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Chemical Science

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https://read.qxmd.com/read/30774926/correction-enantioselective-convergent-synthesis-of-the-ineleganolide-core-by-a-tandem-annulation-cascade
#1
Robert A Craig, Jennifer L Roizen, Russell C Smith, Amanda C Jones, Scott C Virgil, Brian M Stoltz
[This corrects the article DOI: 10.1039/C6SC03347D.].
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774925/efficient-room-temperature-production-of-high-quality-graphene-by-introducing-removable-oxygen-functional-groups-to-the-precursor
#2
Hongwu Chen, Wencheng Du, Jing Liu, Liangti Qu, Chun Li
The excellent solution-processability of graphene oxide (GO) has provided a collection of strategies for the construction of functional graphene assemblies. To improve the performance of graphene-based materials, structurally intact GO should be prepared as a precursor for high-quality graphene; however, solution chemical methods have been constantly challenged by a structural integrity versus fabrication yield trade-off. Here, we report a wet chemical method for the high-efficiency production of a high-quality graphene oxide precursor, with all steps conducted at room-temperature...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774924/one-dimensional-vs-two-dimensional-proton-transport-processes-at-solid-liquid-zinc-oxide-water-interfaces
#3
Matti Hellström, Vanessa Quaranta, Jörg Behler
Long-range charge transport is important for many applications like batteries, fuel cells, sensors, and catalysis. Obtaining microscopic insights into the atomistic mechanism is challenging, in particular if the underlying processes involve protons as the charge carriers. Here, large-scale reactive molecular dynamics simulations employing an efficient density-functional-theory-based neural network potential are used to unravel long-range proton transport mechanisms at solid-liquid interfaces, using the zinc oxide-water interface as a prototypical case...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774923/oxidative-steps-during-the-biosynthesis-of-squalestatin-s1
#4
Karen E Lebe, Russell J Cox
The squalestatins are a class of highly complex fungal metabolites which are potent inhibitors of squalene synthase with potential use in the control of cholesterol biosynthesis. Little is known of the chemical steps involved in the construction of the 4,8-dioxa-bicyclo[3.2.1]octane core. Here, using a combination of directed gene knockout and heterologous expression experiments, we show that two putative non-heme-iron-dependent enzymes appear to catalyse a remarkable series of six consecutive oxidations which set up the bioactive core of the squalestatins...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774922/novel-near-infrared-ii-aggregation-induced-emission-dots-for-in-vivo-bioimaging
#5
Jiacheng Lin, Xiaodong Zeng, Yuling Xiao, Lin Tang, Jinxia Nong, Yufang Liu, Hui Zhou, Bingbing Ding, Fuchun Xu, Hanxing Tong, Zixin Deng, Xuechuan Hong
Near-infrared II fluorescence imaging holds great promise for in vivo imaging and imaging-guided surgery with deep penetration and high spatiotemporal resolution. However, most NIR-II aromatic luminophores suffer from the notorious aggregation-caused quenching (ACQ) effect in the aqueous solution, which largely hinders their biomedical application in vivo . In this study, the first NIR-II organic aggregation-induced emission (AIE) fluorophore ( HLZ-BTED ), encapsulated as nanoparticles ( HLZ-BTED dots) for in vivo biomedical imaging, was designed and synthesized...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774921/reduction-of-organic-azides-by-indyl-anions-isolation-and-reactivity-studies-of-indium-nitrogen-multiple-bonds
#6
Mathew D Anker, Matthias Lein, Martyn P Coles
The synthesis of a new potassium-indyl complex, K[In(NONAr )] (NONAr = [O(SiMe2 NAr)2 ]2- , Ar = 2,6-i Pr2 C6 H3 ) and its reactivity with organic azides RN3 is reported. When R = 2,6-bis(diphenylmethyl)-4- t Bu-phenyl, a dianionic alkyl-amide ligand is formed via C-H activation across a transient In-Nimide bond. Reducing the size of the R-group to 2,4,6-trimethylphenyl (mesityl, Mes) enables oxidation of the indium and elimination of dinitrogen to afford the imide species, K[In(NONAr )(NMes)]. The anion contains a short In-Nimide bond, shown computationally to contain appreciable multiple bond character...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774920/%C3%AE-c-h-hetero-arylation-via-cu-catalyzed-radical-relay
#7
Zuxiao Zhang, Leah M Stateman, David A Nagib
A Cu-catalyzed strategy has been developed that harnesses a radical relay mechanism to intercept a distal C-centered radical for C-C bond formation. This approach enables selective δ C-H (hetero)arylation of sulfonamides via intramolecular hydrogen atom transfer (HAT) by an N-centered radical. The radical relay is both initiated and terminated by a Cu catalyst, which enables incorporation of arenes and heteroarenes by cross-coupling with boronic acids. The broad scope and utility of this catalytic method for δ C-H arylation is shown, along with mechanistic probes for selectivity of the HAT mechanism...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774919/gold-catalyzed-4-3-annulations-of-2-alkenyl-1-alkynylbenzenes-with-anthranils-with-alkyne-dependent-chemoselectivity-skeletal-rearrangement-versus-non-rearrangement
#8
RahulKumar Rajmani Singh, Manisha Skaria, Liang-Yu Chen, Mu-Jeng Cheng, Rai-Shung Liu
Two distinct (4+3)-nitroxy annulations between 1,5-enynes and anthranils have been developed to access tetrahydro-1 H -benzo[ b ]azepine derivatives; the chemoselectivity varies with the types of alkynes. Terminal alkyne substrates deliver benzo[ b ]azepine derivatives via a novel skeletal rearrangement while internal 1,5-enynes afford products without a rearrangement process. To elucidate the mechanism of rearrangement, we performed 13 C- and 2 H-labeling experiments to identify the gold-containing isobenzofulvene intermediates, but their formation relies on the presence of anthranils...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774918/rationally-designed-pure-inorganic-upconversion-nanoprobes-for-ultra-highly-selective-hydrogen-sulfide-imaging-and-elimination-in-vivo
#9
Yuxin Liu, Qi Jia, Xuejiao Zhai, Fang Mao, Anqi Jiang, Jing Zhou
Lung injury is a hydrogen sulfide (H2 S)-associated complication with high mortality in acute pancreatitis (AP) cases. Herein, we used Prussian Blue (PB) as a H2 S-responsive acceptor to develop a novel pure-inorganic upconversion nanoprobe for detecting and eliminating H2 S, which can be used for diagnosing AP and alleviating lung injury. Upconversion nanoprobes with 5 nm PB shells were optimized to achieve outstanding in vitro H2 S detection capacity (linear range: 0-150 μM, LOD: 50 nM), which met the in vivo serum H2 S range, and thus were feasible for imaging H2 S in vivo ...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774917/topology-and-porosity-control-of-metal-organic-frameworks-through-linker-functionalization
#10
Jiafei Lyu, Xuan Zhang, Ken-Ichi Otake, Xingjie Wang, Peng Li, Zhanyong Li, Zhijie Chen, Yuanyuan Zhang, Megan C Wasson, Ying Yang, Peng Bai, Xianghai Guo, Timur Islamoglu, Omar K Farha
Tetratopic organic linkers have been extensively used in Zr-based metal-organic frameworks (MOFs) where diverse topologies have been observed. Achieving meticulous control over the topologies to tune the pore sizes and shapes of the resulting materials, however, remains a great challenge. Herein, by introducing substituents to the backbone of tetratopic linkers to affect the linker conformation, phase-pure Zr-MOFs with different topologies and porosity were successfully obtained under the same synthetic conditions...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774916/visualization-of-the-effect-of-additives-on-the-nanostructures-of-individual-bio-inspired-calcite-crystals
#11
Johannes Ihli, Jesse N Clark, Nasima Kanwal, Yi-Yeoun Kim, Mark A Holden, Ross J Harder, Chiu C Tang, Sharon E Ashbrook, Ian K Robinson, Fiona C Meldrum
Soluble additives provide a versatile strategy for controlling crystallization processes, enabling selection of properties including crystal sizes, morphologies, and structures. The additive species can also be incorporated within the crystal lattice, leading for example to enhanced mechanical properties. However, while many techniques are available for analyzing particle shape and structure, it remains challenging to characterize the structural inhomogeneities and defects introduced into individual crystals by these additives, where these govern many important material properties...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774915/melting-temperature-suppression-of-layered-hybrid-lead-halide-perovskites-via-organic-ammonium-cation-branching
#12
Tianyang Li, Wiley A Dunlap-Shohl, Eric W Reinheimer, Pierre Le Magueres, David B Mitzi
Hybrid organic-inorganic lead halide perovskites have attracted broad interest because of their unique optical and electronic properties, as well as good processability. Thermal properties of these materials, often overlooked, can provide additional critical information for developing new methods of thin film preparation using, for example, melt processing- i.e. , making films of hybrid perovskites by solidification of a thin layer of the melt liquid. We demonstrate that it is possible to tune the melting temperature of layered hybrid lead iodide perovskites over the range of more than 100 degrees by modifying the structures of alkylammonium-derived organic cations...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774914/activatable-cell-biomaterial-interfacing-with-photo-caged-peptides
#13
Yiyang Lin, Manuel M Mazo, Stacey C Skaalure, Michael R Thomas, Simon R Schultz, Molly M Stevens
Spatio-temporally tailoring cell-material interactions is essential for developing smart delivery systems and intelligent biointerfaces. Here we report new photo-activatable cell-material interfacing systems that trigger cellular uptake of various cargoes and cell adhesion towards surfaces. To achieve this, we designed a novel photo-caged peptide which undergoes a structural transition from an antifouling ligand to a cell-penetrating peptide upon photo-irradiation. When the peptide is conjugated to ligands of interest, we demonstrate the photo-activated cellular uptake of a wide range of cargoes, including small fluorophores, proteins, inorganic ( e...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774913/development-and-mechanistic-investigation-of-the-manganese-iii-salen-catalyzed-dehydrogenation-of-alcohols
#14
Simone V Samuelsen, Carola Santilli, Mårten S G Ahlquist, Robert Madsen
The first example of a manganese(iii) catalyst for the acceptorless dehydrogenation of alcohols is presented. N , N' -Bis(salicylidene)-1,2-cyclohexanediaminomanganese(iii) chloride ( 2 ) has been shown to catalyze the direct synthesis of imines from a variety of alcohols and amines with the liberation of hydrogen gas. The mechanism has been investigated experimentally with labelled substrates and theoretically with DFT calculations. The results indicate a metal-ligand bifunctional pathway in which both imine groups in the salen ligand are first reduced to form a manganese(iii) amido complex as the catalytically active species...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774912/ni-catalyzed-migratory-fluoro-alkenylation-of-unactivated-alkyl-bromides-with-gem-difluoroalkenes
#15
Lu Zhou, Chuan Zhu, Peijia Bi, Chao Feng
We describe a nickel-catalyzed highly regio- and stereoselective migratory fluoro-alkenylation of unactivated alkyl bromides. A unique catalytic cycle merging alkyl nickel chain-walking and defluorinative coupling enables the introduction of a broad array of fluoroalkenyl moieties into carbon chains. Control experiments with other halogenated alkenes demonstrated the essential role of fluorine atoms in this reaction. Notably, the reaction proceeds under mild conditions and allows for the synthesis of a variety of valuable monofluoroalkenes...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774911/the-inverted-ketene-synthon-a-double-umpolung-approach-to-enantioselective-%C3%AE-2-3-amino-amide-synthesis
#16
Mahesh Vishe, Jeffrey N Johnston
A stereocontrolled synthesis of β2,3 -amino amides is reported. Innovation is encapsulated by the first use of nitroalkenes to achieve double umpolung in enantioselective β-amino amide synthesis. Step economy is also fulfilled by the use of Umpolung Amide Synthesis (UmAS) in the second step, delivering the amide product without intermediacy of a carboxylic acid or activated derivative. Molybdenum oxide-mediated hydride reduction provides the anti -β2,3 -amino amide with high selectivity.
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774910/multifunctional-behavior-of-molecules-comprising-stacked-cytosine-ag-i-cytosine-base-pairs-towards-conducting-and-photoluminescence-silver-dna-nanowires
#17
Fátima Linares, Emilio García-Fernández, F Javier López-Garzón, María Domingo-García, Angel Orte, Antonio Rodríguez-Diéguez, Miguel A Galindo
DNA molecules containing a 1D silver array may be applied for nanotechnology applications, but first their conducting and photoluminescence behavior must be enhanced. Here we have synthesized and characterized three new helical compounds based on stacked silver-mediated cytosine base pairs [Ag(mC)2 ]X (mC = N1-methylcytosine; X = NO3 ( 1 ), BF4 ( 2 ) and ClO4 ( 3 )), that contain uninterrupted polymeric AgI chains that run through the center of the helixes, comparable to related silver-DNA structures. The exposure of nanostructures of [Ag(mC)2 ]BF4 ( 2 ) to cold hydrogen plasma stimulates the reduction of the prearranged AgI polymeric chains to metallic silver along the material...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774909/a-low-valent-dinuclear-ruthenium-diazadiene-complex-catalyzes-the-oxidation-of-dihydrogen-and-reversible-hydrogenation-of-quinones
#18
Xiuxiu Yang, Thomas L Gianetti, Michael D Wörle, Nicolaas P van Leest, Bas de Bruin, Hansjörg Grützmacher
The dinuclear ruthenium complex [Ru2 H(μ-H)(Me2 dad)(dbcot)2 ] contains a 1,4-dimethyl-diazabuta-1,3-diene (Me2 dad) as a non-innocent bridging ligand between the metal centers to give a [Ru2 (Me2 dad)] core. In addition, each ruthenium is bound to one dibenzo[ a , e ]cyclooctatetraene (dbcot) ligand. This Ru dimer converts H2 to protons and electrons. It also catalyzes reversibly under mild conditions the selective hydrogenation of vitamins K2 and K3 to their corresponding hydroquinone equivalents without affecting the C[double bond, length as m-dash]C double bonds...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774908/asymmetric-maltose-neopentyl-glycol-amphiphiles-for-a-membrane-protein-study-effect-of-detergent-asymmetricity-on-protein-stability
#19
Hyoung Eun Bae, Yang Du, Parameswaran Hariharan, Jonas S Mortensen, Kaavya K Kumar, Betty Ha, Manabendra Das, Hyun Sung Lee, Claus J Loland, Lan Guan, Brian K Kobilka, Pil Seok Chae
Maintaining protein stability in an aqueous solution is a prerequisite for protein structural and functional studies, but conventional detergents have increasingly showed limited ability to maintain protein integrity. A representative novel agent, maltose neopentyl glycol-3 (MNG-3), has recently substantially contributed to membrane protein structural studies. Motivated by the popular use of this novel agent, we prepared asymmetric versions of MNG-3 and evaluated these agents with several membrane proteins including two G protein-coupled receptors in this study...
January 28, 2019: Chemical Science
https://read.qxmd.com/read/30774907/host-guest-selectivity-in-a-series-of-isoreticular-metal-organic-frameworks-observation-of-acetylene-to-alkyne-and-carbon-dioxide-to-amide-interactions
#20
Jack D Humby, Oguarabau Benson, Gemma L Smith, Stephen P Argent, Ivan da Silva, Yongqiang Cheng, Svemir Rudić, Pascal Manuel, Mark D Frogley, Gianfelice Cinque, Lucy K Saunders, Iñigo J Vitórica-Yrezábal, George F S Whitehead, Timothy L Easun, William Lewis, Alexander J Blake, Anibal J Ramirez-Cuesta, Sihai Yang, Martin Schröder
In order to develop new porous materials for applications in gas separations such as natural gas upgrading, landfill gas processing and acetylene purification it is vital to gain understanding of host-substrate interactions at a molecular level. Herein we report a series of six isoreticular metal-organic frameworks (MOFs) for selective gas adsorption. These materials do not incorporate open metal sites and thus provide an excellent platform to investigate the effect of the incorporation of ligand functionality via amide and alkyne groups on substrate binding...
January 28, 2019: Chemical Science
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