- Hydrogenation of Unsaturated Carboxylic Acid Catalyzed by Platinum-Silica Coupled with Alkylsilyl Chloride
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Platinum-silica catalysts coupled with alkylsilyl chloride were prepared for the regioselective hydrogenation of unsaturated compounds.These catalysts were stable in polar solvents.It was found that the carbon-carbon double bond far from a hydrophilic site was more rapidly hydrogenated in this catalyst system.
- Kuno, Hideyuki,Takahashi, Kyoko,Shibagaki, Makoto,Matsushita, Hajime
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Read Online
- Retinoic acid biosynthesis catalyzed by retinal dehydrogenases relies on a rate-limiting conformational transition associated with substrate recognition
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Retinoic acid (RA), a metabolite of vitamin A, exerts pleiotropic effects throughout life in vertebrate organisms. Thus, RA action must be tightly regulated through the coordinated action of biosynthetic and degrading enzymes. The last step of retinoic acid biosynthesis is irreversibly catalyzed by the NAD-dependent retinal dehydrogenases (RALDH), which are members of the aldehyde dehydrogenase (ALDH) superfamily. Low intracellular retinal concentrations imply efficient substrate molecular recognition to ensure high affinity and specificity of RALDHs for retinal. This study addresses the molecular basis of retinal recognition in human ALDH1A1 (or RALDH1) and rat ALDH1A2 (or RALDH2), through the comparison of the catalytic behavior of retinal analogs and use of the fluorescence properties of retinol. We show that, in contrast to long chain unsaturated substrates, the rate-limiting step of retinal oxidation by RALDHs is associated with acylation. Use of the fluorescence resonance energy transfer upon retinol interaction with RALDHs provides evidence that retinal recognition occurs in two steps: binding into the substrate access channel, and a slower structural reorganization with a rate constant of the same magnitude as the kcat for retinal oxidation: 0.18 vs. 0.07 and 0.25 vs. 0.1 s -1 for ALDH1A1 and ALDH1A2, respectively. This suggests that the conformational transition of the RALDH-retinal complex significantly contributes to the rate-limiting step that controls the kinetics of retinal oxidation, as a prerequisite for the formation of a catalytically competent Michaelis complex. This conclusion is consistent with the general notion that structural flexibility within the active site of ALDH enzymes has been shown to be an integral component of catalysis.
- Bchini, Rapha?l,Vasiliou, Vasilis,Branlant, Guy,Talfournier, Fran?ois,Rahuel-Clermont, Sophie
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- A new method for the protection of carboxylic acids with a triisopropylsiloxymethyl group
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An effective method for the protection of carboxylic acids with a triisopropylsiloxymethyl (TIPSOCH2) group is described. The reactions of various carboxylic acids with C12H25SCH 2OTIPS in the presence of CuBrs
- Yoshimura, Hikaru,Eto, Kohei,Takahashi, Keisuke,Ishihara, Jun,Hatakeyama, Susumi
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Read Online
- One-step solvent-free aerobic oxidation of aliphatic alcohols to esters using a tandem Sc-Ru?MOF catalyst
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Esters are an important class of chemicals in industry. Traditionally, ester production is a multi-step process involving the use of corrosive acids or acid derivatives (e.g. acid chloride, anhydride, etc.). Therefore, the development of a green synthetic protocol is highly desirable. This work reports the development of a metal-organic framework (MOF) supported tandem catalyst that can achieve direct alcohol to ester conversion (DAEC) using oxygen as the sole oxidizing agent under strictly solvent-free conditions. By incorporating Ru nanoparticles (NPs) along with a homogeneous Lewis acid catalyst, scandium triflate, into the nanocavities of a Zr MOF, MOF-808, the compound catalyst, Sc-Ru?MOF-808, can achieve aliphatic alcohol conversion up to 92% with ester selectivity up to 91%. A mechanistic study reveals a unique “via acetal” pathway in which the alcohol is first oxidized on Ru NPs and rapidly converted to an acetal on Sc(iii) sites. Then, the acetal slowly decomposes to release an aldehyde in a controlled manner for subsequent oxidation and esterification to the ester product. To the best of our knowledge, this is the first example of DAEC of aliphatic alcohols under solvent-free conditions with high conversion and ester selectivity.
- Feng, Tingkai,Li, Conger,Li, Tao,Zhang, Songwei
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supporting information
p. 1474 - 1480
(2022/03/08)
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- Combining photoredox catalysis and oxoammonium cations for the oxidation of aromatic alcohols to carboxylic acids
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A methodology is reported for converting alcohols to the corresponding carboxylic acids. A dual catalytic system involving a merger of photoredox catalysis and 4-acetamido-TEMPO is employed to carry out this oxidation process.
- Nandi, Jyoti,Hutcheson, Ellen L.,Leadbeater, Nicholas E.
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supporting information
(2020/12/25)
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- Atomically Dispersed Co Clusters Anchored on N-doped Carbon Nanotubes for Efficient Dehydrogenation of Alcohols and Subsequent Conversion to Carboxylic Acids
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The catalytic dehydrogenation of readily available alcohols to high value-added carbonyl compounds is a research hotspot with scientific significance. Most of the current research about this reaction is performed with noble metal-based homogeneous catalysts of high price and poor reusability. Herein, highly dispersed Co-cluster-decorated N-doped carbon nanotubes (Co/N-CNTs) were fabricated via a facile strategy and used for the dehydrogenation of alcohols with high efficiency. Various characterization techniques confirmed the presence of metallic Co clusters with almost atomic dispersion, and the N-doped carbon supports also enhanced the catalytic activity of Co clusters in the dehydrogenation reaction. Aldehydes as dehydrogenation products were further transformed in situ to carboxylic acids through a Cannizzaro-type pathway under alkaline conditions. The reaction pathway of the dehydrogenation of alcohols was clearly confirmed by theoretical calculations. This work should provide an effective and simple approach for the accurate design and synthesis of small Co-clusters catalysts for the efficient dehydrogenation-based transformation of alcohols to carboxylic acids under mild reaction conditions.
- Dong, Zhengping,Fang, Jian,Li, Boyang,Xu, Dan,Zhang, Fengwei,Zhao, Hong,Zhu, Hanghang
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p. 4536 - 4545
(2021/09/22)
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- Light and oxygen-enabled sodium trifluoromethanesulfinate-mediated selective oxidation of C-H bonds
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Visible light-induced organic reactions are important chemical transformations in organic chemistry, and their efficiency highly depends on suitable photocatalysts. However, the commonly used photocatalysts are precious transition-metal complexes and elaborate organic dyes, which hamper large-scale production due to high cost. Here, for the first time, we report a novel strategy: light and oxygen-enabled sodium trifluoromethanesulfinate-mediated selective oxidation of C-H bonds, allowing high-value-added aromatic ketones and carboxylic acids to be easily prepared in high-to-excellent yields using readily available alkyl arenes, methyl arenes and aldehydes as materials. The mechanistic investigations showed that the treatment of inexpensive and readily available sodium trifluoromethanesulfinate with oxygen under irradiation of light could in situ form a pentacoordinate sulfide intermediate as an efficient photosensitizer. The method represents a highly efficient, economical and environmentally friendly strategy, and the light and oxygen-enabled sodium trifluoromethanesulfinate photocatalytic system represents a breakthrough in photochemistry. This journal is
- Fu, Hua,Liu, Can,Liu, Yong,Yang, Haijun,Zhu, Xianjin
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supporting information
p. 4357 - 4363
(2020/07/14)
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- Oxidation of aromatic and aliphatic aldehydes to carboxylic acids by Geotrichum candidum aldehyde dehydrogenase
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Oxidation reaction is one of the most important and indispensable organic reactions, so that green and sustainable catalysts for oxidation are necessary to be developed. Herein, biocatalytic oxidation of aldehydes was investigated, resulted in the synthesis of both aromatic and aliphatic carboxylic acids using a Geotrichum candidum aldehyde dehydrogenase (GcALDH). Moreover, selective oxidation of dialdehydes to aldehydic acids by GcALDH was also successful.
- Hoshino, Tomoyasu,Yamabe, Emi,Hawari, Muhammad Arisyi,Tamura, Mayumi,Kanamaru, Shuji,Yoshida, Keisuke,Koesoema, Afifa Ayu,Matsuda, Tomoko
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- Process for the preparation of fatty acids
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The invention discloses a method for preparing fatty acid. The method comprises the following steps: providing a first reactant which is a furan compound containing an carbonyl group; providing a second reactant which is a compound containing a carboxyl group, an ester group or an anhydride group and can participate in a condensation reaction with the carbonyl group of the first reactant; allowingthe first reactant and the second reactant to participate in a first condensation reaction, and allowing a C=O bond of the carbonyl group of the first reactant to be connected with alpha carbon of the carbonyl group of the second reactant and to be converted into a C=C bond so as to form a condensation product; and carrying out a second-step reaction under hydrogen pressure in the presence of a co-catalytic system of a hydrogenation catalyst and Lewis acid, opening a furan ring of the condensation product, carrying out hydrodeoxygenation at the same time, removing all oxygen except for oxygenin the carboxyl group, and allowing a carbon chain to be saturated so as to obtain the fatty acid.
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Paragraph 0179-0206; 0210-0212
(2020/09/04)
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- Direct conversion of terminal alkenes to aldehydes via ozonolysis reaction in rotating zigzag bed
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In this study, continuous ozonolysis of terminal alkenes in a rotating zigzag bed was developed. Rotating zigzag bed is a new type high gravity unit relative to the previous rotating packed bed and can intensify mass transfer remarkably. The rotating zigzag bed takes advantage of centrifugal force to mix liquid and gas phase effectively. The H2O in acetone acts as an in situ reducing agent for the carbonyl oxide intermediate, providing aldehydes directly from the reaction mixture. Critical factors were investigated and achieved optimum reaction conditions. Under these conditions, the yields of series aldehydes ranged from 72.3 to 95.8percent. The discrepancy in product yields among different olefin substrates likely originates from the electronic stability of the carbonyl oxide intermediate, which is longer lived for aryl olefines with electron donor group and longer carbon chain alkene (CnH2n, n ≥ 10).
- Liang, Zhengyong,Wei, Tong,Xie, Jun,Li, Hua,Liu, Hui
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p. 2379 - 2384
(2020/05/25)
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- Catalytic deoxygenation of bio-based 3-hydroxydecanoic acid to secondary alcohols and alkanes
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This work comprises the selective deoxygenation of bio-derivable 3-hydroxydecanoic acid to either linear alkanes or secondary alcohols in aqueous phase and H2-atmosphere over supported metal catalysts. Among the screened catalysts, Ru-based systems were identified to be most active. By tailoring the catalyst, the product selectivity could be directed to either secondary alcohols or linear alkanes. In the absence of a Br?nsted acidic additive, 2-nonanol and 3-decanol were accessible with a yield of 79% and 6% respectively, both of which can be used in food and perfume industries as flavoring agents and fragrances. To produce alkanes, we successfully synthesized a bifunctional Ru/HZSM-5 catalyst. The acidic zeolite support facilitated the dehydration of the intermediary formed alcohols to alkenes, while the following hydrogenation occurred at the Ru centers. Thus, full 3-hydroxydecanoic acid deoxygenation to nonane and decane, which are both well-established as diesel and jet fuels, was achieved with up to 72% and 12% yield, respectively.
- Artz, Jens,Brosch, Sebastian,Golchert, Christiane,Hergesell, Adrian H.,Mensah, Joel B.,Palkovits, Regina
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p. 3522 - 3531
(2020/08/28)
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- Synthetic method of acid compound
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The invention belongs to the field of organic synthesis, and particularly relates to a synthetic method of an acid compound. An acid anhydride compound and an alkyl bromide or a functionalized alkyl bromide are subjected to a cross-electrophilic coupling reaction to synthesize an acid compound, so that the application of the alkyl bromide in the cross-electrophilic coupling reaction is expanded, and a novel non-traditional method for chemically and selectively constructing a carbon-carbon bond through a decarburization process is provided. The synthesis method is simple, economic, green and environment-friendly, and has wider applicability or is suitable for large-scale production.
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Paragraph 0028-0032; 0043
(2020/08/25)
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- PRODUCTION METHOD OF AMIDE COMPOUND
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PROBLEM TO BE SOLVED: To provide a production method of an amide compound, which can use a variety of carboxylic acid halides and can produce a desired amide compound at a yield higher than a batch process by suppressing a side reaction. SOLUTION: Provided is a production method of an amide compound using a flow type reactor, in which the flow type reactor includes: a first flow path; a second flow path; a first mixing means provided at a confluent part of the first flow path and the second flow path; and a third flow path that is connected to the first mixing means and arranged on a down stream side of the first mixing means, the production method comprising: a mixing step of obtaining a mixed liquid by circulating a first liquid containing the carboxylic acid halide in the first flow path, circulating a second liquid containing an amine compound having a molecular weight of 1,000 or less, an inorganic alkali and water in the second flow path, and mixing the first liquid and the second liquid by the first mixing means to obtain a mixture; and a reaction step of obtaining an amide compound by circulating the mixed liquid in the third flow path and reacting the carboxylic acid halide and the amine compound in the third flow path. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2020,JPO&INPIT
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Paragraph 0134-0137
(2020/10/08)
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- Method for catalytically oxidizing primary alcohol into corresponding carboxylic acid and simultaneously co-producing corresponding alpha olefin
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The invention relates to a method for catalytically oxidizing primary alcohol into corresponding carboxylic acid and simultaneously co-producing corresponding alpha olefin. The method comprises the following steps: mixing primary alcohol shown as a substrate (I), a catalyst cobalt salt, a nitrogen-containing ligand and a solvent, refluxing and stirring for 4-48 hours in an oxygen or air atmospherewith a certain pressure, and distilling and separating the reacted liquid to obtain carboxylic acid shown as (II) and alpha olefin in a certain proportion. The cobalt salt catalyst used in the methodis cheap and easy to obtain, the used nitrogen-containing ligand is a commercial nitrogen-containing compound, the used oxidant is oxygen or air, the reaction condition is mild, and various primary alcohols can be converted into corresponding carboxylic acids and alpha olefins at a high conversion rate under the condition of low cost.
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Paragraph 0034-0035
(2020/12/30)
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- Platinum on carbon–catalyzed and chemoselective aqueous oxygen oxidation of aromatic acetals to benzoic acids
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Novel chemoselective transformations can diversify the synthetic pathways of the target molecules. The chemoselective oxidation of aromatic acetals to benzoic acid derivatives under platinum on carbon (Pt/C)–catalyzed oxygen oxidation conditions has been newly developed with a tolerance of aliphatic acetals and ketals. The present oxidation was clean and useful from the viewpoint of the easy removal of Pt/C and the use of molecular oxygen as a green oxidant in water as an abundant, non-toxic and environmentally friendly solvent.
- Yasukawa, Naoki,Matsuda, Takumi,Shimizu, Eisho,Sajiki, Hironao,Sawama, Yoshinari
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p. 145 - 152
(2020/01/28)
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- Silica gel-mediated self-aldol reactions of highly volatile aldehydes under organic solvent-free conditions without reflux condenser
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Silica gel-mediated self-aldol reactions were catalyzed by piperidine to give the corresponding α,β-conjugated aldehydes in good yields. The aldol reactions of 4-nitro-, 4-trifluoromethyl-, and 4-chlorobenzaldehydes with acetone afforded the corresponding aldol products. Highly volatile aldehydes and acetone could be employed even without a reflux condenser for these reactions. Silica gel could be recycled five times without any significant decrease of the yields of the products.
- Tanemura, Kiyoshi
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p. 1924 - 1928
(2019/06/24)
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- Supramolecular photochemistry of encapsulated caged: Ortho -nitrobenzyl triggers
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ortho-Nitrobenzyl (oNB) triggers have been extensively used to release various molecules of interest. However, the toxicity and reactivity of the spent chromophore, o-nitrosobenzaldehyde, remains an unaddressed difficulty. In this study we have applied the well-established supramolecular photochemical concepts to retain the spent trigger o-nitrosobenzaldehyde within the organic capsule after release of water-soluble acids and alcohols. The sequestering power of organic capsules for spent chromophores during photorelease from ortho-nitrobenzyl esters, ethers and alcohols is demonstrated with several examples.
- Kamatham, Nareshbabu,Raj, A. Mohan,Givens, Richard S.,Da Silva, José P.,Ramamurthy
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p. 2411 - 2420
(2019/10/21)
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- Identification and Quantitation of Four New 2-Alkylthiazolidine-4-carboxylic Acids Formed in Orange Juice by a Reaction of Saturated Aldehydes with Cysteine
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Despite several technological efforts to maximize the quality and shelf life of chilled stored not-from-concentrate orange juice, changes in the overall aroma profile might occur during storage. Besides the degradation of terpenoids, a loss of the aroma-active aldehydes, hexanal, octanal, nonanal, and decanal as well-as of 1-penten-3-one were recently confirmed as a major cause for the changes in the aroma profile of orange juice even during storage under aseptic conditions at 0 °C. To unravel the fate of the aroma-active aldehydes, model experiments were carried out considering the oxidation into the corresponding acids as well as a reaction with free amino acids present in orange juice. The oxidation into the acids could be confirmed by isotope labeling experiments; additionally, the reaction of the four aldehydes mentioned above with l-cysteine yielded four new compounds identified as 2-alkylsubstituted thiazolidine-4-carboxylic acids. Their quantitation in orange juice samples by newly developed stable isotope dilution assays revealed that these acids were already present in the fresh samples but were considerably increased after storage. Labeling experiments in orange juice administered with either labeled octanal or labeled cysteine confirmed that the reaction quickly occurs in the juice. The data contribute another puzzle piece to the loss of aroma-active aldehydes during orange juice storage, which may also be relevant in other foods.
- Mall, Veronika,Sellami, Ines,Schieberle, Peter
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p. 11073 - 11082
(2018/10/24)
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- A biocatalytic method for the chemoselective aerobic oxidation of aldehydes to carboxylic acids
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Herein, we present a study on the oxidation of aldehydes to carboxylic acids using three recombinant aldehyde dehydrogenases (ALDHs). The ALDHs were used in purified form with a nicotinamide oxidase (NOx), which recycles the catalytic NAD+ at the expense of dioxygen (air at atmospheric pressure). The reaction was studied also with lyophilised whole cell as well as resting cell biocatalysts for more convenient practical application. The optimised biocatalytic oxidation runs in phosphate buffer at pH 8.5 and at 40 °C. From a set of sixty-one aliphatic, aryl-Aliphatic, benzylic, hetero-Aromatic and bicyclic aldehydes, fifty were converted with elevated yield (up to >99%). The exceptions were a few ortho-substituted benzaldehydes, bicyclic heteroaromatic aldehydes and 2-phenylpropanal. In all cases, the expected carboxylic acid was shown to be the only product (>99% chemoselectivity). Other oxidisable functionalities within the same molecule (e.g. hydroxyl, alkene, and heteroaromatic nitrogen or sulphur atoms) remained untouched. The reaction was scaled for the oxidation of 5-(hydroxymethyl)furfural (2 g), a bio-based starting material, to afford 5-(hydroxymethyl)furoic acid in 61% isolated yield. The new biocatalytic method avoids the use of toxic or unsafe oxidants, strong acids or bases, or undesired solvents. It shows applicability across a wide range of substrates, and retains perfect chemoselectivity. Alternative oxidisable groups were not converted, and other classical side-reactions (e.g. halogenation of unsaturated functionalities, Dakin-Type oxidation) did not occur. In comparison to other established enzymatic methods such as the use of oxidases (where the concomitant oxidation of alcohols and aldehydes is common), ALDHs offer greatly improved selectivity.
- Knaus, Tanja,Tseliou, Vasilis,Humphreys, Luke D.,Scrutton, Nigel S.,Mutti, Francesco G.
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supporting information
p. 3931 - 3943
(2018/09/11)
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- Zinc Oxide-Catalyzed Dehydrogenation of Primary Alcohols into Carboxylic Acids
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Zinc oxide has been developed as a catalyst for the dehydrogenation of primary alcohols into carboxylic acids and hydrogen gas. The reaction is performed in mesitylene solution in the presence of potassium hydroxide, followed by workup with hydrochloric acid. The transformation can be applied to both benzylic and aliphatic primary alcohols and the catalytically active species was shown to be a homogeneous compound by a hot filtration test. Dialkylzinc and strongly basic zinc salts also catalyze the dehydrogenation with similar results. The mechanism is believed to involve the formation of a zinc alkoxide which degrades into the aldehyde and a zinc hydride. The latter reacts with the alcohol to form hydrogen gas and regenerate the zinc alkoxide. The degradation of a zinc alkoxide into the aldehyde upon heating was confirmed experimentally. The aldehyde can then undergo a Cannizzaro reaction or a Tishchenko reaction, which in the presence of hydroxide leads to the carboxylic acid.
- Monda, Fabrizio,Madsen, Robert
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supporting information
p. 17832 - 17837
(2018/11/23)
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- Hydrofunctionalization of olefins to value-added chemicals: Via photocatalytic coupling
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A green strategy was developed for the synthesis of various value-added chemicals using methanol, acetonitrile, acetic acid, acetone and ethyl acetate as the hydrogen source by coupling them with olefins over heterogeneous photocatalysts. A radical coupling mechanism was proposed for the hydrofunctionalization of olefins with methanol to higher aliphatic alcohols over the Pt/TiO2 catalyst as the model reaction. C-H bond cleavage and C-C bond formation between photogenerated radicals and terminal olefins were accomplished in a single reaction at high efficiency. Our approach is atomically economical with high anti-Markovnikov regioselectivity and promising application potential under mild reaction conditions.
- Fan, Yonghui,Li, Shenggang,Bao, Jingxian,Shi, Lei,Yang, Yanzhang,Yu, Fei,Gao, Peng,Wang, Hui,Zhong, Liangshu,Sun, Yuhan
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supporting information
p. 3450 - 3456
(2018/08/06)
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- A mild method for synthesizing carboxylic acids by oxidation of aldoximes using hypervalent iodine reagents
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A mild oxidation method for the conversion of aldoximes to carboxylic acids was developed mediated by hypervalent iodine reagents. This method covers a wide range of functionalized aldoximes and proceeds under mild conditions, utilizing PhI(OH)OTs as an oxidant.
- Nakamura, Akira,Kanou, Hodaka,Tanaka, Junki,Imamiya, Akira,Maegawa, Tomohiro,Miki, Yasuyoshi
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supporting information
p. 541 - 544
(2018/02/07)
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- Synthesis of medium-chain carboxylic acids or α,ω-dicarboxylic acids from cellulose-derived platform chemicals
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Medium-chain fatty acids and their derivatives have important applications in the energy and chemical industries. Thus, we have prepared a series of medium-chain fatty acids by the selective hydrodeoxygenation of the aldol condensation products derived from cellulose using a metal triflate and Pd/C catalyst system. The selective retention of the carboxyl group is a notable feature of this catalytic system.
- Li, Xing-Long,Zhang, Kun,Jiang, Ju-Long,Zhu, Rui,Wu, Wei-Peng,Deng, Jin,Fu, Yao
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supporting information
p. 362 - 368
(2018/02/07)
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- Synthesis of α,β-unsaturated aldehydes as potential substrates for bacterial luciferases
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Bacterial luciferase catalyzes the monooxygenation of long-chain aldehydes such as tetradecanal to the corresponding acid accompanied by light emission with a maximum at 490?nm. In this study even numbered aldehydes with eight, ten, twelve and fourteen carbon atoms were compared with analogs having a double bond at the α,β-position. These α,β-unsaturated aldehydes were synthesized in three steps and were examined as potential substrates in vitro. The luciferase of Photobacterium leiognathi was found to convert these analogs and showed a reduced but significant bioluminescence activity compared to tetradecanal. This study showed the trend that aldehydes, both saturated and unsaturated, with longer chain lengths had higher activity in terms of bioluminescence than shorter chain lengths. The maximal light intensity of (E)-tetradec-2-enal was approximately half with luciferase of P. leiognathi, compared to tetradecanal. Luciferases of Vibrio harveyi and Aliivibrio fisheri accepted these newly synthesized substrates but light emission dropped drastically compared to saturated aldehydes. The onset and the decay rate of bioluminescence were much slower, when using unsaturated substrates, indicating a kinetic effect. As a result the duration of the light emission is doubled. These results suggest that the substrate scope of bacterial luciferases is broader than previously reported.
- Brodl, Eveline,Ivkovic, Jakov,Tabib, Chaitanya R.,Breinbauer, Rolf,Macheroux, Peter
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p. 1487 - 1495
(2017/02/18)
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- Preparation method of capric acid
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The invention discloses a preparation method of capric acid. The preparation method comprises the following steps: carrying out hydrodeoxygenation on a substance A and hydrogen, trifluoromethanesulfonic acid and a hydrogenation catalyst so as to obtain capric acid. According to the preparation method, the atom economy is good, the product yield is high, the product purity is high, the pollution to the environment is slight, the process route is simple, the operation is convenient, and the preparation method is suitable for industrial large-scale production.
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Paragraph 0094; 0095; 0097; 0102; 0104
(2017/12/30)
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- Pentasaccharide resin glycosides with multidrug resistance reversal activities from the seeds of: Pharbitis nil
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Resin glycosides are novel P-glycoprotein inhibitors. In order to evaluate their multidrug resistance (MDR) reversal activities, we isolated seven new resin glycosides, pharbitins A-G (1-7) from the seeds of Pharbitis nil. Their chemical structures were determined by extensive application of high resolution 2D NMR techniques, HRESIMS and chemical methods. Compounds 1-4 and 6 were evaluated for their MDR reversal activities in KB/VCR, A549/T and K562/ADR cells. Among them, compound 2 showed moderate MDR reversal activity in KB/VCR cells, and increased the cytotoxicity of vincristine by 2.2-fold when incorporated at 25 μM. A structure-activity relationship study revealed that substituting Rha′′ C-3 with a trans-cinnamoyl group improves the MDR reversal activity. Also, an intracellular Rh123 accumulation assay demonstrated that compound 2 could inhibit the function of P-gp.
- Li, Jun,Wang, Wen-Qiong,Tang, Shuai,Song, Wei-Bin,Huang, Min,Xuan, Li-Jiang
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supporting information
p. 52001 - 52009
(2017/11/22)
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- Chemoselective continuous-flow hydrogenation of aldehydes catalyzed by platinum nanoparticles dispersed in an amphiphilic resin
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A chemoselective continuous-flow hydrogenation of aldehydes catalyzed by a dispersion of platinum nanoparticles in an amphiphilic polymer (ARP-Pt) has been developed. Aromatic and aliphatic aldehydes bearing various reducible functional groups, such as keto, ester, or amide groups, readily underwent flow hydrogenation in aqueous solutions within 22 s in a continuous-flow system containing ARP-Pt to give the corresponding primary benzylic or aliphatic alcohols in ≤99% yield with excellent chemoselectivity. Moreover, the long-term continuous-flow hydrogenation of benzaldehyde for 8 days was realized, and the total turnover number of the catalyst reached 997. The flow hydrogenation system provides an efficient and practical method for the chemoselective hydrogenation of aldehydes bearing reducible functional groups.
- Osako, Takao,Torii, Kaoru,Hirata, Shuichi,Uozumi, Yasuhiro
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p. 7371 - 7377
(2017/11/09)
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- Ultrasound-assisted removal of Acid Red 17 using nanosized Fe3O4-loaded coffee waste hydrochar
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The Fe3O4-loaded coffee waste hydrochar (Fe3O4-CHC) was synthesized using a simple precipitation method. The as-prepared adsorbent was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FT-IR). The EDX analysis indicated the presence of Fe in the structure of Fe3O4-CHC. The specific surface area of hydrochar increased from 17.2 to 34.7 m2/g after loading of Fe3O4 nanoparticles onto it. The prepared Fe3O4-CHC was used for removal of Acid Red 17 (AR17) through ultrasound-assisted process. The decolorization efficiency decreased from 100 to 74% with the increase in initial dye concentration and from 100 to 91 and 85% in the presence of NaCl and Na2SO4, respectively. The synthesized Fe3O4-CHC exhibited good stability in the repeated adsorption-desorption cycles. The high correlation coefficient (R2 = 0.997) obtained from Langmuir model indicated that physical and monolayer adsorption of dye molecules occurred on the Fe3O4-CHC surface. Furthermore, the by-products generated through the degradation of AR17 was identified by gas chromatography–mass spectrometry analysis.
- Khataee, Alireza,Kayan, Berkant,Kalderis, Dimitrios,Karimi, Atefeh,Akay, Sema,Konsolakis, Michalis
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- MnO2-promoted carboesterification of alkenes with anhydrides: A facile approach to γ-lactones
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An efficient carboesterification of alkenes with anhydrides promoted by MnO2 has been developed to afford functionalized γ-lactones in good to excellent yields. This method shows a broad substrate scope and provides a valuable and convenient synthetic tool for constructing γ-lactones.
- Wu, Lihuan,Zhang, Zhenming,Liao, Jianhua,Li, Jianxiao,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 2628 - 2631
(2016/02/18)
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- NOVEL GENE DERIVED FROM MUD FLAT METAGENOME AND NOVEL PROTEIN OBTAINED THEREFROM SHOWING COACTIVITY OF PHOSPHOLIPASE AND LIPASE
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The present invention relates to a novel gene derived from a tidal flat metagenome, and a novel protein obtained therefrom showing the coactivity of phospholipase and lipase. Specifically, the novel gene isolated from the metagenome library of tidal flat sedimentsand the protein having phospholipase and lipase activities encoded from the novel gene: are expressed in a water-soluble form to be mass-producible; enable ultra high-purity protein to be obtained through single step purification using an Ni-NTA column; show good activity in the pH range of 5 ?? 10; maintain good low temperature activity and stability up to a temperature of 3°C to 40°C; and have high resistance against various organic solvents. Therefore, the novel gene and the protein can be usefully used for various industrial fields such as the purification and conversion of oil and fat, bio-medicine, and fine chemistry.
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Paragraph 0083-0084
(2016/03/14)
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- Helical supramolecular polymerization of: C 3-symmetric amides and retroamides: On the origin of cooperativity and handedness
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The cooperative supramolecular polymerization of 1 and 2 yields P- or M-type helical aggregates depending on the absolute configuration (S or R) of the stereogenic centres attached to the side chains. The connectivity of the amide group does not affect the handedness of the helical aggregates, but determines a larger cooperativity for retroamides 1.
- Buendía, Julia,Calbo, Joaquín,García, Fátima,Aragó, Juan,Viruela, Pedro M.,Ortí, Enrique,Sánchez, Luis
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supporting information
p. 6907 - 6910
(2016/06/06)
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- Dehydrogenative Synthesis of Carboxylic Acids from Primary Alcohols and Hydroxide Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex
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Primary alcohols have been reacted with hydroxide and the ruthenium complex [RuCl2(IiPr)(p-cymene)] to afford carboxylic acids and dihydrogen. The dehydrogenative reaction is performed in toluene, which allows for a simple isolation of the products by precipitation and extraction. The transformation can be applied to a range of benzylic and saturated aliphatic alcohols containing halide and (thio)ether substituents, while olefins and ester groups are not compatible with the reaction conditions. Benzylic alcohols undergo faster conversion than other substrates, and a competing Cannizzaro reaction is most likely involved in this case. The kinetic isotope effect was determined to be 0.67 using 1-butanol as the substrate. A plausible catalytic cycle was characterized by DFT/B3LYP-D3 and involved coordination of the alcohol to the metal, β-hydride elimination, hydroxide attack on the coordinated aldehyde, and a second β-hydride elimination to furnish the carboxylate.
- Santilli, Carola,Makarov, Ilya S.,Fristrup, Peter,Madsen, Robert
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p. 9931 - 9938
(2016/11/02)
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- Determination of Key Hydrocarbon Autoxidation Products by Fluorescence
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Hydroperoxides and carboxylic acids are key primary products that arise in the autoxidation of hydrocarbons. We have developed a simple approach to rapidly and simultaneously determine both types of products using hydroperoxide- and acid-sensitive moieties conjugated to nonpolar coumarin- and BODIPY-based fluorophores. The coumarin- and BODIPY-conjugated amine probes described here undergo 38- and 8-fold enhancement, respectively, upon protonation in a solvent system compatible with heavy hydrocarbons. The latter can be used directly with our previously described hydroperoxide-sensitive coumarin-conjugated phosphine probe to enable rapid quantification of both carboxylic acids and hydroperoxides in hydrocarbon samples. The utility of the approach is illustrated by the ready determination of the differing relative rates of hydroperoxide and acid formation with changes in hydrocarbon structure (e.g., n-hexadecane vs 1-hexadecene vs a lubricant base stock). The method offers significant versatility and automation compared with common but laborious titration approaches, and greatly improves screening efficiency and accuracy for the identification of novel radical-trapping antioxidants for high temperature applications. This application was demonstrated by the automated analysis of hydroperoxides and carboxylic acids (by microplate reader) in samples from 24 inhibited autoxidations of a lubricating oil, which were carried out on a parallel synthesizer at 160 °C in triplicate in a single day.
- Shah, Ron,Pratt, Derek A.
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p. 6649 - 6656
(2016/08/16)
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- Two pentasaccharide resin glycosides from Argyreia acuta
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Two new compounds of acutacosides 1 and 2, pentasaccharide resin glycosides were isolated from the aerial parts of Argyreia acuta. The core of the two compounds was operculinic acid A, and they were esterfied at the same position, just one substituent group was linked at C-2 of Rha. The absolute configuration of the aglycone in the two compounds was established by Mosher's method, which was (11S)-hydroxyhexadecanoic acid (jalapinolic acid). Their structures were established by a combination of spectroscopic and chemical methods.
- Yin, Yong-Qin,Pan, Jie-Tao,Yu, Bang-Wei,Cui, Hong-Hua,Yan, You-Shao,Chen, Yan-Fen
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- Resin glycosides from Ipomoea wolcottiana as modulators of the multidrug resistance phenotype in vitro
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Recycling liquid chromatography was used for the isolation and purification of resin glycosides from the CHCl3-soluble extracts prepared using flowers of Ipomoea wolcottiana Rose var. wolcottiana. Bioassay-guided fractionation, using modulation of both antibiotic activity against multidrug-resistant strains of Gram-negative bacteria and vinblastine susceptibility in breast carcinoma cells, was used to isolate the active glycolipids as modulators of the multidrug resistance phenotype. An ester-type dimer, wolcottine I, one tetra- and three pentasaccharides, wolcottinosides I-IV, in addition to the known intrapilosin VII, were characterized by NMR spectroscopy and mass spectrometry. In vitro assays established that none of these metabolites displayed antibacterial activity (MIC > 512 μg/mL) against multidrug-resistant strains of Escherichia coli, and two nosocomial pathogens: Salmonella enterica serovar Typhi and Shigella flexneri; however, when tested (25 μg/mL) in combination with tetracycline, kanamycin or chloramphenicol, they exerted a potentiation effect of the antibiotic susceptibility up to eightfold (64 μg/mL from 512 μg/mL). It was also determined that these non-cytotoxic (CI50 > 8.68 μM) agents modulated vinblastine susceptibility at 25 μg/mL in MFC-7/Vin+ cells with a reversal factor (RFMCF-7/Vin+) of 2-130 fold.
- Corona-Casta?eda, Berenice,Rosas-Ramírez, Daniel,Casta?eda-Gómez, Jhon,Aparicio-Cuevas, Manuel Alejandro,Fragoso-Serrano, Mabel,Figueroa-González, Gabriela,Pereda-Miranda, Rogelio
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- One-pot oxidative cleavage of olefins to synthesize carboxylic acids by a telescoped ozonolysis-oxidation process
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A mild one-pot ozonolysis-oxidation process of alkenes to synthesize carboxylic acids is described. Conducting the ozonolysis in an aqueous organic solvent eliminates secondary ozonide formation and the intermediates generated are readily converted into a carboxylic acid by adding sodium chlorite. Following a reductive quench, the desired acids are isolated in high purity and high yield by simple extraction.
- Cochran, Brian M.
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supporting information
p. 245 - 248
(2016/01/20)
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- Palladium on carbon-catalyzed aqueous transformation of primary alcohols to carboxylic acids based on dehydrogenation under mildly reduced pressure
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The catalytic dehydrogenation of alcohols to carbonyl products is a green sustainable oxidation with no production of waste except for hydrogen, which can be an energy source. Additionally, a reusable heterogeneous catalyst is valuable from the viewpoint of process chemistry and water is a green solvent. We have accomplished the palladium on carbon (Pd/C)-catalyzed dehydrogenation of primary alcohols to carboxylic acids in water under a mildly reduced pressure (800 hPa). The reduced pressure can be easily controlled by the vacuum controller of the rotary evaporator to remove the excess of generated hydrogen, which causes the reduction (reverse reaction) of aldehydes to alcohols (starting materials) and other undesirable side reactions. The present method is applicable to the reaction of various aliphatic and benzylic alcohols to the corresponding carboxylic acids, and the Pd/C could be reused at least 5 times.
- Sawama, Yoshinari,Morita, Kosuke,Asai, Shota,Kozawa, Masami,Tadokoro, Shinsuke,Nakajima, Junichi,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 1205 - 1210
(2015/04/22)
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- Synthesis of 1,3-Amino Alcohols, 1,3-Diols, Amines, and Carboxylic Acids from Terminal Alkynes
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The half-sandwich ruthenium complexes 1-3 activate terminal alkynes toward anti-Markovnikov hydration and reductive hydration under mild conditions. These reactions are believed to proceed via addition of water to metal vinylidene intermediates (4). The functionalization of propargylic alcohols by metal vinylidene pathways is challenging owing to decomposition of the starting material and catalytic intermediates. Here we show that catalyst 2 can be employed to convert propargylic alcohols to 1,3-diols in high yield and with retention of stereochemistry at the propargylic position. The method is also amenable to propargylic amine derivatives, thereby establishing a route to enantioenriched 1,3-amino alcohol products. We also report the development of formal anti-Markovnikov reductive amination and oxidative hydration reactions to access linear amines and carboxylic acids, respectively, from terminal alkynes. This chemistry expands the scope of products that can be prepared from terminal alkynes by practical and high-yielding metal-catalyzed methods.
- Zeng, Mingshuo,Herzon, Seth B.
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p. 8604 - 8618
(2015/09/15)
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- Aerobic flow oxidation of alcohols in water catalyzed by platinum nanoparticles dispersed in an amphiphilic polymer
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We have developed a technique for the aqueous aerobic flow oxidation of alcohols in a continuous-flow reactor containing platinum nanoparticles dispersed on an amphiphilic polystyrene-poly(ethylene glycol) resin (ARP-Pt). Various primary and secondary alcohols including aliphatic, aromatic and heteroaromatic alcohols were efficiently oxidized within 73 seconds in a flowing aqueous system at 100-120°C under 40-70 bar of the system pressure to give the corresponding carboxylic acids and ketones, respectively, in up to 99% yield. Benzaldehydes could be also prepared selectively from benzyl alcohols by conducting the flow oxidation under the standard conditions in the presence of triethylamine. Moreover, a practical gram-scale synthesis of surfactants was realized in the aqueous aerobic continuous flow oxidation for 36-116 hours. This aerobic flow oxidation system provides a safe, clean, green, rapid and efficient practical method for oxidizing alcohols.
- Osako, Takao,Torii, Kaoru,Uozumi, Yasuhiro
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p. 2647 - 2654
(2015/02/05)
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- A green and sustainable phosphine-free NHC-ruthenium catalyst for selective oxidation of alcohols to carboxylic acids in water
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In this work, we present a new catalytic system for the selective dehydrogenative oxidation of primary alcohols to carboxylic acids using a phosphine-free NHC-ruthenium catalyst in water under mild reaction conditions. With this catalytic system, a variety of primary alcohols have been converted to carboxylic acids respectively, in aqueous media, without using any additional oxidant; the only side product in this reaction is molecular hydrogen. This novel synthetic protocol is applied for direct oxidation of biologically active monosaccharides and polymers with primary alcohol groups in the side chain. The use of water as a solvent and oxygen donor as well as the absence of any toxic oxidizing agent make this atom economical reaction interesting from an environmental point of view.
- Malineni, Jagadeesh,Keul, Helmut,M?ller, Martin
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supporting information
p. 17409 - 17414
(2015/10/12)
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- Activity of neutral and alkaline ceramidases on fluorogenic N -acylated coumarin-containing aminodiols
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Ceramidases catalyze the cleavage of ceramides into sphingosine and fatty acids. Previously, we reported on the use of the RBM14 fluorogenic ceramide analogs to determine acidic ceramidase activity. In this work, we investigated the activity of other amidohydrolases on RBM14 compounds. Both bacterial and human purified neutral ceramidases (NCs), as well as ectopically expressed mouse neutral ceramidase hydrolyzed RBM14 with different selectivity, depending on the N -acyl chain length. On the other hand, microsomes from alkaline ceramidase (ACER)3 knockdown cells were less competent at hydrolyzing RBM14C12, RBM12C14, and RBM14C16 than controls, while microsomes from ACER2 and ACER3 overexpressing cells showed no activity toward the RBM14 substrates. Conversely, N -acylethanolamine-hydrolyzing acid amidase (NAAA) overexpressing cells hydrolyzed RBM14C14 and RBM14C16 at acidic pH. Overall, NC, ACER3, and, to a lesser extent, NAAA hydrolyze fluorogenic RBM14 compounds. Although the selectivity of the substrates toward ceramidases can be modulated by the length of the N -acyl chain, none of them was specific for a particular enzyme. Despite the lack of specificity, these substrates should prove useful in library screening programs aimed at identifying potent and selective inhibitors for NC and ACER3.
- Casasampere, Mireia,Camacho, Luz,Cingolani, Francesca,Casas, Josefina,Egido-Gabás, Meritxell,Abad, José Luís,Bedia, Carmen,Xu, Ruijuan,Wang, Kai,Canals, Daniel,Hannun, Yusuf A.,Mao, Cungui,Fabrias, Gemma
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p. 2019 - 2028
(2015/11/17)
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- Amination of ω-Functionalized Aliphatic Primary Alcohols by a Biocatalytic Oxidation-Transamination Cascade
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Amination of non-activated aliphatic fatty alcohols to the corresponding primary amines was achieved through a five-enzyme cascade reaction by coupling a long-chain alcohol oxidase from Aspergillus fumigatus (LCAO-Af) with a ω-transaminase from Chromobacterium violaceum (ω-TA-Cv). The alcohol was oxidized at the expense of molecular oxygen to yield the corresponding aldehyde, which was subsequently aminated by the PLP-dependent ω-TA to yield the final primary amine product. The overall cascade was optimized with respect to pH, O2 pressure, substrate concentration, decomposition of H2O2 (derived from alcohol oxidation), NADH regeneration, and biocatalyst ratio. The substrate scope of this concept was investigated under optimized conditions by using terminally functionalized C4-C11 fatty primary alcohols bearing halogen, alkyne, amino, hydroxy, thiol, and nitrile groups.
- Pickl, Mathias,Fuchs, Michael,Glueck, Silvia M.,Faber, Kurt
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p. 3121 - 3124
(2015/10/19)
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- Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
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We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
- Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
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p. 1972 - 1978
(2015/02/19)
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- Batatins VIII-XI, glycolipid ester-type dimers from ipomoea batatas
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Sweet potato (Ipomoea batatas) is native to the tropics of Central and South America, where many varieties have been consumed for more that 5000 years. In developing countries, this crop is a recognized effective food for fighting malnutrition. Purification of the minor lipophilic glicolipids found in the n-hexane-soluble resin glycosides from the white-skinned variety was performed by preparative-scale recycling HPLC. Application of column overload, peak shaving, heart cutting, and recycling techniques permitted the purification of four new oligosaccharide ester-type dimer derivatives of jalapinolic acid, batatins VIII-XI (1-4). The structural characterization of these complex lipo-oligosaccharides was performed through NMR spectroscopy and MS, indicating that batatins VIII-XI (1-4) possess an oligomeric structure consisting of two pentasaccharide units of the known simonic acid B.
- Rosas-Ramírez, Daniel,Pereda-Miranda, Rogelio
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- Rhodium-on-carbon catalyzed hydrogen scavenger- and oxidant-free dehydrogenation of alcohols in aqueous media
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The efficient and catalytic dehydrogenation of alcohols is a clean approach for preparing carbonyl compounds accompanied only by the generation of hydrogen gas. We have accomplished the heterogeneous rhodium-on-carbon catalyzed dehydrogenation of secondary, as well as primary, alcohols to the corresponding ketones and carboxylic acids in water under basic conditions. This journal is the Partner Organisations 2014.
- Sawama, Yoshinari,Morita, Kosuke,Yamada, Tsuyoshi,Nagata, Saori,Yabe, Yuki,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 3439 - 3443
(2014/07/08)
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- Characterization of a novel hormone-sensitive lipase family esterase from Rhizomucor miehei with tertiary alcohol hydrolysis activity
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A novel esterase gene (designated RmEstB) from the thermophilic fungus Rhizomucor miehei was cloned and functionally expressed in Escherichia coli. Sequence analysis revealed a 960-bp open reading frame encoding a protein of 319 amino acids. The deduced protein sequence contained an HGGG motif, suggesting that the enzyme is a hormone-sensitive lipase (HSL) family esterase. It showed highest identity of 52% with the esterase from Pseudomonas mandelii. The recombinant esterase was purified to homogeneity at 5.1-fold purification with a recovery yield of 85%. The molecular mass of RmEstB was estimated to be 37 kDa by SDS-PAGE. RmEstB was most active at pH 7.5 and 50 °C. The enzyme was highly stable in the presence of 30% ethanol, methanol, acetone, isopropanol, dimethyl sulfoxide and acetonitrile. RmEstB showed a broad range of substrate specificities toward various p-nitrophenol (pNP) esters (C2-C10) and triglycerides (C2-C6), with the highest specific activities obtained for pNP acetate (255 U/mg) and triacetin (1330 U/mg), respectively. In addition, RmEstB efficiently catalyzed the hydrolysis of sterically hindered esters of tertiary alcohols. This study presents a novel fungal HSL family esterase with potential for some industrial applications.
- Yan, Qiao-Juan,Yang, Shao-Qing,Duan, Xiao-Jie,Xu, Hai-Bo,Liu, Yu,Jiang, Zheng-Qiang
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- Au/mesoporous-TiO2 as catalyst for the oxidation of alcohols to carboxylic acids with molecular oxygen in water
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Mesoporous TiO2 (meso-TiO2) with sharp pore size distribution was synthesized by hydrothermal method. The obtained meso-TiO 2 is in pure anatase phase and presents spheric aggregates with diameter of 1.0-1.5 μm, which consists of nanoparticles with size of 6-10 nm. Au supported on meso-TiO2 (Au/meso-TiO2) was prepared by urea deposition-precipitation method using HAuCl4 as gold source. The catalyst was characterized by X-ray diffraction, N2 adsorption, transmission electron microscopy and UV-vis diffuse reflectance spectroscopy. The catalytic performance of Au/meso-TiO2 was studied in the oxidation of 1-pentanol to n-valeric acid with molecular oxygen as oxidant in water under basic conditions. It was found that meso-TiO2 is a better support for gold catalyst in the oxidation of 1-pentanol than NaY zeolite, hydrotalcite, and nano-TiO2. Deposition-precipitation time, calcination temperature and Au loading affected the catalytic performance of Au/meso-TiO2. The catalyst can also effectively catalyze the oxidation of aliphatic (C3-C10) and aromatic alcohols to the corresponding carboxylic acids.
- Zhou, Lipeng,Chen, Minzhu,Wang, Youqiang,Su, Yunlai,Yang, Xiaomei,Chen, Chen,Xu, Jie
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p. 347 - 354
(2014/03/21)
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- Selective conversion of alcohols in water to carboxylic acids by in situ generated ruthenium trans dihydrido carbonyl PNP complexes
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In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process. This journal is
- Choi, Jong-Hoo,Heim, Leo E.,Ahrens, Mike,Prechtl, Martin H. G.
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p. 17248 - 17254
(2015/01/09)
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- Ketyl-type radicals from cyclic and acyclic esters are stabilized by SmI2(H2O)n: the role of SmI2(H 2O)n in post-electron transfer steps
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Mechanistic details pertaining to the SmI2-H2O- mediated reduction and reductive coupling of 6-membered lactones, the first class of simple unactivated carboxylic acid derivatives that had long been thought to lie outside the reducing range of SmI2, have been elucidated. Our results provide new experimental evidence that water enables the productive electron transfer from Sm(II) by stabilization of the radical anion intermediate rather than by solely promoting the first electron transfer as originally proposed. Notably, these studies suggest that all reactions involving the generation of ketyl-type radicals with SmI2 occur under a unified mechanism based on the thermodynamic control of the second electron transfer step, thus providing a blueprint for the development of a broad range of novel chemoselective transformations via open-shell electron pathways.
- Szostak, Michal,Spain, Malcolm,Procter, David J.
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supporting information
p. 8459 - 8466
(2014/06/24)
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- Sulfonic acid resin-catalyzed oxidation of aldehydes to carboxylic acids by hydrogen peroxide
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Oxidation of benzaldehyde to benzoic acid can be performed efficiently with 30% H2O2 as the oxidant and sulfonic acid resin Amberlyst 15 as the catalyst. The reactivities of benzaldehyde derivatives are determined by both hindrance effect and electron effect of substituents, and benzaldehyde derivatives with electron-withdrawing group at the meta- or para-position are highly active and almost quantitatively converted into their corresponding acids. In addition, this method also works well for the oxidation of aliphatic aldehydes. The key characteristic of the procedure is that the catalyst is recyclable.
- Yang, Xiaomei,Tang, Si,Lu, Tianliang,Chen, Chen,Zhou, Lipeng,Su, Yunlai,Xu, Jie
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p. 979 - 985
(2013/02/25)
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- Selective catalytic oxidation of alcohols, aldehydes, alkanes and alkenes employing manganese catalysts and hydrogen peroxide
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The manganese-containing catalytic system [MnIV,IV 2O3(tmtacn)2]2+ (1)/carboxylic acid (where tmtacn=N,N′,N′′-trimethyl-1,4,7-triazacyclononane), initially identified for the cis-dihydroxylation and epoxidation of alkenes, is applied for a wide range of oxidative transformations, including oxidation of alkanes, alcohols and aldehydes employing H2O2 as oxidant. The substrate classes examined include primary and secondary aliphatic and aromatic alcohols, aldehydes, and alkenes. The emphasis is not primarily on identifying optimum conditions for each individual substrate, but understanding the various factors that affect the reactivity of the Mn-tmtacn catalytic system and to explore which functional groups are oxidised preferentially. This catalytic system, of which the reactivity can be tuned by variation of the carboxylato ligands of the in situ formed [MnIII,III 2(O)(RCO2)2(tmtacn)2]2+ dimers, employs H2O2 in a highly atom efficient manner. In addition, several substrates containing more than one oxidation sensitive group could be oxidised selectively, in certain cases even in the absence of protecting groups. Copyright
- Saisaha, Pattama,Buettner, Lea,Van Der Meer, Margarethe,Hage, Ronald,Feringa, Ben L.,Browne, Wesley R.,De Boer, Johannes W.
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supporting information
p. 2591 - 2603
(2013/10/21)
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