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41.
John V. Tate William N. Tinnerman Vito Jurevics Harold Jeskey Edward R. Biehl 《Journal of heterocyclic chemistry》1986,23(1):9-11
The acidity of 5-benzylbarbituric acid and a series of 5-substituted benzylbarbituric acids has been determined in 50% ethanol/water and they were found to be more acidic than barbituric acid. The pKas of these derivatives obey Hammett's equation indicating that their acidity is affected by substituents in the same manner as the benzoic acid ionization constants. A synthesis of these acids is described. 相似文献
42.
Shimizu K Suzuki H Hayashi E Kodama T Tsuchiya Y Hagiwara H Kitayama Y 《Chemical communications (Cambridge, England)》2002,(10):1068-1069
Direct 1,4-conjugate addition of naked aldehydes to vinylketones is catalysed effectively by N-methyl-3-aminopropylated FSM-16 mesoporous silica, which can be regarded as a novel heterogeneous catalysis for a practical C-C bond formation reaction. 相似文献
43.
Some of the ascidians belonging to the suborder Phlebobranchia accumulate vanadium ion efficiently from seawater. Clarification of the mechanism of this surprisingly efficient metal-accumulation system is desirable. Two mutually similar vanadium-binding proteins (vanabin1 and vanabin2) have recently been isolated from a vanadium-rich ascidian Ascidia sydneiensis samea. In this study, the vanadium-binding properties of vanabin2 have been investigated by X-band CW EPR and pulsed EPR spectroscopy. CW EPR spectra of samples containing various ratios of VO2+ and vanabin2 invariably exhibited a usual mononuclear-type VO2+ EPR signal with the intensity dependent on the ratio [vanabin]/[V]. EPR titration has shown that vanabin2 can bind up to approximately 23.9 vanadium ions per one molecule, almost all of which ( approximately 84%) are in a mononuclear VO2+ state as estimated by EPR quantitation. Electron spin-echo envelope modulation (ESEEM) spectra of VO-vanabin2 exhibited reasonably intense peaks attributable to amine nitrogen. This is consistent with the fact that vanabin2 is a lysine-rich protein (14 lysines out of 91 amino acids). The present study reveals the uniqueness of vanabin2, which can bind a large number of metal ions in a mononuclear fashion in contrast to the situation for ferritin and metallothionein. 相似文献
44.
Konno T Usami M Hirotsu M Yoshimura T Kawamoto T 《Chemical communications (Cambridge, England)》2004,(20):2296-2297
Treatment of [Ni(L)][L =((-)SCH(2)CH(2)NH[double bond, length as m-dash]C(CH(3))-)(2)] with Ag(+) in water gave a pinwheel-like S-bridged Ni(II)(3)Ag(I)(2) structure in [Ag(2)[Ni(L)](3)](2+), which further reacted with [Ni(L)] to produce a Ni(II)(4)Ag(I)(2) structure in [Ag(2)[Ni(L)](4)](2+) and a Ni(II)(7)Ag(I)(4) structure in [Ag(4)[Ni(L)](7)](4+). 相似文献
45.
Bis-crown ethers in which the benzo-15-crown-5 units were linked to 1,1′-positions of metallocene (M = Fe or Ru) with amide, ester, or ? C? C? bonds were synthesized. Complexing ability of the compounds with alkali, alkali earth, and transition metal cations were measured by the solvent extraction method. The results showed that these crown ethers had high affinity toward alkali metal cations (Li+, Na+, K+, and Rb+) and heavy-metal cations (Ag+ and Tl+). The difference of complexing ability for metal cations between ferrocene and ruthenocene derivatives could not be detected significantly. The extractability of metallocene-bis-crown ethers for metal cations was more larger than that of the corresponding mono-crown ethers, and irregular increments of extractability were explained by assuming the existence of a mixture of 1:1 and 2:1 complexes. 相似文献
46.
Nabeshima T Saiki T Iwabuchi J Akine S 《Journal of the American Chemical Society》2005,127(15):5507-5511
Synthesis and binding behavior of a novel multi-responsive host 1, in which two esters, two polyether moieties, two urea sites, and two bipyridine units as ion binding sites are arranged on the calix[4]arene skeleton, is reported. 1 recognizes Na(+) and Ag(+) simultaneously and quantitatively and captures an anionic guest. The ability of 1 to recognize anions, including CF(3)SO(3)(-) and BF(4)(-), remarkably increases in a stepwise manner using Na(+) and Ag(+) as effectors. The enhancement of the K(a) eventually reaches factors of 1500 and 2000 for NO(3)(-) and CF(3)SO(3)(-), respectively, in the presence of both Na(+) and Ag(+), compared to the free 1. The regulation of binding of multiple ligands may be applicable to multistep cascade systems for the amplification of molecular events, and further studies in this field could provide insight applicable to more advanced molecular devices. 相似文献
47.
Tatsuya Shono Tetsuya Miyamoto Masamichi Mizukami Hiroshi Hamaguchi 《Tetrahedron letters》1981,22(25):2385-2388
Electrochemical reduction of immonium salts in the presence of bromobenzylbromide derivatives gave 1-(bromobenzyl)-isoquinoline derivatives in moderate yields. This reaction is useful in the synthesis of several natural alkaloids as exemplified in the synthesis of Cularine. 相似文献
48.
Toshiharu Okui Yuriko Saito Tatsuya Okubo Masayoshi Sadakata 《Journal of Sol-Gel Science and Technology》1995,5(2):127-134
Selective gas permeation of porous organic/inorganic hybrid membranes via sol-gel route and its thermal stability are described. Separation performance of the hybrid membrane was improved compared with porous membranes governed by the Knudsen flow, and gas permeability was still much higher than that through nonporous membranes. Additionally, it was shown that these membranes were applicable at higher temperatures than organic membranes.SEM observation demonstrated that the thin membrane was crack-free. Nitrogen physisorption isotherms showed the pore size was in the range of nanometers. Gas permeability through this membrane including phenyl group was in the range of 10–8 [cc(STP) cm/(cm2 s cmHg)] at 25°C. The ratios of O2/N2 and CO2/N2 were 1.5 and 6.0, respectively, showing the permeation was not governed by the Knudsen flow. The permeability decreased as the temperature increased. Furthermore, the specific affinity between gas molecules and surface was observed not only in the permeation data of the hybrid membranes but in the physisorption data. These results suggested that the gas permeation through the hybrid membrane was governed by the surface flow mechanism.Thermal analysis indicated that these functional groups were still stable at higher temperatures. The phenyl group especially remained undamaged even at 400°C. 相似文献
49.
Lewis K. Panell Henry M. Fales John P. Scovill Daniel L. Klayman Douglas X. West Ramon L. Tate 《Transition Metal Chemistry》1985,10(4):141-147
Summary Californium-252 plasma desorption mass spectra were recorded for complexes of the anions of various thio-and seleno-semicarbazones of 3-acetylpyridines(1–4) with the transition metal ions iron(III) and cobalt(II). Positive ion spectra gave clear evidence of the cation present and fragmentation with loss of ligands or parts of ligands was straightforward. Negative ion spectra likewise provided evidence of the intact anion except with tetracoordinate metal halide systems [MX4]– which lost one or more halide atoms. Evidence of fragmentation of the ligand and recombination of the fragments with the metal ion was also observed in the negative ion mode. Spectra were used to revise the structure of a complex previously reported as [FeLCl2](1) to [FeL2]+[FeCl4]–. 相似文献
50.
Raquel Simancas Anand Chokkalingam Shanmugam P. Elangovan Zhendong Liu Tsuneji Sano Kenta Iyoki Toru Wakihara Tatsuya Okubo 《Chemical science》2021,12(22):7677
Zeolites have been successfully employed in many catalytic reactions of industrial relevance. The severe conditions required in some processes, where high temperatures are frequently combined with the presence of steam, highlight the need of considering the evolution of the catalyst structure during the reaction. This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites.This review attempts to summarize the recently developed strategies to improve the hydrothermal framework stability of zeolites. 相似文献