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21.
Hien Vuong 《合成通讯》2019,49(2):316-323
Heterocyclic imines provide biaryl products by a two-step transformation. The first transformation involves a Diels–Alder reaction with a multiply protonated imine to give a tetrahydroquinoline product, whereas the second step involves oxidation with elemental sulfur at 260?°C. 相似文献
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Jeishla L. M. Matos Samantha A. Green Yuge Chun Vuong Q. Dang Russell G. Dushin Paul Richardson Jason S. Chen David W. Piotrowski Brian M. Paegel Ryan A. Shenvi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):13098-13103
Preparative reactions that occur efficiently under dilute, buffered, aqueous conditions in the presence of biomolecules find application in ligation, peptide synthesis, and polynucleotide synthesis and sequencing. However, the identification of functional groups or reagents that are mutually reactive with one another, but unreactive with biopolymers and water, is challenging. Shown here are cobalt catalysts that react with alkenes under dilute, aqueous, buffered conditions and promote efficient cycloisomerization and formal Friedel–Crafts reactions. The constraining conditions of bioorthogonal chemistry are beneficial for reaction efficiency as superior conversion at low catalyst concentration is obtained and competent rates in dilute conditions are maintained. Efficiency at high dilution in the presence of buffer and nucleobases suggests that these reaction conditions may find broad application. 相似文献
23.
Capon RJ Vuong D McNally M Peterle T Trotter N Lacey E Gill JH 《Organic & biomolecular chemistry》2005,3(1):118-122
The principle nematocidal agent present in a southern Australian marine sponge of the genus Echinodictyum has been isolated and identified as the novel betaine (+)-echinobetaine B (6), and the structure assigned by spectroscopic analysis has been confirmed by total synthesis. Preliminary SAR conclusions are drawn from analysis of synthetic intermediates and the known marine metabolites zooanemonin (12) and norzooanemonin (13), and the new sponge metabolite norzooanemonin methyl ester (14). The latter compound is reported for the first time from a selection of Australian sponges, including an Axinyssa sp., a Niphates sp., an Axinella sp. and a Ptilocaulis sp. 相似文献
24.
Vu T. Nguyen Graham C. Haug Viet D. Nguyen Ngan T. H. Vuong Hadi D. Arman Oleg V. Larionov 《Chemical science》2021,12(18):6429
Sulfonamides feature prominently in organic synthesis, materials science and medicinal chemistry, where they play important roles as bioisosteric replacements of carboxylic acids and other carbonyls. Yet, a general synthetic platform for the direct conversion of carboxylic acids to a range of functionalized sulfonamides has remained elusive. Herein, we present a visible light-induced, dual catalytic platform that for the first time allows for a one-step access to sulfonamides and sulfonyl azides directly from carboxylic acids. The broad scope of the direct decarboxylative amidosulfonation (DDAS) platform is enabled by the efficient direct conversion of carboxylic acids to sulfinic acids that is catalyzed by acridine photocatalysts and interfaced with copper-catalyzed sulfur–nitrogen bond-forming cross-couplings with both electrophilic and nucleophilic reagents.Sulfonamides are now accessible directly from carboxylic acids by a one-step, tricomponent decarboxylative amidosulfonation that provides the missing link between the two key functionalities. 相似文献
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Vuong LT Grow TD Ishaaya A Gaeta AL 't Hooft GW Eliel ER Fibich G 《Physical review letters》2006,96(13):133901
We theoretically and experimentally investigate the self-focusing of optical vortices in Kerr media. We observe collapse to a distinct self-similar profile, which becomes unstable to azimuthal perturbations. We analyze the azimuthal modulational instability for ring-shaped vortices and predict the number of azimuthal maxima solely as a function of power and topological charge. In our experiments, the observed multiple-filamentation patterns are in excellent agreement with our theoretical analysis. 相似文献
27.
Francisco J. Aragón Artacho Ronan M. T. Fleming Phan T. Vuong 《Mathematical Programming》2018,169(1):95-118
We introduce two new algorithms to minimise smooth difference of convex (DC) functions that accelerate the convergence of the classical DC algorithm (DCA). We prove that the point computed by DCA can be used to define a descent direction for the objective function evaluated at this point. Our algorithms are based on a combination of DCA together with a line search step that uses this descent direction. Convergence of the algorithms is proved and the rate of convergence is analysed under the ?ojasiewicz property of the objective function. We apply our algorithms to a class of smooth DC programs arising in the study of biochemical reaction networks, where the objective function is real analytic and thus satisfies the ?ojasiewicz property. Numerical tests on various biochemical models clearly show that our algorithms outperform DCA, being on average more than four times faster in both computational time and the number of iterations. Numerical experiments show that the algorithms are globally convergent to a non-equilibrium steady state of various biochemical networks, with only chemically consistent restrictions on the network topology. 相似文献
28.
The space-charge field built in a polymeric photorefractive polymer was calculated by a simple method based on the oriented gas model. When anisotropic chromophores in a photorefractive polymer were exposed to an external field, they oriented preferentially to exhibit a birefringence. Then, under illumination of two coherent beams and an external field, they reoriented to form a photorefractive grating. During the formation of the grating, the chromophores were reoriented by the space-charge field as well as by the external applied field. The birefringence induced in the material by an external electric field was determined by measuring the transmittance of the sample which is placed between crossed polarizers, where birefringence depicts the orientation of the chromophores. By measuring the diffraction efficiency with a modified degenerate four-wave mixing setup, the index amplitude of the grating was determined. Finally, the space-charge field was determined by comparing the diffraction efficiency with the birefringence with respect to the applied electric field. In our study, the space-charge field was about 20% of the external applied field, which coincided with previous results obtained from our laboratory. 相似文献
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Mechanics of Composite Materials - The nonlinear buckling and postbuckling of FGM toroidal shell segments surrounded by elastic foundations in a thermal environment and subjected to a torsional... 相似文献
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Van Loat Bui Duong Van-Hao Duong Nguyen Thanh Leuangtakoun Somsavath Duc Thang Duong Anh Hung Vu Anh Duc Vu Tran Hoai-Nam Nguyen Van-Dung Thi Huyen-Trang Vuong 《Journal of Radioanalytical and Nuclear Chemistry》2021,329(2):991-1000
Journal of Radioanalytical and Nuclear Chemistry - The 226Ra, 232Th (228Ra), 40K activity concentrations in soil distributed in 67 points belonging to different geological formations in Khammouan,... 相似文献