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1.
Naoki Ogiwara Hirokazu Kobayashi Patricia Concepcin Fernando Rey Hiroshi Kitagawa 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):11857-11862
We first studied the reactivity of H2O vapor in metal–organic frameworks (MOFs) with Pt nanocrystals (NCs) through the water–gas shift (WGS) reaction. A water‐stable MOF, UiO‐66, serves as a highly effective support material for the WGS reaction compared with ZrO2. The origin of the high catalytic performance was investigated using in situ IR spectroscopy. In addition, from a comparison of the catalytic activities of Pt on UiO‐66, where Pt NCs are located on the surface of UiO‐66 and Pt@UiO‐66, where Pt NCs are coated with UiO‐66, we found that the competitive effects of H2O condensation and diffusion in the UiO‐66 play important roles in the catalytic activity of Pt NCs. A thinner UiO‐66 coating further enhanced the WGS reaction activity of Pt NCs by minimizing the negative effect of slow H2O diffusion in UiO‐66. 相似文献
2.
Keiichi Tomishige Masazumi Tamura Yoshinao Nakagawa 《Chemical record (New York, N.Y.)》2019,19(7):1354-1379
Recent progress on the CeO2 catalyzed synthesis of organic carbonates, ureas, and carbamates from CO2+alcohols, CO2+amines, and CO2+alcohols+amines, respectively, is reviewed. The reactions of CO2 with alcohols and amines are reversible ones and the degree of the equilibrium limitation of the synthesis reactions is strongly dependent on the properties of alcohols and amines as the substrates. When the equilibrium limitation of the reaction is serious, the equilibrium conversion of the substrate and the yield of the target product is very low, therefore, the shift of the equilibrium reaction to the product side by the removal of H2O is essential in order to get the target product in high yield. One of the effective method of the H2O removal from the related reaction systems is the combination with the hydration of 2‐cyanopyridine to 2‐picolinamide, which is also catalyzed by CeO2. 相似文献
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Dr. Hirokazu Tsukamoto Saki Nakamura Akito Tomida Prof. Dr. Takayuki Doi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(55):12528-12532
Haouamines A, B, and their derivatives were synthesized via Suzuki–Miyaura coupling and three key cyclization reactions as follows: the newly developed palladium(0)-catalyzed arylative cyclization of phenylalanine-derived alkyne–aldehydes with 2-bromoarylboronic acid (an “anti-Wacker”-type cyclization); BF3 ⋅ OEt2-promoted Friedel–Crafts-type cyclization of symmetrical electron-rich aromatic rings adjacent to a tertiary allylic alcohol leading to the indeno-tetrahydropyridine skeleton; and (cyanomethyl)trimethylphosphonium iodide-mediated macrocyclization of amino alcohols to afford aza-paracyclophane precursors. The palladium-catalyzed reduction of mono- and di-triflate intermediates in the later stages enabled the alteration of both the position and number of hydroxyl groups on the C-ring. The instability of haouamine B was dramatically improved by salt formation with formic acid. An unambiguous evaluation of the cytotoxicity of the prepared haouamine derivative formates with and without hydroxyl groups at different positions on the C-ring indicated that the catechol structure in haouamine B produced weak cytotoxicity. 相似文献
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Mitsunori Fukaya Shota Nagamine Dr. Taro Ozaki Yaping Liu Miina Ozeki Taro Matsuyama Dr. Kazunori Miyamoto Prof. Dr. Hirokazu Kawagishi Prof. Dr. Masanobu Uchiyama Prof. Dr. Hideaki Oikawa Dr. Atsushi Minami 《Angewandte Chemie (International ed. in English)》2023,62(44):e202308881
Mushroom terpenoids are biologically and chemically diverse fungal metabolites. Among them, melleolides are representative sesquiterpenoids with a characteristic protoilludane skeleton. In this study, we applied a recently established hot spot knock-in method to elucidate the biosynthetic pathway leading to 1α-hydroxymelleolide. The biosynthesis of the sesquiterpene core involves the cytochrome P450 catalyzing stepwise hydroxylation of the Δ6-protoilludene framework and a stereochemical inversion process at the C5 position catalyzed by short-chain dehydrogenase/reductase family proteins. The highlight of the biosynthesis is that the flavoprotein Mld7 catalyzes an oxidation-triggered double-bond shift accompanying dehydration and acyl-group-assisted substitution with two different nucleophiles at the C6 position to afford the Δ7-protoilludene derivatives, such as melleolide and armillarivin. The complex reaction mechanism was proposed by DFT calculations. Of particular importance is that product distribution is regulated by interaction with the cell membrane. 相似文献
7.
Ruthenium‐Immobilized Periodic Mesoporous Organosilica: Synthesis,Characterization, and Catalytic Application for Selective Oxidation of Alkanes 下载免费PDF全文
Nobuhiro Ishito Dr. Hirokazu Kobayashi Dr. Kiyotaka Nakajima Yoshifumi Maegawa Dr. Shinji Inagaki Dr. Kenji Hara Prof. Dr. Atsushi Fukuoka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15564-15569
Periodic mesoporous organosilica (PMO) is a unique material that has a crystal‐like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl2(CO)3]2, is successfully immobilized onto 2,2’‐bipyridine (BPy) units of PMO to form a single‐site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru‐immobilized PMO oxidizes the tertiary C?H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C?H bonds, thereby exhibiting remarkably high regioselectivity. Moreover, the catalyst converts cis‐decalin to cis‐9‐decalol in a 63 % yield with complete retention of the substrate stereochemistry. The Ru catalyst can be separated by simple filtration and reused without loss of the original activity and selectivity for the oxidation reactions. 相似文献
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Supramolecular Polyelectrolyte Complexes of Bone Morphogenetic Protein‐2 with Sulfonated Polyrotaxanes to Induce Enhanced Osteogenic Differentiation 下载免费PDF全文
10.
Hirokazu Okuda Kohei Taniguchi Shinsuke Inagi Toshio Fuchigami 《Electroanalysis》2021,33(11):2296-2301
Electrochemical oxidation of O-(4-chlorobenzyl) S-methyl dithiocarbonate using tris(2,4-dibromophenyl)amine as a redox mediator was studied by cyclic voltammetric measurements. The triarylamine mediated anodic fluorodesulfurization of O-(4-chlorobenzyl) and O-(4-bromobenzyl) S-methyl dithiocarbonates provided 4-chloro- and 4-bromobenzyl fluorides, respectively in moderate yields. On the other hand, similar anodic fluorination of O-(2-phenethyl) S-octyl dithiocarbonate and O-(4-bromophenyl) S-methyl dithiocarbonate afforded 2-phenethyl trifluoromethyl ether and difluoro(methylthio)methyl 4-bromophenyl ether, respectively. Mechanistic aspects are also discussed. 相似文献