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101.
Dr. Abhishek Sharma Dipak Vacchani Prof. Dr. Erik Van der Eycken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1158-1168
This minireview describes the progress made in the development of direct C? H arylation approaches through the application of focused microwave irradiation. The synergistic combination of microwave‐assisted techniques with the rapidly evolving domain of C? H arylation has opened new vistas in the efficient synthesis of a diverse array of biologically important (hetero)arenes. 相似文献
102.
A new zwitterionic salt, sulfated choline based heteropolyanion, which was reported earlier by our group, has been found to be very effective for the synthesis of spirooxindole derivatives at room temperature. The heteropolyanion based on sulfated ionic liquid (HIL) showed promising features for the reaction, such as shorter reaction time, high product yields (about 90–95%), simple work up, easy removal, and reusability of the catalyst for several times without significant loss in its efficiency. This has made the protocol sustainable and economic. 相似文献
103.
A microwave-assisted, one-pot pseudo five-component reaction strategy has been developed for the synthesis of some novel spiroindenotetrahydropyridine derivatives from 1,3-indanedione, an aromatic aldehyde, and ammonium acetate under catalyst- and solvent-free conditions via tandem Knoevenagel/aza-Diels–Alder reaction. 相似文献
104.
Abstract
Iodine catalyzes the pseudo four-component reaction of an aldehyde, a urea or thiourea, and cyclic 1,3-dicarbonyl compounds under microwave irradiation in a solvent-free condition to yield various σ symmetric spiro heterobicyclic rings in excellent yields. 相似文献105.
Dipak Kumar Roy Sundargopal Ghosh Jean-François Halet 《Journal of Cluster Science》2014,25(1):225-237
The recent achievements and progress in the field of high-nuclearity supraicosahedral metallaborane chemistry are reviewed and compared to those made in borane, carborane and metallacarborane chemistry. In contrast to metallacarboranes, characterized large supraicosahedral metallaboranes only adopt isocloso deltahedral structural arrangements with n vertices and a non-Wadean n skeletal-electron-pair count. This anomaly can be rationalized by the preference of metal atoms for 6-connect vertices present in the cluster cages. 相似文献
106.
Component Selection in the Self‐Assembly of Palladium(II) Nanocages and Cage‐to‐Cage Transformations
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Dipak Samanta Prof. Dr. Partha Sarathi Mukherjee 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12483-12492
Dynamic supramolecular systems involving a tetratopic palladium(II) acceptor and three different pyridine‐ and imidazole‐based donors have been used for self‐selection by a synergistic effect of morphological information and coordination ability of ligands through specific coordination interactions. Three different cages were first synthesized by two‐component self‐assembly of individual donor and acceptor. When all four components were allowed to interact in a reaction mixture, only one out of three cages was isolated. The preferential binding affinity towards a particular partner was also established by transforming a non‐preferred cage into a preferred cage by interaction with the appropriate ligand. Computational studies further supported the fact that coordination interaction of imidazole moiety to PdII is enthalpically more preferred compared to pyridine, which drives the selection process. Analysis of crystal packing of both complexes indicated the presence of strong hydrogen bonds between nitrate and water molecules and also H‐bonded 3D networks of water. Both complexes exhibit promising proton conductivity (10?5 to ca. 10?3 S cm?1) at ambient temperature under a relative humidity of circa 98 % with low activation energy. 相似文献
107.
Strong Self-Similar Fluctuations of Target Fragments in Ring-like Events in Ultra-Relativistic Nuclear Collision
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Dipak Ghosh Argha Deb Samabrata Sarkar Prabir Kumar Haldar 《中国物理快报》2006,23(11):2944-2947
The intermittent fluctuation of target evaporated particles is studied in both ring-like and jet-like events emitted in ^32 S-emulsion interactions at 200 A Ge V within the framework of multi-dimensional factorial moment methodology using the concept of the Hurst exponent. It is observed that the intermittent fluctuation in the ring-like event is self-similar, whereas in the jet-like event fluctuation is self-affine. However, study indicates that the strength of fluctuation in the ring-like events is much stronger than that in the jet-like events. 相似文献
108.
The cis‐[Rh(CO)2ClL] (1) complexes, where L = 2‐methylpyridine (a), 3‐methylpyridine (b), 4‐methylpyridine (c), 2‐phenylpyridine (d), 3‐phenylpyridine (e), 4‐phenylpyridine (f), undergo oxidative addition reactions with various electrophiles, like CH3I, C2H5I, C6H5CH2Cl or I2, to yield complexes of the types [Rh(CO)(COR)ClXL] (2) (where R = CH3 (i), C2H5 (ii), X = I; R = C6H5CH2 (iii), X = Cl) or [Rh(CO)ClI2L] (3) and [Rh(CO)2ClI2L] (4). The pseudo‐first‐order rate constants of CH3I addition with complexes 1 containing pyridine (g) and 2‐substituted pyridine (a and d) ligands were found to follow the order pyridine >2‐methylpyridine >2‐phenylpyridine. The catalytic activity of complexes 1 containing different pyridine ligands (a–g) on carbonylation of methanol was studied and, in general, a higher turnover number was obtained compared with that of the well‐known species [Rh(CO)2I2]?. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
109.
María Elena Leyva Guilherme M. O. Barra Ana C. F. Moreira Bluma G. Soares Dipak Khastgir 《Journal of Polymer Science.Polymer Physics》2003,41(23):2983-2997
The conductivity of styrene‐butadiene‐styrene block copolymers containing different amounts of extraconductive carbon black (CB) was investigated as a function of the mold temperature. The composites exhibited reduced percolation thresholds (between 1.0 and 2.0 vol % CB). The dynamic mechanical analysis characterization revealed that the glass‐rubber‐transition temperatures of both segments were not affected by the CB addition, although the damping of the polybutadiene phase displayed a progressive drop with an increase in the CB concentration. The normalized curves of tan δ/tan δmax (where tan δ represents the value of the loss tangent at any measurement temperature and tan δmax represents the loss tangent peak value at the corresponding temperature Tmax) versus T/Tmax (where T is the temperature and Tmax is the maximum temperature), corresponding to both polystyrene and polybutadiene phases as well as the activation energy related to the glass‐rubber‐transition process, did not present any significant change with the addition of CB. The dielectric analysis revealed the presence of two relaxation peaks in the composite containing 1.5 vol % CB, the magnitude of which was strongly influenced by the frequency, being attributed to interfacial Maxwell‐Wagner‐Sillars relaxations caused by the presence of different interfaces in the composite. The mechanical properties were not affected by the presence of CB at concentrations of up to 2.5 vol %. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2983–2997, 2003 相似文献
110.
This paper considers a new approach to develop a very general class of skew multivariate distributions. The approach is based on a linear combination of an elliptically distributed random variable with a linear constraint. Using this approach two different classes of multivariate distributions are constructed based on original distribution. These new classes include different types of skew normal (type A and type B) and other skew elliptical distributions, exist in the literature. We also derive the moment generating function, marginal and conditional density of our proposed classes of distributions. Straightforward explanations are applied to demonstrate the relationships among previous approaches by others with our proposed class of skew distributions. 相似文献