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The observation of electronic motion remains a key target in the development of the field of attoscience. However, systems in which long-lived oscillatory charge migration may be observed must be selected carefully, particularly because it has been shown that nuclear spatial delocalization leads to a loss of coherent electron density oscillations. Here we demonstrate electron dynamics in norbornadiene and extended systems where the hole density migrates between two identical chromophores. By studying the effect of nuclear motion and delocalization in these example systems, we present the physical properties that must be considered in candidate molecules in which to observe electron dynamics. Furthermore, we also show a key contribution to nuclear delocalization arises from motion in the branching plane of the cation. For the systems studied, the dephasing time increases with system size while the energy gap between states, and therefore the frequency of the density oscillation, decreases with size (obeying a simple exponential dependence on the inter-chromophore distance). We present a system that balances these two effects and shows several complete oscillations in the spin density before dephasing occurs. [ABSTRACT FROM AUTHOR]

Pseudomonadaceae y Moraxellaceae families comprise species with medical, agricultural and biotechnological relevance. Pseudomonas aeruginosa and Acinetobacter baumanii, for example, are opportunist pathogens responsible for several nosocomial infections. The Pseudomonadaceae family also includes the phytopathogenic bacteria Pseudomonas syringae and the denitrifying species Azotobacter vinelandii, both with agriculture impact. Even though Pseudomonadaceae and Moraxellaceae have been widely studied, few studies have been conducted to the identification of molecular markers that could be used to distinguish members of these families from other groups of bacteria. The identification of Indels (insertions or deletions) in conserved proteins sequences has been widely used for taxonomic and evolutionary studies in bacteria. In the present study, we investigated whether insertions identified in highly conserved proteins may be used as molecular markers for taxonomic and phylogenetic studies in Pseudomonadaceae and Moraxellaceae families. For this purpose, DNA repair and replication-related protein sequences were obtained from the international databases and aligned using ClustalX2. The one amino acid length insertion identified in the protein DNA polymerase I distinguishes the Pseudomonadaceae y Ventosimonadaceae families; and the larger 11 amino acids insertion, also identified in this protein, supports the monophyletic grouping of Psychrobacter and Moraxella genera. Moreover, the five amino acids insertion in the protein DNA polymerase III (alpha subunit) is distinctive to the Moraxellaceae family. Thus, the insertions evaluated constitute molecular markers useful to assess taxonomy in Pseudomonadaceae and Moraxellaceae, and also provide tools for phylogenetic studies and molecular identification of bacteria included in these important families. [ABSTRACT FROM AUTHOR]

An efficient enantioselective acyl migration reaction of furanyl carbonates was developed to construct all‐carbon quaternary stereogenic centers. In some cases, the reactions required only 0.05 mol % (minimum 500 ppm) of catalyst and showed a high turnover frequency value (TOF; 3640 h−1). Multigram‐scale reactions (10 grams) also proceeded with high enantioselectivity (>99:1 e.r.) in quantitative yield. The catalyst was robust and easily recovered in 98 % yield. A wide range of functional groups were tolerated (15 examples, >98 % yield, up to >99:1 e.r.), and a variety of optically active 3,3′‐disubstituted benzofuranone derivatives, which are useful intermediates for the synthesis of natural products and pharmaceuticals, were efficiently obtained. Control experiments on the catalyst structure (e.g. catalyst 1 a vs. 1 a′ and 1 a′′) and computational calculations revealed that both the catalytic activity and enantioselectivity should be enhanced by hydrogen bonding between catalyst and substrate. Moreover, this system was applied to the challenging γ‐selective acyl migration reaction of furanyl carbonates with high γ‐selectivity and high enantioselectivity (α:γ=10:90, 95:5 e.r.). Need for a spicy catalyst: The reactions required only 0.05 mol % (minimum 500 ppm) of catalyst and showed a high turnover frequency value (TOF; 3640 h−1). A variety of optically active 3,3′‐disubstituted benzofuranone derivatives were efficiently obtained (15 examples, >98 % yield, up to >99:1 e.r.). Moreover, this system was applied to a challenging γ‐selective acyl migration reaction of furanyl carbonates with high γ‐selectivity and high enantioselectivity (α/γ=10:90, 95:5 e.r.). [ABSTRACT FROM AUTHOR]

Highlights • Grow MAPbBr x Cl (3−x) perovskite single crystals in 7 different halide ratio. • Firstly investigate the actual element ratio in perovskite single crystals by EDX. • Fabricate high performance X-ray detectors and realize X-ray imaging. Abstract Organometallic perovskites MAPbX 3 (MA = CH 3 NH 3 and X = I, Br or Cl) are considered as potential materials for X-ray and gamma ray detection due to its high Z atom, large mobility-lifetime product and growth from solution. However, perovskites with one kind halide own numbers of free charges and yielded unbearable noise current. In this work, we grow perovskite single crystals (PSC) with different halide ratio and find the MAPbBr 2.5 Cl 0.5 PSC shows outstanding performance in electric properties. Through energy dispersive X-ray spectrum, vacancy and excess of Pb is thought as the main cause of free charges. The atomic ratio between halide and Pb as 3 in MAPbBr 2.5 Cl 0.5 PSC and its large resistivity 5.6 × 108 Ω cm and 160 cm2 V−1 s−1 high mobility are measured. Thanks to the smaller noise current, higher electric field could be established for higher charges collect efficiency. As a result, compared with pristine perovskite single crystals, improved X-ray detection performance is demonstrated. This work provides useful information to achieve high performance X-ray detectors based on organometallic perovskites. [ABSTRACT FROM AUTHOR]

A rare, ruthenium‐catalyzed, oxazolinlyl assisted C−H functionalization and three‐component cascade cyclization for the synthesis of isoquinolinones via a metal‐carbene migratory insertion is reported. The transformation is unique since it involves the formation of multiple bonds in one pot via C−H functionalization and ring opening of oxazolines. Detailed mechanistic investigations reveal interesting insights on the mode of transformation, involving reversible C−H activation, migratory insertion of the diazo compound and cascade cyclization as the key step of the transformation. [ABSTRACT FROM AUTHOR]

A sterereospecific and efficient synthesis of thiosugars derived from levoglucosenone and methyl α‐d‐glucopyranoside was developed by a domino epoxide ring opening‐ xanthate migration to afford 1,3‐oxathiolane‐2‐thiones in high yields. The stereochemical outcome of the new C–S bond was defined by the configuration of the starting materials. The 1,3‐oxathiolane‐2‐thiones were subsequently submitted to a second tandem reaction affording the corresponding 2,3‐episulfide alcohols. The thiosugars obtained are useful building blocks for the synthesis of thiooligosaccharides with potential biological properties. A stereospecific and efficient synthesis of thiosugars derived from levoglucosenone and methyl α‐d‐glucopyranoside was developed by a domino epoxide ring opening‐ xanthate migration to afford 1,3‐oxathiolane‐2‐thiones in high yields. [ABSTRACT FROM AUTHOR]

The effects of dispersion on migratory insertion reactions and related iron–carbon bond dissociation energies pertaining to (Me2IPr)FeR2 (R = neoPe, 1-nor), and the conversion of (Me2IPr)Fe(=NAd)R2 to (Me2IPr)Fe{N(Ad}R)R are investigated via calculations and structural comparisons. Dispersion appears to be an underappreciated, major contributor to common structure and reactivity relationships. [ABSTRACT FROM AUTHOR]

Phosphogypsum (PG), which is a solid waste in phosphate fertilizer industry, is harmful to the environment. The pyrogenetic decomposition is mainly used in the utilization of PG, and PG decomposition residue is produced in the decomposition process. In this paper, the migration and conversion rules of elements (Al, Si, P, K, Ca, and Fe) in the purification procedure of CaO in PG decomposition residue was investigated. The acid–base method was used to purify CaO. Content and chemical forms of elements in the purification procedure were analyzed by many characterization methods such as SEM and EDS. And moreover, changes on chemical forms of elements were supported theoretically by some ternary phase diagrams, which were made by the FactSage thermodynamics software. The result showed that, the soluble silicon dioxide and the acid‐insoluble material in PG decomposition residue were effectively removed by using the acid–base method. Meanwhile, impurities separated from CaO and the CaO sample were produced in the experiment, the former can be used to produce the building materials, refractories, insulating materials in various industrial fields, and CaO sample could be used as the filler, building materials, decolorant, etc. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1020–1030, 2018 [ABSTRACT FROM AUTHOR]

Radical-mediated controllable difunctionalization of alkenes provides a powerful tool for the manipulation of olefins and has become a hot topic recently. In general, however, the scope of alkene is largely restricted to the activated alkenes. The development of a general strategy for the functionalization of unactivated alkenes is desired, yet remains challenging. In this review, we have summarized the recent advances in the strategy of intramolecularly distal migration of functional groups which has been efficiently applied in the radical-mediated difunctionalization of unactivated alkenes. A portfolio of functionalities including aryl, cyano, heteroaryl, imino, carbonyl, alkynyl, and alkenyl groups showcase the migratory aptitude. [ABSTRACT FROM AUTHOR]

Abstract: A palladium‐catalyzed oxygenative cross‐coupling of ynamides and benzyl bromides has been developed. After subsequent hydrogenation, α,α‐disubstituted amide derivatives were obtained in good yields. Migratory insertion of α‐oxo palladium carbene species, generated by intermolecular oxidation, is proposed as the key step in this reaction. The study demonstrates the potential of ynamides to serve as carbene precursors in palladium‐catalyzed C−C bond‐forming cross‐coupling reactions. [ABSTRACT FROM AUTHOR]

A Ru-catalyzed olefin migration reaction of chiral cyclic allylic acetal is reported. The reaction generates cyclic enol acetal in a highly chemoselective manner. A variety of O,O- and N,O-acetals participated in the reaction with conservation of the stereochemical integrity of the acetal moiety. The utility of the reaction was demonstrated by the short and protective group-free syntheses of (L)-deoxyribonucleoside and β-amicetose glycoside. [ABSTRACT FROM AUTHOR]

In a first part of this work the permeation through and diffusion/migration from high density polyethylene, polybutylene, polypropylene and cross linked polyethylene films was investigated experimentally with three different methods to determine diffusion coefficients in these polyolefins for a series of additives, their degradation products and other organic substances in the 20–60 °C temperature range. The experimental methods used were dynamic permeation through additive free the polymer films, kinetic desorption from additivated films into water and kinetic migration from additivated into additive free polymer films. It was found that in general the temperature dependence of the obtained diffusion coefficients was well represented by the Arrhenius law. Some of these results also suggested that the contact of the polyolefins with water had an influence on the magnitude of the diffusion coefficients and on their apparent activation energy of diffusion. In the second part of this work the obtained pools of diffusion coefficients for each of the investigated polymers were used to develop an approach to estimate theoretically and without any further experimentation “conservative” diffusion coefficients for any organic substance, with molecular mass ranging from 50 to 1250 g/mol, diffusing in these polymers at temperatures between 15 and 85 °C. The possibility to estimate such conservative diffusion coefficients is very important when it comes to use efficiently migration modelling as an alternative method to test the compliance of polymeric articles with the existing national and/or European standards for drinking water. The use of polymer specific diffusion coefficients in migration modelling is required in the framework of the “Migration modelling guideline” recommendation of the German Environment Agency. [ABSTRACT FROM AUTHOR]

Migratory insertion of carbon-based species into transition-metal-carbon bonds is a mechanistic manifold of vast significance: it underlies the Fischer -- Tropsch process, Mizoroki -- Heck reaction, Ziegler -- Natta and analogous late- transition-metal-catalyzed olefin polymerizations, and a number of carbonylative methods for the synthesis of ketones and esters, among others. Although this type of reactivity is well-precedented for most transition metals, gold constitutes a notable exception, with virtually no well-characterized examples known to date. Yet, the complementary reactivity of gold to numerous other transition metals would offer new synthetic opportunities for migratory insertion of carbon-based species into gold -- carbon bonds. Here we report the discovery of well-defined Au(III) complexes that participate in rapid migratory insertion of carbenes derived from silyl- or carbonyl-stabilized diazoalkanes into Au -- C bonds at temperatures > -- 40 °C. Through a combined theoretical and experimental approach, key kinetic, thermodynamic, and structural details of this reaction manifold were elucidated. This study paves the way for homogeneous gold-catalyzed processes incorporating carbene migratory insertion steps. [ABSTRACT FROM AUTHOR]

A Ni-catalyzed method for arylboration is disclosed. The method allows for highly stereoselective arylboration of unactivated alkenes. The reactions utilize a simple Ni-catalyst and work with a broad range of alkenes and aryl bromides. The products represent useful intermediates for chemical synthesis due to the versatility of the C -- B bond. Preliminary mechanistic details of the method are also disclosed. [ABSTRACT FROM AUTHOR]

Hypothesis The amount and distribution of slip agents, erucamide, and behenamide, on the surface of high-density polyethene, is determined by integral characteristics of slip agent structure and polymer morphology. A suite of surface analysis techniques was applied to correlate physicochemical properties with slip-additive migration behaviour and their surface morphology. The migration, surface morphology and physicochemical properties of the slip additives, crystallinity and orientation of polyethene spherulites and interaction between slip additives and high-density polyethene influence the surface characteristics. Experimental The high-density polyethene closures were produced with erucamide and behenamide separately and stored until they produced required torque. Surface composition was determined employing spectroscopy and gas chromatography. The distribution of additives was observed under optical, scanning electron and atomic force microscopes. The surface energy, crystallinity and application torque were measured using contact angle, differential scanning calorimeter and a torque force tester respectively. Results and discussion Each slip additive produced a characteristic amide peak at 1645 cm −1 in infrared spectroscopy and peaks of oxygen and nitrogen in X-ray photoelectron spectroscopy, suggesting their presence on the surface. The erucamide produced placoid scale-like structures and behenamide formed denticulate structures. The surface erucamide and behenamide responsible for reducing the torque was found to be 15.7 µg/cm 2 and 1.7 µg/cm 2 . [ABSTRACT FROM AUTHOR]

We have developed a highly efficient aryl migration from an aryl ether to a carboxylic acid group through retro-Smiles rearrangement by visible-light photoredox catalysis at ambient temperature. Transition metals and a stoichiometric oxidant and base are avoided in the transformation. Inspired by the high efficiency of this transformation and the fundamental importance of C−O bond cleavage, we developed a novel approach to the C−O cleavage of a biaryl ether to form two phenolic compounds, as demonstrated by a one-pot, two-step gram-scale reaction under mild conditions. The aryl migration exhibits broad scope and can be applied to the synthesis of pharmaceutical compounds, such as guacetisal. Primary mechanistic studies indicate that the catalytic cycle occurs by a reductive quenching pathway. [ABSTRACT FROM AUTHOR]

Cross-coupling reaction involving Cu catalysed carbene migratory insertion with N-tosylhydrazones as the reaction partner with various substituted cyanuric chloride were studied, which has been recognized as a new type of cross-coupling reaction. Cu-carbene migratory insertion is proposed to play the key role in this transformation to form C-C bond from heterohalides with various tosylhydrazones. Salient features of this reactions are (i) no stoichiometric organometallic reagents are required (ii) less toxic and step economical reaction (iii) easy to handle, to get moderate to excellent yields. Outcome of this reaction produces 1,1-heterodiaryl alkanes. [ABSTRACT FROM AUTHOR]

Among the coenzyme B 12 -dependent enzymes, methylmalonyl-CoA mutase (MMCM) catalyzes the carbon-skeleton rearrangement reaction between R -methylmalonyl-CoA and succinyl-CoA. Diethyl 2-bromomethyl-2-phenylmalonate, an alkyl bromide substrate having two different migrating groups (phenyl and carboxylic ester groups) on the β -carbon, was applied to the electrolysis mediated by a hydrophobic vitamin B 12 model complex, heptamethyl cobyrinate perchlorate in this study. The electrolysis of the substrate at − 1.0 V vs. Ag-AgCl by light irradiation afforded the simple reduced product (diethyl 2-methyl-2-phenylmalonate) and the phenyl migrated product (diethyl 2-benzyl-2-phenylmalonate), as well as the electrolysis of the substrate at − 1.5 V vs. Ag-AgCl in the dark. The electrolysis of the substrate at − 2.0 V vs. Ag-AgCl afforded the carboxylic ester migrated product (diethyl phenylsuccinate) as the major product. The selectivity for the migrating group was successfully tuned by controlling the electrolysis potential. We clarified that the cathodic chemistry of the Co(III) alkylated heptamethyl cobyrinate is critical for the selectivity of the migrating group through mechanistic investigations and comparisons to the simple vitamin B 12 model complex, an imine/oxime-type cobalt complex. [ABSTRACT FROM AUTHOR]

Reactions of (cyclopentadienylidenehydrazono)triphenylphosphorane with RuCl2(PPh3)3 or (η6-cymene)RuCl2(PPh3) in toluene produced the chlorocyclopentadienyl complex (η5-C5H4Cl)RuCl(PPh3)2, which was likely formed through the cyclopentadienylidene intermediate RuCl2{C(C4H4)}(PPh3)2. Treatment of (η6-cymene)RuCl2(PPh3) with (cyclopentadienylidenehydrazono)triphenylphosphorane in methanol gave [(η5-C5H4Cl)Ru(η6-cymene)]+. Computational studies reveal that the thermodynamic stability of the analogous chlororuthenium complexes RuCl2(CRR')(PPh3)2 and [RuCl(CRR')(PMe3)(η6-C6H6)]+, with respect to the formation of the corresponding η5-chloropentadienyl complexes via a migratory carbene-insertion reaction is in the order of cyclopentadienylidene < indenylidene < fluorenylidene < phenylcarbene. [ABSTRACT FROM AUTHOR]

Migration and desorption of hydrogen atom and molecule on/from graphene are crucial for understanding mechanism of the hydrogen storage in graphene and graphene synthesis. All possible hydrogen atom migration, hydrogen atom and hydrogen molecule desorption from single layer graphene have been studied systematically by using functional density theory B3LYP/6-31G(d). Our results show that the hydrogen atom desorption is energetically favorable with the lowest desorption barrier of 149.3 kJ mol −1 from stable hydrogen adsorption sites, while the migration is restricted due to high barriers which are greater than 191.0 kJ mol −1 . Hydrogen molecular desorption is possible only from edge adsorbed hydrogen atom due to its comparable barrier of 149.9 kJ mol −1 . Other hydrogen molecular desorption pathways are less likely due to small population of the reaction species. [ABSTRACT FROM AUTHOR]

In this study, we investigate the spontaneous migration of small objects driven by surface tension on a catenoid, formed by a layer of soap constrained by two rings. Although the average curvature of the catenoid is zero at each point, the small objects always migrate to the position near the ring. The force and energy analyses have been performed to uncover the mechanism, and it is found that the small objects distort the local shape of the liquid film, thus making the whole system energetically favorable. These findings provide some inspiration to design microfluidics, aquatic robotics, and miniature boats. [ABSTRACT FROM AUTHOR]

A simple and efficient method for Cp*CoIII-catalyzed C-H bond alkylation using activated olefins was developed. Selective C-H monoalkylation was performed at ambient temperature. One-pot symmetrical dialkylation and sequential unsymmetrical C-H dialkylation were performed to give the desired products in excellent yields. The reaction was found to proceed through an M-alkyl intermediate after migratory insertion, and this intermediate undergoes protodemetalation to give the expected alkylated product along with the regenerated catalyst. [ABSTRACT FROM AUTHOR]

A simple and efficient method for Cp*CoIII-catalyzed C-H bond alkylation using activated olefins was developed. Selective C-H monoalkylation was performed at ambient temperature. One-pot symmetrical dialkylation and sequential unsymmetrical C-H dialkylation were performed to give the desired products in excellent yields. The reaction was found to proceed through an M-alkyl intermediate after migratory insertion, and this intermediate undergoes protodemetalation to give the expected alkylated product along with the regenerated catalyst. [ABSTRACT FROM AUTHOR]

The three-dimensional (3D) distribution and oxidation state of a Pt cathode catalyst in a practical membrane electrode assembly (MEA) were visualized in a practical polymer electrolyte fuel cell (PEFC) under fuel-cell operating conditions. Operando 3D computed-tomography imaging with X-ray absorption near edge structure (XANES) spectroscopy (CT-XANES) clearly revealed the heterogeneous migration and degradation of Pt cathode catalyst in an MEA during accelerated degradation test (ADT) of PEFC. The degradative Pt migration proceeded over the entire cathode catalyst layer and spread to MEA depth direction into the Nafion membrane. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via an unprecedented enantioselective 1,5-palladium migration. High enantioselectivity was achieved by employing 4,4′-bis(trimethylsilyl) ( R)-Binap as the chiral ligand, and a series of mechanistic investigations were carried out to probe the catalytic cycle of this process. [ABSTRACT FROM AUTHOR]

The minimum energy paths for the migration of interstitial Mg in wurtzite GaN are studied through density functional calculations. The study also comprises Li, Na, and Be dopants to examine the dependence on size and charge of the dopant species. In all cases considered, the impurities diffuse like ions without any tendency of localizing charge. Li, Mg, and to some extent Na, diffuse almost isotropically in GaN, with average diffusion barriers of 1.1, 2.1, and 2.5 eV, respectively. Instead Be shows a marked anisotropy with energy barriers of 0.76 and 1.88 eV for diffusion paths perpendicular and parallel to the c-axis. The diffusion barrier generally increases with ionic charge and ionic radius, but their interplay is not trivial. The calculated migration barrier for Mg is consistent with the values estimated in a recent [ABSTRACT FROM AUTHOR]

In this work we show that classic coordination of the oxo group in an oxorhenium hydride complex to M(C6F5)3 (M = Al, B) leads to dramatic increases in the rate of migratory olefin insertion. Combined experimental and computational studies have been utilized to understand the reasons for the rate enhancement upon coordination of the oxo group to the Lewis acid. The mechanism for migratory insertion involves coordination of the olefin to rhenium in the equatorial plane. This induces mixing of the rhenium--hydride σ bond with a rhenium-oxygen π* orbital. This results in an accumulation of electron density on the oxo ligand. The Lewis acid lowers the barrier for migratory insertion by diminishing the electron density on the oxo ligand in the transition state. [ABSTRACT FROM AUTHOR]

The Truce-Smiles rearrangement is an X → C aryl migration reaction that is achieved by an intramolecular nucleophilic aromatic substitution pathway. The reaction exhibits a wide substrate scope with respect to a migrating aryl ring and leaving group, appearing in many different tandem reaction sequences, to achieve a wide variety of product outcomes. We present an extensive survey of reported examples of the Truce-Smiles rearrangement from the chemistry literature (1950s until present) organized by various substrate design variables or aspects of the reaction method. Present deficiencies in our understanding of the reaction are identified with recommendations for future research directions and useful developments in the application of the reaction are celebrated. [ABSTRACT FROM AUTHOR]

It is shown that a cationic rhodium(I)/biphep complex catalyzes the cycloisomerization of 2-(alkynylsilylethynyl)phenols, leading to alkynylmethylidene-benzoxasiloles through concomitant silicon and carbon migration. This unprecedented cycloisomerization presumably proceeds via the formation of rhodium vinylidenes through 1,2-silicon migration, followed by 1,3-carbon (alkyne) migration via the formation of hypervalent silicon centers. [ABSTRACT FROM AUTHOR]

Herein we report a novel, general protocol for distal heteroaryl ipso-migration and its application to the elusive heteroarylation of unactivated alkenes. A set of nitrogen-containing heteroaryl groups showcase the migratory aptitude. This reaction provides a variety of fluoroalkyl functionalized heteroarenes under mild reaction conditions. This is the first report of a difunctionalization of unactivated alkenes with distal heteroaryl migration. [ABSTRACT FROM AUTHOR]

An unexpected ring-contraction from benzo[b]pyrazino[1,2-d][1,4]thiazine-1,4-diones ( 6 ) to benzo[4,5]thiazolo[3,2-a]pyrazine-1,4-diones ( 7 ) has been developed. The preliminary mechanistic studies showed the transformation contained two independent steps: the first step is the formation of a Michael adduct upon the addition of the protic solvent, in the presence of base, to the C-2-C-3 double bond of compound 6 , and the second step is a ring-contraction induced by oxygen via the migration of sulfur atom from C-2 to C-3 position. And its scope is also studied. [ABSTRACT FROM AUTHOR]

Aryl migration reactions of C-3 aryl substituted pyrrolidinoindoline compounds to provide highly conjugated C-2 aryl indole compounds have been discovered. The developed reactions have a wide substrate scope and proceed in high yield under simple acidic conditions. A unique cationic cyclopropane intermediate as the transition state is proposed. [ABSTRACT FROM AUTHOR]

A palladium(ii)-based metallomesogen with azobenzene was synthesized for the fabrication of an optically and electrically tunable polarized light modulator. Owing to the extended molecular geometry constructed by organometallic chemistry, the photo-responsive metallomesogen showed an excellent orientation in liquid crystal media. [ABSTRACT FROM AUTHOR]

We report herein an efficient and mechanistically unique tandem chemoselective 1,2-/1,4-migration of the thio group in keto thioesters that provides substituted butenolides in moderate to excellent yields. Thus, α-keto thioesters in the presence of stabilized phosphonate carbanions undergo tandem 1,2-sulfur migration; whereas 1,4-migration of the thio group has been achieved with the same thioesters after the treatment with Wittig reagents followed by BF3⋅OEt2-catalyzed tandem reaction. The crossover experiments and the isolation of intermediates reveal a stepwise mechanism for both of these transformations. [ABSTRACT FROM AUTHOR]

The environmental pollution of phenol is primarily taken as a result of wastewater discharged from some special chemical plants. It is the common pollutant to be controlled in industrial wastewater, and therefore, how to effectively minimize its environmental pollution by the phenolic pollutants treatment and recovery becomes an important subject. This paper aims to make a study on the support liquid membrane separation from phenolic wastewater in hydrated environment. The process of separation is conducted with hydrophobic ionic liquid 1-butyl-3-methylimidazole hexafluorophosphate [BMIM]PF 6 prepared by the microwave synthesis method based on fundamental solvent extraction research and applied to the inner coupling liquid membrane system. as the purpose is to migrate phenol in the simulated wastewater and survey the temperature, stirring speed, feed liquid phase acidity, initial concentration and NaOH concentration in the stripping phase influence on the phenol migration to obtain the preferred condition for migration. The said condition is as follows: The temperature of 300 K, the stirring speed ranging from 350 to 400 rpm, the feed liquid phase pH of 3.65, and NaOH concentration of 0.8 mol/L in the stripping phase. In the system, phenol is approximated to 100% in migration rate and the ionic liquid may be recycled for several times. [ABSTRACT FROM AUTHOR]

Alkylferrocene-based burning rate catalysts exhibit high migration tendency and volatility during prolonged storage and fabrication process of the solid propellants. To retard the migration problems, eight ionic compounds composed of ferrocenylmethyldimethylammonium cation paired with a common energetic anion, were synthesized by 'one-step' procedure. The compounds were characterized by FT-IR, NMR, and UV/Vis spectroscopy as well as elementary analysis. Their crystal structures were confirmed by single-crystal X-ray diffraction. The TG and DSC analyses indicated that they exhibit high thermal stability. Cyclic voltammetry studies suggested that most of them show reversible or quasi-reversible redox waves. The anti-migration results revealed that 1- 4 are low-migratory compounds, but 5 exhibits high migration trends. The TG curves at 70 °C for 24 h showed that all of them have low volatility. They have from high to low impact sensitivity depending on the anions of the compounds. They all exhibit significant effect on the thermal decomposition of ammonium perchlorate (AP) and some of them accelerate the thermal degradation of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX). Among them 4 is the best one. Unexpectedly, compound 5, with 1H-tetrazolate as anion, can decompose into its original reactants at the temperature just higher than its melting point and could show smart-material functionality in solid propellants. [ABSTRACT FROM AUTHOR]

Transition metal carbenes are versatile intermediates that can mediate many reactions. Among the different reactions they can participate in, their reactions with alkynes are especially diverse. The present digest describes the different reaction pathways that can take place when a transition metal carbene reacts with an alkyne, summarizes the most recent developments for each reactivity profile, and tries to shed light on the factors influencing the different reaction types. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed intramolecular carbopalladation of N-aryl acrylamides followed by migratory insertion of an isocyanide-coordinated C(sp3)−Pd intermediate afforded an alkylimidoyl−PdII complex, which can be intercepted by a nucleophile, including heteroarenes. In addition to amides, the alkylimidoyl−PdII complex was successfully converted into esters, ketones, and bis-heterocyclic compounds. An unprecedented palladium-catalyzed enantioselective domino process involving isocyanide was also documented. [ABSTRACT FROM AUTHOR]

Neutral ferrocene-based burning rate (BR) catalysts show strong migration trends and volatility during long-time storage and curing of the composite solid propellants. To reduce these disadvantages thirty-two ferrocenyl quaternary ammonium compounds, paired with polycyano anions, were synthesized and characterized by 1H NMR, 13C NMR, and UV/Vis spectroscopy, as well as elemental analysis. Additionally, crystal structures of eight compounds were confirmed by single-crystal X-ray diffraction. TG and DSC analyses indicated that the compounds containing 1,1,2,3,3-pentacyanopropenide anions show high thermal stability. Cyclic voltammetry studies suggested that they are quasi-reversible or irreversible redox systems. Anti-migration tests verified that the tested compounds show very low migration tendency and some of them exhibit no migration after 30 days aging at 70 °C. Their catalytic efficiency in the thermal decomposition of ammonium perchlorate (AP), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) were examined by DSC analyses. The results revealed that most of the compounds exhibit distinct effects on the thermal degradation of AP and RDX. Two compounds have good catalytic ability in the thermal decomposition of HMX, representing rare examples of the reported ferrocenyl ionic compounds, which display catalytic property during combustion of HMX. [ABSTRACT FROM AUTHOR]

Photoinitiators are widely used to cure ink on packaging materials used in food applications such as cardboards for the packaging of dry foods. Conventional migration testing for long-term storage at ambient temperature with Tenax®was applied to paperboard for the following photoinitiators: benzophenone (BP), 4,4ʹ-bis(diethylamino)benzophenone (DEAB), 2-chloro-9H-thioxanthen-9-one (CTX), 1-chloro-4-propoxy-9H-thioxanthen-9-one (CPTX), 4-(dimethylamino)benzophenone (DMBP), 2-ethylanthraquinone (EA), 2-ethylhexyl-4-dimethylaminobenzoate (EDB), ethyl-4-dimethylaminobenzoate (EDMAB), 4-hydroxybenzophenone (4-HBP), 2-hydroxy-4-methoxybenzophenone (HMBP), 2-hydroxy-4ʹ-(2-hydroxyethoxy)-2-methylpropiophenone (HMMP), 2-isopropyl-9H-thioxanthen-9-one (ITX), 4-methylbenzophenone (MBP) and Michler’s ketone (MK). Test conditions (10 days at 60°C) were according to Regulation (EU) No. 10/2011 and showed different migration patterns for the different photoinitiators. The results were compared with the migration in cereals after a storage of 6 months at room temperature. The simulation with Tenax at 60°C overestimated actual migration in cereals up to a maximum of 92%. In addition, the effect of a lower contact temperature and the impact of the Tenax pore size were investigated. Analogous simulation performed with rice instead of Tenax resulted in insufficiently low migration rates, showing Tenax is a much stronger adsorbent than rice and cereals. [ABSTRACT FROM PUBLISHER]

A new method for the synthesis of benzoxepines via migratory insertion into a Pd carbene followed by C-C bond cleavage was developed. Various benzoxepines were constructed by the regioselective ring expansion concomitant with the introduction of an aryl group at their 5-position. [ABSTRACT FROM AUTHOR]

The process and mechanisms of secondary hydrocarbon migration in the Huixi half-graben, Pearl River Mouth Basin, were investigated on the basis of geological analysis of the strata and study of the porosity and permeability of the reservoir rocks, fluid potential, oil properties, and geochemistry of oil-source correlation. The results suggest that the hydrocarbons of the Zhujiang Formation in the Huixi half-graben were derived from source rocks of the Eocene Wenchang Formation and the Eocene-Oligocene Enping Formation in the Huizhou Sag. The hydrocarbons migrated laterally from northeast to southwest. The sandstone in the upper member of the Zhujiang Formation exhibited superior physical properties (porosity and permeability) and connectivity than the lower member. Thin sandstone beds with good physical properties and stable distribution in the upper member of the Zhujiang Formation were the main carrier beds for lateral hydrocarbon migration. [ABSTRACT FROM AUTHOR]

The regiospecific and stereoselective 1,2-migration reaction of dialkyl α-diazophosphonates for the synthesis of β-amino (E)-enylphosphonates is developed utilizing tetrakis(acetonitrile)copper(I) hexafluorophosphate [Cu(MeCN)4PF6] as the catalyst and N,N-dimethylformamide as an additive. A possible mechanism for the 1,2-migration reaction involving a metal carbene is presented. An investigation on the E/Z isomer selectivity of this process demonstrates that steric factors play an important role on the outcome. This process provides a straightforward access to β-amino (E)-enylphosphonates in moderate to good yields. [ABSTRACT FROM AUTHOR]

From the laboratory practice point of view one of the most important parameter strongly influencing the effectiveness of experiments is the dynamic of ion-selective electrode response and reaction time on main ion concentration changes in analysed solution. In this work a comparison between two analytical solutions, namely Lindner et al. and Morf et al. models, which are based on assumption of the existence of diffusion layer in analyte and numerical solution of Nernst-Planck- Poisson (NPP) system of equations for simple systems are presented. Obtained results show good agreement in potential-time response as well as in value of membrane potential in steady state for different scenarios of ionic species concentration changes. In contrast to analytical solutions, NPP model offers a description of diffusion and migration processes occurring in membrane layer as well as charge transfer kinetics at phase boundaries. [ABSTRACT FROM AUTHOR]

A straightforward N-trifluoroethylation of anilines has been developed based on silver-catalyzed N-H insertions with 2,2,2-trifluorodiazoethane (CF3CHN2). Mechanistically, the reaction is proposed to involve migratory insertion of a silver carbene as the key step. In contrast, when amides are employed as the substrates under similar reaction conditions, O-trifluoroethylation occurs to afford trifluoroethyl imidates. [ABSTRACT FROM AUTHOR]

Treatment of o-nitrostyrenes with aqueous TiCl3 solution at room temperature afforded indoles through a formal reductive C(sp2)-H amination process. A range of functions such as halides (Cl, Br), carbonyl (ester, carbamate), cyano, hydroxy, and amino groups were tolerated. From β,β-disubstituted o-nitrostyrenes, 2,3-disubstituted indoles were formed by a domino reduction/cyclization/migration process. Mild conditions, simple experimental procedure, ready accessibility of the starting materials and good to excellent yields characterize the present transformation. The methodology was used as a key step in a concise synthesis of rizatriptan and a formal total synthesis of aspidospermidine. [ABSTRACT FROM AUTHOR]

A new synthetic method is reported for the N -phosphorylation of pyrroles via intramolecular migration of a phosphonate diester group. The reaction proceeds under mild conditions and produces N -phosphorylated pyrrole derivatives in moderate to good yields. [ABSTRACT FROM AUTHOR]

Cobalt boryl complexes, which have only been sporadically reported, can be accessed systematically with remarkable (but controllable) variation in the nature of the MB bond. Complexes incorporating a very strong trans σ-donor display unparalleled inertness, reflected in retention of the MB bond even in the presence of extremely strong acid. By contrast, the use of the strong π-acceptor CO in the trans position, results in significant CoB elongation and to labilization of the boryl ligand via unprecedented CO migratory insertion. Such chemistry provides a pathway for the generation of coordinative unsaturation, thereby enabling ligand substitution and/or substrate assimilation. Alkene functionalization by boryl transfer, a well-known reaction for noble metals such as Rh or Pt, can thus be effected by an 18-electron base-metal complex. [ABSTRACT FROM AUTHOR]

Radical aryl migration reactions are of particular interest to the chemical community due to their potential application in radical chemistry and organic synthesis. The neophyl rearrangements used as radical clocks for examining the radical–molecular reactions have been known for decades. The combinations of these migrations with other radical reactions have provided a wide range of novel synthetic methodologies that are complementary to nucleophilic rearrangements. This review will give an overview of various types of radical aryl migrations, with an emphasis on their mechanistic studies from a historical point of view, as well as their application in tandem radical reactions. [ABSTRACT FROM AUTHOR]

The first highly diastereo- and enantioselective synthesis of five-membered spiro-2 H-pyrroles was achieved using an Ir-catalyzed asymmetric allylic dearomatization reaction. The spiro-2 H-pyrrole derivatives readily undergo a controllable and stereospecific allylic migration under acid catalysis, providing polycyclic pyrrole derivatives in excellent yields and ee values. Additionally, the novel Ir-complex K1, derived from [Ir(cod)Cl]2 (cod=1,5-cyclooctadiene) and N-benzhydryl- N-phenyldinaphthophosphoramidite (BHPphos), showed excellent control of both diastereo- and enantioselectivities. [ABSTRACT FROM AUTHOR]