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排序方式: 共有443条查询结果,搜索用时 15 毫秒
1.
The treatment of tertiary esters with triphenylphosphine and iodine under mild conditions gives the most stable alkene in good yield. Formates, acetates and trifluoroacetates were studied. 相似文献
2.
I. P. Romanova S. G. Fattakhov A. A. Nafikova I. I. Vandyukova R. R. Shagidullin N. M. Azancheev V. S. Reznik O. G. Sinyáshin 《Russian Chemical Bulletin》1998,47(9):1812-1819
The reactions of phosphine derivatives of diallyl isocyanurates with palladium(ii) dichloride lead to the formation of complexes, whose structure, composition, and stability depend on the length of the methylene
chain between the isocyanurate and diphenylphosphine fragments in the ligand. 1,3-Diallyl-5-[5′-(diphenylphosphino)pentyl
and 10′-(diphenyl-phosphino)decyl] isocyanurates with PdCl2 form monomeric L2PdCl2
trans-complexes in which P atoms of the ligands participate in coordination with the metal. 1,3-Diallyl-5-[2′-(diphenylphosphino)ethyl]
isocyanurate with PdCl2 forms a dimeric (LPdCl2)2 complex, which decomposes in a solution to the monomer including solvent molecule into the coordination sphere of the metal.
The reactions of 1,3-diallyl-5-[4′-(diphenylphosphino)butyl] isocyanurate and 1,3-diallyl-5-[6′-(diphenylphosphino)hexyl]
isocyanurate with PdCl2 give monomeric chelate LPdCl2 complexes in which one of the allyl groups of the isocyanurate cycle participates in coordination with the central ion along
with the phosphorus atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1859–1865, September, 1998. 相似文献
3.
Fadila Balegroune Pierre Braunstein Laurent Douce Yves Dusausoy Daniel Grandjean Michael Knorr Martin Strampfer 《Journal of Cluster Science》1992,3(3):275-296
The reactions of K[Fe{Si(OMe)3}(CO)3(PY)][PY=Ph2PCH2C(O)Ph, Ph2PCH2C(O)[(-C5H4)FeCp] (Cp=5-C5H5), Ph2P(CH2)2CN] with CdCl2·2.5H2O, ZnX
2 (X=Cl, I) or InCl3 afforded Fe-Cd-Fe or Fe-M(-X)2
M-Fe (M=Cd, Zn, In;X=Cl, I) and Fe-InCl2 complexes. Some of them contain an unusual and labile -2-SiO alkoxysilyl bridge which may be associated with a bridging mode for the ketophosphine ligand (first such example structurally established), thus providing original results in bimetallic chemistry on the intramolecular coordination of oxygendonor functions ofchemically different hemilabile ligands firmly attached to a neighboring metal center. The structures of the trinuclear complex (3), of the chlorobenzene solvate of the tetranuclear complex (4a·C6H5Cl) and of [mer-(OC)3{(EtO)3Si} (4e) have been determined by X-ray diffraction. Crystals of 3 are orthorhombic, space groupPbcn, witha=19.010(4),b=11.766(5),c=26.998(7)Å, andZ=4. Crystals of4a·C6H5Cl are monoclinic, space groupC2/c witha=22.455(3),b=17.680(2),c=16.627(4)Å, =90.80(4)°, andZ=4. Crystals of4e are monoclinic, space groupC2/c witha=25.392(5),b=18.554(6),c=16.28(1)Å, =120.73(3)°, andZ=4. The structures were solved using direct methods and Fourier difference techniques and refined by blocked full-matrix least squares toR=0.035 (R
w
=0.049) for 2719 observed reflections, toR=0.042 (R
w
=0.056) for 3082 observed reflections, and toR=0.057 (R
w
=0.075) for 1850 observed reflections for3, 4a·C6H5Cl and4e, respectively. The Fe-Zn complexes (9a), (9b) and (9c) were prepared and characterized by spectroscopic methods.Part 21 in the Series: Complexes with Functional Phosphines. Part 20: P. Braunstein, S. Coco Cea, A. DeCian, and J. Fischer (1992).Inorg. Chem.
31, 4203. 相似文献
4.
Protein fold recognition 总被引:4,自引:0,他引:4
Summary An important, yet seemingly unattainable, goal in structural molecular biology is to be able to predict the native three-dimensional
structure of a protein entirely from its amino acid sequence. Prediction methods based on rigorous energy calculations have
not yet been successful, and best results have been obtained from homology modelling and statistical secondary structure prediction.
Homology modelling is limited to cases where significant sequence similarity is shared between a protein of known structure
and the unknown. Secondary structure prediction methods are not only unreliable, but also do not offer any obvious route to
the full tertiary structure. Recently, methods have been developed whereby entire protein folds are recognized from sequence,
even where little or no sequence similarity is shared between the proteins under consideration. In this paper we review the
current methods, including our own, and in particular offer a historical background to their development. In addition, we
also discuss the future of these methods and outline the developments under investigation in our laboratory. 相似文献
5.
Boris A TrofimovSvetlana F Malysheva Boris G SukhovNatal'ya A Belogorlova Elena Yu SchmidtLyubov N Sobenina Vladimir A KuimovNina K Gusarova 《Tetrahedron letters》2003,44(13):2629-2632
Secondary phosphines 1-3 react readily with N-vinylpyrroles 4 and 5 under radical initiation to give regiospecifically anti-Markovnikov adducts, diorganyl-2-(1-pyrrolyl)ethylphosphines 6a-d, highly reactive building blocks for organic synthesis, in 88-91% yields. 相似文献
6.
Norikazu Nishiyama Yong-Rong Dong Tao Zheng Yasuyuki Egashira Korekazu Ueyama 《Journal of membrane science》2006,280(1-2):603-609
Microporous carbon membranes were prepared on an -alumina support by a pyrolysis of cationic tertiary amine/anionic polymer composites. The precursor solutions contain a thermosetting resorcinol/formaldehyde (RF) polymer and a cationic tertiary amine. Three types of cationic tertiary amines with different chain lengths were used, such as tetramethlammonium bromide (TMAB), tetrapropylammonium bromide (TPAB) and cetyltrimethylammonium bromide (CTAB). A porous structure was produced by a decomposition of the amine and the resulting pores assisted the further gasification of the RF polymer at high temperature. The carbon/alumina membranes have thin and continuous carbon top layers with a thickness of 1 μm. Gas permeation tests were performed using single gases of CO2, O2, N2, CF4, n-C4H10 and i-C4H10, as well as binary mixtures of CH4/n-C4H10 and N2/CF4 at different temperatures between 23 and 150 °C. The carbon membrane prepared using TMAB showed separation factors higher than 650 for the CH4/n-C4H10 mixtures and higher than 8100 for the N2/CF4 mixture. From the permeation of pure gases with different molecular sizes, the pore sizes of the carbon membrane prepared using TMAB, TPAB and CTAB are estimated to be 4.0, 5.0 and larger than 5.5 Å, respectively, indicating that the micropore size of the carbon membranes is controllable by using different amines. 相似文献
7.
冻干保护剂溶液低温退火特性的研究 总被引:3,自引:0,他引:3
利用差示扫描量热仪(DSC)研究了10%叔丁醇/10%蔗糖/水溶液的冻结特性, 退火温度及退火时间, 分析了溶液的退火行为. 实验结果表明, 溶液降温时, 蔗糖的存在阻碍了叔丁醇析出, 最大冻结浓缩溶液玻璃化转变温度Tg′由-32.5 ℃降低到-42.0 ℃, 升温时在-30 ℃叔丁醇发生反玻璃化. 在反玻璃化峰附近的温度进行退火可使叔丁醇充分析出, Tg′由-42.0 ℃上升到-34.9 ℃. 所需的退火时间与退火温度有关, 退火温度越接近Tg′, 所需的退火时间越长. 在-37 ℃时, 退火20 min可完全消除反玻璃化. 相似文献
8.
Renata Kolano? Teresa Borowiak Grzegorz Dutkiewicz 《Journal of Molecular Structure》2005,737(1):75-81
The X-ray and spectroscopic results clearly indicate that the (+)-2-thiono-17-oxosparteine (1) and (+)-2,17-ditihionosparteine (2) are conformationally rigid. In order to analyze deviations of lactam/thiolactam groups from planarity induced by ring constraints, the Dunitz-Winkler approach has been used. The lactam and thiolactam groups are close to planarity, only the lactam group in one of the two independent molecules of 1 is markedly non-planar. The bond angles in the thiolactam and lactam groups are highly diverse. Rings A and C adopt a distorted sofa conformation in both compounds. The distortions in the molecules of 2 as compared with those in the related monothiolactams correspond to the unusual chemical shifts of H5(eq), H5(ax) and H11, as well as to the extremely low J5ax-6 and extremely large J5eq-6 coupling constants. Also chemical shifts show a similar regularity being extremely high and low for C2 and C17, respectively. 相似文献
9.
Summary A new gas chromatographic method for the simultaneous determination of the degree of hydrogenation of ketopantolactone and the enantiomeric excess of pantolactone does not require any derivatisation.
Bestimmung von Enantiomerenüberschuß und Hydriergrad bei der enantioselektiven Hydrierung von Ketopantolacton (Kurze Mitt.)
Zusammenfassung Zur Bestimmung des Hydriergrads von Ketopantolacton und des Enantiomerenüberschusses von Pantolacton wird ein neues gaschromatographisches Verfahren eingesetzt, das keine Derivatisierung erfordert.相似文献
10.
The intermolecular Pauson-Khand reaction between norbornene and dicobalt carbonyl complexes of phenylacetylene substituted with chiral phosphorus ligands has been investigated. High yields (?98%) and enantiomeric excesses of up to 56% have been observed. 相似文献