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91.
Takeshi MiyazakiHirofumi Maekawa Kazuaki YonemuraYoshimasa Yamamoto Yoshiko YamanakaIkuzo Nishiguchi 《Tetrahedron》2011,67(8):1598-1602
Treatment of various types of aromatic δ-ketoesters 2, 7, and 9 with Mg-turnings for Grignard reaction at −5 to 0 °C in N,N-dimethylformamide (DMF) containing trimethylsilyl chloride (TMSCl) brought about selective and reductive intramolecular cyclization to give the corresponding α-aryl-α-hydroxycyclopentanones 5, 8, and 10, respectively, in moderate to good yields. Similar reductive intramolecular cyclization of aromatic δ-ketodiesters 14, followed by acidic hydrolysis and decarboxylation easily gave the corresponding 2-aryl-2-cyclopenten-1-ones 15. The present facile coupling may be initiated through electron transfer from Mg metal to the aromatic carbonyl groups of 2, 7, 9, and 14 to generate the corresponding radical anions, followed by their intramolecular nucleophilic attack to the ester groups to give the corresponding five-membered ring compounds 5, 8, 10, and 15, respectively. 相似文献
92.
Shibata T Hashimoto H Kinoshita I Yano S Nishioka T 《Dalton transactions (Cambridge, England : 2003)》2011,40(18):4826-4829
The first example of the diastereoselective synthesis induced by anomeric isomerism of sugar units in ligands of metal complexes was demonstrated. S and R configurations of chiral-at-metal Ir(III) and Rh(III) complexes were selectively obtained by using chelate-type NHC ligands with α- and β-glucopyranosyl units, respectively. 相似文献
93.
Many empirical parameters have been suggested to measure solvent effects in chemical reactions. Gutmann's donor number has been a successful parameter to quantify the electron-donating property of the solvent molecule; it is defined as the enthalpy change of the addition reaction of solvent molecule to SbCl(5) in 1,2-dichloroethane. Calorimetric measurements can be applied to determine the quantity. Because the existence of water is critical for reactions in organic solvents, we have analyzed the enthalpy change using the titration calorimetry while considering the complexation with water. The determined donor numbers of formamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and 1,1,3,3-tetramethylurea (TMU) are 22.4, 26.5, 30.0, and 40.4, respectively. The values of DMF and DMSO are in perfect agreement with those of Gutmann. A reliable value for TMU is obtained for the first time on the basis of the enthalpy change for the addition reaction. 相似文献
94.
K Miyazaki Y Kato T Matsui S Hayashi Y Iriyama T Fukutsuka T Abe Z Ogumi 《Physical chemistry chemical physics : PCCP》2012,14(31):11135-11138
A high proton-conducting phase appears in the composites of zirconium- and titanium-oxide nanoparticles and polyphosphoric acid (HPO(3)). Metal oxide nanoparticles (ZrO(2) and TiO(2)) react with HPO(3) and form composite electrolytes containing pyrophosphates (ZrP(2)O(7) or TiP(2)O(7)) and shortened HPO(3) chains. The ZrO(2)-HPO(3) composite exhibits eleven times higher conductivity than sole HPO(3) at the maximum. A formed layer of shortened HPO(3) chains surrounding the pyrophosphates enhances the proton conductivities of the composite electrolytes and reduces the activation energies for the proton conductivities from 50 to 30 kJ mol(-1). 相似文献
95.
Yamaguchi T Matsumoto S Masumizu T Takechi S Ishida T Takeshita K Kansui H Kunieda T 《Chemical & pharmaceutical bulletin》2012,60(5):639-646
The various biological activity of dihydropyrazines(DHPs)due to the radical generation potency has been described in previous papers. Detailed data about radical species generating be mentioned here. The electron spin resonance (ESR) spin-trapping technique revealed that DHPs generate free radical species such as ·OH, ·OOH, ·CHR(2) and ·CR(3). Oxygen radicals and two carbon-centered radicals were detected as adducts of the spin traps DMPO and DBNBS, respectively. All the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)- and 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS)-adducts of compounds DHP-1-8 exhibited approximately the same signal patterns, with various levels of intensity depending on the substituent of the dihydropyrazine ring. The ESR signal intensity of DHPs also increased remarkably upon addition of Cu(2+), resulting that the effects of DHPs were enhanced. 相似文献
96.
Kazuaki Shimada Yukichi Takata Yu Osaki Akiko Moro-oka Hisashi Kogawa Maiko Sakuraba Shigenobu Aoyagi Yuji Takikawa Satoshi Ogawa 《Tetrahedron letters》2009,50(48):6651-11128
Treatment of substituted isotellurazoles or their Te-oxides with acetylenic dienophiles efficiently afforded polysubstituted pyridine derivatives through a pathway involving hetero-Diels-Alder reaction of isotellurazoles and the subsequent tellurium extrusion from the intermediary cycloadducts. 相似文献
97.
The vibrational spectrum for a fine particle is obtained by exactly solving the wave equation for a homogeneous elastic sphere with free surface. In terms of this frequency spectrum, enhancements in the specific heat of fine particles are calculated and compared with the experiments at low temperatures. Qualitative features of the experimental results are consistently explained in our theory. 相似文献
98.
99.
Oxygen—atom transfer process in the photolysis of aromatic amine N-oxides was suggested to involve the primary oxygen—atom elimination from N-oxides to give “oxene” follwed by its reactions with the oxygen-acceptors. 相似文献
100.
Thallium-201 distribution in the blood was investigated both in vivo and in vitro. Thallium-201 was distributed into the erythrocytes and plasma with the ratio of 1.4 +/- 0.3 to 1.0, immediately after its administration. The uptake of 201Tl into the erythrocytes in vitro were affected by the incubation temperature and the presence of ouabain and KCl; indicating that the 201Tl was uptaken into cells partly through their membranes Na, K-ATPase. Erythrocytes could retain 201Tl in it, whereas 201Tl was present as free ion in the plasma. Thallium-201 was flew out of erythrocytes into the plasma, keeping the ratio of 201Tl in erythrocytes/plasma to be 1.9 +/- 0.2/1.0. 相似文献