- Au NPs@ polystyrene resin for mild and selective aerobic oxidation of 1,4 dioxane to 1,4 dioxan-2-ol
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Supported gold nanoparticles of sizes 5–8 nm have been found as highly efficient catalyst for the oxidation of 1,4 dioxane, a saturated ether, using elemental oxygen at low temperature. GC–MS analysis of the reaction mixture showed > 85% conversion of 1,4 dioxane with a TON of 1120 h? 1 to 1,4 dioxan-2-ol with 90% selectivity. 1,4 Dioxan-2-one was obtained as the major byproduct along with traces of acetic acid and methoxy dioxalane. The catalyst displayed excellent stability and recyclability. TEM analysis of reused catalyst indicated that there was no significant change in the size, shape and morphology of gold nanoparticles.
- Sharma, Anuj S.,Kaur, Harjinder
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Read Online
- Oxidation of Substituted Alkyl Radicals by IrCl62-, Fe(CN)63-, and MnO4- in Aqueous Solution. Electron Transfer versus Chlorine Transfer from IrCl62-
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Alkyl radicals substituted at Cα by alkyl, carboxyl, hydroxyl, alkoxyl, and chlorine react in aqueous solutions with IrIVCl62- to yield Ir(III) species.In the case of substitution by hydroxyl and alkoxyl, the rate constants are in the diffusion-controlled range ((4-6)x109 M-1 s-1) and the reaction proceeds by electron transfer.In the case of ethyl, methyl, carboxymethyl, and chloromethyl radicals the rate constants range from 3.1x109 for ethyl to 2.8x107 M-1 s-1 for trichloromethyl and the reaction proseeds by chlorine transfer from IrCl62- to the alkyl radical.With isopropyl and tert-butyl radicals the reaction proceeds by both electron and chlorine transfer.Alkyl radicals also react with Fe(CN)63-.The rate constants increase strongly with increasing alkylation at Cα from 5x106 for methyl to 3.6x109 M-1 s-1 for tert-butyl, indicating that the transition state for the reaction is highly polar.Rate constants for reaction of MnO4- with alkyl radical are of the order 109 M-1 s-1.
- Steenken, S.,Neta, P.
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Read Online
- Flavin Nitroalkane Oxidase Mimics Compatibility with NOx/TEMPO Catalysis: Aerobic Oxidization of Alcohols, Diols, and Ethers
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Biomimetic flavin organocatalysts oxidize nitromethane to formaldehyde and NOx - providing a relatively nontoxic, noncaustic, and inexpensive source for catalytic NO2 for aerobic TEMPO oxidations of alcohols, diols, and ethers. Alcohols were oxidized to aldehydes or ketones, cyclic ethers to esters, and terminal diols to lactones. In situ trapping of NOx and formaldehyde suggest an oxidative Nef process reminiscent of flavoprotein nitroalkane oxidase reactivity, which is achieved by relatively stable 1,10-bridged flavins. The metal-free flavin/NOx/TEMPO catalytic cycles are uniquely compatible, especially compared to other Nef and NOx-generating processes, and reveal selectivity over flavin-catalyzed sulfoxide formation. Aliphatic ethers were oxidized by this method, as demonstrated by the conversion of (-)-ambroxide to (+)-sclareolide.
- Thapa, Pawan,Hazoor, Shan,Chouhan, Bikash,Vuong, Thanh Thuy,Foss, Frank W.
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p. 9096 - 9105
(2020/08/14)
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- Production of Hydroxy Acids: Selective Double Oxidation of Diols by Flavoprotein Alcohol Oxidase
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Flavoprotein oxidases can catalyze oxidations of alcohols and amines by merely using molecular oxygen as the oxidant, making this class of enzymes appealing for biocatalysis. The FAD-containing (FAD=flavin adenine dinucleotide) alcohol oxidase from P. chrysosporium facilitated double and triple oxidations for a range of aliphatic diols. Interestingly, depending on the diol substrate, these reactions result in formation of either lactones or hydroxy acids. For example, diethylene glycol could be selectively and fully converted into 2-(2-hydroxyethoxy)acetic acid. Such a facile cofactor-independent biocatalytic route towards hydroxy acids opens up new avenues for the preparation of polyester building blocks.
- Fraaije, Marco W.,Martin, Caterina,Trajkovic, Milos
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p. 4869 - 4872
(2020/02/11)
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- Lignin-fueled photoelectrochemical platform for light-driven redox biotransformation
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The valorization of lignin has significant potential in producing commodity chemicals and fuels from renewable resources. However, the catalytic degradation of lignin is kinetically challenging and often requires noble metal catalysts to be used under harsh and toxic conditions. Here, we report the bias-free, solar reformation of lignin coupled with redox biotransformation in a tandem structure of a BiVO4 photoanode and perovskite photovoltaic. The tandem structure compensates for the potential gap between lignin oxidation and biocatalytic reduction through artificial Z-schematic absorption. We found that the BiVO4-catalyzed photoelectrochemical oxidation of lignin facilitated the fragmentation of higher molecular weight lignin into smaller carboxylated aliphatic and aromatic acids. Lignin oxidation induced photocurrent generation at the photoanode, which enabled efficient electroenzymatic reactions at the cathode. This study successfully demonstrates the oxidative valorization of lignin as well as biocatalytic reductions (e.g., CO2-to-formate and α-ketoglutarate-to-l-glutamate) in an unbiased biocatalytic PEC platform, which provides a new strategic approach for photo-biocatalysis using naturally abundant renewable resources.
- Boonmongkolras, Passarut,Choi, Eun-Gyu,Han, Seunghyun,Kim, Jinhyun,Kim, Kayoung,Kim, Yong Hwan,Lee, Sahng Ha,Lee, Yang Woo,Park, Chan Beum,Shin, Byungha,Trang, Nguyen Vu Thien,Wang, Ding
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supporting information
p. 5151 - 5160
(2020/08/25)
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- Pd-Catalyzed Aerobic Oxidation Reactions: Strategies to Increase Catalyst Lifetimes
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The palladium complex [(neocuproine)Pd(μ-OAc)]2[OTf]2 (1, neocuproine = 2,9-dimethyl-1,10-phenanthroline) is an effective catalyst precursor for the selective oxidation of primary and secondary alcohols, vicinal diols, polyols, and carbohydrates. Both air and benzoquinone can be used as terminal oxidants, but aerobic oxidations are accompanied by oxidative degradation of the neocuproine ligand, thus necessitating high Pd loadings. Several strategies to improve aerobic catalyst lifetimes were devised, guided by mechanistic studies of catalyst deactivation. These studies implicate a radical autoxidation mechanism initiated by H atom abstraction from the neocuproine ligand. Ligand modifications designed to retard H atom abstractions as well as the addition of sacrificial H atom donors increase catalyst lifetimes and lead to higher turnover numbers (TON) under aerobic conditions. Additional investigations revealed that the addition of benzylic hydroperoxides or styrene leads to significant increases in TON as well. Mechanistic studies suggest that benzylic hydroperoxides function as H atom donors and that styrene is effective at intercepting Pd hydrides. These strategies enabled the selective aerobic oxidation of polyols on preparative scales using as little as 0.25 mol % of Pd, a major improvement over previous work.
- Ho, Wilson C.,Chung, Kevin,Ingram, Andrew J.,Waymouth, Robert M.
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supporting information
p. 748 - 757
(2018/01/26)
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- Copper-catalyzed, stereoconvergent,: Cis -diastereoselective borylative cyclization of ω -mesylate- α, β -unsaturated esters and ketones
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The Cu(i)-catalyzed stereoconvergent borylative cyclization of ω-mesylate-α,β-unsaturated compounds is facilitated by a simple Cu-bisphosphine catalyst. This reaction provides a novel route to cis-β-boron-substituted five- and six-membered carbocycle and heterocycle esters. Mechanistic studies indicate that stereoconvergence and cis-substitution likely stem from the rapid enolation of the borylcopper adduct with the substrate double bond and the formation of a five-membered intermediate, respectively.
- Zuo, Ya-Jie,Chang, Xiao-Tong,Hao, Zhi-Ming,Zhong, Chong-Min
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supporting information
p. 6323 - 6327
(2017/08/10)
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- Efficient and Selective Cu/Nitroxyl-Catalyzed Methods for Aerobic Oxidative Lactonization of Diols
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Cu/nitroxyl catalysts have been identified that promote highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. The chemo- and regioselectivity of the reaction may be tuned by changing the identity of the nitroxyl cocatalyst. A Cu/ABNO catalyst system (ABNO = 9-azabicyclo[3.3.1]nonan-N-oxyl) shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system (TEMPO = 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl) displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols. These catalyst systems are compatible with all classes of alcohols (benzylic, allylic, aliphatic), mediate efficient lactonization of 1,4-, 1,5-, and some 1,6-diols, and tolerate diverse functional groups, including alkenes, heterocycles, and other heteroatom-containing groups.
- Xie, Xiaomin,Stahl, Shannon S.
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supporting information
p. 3767 - 3770
(2015/04/14)
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- (Meth)acrylate derivative, intermediate thereof, and polymer compound
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Provided are a polymerizable compound shown below which is useful as a raw material for a polymer having less swelling in developing, a polymer obtained by polymerizing a raw material containing the above polymerizable compound, a photoresist composition which contains the above polymer and which is improved in LWR and an efficient production process for the polymerizable compound described above: wherein n represents an integer of 0 to 2; R1 represents a hydrogen atom, methyl or trifluoromethyl; R2, R3, R4, R5, R6, R7, R8, R9 and R10 represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or the like; W represents an alkylene group having 1 to 10 carbon atoms or the like; and Y1 and Y2 represent an oxygen atom or a sulfur atom.
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Page/Page column 67; 68
(2013/07/25)
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- ACRYLATE ESTER DERIVATIVES AND POLYMER COMPOUNDS
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A cyclic alcohol of formula (II-1): wherein: R2, R3, and R4 are each independently a hydrogen atom, a linear alkyl group comprising 1 to 6 carbon atoms, a branched alkyl group comprising 3 to 6 carbon atoms, or a cyclic alkyl group comprising 3 to 6 carbon atoms; or R2 and R3 or R3 and R4 combine to form an alkylene group comprising 3 to 6 carbon atoms; m is 1 or 2; R5, R6, R7, R8, R9, and R10 are each independently a hydrogen atom, a linear alkyl group comprising 1 to 6 carbon atoms, a branched alkyl group comprising 3 to 6 carbon atoms, or a cyclic alkyl group comprising 3 to 6 carbon atoms; A is an oxygen atom; and B is an oxygen atom or a sulfur atom. In addition, a process for producing the cyclic alcohol of formula (II-1).
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Page/Page column 79-80
(2013/02/27)
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- An expeditious method for the preparation of 2-hydroxy-1,4-dioxane and Its Use in reductive alkylation of amines
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Selective oxidation of diethylene glycol by a ruthenium(VIII) species, obtained in situ from ruthenium(III) chloride-sodium- periodate in the presence of a catalytic quantity of water, affords a monoaldehyde in the form of the internal acetal 2-hydroxy-1,4-dioxane. This compound was used in reductive alkylations of selected primary and secondary amines, demonstrating its utility in the preparation of target structures with the 2-(2-hydroxyethoxy)ethylamino unit. Georg Thieme Verlag Stuttgart.
- Vinter, Adrijana,Avdagic, Amir,Stimac, Vlado,Palej, Ivana,Cikos, Ana,Sunjic, Vitomir,Alihodzic, Sulejman
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experimental part
p. 255 - 258
(2010/03/24)
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- Oxidation of ethers with dimethyldioxirane
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Oxidation of a series of tert-butyl ethers ButOR (R = Me, Et, CH2CH2Cl, Pri, Bui), diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, diisobutoxymethane, 1,4-dioxane, and tetrahydrofuran with dimethyldioxirane (DMDO) was studied. The reaction kinetics obeys the second-order equation w = k[DMDO][ether]. The rate constants in a range of 5-50°C and the activation parameters of the reaction were determined. The solvent effect on the oxidation rate was studied. The oxidation products are the corresponding alcohols and carbonyl compounds. The competition between the nonradical (oxygen insertion) and radical mechanisms of the reaction is discussed. The reactions of the parent dioxirane and DMDO with a series of methyl ethers MeOR′ (R′ = Me, Et, CH2CH2F, Pri) were studied by the density functional theory (DFT). The (U)B3LYP-6-311G(d,p) method was employed to calculate the geometry and energies of the reactants and transition states. The data obtained indicate a possible increase in the probability of oxidation via the radical route and an increase in the activation barrier for the substrates containing electron-withdrawing substituents.
- Grabovskiy,Timerghazin,Kabal'nova
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p. 2384 - 2393
(2007/10/03)
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- Oxidation vs. fragmentation in radiosensitization. Reactions of α-alkoxyalkyl radicals with 4-nitrobenzonitrile and oxygen. A pulse radiolysis and product analysis study
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α-Monoalkoxyalkyl radicals produced from 1,4-dioxane (100percent), 1,3-dioxane (56percent), tetrahydrofuran (92percent) and dimethyl ether (100percent) by H-abstraction by hydroxyl radicals generated in the radiolysis of water were found to react with 4-nitrobenzonitrile (NBN) by addition to give N-alkoxyaminoxyl-type radicals, which have absorption maxima at about 310 nm and decay very slowly (k = 0.4 - 1.0 s-1).On the other hand, the reaction of the α-dialkoxyalkyl radical, 1,3-dioxan-2-yl 3 with NBN leads to the rapid formation of the radical anion NBN.The N-alkoxyaminoxyl-type radicals (A in the case of 1,4-dioxane and D in the case of dimethyl ether) react with ascorbate (k ca. 2*104 dm3 mol-1 s-1).They have a very low reactivity with oxygen (k 3 dm3 mol-1 s-1 in the case of tetrahydrofuran).On the other hand, they are rapidly reduced by NBN radical anion (k ca. 109 dm3 mol-1 s-1 as observed with A and with B derived from 1,3-dioxane).The products -7 mol J-1> in the γ-radiolysis of N2O-saturated solution of 1,4-dioxane in the presence of NBN are 1,4-dioxan-2-one (0.3), 2-hydroxy-1,4-dioxane (2.5), ethane-1,2-diol monoformate (2.1), ethane-1,2-diol diformate (0.7), formaldehyde (2.1), 4-nitrosobenzonitrile and other reduction products of 4-nitrobenzonitrile.These products are accounted for as resulting from the fragmentation of the aminoxyl radical A by (a) heterolysis of the C-O bond (45percent leading to the one-electron oxidation of the 1,4-dioxan-2-yl radical) and (b) homolysis of the N-O bond (55percent leading to the formation of the 1,4-dioxan-2-oxyl radical which undergoes further fragmentation.The products from the reaction of methoxymethyl radicals with NBN under γ-radiolysis conditions are formaldehyde (5.7), methanol (2.5) and methyl formate (1.3).It is concluded that also in this case the decay of the aminoxyl radical D occurs by two pathways: the heterolysis route (46percent) and the homolysis route (54percent).In the presence of oxygen the 1,4-dioxan-2-yl radicals are converted into the corresponding peroxyl radicals.Their bimolecular decay (2k = 2.0*108 dm3 mol-1 s-1) yields the same products as in the case of NBN (albeit with a different product distribution and the formation of some peroxides): 1,4-dioxan-2-one (0.4), 2-hydroxy-1,4-dioxane (0.4), ethane-1,2-diol monoformate (0.6), ethane-1,2-diol diformate (2.8) and formaldehyde (0.6).These results indicate that fragmentation reactions involving the carbon-skeleton of organic radicals are important not only in the case of peroxyl radicals but they can also be induced by nitroaromatic sensitizers.In cells, reduction of the long-lived sensitizer adduct radicals by reducing agents such as ascorbate to give (toxic) hydroxylamine type products may compete with the homolytic or heterolytic fragmentation of the N-alkoxyaminoxyl radicals.
- Nese, Chandrasekhar,Schuchmann, Man Nien,Steenken, Steen,Sonntag, Clemens von
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p. 1037 - 1044
(2007/10/02)
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- Anodic Oxidation of Cycloaliphatic Mono- and Diethers in Aqueous Electrolytes
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The anodic oxidation of cycloaliphatic ethers such as tetrahydrofuran and tetrahydro-2H-pyran (1) as well as cycloaliphatic diethers such as 1,4-dioxane (3) and 1,3-dioxolane (6) was investigated under various conditions in aqueous 1 M H2SO4.The primary products in all cases are those of anodic hydroxylation in the 2-position to yield cyclic hemiacetals.This oxidation gives with platinum current efficiencies which are much larger than the results of the anodic methoxylation in methanol.The high selectivity in some cases is explained in terms of an O-insertion from PtO2. - The follow-up oxidation leads in the case of the cyclic monoethers to lactones, predominantly with lead dioxide. δ-Valerolactone is synthesized with more than 60percent current efficiency from 1.With diethers 3 and 6, anodic products of ring fragmentation are formed.The product distribution is indicative of an O-insertion under ring expansion.
- Wermeckes, Bernd,Beck, Fritz
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p. 1679 - 1682
(2007/10/02)
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