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81.
[reaction: see text] Indium-mediated allenylation of alpha,beta-unsaturated ketones in the presence of tert-butyldimethylsilyl triflate and dimethyl sulfide gives 6-siloxy-1,2,5-trienes, which undergo W(CO)(5)(L)-catalyzed 5-endo cyclization to give the corresponding cyclopentene derivatives in good yield. Furthermore, this novel W(CO)(5)(L)-catalyzed cyclization of allenyl silyl enol ethers proceeds in a 6-endo manner when 5-siloxy-1,2,5-trienes are employed as a substrate. In these reactions, effective electrophilic activation of allenyl compounds for attack by silyl enol ethers is achieved using a catalytic amount of W(CO)(6). 相似文献
82.
Synthesis and Magnetic Properties of (Pyrrolidin‐1‐oxyl)–(Nitronyl Nitroxide)/(Iminonitroxide)‐Dyads
Haruki Tsujimoto Shuichi Suzuki Masatoshi Kozaki Daisuke Shiomi Kazunobu Sato Takeji Takui Keiji Okada 《化学:亚洲杂志》2019,14(10):1801-1806
Unlike extensively studied diradicals linked by π‐conjugated systems, only a few studies have investigated weakly coupled diradicals linked by an sp3 carbon atom. Herein, we prepared pyrrolidin‐1‐oxyl–(nitronyl nitroxide)‐dyad 5 and pyrrolidin‐1‐oxyl–iminonitroxide‐dyad 6 . From the observed temperature dependence of the magnetic susceptibility, 5 and 6 were determined to be in singlet ground states with 2Jintra/kB=?35.2 K and ?13.6 K, respectively. From these results and theoretical calculations of related diradicals, the spin‐polarization model counting the small spin density of the sp3 carbon atom could be used as a spin‐prediction model. 相似文献
83.
Yuichiro Nishizawa Shusuke Matsui Kenji Urayama Takuma Kureha Mitsuhiro Shibayama Takayuki Uchihashi Daisuke Suzuki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(26):8901-8905
Despite the tremendous efforts devoted to the structural analysis of hydrogel microspheres (microgels), many details of their structures remain unclear. Reported in this study is that thermoresponsive poly(N‐isopropyl acrylamide) (pNIPAm)‐based microgels exhibit not only the widely accepted core–shell structures, but also inhomogeneous decanano‐sized non‐thermoresponsive spherical domains within their dense cores, which was revealed by temperature‐controlled high‐speed atomic force microscopy (TC‐HS‐AFM). Based on a series of experiments, it is concluded that the non‐thermoresponsive domains are characteristic for pNIPAm microgels synthesized by precipitation polymerization, and plausible structures for microgels prepared by other polymerization techniques are proposed. 相似文献
84.
Vapor–liquid equilibria and saturated density for carbon dioxide + tetrahydrofuran mixtures at high pressures were measured by the analytical method at the temperatures 298.15 and 313.15 K. The experimental apparatus equipped with three Anton Paar DMA 512S vibrating tube density meters was previously developed for measuring vapor–liquid–liquid equilibrium at high pressures. The equilibrium composition and saturated density of each phase were determined by gas chromatograph and vibrating tube density meters, respectively. The bubble point pressure at the temperature 313.15 K was further measured by the synthetic method. The experimental data were correlated with Soave–Redlich–Kwong (SRK) equation of state and the pseudocubic equation of state. 相似文献
85.
Yoshimi Sueishi Atsushi Miyata Daisuke Yoshioka Masato Kamibayashi Yashige Kotake 《Journal of inclusion phenomena and macrocyclic chemistry》2010,66(3-4):357-364
The effect of CD-inclusion on spin-trapping rates and spin-adduct decay rates for sulfur trioxide radical anion (SO3 ??) was investigated. SO3 ?? radical was produced with UV photolysis of sodium sulfite in basic aqueous solution, and spin-trapped with various spin traps, i.e., PBN (α-phenyl-N-t-butylnitrone), DMPO (5,5-dimethyl pyrroline-1-oxide), and three other phosphoryl DMPO-type spin traps. A modified β-CD, 6-O-α-d-glucosyl-β-cyclodextrin (G-β-CD) having better inclusion properties than β-CD, was employed. Upon adding excess G-β-CD, decay rates of SO3 ?? radical adducts significantly decreased in most spin traps. Half-lives of SO3 ?? radical adducts of phosphoryl spin traps were one to two orders of magnitude longer than that of PBN or DMPO, and the G-β-CD addition further extended the half-life time. The spin traps containing phosphoryl-group all showed higher SO3 ?? trapping rates than those of PBN and DMPO, but two phosphoryl spin traps achieved slower trapping rates by G-β-CD addition. In addition, the structures of CD-inclusion complexes of spin traps were established by means of 1D and 2D NMR measurements. Based on the results, the influences of inclusion on the spin-trapping rate processes and spin-adduct stabilizations were discussed. We conclude that substituents in DMPO-type spin traps may be modified to provide best spin-trapping capabilities in the presence or absence of CD. 相似文献
86.
Secondary 2-thiophenecarboxamides efficiently undergo unique triarylation accompanied by formal decarbamoylation under palladium catalysis. 3-Substituted thiophenes, especially having an electron-withdrawing group, can also be triarylated. 相似文献
87.
88.
Miura T Goto K Waragai H Matsumoto H Hirose Y Ohmae M Ishida HK Satoh A Inazu T 《The Journal of organic chemistry》2004,69(16):5348-5353
The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS. 相似文献
89.
Morita Y Nishida S Kobayashi T Fukui K Sato K Shiomi D Takui T Nakasuji K 《Organic letters》2004,6(9):1397-1400
[structure: see text] A bowl-shaped neutral radical with a corannulene system has been designed and synthesized for the first time as a stable solid in air. An unequivocal characterization of the electronic properties of the radical shows that an appreciable amount of spin delocalization extends onto the corannulene unit's curved surface. 相似文献
90.
Suzuki N Aihara N Takahara H Watanabe T Iwasaki M Saburi M Hashizume D Chihara T 《Journal of the American Chemical Society》2004,126(1):60-61
Five-membered metallacyclic alkynes that have no substituents adjacent to the triple bond have been synthesized, isolated, and structurally characterized. Zirconocene dichlorides, Cp'2ZrCl2 (Cp' = C5H5, C5H4-t-Bu), reacted with 1,4-dichlorobut-2-yne in the presence of magnesium to give 1-zirconacyclopent-3-yne compounds (5 (a) Cp' = C5H5, (b) Cp' = C5H4-t-Bu) that have a -CH2CCCH2- moiety in good yields. They are stable enough to be isolated in a pure form, despite the absence of substituents. 5a reacted with an equimolar amount of Cp2Zr(but-1-ene)(PMe3) to produce a bimetallic complex in which the zirconacyclopentyne coordinates to the other zirconocene moiety as an alkyne. 相似文献