排序方式: 共有57条查询结果,搜索用时 31 毫秒
31.
Hobbs C Yang YC Ling J Nicola S Su HL Bazzi HS Bergbreiter DE 《Organic letters》2011,13(15):3904-3907
The preparation of polyethylene-oligomer (PE(olig))-supported N-heterocyclic carbene ligands (NHCs) and their Ru complexes is described. These complexes are structurally analogous to their low molecular weight counterparts and can serve as thermomorphic, recoverable/recyclable ring-closing metathesis (RCM) catalysts. Because of the insolubility of PE(olig)-supported species at 25 °C, such complexes can perform homogeneous RCM reactions at 65 °C and, upon cooling, precipitate as solids. This allows for their quantitative separation from solutions of products. 相似文献
32.
Analogs of Grubbs' second generation catalyst with hydrophilic phosphine ligands are synthesized, and those with Cy(2)PCH(2)CH(2)N(CH(3))(3)(+) Cl(-) and Cy(2)PCHCH(2)CH(2)N(CH(3))(2)(+)CH(2)CH(2) Cl(-) give much faster ring closing metatheses under CH(2)Cl(2)/aqueous or CH(2)Cl(2)/aqueous HCl biphasic as opposed to CH(2)Cl(2) monophasic conditions. This is attributed to rapid phase transfer of the dissociated ligand to the aqueous phase, where under acidic conditions it is protonated. 相似文献
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34.
C. Curceanu M. Bazzi G. Beer L. Bombelli A. M. Bragadireanu M. Cargnelli M. Catitti C. Fiorini T. Frizzi F. Ghio B. Girolami C. Guaraldo M. Iliescu T. Ishiwatari P. Kienle P. Lechner P. Levi Sandri A. Longoni V. Lucherini J. Marton D. Pietreanu T. Ponta D. L. Sirghi F. Sirghi H. Soltau L. Struder E. Widmann J. Zmeskal 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):537-539
The DAΦNE electron-positron collider at the Frascati National Laboratories has made available a unique “beam" of negative kaons providing
unprecedented conditions for the study of the low-energy kaon-nucleon interaction, a field still largely unexplored. The DEAR
(DAΦNE Exotic Atom Research) experiment at DAΦNE and its successor SIDDHARTA (SIlicon Drift Detector for Hadronic Atom Research by Timing Application) aim at a precision
measurement of the strong-interaction shift and width of the fundamental 1s level, via the measurement of the X-ray transitions to this level, for kaonic hydrogen and kaonic deuterium. The aim is to
extract the isospin-dependent antikaon-nucleon scattering lengths and to contribute to the understanding of aspects of chiral
symmetry breaking in the strangeness sector. 相似文献
35.
Terminally vinyl-functionalized polyisobutylene (PIB) oligomers can be easily transformed into end-functionalized PIB-bound Ru metathesis catalysts. The nonpolar catalysts so prepared can be used as solutions in heptane and recycled by a gravity-based extraction after addition of a heptane-immiscible polar solvent. This paper describes the synthesis and the recycling of a PIB-supported second-generation Hoveyda-Grubbs catalyst for Ru-catalyzed ring-closing metathesis and ring-opening metathesis polymerizations. 相似文献
36.
Christos P. Constantinides Maria Koyioni Fadwat Bazzi Maria Manoli Daniel B. Lawson Panayiotis A. Koutentis 《Molecules (Basel, Switzerland)》2021,26(19)
The crystal structure and solid-state packing of 4-chloro-5H-1,2,3-dithiazol-5-one and two polymorphs of 4-chloro-5H-1,2,3-dithiazole-5-thione were analyzed and compared to structural data of similar systems. These five-membered S,N-rich heterocycles are planar with considerable bond localization. All three structures demonstrate tight solid-state packing without voids which is attributed to a rich network of short intermolecular electrostatic contacts. These include Sδ+…Nδ−, Sδ+…Oδ−, Sδ+…Clδ− and Sδ+…Sδ− interactions that are well within the sum of their van der Waals radii (∑VDW). B3LYP, BLYP, M06, mPW1PW, PBE and MP2 were employed to calculate their intramolecular geometrical parameters, the Fukui condensed functions to probe their reactivity, the bond order, Bird Index and NICS(1) to establish their aromaticity. 相似文献
37.
C. Curceanu M. Bazzi G. Beer L. Bombelli A. M. Bragadireanu M. Cargnelli C. Fiorini T. Frizzi F. Ghio B. Girolami C. Guaraldo R. Hayano M. Iliescu T. Ishiwatari M. Iwasaki P. Kienle P. Lechner P. Levi Sandri A. Longoni V. Lucherini J. Marton S. Okada D. Pietreanu T. Ponta A. Romero Vidal A. Scordo H. -X. Shi D. L. Shirghi F. Sirghi H. Soltau L. Struder H. Tatsuno O. Vazquez Doce E. Widmann J. Zmeskal 《Hyperfine Interactions》2009,188(1-3):11-17
Radioactive 57Mn+(T 1/2?= 1.5 min) ions have been implanted at the ISOLDE facility at CERN with 60 keV energy to fluences <1012/cm2 into p-type Si1???x Ge x (x < 0.1) single crystals held at 300–600 K. The implantation and annealing processes result in the majority of the implanted Mn ions occupying substitutional lattice sites. In the subsequent 57Mn nuclear β ???-decay to the 14.4 keV Mössbauer state of 57Fe (T 1/2?= 100 ns), an average recoil energy of 40 eV is imparted to the 57Fe daughter atoms which results in a large fraction being expelled into tetrahedral interstitial sites and the creation of a vacancy. The remainder occupies substitutional sites. This technique of recoil production of 57m FeI thus allows for the study of the diffusion characteristics of interstitial Fe. From the temperature dependent line broadening, the activation energies have been determined and decrease with increasing Ge concentration which contributes significantly to the increase of the jump frequency. A similar result has been obtained in n-type SiGe but there the values for the activation energies were much higher. 相似文献
38.
SIDDHARTA Collaboration Bazzi M Beer G Bombelli L Bragadireanu AM Cargnelli M Curceanu Petrascu C Dʼuffizi A Fiorini C Frizzi T Ghio F Guaraldo C Hayano RS Iliescu M Ishiwatari T Iwasaki M Kienle P Levi Sandri P Longoni A Marton J Okada S Pietreanu D Ponta T Rizzo A Romero Vidal A Sbardella E Scordo A Shi H Sirghi DL Sirghi F Tatsuno H Tudorache A Tudorache V Vazquez Doce O Wünschek B Widmann E Zmeskal J 《Physics letters. [Part B]》2012,714(1):40-43
The kaonic (3)He and (4)He X-rays emitted in the [Formula: see text] transitions were measured in the SIDDHARTA experiment. The widths of the kaonic (3)He and (4)He 2p states were determined to be [Formula: see text], and [Formula: see text], respectively. Both results are consistent with the theoretical predictions. The width of kaonic (4)He is much smaller than the value of [Formula: see text] determined by the experiments performed in the 70's and 80's, while the width of kaonic (3)He was determined for the first time. 相似文献
39.
Dr. Robert Tuba Dr. Zhenxing Xi Prof. Hassan S. Bazzi Prof. John A. Gladysz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(45):15894-15906
With metal‐based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L′nM?L) to activate the catalyst. The resulting coordinatively unsaturated active species (L′nM) can either back react with the ligand in a k?1 step, or combine with the substrate in a k2 step. When dissociation is not rate determining and k?1[L] is greater than or comparable to k2[substrate], this slows the rate of reaction. By introducing a phase label onto the ligand L and providing a suitable orthogonal liquid or solid phase, dramatic rate accelerations can be achieved. This phenomenon is termed “phase‐transfer activation”. In this Concept, some historical antecedents are reviewed, followed by successful applications involving fluorous/organic and aqueous/organic liquid/liquid biphasic catalysis, and liquid/solid biphasic catalysis. Variants that include a chemical trap for the phase‐labeled ligands are also described. 相似文献
40.
Margherita BarberoStefano Bazzi Silvano CadamuroLorenzo Di Bari Stefano Dughera Giovanni Ghigo Daniele PadulaSilvia Tabasso 《Tetrahedron》2011,67(32):5789-5797
We have recently reported the use, in catalytic amounts, of 1,2-benzenedisulfonimide as a safe Brønsted acid in some acid-catalyzed organic reactions. With the design of new and chiral acid organocatalysts with the structure of 1,2-benzenedisulfonimide in mind, we herein propose a synthesis of 1,2-benzenedisulfonimide derivatives bearing an aryl group in the 3-position with good overall yields. The chirality of these compounds is due to the hindered rotation of the aryl group (atropisomerism). We resolved the atropisomers of one of these compounds. 相似文献