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81.
82.
Mutsumi Ohkubo 《Tetrahedron letters》2006,47(29):5181-5185
The Ti(II)-mediated cyclization of 3-methyloct-2-en-7-yn-1-ol derivatives 2 proceeded stereoselectively to afford 1-methyl-2-(1-alkylbut-3-enylidene)-1-vinylcyclopentanes 3 after treatment of the resulting alkenyltitaniums with allylbromide in the presence of CuCN, which was readily converted to 3a-methyl-2,3,3a,6-tetrahydro-1H-indenes 1 by the Ru-catalyzed ring-closing metathesis. 相似文献
83.
Mutsumi Kato Erika Hashimoto Masatoshi Kozaki Shuichi Suzuki Keiji Okada 《Tetrahedron letters》2012,53(3):309-312
Zinc porphyrin (1) containing 2,2′-bipyridyl units at the peripheral ends of both conjugated and alkyl side chains was prepared. Upon addition of Fe(II), the three bipyridyl terminals at both ends bind to Fe(II)s to form 1:2 complex 1·2Fe. The formation of 1·2Fe induced a large conformational change in the alkyl side chains and moderately affected the binding between the zinc porphyrin and an imidazole ligand. These results show that this method is useful for the communication between the porphyrin functional site and the remote metal-binding site. 相似文献
84.
The analytical performance of pyrolytic and non-pyrolytic boron nitride (PBN and NBN) platforms, attached to a commercially available graphite tube furnace, in electrothermal atomic absorption spectrometry (ETAAS) for Cd was studied. Although the tolerable pyrolysis temperature was 300 degrees C with the conventional pyrolytic graphite platform, it increased to 600 and 950 degrees C with the PBN and NBN platforms, respectively. The lifetime of the ceramic platform was 500 firings. The NBN platform provided an enhanced sensitivity with a better reproducibility than others. Using the NBN platform allowed the LOD, based on the variability of the blank (3sigma), to be 0.1 microg l(-1) within a seawater matrix (20,000 mg NaCl l(-1)) and a constant sensitivity in the range 0-30,000 mg NaCl l(-1). Good recovery in the range of 90-105% was observed for Cd (2.0 microg l(-1)) spiked into sea, estuarine and river water samples using the recommended procedure. This work proposes that using the NBN platform allows the direct monitoring and control of contaminated water for Cd by ETAAS without any chemical modification. 相似文献
85.
Dr. Eugenio Hernán Otal Prof. Dr. Hideki Tanaka Dr. Manuela Leticia Kim Prof. Dr. Juan Paulo Hinestroza Prof. Dr. Mutsumi Kimura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(26):7376-7382
The development of portable, reliable, and low-cost sensors for assessing the quality of natural water sources is of high relevance in developing countries as they can serve as an intermediate solution prior to the building of permanent potable water distribution infrastructure. These sensors should be simple to operate by non-trained operators and easy to manufacture locally. Lanthanide-based metal–organic frameworks (MOFs) offer a trustable platform due to their intense emission in regions of the visible spectra and their high sensitivity to fluorides in water. Cotton was chosen as a substrate due to its high hydrophilicity which, together with the highly porous nature of the MOF, allows for shorter reaction times. The modified cotton was characterized by XRD, SEM as well as XAFS, hence probing the presence of [Tb(BTC)6(H2O)] (Tb-BTC) attachment to cotton. Changes in the emission when Tb-BTC modified cotton was exposed to water and aqueous fluoride solutions were monitored as a function of time. Crystalline phase changes were identified that correlated to structural information. Finally, the Tb-BTC modified cotton was used to build a fluoride demonstrator sensor with a linear response of up to 10 mg L−1 and a limit of detection of 0.8 mg L−1, making it suitable for drinking water analysis under international regulations. 相似文献
86.
Masakazu Nishida Tomoko Tanaka Wataru Kanematsu 《Magnetic resonance in chemistry : MRC》2017,55(6):570-578
In order to investigate the effects of composite production and the role of the counter cation for metal phosphate conductors, changes in the solid‐state nuclear magnetic resonance (NMR) spectra and magnetic relaxation times caused by the removal of volatile products and water washing were examined for various metal pyrophosphate (MP2O7–MO2; M = Sn, Si, Ti, and Zr). Acidic species could be detected by 1H MAS NMR spectra for all the composites except ZrP2O7–ZrO2 that had the lowest conductivity. The 31P DD‐MAS NMR spectra for MP2O7–MO2 composites showed different signal patterns depending on the counter cations participating in the ion exchange as a result of different microstructures. Combinational analysis of 31P DD‐MAS and 31P CP‐MAS NMR spectra of the composites indicated that protonic bulk phosphates were observed at slightly lower fields than non‐protonic bulk phosphates in all of the MP2O7–MO2 composites. After water washing, the acidic species and the protonic bulk phosphates of MP2O7–MO2 composites disappeared or were reduced to trace amounts. The T1H values of the water‐washed composites lengthened because of removal of orthophosphoric acid, although the T1P values remained almost unchanged. The results of the solid‐state NMR studies suggest that the protonic bulk phosphates of MP2O7–MO2 composites do not generally distribute in the bulk but exist in the interface between excess H3PO4 and the bulk. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
87.
88.
(η2-Imine)Ti(O-i-Pr)2 complexes generated from arylaldehyde imines and a divalent titanium reagent, Ti(O-i-Pr)4/2i-PrMgCl, reacted with 3,3-diethoxypropyne to afford 2-arylpyrroles. 相似文献
89.
90.
Kobayashi H Kanematsu M Yoshida M Shishido K 《Chemical communications (Cambridge, England)》2011,47(26):7440-7442
The second-generation enantioselective total synthesis of aspergillide C, a new type of 14-membered macrolide isolated from a marine-derived fungus, has been accomplished in a longest linear sequence of 15 steps from a chiral building block in 19% overall yield employing the 6-exo-trig transannular oxy-Michael reaction as the key step. 相似文献