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91.
Valente C Calimsiz S Hoi KH Mallik D Sayah M Organ MG 《Angewandte Chemie (International ed. in English)》2012,51(14):3314-3332
Palladium‐catalyzed cross‐coupling reactions enable organic chemists to form C? C bonds in targeted positions and under mild conditions. Although phosphine ligands have been intensively researched, in the search for even better cross‐coupling catalysts attention has recently turned to the use of N‐heterocyclic carbene (NHC) ligands, which form a strong bond to the palladium center. PEPPSI (pyridine‐enhanced precatalyst preparation, stabilization, and initiation) palladium precatalysts with bulky NHC ligands have established themselves as successful alternatives to palladium phosphine complexes. This Review shows the success of these species in Suzuki–Miyaura, Negishi, and Stille–Migita cross‐couplings as well as in amination and sulfination reactions. 相似文献
92.
Teodoro Cordova-Fraga Modesto Sosa Martha Alicia Hernandez-Gonzalez Jose Antonio Reyes-Aguilera Sergio Solorio Chystian Ramirez Evelia Bautista-Flores Guadalupe Reynaga Mario Avila-Rodriguez Jose Maria De la Roca-Chiapas 《Applied magnetic resonance》2012,42(2):161-167
Magnetic resonance imaging (MRI) of the gastrointestinal (GI) tract is still limited due to the lack of widely available oral
contrast agents (OCA). The availability of OCA for MRI of the GI tract is a necessity; different fruits might be implemented
as OCA in order to solve this need throughout the year. The objective of this study is to present an alternative fruit as
a clinical OCA for MRI of the GI tract, Achras sapota L. (common medlar). Both physical and chemical characterization of the medlar was performed. It was also tested in situ and
in vivo as an OCA for MRI of the GI tract. Results showed that this fruit had a diamagnetic behavior, although it has enough
iron, manganese and copper to contrast the GI tract in T
1- and T
2-weighted images. Thus we conclude that the medlar fruit has shown a potential as an OCA in GI evaluation by MRI, so it can
be considered as an alternative in complementation of natural OCA. 相似文献
93.
Zwergel C Gaascht F Valente S Diederich M Bagrel D Kirsch G 《Natural product communications》2012,7(3):389-394
Aurones [2-benzylidenebenzofuran-3(2H)-ones] are either natural or synthetic compounds, belonging to the flavonoid family. They are isomeric to flavones and provide a bright yellow color to the plants in which they occur. Today, a literature survey indicates that the related flavonoids have been studied not only for their physiological properties and effects on Nature, but also for their therapeutic potential. Aurones are recently attracting the interest of an increasing number of research groups, and, since the last review, some interesting advances have been made in understanding the aurones. In this review, we report the recent advances made on the synthetic routes towards aurones. We also highlight their activity in different biological areas, as well as applied genetic plant modifications to produce these colored compounds. Their synthesis, structure-activity relationships and the importance of the substitution pattern will also be mentioned. Finally, some aspects regarding the possible development of aurones will be discussed briefly. 相似文献
94.
The synthesis of the tricyclic angular chromone structure originally assigned to aspergillitine is reported. The synthesis was achieved in 11 steps and 15% overall yield from 2,4-dihydroxypropiophenone, through the intermediacy of 2,3-dimethyl-7-hydroxychromen-4-one. Construction of the nitrogen-bearing heterocyclic ring entailed a Stille cross-coupling reaction with n-Bu(3)SnCH(2)CH=CH(2), followed by double bond isomerization, oximation of the chromone carbonyl, and a final microwave-assisted electrocyclization of the thus formed 6π-electron aza-triene system. 相似文献
95.
The paper begins with a fairly detailed presentation of a general mathematical model for the dynamics of ferromagnetic bodies undergoing arbitrarily large deformations. Next, a mathematical study is presented of the evolution problem for the magnetization field in a «soft» ferromagnetic body which is «mechanically at rest». No matter how special and simple this problem within the frame-work of the full theory, the governing equation is interesting: it is identical to the dynamic version of the harmonic-map equation usually referred to in the mathematical literature as the Gilbert form of the Landau-Lifshitz equation. Motivated by recent nonuniqueness results for the dynamic harmonicmap equation, we give a new proof of global existence of weak solutions to the Gilbert-Landau-Lifshitz equation. 相似文献
96.
Ana G. Silva Nenad BundaleskiAugusto M.C. Moutinho Orlando M.N.D. Teodoro 《Applied Surface Science》2012,258(6):2006-2009
Water adsorption dynamics on two TiO2 (1 1 0) rutile surfaces at room temperature has been investigated using the work function (WF) change as a function of time. The first surface was prepared in a standard way using sputtering/annealing cycles, whereas the second one was long term annealed at 620 K in moderate vacuum conditions (the residual gas pressure of about 1 × 10−7 mbar) and cleaned afterwards. The WF change show striking difference as compared to those obtained for highly reduced TiO2 (1 1 0) rutile or the (2 × 1) reconstructed surfaces. For the first kind of surface we show that the observed adsorption dynamics can be qualitatively explained by the present understanding of the water adsorption on non-reconstructed TiO2 (1 1 0) rutile surface according to which the bridging oxygen vacancies and Ti rows are the main adsorption sites. Although generally similar to the former results, water adsorption dynamics on the second kind of the surface has an additional feature that can be only explained by a new adsorption site, which we suggest to be due to (2 × 1) reconstructed regions coexisting with the non-reconstructed TiO2 (1 1 0) surface. 相似文献
97.
98.
Roberto Acevedo Teodoro Meruane Jorge R. Letelier 《Theoretical chemistry accounts》1984,64(5):339-369
The theory of radiative transitions, in centrosymmetric complexes, is examined in great detail, within the framework of the crystal field method.In connection with radiative transitions, the current method of calculations, with and without invoking closure approximation, are considered from a purely theoretical point of view, by taking advantage of the irreducible tensor method put forward by Griffith.Explicit equations are derived throughout the course of this work to account for the vibronic electric dipole moments, associated with d-d and f-f type of excitations.At high Academy of Pedagogic Sciences, Santiago, Chile. 相似文献
99.
J. Dorenbosch F. Udo J. V. Allaby U. Amaldi G. Barbiellini M. Baubillier F. Bergsma A. Capone W. Flegel F. Grancagnolo M. Jonker L. Lanceri M. Metcalf C. Nieuwenhuis J. Panman R. Plunkett C. Santoni K. Winter I. Abt F. W. Büsser H. Daumann P. D. Gall T. Hebbeker F. Niebergall P. Stähelin P. Gorbunov E. Grigoriev V. Kaftanov V. Khovansky A. Rosanov A. Baroncelli L. Barone B. Borgia C. Bosio M. Diemoz U. Dore F. Ferroni E. Longo L. Luminari P. Monacelli S. Morganti F. de Natoristefani L. Tortora V. Valente 《Zeitschrift fur Physik C Particles and Fields》1991,51(1):142-142
100.
Bellotti R Cafagna F Caliccio M De Cataldo G De Marzo C Erriquez O Favuzzi C Giglietto N Nappi E Spinelli P Cecchini S Fabbri M Giacomelli G Mandrioli G Matteuzzi P Pal B Patrizii L Predieri F Sanzani GL Serra P Spurio M Ahlen S Ficenec D Hazen E Klein S Levin D Marin A Stone JL Sulak LR Worstell W Barish B Coutu S Hong J Liu G Peck C Solie D Steele J Lane C Steinberg R Battistoni G Bilokon H Bloise C Campana P Chiarella V Forti C Grillo A Iarocci E Marini A Patera V Reynoldson J Ronga F 《Physical review D: Particles and fields》1990,42(5):1396-1403