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671.
Judiciously balancing steric and electronic influences on 2,3‐diiminobutane‐based Pd(II) complexes in nourishing polyethylene properties
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Yanning Zeng Qaiser Mahmood Tongling Liang Wen‐Hua Sun 《Journal of polymer science. Part A, Polymer chemistry》2017,55(19):3214-3222
A new series of palladium complexes ( Pd1–Pd5 ) ligated by symmetrical 2,3‐diiminobutane derivatives, 2,3‐bis[2,6‐bis{bis(4‐FC6H4)2CH}2‐4‐(alkyl)C6H2N]C4H6 (alkyl = Me L1 , Et L2 , i Pr L3 , t Bu L4 ) and 2,3‐bis[2,6‐bis{bis(C6H5)2CH}2‐4‐{(CH3)3C}C6H2N]C4H6 L5 , have been prepared and well characterized, and their catalytic scope toward ethylene polymerization have been investigated. Upon activation with MAO, all palladium complexes ( Pd1–Pd5) exhibited good activities (up to 1.44 × 106 g (PE) mol?1(Pd) h?1) and produced higher molecular weight polyethylene in the range of 105 g mol?1 with precise molecular weight distribution (M w/M n = 1.37–1.77). One of the long‐standing limiting features of the Brookhart type α‐diimine Pd(II) catalysts is that they produce highly branched (ca. 100/1000 C atoms) and totally amorphous polymer. Conversely, herein Pd5 produced polymers having dramatically lower branching number (28/1000) as well as improved melting temperature up to 73.1 °C showing well‐controlled linear architecture, and very similar to polyethylene materials generated by early‐transition‐metal based catalysts. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3214–3222 相似文献
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Viktor O. Iaroshenko Sajid AliTariq Mahmood Babar Sergii DudkinSatenik Mkrtchyan Nasim Hasan RamaAlexander Villinger Peter Langer 《Tetrahedron letters》2011,52(3):373-376
4-Chloro-3-(trifluoroacetyl)coumarin was synthesized for the first time via direct TMSCl-mediated acylation of 4-hydroxycoumarin with TFAA followed by the treatment with POCl3. The reaction of 4-chloro-3-(trifluoroacetyl)coumarin with commercially available anilines is a two-step method, which affords a set of 7-(trifluoromethyl)-6H-chromeno[4,3-b]quinolin-6-ones in good to excellent yields. 相似文献
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Majid M. Heravi Fatemeh Derikvand Hossein A. Oskooie Rahim Hekmat Shoar Mahmood Tajbakhsh 《合成通讯》2013,43(3):513-517
An efficient and convenient method for the oxidation of thiols mediated by silica‐supported bis (trimethylsilyl) chromate (BTSC) in acetonitrile is reported. 相似文献
678.
Riccardo Costan Zovi Haroon Mahmood Andrea Dorigato Giulia Fredi Alessandro Pegoretti 《Molecules (Basel, Switzerland)》2020,25(22)
Thin cyclic olefin copolymer (COC) foils were used as intrinsic thermoplastic healing agents in carbon fiber (CF)-reinforced epoxy laminates. COC films were produced by hot pressing and were interleaved in the interlaminar regions between each EP/CF lamina, during the hand layup fabrication of the laminates. Three samples were produced, i.e., the neat EP/CF laminate without COC, and two laminates containing COC layers with a thickness of 44 μm and 77 μm, respectively. It was observed that the fiber volume fraction decreased, and the porosity increased with the introduction of COC layers, and this effect was more evident when thick films were used. These two effects, combined with the sub-optimal adhesion between COC and EP, caused a decrease in the mechanical properties (i.e., the elastic modulus, flexural strength, interlaminar shear strength and interlaminar fracture toughness) of the laminates. Specimens subjected to mode I interlaminar fracture toughness test were then thermally mended under pressure by resistive heating, through the Joule effect of conductive CFs. A temperature of approximately 190 °C was reached during the healing treatment. The healing efficiency was evaluated as the ratio of critical strain energy release rate (GIC) of the healed and virgin specimens. Healed specimens containing COC layers of 44 μm and 77 μm exhibited a healing efficiency of 164% and 100%, respectively. As expected, the healing treatment was not beneficial for the neat EP/CF laminate without COC, which experienced a healing efficiency of only 2%. This result proved the efficacy of COC layers as a healing agent for EP/CF laminates, and the effectiveness of resistive heating as a way to activate the intrinsic healing mechanism. 相似文献
679.
Marjan Mollazadeh Maryam Mohammadi-Khanaposhtani Homa Azizian Afsaneh Zonouzi Zahra Abdolahi Hamid Nadri Bagher Larijani Mahmood Biglar Mohammad Mahdavi 《中国化学会会志》2020,67(10):1910-1928
2,4-Dioxochroman-pyridinium-phenylacetamide derivatives 7a–n were synthesized and evaluated for their in vitro cholinesterase (ChE) inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Obtained results demonstrated that, among the synthesized compounds, two compounds, 7j and 7k , were more potent than the standard drug donepezil against BuChE and did not show cytotoxicity and carcinogenicity. Furthermore, through molecular modeling and molecular dynamic studies. we showed that these compounds can be located deep in the gorge cavity of BuChE and that they interacted with catalytic residues, acyl, and cholin-binding pockets of this enzyme. Support information 相似文献
680.
Muhammad Yaqub Javeria Batool Khalid Mahmood Abida Ashraf Ruqayia Perveen Zahid Shafiq 《Journal of heterocyclic chemistry》2020,57(8):3089-3104
A regioselective and convenient methodology was developed to synthesize heterocyclic derivatives, bearing imidazole, piperidines, and azepines rings. The N-arylnitrones derived from 3-formylchromones were selected to react with heterocyclic ketene aminal to furnish the structurally attractive and pharmacologically important fused ring heterocycles. The N-arylnitrone moiety of 3-formylchromone was used to activate the formyl group for regioselective fused ring heterocycles synthesis, whereas, the effect of substituents at aryl functionality of nitrones were studied to improve the yield of target fused ring heterocyclic products. The synthesized compounds (10-12) were evaluated for their in vitro cytotoxic and antifungal influences. In cytotoxic (brine shrimp lethality) assay, compound 11e was found to be active with LD50 = 4.1 × 10−6 μg/mL. 相似文献