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1.
Char barrier effect of graphene nanoplatelets on the flame retardancy and thermal stability of high‐density polyethylene flame‐retarded by brominated polystyrene 下载免费PDF全文
Graphene nanoplatelets (GNPs) with the char barrier effect were combined with brominated polystyrene (BPS) and antimony trioxide (Sb2O3) to improve the flame retardancy and thermal stability of high‐density polyethylene. Thermogravimetric analysis, limited oxygen index (LOI) testing, and vertical burning testing (UL‐94) showed that the presence of GNPs led to enhanced thermal oxidation stability and significantly reduced the flammability. The addition of 1 wt % GNPs to polyethylene/BPS–Sb (mass ratio = 92/6/2) led to UL‐94 grades from NG (first burning time > 30 s) to V‐2 (total burning time = 14 s), and the LOI value increased from 23.4 to 24.1%. The results of the pyrolysis products provided evidence that the GNPs restricted volatilization. The morphology of the chars also proved the formation of the char layer, which could act as a barrier to isolate the material from the flame and retard the vaporization of flammable gases via a tortuous pathway. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40520. 相似文献
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Blends of polystyrene (PS) with polyolefin elastomer (POE) were prepared by a reactive extrusion method. In order to increase the compatibility of the two blending components, a Lewis acid catalyst, aluminium chloride (AlCl3), was adopted to initiate the Friedel–Crafts alkylation reaction. Fourier‐transform infrared (FTIR) spectra of the PS/POE/AlCl3 blends extracted with butanone verified the graft structure between the PS and POE. Because the in situ generated PS‐graft‐POE copolymers acted as compatibilizers, the mechanical properties of PS/POE blends were greatly improved. For example, after compatibilization, the Charpy impact strength of an 80/20 (wt%) PS/POE blend was increased from 6.29 to 8.50 kJ m?2. Scanning electron microscopy (SEM) showed that the size of the droplets decreased from 9–10 µm to less than 2 µm with the addition of AlCl3. Gel permeation chromatography (GPC) showed competition between the grafting reaction and the degradation of blending components in the presence of AlCl3. Copyright © 2005 Society of Chemical Industry 相似文献
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Polyolefin/polystyrene (PS) blends are difficult to compatibilize using in situ reactive compatibilization techniques, because neither of these polymers has any functional groups that one can use in the formation of a copolymer from these polymer components. In this study, the Friedel–Crafts alkylation was realized in a polyethylene/PS (PE/PS) melt blend, which resulted in improved compatibility between PE and PS. A number of Lewis acid compounds were tested as catalysts, among which the AlCl3 was the most efficient. It was found in this study that the presence of a cocatalyst, such as a cationically polymerizable monomer or a halogenated alkane, significantly enhances the formation of PE-g-PS copolymer. The effects of blending parameters, such as temperature and blending time, on the in situ copolymer formation were investigated. The mechanical properties of compatibilized PE/PS blends were improved considerably. Such an in situ compatibilization technique has potential in the recycling of mixed polymer wastes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1385–1393, 1997 相似文献
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Yan‐Chao Wu Hui‐Jing Li Li Liu Nicolas Demoulin Zhe Liu Dong Wang Yong‐Jun Chen 《Advanced Synthesis \u0026amp; Catalysis》2011,353(6):907-912
The direct Friedel–Crafts reaction of chromene hemiacetals with indoles, furans and sterically hindered anilines has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of hafnium triflate [Hf(OTf)4, 0.1 mol%, 0–40 °C]. The mild conditions tolerate various sensitive functional and protecting groups, and the products were confirmed unambiguously from their spectra and by single‐crystal X‐ray analysis. This direct Friedel–Crafts reaction of chromene hemiacetals should inspire and encourage the consideration of hafnium triflate in the development of mild reaction conditions for the efficient derivatization of hemiacetal‐containing compounds. 相似文献
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Fabrice Dumont Fabienne Duriau-Montagne Denise Baudry Alain Dormond 《Polymer International》1999,48(3):165-170
Soluble polybenzyls were prepared by a catalytic electrophilic Friedel–Crafts type polycondensation between α,α′-dichloro-p-xylene and substituted (by an alkyl or an alkoxy side-chain) mesitylene. The influence of the length of the side-chain on the solubility of the polymer was examined. The polymers were found to be soluble in common organic solvents. Polymer characterizations were made by 13C nuclear magnetic resonance spectroscopy (NMR), size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and elemental analysis. © 1999 Society of Chemical Industry 相似文献
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Jing Deng Shilei Zhang Peng Ding Hualiang Jiang Wei Wang Jian Li 《Advanced Synthesis \u0026amp; Catalysis》2010,352(5):833-838
The first direct enantioselective Friedel–Crafts reaction of indoles with isatins has been developed. The process is catalyzed by simple cupreine under mild reaction conditions and affords synthetically and biologically interesting, chiral 3‐indolyl‐3‐hydroxy‐2‐oxindoles in good yields (68–97%) and with high enantioselectivities (76–91%). 相似文献
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A one‐pot synthesis of dihydroindenes from substituted benzenes and haloalkenes was developed. The reaction proceeded via a copper(II) triflate [Cu(OTf)2]‐catalyzed tandem Friedel–Crafts alkylation/cyclization process with high efficiency under relatively mild conditions. 相似文献
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An efficient and expeditious boron trifluoride etherate (BF3⋅Et2O) catalyzed one‐pot reaction for the synthesis of N‐tosyl‐9‐aminofluorenes and anthracene derivatives from in situ generated N‐tosylbenzaldimines via an aza‐Friedal–Crafts reaction has been developed. The catalytic reaction shows high substrate tolerance with excellent yields. 相似文献
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Bisoxazolidine 1 is an effective ligand in the copper(I)‐catalyzed Friedel–Crafts reaction of alkyl trifluoropyruvates and indoles. A range of ethyl 2‐(3′‐indolyl)‐3,3,3‐trifluoro‐2‐hydroxypropanoates was produced in up to 99% yield and 94% ee within 30 min to 4 h. The effect of temperature on conversion and enantioselectivity proved to be substrate specific and was optimized individually. Of particular interest is that this method tolerates the presence of substituents in various positions in the indole ring. Yields ranging from 90–97% and ee values between 90 and 94% were obtained at optimized temperatures with substrates carrying substituents in position 1 or 7. 相似文献
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Liang Wu Ren‐Rong Liu Guoqi Zhang Dan‐Jie Wang Hao Wu Jianrong Gao Yi‐Xia Jia 《Advanced Synthesis \u0026amp; Catalysis》2015,357(4):709-713
An enantioselective Friedel–Crafts alkylation reaction of indoles with cyclic N‐sulfonyl ketimino esters was developed. Under the optimized conditions using a chiral copper(II) triflate‐bisoxazoline complex as the catalyst, a range of N‐sulfonyl ketimino ester derivatives and indoles reacted smoothly to afford indole‐containing chiral cyclic α‐amino esters bearing tetrasubstituted α‐stereogenic centers [3‐ethoxycarbonyl‐3‐(3‐indolyl)‐2,3‐dihydrobenzo[d]isothiazole 1,1‐dioxides] in excellent yields and with high enantioselectivities (up to 99% ee). Pyrrole and N,N‐dimethylaniline were also investigated as aromatic substrates to afford the corresponding products with good results. An asymmetric induction model was then proposed on the basis of the observed absolute configuration of the product 3‐ethoxycarbonyl‐3‐(5‐bromo‐3‐indolyl)‐2,3‐dihydrobenzo[d]isothiazole 1,1‐dioxide. Synthetic transformations to convert the products into cyclic chiral N‐sulfonamido alcohols and the deprotection of the sulfonamides were performed. This study provides an efficient approach to chiral α‐tetrasubstituted indolic α‐amino acids as potential building blocks for peptides and biologically active molecules.
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Shuichi Nakamura Kengo Hyodo Yuko Nakamura Norio Shibata Takeshi Toru 《Advanced Synthesis \u0026amp; Catalysis》2008,350(10):1443-1448
Enantioselective Friedel–Crafts alkylations of a variety of indoles with ethyl 3,3,3‐trifluoropyruvate catalyzed by novel chiral m‐phenylenebis(imidazoline)‐copper(II) complexes or the bis(imidazoline)‐achiral acid combination afforded products with high enantioselectivity. Both enantiomers of indole derivatives can be prepared with high enantioselectivities by tuning the N‐substituents of the imidazoline. 相似文献
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Yuhua Lu Xiangwei Du Xueshun Jia Yuanhong Liu 《Advanced Synthesis \u0026amp; Catalysis》2009,351(10):1517-1522
An efficient domino approach for the synthesis of indole‐fused carbocycles and their analogues from the reactions of suitably substituted (Z)‐enynols with indoles or pyrroles under mild reaction conditions was developed. This methodology is realized by a tandem reaction using Au/Ag catalysts, which could catalyze both of the Friedel–Crafts and the hydroarylation reaction in the same vessel. 相似文献
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Magnus Rueping Sadiya Raja Alberto Núez 《Advanced Synthesis \u0026amp; Catalysis》2011,353(4):563-568
A new enantioselective Brønsted acid‐catalyzed Friedel–Crafts reaction of indole with cyclic imines has been develeoped. This organocatalytic reaction provides for the first time optically active indolindolinone derivatives in high yields and with excellent enantioselectivities (up to 91% ee) under mild reaction conditions. 相似文献
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Congde Huo Cheng Wang Chougu Sun Xiaodong Jia Xicun Wang Wenju Chang Mingxia Wu 《Advanced Synthesis \u0026amp; Catalysis》2013,355(10):1911-1916
A novel and efficient stable radical cation triarylaminium salt‐catalyzed aerobic double Friedel–Crafts alkylation reaction of glycine derivatives with indoles has been developed. The reaction was performed in the absence of any other additives under mild conditions and only requires an air atmosphere (or oxygen, 1 atm) as co‐oxidant. 相似文献
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Yonghai Hui Weiliang Chen Wentao Wang Jun Jiang Yunfei Cai Lili Lin Xiaohua Liu Xiaoming Feng 《Advanced Synthesis \u0026amp; Catalysis》2010,352(18):3174-3178
A highly enantioselective Friedel–Crafts alkylation of indoles with ethyl trifluoropyruvate has been developed using N,N′‐dioxide‐zinc(II) complexes. Both enantiomers of the desired adducts were obtained by the use of enantiomeric ligands in excellent results (up to 99% yield and 98% ee) within 0.5 h under mild conditions. On the basis of the experimental results, a proposed working model was proposed to explain the origin of the asymmetric induction. 相似文献
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Yan‐Jin Sun Nan Li Zhong‐Bo Zheng Lei Liu Yan‐Bo Yu Zhao‐Hai Qin Bin Fu 《Advanced Synthesis \u0026amp; Catalysis》2009,351(18):3113-3117
A series of cheap and easily accessible heteroarylidenemalonate‐derived bis(oxazoline) ligands 1 and 2 were synthesized and their copper(II) complexes were applied to the catalytic Friedel–Crafts reaction between indoles and diethyl alkylidenemalonates, Excellent asymmetric enantioselectivities were afforded for the S‐enantiomer (up to >99% ee) in isobutyl alcohol, and the R‐enantiomer (up to 96.5% ee) in dichloromethane. 相似文献
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Ming‐Hua Zhuo Guo‐Feng Liu Shan‐Liang Song Dong An Jigang Gao Liangyu Zheng Suoqin Zhang 《Advanced Synthesis \u0026amp; Catalysis》2016,358(5):808-815
The first enantioselective Friedel–Crafts alkylation of indoles and pyrroles with 3‐hydroxy‐3‐indolyloxindoles to access two novel types of 3,3‐diaryloxindoles catalyzed by chiral imidodiphosphoric acids has been reported. A range of quaternary carbon centered 3,3‐diaryloxindoles were synthesized in high yield (up to >99%) with excellent enantioselectivity (up to 98% ee) at low catalyst loadings (as low as 0.5 mol%). The Friedel–Crafts reaction between indoles and 3‐hydroxy‐3‐indolyloxindoles is amenable to gram scale syntheses.
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Hashem Sharghi Mahboubeh Jokar Mohammad Mahdi Doroodmand Reza Khalifeh 《Advanced Synthesis \u0026amp; Catalysis》2010,352(17):3031-3044
Catalytic Friedel–Crafts acylation of benzene and unactivated benzenes such as chlorobenzene and nitrobenzene have been successfully carried out using activated hematite (α‐Fe2O3) as a new, heterogeneous and green catalyst. Sonication of neat α‐Fe2O3 in a water bath under air atmosphere at room temperature followed by heating at 200 °C, dramatically increase the activity of α‐Fe2O3. With the catalyst loading as low as 5.0 mol%, a wide variety of benzene derivatives were easily converted into the corresponding acylated products in a clean and high‐yielding acylation reaction. It was found that the activated α‐Fe2O3 could be efficiently recycled and reused several times by simple washing with ethyl acetate, this cannot be attained with most of the traditional catalysts. 相似文献