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101.
l‐Proline‐functionalized Fe3O4 nanoparticles as a novel magnetic chiral catalyst for the direct asymmetric Mannich reaction 下载免费PDF全文
l ‐Proline has been successfully anchored on the surface of magnetic nanoparticles and characterized using powder X‐ray diffraction, scanning electron microscopy, vibrating sample magnetometry and Fourier transform infrared spectroscopy. These nanoparticles as a chiral catalyst have been employed to promote the direct asymmetric Mannich reaction. The corresponding products are obtained in high yields with high level of diastereoselectivity (up to 99:1 dr) in the presence of Fe3O4– l ‐proline. Also this heterogeneous catalyst can be recovered easily and reused many times without significant loss of its catalytic activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
102.
Seyyed Arash Azimi Siavash Ahmadi Zahra Ahmadian Javad Mohajeri Mohammad Reza Aref 《International Journal of Communication Systems》2018,31(1)
HIGHT is a lightweight block cipher introduced in CHES 2006 by Hong et al as a block cipher suitable for low‐resource applications. In this paper, we propose improved impossible differential and biclique attacks on HIGHT block cipher both exploiting the permutation‐based property of the cipher's key schedule algorithm as well as its low diffusion. For impossible differential attack, we found a new 17‐round impossible differential characteristic that enables us to propose a new 27‐round impossible differential attack. The total time complexity of the attack is 2120.4 where an amount of 259.3 chosen plaintext‐ciphertext pairs and 2107.4 memory are required. We also instantiate a new biclique cryptanalysis of HIGHT, which is based on the new idea of splitting each of the forward and backward keys into 2 parts where the computations associated to each one are performed independently. The time complexity and data complexity of this attack are 2125.7 and 242, respectively. To the best of our knowledge, this is the fastest biclique attack on full‐round HIGHT. 相似文献
103.
Microchimica Acta - Accurate detection of temperature and oxygen concentration at the cellular level is important in tumor diagnosis. Multifunctional nanocomposites are described that consist of... 相似文献
104.
Javad Safaei-Ghomi Nasrin Enayat-Mehri Fahime Eshteghal 《Journal of Saudi Chemical Society》2018,22(4):485-495
4-(4′-diamino-di-phenyl)-sulfone supported on hollow magnetic mesoporous (HMMS) Fe3O4@SiO2 NPs has been used as a novel and efficient catalyst in the preparation of ethyl 2-amino-5,10-dihydro-5,10-dioxo-4-phenyl-4H benzo[g]chromene-3-carboxylates by a simple one-pot three-component reaction of aldehydes, ethyl cyanoacetate and 2-hydroxynaphthalene-1,4-dione under reflux conditions in ethanol. Wide range of products, excellent yields in short times, reusability of the catalyst, low catalyst loading and environmental benignity are some of the important features of this protocol. 相似文献
105.
Telecommunication Systems - This paper analyzes the carrier-to-interference ratio (CIR) of the so-called shotgun cellular systems (SCSs) in $$\tau $$ dimensions ( $$\tau =1, 2,$$ and 3). SCSs are... 相似文献
106.
Asghari Abbas Azadi-Tinat Nima Oraizi Homayoon Ghalibafan Javad 《Wireless Personal Communications》2019,108(3):1529-1546
Wireless Personal Communications - One of the important objectives of underwater acoustic sensor network is to extend the lifespan of a network which depends on the topology control mechanisms.... 相似文献
107.
Motahhareh Estebsari Mohammad Gholami Mohammad Javad Ghahramanpour 《Analog Integrated Circuits and Signal Processing》2017,90(2):427-434
A voltage controlled delay cell with wide frequency range is presented in this paper. The delay-line which is resulted by connecting five series of delay cells generating a wide range of delay from 1.9 to 13.24 ns. It can be used in an analog delay locked loop. The linear characteristic of the circuit with respect to the conventional delay line structures is improved, and a better performance of noise is obtained using differential structure. This circuit is designed by ADS software and TSMC CMOS 0.18 μm technology, with supply voltage 1.8 V. By changing control voltage from 0.335 to 1.8 V in delay line, a wide range of frequency from 75.52 to 917.43 MHz will be covered. Simulation results show that the proposed delay line has power consumption of maximum 3.77 mW at frequency of 75.52 MHz. It also shows that increasing of frequency will reduce power dissipation which is the one of the main characteristics of this novel circuit. Moreover, the delay locked loop which uses these delay cells has a very high lock speed so that the maximum lock time in just five clock cycles. 相似文献
108.
Javad Azizian Ali A. Mohammadi Ilyar Bidar Peiman Mirzaei 《Monatshefte für Chemie / Chemical Monthly》2008,139(7):805-808
A simple, efficient, and practical procedure for the Pechmann condensation using KAl(SO4)2 · 12H2O (alum) as a non-toxic, reusable, inexpensive, and easily available catalyst is described under solvent-free condition at
65°C. These improved reaction conditions allow the preparation of a wide variety of some new substituted coumarins in high
yields (86–96%) and purity under mild reaction conditions. Compared to the classical Pechmann condensation, this new method consistently has the advantage of high yields.
Correspondence: Ali A. Mohammadi, Department of Chemistry, Shahid Beheshti University, P.O. Box 19839-4716, Tehran, Iran. 相似文献
109.
A facile one-pot three-component condensation of terephthalic aldehyde with urea and fluorinated 1,3-dicarbonyl derivatives is developed using catalytic quantities of chlorotrimethylsilane at ambient temperature. As a consequence, efficient synthesis of novel trifluoromethyl derivatives of bis(tetrahydropyrimidinone)benzenes is observed within short time periods. The procedure is shown to be equally efficient when urea is replaced with thiourea or guanidine. 相似文献
110.
Seyyed Javad Sabounchei Hassan Nemattalab Sadegh Salehzadeh Sima Khani Mehdi Bayat Hamid Reza Khavasi 《Polyhedron》2008
Reaction of phosphorus ylide Ph3PCHC(O)C6H4Cl (Y1) with HgX2 (X = Cl, Br and I) and ylide (p-tolyl)3PCHC(O)CH3 (Y2) with HgI2 in equimolar ratios using methanol as solvent leads to binuclear products. The bridge-splitting reaction of binuclear complex [(Y1) · HgCl2]2 by DMSO yields a mononuclear complex containing DMSO as ligand. O-coordination of DMSO is revealed by single crystal X-ray analysis in mononuclear complex of [(Y1) · HgCl2 · DMSO]. C-coordination of ylides is confirmed by X-ray structure of binuclear complex [(Y2) · HgI2]2. Characterization of the obtained compounds was also performed by elemental analysis, IR, 1H, 31P, and 13C NMR. Theoretical studies on mercury(II) complexes of Y1 show that formation of mononuclear complexes in DMSO solution in which DMSO acts as a ligand, energetically is more favorable than that of binuclear complexes. 相似文献