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Toshio Shimizu Kazuko Iwata Hideyuki Murakami Nobumasa Kamigata 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):457-458
Sulfur-containing cycloalkenes possessing disulfide units 1, 2, and 3 were obtained by oxidation of cis-disodium ethene-1,2-dithiolate, and their crystal structures were determined by the X-ray crystallographic analyses. Compound 1 was found to give the ring expansion product 3 in acetonitrile even at room temperature and also form reactive thioaldehyde under irradiation. 相似文献
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Kiyoshi Tanaka Yasuhiro Yamamoto Hiroto Obara Satoru Iwata 《Supramolecular chemistry》2013,25(4):347-352
5,15- cis -bis(Ureidophenyl)porphyrins have significant recognizing ability for p -benzoquinones through four-point hydrogen bonding. Although an unusual temperature-dependence of the complexation is observed with bis( N '-phenylureidophenyl) porphyrin, bis( N '-ethylureidophenyl)porphyrin shows a satisfactorily linear van't Hoff plot and recognizes an electron-rich p -benzoquinone such as tetramethyl- p -benzoquinone more effectively, which is ascribed to the large enthalpy change in the complex. 相似文献
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Yin Li Zsolt Csók László Kollár Koichi Iwata Erzsébet Szász 《Supramolecular chemistry》2013,25(6):374-378
2-Methylresorcinarene and its methylene-bridged cavitand derivative as host compounds were investigated in selective complexation of alkali metal ions as guests in methanol media by photoluminescence measurements. These host molecules possess either flexible (2-methylresorcinarene) or rigid (cavitand) molecular skeleton. The Benesi–Hildebrand method and the van't Hoff theory have been applied to determine the stability constants and the thermodynamic parameters, respectively. Considerable interactions between 2-methylresorcinarene and Li+ or Na+ ions have been observed while the rigid cavitand derivative can interact only with K+ or Cs+ ions. Neither the complexes of 2-methylresorcinarene with K+ or Cs+ nor those of the cavitand derivative with Li+ or Na+ ions are stable at room temperature in methanol media. Quantum-chemical investigations justified that only solvated Li+ and Na+ ions can form stable complexes with 2-methylresorcinarene while unsolvated K+ and Cs+ ions form stable complexes with the methylene-bridged cavitand. These results highlight that the stability of the guest solvation shell and its size could play a key role in the selectivity behaviour of host molecules. 相似文献
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We have developed asymmetric Mukaiyama aldol reactions of silicon enolates with aldehydes catalyzed by chiral FeII and BiIII complexes. Although previous reactions often required relatively harsh conditions, such as strictly anhydrous conditions, very low temperatures (?78 °C), etc., the reactions reported herein proceeded in the presence of water at 0 °C. To find appropriate chiral water‐compatible Lewis acids for the Mukaiyama aldol reaction, many Lewis acids were screened in combination with chiral bipyridine L1 , which had previously been found to be a suitable chiral ligand in aqueous media. Three types of chiral catalysts that consisted of a FeII or BiIII metal salt, a chiral ligand ( L1 ), and an additive have been discovered and a wide variety of substrates (silicon enolates and aldehydes) reacted to afford the desired aldol products in high yields with high diastereo‐ and enantioselectivities through an appropriate selection of one of the three catalytic systems. Mechanistic studies elucidated the coordination environments around the FeII and BiIII centers and the effect of additives on the chiral catalysis. Notably, both Brønsted acids and bases worked as efficient additives in the FeII‐catalyzed reactions. The assumed catalytic cycle and transition states indicated important roles of water in these efficient asymmetric Mukaiyama aldol reactions in aqueous media with the broadly applicable and versatile catalytic systems. 相似文献
47.
Application of 28Mg for characterization of Mg uptake in rice seedling under different pH conditions
N. I. Kobayashi N. Iwata T. Saito H. Suzuki R. Iwata K. Tanoi T. M. Nakanishi 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(1):531-534
The magnesium (Mg) uptake of rice seedlings treated with different pH solutions was investigated using tracer of 28Mg. The application of 28Mg enabled the determination of Mg uptake amount within 15 min of the different pH treatments. The uptake amount of 28Mg and its distribution in rice plants were determined by using the imaging plate. The result demonstrated that the Mg uptake amount was approximately 3 μmol/15 min per plant in 0.27 mM Mg solution at pH 5.6, and this uptake decreased by 30 % at lower pH conditions (pH 4.5). On the contrary, the pH 6.5 condition induced the Mg uptake activity to 4.4 μmol/15 min. The inverse relationship found between proton concentration in nutrient solution and the Mg uptake amount within 15 min of treatment demonstrated that the low pH condition could inhibit the Mg uptake activity as a consequence of the competition between Mg2+ and proton. It is concluded that under low pH conditions, regardless of other factors, there is a decrease of Mg uptake activity in rice roots. 相似文献
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The catalytic activities of the cationic synthetic flavin adduct 1 with various dendritic and non-dendritic 2,6-bis(acylamino)pyridines 2 were examined for the oxidation of organic sulfides with H2O2. The adduct of 5-ethyllumiflavinium perchlorate 1a with 2b–d bearing poly(benzyl ether) dendron units acts as an efficient organocatalyst for the oxidative transformation of sulfides to the corresponding sulfoxides under mild conditions. 相似文献
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