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121.
The reactions of SiF2/SiF4 with amines, phosphines and various halomethanes were studied. The results show that in the presence of strong Lewis base (Et3N, HNEt2, PR3, PR2Cl), SiF2 inserts initially into SiF4 to form Si2F6, which was followed by subsequent reactions leading to products containing SiF3 groups. This is the first report of the insertion of SiF2 into SiF4. When the reactants were a weaker base (such as RPCl2, CX3Br, X=F, Cl), insertion of SiF2 into P-Cl and C-Br bonds became predominant. 相似文献
122.
The self-assembly of amphiphilic block copolymers in a gas-liquid microfluidic reactor produces variable, flow-directed micellar morphologies entirely different from off-chip equilibrium structures. A polystyrene-block-poly(acrylic acid) copolymer, which forms exclusively spheres off-chip, generates kinetic cylinders, Y-junctions, bilayers, and networks by a mechanism of collision-coalescence enabled by strong and localized on-chip shear fields. Variation in the size and relative amount of flow-directed nanostructures is achieved by changing the water content and flow rate. These results demonstrate on-chip processing routes to specific functional colloidal nanostructures. 相似文献
123.
Cheng-Yu Lee Yun-Chung Chen Hao-Chun Lin Yuandong Jhong Chih-Wei Chang Ching-Hua Tsai Chai-Lin Kao Tun-Cheng Chien 《Tetrahedron》2012,68(29):5898-5907
A facile and effective synthesis for a wide variety of 4-arylidene-5-imidazolinone derivatives was developed. 4-Arylidene-5-oxazolinones were prepared by Erlenmeyer azlactone synthesis from N-acylglycines and arylaldehydes. The ring-opening reactions of the 4-arylidene-5-oxazolinones with primary amines afforded 2-acylamino-3-arylacrylamides in excellent yields. A new dehydrative cyclization of the 2-acylamino-3-arylacrylamides in pyridine under reflux furnished the corresponding 4-arylidene-5-imidazolinones in good yields. 相似文献
124.
C. Damodaran E. R. B. Shanmugasundaram 《Journal of Radioanalytical and Nuclear Chemistry》1978,46(2):373-377
A brief report on the food pollutant-mycotoxin, citrinin, is presented. Radioactive14C-citrinin was isolated from Aspergillus candidus grown culture supplemented with14C-glucose. Quick uptake of14C-citrinin was observed in the liver and kidney of mice, after the administration of a single dose. In vitro studies with14C-citrinin reveal that it gets bound to the albumin fraction of human serum.
Part of Ph. D. Thesis submitted to the University of Madras in 1973. 相似文献
125.
An analytical method has been proposed to optimise the small-signaloptical gain of CO2-N2 gasdynamic lasers (gdl) employing two-dimensional (2D) wedge nozzles. Following our earlier work the equations governing the steady, inviscid, quasi-one-dimensional
flow in the wedge nozzle of thegdl are reduced to a universal form so that their solutions depend on a single unifying parameter. These equations are solved
numerically to obtain similar solutions for the various flow quantities, which variables are subsequently used to optimize
the small-signal-gain. The corresponding optimum values like reservoir pressure and temperature and 2D nozzle area ratio also
have been predicted and graphed for a wide range of laser gas compositions, with either H2O or He as the catalyst. A large number of graphs are presented which may be used to obtain the optimum values of small signal
gain for a wide range of laser compositions without further computations. 相似文献
126.
The structure of the alkaloid thalicmine has been proved to be 1,2-methylenedioxy-3,9,10-trimethoxyaporphine by a synthesis of the racemic form of the alkaloid on classical lines. 相似文献
127.
Relaxation dynamics and structural characterization of organic nanoparticles with enhanced emission 总被引:3,自引:0,他引:3
Bhongale CJ Chang CW Lee CS Diau EW Hsu CS 《The journal of physical chemistry. B》2005,109(28):13472-13482
With a reprecipitation method, we prepared fluorescent organic nanoparticles of 1,4-di[(E)-2-phenyl-1-propenyl]benzene (PPB) that feature weak emission in solution but exhibit blue-shifted absorption and strong emission as aggregates. Picosecond fluorescent transients of these PPB nanoparticles showed biexponential decay, described with a consecutive kinetic model involving two emissive states. X-ray diffraction patterns of PPB nanocrystals indicate long-range packing structures of two types, one the same as in a single crystal and the other not yet determined. PPB molecules in a crystal show an arrangement of a herringbone type with three benzene rings in a PPB unit being nearly planar and two methyl groups of the unit pointing along the same direction, in contrast to the twisted structure of an isolated PPB molecule. Fluorescence transients of PPB on a femtosecond scale indicate an efficient channel for isomerization that is activated for free PPB in solution but inhibited in PPB forming nanoparticles, demonstrating the significance of molecular geometry and twisting motions that affect the relaxation dynamics in the excited state. The versatile techniques combined in this work provide strong evidence to improve our understanding of optical properties in organic nanoparticles dependent on size. 相似文献
128.
Shanmugasundaram M Wu MS Jeganmohan M Huang CW Cheng CH 《The Journal of organic chemistry》2002,67(22):7724-7729
Diynes 1a-c [X(CH(2)Ctbd1;CCO(2)Me)(2): X = (CH(2))(2), 1a, X = CH(2), 1b and X = O, 1c] undergo [2 + 2 + 2] ene-diyne cycloaddition reactions with a variety of allenes (n-butylallene 2a, phenylallene 2b, (4-chlorophenyl)allene 2c, (4-bromophenyl)allene 2d, (3-methoxyphenyl)allene 2e, 1-naphthylallene 2f, cyclohexylallene 2g and cyclopentylallene 2h) in the presence of Ni(dppe)Br(2) and Zn powder in CH(3)CN at 80 degrees C for 8 h to give the corresponding polysubstituted benzene derivatives 4a-l in good to excellent yields. Under similar reaction conditions, unsymmetrical diynes 5a-c (HCtbd1;CCH(2)XCH(2)Ctbd1;CCO(2)Me) react with allenes 2 to afford exclusively the corresponding meta-isomers 6a-g in 73-86% yields. The catalytic reaction is highly regioselective and completely chemoselective. This synthetic method is compatible with many functional groups such as Cl, Br, and OMe on the phenyl group of the allene moiety and an ether linkage in a diyne moiety. In this catalytic reaction, allenes are synthetically equivalent to terminal alkynes. Interestingly, unsymmetrical diyne 7 (MeCtbd1;C(CH(2))(4)Ctbd1;CCO(2)Me) undergoes 2:1 cocyclotrimerization with allenes 2a and 2g to afford the corresponding polysubstituted benzene derivatives 9a,b in 87% and 82% yields, respectively. A plausible mechanism involving a nickelacycloheptadiene intermediate is proposed to account for this nickel-catalyzed reaction. 相似文献
129.
Shanmugasundaram Karthikeyan 《PAMM》2007,7(1):2030009-2030010
The purpose of this paper is to establish the sufficient conditions concerning the complete controllability of stochastic integrodifferential systems in finite dimensional spaces by using the Banach fixed point theorem. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
130.
Potent, cell-permeable, and subtype-selective sialyltransferase inhibitors represent an attractive family of substances that can potentially be used for the clinical treatment of cancer metastasis. These substances operate by specifically inhibiting sialyltransferase-mediated hypersialylation of cell surface glycoproteins or glycolipids, which then blocks the sialic acid recognition pathway and leads to deterioration of cell motility and invasion. A vast amount of evidence for the in vitro and in vivo effects of sialyltransferase inhibition or knockdown on tumor progression and tumor cell metastasis or colonization has been accumulated over the past decades. In this regard, this review comprehensively discusses the results of studies that have led to the recent discovery and development of sialyltransferase inhibitors, their potential biomedical applications in the treatment of cancer metastasis, and their current limitations and future opportunities. 相似文献