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排序方式: 共有162条查询结果,搜索用时 15 毫秒
31.
Eiichi Masumoto Hiroshi Maruoka Fumi Okabe Sho Nishida Ryoko Tomita Toshihiro Fujioka Kenji Yamagata 《Journal of heterocyclic chemistry》2012,49(4):893-899
A novel synthetic route to 4‐pyridazineacetic acids 10 – 12 has been achieved by the ring‐expansion reaction of N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 – 9 . 1H‐Pyrazole‐4‐acetic acids 1 – 3 were reacted with iodoacetonitrile in the presence of triethylamine in refluxing acetonitrile to give the corresponding C‐cyanomethylated 1H‐pyrazole‐4‐acetic acids 4 – 6 as major products together with N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 and 8 as minor products. On the other hand, reactions of 1 and 3 with chloroacetonitrile in the presence of triethylamine in refluxing chloroform afforded the corresponding N‐cyanomethylated 3‐pyrazoline‐4‐acetic acids 7 and 9 as major products. Thermal treatment of 7 – 9 with sodium hydride in N,N‐dimethylformamide caused ring expansion to yield the corresponding 4‐pyridazineacetic acids 10 – 12 . 相似文献
32.
Naoko Asakuma Toshimi Fukui Mamoru Aizawa Motoyuki Toki Hiroaki Imai Hiroshi Hirashima 《Journal of Sol-Gel Science and Technology》2000,19(1-3):333-336
Structural changes stimulated by ultraviolet (UV) laser irradiations of sol-gel derived inorganic oxide films were investigated. Dried gel films of TiO2, Nb2O5, Ta2O5, SrTiO3 and Pb(Zr
x
Ti1–x
)O3 (PZT) were found to be crystallized by the laser irradiation. On the other hand, the photo-induced change in gel films of BaTiO3, LiNbO3 and LiTaO3 was not observed although the laser beams were absorbed in the films. These sol-gel films were thermally crystallized at almost the same temperature around 600–700°C except TiO2. Thus, the UV-laser-induced crystallization is not directly ascribed to a simple thermal effect with the irradiation. Photochemical properties of the cations are assumed to be important for the change in sol-gel films. 相似文献
33.
Naoko Asakuma Hiroshi Hirashima Hiroaki Imai Toshimi Fukui Motoyuki Toki 《Journal of Sol-Gel Science and Technology》2003,26(1-3):181-184
Structural changes in sol-gel films with photo-irradiation were investigated using zinc oxide (ZnO) derived from zinc acetate. The exposure of the films to an ultraviolet lamp induced hexagonal ZnO crystals in a relatively dense amorphous structure. On the other hand, the formation of zinc metal was found in a porous gel film. The photo-induced crystallization and reduction are ascribed to the electronic excitation in the metastable non-crystalline states. 相似文献
34.
Y. Hirashima H. Tamanishi H. Sato K. Saito A. Naito A. Suzuki 《Journal of Polymer Science.Polymer Physics》2004,42(6):1090-1098
The effects of continuous water exchange on the swelling behavior of poly(N‐isopropylacrylamide‐co‐sodium acrylate) gel were studied. The diameter of gels and the Na+ concentration in the solvent were measured at several constant intervals after the solvent (the distilled deionized water) was exchanged. The diameter decreased at room temperature as the solvent was exchanged with water, and it continued to decrease even after more than about 97% of the initial Na+ diffused into the water. Thus, the final swelling ratio of the gel was only slightly larger than that of the neutral poly(N‐isopropylacrylamide) gel. To reveal the structural change in molecular level, solid‐state 13C cross‐polarization/magic‐angle spinning, solid‐state 1H combined rotation and multiple‐pulse spectroscopy, and swollen‐state 13C dipolar decoupled/magic‐angle spinning NMR experiments were carried out for several dried and swollen samples by varying the times of water exchange. As a result, the intensity and position of the carboxyl peak changed, and the relative intensity of the nonionized carboxyl groups of gels increased with an increasing number of water exchanges. These results indicated that hydrogen bonding was formed between the two, nonionized carboxyl groups (? COOH) and/or between the ? COOH and ? CONH? groups. The macroscopic polymer network shrinkage is discussed in terms of the replacement of counterions Na+ by H+ and of the formation of intermolecular hydrogen bonding. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1090–1098, 2004 相似文献
35.
The formation of an ion-associate between vanadomolybdophosphate and malachite green in aqueous acidic solution (0.5 M sulfuric acid) enables trace amounts (0?1 × 10?5M) of phosphate to be determined. The molar absorptivity is 1.05 × 105 l mol?1 cm?1 at 620 nm. The complex was stabilized in solution by adding poly (vinyl alcohol). Other ions generally found in river waters did not interfere. Interference by silicate is less than that found in the corresponding malachite green molybdophosphate procedure; interference of arsenate is avoided by reduction with thiosulfate. The method is applied to the determination of μg l?1 amounts of phosphorus in river water; the results obtained were in good agreement with those obtained by an extraction-spectrophotometric method with malachite green. 相似文献
36.
Kenji Yamagata Fumi Okabe Hiroshi Maruoka Yoshinobu Tagawa 《Journal of heterocyclic chemistry》2005,42(4):543-549
The reaction of 2‐acylamino‐4,5‐dihydro‐3‐furancarbonitriles 1 with sodium iodide in N,N‐dimethyl‐formamide gave the corresponding 1‐acyl‐2‐oxo‐3‐pyrrolidinecarbonitriles 2 in good yields. Successive treatment of 1 with titanium(IV) chloride and potassium carbonate resulted in the formation of N‐acyl‐1‐cyanocyclopropanecarboxamides 4 . The same compounds 2 were also obtained by treatment of 4 with sodium iodide. The starting compounds 1 were synthesized by the reaction of 2‐amino‐4,5‐dihydro‐3‐furan‐carbonitrile with acyl chlorides in pyridine. 相似文献
37.
Hiroaki Imai Atsushi Tominaga Hiroshi Hirashima Motoyuki Toki Mamoru Aizawa 《Journal of Sol-Gel Science and Technology》1998,13(1-3):991-994
Modification of sol-gel derived indium oxide thin films using ultraviolet lasers was investigated. Irradiation by an ArF excimer (6.4 eV) and the fourth harmonic generation of a Nd : YAG laser (4.7 eV) was found to be effective in crystallization with a loss of hydroxyl groups and a decrease in the sheet resistance of the sol-gel films. Transparent crystalline indium oxide films were successfully obtained by 6.4 eV laser irradiation at fluences below 20 mJ/(cm2·shot), whereas degradation of the films was induced by a relatively high-fluence beam. 相似文献
38.
Hisamatsu Y Hasada K Amano F Tsubota Y Wasada-Tsutsui Y Shirai N Ikeda S Odashima K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(29):7733-7741
A new structure for an adenine-selective host molecule, featuring the pertinent link of five-six-five-membered heteroaromatic rings and two carbamoyl NH sites, was developed. This structure provides a correctly oriented array of complementary hydrogen bonding sites for the adenine nucleobase, which exploits both Watson-Crick and Hoogsteen-type interactions. The complexation with adenine nucleobases by multiple hydrogen bonding was supported by (1)H NMR spectroscopy. This type of host displayed high selectivity in complexation, with an accompanying fluorescent response to lipophilized adenosine in CHCl(3). Furthermore, a remarkably selective potentiometric response was attained for adenosine 5'-monophosphate over 5'-GMP, 5'-CMP, and 5'-UMP by using an ion-selective electrode with a PVC-supported solvent polymeric membrane. This indicates recognition of water-soluble nucleotide guests through the membrane-water interface. These findings are expected to form a reliable basis for the development of artificial sensing systems for mononucleotides in biological systems. 相似文献
39.
Aldehydes were found to be oxidized to the corresponding carboxylic acid in the presence of catalytic lithium bromide under photo-irradiation. 相似文献
40.
Yonehara F Kido Y Sugimoto H Morita S Yamaguchi M 《The Journal of organic chemistry》2003,68(17):6752-6759
GaCl(3) catalyzes the aromatic alkylation of naphthalene or phenanthrene using cycloalkanes. The C[bond]C formation predominantly takes place at the least hindered positions of the substrates, and equatorial isomers regarding the cycloalkane moiety are generally obtained. The reaction of bicyclo[4.4.0]decane and naphthalene occurs at the 2-position of naphthalene and at the 2- or 3-carbons of the cycloalkane, and the products possess a trans configuration at the junctures and an equatorial configuration at the naphthyl groups. Notably, cis-bicyclo[4.4.0]decane turns out to be much more reactive than the trans isomer, and a turnover number "TON" up to 20 based on GaCl(3) is attained. 1,2-Dimethylcyclohexane reacts similarly, and the cis isomer is more reactive than the trans isomer. Monoalkylcycloalkanes react at the secondary carbons provided that the alkyl group is smaller than tert-butyl. Adamantanes react at the tertiary 1-position. The alkylation reaction is considered to involve the C[bond]H activation of cycloalkanes with GaCl(3) at the tertiary center followed by the migration of carbocations and electrophilic aromatic substitution yielding thermodynamically stable products. The stereochemistry of the reaction reveals that GaCl(3) activates the equatorial tertiary C[bond]H rather than the axial tertiary C[bond]H. 相似文献