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https://www.readbyqxmd.com/read/28339213/quaternary-carbon-center-forming-formal-3-3-cycloaddition-reaction-via-bifunctional-catalysis-asymmetric-synthesis-of-spirocyclohexene-pyrazolones
#1
Jin-Yu Liu, Jing Zhao, Jia-Lu Zhang, Peng-Fei Xu
A variety of spirocyclohexene pyrazolones were synthesized in good yields with excellent stereoselectivities through an asymmetric, intermolecular, quaternary carbon center forming [3 + 3] cycloaddition reaction catalyzed by a bifunctional catalyst. The vinylogous pyrazolones used as binucleophilic synthons in this reaction exhibited superior ability for constructing pyrazolone related spirocyclic scaffolds.
March 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28339184/mxene-ti3c2-an-effective-2d-light-to-heat-conversion-material
#2
Renyuan Li, Lianbin Zhang, Le Shi, Peng Wang
MXene, a new series of 2D material, has been steadily advancing its applications to a variety of fields, such as catalysis, supercapacitor, molecular separation, electromagnetic wave interference shielding. This work reports a carefully designed aqueous droplet light heating system along with a thorough mathematical procedure, which combined leads to a precise determination of internal light-to-heat conversion efficiency of a variety of nanomaterials. The internal light-to-heat conversion efficiency of MXene, more specifically Ti3C2, was measured to be 100%, indicating a perfect energy conversion...
March 24, 2017: ACS Nano
https://www.readbyqxmd.com/read/28335364/nickel-based-electrospun-materials-with-tuned-morphology-and-composition
#3
Giorgio Ercolano, Filippo Farina, Sara Cavaliere, Deborah J Jones, Jacques Rozière
Nickel is set to play a crucial role to substitute the less-abundant platinum in clean electrochemical energy conversion and storage devices and catalysis. The controlled design of Ni nanomaterials is essential to fine-tune their properties to match these applications. A systematic study of electrospinning and thermal post-treatment parameters has been performed to synthesize Ni materials and tune their morphology (fibers, ribbons, and sponge-like structures) and composition (metallic Ni, NiO, Ni/C, Ni₃N and their combinations)...
December 6, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28335316/polymer-nanocomposite-film-with-metal-rich-surface-prepared-by-in-situ-single-step-formation-of-palladium-nanoparticles-an-interesting-way-to-combine-specific-functional-properties
#4
David Thompson, David Kranbuehl, Eliane Espuche
This paper presents a continuous single-step route that permits preparation of a thermostable polymer/metal nanocomposite film and to combine different functional properties in a unique material. More precisely, palladium nanoparticles are in situ generated in a polyimide matrix thanks to a designed curing cycle which is applied to a polyamic acid/metal precursor solution cast on a glass plate. A metal-rich surface layer which is strongly bonded to the bulk film is formed in addition to homogeneously dispersed metal nanoparticles...
October 18, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28335250/nanoparticles-for-catalysis
#5
EDITORIAL
Sergio Navalón, H García
Nanoscience emerged in the last decades of the 20th century with the general aim to determine those properties that appear when small particles of nanometric dimensions are prepared and stabilized.[...].
June 23, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28335236/complex-morphology-metal-based-nanostructures-fabrication-characterization-and-applications
#6
REVIEW
Antonella Gentile, Francesco Ruffino, Maria Grazia Grimaldi
Due to their peculiar qualities, metal-based nanostructures have been extensively used in applications such as catalysis, electronics, photography, and information storage, among others. New applications for metals in areas such as photonics, sensing, imaging, and medicine are also being developed. Significantly, most of these applications require the use of metals in the form of nanostructures with specific controlled properties. The properties of nanoscale metals are determined by a set of physical parameters that include size, shape, composition, and structure...
June 6, 2016: Nanomaterials
https://www.readbyqxmd.com/read/28334877/iron-mediates-catalysis-of-nucleic-acid-processing-enzymes-support-for-fe-ii-as-a-cofactor-before-the-great-oxidation-event
#7
C Denise Okafor, Kathryn A Lanier, Anton S Petrov, Shreyas S Athavale, Jessica C Bowman, Nicholas V Hud, Loren Dean Williams
Life originated in an anoxic, Fe2+-rich environment. We hypothesize that on early Earth, Fe2+ was a ubiquitous cofactor for nucleic acids, with roles in RNA folding and catalysis as well as in processing of nucleic acids by protein enzymes. In this model, Mg2+ replaced Fe2+ as the primary cofactor for nucleic acids in parallel with known metal substitutions of metalloproteins, driven by the Great Oxidation Event. To test predictions of this model, we assay the ability of nucleic acid processing enzymes, including a DNA polymerase, an RNA polymerase and a DNA ligase, to use Fe2+ in place of Mg2+ as a cofactor during catalysis...
March 15, 2017: Nucleic Acids Research
https://www.readbyqxmd.com/read/28334525/indium-catalyzed-regioselective-%C3%AE-alkylation-of-pyrroles-with-carbonyl-compounds-and-hydrosilanes-and-its-application-to-constructing-a-quaternary-carbon-center-with-a-%C3%AE-pyrrolyl-group
#8
Shota Nomiyama, Takahiro Ogura, Hiroaki Ishida, Kazuki Aoki, Teruhisa Tsuchimoto
Treatment of N-substituted pyrroles with carbonyl compounds and nucleophiles under indium catalysis was found to be a promising method for preparing β-alkylpyrroles without contamination by α-alkylpyrroles. With this methodology, a variety of alkyl groups, which are primary, secondary and tertiary as well as cyclic and functionalized types, can be introduced in place onto the pyrrole ring. The simplicity performable as a catalytic one-step process is one of the important feature of this reaction. The substituent on the nitrogen atom of the product β-alkylpyrrole can be removed easily by literature procedures...
March 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28334512/flow-pickering-emulsion-interfaces-enhance-catalysis-efficiency-and-selectivity-for-cyclization-of-citronellal
#9
Hengquan Yang, Huan Chen, Houbing Zou, Yajuan Hao
Cyclization of citronellal is a necessary intermediate step to produce the important flavor chemical (-)-menthol. We here demonstrate a continuous flow Pickering emulsion (FPE) strategy for selective cyclization of citronellal to (-)-isopulegol, using water droplets hosting heteropolyacid catalyst (HPA) to fill a column reactor. Owing to the large liquid-liquid interface and the excellent confinement capability of droplets toward HPA, the FPE system exhibits a catalysis efficiency much higher than those of batch systems (2~5 fold) and an excellent durability (two months)...
March 23, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28334484/amine-transaminase-engineering-for-spatially-bulky-substrate-acceptance
#10
Uwe Bornscheuer, Martin S Weiß, Ioannis V Pavlidis, Paul Spur, Steven P Hanlon, Beat Wirz, Hans Iding
Amine transaminase (ATA) catalysing stereoselective amination of prochiral ketones is an attractive alternative to transition metal catalysis. As wild-type ATAs accept only non-sterically hindered ketones, efforts to widen the substrate scope to more challenging targets are of general interest. We recently designed ATAs to accept aromatic and thus planar bulky amines, via a sequenced based motif that supports the identification of novel enzymes. However, these variants were not active against 2,2-dimethyl-1-phenyl-propan-1-one, which carries a spatially bulky tert-butyl substituent adjacent to the carbonyl function...
March 23, 2017: Chembiochem: a European Journal of Chemical Biology
https://www.readbyqxmd.com/read/28333400/an-improved-model-of-the-trypanosoma-brucei-ctp-synthetase-glutaminase-domain-acivicin-complex
#11
Juliana Oliveira de Souza, Alice Dawson, William Nigel Hunter
The natural product acivicin inhibits the glutaminase activity of CTP synthetase and is a potent lead compound for drug discovery in the area of neglected tropical diseases, specifically trypanosomaisis. A 2.1 Å resolution crystal structure of the acivicin adduct with the glutaminase domain from Trypanosoma brucei CTP synthetase has been deposited in the Protein Data Bank and provides a template for structure-based approaches to design new inhibitors. However, our assessment of that data identified deficiencies in the model...
March 23, 2017: ChemMedChem
https://www.readbyqxmd.com/read/28333050/oxidative-treatment-of-diclofenac-via-ferrate-vi-in-aqueous-media-effect-of-surfactant-additives
#12
Yingling Wang, Tianjun Ni, Jianmei Yuan, Chunfeng Wang, Guoguang Liu
The potential reaction of diclofenac (DCF) with ferrate(VI) and influences of coexisting surfactants have not been investigated in depth, and are the focus of this study. The results demonstrated that DCF reacted effectively and rapidly with Fe(VI) and approximately 75% of DCF (0.03 mM) was removed by excess Fe(VI) (0.45 mM) within 10 min. All of the reactions followed pseudo first-order kinetics with respect to DCF and Fe(VI), where the apparent second-order rate constant (kapp) was 5.07 M(-1) s(-1) at pH 9...
March 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/28332817/basal-plane-ligand-functionalization-on-semiconducting-2h-mos2-monolayers
#13
Qi Ding, Kyle J Czech, Yuzhou Zhao, Jianyuan Zhai, Robert J Hamers, John C Wright, Song Jin
Molybdenum disulfide (MoS2) is a two-dimensional material promising for electronic, optical, and catalytic applications. To fully harness its potential, functionalization is essential to control its properties. However, MoS2 functionalization has been mostly limited to either 1T-phase MoS2 or the edges of 2H-phase MoS2, and the chemistry of covalent functionalization on the basal plane of 2H-MoS2 is poorly understood. Here we report a facile approach to covalently functionalize chemical vapor deposition (CVD) grown 2H-MoS2 monolayers (MLs), as well as mechanically exfoliated MoS2, via thiol conjugation at sulfur vacancies on the basal plane...
March 23, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28332657/enhanced-hydrogen-sorption-in-a-li-mg-n-h-system-by-the-synergistic-role-of-li4-nh2-3bh4-and-zrfe2
#14
Vivek Shukla, Ashish Bhatnagar, Pawan K Soni, Alok K Vishwakarma, M A Shaz, T P Yadav, O N Srivastava
The present investigation describes the synergistic role of Li4(BH4)(NH2)3 and ZrFe2 in the hydrogen storage behaviour of a Li-Mg-N-H hydride system. The onset desorption temperature of ZrFe2-catalysed Mg(NH2)2-LiH-Li4(BH4)(NH2)3 is ∼122 °C, which is 83 °C, 63 °C, and 28 °C lower than that of thermally treated 2LiNH2-1MgH2, 2LiNH2-1MgH2-4 wt%ZrFe2, and 2LiNH2-1MgH2-0.1LiBH4 composites, respectively. Native Mg(NH2)2-LiH-Li4(BH4)(NH2)3 absorbed only 2.78 wt% of H2 within 30 min. On the other hand, the ZrFe2-catalysed Mg(NH2)2-LiH-Li4(BH4)(NH2)3 sample absorbed 3...
March 23, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28332398/synthesis-of-selectively-substituted-or-deuterated-indenes-via-sequential-pd-and-ru-catalysis
#15
Anupam Jana, Kasjan Misztal, Anna Zak, Karol Grela
A strategy for the synthesis of functionalised indenes is presented. The readily available substituted phenols are used as starting materials in the reaction sequence composed of Pd-catalysed Suzuki coupling and Ru-catalysed ring-closing metathesis, thus representing a practical method for the controlled construction of functionalized indene derivatives. The methodology has been successfully applied to a broad range of substrates, producing substituted indenes in excellent yields. This approach is also utilized for the synthesis of substituted indenes selectivity deuterated in position 3, which are rare in literature...
March 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28332397/base-catalysis-enables-access-to-%C3%AE-%C3%AE-difluoroalkylthioethers
#16
Douglas L Orsi, Brandon J Easley, Ashley M Lick, Ryan A Altman
A nucleophilic addition reaction of aryl thiols to readily available β,β-difluorostyrenes provides α,α-difluoroalkylthioethers. The reaction proceeds through an unstable anionic intermediate, prone to eliminate fluoride and generate α-fluorovinylthioethers. However, the use of base catalysis overcomes the facile β-fluoride elimination, generating α,α-difluoroalkylthioethers in excellent yields and selectivities.
March 23, 2017: Organic Letters
https://www.readbyqxmd.com/read/28330117/microbial-pectinases-an-ecofriendly-tool-of-nature-for-industries
#17
REVIEW
G Garg, A Singh, A Kaur, R Singh, J Kaur, R Mahajan
Pectinases are the growing enzymes of biotechnological sector, showing gradual increase in their market. They hold a leading position among the commercially produced industrial enzymes. These enzymes are ecofriendly tool of nature that are being used extensively in various industries like wine industry; food industry; paper industry for bleaching of pulp and waste paper recycling; in the processing of fruit-vegetables, tea-coffee, animal feed; extraction of vegetable oil and scouring of plant fibres. Moreover, enzymatic catalysis is preferred over other chemical methods, since it is more specific, less aggressive and saves energy...
June 2016: 3 Biotech
https://www.readbyqxmd.com/read/28330099/thermomyces-lanuginosus-lipase-catalyzed-synthesis-of-natural-flavor-esters-in-a-continuous-flow-microreactor
#18
Ahmad Mohammed Gumel, M S M Annuar
Enzymatic catalysis is considered to be among the most environmental friendly processes for the synthesis of fine chemicals. In this study, lipase from Thermomyces lanuginosus (Lecitase Ultra™) was used to catalyze the synthesis of flavor esters, i.e., methyl butanoate and methyl benzoate by esterification of the acids with methanol in a microfluidic system. Maximum reaction rates of 195 and 115 mM min(-1) corresponding to catalytic efficiencies (k cat/K M) of 0.30 and 0.24 min(-1) mM(-1) as well as yield conversion of 54 and 41 % were observed in methyl butanoate and methyl benzoate synthesis, respectively...
June 2016: 3 Biotech
https://www.readbyqxmd.com/read/28329912/structural-and-mechanistic-insights-into-homocysteine-degradation-by-a-mutant-of-methionine-%C3%AE-lyase-based-on-substrate-assisted-catalysis
#19
Dan Sato, Tomoo Shiba, Shunsuke Yunoto, Kazuo Furutani, Mitsuki Fukumoto, Daizou Kudou, Takashi Tamura, Kenji Inagaki, Shigeharu Harada
Methionine γ-lyse (MGL) catalyzes the α, γ-elimination of l-methionine and its derivatives as well as the α, β-elimination of l-cysteine and its derivatives to produce α-keto acids, volatile thiols, and ammonia. The reaction mechanism of MGL has been characterized by enzymological studies using several site-directed mutants. The Pseudomonas putida MGL C116H mutant showed drastically reduced degradation activity toward methionine while retaining activity toward homocysteine. To understand the underlying mechanism and to discern the subtle differences between these substrates, we analyzed the crystal structures of the reaction intermediates...
March 22, 2017: Protein Science: a Publication of the Protein Society
https://www.readbyqxmd.com/read/28328230/functionalized-tetrahydropyridines-by-enantioselective-phosphine-catalyzed-aza-4-2-cycloaddition-of-n-sulfonyl-1-aza-1-3-dienes-with-vinyl-ketones
#20
Huamin Wang, Wei Zhou, Mengna Tao, Anjing Hu, Junliang Zhang
The development of electron-demand disfavored [4 + 2] cycloaddition of two electron-deficient reacting partners poses a considerable challenge. An enantioselective aza-[4 + 2] cycloaddition of electron-deficient N-sulfonyl-1-aza-1,3-dienes is possible with vinyl ketones via phosphine catalysis, which provides facile access to a wide range of enantioenriched trifluoromethylated tetrahydropyridines in up to 97% yield with 97% ee and >20:1 dr. The mechanistic study indicated that this cycloaddition proceeds via a tandem intermolecular aza-Rauhut-Currier/intramolecular aza-Michael addition reaction...
March 22, 2017: Organic Letters
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