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21.
A highly enantioselective synthesis of lythraceae alkaloid lasubine II has been achieved using organo-catalyzed Mannich reaction, Maruoka allylation, and aza-Michael addition as the key steps. 相似文献
22.
F. Khani M. Ahmadzadeh Raji S. Hamedi-Nezhad 《Communications in Nonlinear Science & Numerical Simulation》2009,14(7):3007-3017
In this work, we apply the homotopy analysis method to solve fin problems with temperature-dependent thermal conductivity. The results are compared with the solutions obtained by the Adomian decomposition method (ADM), homotopy perturbation method (HPM) and with the Taylor series expansion method as well. The results of the comparisons have shown that the ADM and HPM are just an approximation of the present study and the accuracy of the solution obtained by the present study is much better than the latter algorithms. 相似文献
23.
One-pot synthesis of substituted pyrroles by a cascade reaction of azides with Morita-Baylis-Hillman acetates of acetylenic aldehydes is described and the reaction is efficiently mediated by triphenyl phosphine at room temperature. Sodium azide is successfully used to provide N-unsubstituted pyrroles, while alkyl azides afforded the corresponding N-alkylated pyrroles through a sequence of allylic substitution/azide reduction/cycloisomerization reactions. The obtained products have provided a new entry to indolizino indoles, pyrrolo isoquinolines and 8-oxo-5,6,7,8-tetrahydroindolizine. 相似文献
24.
25.
AbstractA convergent synthesis of the southern furan segment of novel furanocembranoids from Croton oblongifolius has been accomplished involving silver-catalyzed cyclization of alkynyl diol as the key step towards 2, 5-disubstituted furan ring formation. 相似文献
26.
F. Khani A. Farmany M. Ahmadzadeh Raji Abdul Aziz F. Samadi 《Communications in Nonlinear Science & Numerical Simulation》2009,14(11):3867-3878
An analytic approximate solution is presented for the natural convective dissipative heat transfer of an incompressible, third grade, non-Newtonian fluid flowing past an infinite porous plate embedded in a Darcy–Forchheimer porous medium. The mathematical model is developed in an coordinate system. Using a set of transformations, the momentum equation is rendered one-dimensional and a partly linearized heat conservation equation is derived. The viscoelastic formulation presented by Akyildiz [Akyildiz FT. A note on the flow of a third grade between heated parallel plates. Int J Non-Linear Mech 2001;36:349–52] is adopted, which generates lateral mass and viscoelastic terms in the heat conservation equation, as well as in the momentum equation. A number of special cases of the general transformed model are discussed. A homotopy analysis method (HAM) is implemented to solve, with appropriate boundary conditions, the coupled third-order, second degree ordinary differential equation for momentum and the second-order, fourth degree heat conservation equation. 相似文献
27.
S. A. Martin Britto Dhas M. Suresh P. Raji K. Ramachandran S. Natarajan 《Crystal Research and Technology》2007,42(2):190-194
Photoacoustic spectroscopy (PAS) is a non‐destructive testing (NDT) tool and used here for analyzing the physical properties such as thermal diffusivity, thermal diffusion length, thermal conductivity and thermal effusivity of L‐Threonine and L‐Prolinium tartrate. These two crystals belong to a group of recently developed NLO materials, in our laboratory. The single crystals of the two compounds were grown by using submerged seed solution growth method. Characterization of the crystals was made by using single crystal X‐ray diffraction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
28.
Thao T. P. Nguyen Dr. Foad Raji Dr. Cuong V. Nguyen Dr. Ngoc N. Nguyen Prof. Anh V. Nguyen 《Chemphyschem》2023,24(23):e202300062
Surfactants are used to control the macroscopic properties of the air-water interface. However, the link between the surfactant molecular structure and the macroscopic properties remains unclear. Using sum-frequency generation spectroscopy and molecular dynamics simulations, two ionic surfactants (dodecyl trimethylammonium bromide, DTAB, and sodium dodecyl sulphate, SDS) with the same carbon chain lengths and charge magnitude (but different signs) of head groups interact and reorient interfacial water molecules differently. DTAB forms a thicker but sparser interfacial layer than SDS. It is due to the deep penetration into the adsorption zone of Br− counterions compared to smaller Na+ ones, and also due to the flip-flop orientation of water molecules. SDS alters two distinctive interfacial water layers into a layer where H+ points to the air, forming strong hydrogen bonding with the sulphate headgroup. In contrast, only weaker dipole-dipole interactions with the DTAB headgroup are formed as they reorient water molecules with H+ point down to the aqueous phase. Hence, with more molecules adsorbed at the interface, SDS builds up a higher interfacial pressure than DTAB, producing lower surface tension and higher foam stability at a similar bulk concentration. Our findings offer improved knowledge for understanding various processes in the industry and nature. 相似文献
29.
Cycloalkanone hydrazones undergo condensation with mercaptoacetic acid to give predominantly the spirothiazolidinones. The structures of the products have been established on the basis of physico-chemical data. These compounds have shown promising antibacterial and antifungal activity. 相似文献
30.
Zora Popović Gordana Pavlović Željka Soldin Jasminka Popović Dubravka Matković-Čalogović Maša Rajić 《Structural chemistry》2002,13(5-6):415-424
The series of compounds of the general formulae HgX2(tzdtH) and HgX2(tzdtH)2 (X = Cl, Br, I; tzdtH = 1,3-thiazolidine-2-thione) have been prepared, as well as Hg(tzdt)2. IR, 1H, and 13C NMR spectral data of the complexes indicate thione donation, which is confirmed by the crystal structure analyses of [HgBr2(tzdtH)]2, [HgI2(tzdtH)]2, and HgI2(tzdtH)2. The structures of [HgBr2(tzdtH)]2 and [HgI2(tzdtH)]2 consist of centrosymmetric doubly bridged dimers, but they are not isostructural. The asymmetry in the HgX2Hg bridge is more pronounced in the bromo than in the iodo derivative [S–Hg–X(terminal) is 138.19(9)° for X = Br and 123.49(10)° for X = I], which is accompanied by the stronger Hg–S covalent bond in the bromo than in the iodo complex [2.435(4) vs. 2.510(3) Å]. The Hg–X(bridging) (X = Br, I) bond distances are shorter than the sum of van der Waals radii for mercury and X. Dimeric centrosymmetric complex units are held together only by van der Waals forces in [HgI2(tzdtH)]2, while in [HgBr2(tzdtH)]2 there is an intramolecular hydrogen bond of N–H Br type (3.34(1) Å). HgI2(tzdtH)2 exists as a mononuclear tetrahedral complex with two long Hg–S [2.672(1) Å] and two short Hg–I bond distances [2.688(1) Å] related by a twofold axis. The molecules of HgI2(tzdtH)2 are linked into infinite chains along the c axis by intermolecular N–H S [3.38(1) Å] hydrogen bonds. 相似文献