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41.
This article presents a full account of intramolecular vinylic substitution reactions of bromoalkenes having an acetylthio moiety, which give sulfur-containing heterocycles such as dihydrothiophene, tetrahydrothiopyran, and 2-alkylidenethietane derivatives. The reaction pathways of the substitution reactions were investigated by theoretical and experimental studies. 相似文献
42.
Koji Nagahama Kanae Fujiura Shunsuke Enami Tatsuro Ouchi Yuichi Ohya 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6317-6332
Starburst triblock copolymers consisting of 8‐arm poly(ethylene glycol) (8‐arm PEG) and biodegradable poly(L ‐lactide) (PLLA) or its enantiomer poly(D ‐lactide) (PDLA), 8‐arm PEG‐b‐PLLA‐b‐PEG ( Stri‐L ), and 8‐arm PEG‐b‐PDLA‐b‐PEG ( Stri‐D ) were synthesized. An aqueous solution of a 1:1 mixture ( Stri‐Mix ) of Stri‐L and Stri‐D assumed a sol state at room temperature, but instantaneously formed a physically crosslinked hydrogel in response to increasing temperature. The resulting hydrogel exhibited a high‐storage modulus (9.8 kPa) at 37 °C. Interestingly, once formed at the transition temperature, the hydrogel was stable even after cooling below the transition temperature. The hydrogel formation process was irreversible because of the formation of stable stereocomplexes. In aqueous solution, gradual hydrolytic erosion was observed because of degradation of the hydrogel. The combination of rapid temperature‐triggered irreversible hydrogel formation, high‐mechanical strength, and degradation behavior render this polymer mixture system suitable for use in injectable biomedical materials, for example, as a drug delivery system for bioactive reagents or a biodegradable scaffold for tissue engineering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6317–6332, 2008 相似文献
43.
Oxidative Degradation of Aqueous Cresols Induced by Gaseous Plasma with Contact Glow Discharge Electrolysis 总被引:2,自引:0,他引:2
The oxidative degradation of cresols smoothly proceeded toward inorganic end products when a gaseous plasma generated by means
of dc glow discharge was sustained in contact with the surface of aqueous solution containing organic compounds. In order
to get mechanistic insight, the monohydroxylation products from each isomeric cresol were closely examined as primary intermediates
to reveal that the aromatic hydroxylation preferentially occurred at the position para to the hydroxyl group of each starting
material. It was also established that the degradation of cresols strictly followed the first-order rate law. On the basis
of the orientational analysis and the kinetical consideration including the effects of Fe ions added on the reaction rate,
it was concluded that hydroxyl radical, which might result from the homolytic cleavage of water molecules by the action of
plasma, was the most likely reagent responsible for the mineralization of cresols. 相似文献
44.
ArS(ArSSAr)+ (arylbis(arylthio)sulfonium ions), which were generated and accumulated by the electrochemical oxidation of diaryl disulfides (ArSSAr) in CH2Cl2 at −78 °C, reacted with alkenes to give the corresponding diarylthio-substituted compounds in a stereospecific manner in good yields, when the reaction was quenched with a soft nucleophile, such as allylsilanes, ketene silyl acetals, and triethylamine. A mechanism involving the initial formation of an episulfonium ion followed by ring-opening by the attack of ArSSAr has been suggested. The reactions of ArS(ArSSAr)+ with alkynes also took place to give 1,2-diorganothio-substitued alkenes stereoselectively under similar conditions. 相似文献
45.
Katsumi Katoh Shunsuke Ito Yuji Ogata Jun-ichi Kasamatsu Hiroshi Miya Masaaki Yamamoto Yuji Wada 《Journal of Thermal Analysis and Calorimetry》2010,99(1):159-164
In order to prevent the spontaneous ignition of nitrocellulose (NC), NC is stabilized by washing with industrial water in
its synthesis process. However, there is a possibility that the components in industrial water contribute to the thermal stability
of NC. In this way, the purpose of this study is to clarify the effect of industrial water components on the thermal stability
of NC. In experiments, a heat flux calorimeter was used to observe the thermal behavior of NC with the residue of vaporized
industrial water. The induction period of heat release of NC with 2-mass% residues was approximately 2–5 h shorter than that
of NC alone whose induction period was observed at 7 h. Those results indicate that the residue destabilized NC. On the other
hand, when the additive amount of the residue was increased, the induction period gradually increased as well. Based upon
these results, we assume that inorganic salts contributing to stabilization and destabilization competitively coexist in the
industrial water components. The same thermal analysis was performed on NC with CaCO3, CaSO4, CaCl, ZnSO4, NaCl, and CuCl. Those salts are predicted to exist in the industrial water. In the results, the induction period of NC with
2-mass% CaCO3 was approximately 15-h longer than that of NC alone, while the induction period with the inorganic salts CaSO4, CaCl, ZnSO4, NaCl, and CuCl was 4–5-h shorter. Therefore, when the industrial water components accumulate in NC, the destabilization
by inorganic salts such as CaSO4, CaCl, ZnSO4, NaCl, and CuCl and the stabilization by compounds such as CaCO3 are thought to countervail against each other. 相似文献
46.
A synthetic method of isoquinolines from aryl ketone O-acyloxime derivatives and internal alkynes has been developed using [Cp*RhCl(2)](2)-NaOAc as the potential catalyst system. The present transformation is carried out by a redox-neutral sequence of C-H vinylation via ortho-rhodation and C-N bond formation of the putative vinyl rhodium intermediate on the oxime nitrogen, where the N-O bond of oxime derivatives could work as an internal oxidant to maintain the catalytic cycle. 相似文献
47.
Shunsuke Kanematsu Kazuhiko Matsumoto Rika Hagiwara 《Electrochemistry communications》2009,11(6):1312-1315
Fluorohydrogenate ionic liquids of quaternary phosphonium cations, tri-n-butylmethylphosphonium (P4441) fluorohydrogenate, tetra-n-butylphosphonium (P4444) fluorohydrogenate, and tri-n-butyl-n-octylphosphonium (P4448) fluorohydrogenate, have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium chloride precursors. All the obtained salts have melting points below room-temperature with a vacuum-stable composition of P444m(FH)2.3F (m = 1, 4, and 8) and were characterized by density, conductivity, and viscosity measurements. Linear sweep voltammetry with a glassy carbon working electrode shows that the P444m(FH)2.3Fs have wide electrochemical windows exceeding 5.2 V. In particular, P4441(FH)2.3F has an electrochemical window of 6.0 V, which is the widest among fluorohydrogenate ionic liquids reported to date. The thermal stability of these ionic liquids is also improved compared to the salts of N-heterocyclic ammonium cations. 相似文献
48.
49.
Shunsuke Kotani Shohei AokiMasaharu Sugiura Makoto Nakajima 《Tetrahedron letters》2011,52(22):2834-2836
Trichlorosilyl triflate, in the presence of a chiral Lewis base catalyst, provides an effective method for the enantioselective direct-type aldol reaction of aldehydes and ketones. A chiral Lewis base induces both the production and activation of trichlorosilyl enol ether, yielding an aldol product in good yield and with high diastereo- and enantioselectivities. 相似文献
50.
Kazuki OsakamaMasaharu Sugiura Makoto Nakajima Shunsuke Kotani 《Tetrahedron letters》2012,53(32):4199-4201
An efficient method was developed for the enantioselective reductive aldol reaction of α,β-unsaturated ketones with aldehydes in the presence of a Lewis base catalyst; conjugate reduction using a tertiary amine and trichlorosilyl triflate, followed by an aldol reaction with BINAP dioxide (BINAPO) as an organocatalyst, gave the corresponding product in high yield with high stereoselectivity. 相似文献