offers advantages such as low cost reagents, aqueous reaction conditions, moderate temperatures and short reaction times and hence environmentally benign reaction. Moreover, the ionic liquid bmim[HSO4] could be recycled for at least three times without loss of significant activity. Graphical abstract: [Figure not available: see fulltext.]
- Khurana, Jitender M.,Lumb, Anshika,Chaudhary, Ankita
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p. 381 - 386
(2017/02/10)
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- Homogeneous oxidation of alcohols in water catalyzed with Cu(II)-triphenyl acetate/bipyridyl complex
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A water-soluble mononuclear copper(II) complex, [Cu(OOCC(C6H5)3)(C10H8N2)(H2O)](ClO4)(CH3OH) (triphenylacetic acid?=?HOOCC(C6H5)3, 2-2′-bipyridyl (bipy)?=?C10H8N2) was synthesized and used as a catalyst precursor in the oxidation of primary (cinnamyl alcohol, benzyl alcohol, cyclohexanol, and 1-heptanol) and secondary alcohols (1-phenylethanol, 3-pentanol, and 2-octanol) to corresponding aldehydes, ketones, and acids. The complex exhibited high catalytic activity toward benzyl alcohol to benzaldehyde as one product (97% conversion in 6?h) and cinnamyl alcohol to benzaldehyde (91.5%) and cinnamaldehyde (6.6%), in 6?h reaction time with less catalyst loading (1?mol%) at a moderate temperature (70?°C). Water was used as a solvent and H2O2 as an oxidant for alcohol oxidation. Thus, the Cu(II)/H2O/H2O2 catalytic system could serve as an environmentally benign “green chemistry” alternative to oxidation methods in traditional organic solvents.
- ünver, Hakan,Kani, Ibrahim
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p. 257 - 262
(2017/07/12)
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- Tetrahydroxydiboron-Mediated Palladium-Catalyzed Transfer Hydrogenation and Deuteriation of Alkenes and Alkynes Using Water as the Stoichiometric H or D Atom Donor
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There are few examples of catalytic transfer hydrogenations of simple alkenes and alkynes that use water as a stoichiometric H or D atom donor. We have found that diboron reagents efficiently mediate the transfer of H or D atoms from water directly onto unsaturated C-C bonds using a palladium catalyst. This reaction is conducted on a broad variety of alkenes and alkynes at ambient temperature, and boric acid is the sole byproduct. Mechanistic experiments suggest that this reaction is made possible by a hydrogen atom transfer from water that generates a Pd-hydride intermediate. Importantly, complete deuterium incorporation from stoichiometric D2O has also been achieved.
- Cummings, Steven P.,Le, Thanh-Ngoc,Fernandez, Gilberto E.,Quiambao, Lorenzo G.,Stokes, Benjamin J.
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supporting information
p. 6107 - 6110
(2016/06/09)
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- Selective Oxidation of Aliphatic Alcohols using Molecular Oxygen at Ambient Temperature: Mixed-Valence Vanadium Oxide Photocatalysts
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Here we report a class of photocatalysts: mixed-valence vanadium oxide particles grafted onto a variety of oxide supports. In these catalysts V6O13 species with mixed oxidation states (V4+ or V5+) are believed to be catalytically active sites. These catalysts successfully enable alcohol oxidation to selectively produce aldehydes and ketones using O2 as the oxidant. The catalytic process is driven by visible light irradiation at room temperature and, most importantly, progresses with negligible overoxidation. The catalysts can even selectively oxidize aliphatic alcohols, which are much more challenging to control in comparison to aromatic analogues. They can also be applied to the activation and oxidation of the otherwise stable C-H bonds of saturated aromatic hydrocarbons, such as toluene and xylene, under irradiation. Both experimental results and density functional theory (DFT) simulations suggest the formation of V6O13-alkoxide species as the initial step in the catalytic cycle. The V6O13-alkoxide then acts as the light harvester, being excited by light of wavelength shorter than 550 nm. Facile room-temperature C-H bond cleavage in the excited state V6O13-alkoxide in the presence of O2 leads to the carbonyl-containing products. These findings demonstrate an example of light-driven selective oxidation of diverse alcohols via in situ formation of photoresponsive V6O13-alkoxide species. This catalytic process is especially valuable for the synthesis of temperature-sensitive products and represents an alternative pathway to many conventional thermal oxidation reactions.
- Zavahir, Sifani,Xiao, Qi,Sarina, Sarina,Zhao, Jian,Bottle, Steven,Wellard, Mark,Jia, Jianfeng,Jing, Liqiang,Huang, Yiming,Blinco, James P.,Wu, Haishun,Zhu, Huai-Yong
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p. 3580 - 3588
(2016/07/06)
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- Calcium tungstate: A convenient recoverable catalyst for hydrogen peroxide oxidation
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Calcium tungstate was found to be an excellent catalyst for large scale "green" oxidations of organic substrates (amines, alkenes, alcohols, sulfides) with hydrogen peroxide. It displays the unusual dual characteristics of producing a soluble pertungstate species, allowing for homogeneous reaction conditions, but then precipitating, unchanged, at the end of the oxidation. These qualities allow for easy catalyst recovery and minimal waste stream generation for large scale application.
- Tressler, Caitlin M.,Stonehouse, Peter,Kyler, Keith S.
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p. 4875 - 4878
(2016/10/06)
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- Alcohol oxidation with H2O2 catalyzed by a cheap and promptly available imine based iron complex
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We previously reported that the iminopyridine iron(II) complex 1, easily and quantitatively obtainable in situ, can activate H2O2 to form a powerful oxidant, capable of aliphatic C-H bond hydroxylation. In the present study we expand the application of this catalyst to the oxidation of a series of alcohols to the corresponding carbonyl compounds. The oxidation of aliphatic alcohols proceeds smoothly, while that of benzylic alcohols is shown to be challenging. Some collected pieces of evidence suggest a preference of the oxidizing species for the aromatic ring instead for the alcoholic moiety. The decrease of the electron density in the aromatic ring shifts the oxidation from the aromatic towards the alcoholic moiety. Quite surprisingly, preferential oxidation of cyclohexanol versus benzylic alcohol was achieved, showing unprecedented selectivity.
- Olivo, Giorgio,Giosia, Simone,Barbieri, Alessia,Lanzalunga, Osvaldo,Di Stefano, Stefano
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p. 10630 - 10635
(2016/11/21)
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- Deoxygenation of carbonyl compounds using an alcohol as an efficient reducing agent catalyzed by oxo-rhenium complexes
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This work describes the first methodology for the deoxygenation of carbonyl compounds using an alcohol as a green solvent/reducing agent catalyzed by oxo-rhenium complexes. The system 3-pentanol/ReOCl3(SMe2)(OPPh3) was successfully employed in the deoxygenation of several aryl ketones to the corresponding alkenes and also in the deoxygenation of aryl aldehydes to alkanes with moderate to excellent yields. The catalyst ReOCl3(SMe2)(OPPh3) can also be used in several catalytic cycles with good activity.
- Bernardo, Joana R.,Fernandes, Ana C.
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supporting information
p. 2675 - 2681
(2016/05/24)
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- Photooxygenation of alkanes by dioxygen with: P -benzoquinone derivatives with high quantum yields
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Alkanes were oxygenated by dioxygen with p-benzoquinone derivatives such as p-xyloquinone in alkanes which are used as solvents to yield the corresponding alkyl hydroperoxides, alcohols and ketones under visible light irradiation with high quantum yields (Φ = 1000, 1600%). The photooxygenation is started by hydrogen atom abstraction from alkanes by the triplet excited states of p-benzoquinone derivatives as revealed by laser-induced transient absorption spectral measurements.
- Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
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p. 731 - 734
(2016/07/06)
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- Solvent-Free Photooxidation of Alkanes by Dioxygen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone via Photoinduced Electron Transfer
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Photooxidation of alkanes by dioxygen occurred under visible light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) which acts as a super photooxidant. Solvent-free hydroxylation of cyclohexane and alkanes is initiated by electron transfer from alkanes to the singlet and triplet excited states of DDQ to afford the corresponding radical cations and DDQ??, as revealed by femtosecond laser-induced transient absorption measurements. Alkane radical cations readily deprotonate to produce alkyl radicals, which react with dioxygen to afford alkylperoxyl radicals. Alkylperoxyl radicals abstract hydrogen atoms from alkanes to yield alkyl hydroperoxides, accompanied by regeneration of alkyl radicals to constitute the radical chain reactions, so called autoxidation. The radical chain is terminated in the bimolecular reactions of alkylperoxyl radicals to yield the corresponding alcohols and ketones. DDQ??, produced by the photoinduced electron transfer from alkanes to the excited state of DDQ, disproportionates with protons to yield DDQH2.
- Ohkubo, Kei,Hirose, Kensaku,Fukuzumi, Shunichi
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supporting information
p. 2255 - 2259
(2016/08/30)
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- Deoxygenation of propionic acid in gas phase over cobalt molybdenum catalyst
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The gas-phase deoxygenation of propionic acid was investigated in the presence of Co-Mo catalysts in N2 or H2 flow at 200-400°C. In the presence of N2, the main product was 3-pentanone with other deoxygenates and some ligh
- Bayahia, Hossein
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p. 2745 - 2748
(2016/10/18)
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- Binuclear ruthenium(III) bis(thiosemicarbazone) complexes: Synthesis, spectral, electrochemical studies and catalytic oxidation of alcohol
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(Chemical Equation Presented).A new series of binuclear ruthenium(III) thiosemicarbazone complexes of general formula [(EPh3)2 (X)2Ru-L-Ru(X)2(EPh3)2] (where E = P or As; X = Cl or Br; L = NS chelating bis(thiosemicarbazone ligands) has been synthesized and characterized by analytical and spectral (FT-IR, UV-Vis and EPR). IR spectra show that the thiosemicarbazones behave as monoanionic bidentate ligands coordinating through the azomethine nitrogen and thiolate sulphur. The electronic spectra of the complexes indicate that the presence of d-d and intense LMCT transitions in the visible region. The complexes are paramagnetic (low spin d5) in nature and all the complexes show rhombic distortion around the ruthenium ion with three different 'g' values (gx ≠ gy ≠ gz) at 77 K. All the complexes are redox active and exhibit an irreversible metal centered redox processes (RuIII-RuIII/RuIV-RuIV; RuIII-RuIII/RuII-RuII) within the potential range of 0.38- 0.86 V and -0.39 to -0.66 V respectively, versus Ag/AgCl. Further, the catalytic efficiency of one of the complexes [Ru2Cl2(AsPh3)4(L1)] (4) has been investigated in the case of oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine- N-oxide(NMO) as co-oxidant. The formation of high valent RuV@O species is proposed as catalytic intermediate for the catalytic cycle.
- Mohamed Subarkhan,Ramesh
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p. 264 - 270
(2015/03/05)
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