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排序方式: 共有163条查询结果,搜索用时 31 毫秒
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63.
Sethuraman KannanGalmari Venkatachalam Ha-Jin LeeByoung Koun Min Woong KimEunhae Koo Young Rag DoSungho Yoon 《Polyhedron》2011,30(2):340-346
The metal coordination geometry in the active site of metalloproteins are very different from the one of small inorganic complexes, due to the inflexibility of the ligand set from amino acid side chains different from freely moving ligand set in synthesis. Using the sterically hindered 2,6-di-(p-fluorophenyl)benzoate(L) ligand, a series of mononuclear Co(II), Ni(II) and Cu(II) complexes of general formula [M(L)2(Hdmpz)2] (where, Hdmpz = 3,5-dimethyl pyrazole) have been synthesized and characterized by the variety of spectroscopic methods. A distorted octahedral geometry in case of nickel, tetrahedral geometry for cobalt and square pyramidal in copper was observed in the X-ray studies, which also revealed that the uncoordinated oxygen atom of the carboxylate group forms intramolecular hydrogen bonding with the N-H group of the coordinated 3,5-dimethylpyrazole in case of cobalt and copper. 相似文献
64.
Alasdair J. RobbieAndrew R. Cowley Michael W. Jones Jonathan R. Dilworth 《Polyhedron》2011,30(11):1849-1856
Two new sterically demanding diaminophosphinothiolate ligands (HL1 and HL2) have been prepared and the X-ray crystal structure of the Li salt of HL2 has been determined. The complex [Pd(L1)2] was fully characterized, but in contrast to other phosphinothiolates, complexes with the M(L)3 stoichiometry could not be prepared. Reaction of LH1 with Ni(II) led to cleavage of the arythiolate group and isolation of a thiolate bridged dimer, confirmed by an X-ray crystal structure. The Rh(I) complexes [Rh(nbd)L] (L = L1, L2) were characterized including an X-ray structure. 相似文献
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66.
Solid-phase synthesis of aryl, heteroaryl, and sterically hindered alkyl amines using the Curtius rearrangement 总被引:1,自引:0,他引:1
An efficient method for the solid-phase synthesis of aryl amines, heteroaryl amines, and sterically hindered alkyl amines has been developed. The key step in this process was the formation of resin-bound carbamates (B) by the Curtius rearrangement of aryl carboxylic acids with Wang resin providing the trapping hydroxyl group. N-Alkylation reactions of B gave secondary amines in good yield. Some biaryl amines, which are found widely in biologically active substances, were also prepared by the Suzuki reaction of resin-bound carbamates of 2-iodoaniline (16) or 3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (21). The developed methods can be applied to the preparation of libraries containing aryl, heteroaryl, and sterically hindered alkyl amine structures as the pharmacophores. 相似文献
67.
Yen-Hsin Chen Shu-Jyun Huang Tung-Yu Hsu Pei-Yu Hung Ting-Rong Wei Dong-Sheng Lee Ta-Jung Lu 《Molecules (Basel, Switzerland)》2021,26(21)
A novel non-C2-symmetric bis-benzimidazolium salt derived from (±)-valinol has been prepared by a simple and straightforward process in good yield. The structure of bis-benzimidazolium salt provided a bulky steric group on the ethylene bridge; which facilitates the catalytic efficacy in the C(sp2)–C(sp2) formation. Its catalytic activity in Suzuki–Miyaura cross-coupling reaction of unactivated aryl chlorides has been found to have high efficacy in 1 mol% Pd loading. This protocol demonstrated the potential on the synthesis of sterically hindered biaryls. 相似文献
68.
6-Halouridine derivatives were synthesized regiospecifically through the coupling of N3-protected 6-halouracil to a ribose derivative. The combination of the silylating reagent N,O-bis(trimethylsilyl)acetamide and Lewis acid catalyst trimethylsilyl trifluoromethanesulfonate is unique in their ability to facilitate the coupling of sterically hindered pyrimidine bases to ribose to form nucleoside derivatives. 相似文献
69.
《Journal of separation science》2017,40(11):2366-2373
Hindered amine light stabilizers are essential for the stabilization of synthetic polymers, particularly for materials used for outdoor applications. Although up to now a considerable number of studies dealing with the analytics of this class of stabilizers had been published, especially the determination of oligomeric hindered amine light stabilizers is still an analytical challenge. In the current work, a fast and simple liquid chromatographic method for the quantitative determination of oligomeric hindered amine light stabilizers is presented. A key aspect of this method is their completely different retention behavior depending on the pH, enabling a single peak elution approach by a pH gradient run. This allows a quantitation with simple UV detection independent of the actual oligomeric composition. Calibration curves within the concentration range relevant for the analysis of real polymer samples (LOQ = 70 mg/L) were constructed with R 2 values above 0.99. Spiked extracts from polyolefin samples showed recovery rates between 97.3 and 102.9% for five different commercial hindered amine light stabilizers. Relative standard deviations were between 2.0 and 3.9%. Furthermore, it was demonstrated that the employed approach can be easily adapted for mass spectrometry detection. 相似文献
70.
Guglielmo Bertolini Luigi Lanzini Luca Marchese Arnaldo Roggero Alessandro Lezzi Silvestro Costanzi 《Journal of polymer science. Part A, Polymer chemistry》1994,32(5):961-969
Monomers having a norbornene as polymerizable group and a 2,2,6,6-tetramethyl piperidine as stabilizing moiety were prepared. This monomer was successfully copolymerized with ethylene using VAc3/AlEt2Cl as the catalytic system. Copolymers exhibited better stability under accelerated aging than polyethylene stabilized by classical blending with commercial hindered amines. Any attempt made to obtain copolymers using a high activity TiCl4/MgCl2 catalyst was unsuccessful. © 1994 John Wiley & Sons, Inc. 相似文献