- Remarkable effect of lithium salts in Friedel-Crafts acylation of 2-methoxynaphthalene catalyzed by metal triflates
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In the presence of a catalytic amount of a metal triflate such as Sb(OTf)3 or Ga(OTf)3, 2-methoxynaphthalene reacted with acetic anhydride in nitromethane-lithium perchlorate to afford 2-acetyl-6-methoxynaphthalene, a well-known intermediate for the synthesis of naproxen, in a high yield. (C) 2000 Elsevier Science Ltd.
- Kobayashi,Komoto
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- Enhancement in activity and shape selectivity of zeolite BEA by phosphate treatment for 2-methoxynaphthalene acylation
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Pore-engineering of large pores of zeolite BEA by phosphate treatment effectively narrowed the pores with the creation of new acid sites. Phosphate modification of BEA with lower loading was more effective in pore modification without affecting the zeolite structure. Pyrophosphates and polyphosphates are mainly responsible for the narrowing of the zeolite pores. Both the activity and shape selectivity for 2-acetyl-6-methoxynaphthalene were enhanced in the acylation of 2-methoxynaphthalene. At higher concentration of phosphates, conversion and selectivity decreased due to dealumination. 1% P loading was found to be optimum for the acylation of 2-methoxynaphthalene. With the optimized phosphate modification of BEA, high selectivity of 78% to 2-acetyl-6-methoxynaphthalene was achieved with 77% conversion.
- Hodala, Janardhan L.,Halgeri, Anand B.,Shanbhag, Ganapati V.
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- Synthesis of bridged biarylbisquinones and effects of biaryl dihedral angles on photo- and electro-chemical properties
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A series of bridged biarylbisquinones, QBINOLs 1-4, and their corresponding monomers, QNaphs 5-6, were designed to demonstrate the influence of biaryl conformation on the photo- and electro-chemical properties of the molecules. All target compounds were synthesized from the Diels-Alder reaction between silyl enol ethers of the corresponding naphthyl or binaphthyl derivatives and p-benzoquinone. Addition of an OMe auxochrome or formation of the dimeric structures affect the absorption spectra and the energy band gap (Eg), but not the reduction potentials of the molecules. Narrowing the dihedral angles of the QBINOLs by shortening methylene bridges limited the contribution of bridging OR auxochromes and therefore resulted in lower HOMO levels and larger Eg.
- Wongma, Krittaphat,Bunbamrung, Nantiya,Thongpanchang, Tienthong
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- Al-ITQ-7, a Shape-Selective Zeolite for Acylation of 2-Methoxynaphthalene
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Acylation of 2-methoxynaphthalene with acetic anhydride has been carried out with a tridirectional 12-member ring pore zeolite named ITQ-7, which has a slightly smaller pore diameter than zeolite Beta. ITQ-7 is as active as Beta but gives better selectivity to 2-acetyl-6-methoxynaphthalene (2-AMN). This is due to the differences in the relative diffusion coefficients of 2-AMN and 1-acetyl-2-methoxynaphthalene (1-AMN), whose ratios are 2.7 and 15.5 in Beta and ITQ-7, respectively. In general, it can be said that when decreasing the zeolite crystallite size, the reaction rate increases, although the selectivity to 2-AMN decreases.
- Botella,Corma,Sastre
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- Fluorogenic kinetic assay for high-throughput discovery of stereoselective ketoreductases relevant to pharmaceutical synthesis
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Enantiomerically pure 1-(6-methoxynaphth-2-yl) and 1-(6-(dimethylamino)naphth-2-yl) carbinols are fluorogenic substrates for aldo/keto reductase (KRED) enzymes, which allow the highly sensitive and reliable determination of activity and kinetic constants of known and unknown enzymes, as well as an immediate enantioselectivity typing. Because of its simplicity in microtiter plate format, the assay qualifies for the discovery of novel KREDs of yet unknown specificity among this vast enzyme superfamily. The suitability of this approach for enzyme typing is illustrated by an exemplary screening of a large collection of short-chain dehydrogenase/reductase (SDR) enzymes arrayed from a metagenomic approach. We believe that this assay format should match well the pharmaceutical industry's demand for acetophenone-type substrates and the continuing interest in new enzymes with broad substrate promiscuity for the synthesis of chiral, non-racemic carbinols.
- Thai, Yen-Chi,Szekrenyi, Anna,Qi, Yuyin,Black, Gary W.,Charnock, Simon J.,Fessner, Wolf-Dieter
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- Acylation of 2-methoxynaphthalene in the presence of modified zeolite HBEA
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The influence of postsynthesis treatment such as calcination and acid treatment of zeolite HBEA has been studied in the acylation of 2-methoxynaphthalene with acetic anhydride. The contribution of the inner and outer surface of zeolite HBEA is examined by conversion and product selectivity to a bulky product, which can be formed only on the outer surface of HBEA, and to a linear product, which can be formed on the inner and outer surfaces. Calcination under high heating rate enhances the catalytic activity of the inner surface due to the formation of extraframework alumina species in the micropores. FTIR-adsorption experiments of the bulky probe molecule 2,4,6-tri-tert-butylpyridine, which does not fit into the micropores, revealed that these alumina species are located preferentially in the micropores of HBEA. Acid treatment increases the catalytic activity of the outer surface due to the extraction of catalytically active extraframework alumina species out of the micropores and due to the formation of silanol groups, respectively.
- Heinichen,Hoelderich
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- Acylation of 2-methoxynaphthalene and isobutylbenzene over zeolite beta
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The acylation of 2-methoxynaphthalene (2MN) and isobutylbenzene using several zeolite beta samples having varius Si/Al ratios and crystal sizes to examine whether external surface sites could be eliminated to enhance the catalyst performance to obtain a viable acylation catalyst for the formation of precursors to the nonsteroidal anti-inflammatory agents naproxen and ibuprofen. Zeolite beta was active for the acylation of 2MN but was not selective to the desired product, 2-acetyl-6-methoxynaphthalene (2,6-AMN). Mild operating conditions (temperature and acylating agent concentration) could be used to obtain reasonable conversions and to limit catalyst deactivation. The other key product, 1-acetyl-2-methoxynaphthalene (1,2-AMN) formed on the external surface of the zeolite, while 2,6-AMN occurred in the zeolite pores. Thus, the selectivity to 2,6-AMN was enhanced on zeolite beta samples having a larger crystal size, on which most of the acid sites could be passivated by coating the crystals with a layer of amorphous silica. The amount of surface coating on the large crystals determined the yield of and the selectivity to 2,6-AMN. Isobutylbenzene was less reactive than 2MN but the desired product, 4-isobutylacetophenone, was always obtained since the isobutyl group provides for the para position being the preferred sites for acylation. For isobutylbenzene, the zeolite external surface contributed significanlty to the formation of 4-isobutylacetophenone. Zeolite beta with a small crystal size was, thus, the most favored catalyst for this reaction.
- Andy,Garcia-Martinez,Lee,Gonzalez,Jones,Davis
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- Development of a High-Throughput Screen for Protein Catalysts: Application to the Directed Evolution of Antibody Aldolases
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A semiautomated high-throughput system has been developed to express and purify proteins and assay their catalytic activity. The screen can be used to evolve activity, selectivity, and expression levels of proteins directly or in combination with selections. To illustrate its potential, the system was applied to the directed evolution of catalytic antibodies with aldolase activity.
- Gildersleeve, Jeff,Varvak, Alex,Atwell, Shane,Evans, Doug,Schultz, Peter G.
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- Oxidation of 2-methoxy-6-(1-methylethyl)naphthalene with oxygen
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Aerobic oxidation of 2-methoxy-6-(1-methyl-ethyl)naphthalene to hydroperoxide, alcohol, and ketone, is reported. These compounds, particularly 2-acetyl-6-meth-oxynaphthalene, are important intermediates in naproxen synthesis. N-Hydroxyphthalimide is shown here to be an efficient catalyst for oxidation to the hydroperoxide, 2-methoxy-6-(1-hydroperoxy-1-methylethyl) naphthalene, with a yield of 87%. However, the ketone and alcohol were obtained with lower yields, with a maximum yield of 13% for the ketone and 27% for the alcohol, using N-hydroxyphthal-imide and Cu(II) acetylacetonate as a catalyst. The synthesis of the products 2-acetyl-6-methoxynaphthalene and 2-methoxy-6-(1-hydroxy-1-methylethyl)naphthalene via an initial oxidation step to the hydroperoxide followed by a hydroperoxide decomposition step is shown to be more efficient; the ketone and alcohol were obtained from 2-methoxy-6-(1-methylethyl)naphthalene with yields of 40 and 56%, respectively.
- Orlinska, Beata,Stec, Zbigniew,Zawadiak, Jan
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- Regioselective acylation of 2-methoxy naphthalene catalyzed by supported 12-Phosphotungstic acid
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12-Phosphotungstic acid supported on silica gel, zirconium sulfate, and a combination of silica gel and zirconium sulfate (50% w/w) were employed as solid acid catalysts for regioselective acylation of 2-methoxynaphtalene with acetic anhydride. 1-(6-Methoxynaphthalen-2-yl)ethanone (2,6-AMN), a commercially important intermediate for production of Naproxen, was obtained with excellent selectivity (>98%) at 67-68% conversion using 12-phosphotungstic acid supported on silica gel 20% (w/w) in refluxing tetrachloroethane. The unreacted starting material can be easily separated from the product by a simple crystallization from nonane.
- Kumaraguru, Thenkrishnan,Devi, Avala Vedamayee,Siddaiah, Vidavalur,Rajdeo, Kishor,Fadnavis, Nitin W.
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- Zeolite catalyzed highly selective synthesis of 2-methoxy-6-acetylnaphthalene by Friedel-Crafts acylation of 2-methoxynaphthalene in acetic acid reaction media
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Zeolite catalyzed Friedel-Crafts acetylation of 2-methoxynaphthalene to produce 2-methoxy-6-acetylnaphthalene with high selectivity and conversion has been a challenging task, because the obtained compound is a key intermediate for an anti-inflammatory agent, Naproxen. However, no satisfactory results have been obtained with zeolite catalysts, and harmful solvents have been used to gain a high selectivity together with a high conversion. Here, we report the synthesis of 2-methoxy-6-acetylnaphthalene from 2-methoxynaphthalene with a high selectivity and a high conversion under an unprecedented simple reaction system; acetic anhydride as an acetylating agent, acetic acid as a solvent, and proton-type zeolite catalysts with low acidity. Among the examined zeolites, a proton-type H-MOR (SiO2/Al2O3 = 200) with a low acid content shows a conversion of 82% and an 86% selectivity for 2-methoxy-6-acetylnaphthalene. Further, detailed control experiments using H-MOR catalyst in acetic acid solvent were carried out to propose a plausible reaction mechanism.
- Yamazaki, Tomoyoshi,Makihara, Makoto,Komura, Kenichi
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- THE SHAPE-SELECTIVE ACYLATION OF 2-METHOXYNAPHTHALENE, CATALYZED BY ZEOLITES Y, BETA AND ZSM-12
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The Friedel-Crafts acylation of 2-methoxynaphthalene (2MN) was investigated using zeolites USY, Beta and ZSM-12 as catalysts under batch conditions at 100 and 180 deg C.Two ketone isomers, 1-acetyl-2-methoxynaphthalene (1AC) and 2-acetyl-6-methoxynaphthalene (2AC) were produced; the selectivity of the reaction could be influenced by the zeolite used.USY produced only the 1AC isomer whereas Beta and ZSM-12 produced both.Selective synthesis of 2AC was achieved by optimization of the reaction conditions using zeolite Beta as the catalyst.It was also observed that the 1AC ketone is unstable in contact with acid zeolite catalysts and undergoes protiodeacylation, a reaction previously only observed in the presence of strong mineral acids.
- Harvey, Gillian,Maeder, Georg
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- Direct Enantio- and Diastereoselective Oxidative Homocoupling of Aldehydes
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A novel strategy for the direct enantioselective oxidative homocoupling of α-branched aldehydes is presented. The methodology employs open-shell intermediates for the construction of chiral 1,4-dialdehydes by forming a carbon–carbon bond connecting two quaternary stereogenic centers in good yields and excellent stereoselectivities for electron-rich aromatic aldehydes. The 1,4-dialdehydes were transformed into synthetically valuable chiral pyrrolidines. Experimental mechanistic investigations based on competition experiments combined with computational studies indicate that the reaction proceeds through a radical cation intermediate and that reactivity and stereoselectivity follow different trends.
- N?sborg, Line,Leth, Lars A.,Reyes-Rodríguez, Gabriel J.,Palazzo, Teresa A.,Corti, Vasco,J?rgensen, Karl Anker
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- From Esters to Ketones via a Photoredox-Assisted Reductive Acyl Cross-Coupling Strategy
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A method was developed for ketone synthesis via a photoredox-assisted reductive acyl cross-coupling (PARAC) using a nickel/photoredox dual-catalyzed cross-electrophile coupling of two different carboxylic acid esters. A variety of aryl, 1°, 2°, 3°-alkyl 2-pyridyl esters can act as acyl electrophiles while N-(acyloxy)phthalimides (NHPI esters) act as 1°, 2°, 3°-radical precursors. Our PARAC strategy provides an alternative and reliable way to synthesize various sterically congested 3°-3°, 3°-2°, and aryl-3° ketones under mild and highly unified conditions, which have been otherwise difficult to access. The combined experimental and computational studies identified a Ni0/NiI/NiIII pathway for ketone formation.
- Chen, Yukun,Li, Weirong,Luo, Yixin,Qi, Xiaotian,Xi, Xiaoxiang,Xu, Minghao,Yuan, Weiming,Zhao, Hongping,Zheng, Songlin
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supporting information
(2021/12/06)
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- Naproxen sodium salt photochemistry in aqueous sodium dodecyl sulfate (SDS) ellipsoidal micelles
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The photochemistry and other properties of the anti-inflammatory drug (NSAID) naproxen (NP) in sodium dodecyl sulfate, SDS, micellar aqueous solutions at pH = 7 (NP is in anionic form) were studied. The large value of the partition coefficient (P) was obtained, logP = 2.7, showing that the most part of NP is localized in the micellar phase. The solubilization in SDS micelles results in NP fluorescence and photodegradation quantum yields decrease. The photoproducts 6-methoxy-2-(1-hydroxyethyl)-naphthalene and 6-methoxy-2-acetyl-naphthalene were found by gas chromatography/mass spectrometry (GC/MS). Both photoproducts were formed in SDS solution in significantly smaller amounts than in water. Small angle neutron scattering (SANS) showed that the presence of NP has small effect on the micellar structure. Only a slight decrease of the ionization degree of the micelle was observed by SANS, suggesting that NP was localized in the vicinity of micellar surface. The NP triplet excited state, hydrated electron, NP radical cation and some other relatively long lived intermediate were observed by laser flash photolysis of NP in micellar solution. The decay kinetics of these intermediates was different with respect to that in the homogeneous media. The reactivity of NP in SDS micellar environment was compared to that in the homogeneous media and the probable nature of the intermediate precursors of the final photoproducts are under the discussion.
- Valero,Sultimova, Natalya B.,Houston, Judith E.,Levin, Peter P.
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- Engineering the Active Site of an (S)-Selective Amine Transaminase for Acceptance of Doubly Bulky Primary Amines
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A protein engineering approach for expanding the substrate scope of the (S)-selective Chromobacterium violaceum amine transaminase is presented. Amino acid residues in the small binding pocket of the active site were targeted in order to increase the pocket size for acceptance of primary amines bearing two bulky groups. A highly sensitive fluorescence assay was then used to evaluate the generated enzyme variants for their activity towards propyl- and benzyl-substituted screening substrates. The best variant, L59A/F88A, was successfully applied in the kinetic resolution of 1,2-diphenylethylamine using different conditions and substrate loadings. The variant L59A/F88A generated enantiomerically pure (R)-1,2-diphenylethylamine with ee>99% under all tested conditions. The variant also holds great promise for synthesis of hydrophobic compounds as it shows optimum activity when 20-30% (v/v) DMSO is applied as cosolvent. The variant L59A/F88A provides a great addition to the available catalyst toolbox for synthesis of chiral amines, as it is the first published (S)-selective amine transaminase showing activity towards benzyl-substituted primary amines. (Figure presented.).
- Land, Henrik,Ruggieri, Federica,Szekrenyi, Anna,Fessner, Wolf-Dieter,Berglund, Per
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supporting information
p. 812 - 821
(2019/12/24)
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- Visible-light-promoted oxidative decarboxylation of arylacetic acids in air: Metal-free synthesis of aldehydes and ketones at room temperature
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A metal-free photocatalytic oxidative decarboxylation reaction at room temperature was developed for the synthesis of aromatic aldehydes and ketones from the corresponding arylacetic acids. The reaction was realized under blue-light irradiation by adding 1 molpercent of 4CzIPN as photocatalyst and air as oxidant. This reaction represents a novel decarboxylation of a sp3-hybridized carboxylic acids without traditional heating, additional oxidants, and metal reagents under mild conditions.
- He, Shuaiqi,Chen, Xiaolan,Zeng, Fanlin,Lu, Peipei,Peng, Yuyu,Qu, Lingbo,Yu, Bing
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supporting information
p. 1863 - 1867
(2020/01/03)
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- FeCl3-catalyzed oxidative decarboxylation of aryl/heteroaryl acetic acids: Preparation of selected API impurities
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There is an ever-increasing demand for impurity compounds for use in impurity profiling as regulatory agencies seek information during registration. Herein, we report the FeCl3-catalyzed oxidative decarboxylation of aryl- and heteroaryl acetic acids to the corresponding carbonyl compounds. A variety of useful aldehydes and ketones were prepared in a simple one-pot transformation by employing an environmentally benign, low-cost, and readily available iron salt. The utility of this method has been demonstrated by preparing five valuable API impurities including a multi-gram-scale synthesis of ketorolac impurity B for the first time. This journal is
- Gangadurai, Chinnakuzhanthai,Illa, Giri Teja,Reddy, D. Srinivasa
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p. 8459 - 8466
(2020/11/05)
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- Decarboxylative Oxygenation via Photoredox Catalysis
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The direct conversion of aliphatic carboxylic acids to their dehomologated carbonyl analogues has been accomplished through photocatalytic decarboxylative oxygenation. This transformation is applicable to an array of carboxylic acid motifs, producing ketones, aldehydes, and amides in excellent yields. Preliminary results demonstrate that this methodology is further amenable to aldehyde substrates via in situ oxidation to the corresponding acid and subsequent decarboxylative oxygenation. We have exploited this strategy for the sequential oxidative dehomologation of linear aliphatic chains.
- Faraggi, Tomer M.,Li, Wei,MacMillan, David W. C.
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p. 410 - 415
(2019/12/24)
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- Gold(i)-catalyzed Nicholas reaction with aromatic molecules utilizing a bifunctional propargyl dicobalt hexacarbonyl complex
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A benchtop-stable reagent for the catalytic Nicholas reaction was developed. By combining a propargyl dicobalt hexacarbonyl cluster with an ortho-alkynylbenzoate unit and a fluorous tag, introduction of a propargyl hexacarbonyl complex on various aromatic compounds having acid- or base-sensitive functional groups becomes possible by using a gold(i) catalyst. In addition, the presence of a fluorous tag facilitates convenient separation of the target products from byproducts.
- Okamura, Toshitaka,Fujiki, Shogo,Iwabuchi, Yoshiharu,Kanoh, Naoki
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supporting information
p. 8522 - 8526
(2019/10/02)
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- Enantiocomplementary decarboxylative hydroxylation combining photocatalysis and whole-cell biocatalysis in a one-pot cascade process
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Designing a green, highly efficient and stereoselective catalytic system to generate valuable enantioenriched products is a long-standing goal in green chemistry. Here, we report a one-pot cascade combining photocatalysts with (R)- or (S)-selective ketoreductases for the decarboxylative carbonylation of carboxylic acids and the subsequent bioreduction to generate valuable chiral alcohols. Using this approach, various chiral alcohols with complementary (R)- or (S)-configurations were prepared with good yields (up to 93%) and excellent stereoselectivity (up to 99% ee). Such a photochemo-enzymatic one-pot whole-cell process combines the advantages of both photocatalysts and enzyme catalysts and provides a mild, green, metal-free and highly stereoselective alternative in asymmetric decarboxylative hydroxylation reactions.
- Xu, Jian,Arkin, Mamatjan,Peng, Yongzhen,Xu, Weihua,Yu, Huilei,Lin, Xianfu,Wu, Qi
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supporting information
p. 1907 - 1911
(2019/04/27)
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- Thiyl radical promoted chemo- and regioselective oxidation of CC bonds using molecular oxygen: Via iron catalysis
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The first example of the thiyl radical promoted ligand-free iron-catalyzed oxidative cleavage of alkenes using molecular oxygen (1 atm) has been developed. The reaction proceeds under mild reaction conditions with high efficiency and high chemo- and regioselectivity. It features a broad substrate scope and excellent functional group compatibility, enabling facile access to valuable molecules for application in medicinal chemistry. Preliminary mechanistic studies reveal that a vital intermediate dioxetane might be involved in the reaction and a thiyl radical plays a synergistic role in facilitating the selective oxidation of the CC bond.
- Xiong, Baojian,Zeng, Xiaoqin,Geng, Shasha,Chen, Shuo,He, Yun,Feng, Zhang
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supporting information
p. 4521 - 4527
(2018/10/17)
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- Visible light promoted copper-catalyzed Markovnikov hydration of alkynes at room temperature
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A new and efficient method for the hydration of alkynes to the corresponding ketones was successfully developed. The hydration process proceeds smoothly at room temperature with 1% mol of CuCl as catalyst under visible light irradiation. This protocol is applicable to various alkynes, including aromatic alkynes, polycyclic aromatic and heterocyclic aromatic excellent regioselectivity in good to excellent yields.
- Niu, Teng-fei,Jiang, Ding-yun,Li, Si-yuan,Shu, Xing-ge,Li, Huan,Zhang, Ai-ling,Xu, Jia-yu,Ni, Bang-qing
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supporting information
p. 1156 - 1159
(2017/03/02)
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- Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids Driven by Visible Light and Using Molecular Oxygen
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This paper discloses the first example of photocatalytic direct decarboxylative hydroxylation of carboxylic acids. It enables the conversion of a variety of readily available carboxylic acids to alcohols in moderate to high yields. This unprecedented protocol is accomplished under extremely mild reaction conditions using molecular oxygen (O2) as a green oxidant and using visible light as a driving force.
- Song, Hai-Tao,Ding, Wei,Zhou, Quan-Quan,Liu, Jing,Lu, Liang-Qiu,Xiao, Wen-Jing
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supporting information
p. 7250 - 7255
(2016/08/30)
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- Hierarchical ZSM-5 zeolite with uniform mesopores and improved catalytic properties
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Hierarchical ZSM-5 with uniform mesoporosity was synthesized by the sequential coupling of two strategies: generation of secondary porosity by the crystallization of silanized protozeolitic units and a subsequent treatment with a basic surfactant-containing solution. The ZSM-5 zeolite obtained exhibited high crystallinity and contained two levels of uniform porosities within the micro- and mesopore ranges, respectively. The uniform mesoporosity is the result of the reorganization of irregular mesopores, created initially from the silanized protozeolitic units, via the local rearrangement of zeolitic fragments, and promoted by contact with a cationic surfactant under mild basic conditions. Interestingly, this second treatment was less effective when it is applied to a non-hierarchical ZSM-5 sample, showing that the presence of initial secondary porosity is essential for allowing the surfactant/ammonia solution to modify the zeolite and form uniform mesopores. Characterization of the zeolite samples using different techniques showed that the crystallinity, Al coordination and acidic features of the zeolite do not change significantly after the mesopore narrowing treatment, even though significant variations in the textural properties are observed as expected. The effects of the occurrence of regular mesoporosity on the catalytic properties of the hierarchical ZSM-5 zeolite were proven using the acylation of 2-methoxynaphthalene as a test reaction. The material with uniform mesopores showed both the highest activity and selectivity towards 6-acetyl-2-methoxynaphthalene, which was interpreted as the result of the presence of a more regular and less rough mesopore surface, which in turn facilitated the interaction between the reactant molecules and the active sites located and distributed over the mesopores.
- Serrano,Escola,Sanz,Garcia,Peral,Moreno,Linares
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p. 4206 - 4216
(2016/06/09)
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- PROTEIN COMPLEX CAPABLE OF CATALYZING ASYMMETRIC OXIDATION REACTION AND METHOD FOR PRODUCING SAME
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Provided are: a protein complex capable of selectively and asymmetrically oxidizing one of enantiomers of a secondary alcohol without adding a coenzyme and having an asymmetric oxidation activity in a water-soluble solvent system in the presence of oxygen; a method for producing the same; and a production method relating to coating of the protein complex with a high molecular compound. A method for producing a protein complex capable of catalyzing an asymmetric oxidation reaction, said method being characterized by comprising: a first step that comprises a treatment for enclosing a crude water-soluble protein derived from an animal or plant in a gel, a treatment for air-oxidizing the gel, and a treatment for eluting the protein complex from the gel into an aqueous solution; and a second step that comprises a treatment for applying gravity to the aqueous solution of the protein complex to concentrate and precipitate the protein complex, a treatment for redissolving the protein complex precipitate in an aqueous glycine sodium hydroxide solution of about 0.5 mM and allowing the same to homogeneously coexist with a high molecular compound, and a treatment for re-precipitating the coexistence solution and dehydrating and drying the same to give the protein complex coated with the high molecular compound.
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Paragraph 0073
(2015/11/10)
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- Selective arylthiolane deprotection by singlet oxygen: A promising tool for sensors and prodrugs
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A routine thioketal protecting group reacts rapidly and selectively with singlet oxygen to reveal ketone products in good (aryl 1,3-dithiolane) to excellent (aryl 1,3-oxathiolane) yields. Arylthiolanes are stable to biologically relevant reactive oxygen species and can be used as a light-activated gating mechanism for activating fluorescent sensors or small molecule prodrugs.
- Lamb, Brian M.,Barbas, Carlos F.
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supporting information
p. 3196 - 3199
(2015/05/27)
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- METHOD OF ACYLATING AN AROMATIC COMPOUND
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The present invention relates to a method of acylating a substituted aromatic compound. The substituted aromatic compound is reacted with an acylating agent in the presence of a macroreticular sulfonic acid ion exchange resin having a water-to-phenol shrinkage between 25 % and 40 %. The method is very advantageous in that the resin is deactivated much less than other resins without a fast drop in conversion and selectivity in the reaction.
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Page/Page column 17
(2015/01/16)
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- Solvent-free hydration of alkynes over Hβ zeolite
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Abstract An efficient and environmentally benign catalytic system has been successfully developed for highly Markovnikov selective hydration of various alkynes over heterogeneous catalyst (Hβ zeolite) in solvent-free conditions. The catalyst (Hβ zeolite) is commercial available, recyclable and exhibits excellent catalytic activity towards the hydration of alkynes to ketones. Moreover, the propargylic aryl carbinols undergo Meyer-Schuster rearrangement to give α,β-unsaturated carbonyl compounds in excellent yields.
- Mameda, Naresh,Peraka, Swamy,Marri, Mahender Reddy,Kodumuri, Srujana,Chevella, Durgaiah,Gutta, Naresh,Nama, Narender
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p. 213 - 216
(2015/08/24)
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- Acetylation of 2-methoxynaphtalene with acetic anhidryde over Zr4+-zeolite beta
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Regioselective acetylation of 2-methoxy naphthalene (2-MN) to 2-acetyl-6-methoxy naphthalene (2,6-ACMN) is the important step in the synthesis of pharmaceutical compounds such as (S)-naproxen. The liquid phase acetylation of 2-MN with acetic anhydride over Zr4+-zeolite beta catalyst was investigated under controlled reaction conditions. Catalyst was prepared by ion exchange and impregnation method. Zr4+-zeolite beta(ie) was obtained by ion exchange that done with 0,5 M ZrCl4 then calcined at 550°C for 3 h and Zr4+-zeolite beta(ip) was obtained by impregnation method. Catalytic activity of catalysts was affected by preparing method, temperature, and reaction solvent. Catalyst that prepared by impregnation showed inactive on acetylation of 2-MN. 1-Acetyl-2-methoxynaphtalene (1,2-ACMN), 1-acetyl-7-methoxy-naphtalene (1,7-ACMN), and 2-acetyl-6-methoxy naphthalene (2,6-ACMN) were identified as the products of 2-MN acetylation over Zr4+-zeolite beta(ie) without solvent. Activity and selectivity of Zr4+-zeolite beta(ie) was increased in dichloromethane solvent at 140°C for 36 h, 1,8-ACMN was not identified and ratio of 1,2-ACMN to 2,6-ACMN was 1,6:1.
- Cahyono, Edy,Priatmoko, Sigit,Haryani, Sri
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- Synthesis of industrially important aromatic and heterocyclic ketones using hierarchical ZSM-5 and Beta zeolites
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Hierarchical ZSM-5 and Beta zeolites were investigated in the synthesis of wide range of industrially important aromatic/heterocyclic ketones by Friedel-Crafts acylation and benzoylation reactions. For comparative study, conventional ZSM-5 and Beta, and amorphous mesoporous Al-MCM-41 were investigated. Hierarchical zeolites were prepared by multi-ammonium structure directing agents whereas conventional zeolites were prepared by mono-ammonium structure directing agents. Among the catalysts investigated in this study, hierarchical Beta exhibited the highest reactant conversion in the acylation and benzoylation reactions. In this study, the systematic assessment of the catalytic activity of acid catalysts for wide range of aromatic and heterocyclic compounds is shown under one umbrella. To the best of our knowledge, these reactions over hierarchical zeolites (ZSM-5 and Beta) are reported here for the first time. Structure activity relationship is explained based on the physico-chemical properties, molecular size, reactivity of reactants, and reaction mechanism. Catalysts can be easily recovered and reused with negligible loss in the catalytic activity.
- Kore, Rajkumar,Srivastava, Rajendra,Satpati, Biswarup
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p. 129 - 141
(2015/09/28)
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- Oxidations of allylic and benzylic alcohols under inductively-heated flow conditions with gold-doped superparamagnetic nanostructured particles as catalyst and oxygen as oxidant
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A continuous flow protocol for the oxidation of allylic and benzylic alcohols to aldehydes and ketones, respectively, using oxygen gas or atmospheric air is reported. The key features of this work are gold nanoparticles that are attached to the surface of nanostructured core shell particles composed of an Fe3O4-containing core and a silica shell. These nanostructured particles exert superparamagnetic properties and thus inductively heat up in an external oscillating electromagnetic field, conditions under which the gold catalyst is able to perform these oxidation reactions.
- Chaudhuri, Sangeeta Roy,Hartwig, Jan,Kupracz, Lukas,Kodanek, Torben,Wegner, Jens,Kirschning, Andreas
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supporting information
p. 3530 - 3538
(2015/02/19)
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- Application of a heme-binding protein eluted from encapsulated biomaterials to the catalysis of enantioselective oxidation
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A protein complex (PX) eluted from an encapsulated pea protein (PP) under aeration can be used as two types of biocatalysts: a polyethylene glycol (PEG) (1000/4000 = 2/1)-aggregated PX (AGPX) and a glutaraldehyde (GA)/compound- modified PX (CMPX). These biocatalysts have the following functional activities: AGPX can catalyze the oxidation of rac-1-(6-methoxynaphthalen-2-yl)ethanol (rac-1) to the corresponding ketone (~95% chemical yield) via the selective oxidation of (S)-(+)-1, leaving highly enantiopure (R)-(-)-1 (>99% ee; ~50% chemical yield); CMPX can catalyze the kinetic resolution of (S)-(+)-1 ((S)-naproxen precursor, >99% ee, ~50% chemical yield) via the selective oxidation of (R)-(-)-1 to the corresponding ketone. Both reactions occur in the absence of an added cofactor (e.g., NAD(P)) in aqueous media. The specific activities of AGPX and CMPX were determined to be 0.8 ± 0.03 mU (mean ± SD) and 0.6 ± 0.02 mU (mean ± SD), respectively, and the exact nature of the species engaged in the key reaction was consistent with that of a heme-binding protein (HBP), on the basis of an N-terminal sequence comparison, which showed 93% similarity with a 20.853 kDa hemophore HasA gene product [Pseudomonas fluorescens Pf-5, a plant commensal bacterium]. PP-HBP can be regenerated via successive asymmetric catalytic events using an incorporated iron electron-transfer system (Fe2+ a? Fe3+) in the presence of oxygen, a process seemingly similar to that utilized by hemoglobin. The use of a raw biomaterial as a PX-catalytic system with an incorporated redox cofactor for asymmetric oxidation overcomes the apparent difficulties in working with pure dehydrogenase enzyme/redox cofactor systems for biotransformation.
- Nagaoka, Hiroyuki
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p. 553 - 565
(2014/03/21)
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- Heterocycle-substituted tetrazole ligands for copper-catalysed aerobic oxidation of alcohols
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An efficient copper-catalysed aerobic oxidation of alcohols has been established, which employed heterocycle-substituted tetrazoles as ligands. The commercially available (S)-5-(pyrrolidin-2-yl)-1H-tetrazole proved as the best ligand for this oxidation. Under optimized conditions, the substrate scope was broadened. A plausible mechanism was also proposed.
- Liu, Yangyang,Xie, Aming,Li, Junjian,Xu, Xiao,Dong, Wei,Wang, Boliang
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p. 9791 - 9796
(2015/01/09)
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- 2-Iodoxybenzenesulfonic acid-catalysed oxidation of primary and secondary alcohols with oxone in cetyl trimethylammonium bromide micelles at room temperature
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A mild and green protocol for alcohol oxidation using 2-iodoxybenzene sulfonic acid/oxone at room temperature in CTAB micelles has been developed. Typically, secondary benzyl alcohols were oxidised to ketones and primary benzyl alcohols to aldehydes in good yields in 2 h. Under harsher conditions (100 °C/24 h), aliphatic alcohols were oxidised to ketones or organic acids in moderate to high yields.
- Liu, Yangyang,Wang, Boliang
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p. 427 - 431
(2014/08/05)
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- Efficient and eco-compatible transition metal-free Oppenauer-type oxidation of alcohols
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Catalytic amounts of cheap, non-toxic, easy-to-handle and non-sensitive sodium tert-butoxide are able to promote the dehydrogenative oxidation of a wide array of secondary alcohols using inexpensive benzophenone as the H-acceptor. The corresponding ketones, highly important intermediates and targets throughout life and material sciences, are very selectively obtained under mild conditions.
- Ballester, Jorge,Caminade, Anne-Marie,Majoral, Jean-Pierre,Taillefer, Marc,Ouali, Armelle
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- Process for the production of an acylation catalyst
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The present invention relates to a process for the preparation of a zeolitic material having a BEA framework structure comprising the steps of: (i) providing one or more zeolitic materials having a BEA framework structure, wherein the BEA framework structure comprises YO2 and X2O3, wherein Y is a tetravalent element, and X is a trivalent element; (ii) subjecting the one or more zeolitic materials provided in step (i) to a procedure for removing at least a portion of X, preferably tetrahedrally coordinated X, from the BEA framework structure; wherein the Y:X molar ratios of the one or more zeolitic materials provided in step (i) are respectively comprised in the range of from 1 to 50.
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Page/Page column 44
(2014/05/08)
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- Bulky, spherical, and fluorinated anion BArF induces 'on-water' activity of silver salt for the hydration of terminal alkynes
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AgBArF displays remarkable 'on-water' activity for catalytic hydration of terminal alkynes although it is ineffective in common organic solvents. Liquid alkynes do not require additive or co-solvent whereas a small amount of ethyl acetate triggers quantitative conversions for solid alkynes.
- Saha, Sayantani,Sarbajna, Abir,Bera, Jitendra K.
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supporting information
p. 1444 - 1447
(2014/03/21)
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- Single-step delamination of a MWW borosilicate layered zeolite precursor under mild conditions without surfactant and sonication
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Layered borosilicate zeolite precursor ERB-1P (Si/B = 11) is delaminated via isomorphous substitution of Al for B using a simple aqueous Al(NO 3)3 treatment. Characterization by PXRD shows loss of long-range order, and TEM demonstrates transformation of rectilinear layers in the precursor to single and curved layers in the delaminated material. N 2 physisorption and base titration confirm the expected decrease of micropore volume and increase in external surface area for delaminated materials relative to their calcined 3D zeolite counterpart, whereas FTIR and multinuclear NMR spectroscopies demonstrate synthesis of Bronsted acid sites upon delamination. Comparative synthetic studies demonstrate that this new delamination method requires (i) a borosilicate layered zeolite precursor, in which boron atoms can be isomorphously substituted by aluminum, (ii) neutral amine pore fillers instead of rigid and large quaternary amine SDAs, and (iii) careful temperature control, with the preferred temperature window being around 135 C for ERB-1P delamination. Acylation of 2-methoxynaphthalene was used as a model reaction to investigate the catalytic benefits of delamination. A partially dealuminated delaminated material displays a 2.3-fold enhancement in its initial rate of catalysis relative to the 3D calcined material, which is nearly equal to its 2.5-fold measured increase in external surface area. This simple, surfactant- and sonication-free, mild delamination method is expected to find broad implementation for the synthesis of delaminated zeolite catalysts.
- Ouyang, Xiaoying,Hwang, Son-Jong,Runnebaum, Ron C.,Xie, Dan,Wanglee, Ying-Jen,Rea, Thomas,Zones, Stacey I.,Katz, Alexander
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p. 1449 - 1461
(2014/02/14)
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- The indium-catalysed hydration of alkynes using substoichiometric amounts of PTSA as additive
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A general, efficient and highly regioselective protocol using an indium(III) trifluoromethanesulfonate and PTSA (TsOH·H2O) catalytic system for the transformation of various alkynes to the corresponding ketones has been successfully developed.
- Gao, Qi,Li, Shenyan,Pan, Yingming,Xu, Yanli,Wang, Hengshan
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supporting information
p. 3775 - 3781
(2013/06/26)
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- Complementation of biotransformations with chemical C-H oxidation: Copper-catalyzed oxidation of tertiary amines in complex pharmaceuticals
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The isolation, quantitation, and characterization of drug metabolites in biological fluids remain challenging. Rapid access to oxidized drugs could facilitate metabolite identification and enable early pharmacology and toxicity studies. Herein, we compared biotransformations to classical and new chemical C-H oxidation methods using oxcarbazepine, naproxen, and an early compound hit (phthalazine 1). These studies illustrated the low preparative efficacy of biotransformations and the inability of chemical methods to oxidize complex pharmaceuticals. We also disclose an aerobic catalytic protocole (CuI/air) to oxidize tertiary amines and benzylic CH's in drugs. The reaction tolerates a broad range of functionalities and displays a high level of chemoselectivity, which is not generally explained by the strength of the C-H bonds but by the individual structural chemotype. This study represents a first step toward establishing a chemical toolkit (chemotransformations) that can selectively oxidize C-H bonds in complex pharmaceuticals and rapidly deliver drug metabolites.
- Genovino, Julien,Luetz, Stephan,Sames, Dalibor,Toure, B. Barry
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supporting information
p. 12346 - 12352
(2013/09/23)
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- Catalytic applications of OSDA-free Beta zeolite
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Beta zeolite obtained from seeded synthesis without the use of organic structure directing agents (OSDAs) has been used as a catalyst in different types of reactions. The large number of strong acid sites resulted in a high activity for the alkylation of benzene with ethene and a high cracking activity in the hydroconversion of n-decane. However, the high framework polarity resulted in fast deactivation in the acylation of aromatic ethers. Dealumination treatments resulted in improved stability in alkylation reactions with the more reactive olefins like propene. In acylation reactions, the activity was significantly increased, and in hydroconversion, a better balance between the hydrogenation/dehydrogenation and the acid sites was obtained.
- De Baerdemaeker, Trees,Yilmaz, Bilge,Mueller, Ulrich,Feyen, Mathias,Xiao, Feng-Shou,Zhang, Weiping,Tatsumi, Takashi,Gies, Hermann,Bao, Xinhe,De Vos, Dirk
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- AgOTf catalyzed hydration of terminal alkynes
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The silver catalysis towards the hydration of terminal alkynes is explored using Silver(I) triflate (AgOTf). The reaction leads to the formation of only Markovnikov addition product with excellent yield. Copyright
- Das, Rima,Chakraborty, Debashis
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p. 722 - 726
(2013/02/22)
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- Preparation and characterization of Zr-MCM-41 synthesized under microwave irradiation condition for acetylation of 1,2-dimethoxybenzene with acetic anhydride
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The liquid phase of acetylation of 1,2-dimethoxybenzene with acetic anhydride has been investigated over a series of acid zirconium mesoporous materials (Zr-MCM-41) synthesized by a microwave irradiation method with different Si/Zr ratios (Si/Zr = 90, 60, 10) and characterized by several spectroscopic techniques such as: N2 physical adsorption, ICP, XRD, TEM, FT-IR, UV-vis and a temperature-programmed desorption (TPD) of pyridine. In fact, the catalyst Zr-MCM-41 (10) showed a greater performance in the acid-catalyzed acetylation of 1,2-dimethoxybenzene employing acetic anhydride as an acylating agent. Furthermore, the kinetics of the acetylation of 1,2-dimethoxybenzene over these catalysts have also been investigated. Springer Science+Business Media B.V. 2011.
- Bachari,Chebout,Guerroudj,Lamouchi
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experimental part
p. 367 - 381
(2012/06/01)
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- METHOD FOR CARRYING OUT OXIDATION REACTIONS USING INDUCTIVELY HEATED HEATING MEDIUM
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The invention relates to a method for carrying out an oxidation reaction for producing a product by heating a reaction medium containing a reactant and oxygen or an oxygen carrier in a reactor, wherein the reaction medium is brought into contact with a solid heating medium which may be heated by electromagnetic induction, which is surrounded by the reaction medium. The heating medium is heated by electromagnetic induction using an inductor, wherein an oxidation reaction is carried out on the first reactant to give a product and the product is separated from the heating medium. The inductor preferably generates an alternating field with a frequency in the range 1 to 100 kHz, preferably in the range 10 to 80 kHz and in particular up to 50 kHz.
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Page/Page column 6-7
(2011/12/14)
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- Racemization of secondary alcohols catalyzed by ruthenium: Application to chemoenzymatic dynamic resolution
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In this paper, we have shown that the [RuCl2(p-cymene)] 2 complex associated with simple hemisalen ligands is able to racemize (S)-1-phenylethanol. The influence on the racemization process of the ligand's structure as well as the nature of a co-catalyst have been evaluated and optimized. This [RuCl2(p-cymene)]2/Ligand/TEMPO racemization system was then associated with the Candida Antarctica B lipase in order to carry out dynamic kinetic resolution experiments on rac-phenylethanol. This led us to identify the best conditions for effective DKR, which was then applied to various secondary benzylic and aliphatic alcohols. It was thus possible to obtain (R)-1-cyclohexylethyl acetate from rac-1-cyclohexylethanol in quantitative conversion and with high enantioselectivity (98%).
- Merabet-Khelassi, Mounia,Vriamont, Nicolas,Aribi-Zouioueche, Louisa,Riant, Olivier
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experimental part
p. 1790 - 1796
(2012/01/03)
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- Efficient synthesis of alkyl aryl ketones & ketals via palladium-catalyzed regioselective arylation of vinyl ethers
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The combination of Pd(OAc)2 with 1,3-bis(diphenylphosphino) propane (dppp) in ethylene glycol constitutes a high-performance catalytic system for highly regioselective arylation of a range of electron-rich vinyl ethers by aryl bromides to provide, upon hydrolysis, alkyl aryl ketones and cyclic ketals in good yields with up to 3.75 × 105 TON and 15625 h-1 TOF.
- Liu, Mingcui,Hyder, Zeynab,Sun, Yawei,Tang, Weijun,Xu, Lijin,Xiao, Jianliang
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supporting information; experimental part
p. 2012 - 2015
(2010/07/04)
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- Chemoenzymatic synthesis of (2S)-2-arylpropanols through a dynamic kinetic resolution of 2-arylpropanals with alcohol dehydrogenases
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We applied Horse Liver Alcohol Dehydrogenase (HLADH) to the enantioselective synthesis of six (2S)-2-arylpropanols, useful intermediates in the synthesis of Profens. The influence of substrate structure and reaction conditions on yields and enantioselectivity were investigated. The high yields and high enantioselectivity towards the (S)-enantiomer obtained in the bioreduction of 2-arylpropionic aldehydes, clearly indicate the achievement of a DKR process through a combination of an enzyme-catalyzed kinetic reduction with a chemical base-catalyzed racemization of the unreacted aldehydes. The racemization step is represented by the keto-enol equilibrium of the aldehyde and can be controlled by modulating pH and reaction conditions.
- Galletti, Paola,Emer, Enrico,Gucciardo, Gabriele,Quintavalla, Arianna,Pori, Matteo,Giacomini, Daria
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experimental part
p. 4117 - 4123
(2010/10/03)
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- Inductively heated oxides inside microreactors - Facile oxidations under flow conditions
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Inductively heated iron oxides mixed with solid oxidants like CrO 2 and NiO2 efficiently oxidize organic substrates under flow conditions in fixed-bed reactors.
- Wegner, Jens,Ceylan, Sascha,Friese, Carsten,Kirschning, Andreas
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experimental part
p. 4372 - 4375
(2010/09/20)
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- INHIBITORS OF ACETYL-COA CARBOXYLASE
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The present invention relates to compounds that act as acetyl-CoA carboxylase (ACC) inhibitors. The invention also relates to methods of preparing the compounds, compositions containing the compounds, and to methods of treatment using the compounds.
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Page/Page column 67
(2010/11/17)
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- One-pot two-step oxidative cleavage of 1,2-arylalkenes to aryl ketones instead of arylaldehydes in an aqueous medium: A complementary approach to ozonolysis
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A new approach has been developed for a one-pot and selective oxidative cleavage of aryl- and 1,2-diarylalkenes leading to one-carbon shorter aryl ketones; thereby, providing a complementary approach to classical ozonolysis. The methodology was applicable to diverse aromatic and polyaromaticarylalkenes bearing electron-donating or -withdrawing groups on the aromatic ring. The protocol also provided a useful one-pot oxidative cleavage-condensation sequence, which could potentially have important applications in natural product total synthesis. A one-pot, two-step approach has been achieved for the oxidative cleavage of 1,2-disubstituted arylalkenes into the corresponding aryl ketones instead of arylaldehydes (see scheme; NIS = N-iodosuccinimide; CTAB = cetyltrimethylammonium bromide; PDC/TBHP = pyridinium dichromate/tert-butyl hydroperoxide). The methodology also led to a valuable one-pot oxidative cleavage-condensation reaction that has widespread utility in the total synthesis of natural products.
- Sharma, Naina,Sharma, Abhishek,Kumar, Rakesh,Shard, Amit,Sinha, Arun K.
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supporting information; experimental part
p. 6025 - 6032
(2011/02/23)
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- Assessment of the catalytic activities of novel broensted acidic ionic liquid catalysts
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Broensted acidic ionic liquids (BILs) were synthesized by a two step synthetic protocol. Catalytic activities of BILs were assessed by means of suitable catalytic reactions such as acylation of 2-methoxynapthalene with acetic anhydride, Biginelli reaction to synthesize 3,4-dihydropyrimidin-2(1H)- one, stereoselective synthesis of β-amino ketone via direct Mannich-type reaction and esterification of hexanoic acid with benzyl alcohol. Catalytic activities of BILs were high when compared with those of solid acid catalysts such as ZSM-5, beta, dealuminated beta and Al-SBA-15. BILs catalysts were found to be highly stereo/regio-selective for above mentioned reactions. Novel BILs catalyst offers several attractive features such as low cost, high catalytic activity/selectivity and recyclability. Graphical Abstract: N-methylimidazole and pyridine derived Broensted acidic ionic liquids were found to be highly active and stereo/regio-selective compared to various solid acid catalysts in fine chemicals (1-5) synthesis.[Figure not available: see fulltext.]
- Srivastava, Rajendra
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experimental part
p. 17 - 25
(2010/12/25)
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- Nickel-catalyzed cross-coupling of aryl methyl ethers with aryl boronic esters
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(Chemical Equation Presented) To C-OMe and go: The title reaction, involving cleavage of a C-OMe bond, is demonstrated for the coupling of aryl methyl ethers on fused aromatic systems, such as naphthalene and phenanthrene, as well as anisoles containing electron-withdrawing groups with a wide range of boronic esters. cod=cycloocta-1,5-diene, Cy=cyclohexyl.
- Tobisu, Mamoru,Shimasaki, Toshiaki,Chatani, Naoto
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experimental part
p. 4866 - 4869
(2009/02/08)
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- Photolytic decarboxylation of α-arylcarboxylic acids mediated by HgF2 under a dioxygen atmosphere
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Mercuric fluoride (HgF2), as a light-sensitive inorganic compound, in the presence of dioxygen is able to convert various α-aryl- and α,α-diarylcarboxylic acids into the corresponding aldehydes and ketones selectively under photoirradiation via trapping of the benzylic radical by O2.
- Farhadi, Saeid,Zaringhadam, Parisa,Sahamieh, Reza Zarei
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p. 1965 - 1968
(2007/10/03)
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- Enantioselective synthesis of (S)-α-arylpropionic acids via Pd-catalyzed kinetic resolution of benzylic alcohols
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A convenient synthetic route for the synthesis of three (S)-α-propionic acids, (5)-naproxen (90% ee), (S)-ibuprofen (82% ee) and (5)-phenylpropionic acid (92% ee) is described. Pd-catalyzed oxidative kinetic resolution of the corresponding benzylic alcohols is used as a key step to introduce stereogenicity into the molecule.
- Thakur, Vinay V.,Sudalai
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p. 557 - 562
(2007/10/03)
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- Acetylation of aromatic compounds over H-BEA zeolite: The influence of the substituents on the reactivity and on the catalyst stability
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The acylation with acetic anhydride of six aromatic substrates with different features (degree of activation of the aromatic ring towards electrophilic substitution, number of rings, i.e., 1 or 2) was carried out in a batch reactor at 373 K over a H-BEA zeolite (Si/Al = 15) with nitrobenzene as a solvent. The acetylation rate was found to be very dependent on the degree of ring activation, with diffusion limitations playing only a limited role. The decrease of the rate with reaction time, which was very pronounced with poorly activated and deactivated substrates, is mainly due to the inhibiting effect of acetic acid and of the products of acetic anhydride condensation.
- Guidotti, Matteo,Canaff, Christine,Coustard, Jean-Marie,Magnoux, Patrick,Guisnet, Michel
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p. 375 - 383
(2007/10/03)
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