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81.
A new method for installation of aryl and alkenyl groups onto a cyclopentene ring and synthesis of prostaglandins 总被引:1,自引:0,他引:1
Kobayashi Y Murugesh MG Nakano M Takahisa E Usmani SB Ainai T 《The Journal of organic chemistry》2002,67(20):7110-7123
To construct a new strategy for synthesis of cyclopentanoids, the transition metal-catalyzed coupling reaction of cis 4-cyclopentene-1,3-diol monoacetate 1 with hard nucleophiles, R(T)-m, was investigated (eq 1 in Chart 1). Although preliminary experiments using PhZnCl, PhSnMe(3), [Ph-B(Me)(OCH(Me)CH(Me)O)]-Li(+) (6a) (derived from boronate ester 4a (R(T) = Ph) and MeLi) in the presence of a palladium or a nickel catalyst resulted in production of unidentified compounds, enone 16, and/or ketone 17 or recovery of 1, a new borate 5a (derived from 4a and n-BuLi) in the presence of a nickel catalyst (NiCl(2)(PPh(3))(2)) in THF at room temperature furnished the trans coupling products 2a (R(T) = Ph) and 3a (R(T) = Ph) in high combined yield, but with a low product ratio of 0.9:1. The ratio was improved to 13:1 by addition of t-BuCN and NaI into the reaction mixture. This is the first successful example of the reaction of 1 with a hard nucleophile, and the increase in the ratio, realized with the additives, is unprecedented. This reagent system (borate 5 (1.2-1.8 equiv), NiCl(2)(PPh(3))(2) (5-10 mol %), t-BuCN (2-5 equiv), NaI (0.5-1 equiv), THF, room temp) was further investigated with aryl borates 5b-g and alkenyl borates 5h-n to afford 2b-n in moderate to good yields (52-89%) with practically acceptable levels of the regioselectivity (5 approximately 21:1), thus establishing the generality of the reaction (Table 2, eqs 6 and 7). Starting with the products of the coupling reaction, syntheses of the prostaglandin intermediates 13 and 14 (for 11-deoxy-PGE(2) and PGA(2)) and Delta(7)-PGA(1) methyl ester (15) were accomplished efficiently. During these investigations, LDA, LiCA, and LHMDS were found to be equally efficient bases for aldol reaction at the alpha' (alpha prime) position of cyclopentenones 39, 40, and 41 (Table 3). 相似文献
82.
Takahisa Iida Toshio Sugizaki Toshifumi Kageyama Osamu Moriya 《Journal of polymer science. Part A, Polymer chemistry》1998,36(4):655-663
Tributylstannylated silicic acid (TBSA), which was regarded as a protected polymeric silanol against self-condensation to give silica gel, was newly prepared from the reaction of water glass (WG) and bis(tributyltin) oxide (TBO). The ratios of Si/Sn contained in TBSA were determined by gravimetric analysis to be in the range of 2–3. The gelation of TBSA in usual organic solvents such as hexane, benzene, and dichloromethane was not observed over 3 weeks. In addition, TBSA was shown to be a convenient precursor for the preparations of silica gel modified with organofunctional groups. From the reaction of TBSA with trimethoxysilanes and aromatic alcohols, the silica gels havingorganofunctional groups were obtained with the elimination of a tributyltin group. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 655–663, 1998 相似文献
83.
Manabu Tsumura Takahisa Iwahara Toshifumi Hirose 《Journal of polymer science. Part A, Polymer chemistry》1996,34(15):3155-3161
The polycarbosilanes (PCS) with meta-linkage bending unit ((SINGLE BOND)Me2Si(SINGLE BOND)m(SINGLE BOND)C6H4(SINGLE BOND)Me2Si(SINGLE BOND)CH2CH2(SINGLE BOND)) were successfully synthesized in mild conditions by hydrosilylation in the presence of [Pt{(CH2(DOUBLE BOND)CHSiMe2)2O}2]. The PCS obtained were soluble in various solvents owing to the lowering of the crystallinity. These properties are well compared with those of the PCS [(SINGLE BOND)Me2Si(SINGLE BOND)p(SINGLE BOND)C6H4(SINGLE BOND)Me2Si(SINGLE BOND)CH2CH2(SINGLE BOND)]n. © 1996 John Wiley & Sons, Inc. 相似文献
84.
Stefan Machill Takahisa Shodai Yoji Sakurai Jun-ichi Yamaki 《Journal of Solid State Electrochemistry》1999,3(2):97-103
Tin-based composite oxide materials have received considerable attention as potential anode materials for rechargeable lithium
batteries. In this contribution we present the results of our investigations of the SnOB2O3P2O5 system. We have investigated its electrochemical properties and especially its cycling performance. A focus of our interest
was to explain the structural changes which occur during lithium cycling and their strong dependence on the preparation method.
A part of the SnO component was converted into a very stable metallic phase. In addition, a decrease was observed in capacity
owing to the formation of isolated and inactive tin grains. We also report on structural changes in the B2O3P2O5 matrix.
Received: 2 October 1997 / Accepted: 3 July 1998 相似文献
85.
Takakazu Yamamoto Yukiko Muramatsu Takahisa Shimizu Wataru Yamada 《Macromolecular rapid communications》1998,19(5):263-266
π-Conjugated polymers bearing nitro substituent(s), e.g., poly(aryleneethynylene) (PAE) type polymers and poly(4,8-dinitroanthraquinone-1,5-diyl) P(4,8-NO2-1,5-AQ), show semiconducting properties with electrical conductivities of an order of 10−7 to 10−6 S · cm−1 at room temperature without special oxidation and reduction of the polymer. P(4,8-NO2-1,5-AQ) shows a large shift of phase in alternating current (ac) measurements and a unique magnetism at low temperature. 相似文献
86.
Katsuhiro Nose Takahisa Omata Shinya Otsuka-Yao-Matsuo Hideaki Maeda 《Journal of luminescence》2007,126(1):21-26
The role of organic amines in the colloidal synthesis of CdSe quantum dots (QDs) has been studied. CdSe QDs were synthesized from the source solutions containing 5 vol% of amines having various alkyl chain lengths, stereochemical sizes and electron donation abilities. The role of the additional amines was evaluated on the basis of the photoluminescence (PL) properties such as PL wavelength and intensity of the obtained CdSe QDs. The observed PL spectra were explained by the fact that the amines behaved as capping ligands on the surface of the QDs in the product colloidal solution and complex ligands for cadmium in the source solutions. It was shown that the particle size was controlled by the diffusion process depending on the mass and stereochemical shape of the amines, and the luminescence intensity increased with the increasing electron donation ability and capping density of the amines. 相似文献
87.
Oikawa M Saito T Takahisa K Suga Y Kino K Nakagawa T Tohei T Abe K Ueno H 《Physical review letters》2000,84(11):2338-2341
Out of plane measurements of the angular correlations for the 12C(e, e(')n) reaction have been performed for the first time in the giant resonance region. The cross sections were directly separated into the longitudinal and transverse, longitudinal-transverse, and transverse-transverse components. The cross section at the peak of the giant resonance ( omega = 22.5 MeV) has been found to be almost all longitudinal. It was reproduced by the multipole expansion with E0 and E2 components besides E1. The longitudinal-transverse component might have a maximum around 24 MeV. The transverse-transverse component is very small over the giant resonance. 相似文献
88.
Mizu M Koumoto K Anada T Matsumoto T Numata M Shinkai S Nagasaki T Sakurai K 《Journal of the American Chemical Society》2004,126(27):8372-8373
A beta-(1 --> 3)-d-glucan schizophyllan (SPG) forms a stoichiometric complex with some polynucleotides. This communication describes our attempt to apply the SPG complex to deliver CpG DNA to endosomes to enhance cytokine secretion. To increase cellular uptake, we introduced spermine, arginine-glycine-aspartic acid tripeptide, octaarginine, or cholesterol to the SPG side chain. The chemically modified SPG showed essentially no cytotoxicity. When CpG DNA complex made therefrom was exposed to macrophages, dramatic enhancement in the cytokine secretion was observed. It increased 5-10 times from the naked dose and 100 times from the background. This performance promises that SPG can be an excellent carrier for CpG DNA. 相似文献
89.
It is well known that granular materials are not homogeneous, i.e. the forces between grains are localized in force chains. However, previous work on plant root growth has neglected this variability in granular soils and reported bulk characteristics or used homogeneous media, such as agar, to grow plant roots. In this paper we report the results of pinto bean root growth through a granular system where photoelastic grains are used to visualize and quantify the local forces in the system. Two issues are addressed: how plant roots respond to different levels of force between grains, and how the growing roots alter the force distribution in a granular system. We find that pinto bean roots are less likely to grow between grains as the force between those grains increases and that roots can exert, on average, 110 mN of force on the granular system. However, both of these observations are time-dependent. Both the inter-grain forces as the roots grow and the forces that the roots impart to the system increase in time without observable concomitant geometric changes in root cross-section. 相似文献
90.
Fumio Hosoi Yasushi Aoki Miyuki Hagiwara Hideki Omichi M. Mat. Salleh 《辐射效应与固体损伤》2013,168(1-4):351-354
Abstract Substituting metallic or rare-earth atoms or removing O in the superconductor YBa2Cu3O7 usually has a strong effect on the superconducting properties. We have made extensive XAFS studies on Co, Fe, Ni, Zn, Gd, and Pr substituted materials including some thin film samples. In nearly all cases, significant distortions are found. Although the lattice constant change is small (< 0.05 Å) the local distortions can be significant larger (~ 0.1 to 0.3 Å). The observed large local distortions of the lattice together with a change in the charge distribution at a site indicate that the interior of the unit cell is easily distorted. The correlation of a strong Tc suppression with large local distortions suggests that distortions of the nearby layers must play a significant role in models for superconductivity in high Tc materials. 相似文献