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91.
An efficient method for the preparation of 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepine derivatives under mild conditions has been developed. The reaction of 2‐(2‐aminophenyl)ethanols 1 with acid chlorides in the presence of excess Et3N in THF at room temperature gave the corresponding N‐acylated intermediates 2 , which were dehydrated by treatment with POCl3 to give 2‐substituted 4‐aryl‐4,5‐dihydro‐3,1‐benzoxazepines 3 in a one‐pot reaction. 相似文献
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94.
J. Garcia-Guinea E. Crespo-Feo V. Correcher A. Cremades J. Rubio L. Tormo P.D. Townsend 《Radiation measurements》2009,44(4):338-343
An historic Strontianite-type specimen from Strontian, Scotland, UK, was characterized to broaden our knowledge on luminescence properties of common carbonates. These fibrous aggregates are Strontianite (SrxCa1−xCO3) with circa 6% of CaO, interfacial water, hydrosilicate anions and substitutional divalent cations, e.g., Ca2+, Mn2+, Fe2+ in structural Sr2+ positions. The specimen was analyzed by X-ray Fluorescence Spectrometry (XRF), Environmental Scanning Electron Microscopy coupled with an Energy Dispersive X-ray Spectroscopy (ESEM-EDS) probe, Spatially-resolved Cathodoluminescence under the Scanning Electron Microscope (SEM-CL), Differential-Thermal Analyses (DTA), Thermogravimetry (TG), Thermoluminescence (TL), Radioluminescence (RL) and High Resolution Spectra Thermoluminescence (3DTL), to gain an overview of the spectral emissions, the defect linkages were modified by heating from room temperature (RT) up to 500 °C. Substitutional transition elements are probably responsible for the spectral emission bands from 500 nm to 800 nm and hydrous molecules from 300 nm to 400 nm. DTA–TG analyses performed on little chips, to preserve the fiber interfaces coherence, exhibit minor endothermic peaks attributed to outflow of water groups in fiber interfaces. Both, CL and RL curves show common spectral positions but UV–blue and red emission intensities are counterbalanced since electron irradiation reduces the UV–blue emissions while X-irradiation increases them. The TL curves show a top thermal limit at 300 °C for the 300–400 nm TL emissions which become irreversibly destroyed, whereas the longer wavelength region emits at higher temperature. The non-reversible changes observed in the 320 nm and 360 nm bands during the spectra 3DTL emission could be linked with non-bridging oxygen defects, protons and hydroxyl groups and the red emissions to the 4G (4T1g)–6S Mn2+ ion transition. Following assignations and similar spectral CL patterns of Russian Strontianite samples, the emission-defect assignments: Dy3+ 480 nm; Tb3+ 540 nm; Dy3+ 580 nm and Sm3+ 640 nm cannot be disregarded. 相似文献
95.
Under mild conditions, conversion of a variety of ketoximes and aldoximes to their corresponding amides and nitriles proceeded in the presence of PEG-SO3H with high yields. 相似文献
96.
Composite membranes prepared from poly(vinyl alcohol) and poly(sulfone) were crosslinked with trimesoyl chloride (TMC) solutions. The degree of crosslinking, crystallinity, surface roughness and hydrophobicity of the crosslinked PVA–PSf membranes were determined from attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), atomic force microscopy (AFM) and contact angle measurements, respectively. Results showed a consistent trend of changes in the physicochemical properties: the degree of crosslinking, crystallinity, surface roughness, hydrophobicity and swelling degree all decrease with increasing crosslinking agent (TMC) concentration and reaction time. The crosslinked membrane performance was assessed with pervaporation dehydration of ethylene glycol solutions at a range of concentrations (30–90 wt% EG) in the feed mixtures. The total flux of permeation was found to decrease, while the selectivity to increase, with increasing TMC concentration and reaction time. The decrease in flux was most prominent at low EG concentrations in the feed mixtures. In addition, the temperature effect on the pervaporation dehydration was investigated in relation to solution–diffusion mechanisms. 相似文献
97.
Bao-Jian Pei 《Tetrahedron letters》2010,51(34):4519-1777
Microwave-irradiated Diels-Alder reactions of anthracene and endoxides (6a-g) in water afforded the cycloadducts (8a-g) with high efficiencies. The extended triptycenes (2a-g) were readily obtained by dehydration of 8a-g in a mixture of AcOH and Ac2O with good overall yields. 相似文献
98.
改善SBA-15介孔材料水热稳定性的简单溶剂热后处理方法 总被引:1,自引:0,他引:1
提出了一种有效改善SBA-15介孔材料水热稳定性的简单溶剂热后处理方法. SBA-15材料经环己烷、甲苯和正丁醇等有机溶剂在157和190 oC密闭容器中分别处理6–24 h后,可呈现很好的水热稳定性.它们在800 oC经100%水蒸气处理12 h,依然能保持很好的有序介孔结构,比表面积可高达192–281 m2/g.其中,经环己烷190 oC溶剂热处理24 h的样品表现出最优的水热稳定性.溶剂热处理能显著提升材料孔壁中类似Si(OSi)2(OH)2和Si(OSi)3OH结构的Si–OH基间脱水,形成稳定的Si(OSi)4结构,从而有效减少了SBA-15材料孔壁的缺陷.由此,介孔材料的水热稳定性得到明显改善.溶剂热处理对SBA-15材料水热稳定性的这种提升作用与所用溶剂性质、处理温度以及SBA-15前驱体的类型密切相关.其中,以低沸点的非极性溶剂处理焙烧后的SBA-15材料表现出最好的稳定化效果.该方法具有简单、低能耗的特点,其在制备高水热稳定的有序硅基介孔材料上有很好的潜在应用价值. 相似文献
99.
Sumit Dey 《Tetrahedron letters》2007,48(14):2573-2575
A one-pot synthesis of the substituted furans 3 could be achieved in good yields by reacting but-2-ene-1,4-diones 1 with acetoacetates 2 in the presence of a catalytic amount of InCl3 (20 mol %) using i-PrOH as solvent at 80-90 °C for 4-8 h. InCl3 was observed to give the optimum results among the various Lewis acids examined. 相似文献
100.
Jan Greve 《Journal of solid state chemistry》2003,175(2):328-340
The three new isostructural coordination polymers poly[diaqua-(μ2-squarato-O,O′)-(μ2-4,4′-bipyridine-N,N′)Me(II)] hydrate (Me=Fe, Co, Ni) were prepared by hydrothermal reaction. All compounds are isostructural and crystallize in the monoclinic space group P21/c with 4 formula units in the unit cell (a=18.893 (1) Å, b=11.450 (1) Å, c=8.0985 (4) Å, β=93.032 (5)°, V=1749.5 (2) Å3, [Fe(C4O4)(C10H8)(H2O)2]·(H2O)3; a=18.937 (1) Å, b=11.342 (1) Å, c=8.0545 (5) Å, β=91.83 (1)°, V=1725.3 (2) Å3, [Co(C4O4)(C10H8)(H2O)2] · (H2O)3; a=18.271 (1) Å, b=11.340 (1) Å, c=7.8946 (4) Å, β=90.69 (5)°, V=1633.1 (2) Å3, [Ni(C4O4)(C10H8)(H2O)2](H2O)1.7). In the crystal structures the metal atoms are coordinated by two squarate dianions, two 4,4′-bipyridine ligands and two water molecules. The metal atoms are connected via the squarate dianions and the 4,4′-bipyridine ligands into layers, which interpenetrate forming a three-dimensional coordination network. This arrangement yields channels in which additional water molecules are embedded. Thermoanalytic investigations show that upon heating the channel water is removed in the first step and that the water coordinated to the metal atoms is emitted in the second step. Both steps are fully reversible with the former reaction proceeding via a topotactic reaction. The hydration and dehydration of the compounds are accompanied with a continuous change of the color of the materials. The de- and reintercalation processes were investigated using single crystal structure analysis, X-ray powder diffraction, temperature-dependent X-ray powder diffraction, simultaneous differential thermoanalysis and thermogravimetry coupled to mass spectroscopy, differential scanning calorimetry and time-dependent UV-Vis spectroscopy. The results of the investigations are discussed and compared with those for the previously reported manganese compound. 相似文献