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961.
Cuiling Wang Jiaxu Yan Mo Du Joseph A. Burlison Chi Li Yanni Sun Danqing Zhao Jianli Liu 《Tetrahedron》2017,73(19):2780-2785
One step synthesis of the natural product indirubin by reductive coupling of isatin with KBH4 is described and a possible mechanism for the reaction is proposed. Eleven indirubin derivatives were obtained easily from the corresponding substituted isatin. 相似文献
962.
The effective elasticity tensor of a composite is defined to be the four-tensor C which relates the average stress to the average strain. We determine it for an array of rigid spheres centered on the points of a periodic lattice in a homogeneous isotropic elastic medium. We first express C in terms of the traction exerted on a single sphere by the medium, and then derive an integral equation for this traction. We solve this equation numerically for simple, body-centered and face-centered cubic lattices with inclusion concentrations up to 90% of the close-packing concentration. For lattices with cubic symmetry the effective elasticity tensor involves just three parameters, which we compute from the solution for the traction. We obtain approximate asymptotic formulas for low concentrations which agree well with the numerical results. We also derive asymptotic results for C at high inclusion concentrations for arbitrary lattice geometries. We find them to be in good agreement with the numerical results for cubic lattices. For low and moderate concentrations the approximate results of Nemat-Nasseret al., also agree well with the numerical results for cubic lattices. 相似文献
963.
William J. Evans Prof. Thomas J. Mueller Joseph W. Ziller Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):964-975
The limits of steric crowding in organometallic metallocene complexes have been examined by studying the synthesis of [(C5Me5)3MLn] complexes as a function of metal in which L=Me3CCN, Me3CNC, and Me3SiCN. The bis(tert‐butyl nitrile) complexes [(C5Me5)3Ln(NCCMe3)2] (Ln=La, 1 ; Ce, 2 ; Pr, 3 ) can be isolated with the largest lanthanide metal ions, La3+, Ce3+, and Pr3+. The Pr3+ ion also forms an isolable mono‐nitrile complex, [(C5Me5)3Pr(NCCMe3)] ( 4 ), whereas for Nd3+ only the mono‐adduct [(C5Me5)3Nd(NCCMe3)] ( 5 ) was observed. With smaller metal ions, Sm3+ and Y3+, insertion of Me3CCN into the M? C(C5Me5) bond was observed to form the cyclopentadiene‐substituted ketimide complexes [(C5Me5)2Ln{NC(C5Me5)(CMe3)}(NCCMe3)] (Ln=Sm, 6 ; Y, 7 ). With tert‐butyl isocyanide ligands, a bis‐isocyanide product can be isolated with lanthanum, [(C5Me5)3La(CNCMe3)2] ( 8 ), and a mono‐isocyanide product with neodymium, [(C5Me5)3Nd(CNCMe3)] ( 9 ). Silicon–carbon bond cleavage was observed in reactions between [(C5Me5)3Ln] complexes and trimethylsilyl cyanide, Me3SiCN, to produce the trimeric cyanide complexes [{(C5Me5)2Ln(μ‐CN)(NCSiMe3)}3] (Ln=La, 10 ; Pr, 11 ). With uranium, a mono‐nitrile reaction product, [(C5Me5)3U(NCCMe3)] ( 12 ), which is analogous to 5 , was obtained from the reaction between [(C5Me5)3U] and Me3CCN, but [(C5Me5)3U] reacts with Me3CNC through C? N bond cleavage to form a trimeric cyanide complex, [{(C5Me5)2U(μ‐CN)(CNCMe3)}3] ( 13 ). 相似文献
964.
Dr. M. Laura Soriano Dr. Joseph T. Lenthall Dr. Kirsty M. Anderson Dr. Stephen J. Smith Prof. Jonathan W. Steed 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(35):10818-10831
Treatment of a range of bis(thiourea) ligands with inert organometallic transition‐metal ions gives a number of novel complexes that exhibit unusual ligand binding modes and significantly enhanced anion binding ability. The ruthenium(II) complex [Ru(η6‐p‐cymene)(κS,S′,N‐ L3 ?H)]+ ( 2 b ) possesses juxtaposed four‐ and seven‐membered chelate rings and binds anions as both 1:1 and 2:1 host guest complexes. The pyridyl bis(thiourea) complex [Ru(η6‐p‐cymeme)(κS,S′,Npy‐ L4 )]2+ ( 4 ) binds anions in both 1:1 and 1:2 species, whereas the free ligand is ineffective because of intramolecular NH???N hydrogen bonding. Novel palladium(II) complexes with nine‐ and ten‐membered chelate rings are also reported. 相似文献
965.
966.
A series of homo- and copolymers of acrylonitrile was prepared under radical initiation in DMF solutions. The thermal and flammability characteristics of these polymers were evaluated through thermogravimetric analyses (TGA), differential scanning calorimetry (DSC), and by limiting oxygen index (LOI) measurements. The thermal degradation behaviours of the polymers were assessed primarily with a view to designing comonomers, for acrylonitrile-based polymers, bearing flame retardant moieties. Broadly speaking, in LOI tests acrylic-based comonomers were found to improve fire performance. For instance, the incorporation of methacrylic acid gave a limiting oxygen index value of 26.4 at 30.9 mol% loading, and an intumescent char was produced upon burning. 相似文献
967.
Victor J. Bellitto Mikhail I. Melnik Daniel N. Sorensen Joseph C. Chang 《Journal of Thermal Analysis and Calorimetry》2010,102(2):557-562
We studied the surface and thermal properties of seven different varieties of cyclotrimethylene-trinitramine (RDX) crystalline
explosives from five manufacturers using differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The specific
varieties of the RDX studied were acquired from the previous Reduced Sensitivity RDX Round Robin program. They were chosen
because intensive characterization of the materials already existed including shock sensitivity and cyclotetramethylene-tetranitramine
(HMX) impurity levels. AFM scans revealed a diversity of surface defects. To quantify the surface defects on the crystalline
surface of the RDX particles, surface roughness measurements were acquired. Statistical analysis was undertaken to correlate
the observed surface, HMX impurity levels, and DSC thermal curve properties with the known shock sensitivities of the material.
It was determined that a statistically significant relationship exists between surface roughness and the shock sensitivity
of the material while no relationship was observed between the DSC thermal properties and either surface roughness or shock
sensitivity. The HMX content greatly affected the thermal properties of RDX but was uncorrelated with the shock sensitivity. 相似文献
968.
969.
970.
The chemical composition of 27 oil samples of Myrtus communis isolated from leaves collected in three locations in north-eastern Algeria was investigated by GC(RI) and 13C NMR spectroscopy. Yields ranged between 0.2-1.2% (w/w). The chemical composition of the oils was largely dominated by monoterpene hydrocarbons, with alpha-pinene (40.5-64.0%), 1,8-cineole (10.9-29.1%) and limonene (6.7-8.2%) being the major compounds. In all the samples, 3,3,5,5,8,8-hexamethyl-7-oxabicyclo[4.3.0]non-1(6)-ene-2,4-dione was identified (0.8-1.5%). The composition is similar to that reported for myrtle oils from Corsica, Sardinia and Tunisia, but differed from that of Moroccan and Spanish myrtle oils. 相似文献