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91.
Toyoharu Kobayashi Masako Ishida Kazuhiro Imaida Hideki Abe Hisanaka Ito 《Tetrahedron letters》2017,58(33):3294-3295
The stereoselective total synthesis of pleurolactone has been accomplished in 7 steps. The key synthetic features were the construction of four contiguous stereocenters using an endo-selective Diels-Alder reaction and high diastereoselective dihydroxylation. 相似文献
92.
Dr. Yasunori Minami Prof. Dr. Tamejiro Hiyama 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(2):391-399
Organo(trialkyl)silanes have several advantages, including high stability, low toxicity, good solubility, easy handling, and ready availability compared with heteroatom-substituted silanes. However, methods for the cross-coupling of organo(trialkyl)silanes are limited, most probably because of their exceeding robustness. Thus, a practical method for the cross-coupling of organo(trialkyl)silanes has been a long-standing challenging research target. This article discusses how aryl(trialkyl)silanes can be used in cross-coupling reactions. A pioneering example is CuII catalytic conditions with the use of electron-accepting aryl- or heteroaryl(triethyl)silanes and aryl iodides. The reaction forms biaryls or teraryls. This design concept can be extended to Pd/CuII-catalyzed cross-coupling polymerization reactions between such silanes and aryl bromides or chlorides and to CuI-catalyzed alkylation using alkyl halides. 相似文献
93.
Proton Order–Disorder Phenomena in a Hydrogen‐Bonded Rhodium–η5‐Semiquinone Complex: A Possible Dielectric Response Mechanism
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Dr. Minoru Mitsumi Kazunari Ezaki Yuuki Komatsu Prof. Dr. Koshiro Toriumi Dr. Tatsuya Miyatou Prof. Dr. Motohiro Mizuno Nobuaki Azuma Prof. Dr. Yuji Miyazaki Prof. Dr. Motohiro Nakano Prof. Dr. Yasutaka Kitagawa Dr. Takayasu Hanashima Dr. Ryoji Kiyanagi Dr. Takashi Ohhara Prof. Dr. Kazuhiro Nakasuji 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9682-9696
A newly synthesized one‐dimensional (1D) hydrogen‐bonded (H‐bonded) rhodium(II)–η5‐semiquinone complex, [Cp*Rh(η5‐p‐HSQ‐Me4)]PF6 ([ 1 ]PF6; Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl; HSQ=semiquinone) exhibits a paraelectric–antiferroelectric second‐order phase transition at 237.1 K. Neutron and X‐ray crystal structure analyses reveal that the H‐bonded proton is disordered over two sites in the room‐temperature (RT) phase. The phase transition would arise from this proton disorder together with rotation or libration of the Cp* ring and PF6? ion. The relative permittivity εb′ along the H‐bonded chains reaches relatively high values (ca., 130) in the RT phase. The temperature dependence of 13C CP/MAS NMR spectra demonstrates that the proton is dynamically disordered in the RT phase and that the proton exchange has already occurred in the low‐temperature (LT) phase. Rate constants for the proton exchange are estimated to be 10?4–10?6 s in the temperature range of 240–270 K. DFT calculations predict that the protonation/deprotonation of [ 1 ]+ leads to interesting hapticity changes of the semiquinone ligand accompanied by reduction/oxidation by the π‐bonded rhodium fragment, producing the stable η6‐hydroquinone complex, [Cp*Rh3+(η6‐p‐H2Q‐Me4)]2+ ([ 2 ]2+), and η4‐benzoquinone complex, [Cp*Rh+(η4‐p‐BQ‐Me4)] ([ 3 ]), respectively. Possible mechanisms leading to the dielectric response are discussed on the basis of the migration of the protonic solitons comprising of [ 2 ]2+ and [ 3 ], which would be generated in the H‐bonded chain. 相似文献
94.
Kazunori Masuko Chiharu Kumano Ryo Sugawara Kazuhiro Nakabayashi Hideharu Mori 《Journal of polymer science. Part A, Polymer chemistry》2021,59(15):1664-1677
A series of amino-acid-based amphiphilic diblock copolymer nano-objects having different morphologies were developed by reversible addition–fragmentation chain-transfer (RAFT) dispersion polymerization of styrene (St) in methanol. This was mediated by six different hydrophilic poly(N-acryloyl amino acid) macro-chain transfer agents (CTAs), including three carboxylic-acid-containing ones, poly(N-acryloyl-l -proline) (PAProOH), poly(N-acryloyl-4-trans-hydroxy-l -proline) (PAHypOH), and poly(N-acryloyl-l -threonine) (PAThrOH) prepared by RAFT polymerization, and their methyl ester forms, PAProOMe, PAHypOMe, and PAThrOMe. The effects of polymerization conditions on RAFT dispersion polymerization of St using a dithiocarbamate-terminated PAProOH was investigated. A systematic study of the effects of monomer conversion and concentration afforded the formation of various morphologies (i.e., spheres, worms, and vesicles). The effects of hydrogen-bonding and ionic interactions of the macro-CTAs on the assembled structures of the nano-objects were evaluated using six different macro-CTAs. Transforming the products from methanol to water via dialysis produced amino-acid-based block copolymer nano-objects, exhibiting pH-responsive morphological change, in aqueous solution. 相似文献
95.
To prepare cross‐linked silicone (silicone rubber) particles in an aqueous medium, we investigated two synthesis methods involving a miniemulsion system. The first method was based on cationic ring‐opening polymerization of cyclic siloxane, which is a common synthetic route for linear silicone oil and uses octamethylcyclotetrasiloxane (D4) as the monomer and dimeric D4 (bis‐D4) as the cross‐linker. Although this method produces silicone particles, the particles do not remain in the particulate state after drying because of low cross‐linking density. The polymerization mechanism of this method was also investigated, which proceeds under the ring‐opening reaction of D4 in monomer droplets and upon polycondensation of hydrolyzed D4, which occurs in the water phase (ie, outside the monomer droplets). This mechanism implied that introducing the cross‐linking structure into particles is difficult because of the low solubility of bis‐D4 in water. To overcome these difficulties, we demonstrated a second method of preparing silicone particles based on the thiol‐Michael addition reaction between thiol‐terminated silicone oil and triacrylate in miniemulsion systems. Transmission electron microscopy images indicated that the silicone particles obtained in the particulate state upon drying and the aggregates of these particles showed elasticity. 相似文献
96.
Formation of homogeneous nanocomposite films at ambient temperature via miniemulsion polymerization using graphene oxide as surfactant
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Yasemin Fadil S. H. C. Man Florent Jasinski Hideto Minami Stuart C. Thickett Per B. Zetterlund 《Journal of polymer science. Part A, Polymer chemistry》2017,55(14):2289-2297
A convenient and industrially scalable method for synthesis of homogeneous nanocomposite films comprising poly(styrene‐stat‐butyl acrylate) and nanodimensional graphene oxide (GO) or reduced GO (rGO) is presented. Importantly, the nanocomposite latex undergoes film formation at ambient temperature, thus alleviating any need for high temperature or high pressure methods such as compression molding. The method entails synthesis of an aqueous nanocomposite latex via miniemulsion copolymerization relying on nanodimensional GO sheets as sole surfactant, followed by ambient temperature film formation resulting in homogeneous film. For comparison, a similar latex obtained by physical mixing of a polymer latex with an aqueous GO dispersion results in severe phase separation, illustrating that the miniemulsion approach using GO as surfactant is key to obtaining homogeneous nanocomposite films. Finally, it is demonstrated that the GO sheets can be readily reduced to rGO in situ by heat treatment of the film. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2289–2297 相似文献
97.
Toru Minami Ryoji Kouno Tatsuo Okauchi Mitsuharu Nakamura Junji Ichikawa 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):689-692
The α-phosphonovinyl anions, generated in situ from treatment of β-hetero-substituted vinyl-phosphonates 1a-c with LDA (or LTMP), were trapped with various electrophiles such as chlorotriorganosilanes, chlorotrimethylgermane, chlorotriorganotins, dimethyl disulfide, and halogen to afford the corresponding β-hetero-substituted α-functionalized vinylphosphonates 2–14 in good to excellent yields. The Friedel-Crafts reaction of α-(silyl) or α-(germyl)phosphonoketene dithioacetals 2, 9 or 4 with acid chlorides gave α-acylated phosphonoketene dithioacetals 15–19 in 53–91 % yields. The palladium-catalyzed cross-coupling reaction of β-ethoxy-α-(tributylstannyl)vinylphosphonate 13 with a variety of organic halides (R = acyl, allyl, aryl etc.) provided β-ethoxy-α-substituted vinylphosphonates 20–25 in good to moderate yields. The palladium-mediated cross-coupling reaction of α-(iodo)-vinyl-phosphonates 7, 14 with terminal acetylenes afforded α-alkynylated vinylphosphonates 26–29 in 69–83 % yields. 相似文献
98.
H. Ahmad K. Kumar M. A. Rahman M. M. Rahman M. A. J. Miah H. Minami M. A. Nuri 《先进技术聚合物》2013,24(8):740-746
Considering the application potentials of organic materials possessing both conducting and ferromagnetic functions in various electronic devices, an attempt was made to prepare conducting polyaniline (PANI) layered magnetic nano composite polymer particles. Two routes were used to modify magnetic Fe3O4 core particles. In one route, seeded emulsion polymerization of methyl methacrylate (MMA) was carried out in presence of nano‐sized Fe3O4 core particles. In another route, cross‐linker ethyleneglycol dimethacrylate (EGDM) was used in addition to MMA. The modified composite particles were named as Fe3O4/PMMA and Fe3O4/P(MMA‐EGDM), respectively. Finally, seeded chemical oxidative polymerization of aniline was carried out in the presence of Fe3O4/PMMA and Fe3O4/P(MMA‐EGDM) composite seed particles to obtain Fe3O4/PMMA/PANI and Fe3O4/P(MMA‐EGDM)/PANI composite polymer particles. The modification of Fe3O4 core particles was confirmed by electron micrographs, FTIR, UV–visible spectra, X‐ray photoelectron spectra, X‐ray diffraction pattern and thermogravimetric analyses. A comparative study showed that crosslinking of intermediate shell improved the magnetic susceptibility and electrical conductivity of PANI layered magnetic nano composite particles. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
99.
Tatsuro Ouchi Kazuhiro Nomoto Yoshifumi Hosaka Minoru Imoto Tadao Nakaya Tsutomu Iwamoto 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6-7):859-866
Abstract Three kinds of betaine-type polymers, which are macromolecular amphoteric electrolytes, were found to be able to polymerize vinyl monomers in aqueous solution through a radical mechanism without any further initiator. Betain-type polymers form hydrophobic areas (HA) in water. Vinyl polymerization commenced in the HA. The effect of the pH of the aqueous solution on polymerization was investigated. 相似文献
100.
Atsushi Tarui Shoji Kondo Kazuyuki Sato Masaaki Omote Hideki Minami Yoshihisa Miwa Akira Ando 《Tetrahedron》2013,69(5):1559-1565
A highly diastereoselective cross-coupling reaction of an α-bromo-α-fluoro-β-lactam with a wide range of aryl Grignard reagents was catalyzed by Ni/bis(oxazoline) in yields of up to 98%. The product was obtained diastereoselectively as an anti-isomer. This is the first successful α-arylation of an α-fluoro-β-lactam to produce diverse α-aryl-α-fluoro-β-lactams. 相似文献