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排序方式: 共有216条查询结果,搜索用时 31 毫秒
1.
Dr. Nozomi Mihara Dr. Yasuyuki Yamada Dr. Hikaru Takaya Prof. Yasutaka Kitagawa Dr. Kazunobu Igawa Prof. Katsuhiko Tomooka Prof. Hiroshi Fujii Prof. Kentaro Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(13):3369-3375
Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high-valent oxo species of a nitrido-bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido-bridged dinuclear iron complex of porphyrin-phthalocyanine heterodimer 3 5+, which is connected through a fourfold rotaxane, was prepared. Heterodimer 3 5+ catalyzed ethane oxidation in the presence of H2O2 at a relatively low temperature. The site-selective complexation of 3 5+ with an additional anionic porphyrin (TPPS4−) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post-synthetic modification of 3 5+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido-bridged iron phthalocyanine dimer, which is the most potent iron-oxo-based molecular catalyst for light-alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4− to 3 5+ enhanced the catalytic activity. 相似文献
2.
Takaya Y Kikuchi H Terui Y Komiya J Furukawa KI Seya K Motomura S Ito A Oshima Y 《The Journal of organic chemistry》2000,65(4):985-989
For the elucidation of the diversity of secondary metabolites of Dictyostelium cellular slime molds, we investigate the constituent of three species of slime molds. From the methanol extract of their fruit bodies, we obtained three novel compounds, dictyopyrone A (1) and B (2) from D. discoideum and D. rhizoposium and dictyopyrone C (3) from D. longosporum. They possess a unique alpha-pyrone moiety with a side chain at the C-3 position. Their relative structures were elucidated by spectral means, and the absolute configuration was confirmed by asymmetric synthesis of 1. Since these compounds were obtained from different species of Dictyostelium slime molds, they may be a type of compound common to this genus. 相似文献
3.
Kikuchi H Saito Y Komiya J Takaya Y Honma S Nakahata N Ito A Oshima Y 《The Journal of organic chemistry》2001,66(21):6982-6987
We investigated the constituents of Dictyostelium discoideum to clarify the diversity of secondary metabolites of Dictyostelium cellular slime molds and to explore biologically active substances that could be useful in the development of novel drugs. From a methanol extract of the multicellular fruit body of D. discoideum, we isolated two novel amino sugar analogues, furanodictine A (1) and B (2). They are the first 3,6-anhydrosugars to be isolated from natural sources. Their relative structures were elucidated by spectral means, and the absolute configurations were confirmed by asymmetric syntheses of 1 and 2. These furanodictines potently induce neuronal differentiation of rat pheochromocytoma (PC-12) cells. 相似文献
4.
Takaya Matsumoto 《Catalysis Surveys from Asia》2007,11(1-2):31-48
In this article, two kinds of our transition metal-catalyzed olefin arylations are summarized and discussed. The first one
is Ir-catalyzed novel anti-Markovnikov hydroarylation of olefins with benzene. Using this reaction catalyzed by [Ir(μ-acac-O,O′,C3)(acac-O,O′)(acac-C3)]2 (acac = acetylacetonato), 1, straight-chain alkylarenes, which were not obtainable by the conventional Friedel-Crafts aromatic alkylation with olefins,
were able to be successfully synthesized directly from arenes and olefins with the higher selectivity than that of branched
alkylarenes. This is the first efficient catalyst which shows the desirable high regioselectivity. The reaction of benzene
with propylene gave n-propylbenzene and cumene in 61% and 39% selectivities, respectively, and the reaction of benzene and styrene afforded 1,2-diphenylethane
in 98% selectivity. The reaction of alkylarene and olefin showed meta and para orientations. A wide range of olefins and arenes
can be employed for the synthesis of alkylarenes. The mechanism of the reaction involves C–H bond activation of benzene by
Ir center to form Ir–phenyl species. The second reaction is Rh-catalyzed oxidative arylation of ethylene with benzene to directly
produce styrene, namely one-step synthesis of styrene. The reaction of benzene with ethylene catalyzed by Rh(ppy)2(OAc) (ppyH = 2-phenylpyridine, OAc = acetate), 3 with Cu oxidizing agent gave styrene and vinyl acetate in 77% and 23% selectivities, respectively, in contrast to those by
Pd(OAc)2, 47% of styrene and 53% of vinyl acetate. The mechanism of the reaction involves Rh-mediated C–H bond activation of benzene,
which appears to be a rate-determining step. Furthermore, Rh complexes in a Rh(I) oxidation state at the beginning of the
reaction work as catalysts for the reaction by addition of acacH and O2 without any oxidizing agent, like Cu salt. 相似文献
5.
Takaya Hisano 《Tetrahedron letters》2005,46(37):6293-6295
Highly regioselective transformation of acyclic α,α′-alkenediols and their corresponding diacetates to monoacetates using lipase was accomplished. The acetylation of the α,α′-alkenediol regioselectively gave (E)-monoacetate, whereas the (Z)-monoacetate were obtained by hydrolysis of the α,α′-diacetate. 相似文献
6.
7.
8.
Takashi Kitayama Maki Nakahira Kae Yamasaki Hiromi Inoue Chika Imada Yuji Yonekura Masataka Awata Hikaru Takaya Yasushi Kawai Kohta Ohnishi Akira Murakami 《Tetrahedron》2013
Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through SN2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC50 against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC50: 0.24 μM). 相似文献
9.
Dilute aqueous solutions of dodecyl-benzenesulfonic acid sodium salt (DBS-Na) and polyoxyethylenenonylphenyl ethers (PONPEs) were ultrasonically atomized. The surfactants were concentrated in collected mist droplets. The enrichment ratio increased with decreasing surfactant concentration. Depending on the surfactant’s molecular weight and affinity to water, different enrichment ratio was observed in the range of low feed concentrations. For anionic surfactant, DBS-Na, the enrichment ratio was significantly improved by KCl addition and a peak appeared on the plot of the ratio against KCl concentration. Addition of NaCl or CaCl2 · 2H2O to the surfactant solution also enhanced the enrichment ratio; however, the effect was relatively small. Such behaviors of the ratio were interpreted as enhanced interfacial adsorption of the surfactant and a lack of supply of surfactant monomers from liquid bulk because of slow breaking of surfactant micelles. Time required for collecting an amount of mist was also observed. Among the three salt systems, the time for KCl system was twice as long as others. This fact suggested that the formation of smaller droplets in KCl system. 相似文献
10.
[reaction: see text] A concise method for the preparation of 1-acyl-4-alkoxy- or 1-acyl-4-alkylsulfanylnaphthalenes has been developed by the reaction of o-ethynylbenzoates or benzothioates with vinyl ethers, in the presence of a catalytic amount of PtCl(2). It is proposed that the reaction proceeds through [3 + 2]-cycloaddition of the platinum-containing carbonyl ylides followed by 1,2-alkyl migration. 相似文献