Acenaphthenoannulation Induced by the Dual Lewis Acidity of Alumina

We have discovered a dual (i. e., soft and hard) Lewis acidity of alumina that enables rapid one-pot π-extension through the activation of terminal alkynes followed by C−F activation. The tandem reaction introduces an acenaphthene fragment – an essential moiety of geodesic polyarenes. This reaction provides quick access to elusive non-alternant polyarenes such as π-extended buckybowls and helicenes through three-point annulation of the 1-(2-ethynyl-6-fluorophenyl)naphthalene moiety. The versatility of the developed method was demonstrated by the synthesis of unprecedented structural fragments of elusive geodesic graphene nanoribbons.     

Thermal and mechanical design of tangential hybrid microchannel and high-conductivity inserts for cooling of disk-shaped electronic components

The efficiency of electronic equipment is the cornerstone of technology development. Thermal conditions significantly affect the performance of electronic components. Moreover, mechanical strength, size, and mass are the parameters that impose some limitations. Thus, they should be considered in the high tech industry. Therefore, it is needed to examine both mechanical and thermal behaviors simultaneously. Microchannel and inserted high-conductivity materials are two usual cooling approaches. To improve cooling efficiency and mechanical strength, a new method named Hybrid is introduced here. This method is a combination of microchannel and high-conductivity methods. In this study, the consumed energy, the conductivity ratio of the material with high conductivity, peak temperature, and maximum Von Mises stress have been investigated and analyzed. For the hybrid method, the peak temperature and stress were minimized regarding the volume of high-conductivity change in the tangential direction of the duct. The results showed that the tangential hybrid method could decrease the peak temperature and peak Von Mises stress, up to 40% and 34% in comparison to the microchannel and high-conductivity inserts method.

     

Association (micellization) and partitioning of aglycon triterpenoids

The reaction between methyl 4-nitrobenzenesulfonate and bromide ions has been studied in mixed single-chain-gemini micellar solutions of n-dodecyltrimethylammonium bromide, DTAB, and dodecyl tricosaoxyethylene glycol ether, Brij(35), with alkanediyl-alpha-omega-bis(dodecyldimethylammonium) bromide, 12-s-12,2Br(-) (s=3,4,5). Kinetic micellar effects show that an increase in the solution mole fraction of the single-chain surfactant, X(single-chain), results in a diminution of the mixed micelles tendency to form spherocylindrical aggregates upon increasing surfactant concentration. The dependence of the surfactant concentration at which the sphere-to-rod transition occurs, C(*), on X(single-chain) showed through kinetic data was in agreement with results obtained by means of fluorescence measurements.     

A mild and efficient approach for the selective deprotection of benzyl and phenyl trimethylsilyl ethers in 1-butyl-3-methyl-imidazolium chloride

1-Butyl-3-methyl-imidazolium chloride ([bmim]Cl) in the absence of any catalyst mediated the selective deprotection of benzyl and phenyl trimethylsilyl (TMS) ethers to the corresponding alcohols and phenol in good yields at room temperature even in presence of alkyl silyl ethers. The work-up of reactions is very simple and the products do not require further purification. The ionic liquid (IL) can be recycled and reused for several runs without any significant loss of activity. Correspondence: Ahmad Shaabani, Department of Chemistry, Shahid Beheshti University, PO Box 19396-4716, Tehran, Iran.     

Intramolecular hetero-Diels-Alder reaction of 1-oxa-1,3-butadienes with terminal acetylenes in aqueous media using CuI

A new method for the preparation of tetracyclic uracils (oxa-helicene) 4 was developed. The intramolecular hetero-Diels-Alder reaction of 1-oxa-1,3-butadiene 3 and an unactivated alkyne in the presence of CuI led to tetracyclic uracils 4 in aqueous media with good yields. The 1-oxa-1,3-butadiene 3 was prepared through Knoevenagel reaction of O-propargylated salicylaldehyde derivatives and barbituric acid or 1,3-dimethylbarbituric acid.     

Shape-Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF₆)(L)₂]_n, (L=1,4-bis(1-imidazolyl)benzene, SiF₆²⁻=SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-Cu^N, [Cu(SiF₆)(L^N)₂]_n (L^N=2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO₂. As-synthesized SIFSIX-23-Cu^N, α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N₂ (77 K), rather it reverted to α induced by CO₂ at 195, 273 and 298 K. CO₂ desorption resulted in α′, a shape-memory phase which subsequently exhibited type-I isotherms for N₂ (77 K) and CO₂ as well as strong performance for separation of CO₂/N₂ (15/85) at 298 K and 1 bar driven by strong binding (Q_st=45–51 kJ/mol) and excellent CO₂/N₂ selectivity (up to 700). Interestingly, α′ reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-Cu^N.     

毛细管电色谱和加压毛细管电色谱的进展与应用

毛细管电色谱(CEC)以内含色谱固定相的毛细管为分离柱,以电渗流为驱动力,既可以分离带电物质也可以分离中性物质。它结合了毛细管电泳和高效液相色谱两者的优点,兼具高柱效、高分辨率、高选择性和高峰容量的特点,同时具有色谱和电泳的双重分离机理。然而,“纯粹”的电色谱在实际应用中有着天然的弱点,即: 在电流通过毛细管柱中的流动相时容易产生气泡(焦耳热作用),从而使电流中断和电渗流停止,毛细管柱必须被重新用流动相润湿后方能再次使用。加压毛细管电色谱(pCEC)将液相色谱中的压力流引入CEC系统中,不仅解决了气泡、干柱等问题,而且实现了定量阀进样和二元梯度洗脱。CEC和pCEC作为微分离领域的两种前沿技术,满足了当前复杂样品分析和分析仪器微型化的需求,近年来获得了广泛的关注。本文综述了这两种技术近来的发展,包括仪器、色谱固定相的发展,总结了其在生命科学、药物分析、食品安全以及环保样品分析等方面的应用进展,评述了各方法的特点,并展望了CEC和pCEC今后的发展和应用前景。     

Fabrication and characterization of gold nanospheres‐cored pH‐sensitive thiol‐ended triblock copolymer: A smart drug delivery system for cancer therapy

Conventional chemotherapy suffers lack of multidrug resistance (MDR), lack of bioavailability, and selectivity. Nano‐sized drug delivery systems (DDS) are developing aimed to solve several limitations of conventional DDS. These systems have been offered for targeting tumor tissue owing to enhanced long circulation time, drug solubility, their retention effect, and improved permeability. As a result, the aim of this project was the design and development of DDS for biomedical applications. For this purpose, gold nanospheres (GNSs) covered by pH‐sensitive thiol‐ended triblock copolymer [poly(methacrylic acid) ‐b‐poly(acrylamide) ‐b‐poly(ε‐caprolactone)‐SH; PMAA‐b‐PAM‐b‐PCL‐SH] for delivery of anticancer drug doxorubicin (DOX). The chemical structures of triblock copolymer were investigated by proton nuclear magnetic resonance (¹H NMR) and Fourier transform infrared (FTIR) spectroscopies. ¹H NMR spectroscopy and gel permeation chromatography (GPC) were used for calculating the molecular weights of each part in the nanocarrier. The success of coating, GNSs with triblock copolymer was considered by means of dynamic light scattering (DLS), FTIR, ultraviolet‐visible (UV‐Vis), and transmission electron microscopy (TEM) measurement. The pH‐responsive drug release ability, (DOX)‐loading capacity, biocompatibility, and in vitro cytotoxicity effects of the nanocarriers were also studied. As a result, it is expected that the synthesized GNSs@polymer‐DOX considered as a potential application in nanomedicine demand like smart drug delivery, imaging, and chemo‐photothermal therapy.     

Glutathione and pH‐responsive fluorescent nanogels for cell imaging and targeted methotrexate delivery

Cancer is one of the health problems that lead to death in the world, and nanotechnology was shown to have a unique potential to improve the therapeutic efficacy of anticancer agents. The nanosized drug delivery systems (DDSs) have been offered for targeting tumor tissue because of enhanced drug bioavailability and long circulation time. In this context, we reported a facial approach to prepare a novel pH and glutathione‐responsive nanogel. After that, the nanocarriers coupled with highly fluorescent quantum dots were developed. Then methotrexate (MTX) was loaded into and on the surface of nanogels by ionic interaction so that the triggered MTX release ability of the synthesized nanocarriers was verified through the assessment of in vitro drug release at simulated tumor tissue condition. The improved efficiency of the developed nanogels and their targeted performance via conjugation of MTX (as target ligand of folate receptors) were investigated through the various cell cytotoxicity studies such as 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay, 4′6‐diamidino‐2‐phenylindole (DAPI) staining, and flow cytometry. The results of various cell cytotoxicity studies concluded that the developed smart nanogels have many promising abilities for the targeted MTX delivery to cancer tissues.     

A novel method for the synthesis of substituted 3,4-dihydrocoumarin derivatives via isocyanide-based three-component reaction

A new one-pot procedure for the efficient synthesis of novel 3,4-dihydrocoumarin derivatives using commercially available substituted 2-hydroxybenzaldehydes, Meldrum's acid, and isocyanides by a three-component condensation reaction in dichloromethane at room temperature without using any catalysts and activation was developed.