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861.
Highly Chemo‐, Regio‐, and Enantioselective Rhodium‐Catalyzed Cross‐Cyclotrimerization of Two Different Alkynes with Alkenes
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Jun Hara Mana Ishida Masayuki Kobayashi Prof. Dr. Keiichi Noguchi Prof. Dr. Ken Tanaka 《Angewandte Chemie (International ed. in English)》2014,53(11):2956-2959
It has been established that a cationic rhodium(I)/(R)‐tol‐binap complex catalyzes the cross‐cyclotrimerization of silylacetylenes, di‐tert‐butyl acetylenedicarboxylates, and acrylamides with excellent chemo‐, regio‐, and enantioselectivities. Unsymmetrical alkynoates can also be employed in place of di‐tert‐butyl acetylenedicarboxylate for this process, but with reduced chemoselectivity. 相似文献
862.
Disilanyl Double‐Pillared Bisternaphthyl (SiDPBT): Synthesis and Interfused Packing Structures with Herringbone and π‐Stack Motifs
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Dr. Waka Nakanishi Naoto Matsuyama Daisuke Hara Akinori Saeki Dr. Shunpei Hitosugi Prof. Shu Seki Prof. Hiroyuki Isobe 《化学:亚洲杂志》2014,9(7):1782-1785
A silacyclophane molecule with two disilanyl pillars and two oligoarylene units was synthesized. The molecule was packed in a single crystal with a new motif interfusing π‐stack and herringbone packing structures. The hole transporting ability of the solid was revealed by using the flash‐photolysis time‐resolved microwave conductivity method. The molecular structure, albeit a singly‐bonded arylene macrocycle, was rigidified by the unique packing array, which favorably contributed to the hole transporting ability of the solid via the small reorganization energy through the charge transport. 相似文献
863.
Hiromu Kawakubo Tomoko Suzuki Kazutaka Nishino Futaba Hara Tomoyoshi Takano Yoshito Takebayashi 《合成通讯》2013,43(9):1068-1072
Diethyl azodicarboxylate (DEAD) is a well-known coupling reagent that can be readily synthesized from diethylhydrazodicarboxylate (DEHD). The bromination of commercially available ethyl allophanate (1) in CHCl3, followed by the Hofmann-type rearrangement reaction of the resulting N-brominated species 2 and 3 in C2H5OH in the presence of 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), gave DEHD in good yield from a one-pot process. Interestingly, however, the bromination and Hofmann-type rearrangement reactions did not occur in the presence of N(C2H5)3. These results therefore suggest that this reaction is reliant upon a high level of reactivity during the bromination reaction to give 2 and 3, and that these N-brominated species require the presence of a strong and nonnucleophilic base to undergo the Hofmann-type rearrangement to give DEHD. 相似文献
864.
Zhanying Zhang Ian M. O’Hara William O. S. Doherty 《Cellulose (London, England)》2013,20(6):3179-3190
Pretreatments of sugarcane bagasse by three high boiling-point polyol solutions were compared in acid-catalysed processes. Pretreatments by ethylene glycol (EG) and propylene glycol solutions containing 1.2 % H2SO4 and 10 % water at 130 °C for 30 min removed 89 % lignin from bagasse resulting in a glucan digestibility of 95 % with a cellulase loading of ~20 FPU/g glucan. Pretreatment by glycerol solution under the same conditions removed 57 % lignin with a glucan digestibility of 77 %. Further investigations with EG solutions showed that increases in acid content, pretreatment temperature and time, and decrease in water content improved pretreatment effectiveness. A good linear correlation of glucan digestibility with delignification was observed with R2 = 0.984. Bagasse samples pretreated with EG solutions were characterised by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction, which confirmed that improved glucan enzymatic digestibility is mainly due to delignification and defibrillation of bagasse. Pretreatment by acidified EG solutions likely led to the formation of EG-glycosides. Up to 36 % of the total lignin was recovered from pretreatment hydrolysate, which may improve the pretreatment efficiency of recycled EG solution. 相似文献
865.
Electrochemical polymerization of benzene has been carried out in a one-compartment cell using indium-tin oxide conducting glass as a working electrode and Pt mesh as a counterelectrode by the use of a composite electrolyte of aluminum chloride and copper(I) chloride in nitrobenzene. On applying a constant voltage at + 1.8 V vs SCE, a brown and flexible polyparaphenylene (PPP) film was smoothly obtained on the ITO anode surface. The electrical conductivity of the film as grown was 1.9 × 10?5 S/cm. Aluminum and chlorine atoms were detected in the film from XPS studies, so the film might contain AlCl4 ? (and Cl?) as a dopant. Scanning electron micrographs of the growing side surface of the film prepared at a constant potential of + 1.8 V vs SCE showed a fibrillar morphology. The fibril diameter (~100 nm) was similar to that of a polyaniline film. The PPP film exhibited a spin concentration of 1.0 × 1019 spins/g, which corresponds to 800 phenylene units per spin. The g-value and the peak-to-peak linewidth were 2.0045 and 7 G, respectively. 相似文献
866.
Yoshiki Oda Sho Matsuda Akihiko Murota Kaname Katsuraya 《Supramolecular chemistry》2013,25(7):638-642
This study describes the 2D 1H and 13C diffusion-ordered NMR spectroscopy (DOSY) experiments using the mixed sample of α-cyclodextrin (α-CyD) and phenyl β-d-(13C6)glucopyranoside (1). Both the 2D 1H and 13C DOSY spectra showed the component with a diffusion coefficient different from those of α-CyD and 1, which suggested the inclusion complexation of α-CyD with 1. 相似文献
867.
Takatsune Yoshida Ippei Kurimoto Hiroyuki Umejima Shunsuke Watanabe Kazuhiro Sako Akihiko Kikuchi 《Colloid and polymer science》2013,291(5):1191-1199
Eudragit® E/HCl salt (E–SD) displays a good antireprecipitation effect on solid dispersion formulations of poorly water-soluble drugs. To elucidate the mechanism underlying the antireprecipitation effect of E–SD, a study on supersaturation was conducted using a dissolution test method with test fluids at varying pH and ionic strength values. Both pH and ionic strength of the test fluid were shown to influence the antireprecipitation effect of E–SD; a strong antireprecipitation effect was observed at a neutral pH (pH?6~7) and an ionic strength of 0.1 to 1.0. To investigate E–SD in its dissolved state in each test fluid, fluorescence measurement using pyrene as a probe molecule and dynamic light-scattering (DLS) measurement were conducted. The total fluorescence intensity of pyrene increased with increasing E–SD concentrations. Further, small nanoparticles were observed using DLS measurement. These results suggest that E–SD may form a micelle-like structure in the dissolved test fluid. 相似文献
868.
Gi Heon Kim Shintaro Enomoto Akihiko Kanazawa Takeshi Shiono Tomiki Ikeda Lee-Soon Park 《Liquid crystals》2013,40(2):271-277
We have explored the change in alignment of a nematic liquid crystal, 4'-pentyl-4-cyanobiphenyl (5CB) with three types of photosensitive polyimide as the alignment layer by photoirradiation at 366 nm. The photosensitive polyimide alignment layer induced a reversible change in alignment of 5CB. It was observed that the 5CB molecules became aligned from homogeneous alignment to homeotropic on photoirradiation with a d.c. electric field as a bias, and reversed to the homogeneous state when photoirradiation was ceased. This result indicates that optical switching could be repeated by on and off switching of the excitation light at 366 nm. The optical switching of the nematic liquid crystal might be mainly due to a photophysical change in the polyimide surface which is affected by the chemical structures of the polyimides at the temperature at which 5CB exhibits a nematic phase. The optical switching of nematic liquid crystals with photosensitive polyimides as the alignment layer is a novel driving method for nematic liquid crystals. 相似文献
869.
Akihiko Kameyama Hideharu Ishida Makoto Kiso Akira Hasegawa 《Journal of carbohydrate chemistry》2013,32(5):641-654
Abstract The first total synthesis of tumor-associated glycolipid antigen, sialyl Lea, is described. Methylsulfenyl bromide-silver triflate-promoted coupling of 2-(trimethylsilyl)ethyl O-(2-acetamido-6-O-benzyl-2-deoxy-β-d-glucopyranosyl)-(1→3)-O-(2,4,6-tri-O-benzyl-β-d-galactopyranosyl)-(1→4)-2,3,6-tri-O-benzyl-β-d-glucopyranoside (2) with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-d-glycero-α-d-galacto-2-nonulopyranosylonate)-(2→3)-2,4,6-tri-O-benzoyl-1-thio-β-d-galactopyranoside (3) afforded the pentasaccharide 4a and 5a in good yields. Glycosylation of 4a with methyl 2,3,4-tri-O-benzyl-1-thio-β-l-fucopyranoside (6) by use of N-iodosuccinimide (NIS) — trifluoromethanesulfonic acid (TfOH) as a promoter, gave the desired hexasaccharide 7. Compound 7 was converted into the α-trichloroacetimidate 10, via reductive removal of benzyl groups, O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile, which, on coupling with (2S, 3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1, 3-diol (11), gave the β-glycoside 12. Finally, 12 was transformed, via selective reduction of the azide group, coupling with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester group, into the title ganglioside 15 in good yield. 相似文献
870.
Akihiko Toda Takeshi Arita Chiyoko Tomita Masamichi Hikosaka 《Thermochimica Acta》1999,330(1-2):75-83
Computer simulation has been applied to the modeling of the melting kinetics of polymer crystals, which we have recently presented to predict the response of the kinetics to a sinusoidal modulation in temperature on heating. The frequency and heating-rate dependencies have been examined with a Gaussian or uniform distribution of the melting points. For both of the distributions, the details of the dependence have been examined on the basis of the analytical results of the modeling. It has also been confirmed that the response of the kinetics has higher harmonics as expected from the formulation of the modeling. This behavior corresponds to the experimental results of temperature-modulated DSC (T-MDSC) in the melting region of polymer crystals. 相似文献