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101.
Lee VY Ito Y Yasuda H Takanashi K Sekiguchi A 《Journal of the American Chemical Society》2011,133(13):5103-5108
The reaction of 3,4-dichlorotetragermetene derivative 2 with Na(2)[Fe(CO)(4)] in THF produced a (tetragermacyclobutadiene)tricarbonyliron complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]Fe(CO)(3)4, which has a slightly folded Ge(4) ring perhaptocoordinated to the Fe center. Structural and spectral characteristics of 4 show a remarkable π-donating ability of the tetragermacyclobutadiene ligand toward the transition metal, surpassing that of tetrasilacyclobutadiene and cyclobutadiene ligands. Reduction of 2 with KC(8) resulted in exclusive formation of the dipotassium salt of the tetragermacyclobutadiene dianion derivative 3(2-)·[K(+)(thf)(2)](2), representing a rare example of a 6π-electron compound that, on the basis of its structural and magnetic properties, was recognized as a nonaromatic species. Reaction of 3(2-)·[K(+)(thf)(2)](2) with CpCoI(2)(PPh(3)) produced a (cyclopentadienyl)(tetragermacyclobutadiene)cobalt complex, [{η(4)-((t)Bu(2)MeSi)(4)Ge(4)}]CoCp 7, as the first example of a sandwich compound featuring an all-germanium-containing cyclic polyene ligand. 相似文献
102.
Yuki Goto Masahiro Shiosaki Takeshi Hanamoto Masato Yoshida Hideo Sawada 《Colloid and polymer science》2013,291(5):1211-1217
Fluoro(silyl)acetylenes, which were prepared by reaction of 1,1-difluoroethylene with silyl chlorides, reacted with triethylamine to give dark-brown colored polyfluoro(silyl)acetylene powders in excellent to moderate isolated yields. In contrast, the corresponding nonfluorinated acetylene was unable to react with triethylamine at all to afford poly(silyl)acetylene under similar conditions. Polyfluoro(silyl)acetylenes thus obtained were nanometer size-controlled cubic fine particles with a good dispersibility and stability in a variety of solvents. These polyfluoro(silyl)acetylene nanoparticles exhibited clear absorption and emission spectra related to the conjugated units in polymer main chain. Furthermore, these polyfluoro(silyl)acetylene nanoparticles were applied to the surface modification of poly(methyl methacrylate) [PMMA] film to exhibit a higher oleophobicity imparted by fluorine on their surface, compared to that on the reverse side. Figure
New polyfluoro(silyl)acetylenes were prepared by reaction of the creesponding fluoro(silyl)acetylenes with triethylamine in excellent to moderate isolated yields. In contrast, the corresponding nonfluorinated silylacetylene was unable to give poly(silyl)acetylene under similar conditions. These polyfluoro(silyl)acetylenes thus obtained can form the nanometer size-controlled cubic fine particles (within 100 nm) in a variety of solvents. 相似文献
103.
Kyoichi Hanada Juntaro Nogami Prof. Dr. Kazunori Miyamoto Norihiko Hayase Dr. Yuki Nagashima Yusuke Tanaka Dr. Atsuya Muranaka Prof. Dr. Masanobu Uchiyama Prof. Dr. Ken Tanaka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(36):9313-9319
The enantioselective synthesis of aza[6] and [7]helicene-like molecules have been achieved by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex-catalyzed intramolecular [2+2+2] cycloaddition of cyanodiynes. This protocol was successfully applied to the diastereo- and enantioselective synthesis of an S-shaped double aza[6]helicene-like molecule with a high ee value of 89 %. Although no epimerization and racemization were observed in the double carbo[6]helicene-like molecule at 80 °C, epimerization and racemization of the double aza[6]helicene-like molecule proceeded at 80 °C. This double aza[6]helicene-like molecule showed good fluorescent quantum yields and chiroptical responses under both neutral and acidic conditions. 相似文献
104.
Hiroyoshi Nakajima Katsuhiro Yamada Yuki Iseki Satoru Hosoda Ayako Hanai Yasunori Oumi Toshiharu Teranishi Tsuneji Sano 《Journal of polymer science. Part A, Polymer chemistry》2003,41(24):3324-3332
Polypropylene (PP)/Ti-MCM-41 nanocomposites were prepared by isospecific propylene polymerization with Ti-MCM-41/Al(i-C4H9)3 catalyst. The cross polarization/magic angle spinning (CP/MAS) 13C NMR spectrum of the composite was similar to that of the conventional isotactic PP, and the decrease in the pore volume of Ti-MCM-41 in the nanocomposites, as measured by N2 adsorption, was consistent with the value calculated from the weight loss in the thermogravimetric analysis (TGA) curve; both these facts attest to propylene polymerization within the mesopores of Ti-MCM-41. Alkali treatment followed by extraction with o-dichlorobenzene allows us to extract the confined PP out of the Ti-MCM-41 mesopores. Although the PP/Ti-MCM-41 nanocomposites do not exhibit a crystalline melting point, the same PP when extracted from the mesopores showed a clear melting point at 154.7 °C; this indicates that the crystallization of PP confined in mesopores is strongly hindered. For the PP polymerized within the confinement, the molecular weight (Mw) and molecular weight distribution (Mw/Mn) were 84,000 and 4.3, respectively; these values were considerably smaller than those of the PP polymerized concurrently outside the Ti-MCM-41 mesopores (Mw = 200,000–450,000, Mw/Mn = 40–75). Therefore, the confinement also has a marked effect on the molecular weight of the PP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3324–3332, 2003 相似文献
105.
In bacteriorhodopsin (bR), Arg-82bR has been proven to be a very important residue for functional role of this light-driven proton pump. The arginine residue at this position is a super-conserved residue among archaeal rhodopsins. pharaonis phoborhodopsin (ppR; or called as "pharaonis sensory rhodopsin II") has its absorption maximum at 498 nm and acts as a sensor in the membrane of Natronobacterium pharaonis, mediating the negative phototaxis from the light of wavelength shorter than 520 nm. To investigate the role of the arginine residue (Arg-72ppR) of ppR corresponding to Arg-82bR, mutants whose Arg-72ppR was replaced by alanine (R72A), lysine (R72K), glutamine (R72Q) and serine (R72S) were prepared. These mutants were unstable in low concentrations of NaCl and lost their color gradually when the proteins were solubilized with 0.1% n-dodecyl-beta-D-maltoside. The order of instability was R72S > R72A > R72K > R72Q > the wild type. The rates of denaturation were reduced in a solution of high concentrations of monovalent anions. 相似文献
106.
M Miyauchi R Endo K Watanabe Y Kawahara M Iwata I Kawamoto 《Chemical & pharmaceutical bulletin》1990,38(6):1587-1590
Acyloxyalkyl esters (2a-d), alkyloxycarbonyloxyalkyl esters (2e-g) and (5-methyl-2-oxo-1,3-dioxol-4-yl)methyl ester (2h) of (5R,6S)-2-(2-fluoroethylthio)-6-[(1R)-1-hydroxyethyl]penem-3- carboxylic acid (1) were synthesized. Enhanced oral absorption was observed in mice reflecting increased lipophilicity, compared with the parent 1 itself. Among them, the ester 2h showed a prolonged plasma level and a large area under the blood concentration-time curve (AUC) in rats. These ester-type prodrugs of penem 1 in phosphate buffer (pH 6.86) were much more stable than those of cephalosporins which easily degraded via isomerization to delta 2 cephalosporins. 相似文献
107.
108.
109.
Nishizawa M Hirakawa H Nakagawa Y Yamamoto H Namba K Imagawa H 《Organic letters》2007,9(26):5577-5580
The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded alpha,beta-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction. 相似文献
110.