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A globally accurate full-dimensional potential energy surface (PES) for the OH + CH4 → H2O + CH3 reaction is developed using the permutation invariant polynomial-neural network approach based on ~135 000 points at the level of correlated coupled cluster singles, doubles, and perturbative triples level with the augmented correlation consistent polarized valence triple-zeta basis set. The total root mean square fitting error is only 3.9 meV or 0.09 kcal/mol. This PES is shown to reproduce energies, geometries, and harmonic frequencies of stationary points along the reaction path. Kinetic and dynamical calculations on the PES indicated a good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]

An eight-dimensional quantum dynamical model is proposed and applied to the title reaction. The reaction probabilities and integral cross sections have been determined for both the ground and excited vibrational states of the two reactants. The results indicate that the H2 stretching and CH3 umbrella modes, along with the translational energy, strongly promote the reactivity, while the CH3 symmetric stretching mode has a negligible effect. The observed mode specificity is confirmed by full-dimensional quasi-classical trajectory calculations. The mode specificity can be interpreted by the recently proposed sudden vector projection model, which attributes the enhancement effects of the reactant modes to their strong couplings with the reaction coordinate at the transition state. [ABSTRACT FROM AUTHOR]

The simplest Criegee intermediate CH2OO is important in atmospheric chemistry. It has been detected in the reaction of CH2I + O2 with various spectral methods, including infrared spectroscopy; infrared absorption of CH2OO was recorded at resolution 1.0 cm-1 in our laboratory. We have improved our system and recorded the infrared spectrum of CH2OO at resolution 0.25 cm-1 with rotational structures partially resolved. Observed vibrational wavenumbers and relative intensities are improved from those of the previous report and agree well with those predicted with quantum-mechanical calculations using the MULTIMODE method on an accurate potential energy surface. Observed rotational structures also agree with the simulated spectra according to theoretical predictions. In addition to derivation of critical vibrational and rotational parameters of the vibrationally excited states to confirm the assignments, the spectrum with improved resolution provides new assignments for bands 2ν9 at 1234.2 cm-1 and ν5 at 1213.3 cm-1; some hot bands and combination bands are also tentatively assigned. [ABSTRACT FROM AUTHOR]

The state-to-state dynamics of the title reactions are investigated using a quasi-classical trajectory method on recently developed accurate global potential energy surfaces. Although both produce the H2O product, these two reactions have very different characteristics in the reaction energy, barrier location, and barrier height. It is shown that the H2O product is moderately excited in its three vibrational modes in the HF + OH reaction, but its stretching modes are highly excited in the HCl + OH reaction. For both reactions, the OH vibrational degree of freedom is essentially a spectator, which sequesters its energy throughout the reaction. On the other hand, the HF vibrational excitation has almost no impact on the H2O vibrational distribution while HCl converts some of its vibrational energy into the stretching modes of H2O. These mode specific correlations can be rationalized by the recently proposed Sudden Vector Projection model. [ABSTRACT FROM AUTHOR]

Full-dimensional quantum dynamics and quasi-classical trajectory calculations are reported for the title reaction on a recently constructed ab initio based global potential energy surface. Strong mode specificity was found, consistent with the prediction of the sudden vector projection model. Specifically, the HF vibration strongly promotes the reaction while the OH vibration has little effect. Rotational excitations of both reactants slightly enhance the reaction. [ABSTRACT FROM AUTHOR]

A mononuclear complex {Fe(L) 2 [N(CN) 2 ] 2 } ( 1 ) has been synthesized through the reaction of (naphth-1-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine (L) with Fe[N(CN) 2 ] 2 . Magnetic measurement reveals that 1 exhibits a thermal induced one-step spin crossover behavior with transition temperature T 1/2 of 75 K. Furthermore, the light induced excited spin state trapping effect is observed on 1 . [ABSTRACT FROM AUTHOR]

The slurry chemical action affects chemical reaction between the wafer and slurry, and self-conditioning performance of the pad in nano machining process. Fixed abrasive polishing, one of important nano machining technologies, was adopted to achieve a nano precision surface quality of CaF2 crystal. Five kinds of alkaline regulators, triethanolamine, sodium citrate, sodium carbonate, ethylenediamine and sodium phosphate in slurries with pH 10, were screened in nano machining CaF2 crystal. The effect on material removal rate (MRR), surface topography and surface roughness was investigated in fixed abrasive polishing of CaF2 crystal. The results indicated that surface quality is getting better with MRR decreasing. The optimal surface quality of CaF2 crystal with surface roughness Sa 4.13 nm can be obtained by sodium phosphate slurry with MRR224 nm/min in fixed abrasive polishing of CaF2 crystal. The nanometer precision surface quality with high material removal was achieved in nano machining CaF2 crystal. [ABSTRACT FROM AUTHOR]

A long-standing scientific challenge in the field of alcohol deoxygenation has been direct catalytic sp3 C-O defunctionalization with high selectivity and efficiency, in the presence of other functionalities, such as free hydroxyl groups and amines widely present in biological molecules. Previously, the selectivity issue had been only addressed by classic multistep deoxygenation strategies with stoichiometric reagents. Herein, we propose a catalytic late-transition-metal-catalyzed redox design, on the basis of dehydrogenation/Wolff-Kishner (WK) reduction, to simultaneously tackle the challenges regarding step economy and selectivity. The early development of our hypothesis focuses on an iridium-catalyzed process efficient mainly with activated alcohols, which dictates harsh reaction conditions and thus limits its synthetic utility. Later, a significant advancement has been made on aliphatic primary alcohol deoxygenation by employing a ruthenium complex, with good functional group tolerance and exclusive selectivity under practical reaction conditions. Its synthetic utility is further illustrated by excellent efficiency as well as complete chemo- and regio-selectivity in both simple and complex molecular settings. Mechanistic discussion is also included with experimental supports. Overall, our current method successfully addresses the aforementioned challenges in the pertinent field, providing a practical redox-based approach to the direct sp3 C-O defunctionalization of aliphatic primary alcohols. [ABSTRACT FROM AUTHOR]

An unprecedented cascade vinylogous Mukaiyama 1,6-MA/MA of 2-silyloxyfurans and azoalkenes was realized with a Cu(II)/tBu-Box complex. An array of fused butyrolactones containing multiple stereocenters was generally obtained in good yield (up to 90% yield) with exclusive diastereoselectivity (>20:1 dr) and excellent enantioselectivity (up to 99% ee). Carbon isotope effects measured by 13C NMR revealed a stepwise mechanism for this annulation process. [ABSTRACT FROM AUTHOR]

A series of 1-sulfonyl-1-trifluoromethyl allenes were prepared for the first time from commercial available 2-bromo-3,3,3-trifluoropropene. Cycloaddition reaction of these trifluoromethylated allenes with nitrones occured readily under mild conditions, giving the corresponding trifluoromethylated isoxazolidines in high yields. [ABSTRACT FROM AUTHOR]

The FeWB alloy powders were successfully obtained from reactive synthesis, and the bulk materials were prepared by the spark plasma sintering (SPS) technique using the FeWB alloy powders. The influences of temperature and holding time on the microstructure of alloy powders, as well as the reaction mechanism were investigated by X-ray diffraction meter (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS) and Lakeshore 7410 vibrating sample magnetometer (VSM). The results show that increased temperature and extended holding time are both beneficial to synthesizing the phase FeWB. The boron and iron atoms diffused into tungsten particles to form W2B and Fe2B firstly, and the FeWB alloy powders were obtained at 1150°C after holding 3h. The bulk materials exhibit the Rockwell hardness of 90.4HRA measured by an HR-150A Rockwell hardness tester which could be comparable to the hardness of cemented carbides. FeWB alloy presents a promising future in the hard material area. [ABSTRACT FROM AUTHOR]

A facile and efficient methodology is presented for the direct oxidative esterification of alcohols with alcohols catalyzed by NaAuCl4. Just in the presence of a low catalytic amount of base additive, the newly developed catalytic system proceeds with high selectivity and broad substrate scope under mild conditions with dioxygen or air as the environmentally benign terminal oxidant. Various alcohols including benzylic and allylic alcohols were smoothly reacted with methanol and even with long-chain aliphatic alcohols, affording the desired products in good to excellent yields (up to 95% yield). The present system showed high catalytic activity with a TOF up to 219 h-1. Kinetic studies of the reaction process provide fundamental insights into the catalytic pathway, and a possible reaction pathway was proposed based on the results of the control experiments. XPS, TEM, and UV-vis were carried out to characterize the chemical state of the Au catalyst in the present catalytic system. The results indicate that the Au nanoparticles were generated in situ and supported on K2CO3, forming a simple, recyclable and selective catalyst system for the direct oxidative esterification of alcohols. [ABSTRACT FROM AUTHOR]

The reactions of C702- with organic halides result in several isomeric products. However, the structures of the isomers have not been identified unambiguously and the reactions still remain elusive even though the first report of the reaction appeared more than ten years ago. Herein, the reactions of C702- with ArCH2Br (Ar = Ph, o-, m-, and p-BrC6H4) are revisited. Two types of isomeric para-adducts of 2,5- and 7,23-(ArCH2)2C70 are obtained and characterized with the X-ray single-crystal diffractions, HRMS, ¹H and 13C NMR, and UV-vis spectroscopies. An unusual singlet resonance instead of the typical AB quartet resonance is shown for the C2 diastereotopic methylene protons in ¹H NMR spectrum of 2,5-(PhCH2)2C70 recorded at ambient temperature. The unexpected magnetic equivalence is studied with the variable-temperature (VT) NMR and density functional theory (DFT) calculations. The results show that the greater local curvature in the C70 polar region is likely responsible for the unusual magnetic equivalence exhibited by the C2 diastereotopic methylene protons of 2,5-(PhCH2)2C70, indicating that under certain cases, it is improbable to elucidate the spectral data of fullerene derivatives with a less symmetrical carbon cage in analogy with those of the C60 derivatives. [ABSTRACT FROM AUTHOR]

The exothermic F + H2O → HF + OH reaction has a decidedly "early" or "reactant-like" barrier. According to a naïve interpretation of the Polanyi's rules, translational energy would be more effective than vibrational energy in promoting such reactions. However, we demonstrate here using both quasi-classical trajectory and full-dimensional quantum wave packet methods on an accurate global potential energy surface that excitations in the H2O vibrational degrees of freedom have higher efficacy in enhancing the reactivity of the title reaction than the same amount of translational energy, thus providing a counter-example to Polanyi's rules. This enhancement of reactivity is analyzed using a vibrational adiabatic model, which sheds light on the surprising mode selectivity in this reaction. [ABSTRACT FROM AUTHOR]

The catalytic enantioselective fluorination of N--H-free 3-substituted oxindoles was accomplished by a Sc(III)/N,N'-dioxide complex. Under mild reaction conditions, a series of 3-aryl- and 3-alkyl-3-fluoro-2-oxin doles were obtained in excellent yields (up to 9896) and enantioselectivities (up to 99% ee) by using N-fluorobisbenzenesulfonimide (NFSI) as the fluorination agent MaxiPost was synthesized efficiently in 81% yield with 96% ee. [ABSTRACT FROM AUTHOR]

Singly bonded PhCH2C60-C60CH2Ph dimers are generated via controlled-potential bulk electroreduction and electrooxidation of 1,2-(PhCH2)HC60. The reaction mixture was purified by HPLC, and the isolated fraction was characterized with single-crystal X-ray diffractions, H and NMR, MS, elemental analysis, and cyclic voltammetry. It was shown that the fraction consists of two HPLC-inseparable PhCH2C60-C60CH2Ph regioisomers, which are assigned as the meso and racemic regioisomers. The bulk electrolysis processes for the formation of the dimers were followed by in situ cyclic voltammetry and were further corroborated with an in situ voltammetric titration of 1,2-(PhCH2)HC60 with tetra-n-butylammonium hydroxide (TBAOH), on the basis of which a reaction mechanism is proposed. [ABSTRACT FROM AUTHOR]

The reactions of dianionic C60 with organic halides, which have been studied extensively in benzonitrile (PhCN), are revisited in a different solvent medium, N,N-dimethylformamide (DMF), by using ArCH2Br (Ar = Ph, C6H4CH3, C6H4Br). Interestingly, instead of the 1,4-R2C60 adducts, which are the typical products when the reactions are carried out in PhCN, the 1,2-dihydro[60]fullerenes (1,2-HRC60) have been obtained as the major products in DMF, except for the case of o-CH3C6H4CH2Br probably due to the steric effect. The obtained 1,2-dihydro[6Q]fullerenes have been characterized with single-crystal diffraction, 1H and 13C NMR, high-resolution mass spectrometry (HRMS), and UV-vis. Further examination with deuterated reagents including PhCD2Br, DMF-d7, and D2O has revealed that the fullerenyl hydrogen of 1,2-dihydrofullerenes originates from traces of water residue in DMF. When the reaction is re-examined in PhCN with the addition of an excessive amount of water, the yield of I ,2-dihydrofullerene increases significantly, but is still lower compared with that obtained in DMF, demonstrating a considerable solvent effect on the reactivity of C602-. A possible mechanism accounting for such a difference is proposed. The work has presented an alternative protocol for effective preparation of 1,2-dihydro[60]fullerenes, and may also provide clues toward a better understanding of the proton transfer process for anionic C60-mediated reducing reactions involving H2O. [ABSTRACT FROM AUTHOR]

A new metal–organic framework [(LaL)·3H2O]n(L = chelidamic acid) with good optical properties was obtained through the hydrothermal reaction. It is the third three-dimensional framework constructed from chelidamic acid and presents a rare (3,6)-connected topology with Schläfli symbol (42.6)2(44.62.87.102). [ABSTRACT FROM AUTHOR]

A simple and highly efficient C–C bond formation was developed by the activation of two sp3 C–H bonds. [ABSTRACT FROM AUTHOR]

A series of RuO2 · xH2O/carbon aerogel (CA) composite electrode materials was prepared by a chemical precipitation method. Ultrasonication was used to accelerate the chemical reaction and improve the dispersion of RuO2 · xH2O particles on the surface and the pores of the aerogel. The structure and morphology of the as-prepared composite were characterized by N2 adsorption isotherm, X-ray diffraction (XRD), and field emission-scanning electron microscopy (FE-SEM). The results showed that the CA had a pearly network structure and the composites had a relatively high specific surface area and mesopore volume. The electrochemical performance of the composite electrodes was studied by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance measurements. The results indicated a substantial increase in the specific capacitance of the composite. Moreover, the utilization efficiency of RuO2 · xH2O was greatly improved by loading it on the conductive and porous CA due to a significant improvement in the inter-particle electronic conductivity and the extensive mesoporous network of the composites. [ABSTRACT FROM AUTHOR]

An initial state selected time-dependent wave packet method is applied to study the dynamics of the OH + CHD3 reaction with a six-dimensional model on a newly developed full-dimensional ab initio potential energy surface (PES). This quantum dynamical (QD) study is complemented by fulldimensional quasi-classical trajectory (QCT) calculations on the same PES. The QD results indicate that both translational energy and the excitation of the CH stretching mode significantly promote the reaction while the excitation of the umbrella mode has a negligible effect on the reactivity. For this early barrier reaction, interestingly, the CH stretching mode is more effective than translational energy in promoting the reaction except at very low collision energies. These QD observations are supported by QCT results. The higher efficacy of the CH stretching model in promoting this early barrier reaction is inconsistent with the prediction of the naively extended Polanyi's rules, but can be rationalized by the recently proposed sudden vector projection model. [ABSTRACT FROM AUTHOR]

This study investigated the photochemical behavior of the ferroin--bromate--benzoquinone reaction in a batch system, in which the reduction of ferriin was dominated by bromide ions rather than by organic substrates as known in most of bromate oscillators. The chemical oscillations exhibited ultrasensitive response to illumination, where both the oscillation frequency and lifetime were significantly increased by ceiling light with an intensity of less than 20 µW/cm². As the light intensity was increased, the influence of light evolved from constructive to inhibitory. At a constant illumination, the influence of light also underwent a transition from constructive to inhibitory when the acid concentration was increased from 0.03 to 0.09 M. NMR measurements and absorption spectroscopy indicated photoenhanced bromination of benzoquinone and photoenhanced reduction of ferriin by bromide ions. [ABSTRACT FROM AUTHOR]

The crystallization of ammonium dihydrogen phosphate (MAP) is largely affected by certain metal ions such as Fe (III), and the influence seems to be pointed at both ends. Therefore, the industrial-grade MAP products can only be obtained by purifying the neutralized MAP solution from wet-process phosphoric acid (WPA). The extraction kinetics of Fe (III) from MAP solution using di-2-ethylhexyl phosphoric acid (D2EHPA) in sulfonated kerosene measured by the Lewis cell. The extraction mechanism is discussed and confirmed on the basis of the dimeric model of D2EHPA in non-polar solution. From the temperature dependence of reaction rate, the value of Ea and Kf are calculated and the extraction regimes are deduced to be mixed controlled with diffusion and chemical reaction for Fe (III). Ultimately, the rate equation for the extraction reaction of Fe (III) with D2EHPA is obtained as follows: Rf = 0.08cFe3+1.2cH2A2 0.81cH+-0.85. [ABSTRACT FROM AUTHOR]

The article highlights a study on the reaction of carboxylic acids and isonitriles in small spaces. The authors relates their results of several observations on the reactions of carboxylic acids and isonitriles in a cylindrical hosts by NMR methods and with a bulkier group on the isonitrles. It concludes that the encapsulation does provide an alternative to reactions at high temperatures in bulk solution.

Eight of novel fluoro-substituted phosphonate derivatives were synthesized and the preliminary bioassay indicated that these compounds exhibited herbicidal activities. [ABSTRACT FROM AUTHOR]

This article focuses on the catalytic allylic alkylation via the cross-dehydrogenative-coupling (CDC) reaction between allylic sp3 C-H and methylenic sp3 C-H bonds. The palladium catalyzed allylic alkylation is one of the most important reactions for constructing C-C bonds in modern organic synthesis. The direct utilization of an allylic C-H bond rather than an allylic functional group would avoid the need to synthesize the allylic functional group, thus leading to increased synthetic efficiency. The development of a catalytic allylic alkylation via a CDC reaction would be quite desirable. With the optimized reaction conditions established, various substrates were subjected to the allylic alkylation reactions.

Describes a highly efficient three-component coupling of aldehyde, alkyne, and amines via C-H activation catalyzed by gold in water. Catalytic properties of gold; Proposed mechanism for the three-component coupling; Applicability of the reaction to both aromatic and aliphatic aldehydes and amines.

A palladium-catalyzed homo cross-dehydrogenative coupling (CDC) of 2-arylpyridines via C-H activation is described. This reaction employs I2 as the sole oxidant without any other additives, which complements the hypervalent iodine chemistry, such as of phenyliodonium diacetate (PIDA) or IOAc, in C-H activation research field. A tentative mechanism involving a Pd(II)-Pd(IV) catalytic cycle is proposed to rationalize this homo CDC reaction. [ABSTRACT FROM AUTHOR]

An unprecedented multicomponent cascade asymmetric inverse-electron-demand Diels-Alder/nucleophilic addition/ring-opening reaction involving 2-methoxyfurans as efficient dienophiles was successfully developed with Cu(I)/tBu-Box complex as the catalyst. A diverse array of tetrahydropyridazines containing unexpectedly stable γ-hydroxyl ester moiety was obtained in generally good yield with exclusive regioselectivity and excellent stereoselectivity. [ABSTRACT FROM AUTHOR]

The dihydro­pyrimidine ring of the title compound, C14H15N3O5, assumes a boat conformation. The stability of the solid-state structure is enhanced by π–π stacking inter­actions and hydrogen-bonding inter­actions, linking the mol­ecules into an extended three-dimensional network. [ABSTRACT FROM AUTHOR]

Colorless crystals of the title compound, C29H24NO5P, were synthesized by the reaction of triphenyl­phosphine, an iron porphyrin complex and 4-nitro­benzyl 2-diazo-3-oxobutanoate at 353 K. All bond distances and angles are within normal ranges and there are no notable inter­actions between neighboring mol­ecules. [ABSTRACT FROM AUTHOR]

The article discusses synthesis of aromatic amide foldamers which are chain of molecules and oligomers that adopts secondary structure of proteins stabilized by non covalent interactions. The molecular design and development of hydrogen bonding patterns in aromatic amide foldamers is discussed. It also refers to design principles and basic synthetic strategies that should be employed for preparation of foldamers.

Abstract: The objective of this work was to develop appropriate reaction pathways to explain the liquefaction behavior of cornstalk in sub- and super-critical ethanol. This reaction system was divided into gas lump, water-soluble oil lump, heavy oil lump, volatile organic compounds lump and residue lump based on the characteristics of cornstalk and liquefaction products, and the residue was further separated into carbon, hydrogen, oxygen and nitrogen. Results showed that the reversible reaction between heavy oil and volatile organic compounds occurred in the liquefaction process, and the decrease in the water-soluble oil yield was mainly attributed to the conversion of water-soluble oil to gas in the sub- and super-critical ethanol. The GC/MS analysis showed that the volatile organic compounds, water-soluble oil and heavy oil comprised a mixture of organic compounds of 6–10, 3–12 and 8–20 carbons, respectively, which mainly included esters, phenols, acids, furans and their derivatives. [Copyright &y& Elsevier]

Poly(ethylene adipate- co- l-lactic acid) (PLEA) copolymers were prepared via ring opening polymerization from l-lactide and hydroxyl terminated poly(ethylene adipate) prepolymer as starting materials. The composition and microstructure of the PLEA copolymers were characterized by nuclear magnetic resonance (H NMR) spectra. Results confirmed the incorporation of lactic acid segments into the chain of PLEA copolymers as well as the existence of ester exchange reaction. The thermal behaviors and thermal stability of the resultant PLEA copolymers were evaluated by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA), respectively; and the crystal structure was confirmed by using wide-angle X-ray diffraction (WAXD). Results showed that those properties of the PLEA copolymers showed high dependence on the composition of the copolymers. [ABSTRACT FROM AUTHOR]

A highly efficient double-hydroamination reaction of o-alkynylanilines with terminal alkynes leading to N-alkenylindoles was developed by using gold(III) as a catalyst under neat conditions. [ABSTRACT FROM AUTHOR]

Cu-catalyzed cross-dehydrogenative coupling (CDC) methodologies were developed based on the oxidative activation of sp3 C-H bonds adjacent to a nitrogen atom. Various sp, sp2, and sp3 C-H bonds of pronucleophiles were used in the Cu-catalyzed CDC reactions. Based on these results, the mechanisms of the CDC reactions also are discussed. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed coupling of N-heterocycles with simple alcohols was achieved. The reaction is initiated by peroxide and does not require the use of stoichiometric acid for activation of the heterocycle. [ABSTRACT FROM AUTHOR]

A novel and convenient strategy to separate, recover and reuse N-heterocyclic carbene catalysts in transesterification reactions has been developed. [ABSTRACT FROM AUTHOR]

Abstract: A simple route for the preparation of 3,4,6-substituted pyridazines is described by using Tebbe olefination of esters then Diels–Alder reaction of the resulting enol ethers with tetrazine. [Copyright &y& Elsevier]

Acid and metalliferous release occurring when sulfide (principally pyrite)-containing rock from mining activities and from natural environments is exposed to the elements is acknowledged as a major environmental problem. Acid rock drainage (ARD) management is both challenging and costly for operating and legacy mine sites. Current technological solutions are expensive and focused on treating ARD on release rather than preventing it at source. We describe here a viable, practical mechanism for reduced ARD through the formation of silicate-stabilized iron oxyhydroxide surface layers. Without silicate, oxidized pyrite particles form an overlayer of crystalline goethite or lepidocrocite with porous structure. With silicate addition, a smooth, continuous, coherent and apparently amorphous iron oxyhydroxide surface layer is observed, with consequent pyrite dissolution rates reduced by more than 90% at neutral pH. Silicate is structurally incorporated within this layer and inhibits the phase transformation from amorphous iron (oxy)hydroxide to goethite, resulting in pyrite surface passivation. This is confirmed by computational simulation, suggesting that silicate-doping of a pseudoamorphous iron oxyhydroxide (ferrihydrite structure) is thermodynamically more stable than the equivalent undoped structure. This mechanism and its controlling factors are described. As a consequence of the greatly reduced acid generation rate, neutralization from on-site available reactive silicate minerals may be used to maintain neutral pH, after initial limestone addition to achieve neutral pH, thus maintaining the integrity of these layers for effective ARD management. [ABSTRACT FROM AUTHOR]

SiC network reinforced C/C-ZrB 2 -ZrC-SiC composites are prepared by precursor infiltration and pyrolysis process with C/C-ZrB 2 fabric as preform. SiC wires with different lengthscales form networks in pores and matrix of the composites. The composites exhibit good ablation resistance under the plasma flame. After ablation, a network reinforced film is formed in the ablation center, which can prevent the oxygen and heat attacking the substrate. The formation of the network interlocking structure not only improves the toughness of the film, but also enhances the bonding ability of the film due to the pinning effect of the ablated networks. [ABSTRACT FROM AUTHOR]

Uranium oxide clusters UOx- (x = 3-5) were produced by laser vaporization and characterized by photoelectron spectroscopy and quantum theory. Photoelectron spectra were obtained for UOx at various photon energies with well-resolved detachment transitions and vibrational resolution for x = 3 and 4. The electron affinities of UOx were measured as 1.12, 3.60, and 4.02 eV for x = 3, 4, and 5, respectively. The geometric and electronic structures of both the anions and the corresponding neutrals were investigated by quasi-relativistic electron-correlation quantum theory to interpret the photoelectron spectra and to provide insight into their chemical bonding. For UOx clusters with x ≤ 3, the O atoms appear as divalent closed-shell anions around the U atom, which is in various oxidation states from UII(fds)4 in UO to UVI(fds)0 in UO3. For x > 3, there are no longer sufficient valence electrons from the U atom to fill the O(2p) shell, resulting in fractionally charged and multicenter delocalized valence states for the O ligands as well as η1- or η2-bonded O2 units, with unusual spin couplings and complicated electron correlations in the unfilled poly oxo shell. The present work expands our understanding of both the bonding capacities of actinide elements with extended spdf valence shells as well as the multitude of oxygen's charge and bonding states. [ABSTRACT FROM AUTHOR]

A facile and versatile catalytic system involving copper catalyst, K3PO4 as the base, and O2 as the oxidant has been developed to enable efficient synthesis of 2,4,6-trisubstituted and 2,6-disubstituted 1,3,5-triazines and 1,3-disubstituted 1,2,4-triazoles from amidines with trialkylamines, DMSO, and DMF as the reaction partners, respectively. This protocol features inexpensive metal catalyst, green oxidant, good functional group tolerance, and high regioselectivity, providing an efficient entry to those products that are challenging to prepare by traditional methods. A single-electron-transfer (SET) mechanism is proposed for these transformations. [ABSTRACT FROM AUTHOR]

The Pictet-Spengler (PS) reaction constructs plant alkaloids such as morphine and camptothecin, but it has not yet been noticed in the fungal kingdom. Here, a silent fungal Pictet-Spenglerase (FPS) gene of Chaetomium globosum 1C51 residing in Epinephelus drummondhayi guts is described and ascertained to be activable by 1-methyl-L-tryptophan (1-MT). The activated FPS expression enables the PS reaction between 1-MT and flavipin (fungal aldehyde) to form "unnatural" natural products with unprecedented skeletons, of which chaetoglines B and F are potently antibacterial with the latter inhibiting acetylcholinesterase. A gene-implied enzyme inhibition (GIEI) strategy has been introduced to address the key steps for PS product diversifications. In aggregation, the work designs and validates an innovative approach that can activate the PS reaction-based fungal biosynthetic machinery to produce unpredictable compounds of unusual and novel structure valuable for new biology and biomedicine. [ABSTRACT FROM AUTHOR]

The article focuses on the development of a novel olefination method using decarbonylative addition of alkynes and aldehydes. It states that an alkene is generated when an alkyne is added during carbon—hydrogen (C—H) activation of aldehydes. It also notes that a high chemoselectivity was observed during the aromatic and aliphatic aldehydes chemical reaction.

Aqueous carbonation of Ca(OH)2 is a complex process that produces calcite with scalenohedral calcite phases and characterized by inadequate carbonate species for effective carbonation due to the poor dissolution of CO2 in water. Consequently, we report a solid-liquid-gas carbonation system with an ionic liquid (IL), 1-butyl-3-methylimidazolium bromide, in view of enhancing the reaction of CO2 with Ca(OH)2. The use of the IL increased the solubility of CO2 in the aqueous environment and enhanced the transport of the reactive species (Ca2+ and CO3 2-) and products. The presence of the IL also avoided the formation of the CaCO3 protective and passivation layer and ensured high carbonation yields, as well as the production of stoichiometric rhombohedral calcite phases in a short time. [ABSTRACT FROM AUTHOR]

A highly efficient silver-catalyzed chemoselective method for the reduction of aldehydes to their corresponding alcohols in water was developed by using hydrosilanes as reducing agents. The ketones remained essentially inert under the same reaction conditions, thereby providing an additional synthetically useful chemoselectivity. [ABSTRACT FROM AUTHOR]

Graphene represents a two-dimensional material having extraordinary physical properties, which make it a prospective material for many applications. In particular, graphene oxide (GO), with abundant chemical functional groups, further extends the new functions of graphene-based materials. However, the preparation of GO materials through chemical reactions remains a challenge to materials science. Here, using suitable cross-linkable polymers, a GO-polyacrylic acid (PAA) composite membrane was prepared by a gel-desiccation approach. The fabricated membrane displays both well controlled mechanical characteristics and unique multiple pH response. [ABSTRACT FROM AUTHOR]

A metal-free method for the direct regioselective fluorination of anilides has been developed. In the presence of bis(tert-butylcarbonyloxy)iodobenzene (PhI(OPiv)2) and hydrogen fluoride-pyridine, the para-fluorination products of anilides were obtained in moderate to good yields. Because of its operational safety and the use of readily available reagents, this new procedure provides facile access to a variety of para-fluorinated anilides. [ABSTRACT FROM AUTHOR]

A highly selective ruthenium-catalyzed C−N bond formation was developed by using the hydrogen-borrowing strategy. Various tertiary amines were obtained efficiently from nitroarenes and primary alcohols. The reaction tolerates a wide range of functionalities. A tentative mechanism was proposed for this direct amination reaction of alcohols with nitroarenes. [ABSTRACT FROM AUTHOR]