- PHOTOCATALYTIC EFFECTS OF Fe(III) COMPOUNDS ON THE HYDROXYLATION OF BENZOIC ACID BY HYDROGEN PEROXIDE INITIATED BY 589 nm RADIATION AND SENSITIZED BY METHYLENE BLUE
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The hydroxylation of benzoic acid by hydrogen peroxide initiated by 589 nm radiation is catalyzed by the following Fe(III) compounds: FeCl3, K3, Na2, and K3.This photochemical reaction can be effectively sensitized by methylene blue.
- Lunak, Stanislav,Sedlak, Petr,Brodilova, Jirina,Lederer, Pavel
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- EVIDENCE FOR THE FORMATION OF 1,3- AND 1,4-DEHYDROBENZENES IN THE THERMAL DECOMPOSITION OF DIARYLIODONIUM-CARBOXYLATES
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Generation of m- and p-benzynes in decomposition of diaryliodonium- 3- and 4-carboxylates is demonstrated by three-phase method.
- Gavina, F.,Luis, S.V.,Safont, V.S.,Ferrer, P.,Costero, A.M.
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Read Online
- Efficiency of lithium cations in hydrolysis reactions of esters in aqueous tetrahydrofuran
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Lithium cations were observed to accelerate the hydrolysis of esters with hydroxides (KOH, NaOH, LiOH) in a water/tetrahydrofuran (THF) two-phase system. Yields in the hydrolysis of substituted benzoates and aliphatic esters using the various hydroxides were compared, and the effects of the addition of lithium salt were examined. Moreover, it was presumed that a certain amount of LiOH was dissolved in THF by the coordination of THF with lithium cation and hydrolyzed esters even in the THF layer, as in the reaction by a phase-transfer catalyst.
- Hayashi, Kazuhiko,Ichimaru, Yoshimi,Sugiura, Kirara,Maeda, Azusa,Harada, Yumi,Kojima, Yuki,Nakayama, Kanae,Imai, Masanori
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p. 581 - 594
(2021/06/06)
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- Cleavage of Carboxylic Esters by Aluminum and Iodine
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A one-pot procedure for deprotecting carboxylic esters under nonhydrolytic conditions is described. Typical alkyl carboxylates are readily deblocked to the carboxylic acids by the action of aluminum powder and iodine in anhydrous acetonitrile. Cleavage of lactones affords the corresponding ω-iodoalkylcarboxylic acids. Aryl acetylates undergo deacetylation with the participation of the neighboring group. This method enables the selective cleavage of alkyl carboxylic esters in the presence of aryl esters.
- Sang, Dayong,Yue, Huaxin,Fu, Yang,Tian, Juan
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p. 4254 - 4261
(2021/03/09)
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- Photocatalytic synthesis of phenols mediated by visible light using KI as catalyst
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A transition-metal-free hydroxylation of iodoarenes to afford substituted phenols is described. The reaction is promoted by KI under white LED light irradiation and uses atmospheric oxygen as oxidant. By the use of triethylamine as base and solvent, the corresponding phenols are obtained in moderate to good yields. Mechanistic studies suggest that KI and catalysis synergistically promote the cleavage of C-I bond to form free aryl radicals.
- Huiqin, Wei,Wu, Mei
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supporting information
(2021/11/30)
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- MOF-Zn-NHC as an efficient N-heterocyclic carbene catalyst for aerobic oxidation of aldehydes to their corresponding carboxylic acids: Via a cooperative geminal anomeric based oxidation
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As an efficient heterogenous N-heterocyclic carbene (NHC) catalyst, MOF-Zn-NHC was used in the aerobic oxidation of aryl aldehydes to their corresponding carbocyclic acids via an anomeric based oxidation. Features such as mild reaction conditions and no need for a co-catalyst or oxidative reagent can be considered as the major advantages of the presented method in this study. This journal is
- Babaee, Saeed,Zarei, Mahmoud,Zolfigol, Mohammad Ali
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p. 36230 - 36236
(2021/12/02)
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- Investigation of the requirements for efficient and selective cytochrome P450 monooxygenase catalysis across different reactions
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The cytochrome P450 metalloenzyme (CYP) CYP199A4 from Rhodopseudomonas palustris HaA2 catalyzes the highly efficient oxidation of para-substituted benzoic acids. Here we determined crystal structures of CYP199A4, and the binding and turnover parameters, with different meta-substituted benzoic acids in order to establish which criteria are important for efficient catalysis. When compared to the para isomers, the meta-substituted benzoic acids were less efficiently oxidized. For example, 3-formylbenzoic acid was oxidized with lower activity than the equivalent para isomer and 3-methoxybenzoic acid did not undergo O-demethylation by CYP199A4. The structural data highlighted that the meta-substituted benzoic acids bound in the enzyme active site in a modified position with incomplete loss of the distal water ligand of the heme moiety. However, for both sets of isomers the meta- or para-substituent pointed towards, and was in close proximity, to the heme iron. The absence of oxidation activity with 3-methoxybenzoic acid was assigned to the observation that the C[sbnd]H bonds of this molecule point away from the heme iron. In contrast, in the para isomer they are in an ideal location for abstraction. These findings were confirmed by using the bulkier 3-ethoxybenzoic acid as a substrate which removed the water ligand and reoriented the meta-substituent so that the methylene hydrogens pointed towards the heme, enabling more efficient oxidation. Overall we show relatively small changes in substrate structure and position in the active site can have a dramatic effect on the activity.
- Podgorski, Matthew N.,Coleman, Tom,Chao, Rebecca R.,De Voss, James J.,Bruning, John B.,Bell, Stephen G.
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- Copper and L-(?)-quebrachitol catalyzed hydroxylation and amination of aryl halides under air
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L-(?)-Quebrachitol, a natural product obtained from waste water of the rubber industry, was utilized as an efficient ligand for the copper-catalyzed hydroxylation and amination of aryl halides to selectively give phenols and aryl amines in water or 95percent ethanol. In addition, the hydroxylation of 2-chloro-4-hydroxybenzoic acid was validated on a 100-g scale under air.
- Bao, Xuefei,Chen, Guoliang,Dong, Jinhua,Du, Fangyu,Li, Hui,Liang, Xinjie,Wu, Ying,Zhang, Yongsheng
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supporting information
(2020/08/03)
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- Reductive dehalogenation and dehalogenative sulfonation of phenols and heteroaromatics with sodium sulfite in an aqueous medium
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Prototropic tautomerism was used as a tool for the reductive dehalogenation of (hetero)aryl bromides and iodides, or dehalogenative sulfonation of (hetero)aryl chlorides and fluorides, using sodium sulfite as the sole reagent in an aqueous medium. This protocol does not require a metal or phase transfer catalyst and avoids using organic solvent as the reaction medium. This method is especially suitable for substrates that readily tautomerize (such as 2-or 4-halogenated aminophenols and 4-halogenated resorcinols), for which dehalogenation or sulfonation proceeds under mild reaction conditions (≤60 °C). As sodium sulfite is an inexpensive, safe, and environmentally less hazardous reagent, this method has at least three potential applications: (i) in the deprotection of halogens as protecting groups, using sodium sulfite as a reducing agent; (ii) in the sulfonation of aromatic halides under mild reaction conditions avoiding hazardous and corrosive reagents/solvents; and (iii) in the transformation of toxic halogenated aromatics into less harmful compounds.
- Tomanová, Monika,Jedinák, Luká?,Canka?, Petr
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supporting information
p. 2621 - 2628
(2019/06/03)
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- Exploring the Selective Demethylation of Aryl Methyl Ethers with a Pseudomonas Rieske Monooxygenase
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Biocatalytic dealkylation of aryl methyl ethers is an attractive reaction for valorization of lignin components, as well as for deprotection of hydroxy functionalities in synthetic chemistry. We explored the demethylation of various aryl methyl ethers by using an oxidative demethylase from Pseudomonas sp. HR199. The Rieske monooxygenase VanA and its partner electron transfer protein VanB were recombinantly coexpressed in Escherichia coli and they constituted at least 25 % of the total protein content. Enzymatic transformations showed that VanB accepts NADH and NADPH as electron donors. The VanA–VanB system demethylates a number of aromatic substrates, the presence of a carboxylic acid moiety is essential, and the catalysis occurs selectively at the meta position to this carboxylic acid in the aromatic ring. The reaction is inhibited by the by-product formaldehyde. Therefore, we tested three different cascade/tandem reactions for cofactor regeneration and formaldehyde elimination; in particular, conversion was improved by addition of formaldehyde dehydrogenase and formate dehydrogenase. Finally, the biocatalyst was applied for the preparation of protocatechuic acid from vanillic acid, giving a 77 % yield of the desired product. The described reaction may find application in the conversion of lignin components into diverse hydroxyaromatic building blocks and generally offers potential for new, mild methods for efficient unmasking of phenols.
- Lanfranchi, Elisa,Trajkovi?, Milo?,Barta, Katalin,de Vries, Johannes G.,Janssen, Dick B.
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p. 118 - 125
(2019/01/04)
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- Application of quebrachitol in hydrolysis reaction of copper-catalyzed aryl halide
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The invention belongs to the technical field of drug synthesis, and provides application of quebrachitol in a hydrolysis reaction of a copper-catalyzed aryl halide. According to the hydrolysis reaction, copper serves as a catalyst, quebrachitol serves as a ligand, and the hydrolysis reaction is carried out on the aryl halide. The invention further provides a catalytic system of the hydrolysis reaction of the aryl halide. The reaction system comprises the copper catalyst, the quebrachitol, alkali and water, and the system is environmentally friendly and is suitable for industrial application.
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Paragraph 0075-0077
(2019/07/16)
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- C70 Fullerene-Catalyzed Metal-Free Photocatalytic ipso-Hydroxylation of Aryl Boronic Acids: Synthesis of Phenols
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A metal-free C70 fullerene-catalyzed method has been developed for the ipso-hydroxylation of aryl and heteroaryl boronic acids to corresponding phenols under photocatalytic conditions. The reaction proceeds under oxygen atmosphere and the mechanistic study revealed that C70 plays a critical role in the generation of reactive oxygen species in the presence of blue light. Reactions in the presence of 18O-labelled water and oxygen confirmed the generation of reactive oxygen species from oxygen molecule. Amine used as a reductant could be recovered in the form of imine. The current method is also applicable to the synthesis of aryl ethers in one-pot two-step process. (Figure presented.).
- Kumar, Inder,Sharma, Ritika,Kumar, Rakesh,Kumar, Rakesh,Sharma, Upendra
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supporting information
p. 2013 - 2019
(2018/04/02)
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- Chemoselective ester/ether C–O cleavage of methyl anisates by aluminum triiodide
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The aluminum triiodide mediated chemoselective ester/ether C–O cleavage of methyl anisates was investigated. o-Anisate undergoes ether cleavage at low temperatures in carbon disulfide, cyclohexane and acetonitrile. Further cleavage of the ester group occurs at elevated temperatures to afford salicylic acid. The cleavage of p-anisate is solvent-dependent. In cyclohexane, the ester and ether groups were cleaved non-selectively to give equimolar amounts of p-anisic acid and methyl p-hydroxybenzoate. The ester group was preferentially cleaved in acetonitrile, compared to ether group cleavage in carbon disulfide. The ester cleavage reaction was improved using pyridine as an acid scavenger additive. Reasons for the contrasting reactivity of anisates towards AlI3 were explored, and the methods were applied to cleavage of the tert-butyl ester of acemetacin which gave different products under these conditions.
- Sang, Dayong,Yi, Cuicui,He, Zhoujun,Wang, Jiahui,Tian, Juan,Yao, Ming,Shi, Hong
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supporting information
p. 1469 - 1472
(2018/03/13)
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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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- Method for synthesizing m-hydroxybenzoic acid from m-cresol through catalytic oxidation
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A method for synthesizing m-hydroxybenzoic acid from m-cresol through catalytic oxidation comprises: purifying industrial phenol-containing waste water to obtain crude phenol, performing rectificationto obtain m-cresol, and adding a mixed catalyst for catalysis. The mixed catalyst is a mixture of a catalyst which is made by loading a complex prepared by coordinating salt of four metals includingvanadium, nickel, cobalt and copper with an imidazoles compound on a molecular sieve and a dibutyltin dilaurate catalyst. The method is eco-friendly and efficient, is improved in reaction yield, reduced in reaction pressure and reaction time, and improved in production economy.
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Paragraph 0022; 0023; 0028; 0029; 0030; 0031
(2018/06/14)
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- Aqueous Oxidations Started by TiO2 Photoinduced Holes Can Be a Rate-Determining Step
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In aqueous TiO2 photocatalytic hydroxylation of weakly polar aromatics, a series of inverse H/D KIEs of 0.7–0.8 were observed, which is different than the normal H/D kinetic isotope effects (KIEs) usually observed for polar aromatics. This result indicated that the oxidation started by photo-induced hvb + can be the rate-determining step.
- Gong, Yuanzheng,Yang, Chun,Ji, Hongwei,Chen, Chuncheng,Ma, Wanhong,Zhao, Jincai
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supporting information
p. 2048 - 2051
(2017/08/23)
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- Selective oxidation of aliphatic C-H bonds in alkylphenols by a chemomimetic biocatalytic system
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Selective oxidation of aliphatic C-H bonds in alkylphenols serves significant roles not only in generation of functionalized intermediates that can be used to synthesize diverse downstream chemical products, but also in biological degradation of these environmentally hazardous compounds. Chemo-, regio-, and stereoselectivity; controllability; and environmental impact represent the major challenges for chemical oxidation of alkylphenols. Here, we report the development of a unique chemomimetic biocatalytic system originated from the Gram-positive bacterium Corynebacterium glutamicum. The system consisting of CreHI (for installation of a phosphate directing/ anchoring group), CreJEF/CreG/CreC (for oxidation of alkylphenols), and CreD (for directing/anchoring group offloading) is able to selectively oxidize the aliphatic C-H bonds of p-And m-Alkylated phenols in a controllable manner. Moreover, the crystal structures of the central P450 biocatalyst CreJ in complex with two representative substrates provide significant structural insights into its substrate flexibility and reaction selectivity.
- Du, Lei,Dong, Sheng,Zhang, Xingwang,Jiang, Chengying,Chen, Jingfei,Yao, Lishan,Wang, Xiao,Wan, Xiaobo,Liu, Xi,Wangi, Xinquan,Huang, Shaohua,Cui, Qiu,Feng, Yingang,Liu, Shuang-Jiang,Li, Shengying
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p. E5129 - E5137
(2017/07/04)
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- METHOD FOR SYNTHESIZING PHENOL USING METAL CATALYST
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The present invention relates to a method for synthesizing phenol using a metal catalyst and, more specifically, to a method for preparing phenol, which is a product of cross-coupling reaction by performing reaction of aryl halide and 2-dimethylaminoethanol in the presence of a metal catalyst. According to the present invention, phenol, as a product of cross-coupling reaction by performing reaction of aryl halide and 2-dimethylaminoethanol in the presence of a metal catalyst, can be synthesized with high yield. Also, various phenols having substituents can be synthesized.COPYRIGHT KIPO 2017
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Paragraph 0058; 0060
(2017/10/26)
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- METHOD TO PREPARE PHENOLICS FROM BIOMASS
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The present invention is directed to a method for preparing a final phenolic product from biomass comprising the steps of providing a furanic compound obtainable from biomass; reacting the furanic compound with a dienophile to obtain a phenolic compound; reacting the phenolic compound further to obtain the final phenolic product.
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Page/Page column 47
(2016/08/10)
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- Nanocomposites with different metals as magnetically separable nanocatalysts for oxidation of aldehydes
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In this study, two metals were chosen for composing two different nanocatalysts. Zinc acetate and nickel chloride were used to prepare two nanocatalysts from acetanilide anchored to functionalized silica-coated Fe3O4 magnetic nanoparticles. They were identified using scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and gas chromatography–mass spectrometry. These nanocatalysts were used for the oxidation of the following aldehydes: 3-hydroxybenzaldehyde, 4-methoxybenzaldehyde, and 3-nitrobenzaldehyde. High efficiency, stability, recoverability, recyclability, and selectivity were achieved using these nanocatalysts.
- Esmaeili, Akbar,Kakavand, Sahar
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p. 936 - 941
(2016/08/08)
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- Hydrolysis of diazonium salts using a two-phase system (CPME and water)
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A new method for the hydrolysis of diazonium salts, without the formation of tar, was developed. A two-phase system consisting of cyclopentyl methyl ether (CPME) and water is very effective for the hydrolysis of diazonium salts. Using this solvent system, the diazonium salt prepared from 3-(4-nitrophenoxy)aniline gave 3-(4-nitrophenoxy)phenol in high yield (96%) within 20 min. The synthesized phenol is an industrially important raw material in polymer syntheses. Furthermore, the use of the present two-phase system of CPME and water successfully brought about the efficient conversions of several m-substituted anilines into the corresponding m-substituted phenols. This is the first example of hydrolysis of diazonium salts using the two-phase system (CPME and water).
- Taniguchi, Toshihide,Imoto, Mitsutaka,Takeda, Motonori,Nakai, Takeo,Mihara, Masatoshi,Iwai, Toshiyuki,Ito, Takatoshi,Mizuno, Takumi,Nomoto, Akihiro,Ogawa, Akiya
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p. 411 - 416
(2018/01/18)
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- Chorismatase Mechanisms Reveal Fundamentally Different Types of Reaction in a Single Conserved Protein Fold
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Chorismatases are a class of chorismate-converting enzymes involved in the biosynthetic pathways of different natural products, many of them with interesting pharmaceutical characteristics. So far, three subfamilies of chorismatases are described that convert chorismate into different (dihydro-)benzoate derivatives (CH-FkbO, CH-Hyg5, and CH-XanB2). Until now, the detailed enzyme mechanism and the molecular basis for the different reaction products were unknown. Here we show that the CH-FkbO and CH-Hyg5 subfamilies share the same protein fold, but employ fundamentally different reaction mechanisms. While the FkbO reaction is a typical hydrolysis, the Hyg5 reaction proceeds intramolecularly, most likely via an arene oxide intermediate. Two nonconserved active site residues were identified that are responsible for the different reaction mechanisms in CH-FkbO and CH-Hyg5. Further, we propose an additional amino acid residue to be responsible for the discrimination of the CH-XanB2 subfamily, which catalyzes the formation of two different hydroxybenzoate regioisomers, likely in a single active site. A multiple sequence alignment shows that these three crucial amino acid positions are located in conserved motifs and can therefore be used to assign unknown chorismatases to the corresponding subfamily. (Chemical Equation Presented).
- Hubrich, Florian,Juneja, Puneet,Müller, Michael,Diederichs, Kay,Welte, Wolfram,Andexer, Jennifer N.
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supporting information
p. 11032 - 11037
(2015/09/15)
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- METHOD OF PRODUCING BENZOIC ACID
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PROBLEM TO BE SOLVED: To provide a novel synthesis method in the production of a benzoic acid, which is an important compound for the synthesis of an organic compound, and an industrially suitable production method using main materials derived from nonfossil resources. SOLUTION: This invention provides a method of producing a benzoic acid with a substituted hydroxyl group, methoxy group, or acetoxy group, comprising the step of the ozonation of a compound represented by formula (I), where R1 is H, a methyl group or an acetyl group; R2 is H or an acetoxy group; R3 is an alkyl group, a carboxy group, a formyl group, an alkoxycarbonyl group, an amide group, an acid chloride group, a halogenation alkyl group, or a hydroxyalkyl group. COPYRIGHT: (C)2015,JPOandINPIT
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- Ring Opening of Bicyclo[3.1.0]hexan-2-ones: A Versatile Synthetic Platform for the Construction of Substituted Benzoates
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Described is the development of a highly efficient 2πdisrotatory ring-opening aromatization sequence using bicyclo[3.1.0]hexan-2-ones. This unprecedented transformation efficiently proceeds under thermal conditions and allows facile construction of uniquely substituted and polyfunctionalized benzoates. In the presence of either amines or alcohols formation of substituted anilines or ethers, respectively, is achieved. Additionally, the utility of this method was demonstrated in a short synthesis of sekikaic acid methyl ester. Cracked open: A highly efficient thermal 2πdisrotatory ring-opening aromatization sequence of bicyclo[3.1.0]hexan-2-ones is described. The transformation proceeds in sulfolane to give uniquely substituted benzoates. In the presence of either amines or alcohols, formation of substituted anilines or ethers, respectively, is achieved.
- Feierfeil, Johannes,Grossmann, Adriana,Magauer, Thomas
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supporting information
p. 11835 - 11838
(2015/10/05)
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- Copper and l-sodium ascorbate catalyzed hydroxylation and aryloxylation of aryl halides
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CuSO4·5H2O and NaAsc catalyzed hydroxylation and C-O/C-S cross-coupling reactions of aryl halides with phenols or 4-methylbenzenethiol were described. A wide range of substrates and test cases highlight the synthetic utility of the approach. A series of phenols, diaryl ethers, alkylaryl ethers, and diaryl thioethers were synthesized in high yield.
- Song, Guang-Lin,Zhang, Zhang,Da, Yu-Xia,Wang, Xi-Cun
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p. 8823 - 8829
(2015/10/20)
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- Reaction of 1,2-difunctionalized ethanes with aryl iodides in copper-catalyzed cross-coupling: Application to synthesis of phenols
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A series of 1,2-difunctionalized ethanes, such as ethylene glycol, 2-aminoethanol, 1,2-diaminoethane, 2-dimethylaminoethanol N',N'-dimethylethane-1,2-diamine, were investigated to test the reactivity with aryl iodides in the presence of copper catalysts. Under the reaction conditions, they produce the various Cheteroatom cross-coupled products. Interestingly, ethylene glycol and 2-dimethylaminoethanol afforded mainly the phenolic compounds while the others produced different cross-coupled products. Although ethylene glycol and 2-dimethylaminoethanol resulted in the same product, their behaviors in the reaction were quite different: ethylene glycol appears to mostly act as the ligand and 2-dimethylaminoethanol appears to serve as both the ligand and reactant. This finding led to a copper-catalyzed synthesis of phenols using either ethylene glycol or 2-dimethylaminoethanol, which can be applied to a variety of aryl iodides, providing an alternative synthetic route to phenols.
- Kim, Jihye,Battsengel, Oyunsaikhan,Liu, Yajun,Chae, Junghyun
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supporting information
p. 2833 - 2840
(2016/02/05)
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- Purification, characterization and in-silico analysis of nitrilase from Gordonia terrae
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An inducible and aromatic nitrilase from Gordonia terrae was purified with a yield of 19%. The enzyme had turnover number of 63 s-1 × 10-3, Km1.4 mM and Vmax95 Umg-1 protein for benzonitrile. The nitrilase of G. terrae was active at basic pH (7-10), moderate temperature (20-45 °C) and has a half-life of 4 h at 35 °C. MALDI analysis and amino acid sequence deduced from cloned nucleotide fragment showed 97% homology with putative amidohydrolase of Gordonia sputi NBRC 100414 and G. namibiensis. The enzyme showed regioselectivity towards hydroxybenzonitriles, as different position of hydroxyl group i.e. meta-, para- and orthosubstitutions on benzonitrile effect enzyme activity. The in-silico interactions of these substrates with the predicted 3D model of this enzyme also showed differential interaction between hydroxyl group of substrates and the polar amino acids surrounding enzyme's active site. This leads to different proximity and orientation of substrates vis-a-vis their interaction with catalytic residues.
- Kumar, Vijay,Seth, Amit,Kumari, Vijaya,Kumar, Virender,Bhalla, Tek C.
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- Enhancement of the advanced Fenton process by weak magnetic field for the degradation of 4-nitrophenol
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A weak magnetic field (WMF) was employed to enhance the degradation of 4-nitrophenol (4-NP) by the advanced Fenton process (Fe0/H2O2) in this study. Although the oxidation rates of 4-NP by Fe0/H2O2 and WMF-Fe0/H2O2 dropped sharply upon increasing the initial pH (pHini), the introduction of WMF could remarkably improve the 4-NP degradation by Fe0/H2O2 at pHini ranging from 3.0 to 6.0. The quenching and electron paramagnetic resonance experiments verified that the hydroxyl radical was the primary oxidant responsible for the 4-NP degradation at pHini 4.0 and the cumulative concentration of HO in the WMF-Fe0/H2O2 system was about 3-fold that in Fe0/H2O2 system. The superimposed WMF increased the generation of HO in the Fe0/H2O2 process by accelerating the Fe0 corrosion and FeII generation, which was the limiting step of the Fe0/H2O2 process. The application of WMF largely enhanced the mineralization of 4-NP but it did not change the 4-NP degradation pathways, which were proposed based on the degradation products detected with LC-MS/MS. The optimum intensity of the magnetic field for 4-NP oxidation by WMF-Fe0/H2O2 was determined to be 20 mT. Response surface methodology (RSM) was applied to analyze the experimental variables and it was found that lower pH and higher Fe0 and H2O2 dosages were beneficial for 4-NP degradation by WMF-Fe0/H2O2. Among the three factors (pHini, Fe0 dosage, and H2O2 dosage) investigated, pHini was the most important factor affecting the performance of the WMF-Fe0/H2O2 process. The WMF-Fe0/H2O2 technology provides a new alternative for scientists working in the field of water treatment. This journal is
- Xiong, Xinmei,Sun, Yuankui,Sun, Bo,Song, Weihua,Sun, Jingyi,Gao, Naiyun,Qiao, Junlian,Guan, Xiaohong
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p. 13357 - 13365
(2015/02/19)
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- Direct hydroxylation of arenes with O2 catalyzed by V@CN catalyst
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A vanadium doped graphitic carbon nitride catalyst has been prepared and used for the direct hydroxylation of arenes with O2. Substituted arenes with electron-withdrawing groups such as CN, NO2, COOH, CF3, and COCH3 were oxygenated to the corresponding phenols in moderate yields. The catalyst also proved applicable for the hydroxylation of aromatic halides (F, Cl, and Br) with O2.
- Li, Yan,Li, Bing,Chen, Ting,Zhou, Zhicheng,Wang, Jun,Huang, Jun
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p. 1086 - 1092
(2015/07/01)
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- The Hydroxylation of Aromatics with Oxygen by Vanadium Catalysts Supported on N-doped Carbon Materials
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Vanadium catalysts supported on N-doped carbon materials (CN) were prepared and the catalyst VOSiW showed high activity for the hydroxylation of various aromatics with O2. Aromatics with electron-withdrawing groups such as CN, NO2, COOH, CF3, COCH3 and aromatic halides (F, Cl and Br) were oxygenated to the corresponding phenols in considerable yields. The CN materials were not only indispensable for the reusability of the vanadium catalyst VOSiW, but also favorable to the high catalytic activity. The VOSiW catalyst is ready for the hydroxylation of aromatics with O2 as both V4+ and V5+ species are coexisted in the VOSiW catalyst.
- Li, Yan,Li, Bing,Geng, Longfei,Wang, Jun,Wang, Yong,Huang, Jun
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p. 1014 - 1021
(2015/08/04)
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- A novel sustainable strategy for the synthesis of phenols by magnetic CuFe2O4-catalyzed oxidative hydroxylation of arylboronic acids under mild conditions in water
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A novel sustainable strategy for the synthesis of phenols has been developed using inexpensive, readily available, air-stable, and recyclable CuFe2O4 nanoparticles as the catalyst, and the corresponding substituted phenols were obtained in moderate to good yields by oxidative hydroxylation of arylboronic acids in water. Importantly, a ligand or an additive was not necessary. The catalyst was completely recoverable with an external magnet and could be reused six times without significant loss of catalytic activity.
- Yang, Daoshan,An, Baojuan,Wei, Wei,Jiang, Min,You, Jinmao,Wang, Hua
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supporting information
p. 3630 - 3634
(2014/05/20)
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- Metal-free UV-Vis-light-induced aerobic oxidative hydroxylation of arylboronic acids in the absence of a photosensitizer
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A simple and efficient method has been developed for the metal-free photosynthesis of phenols with UV-Vis (ultraviolet-visible) light in quartz tubes. The protocol uses readily available arylboronic acids as the starting materials, triethylamine as the sacrificial electron donor, and air as the oxidant. The method shows high efficiency, environmental friendliness and mild reaction conditions, without the addition of a photosensitizer. This journal is the Partner Organisations 2014.
- Jiang, Min,Li, Yong,Yang, Haijun,Zong, Ruilong,Jin, Yunhe,Fu, Hua
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p. 12977 - 12980
(2014/04/03)
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- Copper-catalyzed synthesis of aromatic carboxylic acids from arylboronic acids and acetyl acetate
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A simple and efficient copper-catalyzed method for the synthesis of aromatic carboxylic acids in moderate to high yields with great functional-group compatibility in the substrates has been developed. The new method uses readily available arylboronic acids and acetyl acetate as the starting materials and inexpensive CuI as the catalyst.
- Zheng, Rui,Zhou, Qizhong,Gu, Haining,Jiang, Huajiang,Wu, Jiashou,Jin, Zhengneng,Han, Deman,Dai, Guoliang,Chen, Rener
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supporting information
p. 5671 - 5675
(2014/12/11)
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- Metal-free synthesis of substituted phenols from arylboronic acids in water at room temperature
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A convenient, efficient and practical metal-free method for the synthesis of substituted phenols from arylboronic acids has been developed. The protocol uses hydrogen peroxide as a hydroxylating agent, ammonium bicarbonate as an additive, and the reactions were conveniently performed in water at room temperature. The method shows an excellent tolerance of functional groups, so it will find a wide variety of applications in academic and industrial research.
- Jiang, Min,Yang, Hai-Jun,Li, Yong,Jia, Zhi-Ying,Fu, Hua
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supporting information
p. 715 - 719
(2014/06/09)
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- Inclusion complex containing epoxy resin composition for semiconductor encapsulation
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The invention is an epoxy resin composition for sealing a semiconductor, including (A) an epoxy resin and (B) a clathrate complex. The clathrate complex is one of (b1) an aromatic carboxylic acid compound, and (b2) at least one imidazole compound represented by formula (II): wherein R2 represents a hydrogen atom, C1-C10 alkyl group, phenyl group, benzyl group or cyanoethyl group, and R3 to R5 represent a hydrogen atom, nitro group, halogen atom, C1-C20 alkyl group, phenyl group, benzyl group, hydroxymethyl group or C1-C20 acyl group. The composition has improved storage stability, retains flowability when sealing, and achieves an effective curing rate applicable for sealing delicate semiconductors.
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- Electrophilicity and nucleophilicity of commonly used aldehydes
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The present approach for determining the electrophilicity (E) and nucleophilicity (N) of aldehydes includes a kinetic study of KMNO4 oxidation and NaBH4 reduction of aldehydes. A transition state analysis of the KMNO4 promoted aldehyde oxidation reaction has been performed, which shows a very good correlation with experimental results. The validity of the experimental method has been tested using the experimental activation parameters of the two reactions. The utility of the present approach is further demonstrated by the theoretical versus experimental relationship, which provides easy access to E and N values for various aldehydes and offers an at-a-glance assessment of the chemical reactivity of aldehydes in various reactions. the Partner Organisations 2014.
- Pratihar, Sanjay
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p. 5781 - 5788
(2014/07/22)
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- Diaryl-1,2,4-oxadiazole antioxidants: Synthesis and properties of inhibiting the oxidation of DNA and scavenging radicals
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Six 1,2,4-oxadiazole derivatives were prepared in order to compare their abilities to protect DNA against radical-mediated oxidation and to scavenge radicals. These derivatives had a structure based on disubstituted 1,2,4-oxadiazole, in which a vanillin group (A ring) and a substituted benzene group (B ring) were the substituents. The functional group at B ring was assigned as ortho- or meta-hydroxylbenzene group, ortho-chlorobenzene group, no group contained, and pyridine group or vanillin group at B ring. It was found that the compound with two vanillin groups attaching to oxadiazole can trap 2.05 radicals in protecting DNA against 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation, and the compound with an ortho-hydroxylbenzene group at B ring can trap 1.78 radicals. The compound with an ortho-chlorobenzene group at B ring exhibited the highest ability to inhibit ·OH-induced oxidation of DNA, while the compound with a meta-hydroxylbenzene group at B ring inhibited Cu2+/glutathione (GSH)-induced oxidation of DNA efficiently. The ortho- and para-hydroxylbenzene groups at B ring made the compounds possess the highest rate constant (k) in scavenging 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+.) and 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH). Therefore, only a few hydroxyl groups can markedly enhance the activity of the core-branched antioxidant, which may be a novel structural feature in designing antioxidant.
- Zhao, Chao,Liu, Zai-Qun
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p. 842 - 849
(2013/04/24)
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- An efficient single-enzymatic cascade for asymmetric synthesis of chiral amines catalyzed by ω-transaminase
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An efficient single-enzymatic cascade approach for the asymmetric synthesis of chiral amines has been developed, which applies the amino donor 3-aminocyclohexa-1,5-dienecarboxylic acid spontaneously tautomerizing to reach reaction completion with excellen
- Wang, Bo,Land, Henrik,Berglund, Per
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supporting information
p. 161 - 163
(2013/02/23)
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- Copper(II)-catalyzed hydroxylation of aryl halides using glycolic acid as a ligand
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Copper(II)-catalyzed hydroxylation of aryl halides has been developed to afford functionalized phenols. The protocol utilizes the reagent combination of Cu(OH)2, glycolic acid, and NaOH in aqueous DMSO, all of which are cheap, readily available, and easily removable after the reaction. A broad range of aryl iodides and activated aryl bromides were transformed into the corresponding phenols in excellent yields. Moreover, it has been shown that C-O(alkyl)-coupled product, instead of phenol, can be predominantly formed under similar reaction conditions.
- Xiao, Yan,Xu, Yongnan,Cheon, Hwan-Sung,Chae, Junghyun
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p. 5804 - 5809
(2013/07/25)
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- Exploring the reactivity of multicomponent photocatalysts: Insight into the complex valence band of BiOBr
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The band structure of multicomponent semiconductor photocatalysts, as well as their reactivity distinction under different wavelengths of light, is still unclear. BiOBr, which is a typical multicomponent semiconductor, may have two possible valence-band structures, that is, two discrete valence bands constructed respectively from O 2p and Br 4p orbitals, or one valence band derived from the hybridization of these orbitals. In this work, aqueous photocatalytic hydroxylation is applied as the probe reaction to investigate the nature and reactions of photogenerated holes in BiOBr. Three organic compounds (microcystin-LR, aniline, and benzoic acid) with different oxidation potentials were selected as substrates. Isotope labeling (H218O as the solvent) was used to determine the source of the O atom in the hydroxyl group of the products, which distinguishes the contribution of different hydroxylation pathways. Furthermore, a spin-trapping ESR method was used to quantify the reactive oxygen species (.OH and .OOH) formed in the reaction system. The different isotope abundances of the hydroxyl O atom of the products formed, as well as the reverse trend of the .OH/.OOH ratio with the oxidative resistance of the substrate under UV and visible irradiation, reveal that BiOBr has two separate valence bands, which have different oxidation ability and respond to UV and visible light, respectively. This study shows that the band structure of semiconductor photocatalysts can be reliably analyzed with an isotope labeling method. Which isotope won? Hydroxylation in the BiOBr photocatalytic system with H218O solvent and 16O2 oxidant gives products with different isotope profiles under visible-light versus UV irradiation (see scheme). The isotope abundance is also affected by the oxidative resistance of the substrate. Together with the .OH/ .OOH ratio, the results show that BiOBr has two valence bands that have different oxidation abilities and responses to UV and visible light. Copyright
- Fang, Yan-Fen,Ma, Wan-Hong,Huang, Ying-Ping,Cheng, Gen-Wei
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p. 3224 - 3229
(2013/03/29)
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- Rescuing auxotrophic microorganisms with nonenzymatic chemistry
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Organic chemistry to the rescue: Two unrelated nonenzymatic chemical reactions can support the growth of auxotrophic E.-coli strains by generating essential nutrients in-situ. These biocompatible reactions, which take place in the presence of the organisms and are designed to interface with cellular metabolic processes, provide a means of linking the growth of an organism to the success of a nonbiological chemical transformation. Copyright
- Lee, Yunmi,Umeano, Afoma,Balskus, Emily P.
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supporting information
p. 11800 - 11803
(2013/11/19)
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- NHC-catalysed highly selective aerobic oxidation of nonactivated aldehydes
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This publication describes a highly selective oxidation of aldehydes to the corresponding acids or esters. The reaction proceeds under metal-free conditions by using N-heterocyclic carbenes as organocatalysts in combination with environmentally friendly oxygen as the terminal oxidation agent.
- Moehlmann, Lennart,Ludwig, Stefan,Blechert, Siegfried
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p. 602 - 607
(2013/04/24)
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- Kinetics and stereochemistry of hydrolysis of an N-(phenylacetyl)-α- hydroxyglycine ester catalyzed by serine β-lactamases and dd-peptidases
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The α-hydroxydepsipeptide 3-carboxyphenyl N-(phenylacetyl)-α- hydroxyglycinate (5) is a quite effective substrate of serine β-lactamases and low molecular mass dd-peptidases. The class C P99 and ampC β-lactamases catalyze the hydrolysis of both enantiomers of 5, although they show a strong preference for one of them. The class A TEM-2 and class D OXA-1 β-lactamases and the Streptomyces R61 and Actinomadura R39 dd-peptidases catalyze hydrolysis of only one enantiomer of 5 at any significant rate. Experiments show that all of the above enzymes strongly prefer the same enantiomer, a surprising result since β-lactamases usually prefer l(S) enantiomers and dd-peptidases d(R). Product analysis, employing peptidylglycine α-amidating lyase, showed that the preferred enantiomer is d(R). Thus, it is the β-lactamases that have switched preference rather than the dd-peptidases. Molecular modeling of the P99 β-lactamase active site suggests that the α-hydroxyl of 5 may interact with conserved Asn and Lys residues. Both α-hydroxy and α-amido substituents on a glycine ester substrate can therefore enhance its productive interaction with the β-lactamase active site, although their effects are not additive; this may also be true for inhibitors.
- Pelto, Ryan B.,Pratt
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experimental part
p. 7356 - 7362
(2012/10/08)
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- Selective oxidation of phenol and benzoic acid in water via home-prepared TiO2 photocatalysts: Distribution of hydroxylation products
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The hydroxylation of phenol (a substrate containing an electron donor group) and of benzoic acid (a substrate containing an electron withdrawing group) has been carried out by the photocatalytic method in aqueous suspensions containing commercial or home prepared TiO2 samples. The aim of the work was to study the distribution of hydroxylation products when different photocatalysts were used and to correlate the selectivity to some physico-chemical features of the powders. The samples were characterized by X-ray diffraction, thermogravimetry, determination of crystalline phase percentage, specific surface area and zero charge point. The photoreactivity results indicate that the products of the primary oxidation of phenol are the ortho- and para-mono-hydroxy derivatives while those of benzoic acid are all the mono-hydroxy derivatives independently of the catalyst. The selectivity toward mono-hydroxy derivatives shows a strong dependence on catalyst hydroxylation and crystallinity degrees: the highest selectivity values were obtained by using the commercial samples that resulted the least hydroxylated and the most crystalline ones. A kinetic model, taking into account the mineralization and the partial oxidation reaction routes, is proposed by using the Langmuir-Hinshelwood model.
- Bellardita, Marianna,Augugliaro, Vincenzo,Loddo, Vittorio,Megna, Bartolomeo,Palmisano, Giovanni,Palmisano, Leonardo,Puma, Maria Angela
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- Green catalysts derived from agricultural and industrial waste products: The preparation of phenols from CsOH and Aryl iodides using CuO on mesoporous silica
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The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. The synthesis of CuO catalysts supported on mesoporous silica derived from rice husks and semiconductor copper from chemical mechanical planarization (Cu-CMP) wastewater is described. These catalysts are active for the coupling reaction of CsOH with aryl iodides. Low catalyst loading (1 mol-%) without the need for ancillary ligands make these very attractive "green" catalysts. Copyright
- Chan, Chien-Ching,Chen, Yan-Wun,Su, Chi-Shen,Lin, Hong-Ping,Lee, Chin-Fa
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experimental part
p. 7288 - 7293
(2012/01/06)
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- Simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide
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This work reports a simple and efficient CuI/PEG-400 system for hydroxylation of aryl halides with potassium hydroxide. This protocol offers a direct transformation of aryl iodides or bromides to substituted phenols in great diversity. A very wide variety of functional groups are tolerated on aryl halides partners such as carboxyl, aldehyde and hydroxyl group.
- Chen, Junmin,Yuan, Tangjun,Hao, Wenyan,Cai, Mingzhong
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experimental part
p. 1463 - 1465
(2012/06/18)
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- CuI-catalyzed hydroxylation of aryl bromides under the assistance of 5-bromo-2-(1H-imidazol-2-yl)pyridine and related ligands
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A number of substituted 2-pyridin-2-yl-1H-benzoimidazoles and 2-(1H-imidazol-2-yl)pyridines were screened for promoting CuI-catalyzed hydroxylation of aryl bromides, which led to the discovery of the combination of CuI and 5-bromo-2-(1H-imidazol-2-yl)pyridine as an effective catalytic system for this transformation. Both electron-rich and electronic-deficient aryl bromides could be converted into the corresponding substituted phenols in good to excellent yields.
- Jia, Jianhuan,Jiang, Chenglin,Zhang, Xiaojing,Jiang, Yongwen,Ma, Dawei
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supporting information; experimental part
p. 5593 - 5595
(2011/11/06)
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- Serendipitous discovery of α-hydroxyalkyl esters as β-lactamase substrates
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O-(1-Carboxy-1-alkyloxycarbonyl) hydroxamates were found to spontaneously decarboxylate in aqueous neutral buffer to form O-(2-hydroxyalkylcarbonyl) hydroxamates. While the former molecules do not react rapidly with serine β-lactamases, the latter are quite good substrates of representative class A and C, but not D, enzymes, and particularly of a class C enzyme. The enzymes catalyze hydrolysis of these compounds to a mixture of the α-hydroxy acid and hydroxamate. Analogous compounds containing aryloxy leaving groups rather that hydroxamates are also substrates. Structure-activity experiments showed that the α-hydroxyl group was required for any substantial substrate activity. Although both d- and l-α-hydroxy acid derivatives were substrates, the former were preferred. The response of the class C activity to pH and to alternative nucleophiles (methanol and d-phenylalanine) suggested that the same active site functional groups participated in catalysis as for classical substrates. Molecular modeling was employed to explore how the α-hydroxy group might interact with the class C β-lactamase active site. Incorporation of the α-hydroxyalkyl moiety into novel inhibitors will be of considerable interest.
- Pelto, Ryan B.,Pratt
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experimental part
p. 10496 - 10506
(2011/10/18)
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- METHOD FOR THE SYNTHESIS OF (Z)-3-[2-BUTOXY-3'-(3-HEPTYL-1-METHYL-UREIDO)-BIPHENYL-4-YL]-2-METHOXY-ACRYLIC ACID
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The invention relates to a process for the synthesis of (Z)-3-[2-butoxy-3′-(3-heptyl-1-methylureido)biphenyl-4-yl]-2-methoxyacrylic acid of formula (I): and also to the process for the synthesis of the reaction intermediates of general formula (XII), and to the said compounds when R2 is chosen from the methyl, trifluoromethyl, phenyl and 4-tolyl radicals:
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Page/Page column title page; 1
(2010/12/29)
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- Substituted aryl malonamates as new serine β-lactamase substrates: Structure-activity studies
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A series of substituted aryl malonamates have been prepared. These compounds are analogues of aryl phenaceturates where the amido side chain has been replaced by a retro-amide. Like the phenaceturates, these compounds are substrates of typical class A and class C β-lactamases, particularly of the latter, and of soluble DD-peptidases. The effect of substituents α to the ester carbonyl group on turnover by these enzymes is similar to that in the phenaceturates. On the other hand, N-alkylation of the side chain amide of malonamates, but not of phenaceturates, retains the susceptibility of the compounds to hydrolysis by β-lactamases. This reactivity is not enhanced, however, by bridging the amide nitrogen and Cα atoms. A phosphonate analogue of the malonamates was found to be an irreversible inhibitor of the β-lactamases. These results, therefore, provide further evidence for the covalent access of compounds bearing retro-amide side chains to the active sites of β-lactam-recognizing enzymes.
- Adediran,Cabaret,Lohier,Wakselman,Pratt
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experimental part
p. 282 - 291
(2010/04/05)
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- An efficient synthesis of phenol via CuI/8-hydroxyquinoline-catalyzed hydroxylation of aryl halides and potassium hydroxide
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The CuI/8-hydroxyquinoline-catalyzed direct hydroxylation of aryl iodides with KOH takes place at 100 C in a mixed solvent system (t-BuOH-DMSO-H 2O), providing the corresponding phenols in great diversity. Aryl bromides are found to be rather less reactive under these reaction conditions. Georg Thieme Verlag Stuttgart - New York.
- Maurer, Stefan,Liu, Wei,Zhang, Xiaojing,Jiang, Yongwen,Ma, Dawei
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supporting information; experimental part
p. 976 - 978
(2010/07/10)
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- A simple and practical copper-catalyzed approach to substituted phenols from aryl halides by using water as the solvent
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Water surprise! A simple and practical copper-catalyzed approach to substituted phenols by hydroxylation of aryl halides has been developed by using environmentally benign water as the solvent (see scheme). The method proceeds under mild conditions and is tolerant towards various functional groups in the substrates.
- Yang, Daoshan,Fu, Hua
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supporting information; experimental part
p. 2366 - 2370
(2010/06/15)
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