排序方式: 共有65条查询结果,搜索用时 15 毫秒
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Niloufar Afzali Reihaneh Kardanpour Farnaz Zadehahmadi Shahram Tangestaninejad Majid Moghadam Valiollah Mirkhani Adam Mechler Iraj Mohammadpoor‐Baltork Mehrnaz Bahadori 《应用有机金属化学》2019,33(11)
A novel heterogeneous nanocatalyst was established by supporting molybdenum (VI) on Zr6 nodes in the structure of the well‐known UiO‐66 metal–organic framework (MOF). The structure of the UiO‐66 before and after Mo (VI) immobilization was confirmed with XRD, DR‐FTIR and UV–vis spectroscopy, and the presence and amount of Mo (VI) was identified by X‐ray photoelectron spectroscopy and inductively coupled plasma atomic emission spectroscopy. TEM imaging confirmed the absence of Mo clusters on the MOF surface, while SEM confirmed that the appearance of the MOF has not changed upon immobilizing the Mo (VI) catalyst. BET adsorption measurements were used to confirm the porosity of the catalyst. The catalytic activity of this heterogeneous catalyst was investigated in oxidation of sulfides with H2O2 in acetonitrile and oxidative desulfurization of dibenzothiophene. Easy work up, convenient and steady reuse and high activity and selectivity are prominent properties of this new hybrid material. 相似文献
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A reduced surface electric field in AlGaN/GaN high electron mobility transistor (HEMT) is investigated by employing a localized Mg-doped layer under the two-dimensional electron gas (2-DEG) channel as an electric field shaping layer. The electric field strength around the gate edge is effectively relieved and the surface electric field is distributed evenly as compared with those of HEMTs with conventional source-connected field plate and double field plate structures with the same device physical dimensions. Compared with the HEMTs with conventional source-connected field plate and double field plate, the HEMT with Mg-doped layer also shows that the breakdown location shifts from the surface of the gate edge to the bulk Mg-doped layer edge. By optimizing both the length of Mg-doped layer, Lm, and the doping concentration, a 5.5 times and 3 times the reduction in the peak electric field near the drain side gate edge is observed as compared with those of the HEMTs with source-connected field plate structure and double field plate structure, respectively. In a device with VGS=-5 V, Lm=1.5 μm, a peak Mg doping concentration of 8× 1017 cm-3 and a drift region length of 10 μm, the breakdown voltage is observed to increase from 560 V in a conventional device without field plate structure to over 900 V without any area overhead penalty. 相似文献
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Hunter HN Hadei N Blagojevic V Patschinski P Achonduh GT Avola S Bohme DK Organ MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(28):7845-7851
Negishi cross-coupling reactions were analyzed in solution by mass spectrometry and NMR spectroscopy to identify both the effect of LiBr as an additive as well as the purpose of 3-dimethyl-2-imidazolidinone (DMI) as a co-solvent. The results suggest that the main role of DMI is to facilitate a higher order bromozincate formation during the addition of LiBr. 相似文献
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Organ MG Abdel-Hadi M Avola S Dubovyk I Hadei N Kantchev EA O'Brien CJ Sayah M Valente C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(8):2443-2452
Pd-N-heterocyclic carbene (NHC)-catalyzed Buchwald-Hartwig amination protocols mediated by Pd-PEPPSI precatalysts is described. These protocols provide access to a range of hindered and functionalized drug-like aryl amines in high yield with both electron-deficient and electron-rich aryl- and heteroaryl chlorides and bromides. Variations in solvent polarity, base and temperature are tolerated, enhancing the scope and utility of this protocol. A mechanistic rationalization for base strength (pKb) requirements is also provided. 相似文献
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Rosseto R Bibak N DeOcampo R Shah T Gabrielian A Hajdu J 《The Journal of organic chemistry》2007,72(5):1691-1698
A new stereoselective synthesis of lysophosphatidylcholines is reported. The synthesis is based upon (1) the use of 3-p-toluenesulfonyl-sn-glycerol to provide the stereocenter for construction of the optically active lysophospholipid molecule, (2) tetrahydropyranylation of the secondary alcohol function to achieve orthogonal protection of the sn-2- and sn-3-glycerol positions, and (3) elaboration of the phosphodiester headgroup using a 2-chloro-1,3,2-dioxaphospholane/trimethylamine sequence. In the course of developing the synthesis it has been discovered that methoxyacetate displacement of the sn-3-p-toluenesulfonate yields a reactive methoxyacetyl ester, which in turn can be selectively cleaved with methanol/tert-butylamine, while the ester group at the sn-1-position remains unaffected. The sequence has been shown to be suitable for preparation of spectroscopically labeled lysophosphatidylcholines. One of these compounds was readily converted to a double-labeled mixed-chain phosphatidylcholine applicable for real-time fluorescence resonance energy transfer (FRET) assay of lipolytic enzymes. In addition, the work led to new synthetic strategies based on chemoselective manipulation of the tosyl group in the presence of other base-labile groups such as FMOC derivatives that are often used for the protection of amino and hydroxyl groups in syntheses. 相似文献
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Organ MG Avola S Dubovyk I Hadei N Kantchev EA O'Brien CJ Valente C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(18):4749-4755
We have developed the first user-friendly Negishi protocol capable of routinely cross-coupling all combinations of alkyl and aryl centers. The use of an easily synthesized, air stable, highly active, well-defined precatalyst PEPPSI-IPr (1; PEPPSI=pyridine-enhanced precatalyst preparation, stabilization and initiation; IPr=diisopropylphenylimidazolium derivative) substantially increases the scope, reliability, and ease-of-use of the Negishi reaction. All organohalides and routinely used pseudohalides were excellent coupling partners, with the use of chlorides, bromides, iodides, triflates, tosylates, and mesylates resulting in high yield of the coupled product. Furthermore, all reactions were performed by using general laboratory techniques, with no glove-box necessary as the precatalyst was weighed and stored in air. Utilization of this methodology allowed for the easy synthesis of an assortment of sterically encumbered biaryls and druglike heteroaromatics, demonstrating the value of the PEPPSI-IPr system. Furthermore, this is also the first time Pd-NHC (NHC=N-heterocyclic carbene) methodology has surpassed the related phosphine-ligated Negishi processes both in activity and use. 相似文献
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O'Brien CJ Kantchev EA Valente C Hadei N Chass GA Lough A Hopkinson AC Organ MG 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(18):4743-4748
The synthesis of NHC-PdCl(2)-3-chloropyridine (NHC=N-heterocyclic carbene) complexes from readily available starting materials in air is described. The 2,6-diisopropylphenyl derivative was found to be highly catalytically active in alkyl-alkyl Suzuki and Negishi cross-coupling reactions. The synthesis, ease-of-use, and activity of this complex are substantial improvements over in situ catalyst generation and all current Pd-NHC complexes. The utilization of complex 4 led to the development of a reliable, easily employed Suzuki-Miyama protocol. Employing various reaction conditions allowed a large array of hindered biaryl and drug-like heteroaromatic compounds to be synthesized without difficulty. 相似文献
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Synthesis and Cytotoxic Evaluation of Novel 1,2,3‐Triazole‐4‐Linked (2E,6E)‐2‐Benzylidene‐6‐(4‐nitrobenzylidene)cyclohexanones
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Mohammad Mahdavi Maryam Akhbari Mina Saeedi Maryam Karimi Niloufar Foroughi Elahe Karimpour‐Razkenari Heshmatollah Alinezhad Alireza Foroumadi Abbas Shafiee Tahmineh Akbarzadeh 《Helvetica chimica acta》2016,99(3):175-180
This work describes the synthesis of novel 1,2,3‐triazole‐4‐linked (2E,6E)‐2‐benzylidene‐6‐(4‐nitrobenzylidene)cyclo‐hexanones starting from cyclohexanone. 1‐(Cyclohex‐1‐en‐1‐yl)piperidine, the enamine from cyclohexanone and piperidine, reacted with 4‐nitrobenzaldehyde to obtain 2‐(4‐nitrobenzylidene)cyclohexanone. Condensation of the latter compound with (prop‐2‐yn‐1‐yloxy)benzaldehyde derivatives under acidic conditions gave (4‐nitrobenzylidene)‐[(prop‐2‐yn‐1‐yloxy)‐benzylidene]cyclohexanones. Finally, ‘click reaction’ of these derivatives and various organic azides led to the title compounds. All compounds were examined by MTT assay for cytotoxic activity in one human breast cancer cell line, MDA‐MB‐231. 相似文献