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111.
James C. W. Chien Takashi Nozaki 《Journal of polymer science. Part A, Polymer chemistry》1993,31(1):227-237
Homopolymerization of ethylene and 1-hexene and their copolymerizations were compared to investigate the influence of α-olefin on the enhancement of ethylene polymerization rate (Rp), which is often referred to as the “comonomer” effect. With the two homogeneous Ziegler–Natta catalysts, Et[Ind]2ZrCl2/MAO and (π-C5H5)2ZrCl2/MAO (MAO = methylaluminoxane), hexene causes reduction of Rp—in other words a negative “comonomer” effect. In the case of the high activity MgCl2 supported TiCl3 catalysts there is a slight positive “comonomer” effect; the Rp increases by 25 to 70% with the addition of 15 mol % of hexene. The “comonomer” effects in there catalyst systems are much smaller than that observed for the classical TiCl3 catalyst. © 1993 John Wiley & Sons, Inc. 相似文献
112.
Jun-ichi Hibino Seijiro Matsubara Yoshitomi Morizawa Koichiro Oshima Hitosi Nozaki 《Tetrahedron letters》1984,25(20):2151-2154
The reaction of terminal acetylenes with Bu3SnMgMe, Bu3SnA1Et2, or (Bu3Sn)2Zn in the presence of various transition-metal catalysts provides vinylstannanes in good yields. Whereas copper catalysed stannylmagnesation of 4-benzyloxy-1-butyne gives (E)-4-benzyloxy-1-tributylstannyl-1-butene exclusively, palladium catalysed stannylzincation affords 4-benzyloxy-2-tributylstannyl-1-butene preferentially. 相似文献
113.
The novel, bridged bromocycloheptatriene (4) is obtained by the thermolysis of a tricyclo[6.4.1.01,8]tridecane derivative (6), and the observed anti stereochemistry of the Br atom on C(13) is accounted for by assuming the suprafacial [1,5] hydrogen shift in the intermediate 7. The mother hydrocarbon (8) and syn-methyltropylidene (9), as well as tropone (10), are derived from 4, and the structures of these products are examined spectrometrically. The covalent CBr bond of 4 remains intact under various reaction conditions of nucleophilic substitution, and this is ascribed to the conformational rigidity constrained by the short hexamethylene bridge. The attempted transformation of 4 or 10 to the corresponding tropyllium ion 12 or 14 fails to success and this is again attributed to the bridge effect. 相似文献
114.
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116.
Treatment of lithium trialkylalkynylborates with acetyl chloride gave 2-oxa-3-borolenes (2). The enol borinates were oxidized by Jones reagent to highly substituted α,β-unsaturated ketones (4). The stability of 2 is ascribed to the steric hindrance of the B-alkyl groups and to the resonance contribution of the mesomeric structure 3. 相似文献
117.
Shiratori H Ohno T Nozaki K Yamazaki I Nishimura Y Osuka A 《The Journal of organic chemistry》2000,65(25):8747-8757
Three sets of dyads, in which a zinc-porphyrin (ZP) electron donor is connected to an aromatic diimide electron acceptor,either pyromellitimide (PI) or naphthalene-1,8:4,5-tetracarboxylic acid diimide (NI), via a boronate-ester bridge, a piperidine bridge, and a 1,3-dioxolane bridge, respectively, were prepared for the purpose of control of intramolecular electron transfer (ET) by acid-base reactions at the connecting bridge. Boronate-ester bridge is a Lewis acidic site and confers a chance to regulate intramolecular ET reaction upon base coordination. This has been demonstrated by suppression of photoinduced ET from ZP to PI or NI in highly electron-pair donating solvents or upon addition of a fluoride anion. To extend this strategy to control of ET-path selectivity, we prepared triad 18, which consists of a ZP donor bearing NI and PI acceptors at similar distances through a boronate-ester bridge and an acetal bridge, respectively. Photoexcitation of 18 in a free form led to intramolecular ET from (1)()ZP preferentially to NI, but the ET path was completely switched toward PI in F(-)-coordinated form without a serious drop in the rate, constituting a novel ET-switching molecular system. 相似文献
118.
Trialkylaluminium-mediated alkylation of enol phosphates under the CO bond cleavage is performed stereospecifically in the presence of a catalytic amount of Pd(PPh3)4. Alkenylation and alkynylation are also described. 相似文献
119.
T. Nozaki T. Kobayashi M. Shirai 《Journal of Radioanalytical and Nuclear Chemistry》1996,203(1):151-160
Carrier- and salt-free42K milked from an42Ar–42K generator was utilized for isotope dilution analysis of potassium in ultra-pure water. Potassium in the sample marked with the42K was shown to be concentrated easily 60 times by crown-ether extraction and acid back-extraction to be determined by atomic absorption spectrophotometry. The same extractions proved to be effective for removing the reagent blank. Cerenkov radiation counting was often suitable for42K measurement. The42K was used also for studying the interaction of ultra-low concentrations of potassium with vessel walls. 相似文献
120.
Kenji Sakamaki Hiroaki Wada Hiroshi Nozaki Yoshichika Onuki Maki Kawai 《Molecular Crystals and Liquid Crystals》2013,570(2):99-104
Abstract Evidence for bulk superconductivity in Nb2SC0.90 carbosulfide is presented. Diamagnetic volume fraction of Nb2SC0.90 was precisely determined with low applied magnetic fields which were corrected by 6N lead rod as an internal standard. Based on magnetic field dependence of magnetic moment at several constant temperature's below TC = 5 K, Nb2SC0.90 is found to be a type II superconductor with relatively high H C2 and low HC1. 相似文献