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Ali Khalafi-Nezhad Farhad Panahi Somayeh Mohammadi Habib Ollah Foroughi 《Journal of the Iranian Chemical Society》2013,10(2):189-200
Silica boron–sulfuric acid nanoparticles (SBSANs) as a solid Lewis-protic acid have been found to be an efficient heterogeneous catalyst in the synthesis of xanthene and acridine derivatives. The SBSAN-catalyzed reaction between carbonyl compound (aldehyde/ketone/ethyl orthoformate) and 5,5-dimethyl-1,3-cyclohexanedione (dimedone) for synthesis of xanthene derivatives is performed under mild conditions with the excellent isolated yield. Also, we can apply a broad scope of carbonyl compounds and amines for efficient synthesis of various acridine derivatives in the presence of SBSAN catalyst. In these multicomponent approaches the SBSAN catalyst can be reused for several times without any treatment in its catalytic activity. 相似文献
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Dadkhoda Ghazanfari Mohammed M. Hashemi Mohammad Reza Akhgar Mohammad Mehdi Foroughi Fariba Najafi-Zadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3018-3022
The ring-opening reaction of epoxides with thiols by SbCl 3 supported on Kieselguhr under solvent-free conditions, afforded high yields of β-hydroxy sulfides. Nucleophilic attack of the thiols occurs regioselectively at the less hindered side of the epoxides. 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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P. Knowles J. Deutsch J. Egger W. Fetscher F. Foroughi J. Govaerts M. Hadri K. Kirch S. Kistryn J. Lang X. Morelle O. Naviliat A. Ninane R. Prieels N. Severijns L. Simons J. Sromicki S. Vandormael P. Van Hove 《Hyperfine Interactions》1999,118(1-4):73-76
Unlike the majority of Michel parameters which are consistent with the Standard Model V-A interaction, the experimental value of ξ″(=0.65±0.36) [1] is poorly known. Our experiment will measure the longitudinal polarization,
P
L
, of positrons emitted from the decay of polarized muons. The value of P
L
, equal to unity in the Standard Model, will decrease for high energy positrons emitted antiparallel to the muon spin if the
combination of Michel parameters ξ″/ξξ′ − 1 deviates from the Standard Model value of zero.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献