- Oxidation of Substituted Phenethyl Alcohols by Sodium-N-chloro-p-toluene sulfonamide: A Kinetic Study
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The kinetics of the oxidation of six p-substituted phenethyl alcohols (PEA, R = H, -Cl, -Br, -CH3, -OCH3, and -NO2) by sodium-N-chloro-p-toluene sulfonamide (chloramine-T, CAT) in the presence of HCl was studied at 35 °C. The rate shows a first order dependence on [CAT]0 and [H+]0 and a fractional order in [PEA]0 and [Cr-]0. Ionic strength variations, addition of reaction product toluene sulfonamide, and variation of the dielectric constant of the medium have no effect on the rate. The solvent isotope effect k′H2O/k′D2O amounts to about 0.90. Proton inventory studies have been made in H2O-D2O mixtures. The rates correlate satisfactorily with Hammett's relationship. The reaction constant ρ was -3.3 for electron releasing substituents and -0.25 for electron withdrawing groups at 35 °C. The activation parameters ΔH#, ΔS#, ΔG#, and logA were derived. ΔH# and ΔS# are linearly related, and an isokinetic relationship is observed with β = 166.7 K, indicating entropy as a controlling factor.
- Ramachandra,Rangappa,Mahadevappa,MadeGowda
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- Magnetically recoverable porphyrin-based nanocatalysts for the effective oxidation of olefins with hydrogen peroxide: A comparative study
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In this paper, preparation, characterization and catalytic applications of metalloporphyrin-based magnetic nanocatalysts were investigated. meso-Tetrakis(4-carboxyphenyl)porphyrinatoiron(iii) chloride (Fe(TCPP)Cl) and meso-tetrakis(4-carboxyphenyl)porphyrinatomanganese(iii) acetate (Mn(TCPP)OAc) were separately immobilized onto the surface of amine functionalized magnetic nanoparticles (Fe3O4/SiO2/NH2) via covalent attachment. The obtained nanocatalysts were characterized using FT-IR and UV-Vis and atomic absorption spectroscopy, X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalytic efficiency of Fe3O4/SiO2/NH2-Fe(TCPP)Cl and Fe3O4/SiO2/NH2-Mn(TCPP)OAc for the green oxidation of alkenes with H2O2 was investigated in a comparative manner. The Mn-porphyrin based magnetic nanocatalyst shows higher catalytic efficiency compared to the Fe-porphyrin. In addition, the prepared magnetic nanocatalyst exhibited excellent reusability and could be reused at least five times without significant leaching or loss of activity. This journal is
- Rayati, Saeed,Moradi, Dana,Nejabat, Fatemeh
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- A practical and mild method for the highly selective conversion of terminal alkenes into aldehydes through epoxidation-isomerization with ruthenium(IV)-porphyrin catalysts
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Aldehydes in excellent yields were obtained from the ruthenium-porphyrin- catalyzed oxidation of various terminal alkenes with 2,6-dichloropyridine N-oxide under mild conditions. The aldehydes generated from these ruthenium-catalyzed alkene oxidations can be used in situ for olefination reactions with ethyl diazoacetate in the presence of PPh3 in a one-pot diazoacetate olefination starting from alkenes (see example).
- Chen, Jian,Che, Chi-Ming
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- Co-N-C catalysts synthesized by pyrolysis of Co-based deep eutectic solvents for aerobic oxidation of alcohols
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The selective oxidation of alcohols to the corresponding aldehydes and ketones is of great importance in the academic and industrial fields. A series of excellent nanostructured catalysts comprising cobalt nanoparticles supported on nitrogen-doped carbon (Co-N-C) were thus prepared by pyrolysis of a deep eutectic solvent Co(NO3)2·6H2O/[Bmim]Br supported on commercial carbon. The catalytic activity of the Co-N-C materials was studied in the selective aerobic oxidation of alcohols with molecular oxygen under base-free conditions. The results indicated that the optimized Co-N-C/700 catalyst exhibited excellent catalytic performance in the selective oxidation of both aryl and alkyl alcohols, giving their corresponding aldehydes and ketones in good to excellent yields. Furthermore, the combination of the catalytic results of the control group and the different characterization methods showed that such high catalytic activity is due to the synergistic interaction between the nitrogen-doped carbon support and Co-N species in Co-N-C/700. In addition, the magnetically recoverable Co-N-C catalyst could be easily separated from the reaction system by using an external magnetic field and reused at least five times without an obvious decrease in the catalytic efficiency.
- Zhao, Xin,Zhou, Yan,Jin, Ai-Ling,Huang, Kuan,Liu, Fujian,Tao, Duan-Jian
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- Mechanistic studies of the oxidation of substituted phenethyl alcohols by N-metallo-N-haloarylsulphonamides: Kinetic isotope studies
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The oxidation of para-substituted phenethyl alcohols (PEA, 2) by N-metallo-N-haloarylsulphonamides (1) in the presence of dilute HCl to the corresponding phenacetaldehydes (4) is first order with respect to oxidant (1) and [H+] and a fract ional order each in [PEA] and [Cl-]. Addition of the reaction product (3), ionic strength variations and variation of dielectric constant of the medium had no effect on the rate. The oxidation of PhCH2CD2OH (2) exhibited a substantial primary kinetic isotope effect (kH/kD=5.83). The rates correlate satisfactorily with the Hammett free energy relationship. The activation parameters ΔH≠, ΔS≠, ΔG≠ and logA were calculated for the i reaction. The proposed mechanism is consistent with the observed results. Copyright
- Rangappa, Kanchugarakoppal S.
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- Biocatalytic Formal Anti-Markovnikov Hydroamination and Hydration of Aryl Alkenes
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Biocatalytic anti-Markovnikov alkene hydroamination and hydration were achieved based on two concepts involving enzyme cascades: epoxidation-isomerization-amination for hydroamination and epoxidation-isomerization-reduction for hydration. An Escherichia coli strain coexpressing styrene monooxygenase (SMO), styrene oxide isomerase (SOI), ω-transaminase (CvTA), and alanine dehydrogenase (AlaDH) catalyzed the hydroamination of 12 aryl alkenes to give the corresponding valuable terminal amines in high conversion (many ≥86%) and exclusive anti-Markovnikov selectivity (>99:1). Another E. coli strain coexpressing SMO, SOI, and phenylacetaldehyde reductase (PAR) catalyzed the hydration of 12 aryl alkenes to the corresponding useful terminal alcohols in high conversion (many ≥80%) and very high anti-Markovnikov selectivity (>99:1). Importantly, SOI was discovered for stereoselective isomerization of a chiral epoxide to a chiral aldehyde, providing some insights on enzymatic epoxide rearrangement. Harnessing this stereoselective rearrangement, highly enantioselective anti-Markovnikov hydroamination and hydration were demonstrated to convert α-methylstyrene to the corresponding (S)-amine and (S)-alcohol in 84-81% conversion with 97-92% ee, respectively. The biocatalytic anti-Markovnikov hydroamination and hydration of alkenes, utilizing cheap and nontoxic chemicals (O2, NH3, and glucose) and cells, provide an environmentally friendly, highly selective, and high-yielding synthesis of terminal amines and alcohols.
- Wu, Shuke,Liu, Ji,Li, Zhi
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- A highly effective green catalyst Ni/Cu bimetallic nanoparticles supported by dendritic ligand for chemoselective oxidation and reduction reaction
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The highly active Ni/Cu bimetallic nanoparticles (NPs) of the different molar ratios of Ni and Cu (1:1, 1:3, 3:1) assisted by dendritic ligand 2,4,6-Tris (di-4-chlorobenzamido)-1,3-diazine were synthesized successfully confirmed by Scanning Electron Microscopy (SEM), Electron Diffraction X-ray (EDX), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM) analysis. These NPs were studied as a heterogeneous catalyst for the chemoselective oxidation of alcohol to the corresponding aldehyde at 30?min and chemoselective reduction of aromatic nitro substituents to the corresponding amino substituents at 20?min, while the Ni/Cu (3:1) NPs were found to be the most effective among other Ni/Cu?(1:1)?and Ni/Cu?(1:3)?NPs at room temperature under mild conditions. The Ni/Cu (3:1) NPs can be recycled for at least five successive runs with no perceptible decrease in catalytic activity. Graphic abstract: [Figure not available: see fulltext.]
- Islam, Md. Sayedul,Khan, Md. Wahab
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- Facile solid-phase synthesis of aliphatic aldehydes using novel polymer-supported phenylselenomethyltrimethylsilane
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Treatment of a novel polymer-supported phenylselenomethyltrimethylsilane reagent with LDA followed by alkylation and oxidative deselenation efficiently afforded aliphatic aldehydes in moderate to good yields with excellent purities. Copyright Taylor & Francis Group, LLC.
- Sheng, Shou-Ri,Wang, Qiu-Ying,Huang, Yi-Xiang,Xin, Qin,Liu, Xiao-Ling
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- Synthesis of a novel six membered CNS palladacycle; TD-DFT study and catalytic activity towards microwave-assisted selective oxidation of terminal olefin to aldehyde
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This article documented synthesis of a Schiff base, E-2-(benzylthio)-N-{(2-methoxynaphthalene-1-yl)methylene}benzenamine (HL) by the treatment of 2-meyhoxynaphthaldehyde and 2-(benzylthio)aniline. Reaction of this synthesized Schiff base with Na2PdCl4has been investigated, which gave a novel six membered Pd(II) complex (PdLCl) through C,N,S-donor atom of Schiff base. These two newly synthesized compounds were characterized by1H NMR, FTIR and UV–Vis spectra and structure of the Pd(II) complex was confirmed by X-ray crystallography. The catalyst (PdLCl) displayed considerable reactivity (up to 99% selectivity and 90% yield) in the selective oxidation of terminal [Formula presented] bond in aryl substituted olefin to aldehyde. The method shows good functional groups compatibility, no ketone byproducts and is operationally simple. Time dependent density functional study (TD-DFT) of representative cyclopalladated complex has been undertaken. The simulated optical spectrum of the complex is in good agreement with the experimentally observed spectrum.
- Sarma, Kuladip,Devi, Namita,Sutradhar, Dipankar,Sarma, Bipul,Chandra, Asit K.,Barman, Pranjit
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- Photocatalytic oxidation of organic compounds in a hybrid system composed of a molecular catalyst and visible light-absorbing semiconductor
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Photocatalytic oxidation of organic compounds proceeded efficiently in a hybrid system with ruthenium aqua complexes as catalysts, BiVO4 as a light absorber, [Co(NH3)5Cl]2+ as a sacrificial electron acceptor and
- Zhou, Xu,Li, Fei,Li, Xiaona,Li, Hua,Wang, Yong,Sun, Licheng
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- Mild oxidation of styrene and its derivatives with ionic manganese porphyrin immobilized in the similarly structured ionic liquid
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Without the auxiliary involvement of axial ligands and organic solvents, the ionic manganese porphyrin 1c immobilized in [BPy][BF4] efficiently catalyzed the oxidation of styrene and its derivatives under mild conditions, affording high activity/oxide selectivity and good stability even after 5 recycling uses. Copyright
- Liu, Ye,Zhang, Hong-Jiao,Cai, Yue-Qin,Wu, Hai-Hong,Liu, Xiu-Li,Lu, Yong
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- Diazo reactions with unsaturated compounds: VII. Vinyl p-methylphenyl and vinyl p-nitrophenyl ethers in the Meerwein reaction
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Vinyl p-methylphenyl ether in aqueous acetone at pH 3-4 in the presence of catalytic amounts of copper(II) chloride reacts with arenediazonium chlorides to form arylacetaldehydes. Vinyl p-nitrophenyl ether under the same conditions fails to react with are
- Naidan,Fesak
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- SeO2-Mediated One-Pot Synthesis of 3-Cyanofurans from 3-Oxo-3-arylpropanenitriles and Substituted Acetaldehydes
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An SeO2-mediated one-pot method was established for the synthesis of 3-cyanofurans from 3-oxo-3-arylpropanenitriles and substituted acetaldehydes. The generality of the reaction was explored, and a plausible mechanism is proposed.
- Zhou, Jie,Zhu, Xinhai,Huang, Manna,Wan, Yiqian
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- Application of an electron-transfer catalyst in light-induced aerobic oxidation of alcohols
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The first heterogeneous photocatalysis system including a bipyridinium-based complex as the electron-transfer catalyst was developed for aerobic oxidation of alcohols without the use of any noble-metal, external N-oxide or peroxide co-oxidant. The current work provides an efficient strategy for alcohol oxidation through a cost-effective, convenient and eco-friendly route.
- Guo, Rui-Yun,Sun, Li,Pan, Xin-Yi,Yang, Xiao-Dong,Ma, Shuai,Zhang, Jie
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- Facile Access to Challenging ortho-Terphenyls via Merging Two Multi-Step Domino Reactions in One-Pot: A Joint Experimental/Theoretical Study
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ortho-Terphenyls are of high interest for medicinal chemistry and materials science, but they are difficult to access. Herein, we demonstrate a straightforward and sustainable synthesis of highly functionalized ortho-terphenyls via joining an organocatalyzed two-step domino reaction (Knoevenagel/vinylogous Michael) with a DABCO/CuBr2 co-catalyzed three-step domino reaction (cyclization/tautomerization/aromatization) in a one-pot process. Overcoming necessity to isolate intermediate products leads to a reduction of energy, costs and waste for a broad scope of reactions. DFT calculations have been performed to investigate the thermodynamics of this one-pot process towards ortho-terphenyls and to study the reaction profile of the vinylogous Michael reaction under inclusion of solvent effects. Role of London dispersion forces in this transformation has been elucidated. It is shown that reaction kinetics and thermodynamics are slightly influenced by dispersion interactions. Furthermore, the addition of dispersion energy donors leads to small changes of reaction energies in some cases.
- Grau, Benedikt W.,B?nisch, Simon,Neuhauser, Alexander,Hampel, Frank,G?rling, Andreas,Tsogoeva, Svetlana B.
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- Synthesis method of phenylacetaldehyde derivative
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The present invention discloses a synthesis method of phenylacetaldehyde derivative, a benzaldehyde derivative is adopted as a raw material, an intermediate 2-methoxyvinylphenyl derivative is obtained through synthesis, then the phenylacetaldehyde derivative is obtained through synthesis, and the substituent group R of the benzaldehyde derivative includes but is not limited to m-methyl, m-ethyl, m-nitrile group, p-methyl, o-methyl, o-nitro and 2, 6-dimethyl. The synthesis process is simple, synthesis conditions are mild, post-treatment is relatively simple, and industrial production is easy; the universality is good, and substrates with different functional groups are compatible; the yield is considerable, part of compounds are almost quantitatively converted, and the requirement of atom economy is met.
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Paragraph 0041; 0046-0047; 0050
(2021/08/07)
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- Kinetic Resolution of Neopentylic Secondary Alcohols by Cu-H-Catalyzed Enantioselective Silylation with Hydrosilanes
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A nonenzymatic kinetic resolution of sterically congested alcohols having a quaternary carbon atom in the β-position is reported. The catalyst system CuCl/NaOtBu/(R,R)-Ph-BPE together with a 3,5-xylyl-substituted tertiary hydrosilane enable enantioselective silylation of the hydroxy group. Several alcohols are obtained with good to excellent selectivity factors, and there are no other known straightforward methods to access these motifs.
- Oestreich, Martin,Papadopulu, Zaneta
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supporting information
p. 438 - 441
(2021/01/13)
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- Rhodium-Catalyzed β-Dehydroborylation of Silyl Enol Ethers: Access to Highly Functionalized Enolates
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An efficient rhodium-catalyzed β-dehydroborylation of aldehyde-derived silyl enol ethers (SEEs) with bis(pinacolato)diboron (B2pin2) is disclosed. The borylation reactions proceeded well with alkyl- and aryl-substituted SEEs, affording a wide array of valuable functionalized β-boryl silyl enolates with high efficiency and excellent stereoselectivity. Moreover, the borylated products, through versatile carbon–boron bond transformations, were readily converted into diverse synthetically useful molecules, including α-hydroxy ketones, functionalized SEEs, and gem-difunctionalized aldehydes.
- Li, Jie,Li, Ruoling,Yang, Wen,Zhao, Pei,Zhao, Wanxiang
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supporting information
p. 9580 - 9585
(2021/12/14)
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- Aerobic epoxidation of styrene over Zr-based metal-organic framework encapsulated transition metal substituted phosphomolybdic acid
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Catalytic epoxidation of styrene with molecular oxygen is regarded as an eco-friendly alternative to producing industrially important chemical of styrene oxide (STO). Recent efforts have been focused on developing highly active and stable heterogeneous catalysts with high STO selectivity for the aerobic epoxidation of styrene. Herein, a series of transition metal monosubstituted heteropolyacid compounds (TM-HPAs), such as Fe, Co, Ni or Cu-monosubstituted HPA, were encapsulated in UiO-66 frameworks (denoted as TM-HPA@UiO-66) by direct solvothermal method, and their catalytic properties were investigated for the aerobic epoxidation of styrene with aldehydes as co-reductants. Among them, Co-HPA@UiO-66 showed relatively high catalytic activity, stability and epoxidation selectivity at very mild conditions (313 K, ambient pressure), that can achieve 82 % selectivity to STO under a styrene conversion of 96 % with air as oxidant and pivalaldehyde (PIA) as co-reductant. In addition, the hybrid composite catalyst can also efficiently catalyze the aerobic epoxidation of a variety of styrene derivatives. The monosubstituted Co atoms in Co-HPA@UiO-66 are the main active sites for the aerobic epoxidation of styrene with O2/PIA, which can efficiently converting styrene to the corresponding epoxide through the activation of the in-situ generated acylperoxy radical intermediate.
- Hu, Dianwen,Song, Xiaojing,Zhang, Hao,Chang, Xinyu,Zhao, Chen,Jia, Mingjun
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- Deoxygenation of Epoxides with Carbon Monoxide
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The use of carbon monoxide as a direct reducing agent for the deoxygenation of terminal and internal epoxides to the respective olefins is presented. This reaction is homogeneously catalyzed by a carbonyl pincer-iridium(I) complex in combination with a Lewis acid co-catalyst to achieve a pre-activation of the epoxide substrate, as well as the elimination of CO2 from a γ-2-iridabutyrolactone intermediate. Especially terminal alkyl epoxides react smoothly and without significant isomerization to the internal olefins under CO atmosphere in benzene or toluene at 80–120 °C. Detailed investigations reveal a substrate-dependent change in the mechanism for the epoxide C?O bond activation between an oxidative addition under retention of the configuration and an SN2 reaction that leads to an inversion of the configuration.
- Maulbetsch, Theo,Jürgens, Eva,Kunz, Doris
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p. 10634 - 10640
(2020/07/30)
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- Synthesis of Arylacetaldehydes by Iridium-Catalyzed Arylation of Vinylene Carbonate with Arylboronic Acids
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The one-step synthesis of arylacetaldehydes by carbon–carbon bond formation between formylmethyl and aryl groups has been realized by the reaction of vinylene carbonate with arylboronic acids in the presence of an iridium/bisphosphine catalyst and a catalytic amount of tetrahydroxydiboron.
- Wang, Zhe,Xue, Fei,Hayashi, Tamio
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supporting information
p. 11054 - 11057
(2019/07/17)
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- α-Amino Diphenyl Phosphonates as Novel Inhibitors of Escherichia coli ClpP Protease
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Increased Gram-negative bacteria resistance to antibiotics is becoming a global problem, and new classes of antibiotics with novel mechanisms of action are required. The caseinolytic protease subunit P (ClpP) is a serine protease conserved among bacteria that is considered as an interesting drug target. ClpP function is involved in protein turnover and homeostasis, stress response, and virulence among other processes. The focus of this study was to identify new inhibitors of Escherichia coli ClpP and to understand their mode of action. A focused library of serine protease inhibitors based on diaryl phosphonate warheads was tested for ClpP inhibition, and a chemical exploration around the hit compounds was conducted. Altogether, 14 new potent inhibitors of E. coli ClpP were identified. Compounds 85 and 92 emerged as most interesting compounds from this study due to their potency and, respectively, to its moderate but consistent antibacterial properties as well as the favorable cytotoxicity profile.
- Moreno-Cinos, Carlos,Sassetti, Elisa,Salado, Irene G.,Witt, Gesa,Benramdane, Siham,Reinhardt, Laura,Cruz, Cristina D.,Joossens, Jurgen,Van Der Veken, Pieter,Br?tz-Oesterhelt, Heike,Tammela, P?ivi,Winterhalter, Mathias,Gribbon, Philip,Windshügel, Bj?rn,Augustyns, Koen
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p. 774 - 797
(2019/01/30)
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- Copper-Catalyzed Ring-Opening/Reconstruction of Anthranils with Oxo-Compounds: Synthesis of Quinoline Derivatives
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A copper-catalyzed protocol for the construction of various 2-aryl(alkyl)-3-acylquinolines or 3-arylquinolines using readily available anthranils and 1,3-diketones or aldehydes as starting materials is reported herein. Dioxygen as the sole oxidant and hexafluoroisopropanol as the solvent play an important role in both procedures. This ring-opening/reconstruction strategy involving N-O bond cleavage and C-N/C-C bond formation features high yields and broad substrate scope.
- Zou, Liang-Hua,Zhu, Hao,Zhu, Shuai,Shi, Kai,Yan, Cheng,Li, Ping-Gui
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p. 12301 - 12313
(2019/10/11)
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- Peroxygenase-Catalysed Epoxidation of Styrene Derivatives in Neat Reaction Media
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Biocatalytic oxyfunctionalisation reactions are traditionally conducted in aqueous media limiting their production yield. Here we report the application of a peroxygenase in neat reaction conditions reaching product concentrations of up to 360 mM.
- Alcalde, Miguel,Arends, Isabel W. C. E.,Hollmann, Frank,Paul, Caroline E.,Rauch, Marine C. R.,Tieves, Florian
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- Tetradentate amido azo Schiff base Cu(II), Ni(II) and Pd(II) complexes: Synthesis, characterization, spectral properties, and applications to catalysis in C–C coupling and oxidation reaction
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New Schiff base ligands (H2L1 & H2L2) were synthesized by the reaction of salicylaldehyde with (2-((2-aminophenyl)diazenyl)-N-alkylaniline), and were used for the preparation of complexes with Cu(II), Ni(II) and Pd(II) metal ions. The structural features of the synthesized compounds were examined by UV–Vis, IR and 1H NMR spectroscopy. The crystal structures of Schiff base (H2L1) and two metal complexes Cu(L1) and Ni(L2) were determined by single crystal X-ray diffraction. The studies revealed that the synthesized Schiff bases existed as tetradentate (N,N,N,O) ligands and bonded to the metal ions through the donor atoms of the amido nitrogen, azo nitrogen, azomethine nitrogen and phenolic oxygen atoms. The redox property of Cu(L1) and Ni(L1) and emission behavior of ligand H2L1 and complexes Cu(L1) and Ni(L1) were examined. The complex Cu(L1) shows excellent catalytic activity towards oxidation of benzyl alcohol to benzyldehyde (under solvent-free condition) using H2O2 as the oxidant. Complex Pd(L1) acts as highly efficient catalyst in the Suzuki–Miyaura cross-coupling reaction of various aryl halides with phenyl boronic acid to produce the corresponding biaryls with high yields under mild reaction conditions. Both the catalysts Cu(L1) and Pd(L1) were easily recovered by simple chromatographic separation and reused for next catalytic cycle.
- Pratihar, Jahar Lal,Mandal, Paritosh,Lai, Chung Kung,Chattopadhyay, Surajit
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p. 317 - 324
(2019/02/06)
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- Regio- and chemoselective rearrangement of terminal epoxides into methyl alkyl and aryl ketones
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The development of the highly active pincer-type rhodium catalyst 2 for the nucleophilic Meinwald rearrangement of functionalised terminal epoxides into methyl ketones under mild conditions is presented. An excellent regio- and chemoselectivity is obtained for the first time for aryl oxiranes.
- Tian, Yingying,Jürgens, Eva,Kunz, Doris
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p. 11340 - 11343
(2018/10/31)
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- Berberine derivative and use thereof
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The invention discloses a berberine derivative for treating bacterium infection, and a use for thereof. The berberine derivative has a structure shown in the description. Experiments prove that the berberine derivative has positive ion charges under physiological conditions, and has the characteristics of broad antibacterial spectrum, good biocompatibility, good water solubility, strong targetingand low toxicity, a preparation method has the advantages of simplicity, easiness in implementing, high yield, and significant curative effect in the antibacterial field.
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Paragraph 0052; 0105-0106
(2018/06/15)
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- Synthesis of Substrates for Aldolase-Catalysed Reactions: A Comparison of Methods for the Synthesis of Substituted Phenylacetaldehydes
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Methods for the synthesis of phenylacetaldehydes (oxidation, one-carbon chain extension) were compared by using the synthesis of 4-methoxyphenylacetaldehyde as a model example. Oxidations of 4-methoxyphenylethanol with activated DMSO (Swern oxidation) or manganese dioxide gave unsatisfactory results; whereas oxidation with 2-iodoxybenzoic acid (IBX) produced 4-methoxyphenylacetaldehyde in reasonable (75%) yield. However, Wittig-type one-carbon chain extension with methoxymethylene-triphenylphosphine followed by hydrolysis gave an excellent (81% overall) yield of 4-methoxyphenylacetaldehyde from 4-methoxybenzaldehyde (a cheap starting material). This approach was subsequently used to synthesise a set of 10 substituted phenylacetaldehydes in good to excellent yields.
- Al-Smadi, Derar,Enugala, Thilak Reddy,Norberg, Thomas,Kihlberg, Jan,Widersten, Mikael
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supporting information
p. 1187 - 1190
(2018/03/26)
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- One-Pot Preparation of C1-Homologated Aliphatic Nitriles from Aldehydes through a Wittig Reaction under Metal-Cyanide-Free Conditions
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A one-pot protocol to obtain C1-homologated aliphatic nitriles was achieved by treating aromatic and aliphatic aldehydes with the (methoxymethyl)triphenylphosphonium ylide followed by hydrolysis of the resulting methyl vinyl ethers with pTsOH (Ts = para-toluenesulfonyl) and treatment with molecular iodine and aqueous ammonia under metal cyanide free conditions. Neopentyl-type nitriles, which could not be obtained by conventional methods that involved conversion of the neopentyl alcohol into a tosylate and treatment with metal cyanide, were successfully obtained by using the present method.
- Ezawa, Masatoshi,Togo, Hideo
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p. 2379 - 2384
(2017/05/01)
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- Coupling molecular and nanoparticle catalysts on single metal?organic framework microcrystals for the tandem reaction of H2O2 generation and selective alkene oxidation
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A molecular catalyst, (sal)MoVI, and a heterogeneous catalyst, either Pd or Au nanoparticles (NPs), were integrated into one UiO-66 MOF microcrystal. The resulting dually functionalized catalysts, Pd@UiO-66-(sal)Mo and Au/UiO-66-(sal)Mo, have been utilized for a one-pot tandem reaction of H2O2 generation and selective liquid-phase alkene oxidation. The NPs serve as catalysts for the production of H2O2 from H2 and O2 gases, while the (sal)Mo moieties function as the oxidation catalyst. When the metal NPs are fully encapsulated within the MOF microcrystals, the alkene hydrogenation side reaction is largely suppressed, with a 6-fold decrease in the hydrogenation/oxidation product ratio for 5-bromo-1-cyclooctene favoring the epoxide as the major product. For Au/UiO-66-(sal)Mo, where the two catal sts are in close roximit on the MOF microcr stal the enhancement in oxidation productivity is increased by 10 times in comparison to the [Au/UiO-66-NH2 + UiO-66-sal(Mo)] physical mixture of the two singly functionalized MOFs.
- Limvorapitux, Rungmai,Chou, Lien-Yang,Young, Allison P.,Tsung, Chia-Kuang,Nguyen, SonBinh T.
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p. 6691 - 6698
(2017/11/09)
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- Carbon nitride assisted chemoselective C-H bond photo-oxidation of alkylphenolethoxylates in water medium
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The unprecedented ability of g-C3N4 to chemoselectively photo-oxidise the methyl group of 2-(4-methylphenoxy)ethanol instead of the easily oxidised oxyethanol fragment has been demonstrated. When g-C3N4 is treat
- Ilkaeva,Krivtsov,Bartashevich,Khainakov,García,Díaz,Ordó?ez
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supporting information
p. 4299 - 4304
(2017/09/29)
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- Maleimide-assisted anti-Markovnikov Wacker-type oxidation of vinylarenes using molecular oxygen as a terminal oxidant
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Arylacetaldehydes were successfully synthesized by the anti-Markovnikov Wacker-type oxidation of vinylarenes using 1 atm O2 as a terminal oxidant under mild conditions. Electron-deficient alkenes, such as maleic anhydride and maleimides, were effective additives and would operate as ligands to stabilize the Pd(0) species during the reaction.
- Nakaoka, Sonoe,Murakami, Yuka,Kataoka, Yasutaka,Ura, Yasuyuki
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supporting information
p. 335 - 338
(2016/01/09)
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- Synthesis and Catalytic Properties of New Metalloporphyrin-Based Porous Organic Framework Materials with Single and Accessible Sites
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It is a big challenge to homogenize heterogeneous catalysts with molecular catalytic performance. With this target in mind, herein, we describe a facile strategy for direct incorporation of single catalytic sites in 3D open porous aromatic frameworks (PAFs). The synthesis of the PAF (denoted as PAF-76) as well as its derivatives (PAF-76-M, M=Fe, Mn, Zn) was achieved by the use of tetrakis(4-bromophenyl)methane as tetrahedral nodes and tetrakis(4-bromophenyl)porphyrin as planar nodes. The connection of monomers into an extended network of PAF-76 was monitored by 13C NMR and FTIR spectroscopies. The prepared PAF-76s showed 3D porous structures with surface areas of 450–700 m2 g?1, pore volumes of 0.3–0.4 cm3 g?1, and pore sizes around 1.2 nm. The direct incorporation of metalloporphyrin components into the PAF-76-M frameworks has allowed the uniform distribution of metal ionic sites throughout the PAF-76-M particles. The combined merits of isolated metal sites and suitable pore size make PAF-76 a good candidate for heterogeneous catalysis. The catalytic performances of the porphyrin/metalloporphyrin-based active sites in the PAF-76s were evaluated by aerobic oxidation reactions of styrene, which are usually carried out with homogeneous systems. Metal-functionalized PAF-76s (PAF-76-M) exhibit enhanced turnover frequencies for styrene conversion (16.9–50.9 mol mol(M)?1 h?1) compared with molecular catalysts (0–35.0 mol mol(M)?1 h?1), and improved selectivity toward phenylacetaldehyde (85.7–99 %) in contrast to their corresponding monomers (0–75.5 %). The robustness of PAF-76 in terms of high thermal stability, good recyclability, and excellent solvent resistance showed that these PAF-76 materials hold great promise for developing heterogeneous catalysts.
- Meng, Shuang,Zou, Xiaoqin,Liu, Chuanfang,Ma, Heping,Zhao, Nian,Ren, Hao,Jia, Mingjun,Liu, Jia,Zhu, Guangshan
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p. 2393 - 2400
(2016/07/28)
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- Anti-Markovnikov Oxidation of β-Alkyl Styrenes with H2O as the Terminal Oxidant
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Oxygenation of alkenes is one of the most straightforward routes for the construction of carbonyl compounds. Wacker oxidation provides a broadly useful strategy to convert the mineral oil into higher value-added carbonyl chemicals. However, the conventional Wacker chemistry remains problematic, such as the poor activity for internal alkenes, the lack of anti-Markovnikov regioselectivity, and the high cost and chemical waste resulted from noble metal catalysts and stoichiometric oxidant. Here, we describe an unprecedented dehydrogenative oxygenation of β-alkyl styrenes and their derivatives with water under external-oxidant-free conditions by utilizing the synergistic effect of photocatalysis and proton-reduction catalysis that can address these challenges. This dual catalytic system possesses the single anti-Markovnikov selectivity due to the property of the visible-light-induced alkene radical cation intermediate.
- Zhang, Guoting,Hu, Xia,Chiang, Chien-Wei,Yi, Hong,Pei, Pengkun,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 12037 - 12040
(2016/09/28)
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- Hypoiodite-catalyzed regioselective oxidation of alkenes: An expeditious access to aldehydes in aqueous micellar media
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A highly anti-Markovnikov selective oxidation of alkenes based on in situ generated hypoiodite catalysis in aqueous micellar media under mild conditions has been described. This novel catalytic system realizes an efficient synthesis of aldehydes from alkenes in an economically viable and environmentally safe fashion. The preliminary mechanistic studies suggest that the reaction proceeds via tandem iodofunctionalization/1,2-aryl or alkyl migration. The scope and limitations of this tandem process are demonstrated with various mono- and disubstituted (terminal and internal) olefins.
- Swamy, Peraka,Reddy, Marri Mahender,Naresh, Mameda,Kumar, Macharla Arun,Srujana, Kodumuri,Durgaiah, Chevella,Narender, Nama
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p. 1125 - 1130
(2015/04/22)
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- Synthesis of 3-Arylpyridines via Palladium/Copper-Catalyzed Annulation of Allylamine/1,3-Propanediamine and Aldehydes
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A novel and efficient method for the synthesis of 3-arylpyridines from allylamine/propanediamine and aldehydes by palladium/copper-catalyzed oxidative tandem cyclization has been developed. With this reaction, a series of desired 3-arylpyridines was synthesized in moderate yields via C-C/C-N bond formation and 6-endo/exo-trig cyclization.
- Yang, Xiaodong,Yang, Shenghua,Xiang, Likui,Pang, Xiaobo,Chen, Baohua,Huang, Guosheng,Yan, Rulong
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p. 3732 - 3736
(2016/01/25)
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- DDQ-mediated Direct C(sp3)-H Cyanation of Benzyl Ethers and 1,3-Diarylpropenes under Solvent- and Metal-free Conditions
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A direct cyanation of benzyl ethers and 1,3-diarylpropenes with TMSCN was performed under solvent- and metal-free conditions. This oxidative cross dehydrative coupling (CDC) reaction was promoted by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and provided rapid access to a broad range of nitriles in good to excellent yields.
- Kong, Shanshan,Zhang, Lingqiong,Dai, Xiaoli,Tao, Lianzhi,Xie, Chunsong,Shi, Lei,Wang, Min
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supporting information
p. 2453 - 2456
(2015/08/18)
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- Homogeneous catalytic oxidation of styrene and styrene derivatives with hydrogen peroxide in the presence of transition metal-substituted polyoxotungstates
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The tetrabutylammonium (TBA) salts of the Keggin-type polyoxotungstates with general formula [XW11M(H2O)O39](n-m)-, where X = P, B or Si and M = Mn, Fe or Co, were evaluated as catalysts in the oxidation of styrene, α-methylstyrene, p-methylstyrene, α,p-dimethylstyrene, p-chlorostyrene, p-nitrostyrene, and p-methoxystyrene under mild conditions, using aqueous H2O2 as an eco-sustainable oxidant. In this study, the influence of the catalysts and of the different styrene substituents on the oxidation reaction profile was evaluated in terms of conversion and selectivity. For all the performed catalytic studies, the main product results from the oxidative cleavage of the vinyl double bond, except in the case of the oxidation of p-methoxystyrene catalysed by BW11Mn, for which p-methoxyphenol is the main product. The catalysts BW11Mn and SiW11Co give rise to 100% conversion for almost all of the substrates, excluding p-methoxystyrene and p-nitrostyrene for both catalysts and α,p-dimethylstyrene only in the case of BW11Mn. The selectivity for C=C cleavage products resulting from the oxidative cleavage of the vinyl double bond can be as high as 98%, reaching 98% conversion for p-nitrostyrene when SiW11Co was used as a catalyst. Possible pathways are discussed and the oxidation of a few presumed intermediates was carried out. The systematic study of several substituted styrene derivatives suggests a possible reactivity order for these compounds in the catalytic system considered.
- Duarte, Tiago A. G.,Estrada, Ana C.,Simes, Mrio M. Q.,Santos, Isabel C. M. S.,Cavaleiro, Ana M. V.,Neves, M. Graca P. M. S.,Cavaleiro, Jos A. S.
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p. 351 - 363
(2015/02/18)
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- Catalysed anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant
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Anti-Markovnikov oxidation of terminal aryl alkenes to aldehydes and transformation of N-methyl aryl tertiary amines to formamides with H2O2 as a terminal oxidant under mild conditions have been achieved with moderate to good product yields using [FeIII(TF4DMAP)OTf] as catalyst. This journal is
- Du, Yi-Dan,Tse, Chun-Wai,Xu, Zhen-Jiang,Liu, Yungen,Che, Chi-Ming
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supporting information
p. 12669 - 12672
(2015/05/20)
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- Broad-spectrum catalysts for the ambient temperature anti-Markovnikov hydration of alkynes
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Anti-Markovnikov alkyne hydration provides a valuable route to aldehydes. Half-sandwich ruthenium complexes ligated by 5,5′-bis(trifluoromethyl)-2, 2′-bipyridine are remarkably active for this transformation. In the presence of 2 mol % metal, a wide range of functionalized aliphatic and aromatic alkynes are hydrated in high yield at ambient temperature. Alkyne hydration: Half-sandwich ruthenium complexes derived from 5,5′-bis(trifluoromethyl)- 2,2′-bipyridine show a high activity for the anti-Markovnikov hydration of terminal alkynes (see picture). A wide array of alkynes are efficiently hydrated to aldehydes using 2 mol % metal loadings at 25 °C within 8-24 h.
- Li, Le,Zeng, Mingshuo,Herzon, Seth B.
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supporting information
p. 7892 - 7895
(2014/08/05)
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- A straightforward organocatalytic alkylation of 2-arylacetaldehydes: An approach towards bisabolanes
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A highly stereoselective organocatalytic aalkylation of 2-arylacetaldehydes with a commercially available carbenium tetrafluoroborate is described. The stereoselective alkylation was carried out in acetonitrile/ water, under air in the presence of a commercially available imidazolidinone (MacMillan's catalyst). Key intermediates for the synthesis of bisabolanes were obtained through a simple chemistry. In particular a direct, enantioselective and facile synthesis of (R)-(-)-curcumene is described.
- Gualandi, Andrea,Canestrari, Pietro,Emer, Enrico,Cozzi, Pier Giorgio
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supporting information
p. 528 - 536
(2014/05/20)
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- Unusually Broad Substrate Profile of Self-Sufficient Cytochrome P450 Monooxygenase CYP116B4 from Labrenzia aggregata
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A new member of the CYP116B subfamily - P450LaMO - was discovered in Labrenzia aggregata by genomic data mining. It was successfully overexpressed in Escherichia coli, purified, and subsequently characterized spectroscopically, and its catalytic properties were assessed. Substrate profiling of the P450LaMO revealed that it was a versatile catalyst, exhibiting hydroxylation and epoxidation activities as well as O-dealkylation and asymmetric sulfoxidation activities. Diverse compounds, including alkylbenzenes, aromatic bicyclic molecules, and terpenoids, were shown to be hydroxylated by P450LaMO. Such diverse catalytic activities are uncommon for the bacterial P450s, and the P450LaMO -mediated stereoselective hydroxylation of inactivated C - H bonds - ubiquitous and relatively unreactive in organic molecules - is particularly unusual. The self-sufficient nature of P450LaMO, coupled with its broad substrate range, highlights it as an ideal template for directed evolution towards various applications.
- Yin, Yue-Cai,Yu, Hui-Lei,Luan, Zheng-Jiao,Li, Ren-Jie,Ouyang, Peng-Fei,Liu, Jing,Xu, Jian-He
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p. 2443 - 2449
(2015/03/03)
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- Unusually Broad Substrate Profile of Self-Sufficient Cytochrome P450 Monooxygenase CYP116B4 from Labrenzia aggregata
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A new member of the CYP116B subfamily - P450LaMO - was discovered in Labrenzia aggregata by genomic data mining. It was successfully overexpressed in Escherichia coli, purified, and subsequently characterized spectroscopically, and its catalytic properties were assessed. Substrate profiling of the P450LaMO revealed that it was a versatile catalyst, exhibiting hydroxylation and epoxidation activities as well as O-dealkylation and asymmetric sulfoxidation activities. Diverse compounds, including alkylbenzenes, aromatic bicyclic molecules, and terpenoids, were shown to be hydroxylated by P450LaMO. Such diverse catalytic activities are uncommon for the bacterial P450s, and the P450LaMO -mediated stereoselective hydroxylation of inactivated C-H bonds - ubiquitous and relatively unreactive in organic molecules - is particularly unusual. The self-sufficient nature of P450LaMO, coupled with its broad substrate range, highlights it as an ideal template for directed evolution towards various applications.
- Yin, Yue-Cai,Yu, Hui-Lei,Luan, Zheng-Jiao,Li, Ren-Jie,Ouyang, Peng-Fei,Liu, Jing,Xu, Jian-He
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p. 2443 - 2449
(2015/08/24)
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- Selective reduction of esters to aldehydes under the catalysis of well-defined NHC-iron complexes
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On a direct course to the aldehyde: Hydrosilylation catalyzed by a well-defined N-heterocyclic-carbene-iron complex under UV irradiation enabled the selective reduction of esters to aldehydes (see scheme; Bn=benzyl, Mes=mesityl). The low catalyst loading and very mild reaction conditions make this chemoselective transformation a promising alternative to the reduction of esters with diisobutylaluminum hydride. Copyright
- Li, Haoquan,Misal Castro, Luis C.,Zheng, Jianxia,Roisnel, Thierry,Dorcet, Vincent,Sortais, Jean-Baptiste,Darcel, Christophe
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p. 8045 - 8049
(2013/08/23)
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- Indium-catalyzed annulation of 3-aryl- and 3-heteroarylindoles with propargyl ethers: Synthesis and photoluminescent properties of aryl- and heteroaryl[c]carbazoles
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Treatment of 3-aryl- and 3-heteroarylindoles with propargyl ethers under indium catalysis successfully provided aryl- and heteroaryl[c]carbazoles, which were found to be more efficient emitters compared with the corresponding [a]-analogs.
- Nagase, Yuta,Shirai, Hiroyuki,Kaneko, Masayoshi,Shirakawa, Eiji,Tsuchimoto, Teruhisa
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supporting information
p. 1456 - 1459
(2013/05/08)
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- A continuous flow solution to achieving efficient aerobic anti-Markovnikov Wacker oxidation
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An aerobic anti-Markovnikov Wacker oxidation for the flow-synthesis of arylacetaldehydes is reported. In the process, flow chemistry techniques have provided a means to control and minimise the over-oxidation of sensitive products. The reaction showed general applicability to various functionalised styrenes and provided a process capable of a multi-gram scale. Copyright
- Bourne,Ley
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supporting information
p. 1905 - 1910
(2013/08/23)
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- An iron catalyzed regioselective oxidation of terminal alkenes to aldehydes
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Fe(BF4)2·6H2O with pyridine-2,6-dicarboxylic acid and PhIO can efficiently catalyze the regioselective oxidation of terminal alkene derivatives to aldehydes under mild and benign reaction conditions.
- Chowdhury, Abhishek Dutta,Ray, Ritwika,Lahiri, Goutam Kumar
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supporting information; experimental part
p. 5497 - 5499
(2012/07/01)
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- FeCl3?6H2O-catalyzed alkenylation of indoles with aldehydes
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FeCl3?6H2O-catalyzed efficient C3-alkenylation of indoles was realized through the condensation of aldehydes and indole derivatives in the presence of 2 equiv of ethanol at ambient temperature, forming 3- vinylindoles in up to 93% yields. Ethanol promoted formation of the desired products. An obvious solvent effect was observed, and bisindoles were identified as the reaction intermediates.
- Yang, Qin,Wang, Liandi,Guo, Tenglong,Yu, Zhengkun
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p. 8355 - 8361
(2013/01/15)
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- Regioselective synthesis of substituted naphthalenes and phenanthrenes by FeCl3-promoted annulation of aryl and naphthyl acetaldehydes with alkynes
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The FeCl3-promoted annulation reaction of aryl acetaldehydes with alkynes has been established, which provides a new and versatile straightforward procedure for the regioselective synthesis of mono-, di-, and polysubstituted naphthalenes under mild conditions. Interestingly, the present catalytic system not only differentiates between internal and terminal alkynes but also shows unprecedented complete Me3SiOH elimination selectivity for silyl alkyne substrates. Furthermore, the synthesis of a series of substituted phenanthrenes via reactions of nathphyl acetaldehydes with internal alkynes is also achieved for the first time in good yields with excellent regioselectivity.
- Bu, Xiuli,Hong, Longcheng,Liu, Ruiting,Hong, Jianquan,Zhang, Zhengxing,Zhou, Xigeng
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p. 7960 - 7965
(2012/09/21)
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- The catalytic potential of Coptis japonica NCS2 revealed - Development and utilisation of a fluorescamine-based assay ETI
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The versatility and potential of a norcoclaurine synthase (NCS) from Coptis japonica NCS2 has been investigated, together with the development and application of a novel fluorescence-based high-throughput assay using nearly forty amines/aldehydes. The stereocontrol exerted by CjNCS2 on selected non-natural substrates has been determined, where the tetrahydroisoquinolines (THIAs) were formed as the (1S)-isomer in >95% ee, as observed with the natural product norcoclaurine. Docking calculations involving THIA mechanism intermediates, utilising the reported Thalictrum flavum NCS X-ray crystallographic structure, were carried out and combined with the CjNCS2 screening results to further understand the mode of action of NCS. These findings suggested that in addition to the key active-site residues K122 and E110, D141 is also mechanistically essential for the enzymatic transformation. The exceptional tolerance of NCS towards aldehyde substrates is furthermore supported by our proposed mechanism in which the aldehydes protrude out of the enzymatic pocket. Copyright
- Pesnot, Thomas,Gershater, Markus C.,Ward, John M.,Hailes, Helen C.
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supporting information
p. 2997 - 3008
(2013/01/15)
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- Biocatalytic production of tetrahydroisoquinolines
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The promiscuity of the enzyme norcoclaurine synthase is described. This biocatalyst yielded a diverse array of substituted tetrahydroisoquinolines by cyclizing dopamine with various acetaldehydes in a Pictet-Spengler reaction. This enzymatic reaction may provide a biocatalytic route to a range of tetrahydroisoquinoline alkaloids.
- Ruff, Bettina M.,Br?se,O'Connor, Sarah E.
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supporting information; experimental part
p. 1071 - 1074
(2012/03/27)
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- Selective switchable iron-catalyzed hydrosilylation of carboxylic acids
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Selective reduction of carboxylic acids either to aldehydes or alcohols is achieved using a one pot procedure based on iron-catalyzed hydrosilylations. Using phenylsilane and (COD)Fe(CO)3 catalyst under UV-irradiation at rt, alcohols were obtained specifically in good yields, whereas aldehydes were selectively obtained using TMDS and (t-PBO)Fe(CO)3 catalyst under thermal activation.
- Misal Castro, Luis C.,Li, Haoquan,Sortais, Jean-Baptiste,Darcel, Christophe
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supporting information
p. 10514 - 10516,3
(2020/09/02)
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- Enantioselective water-soluble iron-porphyrin-catalyzed epoxidation with aqueous hydrogen peroxide and hydroxylation with iodobenzene diacetate
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The asymmetric epoxidation of styrene derivatives by H2O 2 (or UHP) to give optically active epoxides (ee up to 81%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 78%) were carried out in methanol and water using chiral water-soluble iron porphyrins as catalysts.
- Maux, Paul Le,Srour, Hassan F.,Simonneaux, Gérard
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experimental part
p. 5824 - 5828
(2012/09/11)
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- Selective oxidation of terminal aryl and aliphatic alkenes to aldehydes catalyzed by iron(iii) porphyrins with triflate as a counter anion
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[Fe(Por)CF3SO3] (Por = porphyrin dianion) can efficiently catalyze selective oxidation of terminal aryl alkenes and aliphatic alkenes to aldehydes in good to high yields under mild conditions.
- Chen, Guo-Qiang,Xu, Zhen-Jiang,Zhou, Cong-Ying,Che, Chi-Ming
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supporting information; experimental part
p. 10963 - 10965
(2011/11/06)
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- Bulky and modular 3,3′-bipyrazoles as ligands: Synthesis, characterization, and catalytic activity of Pd complexes
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In the present study, the properties of a new bidentate N,N′-chelating ligand class that bears an electron-excessive 3,3′-bipyrazole core have been investigated. The ligands are easily accessible in a three-step procedure by condensation with diethyl oxalate followed by tandem condensation with hydrazine hydrate and finally by aryl- or alkylation exclusively at the N-1,1′-pyrazole positions to furnish overall eleven new ligands with different electronic properties. After structural analysis of the ligands, their coordination to palladium, copper, and cobalt has been studied. These ligands coordinate the 2,2′-pyrazolyl nitrogen atoms in a bidentate fashion to the metals to realize complexes with an (L)MX 2 motif. We present two crystal structures of Pd and Cu complexes, which to the best of our knowledge represent the first d8 and d 9 2,2′-bipyrazole compounds coordinated through bidentate complexation. Initial catalytic experiments have been performed with palladium complexes with three bipyrazole ligands of this new class; the palladium-catalyzed copper-free Wacker oxidation of different alkenes showed superior activity compared to 2,2′-bipyridines. We attribute this to a higher redox potential of the 3,3′-bipyrazoles, which are- besides electronic effects- also strongly influenced by steric effects. These might be enforced by the extended ligand backbone, the choice of the wingtip substitution, and the smaller coordination cavity within the N 2,N2′ atoms compared to 2,2′-bipyridine ligands. A sterically bulky 3,3′-bipyrazole ligand class was synthesized in excellent yields using camphor as a building block. The highly modular nature of the system gave rise to a series of 11 new ligands with tunable steric and electronic properties. The derived catalysts with increasing electron-donating properties revealed higher conversions in Cu-free Wacker oxidations of terminal alkenes.
- Spallek, Markus J.,Stockinger, Skrollan,Goddard, Richard,Rominger, Frank,Trapp, Oliver
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experimental part
p. 5014 - 5024
(2012/01/14)
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