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71.
Dr. Masato Ohashi Ryohei Doi Prof. Dr. Sensuke Ogoshi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(7):2040-2048
This report describes the first Pd0‐catalyzed cross‐coupling of hexafluorobenzene (C6F6) with diarylzinc compounds to give a variety of pentafluorophenyl arenes. This reaction could be applied to other perfluoroarenes, such as octafluorotoluene, pentafluoropyridine, and perfluoronaphthalene, to give the corresponding polyfluorinated coupling products. The optimal ligand in this catalytic reaction was PCy3, and lithium iodide was indispensable as an additive for the coupling reaction. One of the roles of lithium iodide in this catalytic reaction was to promote the oxidative addition of one C?F bond of C6F6 to palladium. Stoichiometric reactions revealed that an expected oxidative‐addition product, trans‐[Pd(C6F5)I(PCy3)2], generated from the reaction of [Pd(PCy3)2] with C6F6 in the presence of lithium iodide, was not involved in the catalytic cycle. Instead, a transient three‐coordinate, monophosphine‐ligated species, [Pd(C6F5)I(PCy3)], emerged as a potential intermediate in the catalytic cycle. Therefore, we isolated a novel PdII complex, [Pd(C6F5)I(PCy3)(py)], in which pyridine (py) acted as a labile ligand to generate the transient species. In fact, in the presence of lithium iodide, this PdII complex was found to react smoothly with diphenylzinc to give the desired pentafluorophenyl benzene, whereas the same reaction conducted in the absence of lithium iodide resulted in a decreased yield of pentafluorophenyl benzene, which indicated that the other role of lithium iodide was to enhance the reactivity of the organozinc species during the transmetalation step. 相似文献
72.
73.
A new method for constructing the polycyclic skeleton of psiguadial B (1), a meroterpenoid isolated from an evergreen shrub of Myrtaceae, was developed. The terpenoid substructure of 1 was constructed on the basis of a cascade double cyclization reaction of an alkyne dicobalt complex, which afforded the bicyclo[4.3.1]decane derivative having a benzyl group with the correct configuration. The substituted aromatic ring was introduced to the bridgehead position of the intermediate, and bromination under radical conditions followed by intramolecular cyclization reaction resulted in formation of the benzopyran moiety in a stereoselective manner. 相似文献
74.
Kamo T Kasahara R Abe S Hirota M Sugano M Yamaya H Hiradate S Fujii Y 《Natural product research》2010,24(17):1637-1642
The 13C labels of [13C]carbon dioxide and D-[13C?]glucose were incorporated into cyanamide (NH?CN) when they were administered to Vicia villosa subsp. varia shoots. In contrast, the administration of sodium [2,3-13C?]pyruvate did not affect the relative area of the [M + 1]+ ion of cyanamide in the gas chromatography-mass spectrometry analysis. [2,3-13C?]pyruvate was incorporated into organic acids that are part of the citric acid cycle, such as succinate and fumarate, confirming that the shoots absorbed and metabolised it. These observations demonstrated that the carbon atom of cyanamide is derived from any of the carbohydrates that are present upstream of pyruvate in the metabolic pathway. 相似文献
75.
We show a Lagrange-type duality theorem for a DC programming problem, which is a generalization of previous results by J.-E. Martínez-Legaz, M. Volle [5] and Y. Fujiwara, D. Kuroiwa [1] when all constraint functions are real-valued. To the purpose, we decompose the DC programming problem into certain infinite convex programming problems. 相似文献
76.
In this paper, we introduce a valuation model of callable warrants under a setting of the optimal stopping problem between the holder (investor) and the issuer (firm). A warrant is the right to purchase new shares at a predetermined price. When the new stocks are issued, the value of the stock is diluted. We consider the model taking the dilution into account. After identifying optimal policies for the issuer and the investor, we explore the analytical properties of the optimal exercise and call boundaries for the holder and the issuer, respectively. Furthermore, the value of such a callable warrant and the optimal critical prices are examined numerically using the binomial method. 相似文献
77.
Journal of Solid State Electrochemistry - Lithium-sulfur batteries (LSBs) are considered to be one of the most promising candidates for becoming the post-lithium-ion battery technology, which would... 相似文献
78.
Hisayasu Ishibashi Dr. Manuel Rondelli Hiroki Shudo Prof. Dr. Takehisa Maekawa Prof. Dr. Hideto Ito Prof. Dr. Kiichi Mizukami Prof. Dr. Nobuo Kimizuka Prof. Dr. Akiko Yagi Prof. Dr. Kenichiro Itami 《Angewandte Chemie (International ed. in English)》2023,62(44):e202310613
The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2′-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C−H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions. 相似文献
79.
E Makino N Iwasaki N Yagi T Ohashi H Kato Y Ito H Azuma 《Chemical & pharmaceutical bulletin》1990,38(1):201-207
Various pyrazine derivatives were synthesized and their antiallergic activity was examined. The inhibitory activity on allergic histamine release of the compounds bearing a 5-tetrazolyl group was more potent than that of the corresponding carboxyl derivatives. The introduction of -CONH- or -NHCO- between the pyrazine ring and the 5-tetrazolyl group as a spacer greatly enhanced the activity. N-(1H-Tetrazol-5-yl)-2-pyrazinecarboxamide (I-3) was estimated to exhibit nearly the same potency as disodium cromoglycate (DSCG). The structure-activity relationship among various derivatives modified by introducing some substituents onto the 3-, 5- or 6-position of the pyrazine ring of I-3 was investigated. The activity remained unchanged or was reduced when such substituents as methyl, chloro, methoxy, methylamino and dimethylamino were introduced at the 3- or 5-position. In contrast, 6-substitution with various alkylamino groups more or less increased the activity. Among them, the 6-dimethylamino (I-17c) and 6-(1-pyrrolidinyl) (I-34) derivative were proved to be most potent. The IC50 values (concentration which produces 50% inhibition of the allergic histamine release) of I-17c and I-34 were determined to be 4.7 x 10(-10) and 4.6 x 10(-10) M, respectively. These two compounds produced a potent inhibitory activity on passive cutaneous anaphylaxis (PCA) in rat, not only by the intravenous route (ED50 = 0.0096 mg/kg for both compounds) but also by the oral route (ED50 = 0.19 and 0.18 mg/kg, respectively). On the other hand, when the pyrazine ring of some representative compounds was replaced with a pyridine ring, the inhibitory activity on histamine release was significantly reduced. 相似文献
80.
A quasi-degenerate perturbation method with vibrational self-consistent field (VSCF) reference wavefunction is developed. It simultaneously accounts for strong anharmonic mode-mode coupling among a few states (static correlation) by a configuration interaction theory and for weak coupling with a vast number of the other states (dynamic correlation) by a perturbation theory. A general formula is derived based on the van Vleck perturbation theory. An algorithm that selects a compact set of the most important VSCF configurations which contribute to the static correlation is proposed and a scheme to limit the number of configurations considered for dynamic correlation is also implemented. This method reproduces the vibrational frequencies of CO2 and H2CO that are subject to the strongest anharmonic mode-mode coupling within 10 cm(-1) of vibrational configuration interaction results in a computational expense reduced by a factor of one to two orders of magnitude. The method also reproduces the infrared absorption of C6H6 in the CH stretching (nu12) frequency region, in which combination tones nu13nu16 and nu2nu13nu18 appear on account of an intensity borrowing from nu12via the anharmonic coupling. 相似文献