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551.
A.R Siedle Robert J Webb Myles Brostrom Kristin Erickson Victor G Young Jr. 《Journal of fluorine chemistry》2003,122(2):175-182
Hydrolysis of the imine perfluoro-5-aza-4-nonene, C3F7CFNC4F9, in ether was studied by several spectroscopic techniques including NMR. The initial product is C3F7CONHC4F9 which is converted to (C3F7CO)2NH and then to C3F7CONH2 and C3F7CO2H. Solvolysis in liquid ammonia afforded the amidine C3F7C(NH)NH2. Reaction with hydrazine produced 3,5-bis(heptafluoropropyl)-1,2,4-triazole whose crystal structure is reported. 相似文献
552.
Structural aspects of the binding of halides in the octaaza cryptand (1,4,11,14,17,24,29,36-octa-azapentacyclo[12.12.12.2(6,9).2(19,22).2(31,34)]-tetratetraconta-6(43),7,9(44),19(41),20,22(42),31(39),32,34(40)-nonaene, N(CH2CH2NHCH2-p-xylyl-CH2NHCH2CH2)3N), L1, were examined for fluoride, chloride, and bromide. Crystallographic results for two different fluoride complexes indicated cascade-like coordination, with two fluoride ions inside the tren-based cavity, bridged by a water molecule. In the two different chloride structures, a single chloride and a water molecule occupied the cavity. The bromide structure contained two crystallographically independent cationic cryptands. Unit A consisted of a bromide on one side of the cavity and three disordered water molecules situated between the cryptand arms on the other side. Unit B also had a bromide inside the cavity at one side, but a single molecule of water was centered at the other side of the cavity. Association constants for the three ions, determined by NMR titrations in aqueous solution at pH 5, revealed log Ka=3.15(5), 3.37(3), and 3.34(4) for fluoride, chloride, and bromide, respectively. 相似文献
553.
The palladium-catalyzed N-(hetero)arylation of a number of heteroarylamines including 2-aminopyridines, 2-aminothiazoles, and their analogues has been realized using Xantphos as the ligand. Weak bases such as Cs(2)CO(3), Na(2)CO(3), and K(3)PO(4) were used in most cases to allow for the introduction of functional groups. Choice of the base and solvent was critical for the success of these reactions. [reaction: see text] 相似文献
554.
Payack JF Vazquez E Matty L Kress MH McNamara J 《The Journal of organic chemistry》2005,70(1):175-178
An efficient synthesis of the potent KDR inhibitor 3-[5-[[4-(methylsulfonyl)-1-piperazinyl]methyl]-1H-indole-2-yl]quinolin-2(1H)-one (1) is described. The process features a noncryogenic indole boronation and a dicyclohexylamine-mediated Suzuki coupling. 相似文献
555.
The total and semi syntheses of (2R,3R)-epigallocatechin-3-O-(4-hydroxybenzoate), a novel catechin from Cistus salvifolius, were accomplished. The proteasome inhibition and cytotoxic activities of the synthetic compound and its acetyl derivative were studied and compared with (2R,3R)-epigallocatechin-3-gallate (EGCG), the active component from green tea. 相似文献
556.
Musgrave KB Laplaza CE Holm RH Hedman B Hodgson KO 《Journal of the American Chemical Society》2002,124(12):3083-3092
In earlier work, de novo designed peptides with a helix-loop-helix motif and 63 residues have been synthesized as potential scaffolds for stabilization of the [Ni(II)-X-Fe(4)S(4)] bridged assembly that is the spectroscopically deduced structure of the A-Cluster in clostridial carbon monoxide dehydrogenase. The 63mers contain a consensus tricysteinyl ferredoxin domain in the loop for binding an Fe(4)S(4) cluster and Cys and His residues proximate to the loop for binding Ni(II), with one Cys residue designed as the bridge X. The metallopeptides HC(4)H(2)-[Fe(4)S(4)]-Ni and HC(5)H-[Fe(4)S(4)]-M, containing three His and one Cys residue for Ni(II) coordination and two His and two Cys residues for binding M = Ni(II) and Co(II), have been examined by Fe-, Ni-, and Co-K edge spectroscopy and EXAFS. All peptides bind an [Fe(4)S(4)](2+) cubane-type cluster. Interpretation of the Ni and Co data is complicated by the presence of a minority population of six-coordinate species with low Z ligands, designated for simplicity as [M(OH(2))(6)](2+). Best fits of the data were obtained with ca. 20% [M(OH(2))(6)](2+) and ca. 80% M(II) with mixed N/S coordination. The collective XAS results for HC(4)H(2)-[Fe(4)S(4)]-Ni and HC(5)H-[Fe(4)S(4)]-M demonstrate the presence of an Fe(4)S(4) cluster and support the existence of the distorted square-planar coordination units [Ni(II)(S.Cys)(N.His)(3)] and [Ni(II)(S.Cys)(2)(N.His)(2)] in the HC(4)H(2) and HC(5)H metallopeptides, respectively. In the HC(5)H metallopeptide, tetrahedral [Co(II)(S.Cys)(2)(N.His)(2)] is present. We conclude that the designed scaffolded binding sites, including Ni-(mu(2)-S.Cys)-Fe bridges, have been achieved. This is the first XAS study of a de novo designed metallopeptide intended to stabilize a bridged biological assembly, and one of a few XAS analyses of metal derivatives of designed peptides. The scaffolding concept should be extendable to other bridged metal assemblies. 相似文献
557.
Christopher J. Hanlon Kristin A. Arnold Isaura Delgado George W. Gokel 《Journal of inclusion phenomena and macrocyclic chemistry》1989,7(4):437-442
The first example of a lariat ether containing a sulfur sidearm donor is reported here along with a comparison of cation binding strengths to Na+ and K+. The binding strength differs remarkably little from analogs completely lacking a sidearm donor group and similar results are observed for the novel sulfoxide analog. 相似文献
558.
Kristin Schröder Bianca Bitterlich Feyissa Gadissa Gelalcha Matthias Beller 《Tetrahedron letters》2007,48(36):6339-6342
A new selective and easily manageable epoxidation method is presented using an inexpensive and efficient FeCl3·6H2O and imidazole derivatives as catalysts. Aqueous hydrogen peroxide as an environmentally benign oxidant is utilized. This novel Fe/imidazole system gives moderate to excellent yields toward aromatic mono-, di-, and tri-substituted olefins. 相似文献
559.
Use of the Boltzmann equation to simulate lattice gas automata 总被引:1,自引:0,他引:1
560.
Observation of stochastic resonance in a ring laser 总被引:3,自引:0,他引:3