Search

Benzoxaborinines are intermediates en-route to bicyclic boronates that are important active pharmaceutical ingredients (APIs). Herein, the haloboration of o-alkynyl-phenols using BX3 (X = Cl or Br) is disclosed as a route to form C4-X-benzoxaborinines with good functional group tolerance. Computational studies indicated that there are two similar in barrier mechanisms: (i) double alkyne haloboration followed by retro-haloboration; (ii) concerted trans-haloboration involving an exogenous chloride source. The C4-halide in these benzoxaborinines is useful, with a one-pot haloboration-Negishi cross coupling protocol effective to form benzoxaborinines with an alkyl or an aryl at C4. Therefore this method is a useful addition to the toolbox for synthesizing bicyclic-boronates that are attracting increasing attention as APIs.

We have developed a generalizable strategy to quantify the effect of surface barriers on zeolite catalysis. Isomerization of n‐pentane, catalyzed by Pt/Beta, is taken as a model reaction system. Firstly, the surface modification by chemical liquid deposition of SiO2 was carried out to control the surface barriers on zeolite Beta crystals. The deposition of SiO2 leads to a very slight change in the physical properties of Beta crystals, but an obvious reduction in Brønsted acid sites. Diffusion measurements by the zero‐length column (ZLC) method show that the apparent diffusivity of n‐pentane can be more than doubled after SiO2 deposition, indicating that the surface barriers have been weakened. Catalytic performance was tested in a fixed‐bed reactor, showing that the apparent catalytic activity improved by 51–131 % after SiO2 deposition. These results provide direct proof that reducing surface barriers can be an effective route to improve zeolite catalyst performance deteriorated by transport limitations., External surface diffusion barriers on zeolite Beta crystals significantly reduce their apparent catalytic activity in catalyzing isomerization of n‐pentane. Eliminating surface barriers can lead to an improvement in apparent catalytic activity higher than 131 %.

Pyrazabole ( 1 ) is a readily accessible diboron compound that can be transformed into ditopic electrophiles. In 1 (and derivatives), the B∙∙∙B separation is ca. 3 Å, appropriate for one boron centre bonding to N and one to the C7 of indoles and indolines. This suitable B∙∙∙B separation enables double E-H (E = N/C) functionalisation of indoles and indolines. Specifically, the activation of 1 with HNTf 2 generates an electrophile that transforms N-H indoles and indolines into N/C7-diborylated indolines, with N-H borylation directing subsequent C7-H borylation. Indole reduction to indoline occurs before C-H borylation and our studies indicate this proceeds via hydroboration - C3-protodeboronation to produce an intermediate that then undergoes C7 borylation. The borylated products can be converted in-situ into C7-BPin-N-H-indolines. Overall, this represents a transient directed C-H borylation to form useful C7-BPin-indolines.

Background and purpose There are limited data on the association between uric acid (UA) and symptomatic intracranial haemorrhage (SICH) in patients who have undergone mechanical thrombectomy [endovascular treatment (EVT)]. In the present study, we aimed to investigate the role of serum UA level in SICH after EVT in a real-world practice. Methods Patients were selected from the Endovascular Treatment for Acute Anterior Circulation Ischemic Stroke (ACTUAL) registry. SICH was identified using the Heidelberg Bleeding Classification. Multivariable logistic regression analysis was performed to explore the relationship between serum UA and SICH. Results Among 611 enrolled patients, 90 (14.7%) were diagnosed with SICH within 72 h after EVT. Patients with SICH had a significantly higher level of serum UA (median, 341.0 vs. 302.0 μmol/L; P = 0.003) than those without SICH. Univariate logistic regression analysis indicated that patients with UA levels in the fourth quartile, compared with the first quartile, were more likely to have SICH (odds ratio, 2.846; 95% confidence intervals, 1.429-6.003; P = 0.003). The association remained significant after multivariable adjustment for potential confounders. Furthermore, the multiple-adjusted spline regression model showed an inverted U-shaped association between UA and SICH (P = 0.047 for non-linearity). Conclusion Our study indicated that increased serum UA level was independently associated with SICH after EVT in acute ischaemic stroke.

A versatile pore network model is used to study deactivation by coking in a single catalyst particle. This approach allows to gain detailed insights into the progression of deactivation from active site, to pore, and to particle – providing valuable information for catalyst design. The model is applied to investigate deactivation by coking during propane dehydrogenation in a Pt‐Sn/Al2O3 catalyst particle. We find that the deactivation process can be separated into two stages when there exist severe diffusion limitation and pore blockage, and the toxicity of coke formed in the later stage is much stronger than of coke formed in the early stage. The reaction temperature and composition change the coking rate and apparent reaction rate, informed by the kinetics, but, remarkably, they do not change the capacity for a catalyst particle to accommodate coke. On the other hand, the pore network structure significantly affects the capacity to contain coke.

Naphthalene and acenaphthene with peri 2-py and BMes2 (py=pyridyl, Mes=mesityl) substituents have been found to undergo facile phototransformation, cleavage of a C-C bond of naphthalene, and formation of 2-py-bound benzoborepins as the major products. Mechanistic pathways of this photoreaction have been established by examination of both excited and ground states by using CASSCF and CASPT2 methods in DFT and time-dependent DFT calculations. The mesityl to py-naphthyl charge-transfer transition and the mesityl migration from the boron atom to the naphthyl moiety drive this unprecedented C-C bond cleavage and boron-insertion reaction.

An innovative intensified vitamin E (VE) recovery process from the methylated oil deodorizer distillates (MODDs) was proposed, where VE was in situ transferred into a deep eutectic solvent (DES) with an organic salt. To design the process, the chlorine based quaternary ammonium salts were primarily investigated, and [N4,4,4,4]Cl was selected as an association solvent which can efficiently form DES with α-tocopherol of the representative compound of VE. Based on the determined phase diagram of the DES freezing points, four phase regions were classified, and the effect of the [N4,4,4,4]Cl/tocopherol ratio and temperature on the extraction performance and phase transformation was figured out. Moreover, an intensified association extraction process via in situ forming DES of α-tocopherol with [N4,4,4,4]Cl was designed and validated by experiments. VE products were finally obtained from both model MODD (purity of 99.63%) and practical MODDs (purity of >79.18%), which verifies the excellent extraction efficiency for the proposed recovery method. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2212–2220, 2017

Managing the interference effects from thin (multi‐)layers allows for the control of the optical transmittance/reflectance of widely used and technologically significant structures such as antireflection coatings (ARCs) and distributed Bragg reflectors (DBRs). These rely on the destructive/constructive interference between incident, reflected, and transmitted radiation. While known for over a century and having been extremely well investigated, the emergence of printable and large‐area electronics brings a new emphasis: the development of materials capable of transferring well‐established ideas to a solution‐based production. Here, demonstrated is the solution‐fabrication of ARCs and DBRs utilizing alternating layers of commodity plastics and recently developed organic/inorganic hybrid materials comprised of poly(vinyl alcohol) (PVAl), cross‐linked with titanium oxide hydrates. Dip‐coated ARCs exhibit an 88% reduction in reflectance across the visible compared to uncoated glass, and fully solution‐coated DBRs provide a reflection of >99% across a 100 nm spectral band in the visible region. Detailed comparisons with transfermatrix methods (TMM) highlight their excellent optical quality including extremely low optical losses. Beneficially, when exposed to elevated temperatures, the hybrid material can display a notable, reproducible, and irreversible change in refractive index and film thickness while maintaining excellent optical performance allowing postdeposition tuning, e.g., for thermo‐responsive applications, including security features and product‐storage environment monitoring.

The effects of the catalyst pore network structure on multiphase reactions in catalyst pellets are investigated by using the experimentally validated pore network model proposed in our recent work (AIChE J, 62, 451, 2016). The simulations display hysteresis loops of the effectiveness factor. The hysteresis loop area becomes significantly larger, when having small volume-averaged pore radius, wide pore-size distribution, and low pore connectivity; however, the loop area is insensitive to pellet size, even though it affects the value of the effectiveness factor. The hysteresis loop area is also strongly affected by the spatial distribution of the pore size, in particular for a bimodal pore-size distribution. The pore network structure directly influences mass transfer, capillary condensation, and pore blocking, and subsequently passes these influences on to the hysteresis loop of the effectiveness factor. Recognizing these effects is essential when designing porous catalysts for multiphase reaction processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 78–86, 2017.

Selective acetylene hydrogenation over a commercial Pd-Ag/Al2O3 catalyst was carried out under industrial operation conditions that correspond to the “tail-end” process. Pyrolysis gas chromatography-mass spectrometry was used to analyze the composition of the green oil. C8–C30 linear hydrocarbons with even carbon-numbered chains were detected as the main components of the green oil. Its chain length increased with operating time, temperature, and hydrogen partial pressure, and decreased with acetylene partial pressure. The composition of the green oil deviates from the Anderson-Schulz-Flory distribution. Both coupling-hydrogenation and hydrogenation-coupling mechanisms are involved in green oil formation.

A discrete model coupling mass transfer, reaction, and phase change in porous catalyst particles is proposed to probe pore blocking effects on multiphase reactions. This discrete model is validated by comparing the results with experiments and those obtained using a continuum model, for the hydrogenation of benzene to cyclohexane in Pd/γ-alumina catalyst particles. The results show that pore blocking has a significant effect on the effectiveness factor and can contribute to up to 50% of the hysteresis loop area for multiphase reactions in porous catalysts, indicating that pore blocking must be accounted for. Moreover, the pore blocking effects are significantly enhanced when the pore network is poorly connected and the pore size distribution is wide, while the pore blocking effects are insensitive to the volume-averaged pore size. Multiphase catalyst material characterization and design should account for this effect. This article is protected by copyright. All rights reserved.

The reaction kinetics of the pyrolysis of heavy oil in the presence of supercritical water (SCW) and high pressure N2 were measured. At any reaction temperature applied, the pyrolysis under SCW environments is faster than that under N2 environments. Meanwhile, at lower temperatures the pyrolysis under both environments is accelerated by the introduction of coke into the feedstock. On the basis of a first-order four-lump reaction network consisting of the sequential condensation of maltenes and asphaltenes, the pyrolysis in whichever medium can be preferably described either by the lumped reaction kinetic model modified with autocatalysis and pseudoequilibrium or by the model modified solely with pseudoequilibrium. Benefited from the reduced limitation of diffusion to reaction kinetics, the pyrolysis in the SCW phase is more sensitive to the increase in reaction temperature than that in the oil phase, disengaging readily from the dependence on autocatalysis at a lower temperature. © 2015 American Institute of Chemical Engineers AIChE J, 62: 207–216, 2016

The ability to modify or enhance the dielectric constant of semiconducting polymers can prove valuable for a range of optoelectronic and microelectronic applications. In the case of organic photovoltaics, increasing the dielectric constant of the active layer has often been suggested as a method to control charge generation, recombination dynamics, and ultimately, the power conversion efficiencies. In this contribution, the impact that the degree and pattern of fluorination has on the dielectric constant of poly(3‐octylthiophene) (P3OT), a more soluble analogue of the widely studied conjugated material poly(3‐hexylthiophene), is explored. P3OT and its backbone‐fluorinated analogue, F‐P3OT, are compared along with a block and alternating copolymer version of these materials. It is found that the dielectric constant of the polymer thin films increases as the degree of backbone fluorination increases, in a trend consistent with density functional theory calculations of the dipole moment.

In the presence of supercritical water (SCW) and N2, the pyrolysis of heavy oil was investigated to distinguish the difference in the reaction kinetics between the upgrading in the SCW and oil phases. The pyrolysis in the SCW phase is faster than that in the oil phase, but the reaction in whichever phase is retarded by vigorous stirring. The pyrolysis can be preferably described by a four-lump kinetic model consisting of the condensation of maltenes and asphaltenes in series. In the SCW phase, highly dispersed asphaltenes are isolated by water clusters from maltenes dissolved in SCW surroundings, by which the condensation of asphaltenes is drastically accelerated. Benefited from excellent mass transfer environments in SCW, the condensation of maltenes is promoted simultaneously. The introduction of SCW into the pyrolysis of heavy oil results in an effectively increased upgrading efficiency, but its influence on the properties of equilibrium liquid products is minor. © 2014 American Institute of Chemical Engineers AIChE J, 61: 857–866, 2015

A continuous polycondensation process for polyethylene adipate in a bubbling reactive distillation tower with six trays allowed achieving high conversion of carboxyl end groups within short residence times. Influences of different operating conditions including residence time, reaction temperature, pressure, etc. on reactor performance were investigated by experimental and simulation analyses. Optimal conditions for polyethylene adipate continuous polycondensation in the bubbling reactive distillation tower reactor were defined and applied to the process.

The combined elimination of NO and SO2 can be realized by hexamminecobalt(II) solution. Activated carbon is utilized to catalyze the reduction of hexamminecobalt(III) (Co(NH3)63+) to hexamminecobalt(II) (Co(NH3)62+), so as to maintain a high NO removal efficiency for a long time. K2S2O8 solution has been tried to modify coconut activated carbon to enhance its catalytic capability in the reduction of hexamminecobalt(III). The experiments have been performed in a stirred cell to investigate the effects of K2S2O8 concentration, impregnation temperature, and impregnation time on the catalytic ability of activated carbon. The results showed that the best K2S2O8 concentration for the improvement of activated carbon is 0.3 mol L−1. The optimal impregnation temperature was 40°C. The optimum impregnation duration was 9 h. After treated with K2S2O8 solution, the surface area of activated carbon decreased. But the acidity on its surface was enhanced, which played a crucial role in improving the catalytic capacity of activated carbon in the reduction of Co(NH3)63+. The experimental results showed that the modified carbon could obtain a higher NO removal efficiency than the original carbon. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 65–73, 2015

NO and SO2 can be removed simultaneously by [Fe(II)EDTA]2− solution. Activated carbon is used to catalyze the regeneration of [Fe(II)EDTA]2− to maintain the NO removal efficiency at a high level for a long time. In this article, ammonia solution has been tried to modify the coconut activated carbon to ameliorate its catalytic capability in the regeneration of [Fe(II)EDTA]2−. Experiments have been made in a batch stirred cell to investigate the effects of modification conditions, such as ammonia concentration, impregnation time, activation temperature, and activation time, on the catalytic performance of activated carbon. The experimental results suggest that the optimal modification condition be illustrated as follow: ammonia concentration 9.0 mol L−1, impregnation time 11 h, activation temperature 700°C, and activation time 4 h. After ammonia modification, the surface area of activated carbon decreases. But the total basicity of activated carbon is enhanced, which plays a vital role in improving the catalytic capability of activated carbon in the reduction of [Fe(III)EDTA]−. The activated carbon modified by ammonia solution can get a higher NO removal efficiency than the original activated carbon. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 99–106, 2014

We report the first examples of straightforward trans-hydroboration of internal alkynes at room temperature with 9-BBN, producing five-membered BN-heterocycles. Contrary to conventional cis-hydroboration, we demonstrate that the introduction of a pyridyl group switches the stereoselectivity of the reaction. A hydride migration mechanism has been proposed and supported by DFT calculations for the trans-hydroboration. This new hydroboration approach allows facile construction of new blue fluorescent BN-heterocyclic compounds.

Background: Early detection trials with chest radiography and sputum cytology were ineffective in decreasing lung cancer mortality. The advent of low-dose spiral chest computed tomography (LDCT) provided clinicians with a new tool that could be with early diagnosis; however, this also raised significant concerns regarding the systematic use of LDCT with its high false-positive rate for benign nodules. At this time, there is limited information about the true role of PET (positron emission tomography) for early detection of lung cancer. Methods: We used systematic methods, including Preferred Reporting Items for Systematic reviews and Meta-Analyses statement, to identify relevant studies, assess study eligibility, evaluate study methodological quality, and summarize findings regarding diagnostic accuracy and outcome. Results: In total, only seven eligible studies were selected from 82 potentially relevant studies. The sensitivity of 18F-FDG-PET for the detection of T1 lung cancers ranged between 68% and 95%. The rate of detection tended to be lower for carcinoid tumors, adenocarcinoma and bronchoalveolar cell carcinomas. FDG-PET using SUV (standardized uptake value) level can predict the outcome of the screening detected lung cancer. A combination of FDG-PET and LDCT may improve screening for lung cancer in high-risk patients. Conclusions: PET or PET/CT may be used as a useful tool for early detection of lung cancer in high-risk population based on the existing information. However, there is still limited information with regards to evidence of survival benefits from PET screening in high-risk patients. Please cite this paper as: Chang C-Y, Chang S-J, Chang S-C and Yuan M-K. The value of positron emission tomography in early detection of lung cancer in high-risk population: a systematic review. Clin Respir J 2013; 7: 1–6.

In this study, the adsorption of [Fe(III)–EDTA]− on coconut-activated carbon from aqueous solutions has been studied in a batch stirred cell. Experiments have been carried out to investigate the effects of temperature, [Fe(III)–EDTA]− concentration, pH, and activated carbon mass on [Fe(III)–EDTA]− adsorption. The experimental results manifest that high temperature is favorable to the adsorption of [Fe(III)–EDTA]− on the activated carbon. The [Fe(III)–EDTA]− adsorption on activated carbon increases with its concentration in the aqueous solutions. However, the [Fe(III)–EDTA]− adsorption on activated carbon decreases as the pH rises. The [Fe(III)–EDTA]− adsorption on per gram of activated carbon decreases as the activated carbon mass increases. The kinetic study shows that [Fe(III)–EDTA]− adsorption on the activated carbon is in good compliance with the pseudo-second-order kinetic model. The Langmuir and Freundlich equilibrium isotherm models are found to provide a good fitting of the adsorption data. Thermodynamic parameters such as Ea, ΔG0, ΔH0, and ΔS0 for adsorption reaction are estimated. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 470–479, 2013