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Lili Lv, Lijuan Wang, Jun Li, Yajun Jiao, Shengnan Gao, Jiachang Wang, Hongyuan Yan
A rapid and effective nonaqueous capillary electrophoresis (NACE)-ultraviolet (UV) method was developed for the enantiomeric separation of seven β-agonists. Diacetone-d-mannitol-boric acid complex was used as a new chiral selector. It was in situ synthesized by the reaction of diacetone-d-mannitol and boric acid in methanol medium containing triethylamine. The effects of diacetone-d-mannitol, boric acid, and triethylamine concentrations on the enantioseparation were carefully investigated. Under the optimized conditions, baseline enantioseparation could be obtained for six of the tested β-agonists within 12min...
July 8, 2017: Journal of Pharmaceutical and Biomedical Analysis
Sedef Karabiyikoglu, Byron A Boon, Craig A Merlic
The Pauson-Khand reaction is a powerful tool for the synthesis of cyclopentenones through the efficient [2+2+1] cycloaddition of dicobalt alkyne complexes with alkenes. While intermolecular and intramolecular variants are widely known, transannular versions of this reaction are unknown and the basis of this study. Macrocyclic enyne and dienyne complexes were readily synthesized by palladium(II)-catalyzed oxidative macrocyclizations of bis(vinyl boronate esters) or ring-closing metathesis reactions, followed by complexation with dicobalt octacarbonyl...
July 18, 2017: Journal of Organic Chemistry
Jörg Axthelm, Sven H C Askes, Martin Elstner, Upendar Reddy Gandra, Helmar Görls, Peter Bellstedt, Alexander Schiller
The identification and discrimination of diols is of fundamental importance in medical diagnostics, such as measuring the contents of glucose in the urine of diabetes patients. Diol sensors are often based on fluorophore-appended boronic acids, but these severely lack discrimination power and their response is one-dimensional. As an alternative strategy, we present the use of fluorinated boronic acid-appended pyridinium salts in combination with 19F NMR spectroscopy. A pool of 59 (bio)analytes was screened, containing monosaccharides, phosphorylated and N-acetylated sugars, polyols, carboxylic acids, nucleotides and amines...
July 18, 2017: Journal of the American Chemical Society
Gabriela Statkiewicz-Barabach, Jacek Olszewski, Pawel Mergo, Waclaw Urbanczyk
We present a comprehensive study of an in-line Mach-Zehnder intermodal interferometer fabricated in a boron-doped two-mode highly birefringent microstructured fiber. We observed different interference signals at the output of the interferometer, related to the intermodal interference of the fundamental and the first order modes of the orthogonal polarizations and a beating of the polarimetric signal related to the difference in the group modal birefringence between the fundamental and the first order modes, respectively...
July 18, 2017: Sensors
Natalia Berseneva, Hannu-Pekka Komsa, Ville Vierimaa, Torbjörn Björkman, Zheyong Fan, Ari Harju, Milica Todorović, Arkady Krasheninnikov, Risto M Nieminen
Development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open a possibility to create stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0001), but the stabilization mechanism is still unknown...
July 18, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
James Patrick Morken, Xun Liu, Timothy Maxwell Deaton, Fredrik Haeffner
We describe an unusual net 2+2 cycloaddition reaction between boron alkylidenes and unactivated alkenes. This reaction provides a new method for construction of carbocyclic ring systems bearing versatile organoboronic esters. In addition to surveying the scope of this reaction, we provide details about the mechanistic underpinnings of this process, and examine application to the synthesis of the natural product aphanamal.
July 17, 2017: Angewandte Chemie
Houshang Najafi, Zeynab Mohamadi Yarijani, Meysam Najafi
In this study, the antioxidant activity of crocin via experimental and theoretical methods was investigated. In order to induce oxidative stress, 30-min renal ischemia and 24-h reperfusion were used in male Wistar rats. Oxidative stress was assessed by measuring tissue malondialdehyde (MDA) and ferric reducing/antioxidant power (FRAP). The results showed that following ischemia/reperfusion, the level of MDA was increased and FRAP decreased. Both of these changes were alleviated by crocin administration. The bond dissociation enthalpy and ionization potential values as enthalpies of mechanism of antioxidant activity of crocin were calculated by density functional theory method...
July 17, 2017: Inflammation
Beryl X Li, Diane N Le, Kyle A Mack, Andrew McClory, Ngiap-Kie Lim, Theresa Cravillion, Scott Savage, Chong Han, David B Collum, Haiming Zhang, Francis Gosselin
A highly stereocontrolled synthesis of tetrasubstituted acyclic all-carbon olefins has been developed via a stereoselective enolization and tosylate formation, followed by a palladium-catalyzed Suzuki‒Miyaura cross-coupling of the tosylates and pinacol boronic esters in the presence of Pd(OAc)2/RuPhos catalytic system. Both the enol tosylation and Suzuki‒Miyaura coupling reactions tolerate an array of electronically and sterically diverse substituents and generate high yield and stereoselectivity of the olefin products...
July 17, 2017: Journal of the American Chemical Society
Changjian Deng, Miu Lun Lau, Heather M Barkholtz, Haiping Xu, Riley Parrish, Meiyue Olivia Xu, Tao Xu, Yuzi Liu, Hao Wang, Justin G Connell, Kassiopeia A Smith, Hui Xiong
We report an amorphous boron nanorod anode material for lithium-ion batteries prepared through smelting non-toxic boron oxide in liquid lithium. Boron in theory can provide capacity as high as 3099 mA h g(-1) by alloying with Li to form B4Li5. However, experimental studies of the boron anode have been rarely reported for room temperature lithium-ion batteries. Among the reported studies the electrochemical activity and cycling performance of the bulk crystalline boron anode material are poor at room temperature...
July 17, 2017: Nanoscale
Shoko Tago, Tsuyoshi Ochiai, Seitaro Suzuki, Mio Hayashi, Takeshi Kondo, Akira Fujishima
Detecting the bio-potential changes of plants would be useful for monitoring their growth and health in the field. A sensitive plant monitoring system with flexible boron-doped diamond (BDD) electrodes prepared from BDD powder and resin (Nafion or Vylon-KE1830) was investigated. The properties of the electrodes were compared with those of small BDD plate-type electrodes by monitoring the bioelectric potentials of potted Aloe and hybrid species in the genus Opuntia. While flexible BDD electrodes have wide potential windows, their cyclic voltammograms are different from those of the BDD plate...
July 15, 2017: Sensors
Amin Azizi, Matthew R Gadinski, Qi Li, Mohammed Abu AlSaud, Jianjun Wang, Yi Wang, Bo Wang, Feihua Liu, Long-Qing Chen, Nasim Alem, Qing Wang
Polymer dielectrics are the preferred materials of choice for power electronics and pulsed power applications. However, their relatively low operating temperatures significantly limit their uses in harsh-environment energy storage devices, e.g., automobile and aerospace power systems. Herein, hexagonal boron nitride (h-BN) films are prepared from chemical vapor deposition (CVD) and readily transferred onto polyetherimide (PEI) films. Greatly improved performance in terms of discharged energy density and charge-discharge efficiency is achieved in the PEI sandwiched with CVD-grown h-BN films at elevated temperatures when compared to neat PEI films and other high-temperature polymer and nanocomposite dielectrics...
July 17, 2017: Advanced Materials
Marta Brambilla, Matthew Tredwell
A palladium catalyzed C(sp3)-C(sp2) Suzuki-Miyaura cross-coupling of aryl boronic acids and α-(trifluoromethyl)benzyl tosylates is reported. The reaction uses a readily available, air-stable palladium catalyst to access a wide range of functionalized 1,1-diaryl-2,2,2-trifluoroethanes. Enantioenriched α-(trifluoromethyl)benzyl tosylates were found to undergo cross-coupling to give the corresponding enantioenriched cross-coupled products with an overall inversion in configuration. The crucial role of the CF3 group in promoting this transformation is demonstrated by comparison with non-fluorinated derivatives...
July 14, 2017: Angewandte Chemie
Bin Mu, Jie Tang, Long Zhang, Aiqin Wang
Using graphene as adsorbent for removal of pollutants from polluted water is commonly recognized to be costly because the graphene is usually produced by a very complex process. Herein, a simple and eco-friendly method was employed to fabricate efficient superparamagnetic graphene/polyaniline/Fe3O4 nanocomposites for removal of dyes. The exfoliation of graphite as nanosheets and the functionalization of nanosheets with polyaniline and Fe3O4 nanoparticles were simultaneously achieved via a one-pot reaction process combining the intercalation polymerization of aniline and the co-precipitation of the residual Fe(3+) and the generated Fe(2+)...
July 13, 2017: Scientific Reports
Konstantin Troshin, John F Hartwig
We present an approach to multidimensional high-throughput discovery of catalytic coupling reactions that integrates molecular design with automated analysis and interpretation of mass spectral data. We simultaneously assessed the reactivity of three pools of compounds that shared the same functional groups (halides, boronic acids, alkenes, and alkynes, among other groups) but carried inactive substituents having specifically designed differences in masses. The substituents were chosen such that the products from any class of reaction in multiple reaction sets would have unique differences in masses, thus allowing simultaneous identification of the products of all transformations in a set of reactants...
July 14, 2017: Science
Yu Lu, Nengwu Zhu, Fuhua Yin, Tingting Yang, Pingxiao Wu, Zhi Dang, Meilin Liu, Xiaorong Wei
Currently, the development of less expensive, more active and more stable catalysts like heteroatom-doped carbon based non-precious metal materials are highly desired for the cathodic oxygen reduction reaction (ORR) in microbial fuel cells (MFCs). Comparing with heteroatom sources from chemical reagents, biomass is notably inexpensive and abundant, containing more elements which contribute to ORR activity. Herein, we demonstrate an easy operating one-step and low-cost way to synthesize egg-derived heteroatoms-doped mesoporous carbon (EGC) catalysts utilizing egg as the biomass carbon and other elements source (sulphur, phosphorus, boron and iron), and porous g-C3N4 as both template and nitrogen source...
July 5, 2017: Biosensors & Bioelectronics
Max Pinheiro, Luiz F A Ferrão, Fernanda Bettanin, Adélia J A Aquino, Francisco B C Machado, Hans Lischka
Acenes are fascinating polyaromatic compounds that combine impressive semiconductor properties with an open-shell character by varying their molecular sizes. However, the increasing chemical instabilities related to their biradicaloid structures pose a great challenge for synthetic chemistry. Modifying the π-bond topology through chemical doping allows modulation of the electronic properties of graphene-related materials. In spite of the practical importance of these techniques, remarkably little is known about the basic question - the extent of the radical character created or quenched thereby...
July 12, 2017: Physical Chemistry Chemical Physics: PCCP
Zhuo Zhe Li, An Yong Li
The monocyclic compounds (BRg)3(+)(D3h), (BRg)4(2+)(D4h), (BRg)5(3+)(D5h) and (BRg)6(4+)(D6h) formed between boron and rare gases Rg (He-Rn) are theoretically predicted to be stable structures and have π-aromaticity with a delocalized nc-2e π-system. For heavier rare gases Ar-Rn, the B-Rg bond energy is quite high and ranges from 15 to 96 kcal mol(-1), increasing with the ring size and the atomic number of rare gases; the B-Rg bond length is close to the sum of covalent radii of B and Rg atoms; NBO and AIM analyses show that the B-Rg bonds for Ar-Rn have a typical covalent character...
July 12, 2017: Physical Chemistry Chemical Physics: PCCP
Yifan Li, Yi Zhou, Yan Wu, Chengchi Huang, Long Wang, Xuyan Zhou, Zhenyang Zhao, Hui Li
A self-excited launcher consisting of multi-walled boron nitride nanotubes (BNNTs) has been investigated using molecular dynamics simulation. The results show that, after a period of high frequency oscillation, the innermost BNNT can be spontaneously ejected along its central axis at a relatively fast speed. The launching is caused by the energy transfer between the nanotubes and without absorbing energy from the external environment. Most self-excited launchers could launch their innermost nanotube, although an inappropriate structure of the nanotubes contributes to a blocked or failed launch...
July 12, 2017: Nanoscale
Kanupriya Verma, K S Viswanathan
Dimers of borazine were studied using matrix isolation infrared spectroscopy and ab initio quantum chemical calculations. Computations were performed at the MP2 and M06-2X levels of theory using the 6-311++G(d,p) and aug-cc-pVDZ basis sets for the various homodimers. At both levels of theory, an aligned stacked structure was found to be the global minimum, which was nearly isoenergetic to a parallel displaced structure. A T-shaped structure, where the N-H of one borazine pointed towards the N of the second borazine, was found to be a local minimum...
July 12, 2017: Physical Chemistry Chemical Physics: PCCP
Duc Duy Vo, Mikael Elofsson
Resveratrol-based natural products constitute a valuable source of unique compounds with diverse biological activities. In this report we investigate demethylation strategies to minimize formation of cyclized and dimerized products during the synthesis of viniferifuran and analogues. We found that boron trichloride/tetra-n-butylammonium iodide (BCl3/TBAI) is typically more effective than boron tribromide (BBr3). Based on these findings we carried out the first syntheses of dehydro-δ-viniferin, resveratrol-piceatannol hybrid and anigopreissin A...
December 22, 2016: Advanced Synthesis & Catalysis
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