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241.
Takahiro Hosokawa Toshiyuki Ohta Yoshihiro Okamoto Shun-Ichi Murahashi 《Tetrahedron letters》1980,21(13):1259-1260
Methylene dioximes are formed from ketoximes and CH2Cl2 using either KO2 with a catalytic amount of Pd(II) complex or K2CO3 with 18-crown-6 catalyst. The reactivity of ketoximes towards CH2Cl2 is reversed between these two methods. 相似文献
242.
243.
Unusual Electro‐Optic Kerr Response in a Self‐Stabilized Amorphous Blue Phase with Nanoscale Smectic Clusters 下载免费PDF全文
Dr. Khoa V. Le Miho Hafuri Dr. Hale Ocak Prof. Belkız Bilgin‐Eran Prof. Carsten Tschierske Prof. Takeo Sasaki Dr. Fumito Araoka 《Chemphyschem》2016,17(10):1425-1429
We investigated the electro‐optic response in the “foggy” amorphous blue phase (BPIII) as well as in the isotropic phase. To the best of our knowledge, such a study has not yet been performed due to the very limited thermal range of BPIII. In this study, we used a single‐component chiral bent‐core liquid crystal with a self‐stabilized BPIII, which is stable over a wide temperature range. The results show that the response time is on the order of hundreds of microseconds in the isotropic phase and increases to 1–2 ms in the BPIII (at TI?BP–T <1), then drastically increases up to a few tens of milliseconds upon further cooling in BPIII. Such an unusual behavior was explained on the basis of the high rotational viscosity and/or the existence of nanoscale smectic (Sm) clusters. The Kerr constant was also measured and found to be ~500 pm V?2, which is the largest among bent‐core BP systems reported so far and comparable with that of polymer‐stabilized BPs. 相似文献
244.
Inside Cover: Rhodium(III)‐Catalyzed Tandem [2+2+2] Annulation–Lactamization of Anilides with Two Alkynoates via Cleavage of Two Adjacent C−H or C−H/C−O bonds (Chem. Asian J. 16/2016) 下载免费PDF全文
245.
Murahashi T Watanabe T Otake S Hattori Y Takamura T Wakabayashi K Hirayama T 《Journal of chromatography. A》2003,992(1-2):101-107
A sensitive method for determining 3-nitrobenzanthrone in surface soil was developed. 3-Nitrobenzanthrone was reduced to 3-aminobenzanthrone by refluxing at 60 degrees C with hydrazine and Raney nickel for 20 min, and 3-aminobenzanthrone was determined by normal-phase high-performance liquid chromatography (HPLC) with fluorescence detection. We used a cyanopropyl stationary phase and an n-hexane-ethyl acetate (3:1, v/v) mobile phase, since 3-aminobenzanthrone exhibits fluorescence in a low-polarity solvent such as n-hexane or ethyl acetate, but not in a polar solvent such as water or methanol. The calibration graph showed good linearity (r2>0.9999) in the range of 0.002-2 ng, and the detection limit was 0.002 ng (S/N=3). 3-Nitrobenzanthrone in extracts from surface soil collected in the Chubu area (central area) of Japan was determined after clean-up using silica gel chromatography and high-performance liquid chromatography on a pyrenylethyl stationary phase. The concentration of 3-nitrobenzanthrone in surface soil was determined in the range of 1.2-1020 pg/g soil. 相似文献
246.
[reaction: see text] Asymmetric amination of 2,3-allenyl phosphates with nitrogen nucleophiles such as amines, hydroxylamines, and imides can be performed efficiently using a combination of zerovalent palladium complexes and SEGPHOS or MeOBIPHEP ligand, affording the corresponding optically active 1-aminated derivatives with enantiomeric excess of up to 97% ee. 相似文献
247.
Murahashi SI Komiya N Oda Y Kuwabara T Naota T 《The Journal of organic chemistry》2000,65(26):9186-9193
The ruthenium-catalyzed oxidation of alkanes with tert-butyl hydroperoxide and peracetic acid gives the corresponding ketones and alcohols highly efficiently at room temperature. The former catalytic system, RuCl(2)(PPh(3))(3)-t-BuOOH, is preferable to the oxidation of alkylated arenes to give aryl ketones. The latter system, Ru/C-CH(3)CO(3)H, is suitable especially for the synthesis of ketones and alcohols from alkanes. The ruthenium-catalyzed oxidation of cyclohexane with CH(3)CO(3)H in trifluoroacetic acid/CH(2)Cl(2) at room temperature gave cyclohexyl trifluoroacetate and cyclohexanone with 90% conversion and 90% selectivity (85:15). The mechanistic study indicates that these catalytic oxidations of hydrocarbons involve oxo-ruthenium species as key intermediates. 相似文献
248.
Fast atom bombardment mass spectrometry (FABMS) was applied to the direct detection of silica species dissolved in LiCl, NaCl, MgCl(2), CaCl(2) and SrCl(2) solutions in order to investigate its dissolution process in solution. Several species of dissolved silicate complexes in the solution were directly detected by FABMS. The peak intensities of [SiO(2)(OH)(2)Na](-), [SiO(3)(OH)Ca](-) and [SiO(3)(OH)Sr](-) increased with increasing concentrations of NaCl, CaCl(2) and SrCl(2), whereas the peak intensities of [SiO(2)(OH)(2)Li](-) and [SiO(3)(OH)Mg](-) did not increase with increasing concentrations of LiCl and MgCl(2). These results indicte that silicate and cation bind in the solution not after but before ionization. The isotope pattern of Sr(2+) confirmed the existence of the silicate-Sr complex not only with increase of the concentration of silica but also the mass numbers of Sr. The silicate complexes formed with Na(+), Ca(2+) and Sr(2+) showed high stability in chloride solution. This is in good accordance with the fact that Na(+), Ca(2+) and Sr(2+) accelerate the dissolution of silica to form complexes during solution equilibrium. Considering that the stability constant was examined and reported in other papers, this new findings that Mg(2+) does not form a complex with silicic acid (Si(OH)(4)) is very important. 相似文献
249.
Shun-Ichi Nozakura Takehiko Okamoto Kunimitsu Toyora Shunsuke Murahashi 《Journal of polymer science. Part A, Polymer chemistry》1973,11(5):1043-1051
In order to clarify the effect of bulky substituents on the stereoregulation of vinyl monomers, vinyl-1-adamantanecarboxylate and vinyl 1-adamantyl ether were synthesized and polymerized by radical and cationic mechanisms, respectively. As open-chain models of the adamantyl group, vinyl trialkylacetate (alkyl = ethyl, n-propyl, and n-butyl) and vinyl tri-n-propylcarbinyl ether were also synthesized and polymerized. The adamantly group in the vinyl ester favored syndiotactic propagation in a manner similar to the trimethylcarbinyl group. Higher homologs of tri-n-alkylcarbinyl group showed higher syndiotacticity but this effect was saturated in higher members of the series. The effect of the adamantyl group in vinyl ether was similar to that of the tert-butyl group, leading to high isotacticity on cationic polymerizations in nonpolar solvents and to atactic polymers in polar solvents, but the tri-n-propylcarbinyl group was found unique in leading to what was assumed to be a heterotactic polymer. Polymers with the adamantyl group showed much higher softening points than polymers of the corresponding open-chain groups. 相似文献
250.
Satoshi ImutaShinya Ochiai Miho KuribayashiNoritaka Chida 《Tetrahedron letters》2003,44(27):5047-5051
The total synthesis of (−)-actinobolin 2, an antipode of the natural product starting from d-glucose is described. A three-component coupling reaction of a functionalized cyclohexenone (+)-6, derived from d-glucose by way of Ferrier's carbocyclization, with vinyl cuprate and an aldehyde (R)-5 effectively constructed the carbon framework of 2 in a highly stereoselective manner. The formal synthesis of the natural enantiomer 1 from d-glucose was also achieved. 相似文献