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51.
Sujit Mondal 《Tetrahedron letters》2010,51(33):4452-4913
A novel Cu(I)-catalyzed photochemical reaction of diethyl ether with vicinal diols and their ketals is reported. The most remarkable feature is the transformation of 1,2-diols and their ketals to acetals of acetaldehyde under totally neutral condition without using acetaldehyde. 相似文献
52.
Pei-Hsun Wei Mukulesh Mondal Gero D. Harzmann Kraig A. Wheeler 《Tetrahedron letters》2010,51(51):6690-6694
The mechanism of PBu3-catalyzed homodimerization of ketoketenes has been explored and compared with that of the previously reported trialkylphosphite-mediated reactions. NMR studies of the PBu3-catalyzed reaction implicated the involvement of tetravalent phosphonium intermediates. Phosphonium intermediates in the catalytic cycle were trapped through reaction with trimethylsilyl chloride and 4-chlorobenzaldehyde, and the resulting products were characterized. A method for the stoichiometric generation of phosphonium enolates was developed as a result of these studies. No evidence was obtained for the involvement of pentacovalent phosphorane intermediates in trialkylphosphine-catalyzed ketoketene homodimerization reactions, in contrast with the mechanism of the trialkylphosphite-mediated homodimerization of dimethylketene. An X-ray crystal structure analysis of methylphenylketene dimer showed that it possesses Z-geometry about the exocyclic olefin. 相似文献
53.
Mrinal Kanti Paira Tapan Kumar Mondal Elena López-Torres Joan Ribas Chittaranjan Sinha 《Polyhedron》2010
Copper(II) complexes of 3-((2-(alkylthio)phenylazo)-2,4-pentanedione, tridentate O, N, S donor ligands, are described in this work. Chloride bridged copper(II) polymers (1) and thiocyanato bridged copper(II) dimmers (2) are characterized by a single crystal X-ray diffraction study. The complexes show antiferromagnetic interactions, with J = −0.5 ± 0.1 cm−1 (1a) and −25.8 ± 0.5 cm−1 (2b), which implies stronger coupling in the –SCN-bridging compound. The spectra, redox and magnetism are explained by DFT studies. 相似文献
54.
Structure, stability, and dissociation of H2BSiN, H2NSiN, H2PSiN and their isomers H2BNSi, H2NNSi, H2PNSi have been studied in detail using ab initio MP2 and CCSD(T) methods. After dissociation of H2BNSi, H2NNSi, H2PNSi and their isomers, the fragmented atoms have been considered to be either in their ground state or in their valence excited state in various dissociation channels. Only allowed dissociations of these molecules are considered. Various dissociation channels of H2BNSi, H2NNSi, H2PNSi and their isomers have been explored and interesting trends are observed for the dissociation of stable isomers H2BNSi, H2NNSi, H2PNSi and less stable isomers H2BSiN, H2NSiN, H2PSiN. The effect of substituents on their structural properties has been discussed. The potential energy surfaces for the RSiN ? RNSi isomerization reactions have been analyzed. The structural properties of these molecules agree well with the theoretical values wherever available. 相似文献
55.
Swarup Kumar Maji Anup Mondal Bibhutosh Adhikary Basudeb Karmakar 《Journal of Physics and Chemistry of Solids》2011,72(6):784-788
We report the formation of mesoporous zinc sulphide, composed by the fine network of nanoparticles, which was formed via a single precursor Zn(SOCCH3)2Lut2 complex. The complex was chemically synthesized using zinc carbonate basic, 3,5-lutidine and thioacetic acid, in air. The metal precursor complex was characterized using different conventional techniques. Thermogravimetric analysis (TGA) result indicates that the decomposition of the complex starts at 100 °C and continues up to 450 °C, finally yielding ZnS. ZnS nanocrystals were characterized by powder X-ray diffraction (XRD) technique, field emission scanning electron microscopy (FESEM), N2-sorption isotherm, UV-vis spectroscopy and photoluminescence (PL) spectroscopy. The grain diameter of nanocrystals was found to be 4-5 nm. The material followed Type-IV N2-sorption isotherm, which is the characteristic of mesoporous materials. The band gap energy, as obtained from optical measurements was around 3.8 eV. 相似文献
56.
In this paper, we consider some transportation problems (TPs) with different types of fuzzy-stochastic unit transportation costs and budget constraints. These fuzzy stochastic costs are reduced to corresponding crisp ones in two different ways. For the first method, using the definition of α-cut of the fuzzy numbers, expectation is taken separately on both lower and upper α-cuts and then mean expectation is calculated with the help of signed distance. In the second procedure, we realize fuzzy random events (ξ?r) and (ξ?r) for the fuzzy random variable (ξ). Using credibility measure of these events, mean chances for the above fuzzy random events are calculated and then expectation is taken to get the crisp expressions. The reduced deterministic problems of the fuzzy stochastic TP are solved using a real coded genetic algorithm with Roulette wheel selection, arithmetic crossover and random mutation. Few numerical examples are demonstrated to find the optimal solutions of the proposed models. 相似文献
57.
58.
S. M. Islam Sanchita Mondal Anupam Singha Roy Paramita Mondal Manir Mobarak Dildar Hossain Palash Pandit 《Transition Metal Chemistry》2010,35(3):305-313
A polymer-anchored Pd(II) Schiff base complex has been synthesized by reacting a polymeric amine with 2-pyridinecarboxaldehyde
to get the polymer-anchored Schiff base, which was then reacted with palladium acetate. The catalyst was characterized by
physicochemical and spectroscopic methods. It shows excellent catalytic activity in the Sonogashira coupling of phenylacetylene
with aryl halides using triethylamine as a base and copper iodide as a co-catalyst in water under open air at 70 °C. We have
also studied the effects of base and solvent on the coupling reaction. Sonogashira reactions of phenylacetylene with a variety
of functionalized aryl halides were performed under the optimized reaction conditions. This catalyst gives excellent yields
without the use of phosphine ligands. Further experiments showed that the catalyst can be used five times without much loss
in the catalytic activity. 相似文献
59.
An SIR epidemic model with time delay, information variable and saturated incidence rate, where the susceptibles are assumed to satisfy the logistic equation and the incidence term, is of saturated form with the susceptibles. This model exhibits two bifurcations, one is transcritical bifurcation and the other is Hopf bifurcation. The local and global stability of endemic equilibrium is also discussed. Finally, numerical simulations are carried out to explain the mathematical conclusions. 相似文献
60.
In this article, the similarity relations are studied, together with invertibility conditions and eigenvalues of intuitionistic fuzzy matrices (IFMs). Besides, idempotent, regularity, permutation matrix and spectral radius of IFMs are considered here with some properties and results for IFMs investigated. 相似文献