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31.
Organolanthanide complexes of the type Cp'(2)LnCH(SiMe(3))(2) (Cp' = eta(5)-Me(5)C(5); Ln = La, Nd, Sm, Lu) and Me(2)SiCp' '(2)LnCH(SiMe(3))(2) (Cp' ' = eta(5)-Me(4)C(5); Ln = Nd, Sm, Lu) serve as efficient precatalysts for the regioselective intermolecular hydroamination of alkynes R'Ctbd1;CMe (R' = SiMe(3), C(6)H(5), Me), alkenes RCH=CH(2) (R = SiMe(3), CH(3)CH(2)CH(2)), butadiene, vinylarenes ArCH=CH(2) (Ar = phenyl, 4-methylbenzene, naphthyl, 4-fluorobenzene, 4-(trifluoromethyl)benzene, 4-methoxybenzene, 4-(dimethylamino)benzene, 4-(methylthio)benzene), di- and trivinylarenes, and methylenecyclopropanes with primary amines R' 'NH(2) (R' ' = n-propyl, n-butyl, isobutyl, phenyl, 4-methylphenyl, 4-(dimethylamino)phenyl) to yield the corresponding amines and imines. For R = SiMe(3), R = CH(2)=CH lanthanide-mediated intermolecular hydroamination regioselectively generates the anti-Markovnikov addition products (Me(3)SiCH(2)CH(2)NHR' ', (E)-CH(3)CH=CHCH(2)NHR' '). However, for R = CH(3)CH(2)CH(2), the Markovnikov addition product is observed (CH(3)CH(2)CH(2)CHNHR' 'CH(3)). For internal alkynes, it appears that these regioselective transformations occur under significant stereoelectronic control, and for R' = SiMe(3), rearrangement of the product enamines occurs via tautomerization to imines, followed by a 1,3-trimethylsilyl group shift to stable N-SiMe(3)-bonded CH(2)=CMeN(SiMe(3))R' ' structures. For vinylarenes, intermolecular hydroamination with n-propylamine affords the anti-Markovnikov addition product beta-phenylethylamine. In addition, hydroamination of divinylarenes provides a concise synthesis of tetrahydroisoquinoline structures via coupled intermolecular hydroamination/subsequent intramolecular cyclohydroamination sequences. Intermolecular hydroamination of methylenecyclopropane proceeds via highly regioselective exo-methylene C=C insertion into Ln-N bonds, followed by regioselective cyclopropane ring opening to afford the corresponding imine. For the Me(2)SiCp' '(2)Nd-catalyzed reaction of Me(3)SiCtbd1;CMe and H(2)NCH(2)CH(2)CH(2)CH(3), DeltaH() = 17.2 (1.1) kcal mol(-)(1) and DeltaS() = -25.9 (9.7) eu, while the reaction kinetics are zero-order in [amine] and first-order in both [catalyst] and [alkyne]. For the same substrate pair, catalytic turnover frequencies under identical conditions decrease in the order Me(2)SiCp' '(2)NdCH(SiMe(3))(2) > Me(2)SiCp' '(2)SmCH(SiMe(3))(2) > Me(2)SiCp' '(2)LuCH(SiMe(3))(2) > Cp'(2)SmCH(SiMe(3))(2), in accord with documented steric requirements for the insertion of olefinic functionalities into lanthanide-alkyl and -heteroatom sigma-bonds. Kinetic and mechanistic evidence argues that the turnover-limiting step is intermolecular C=C/Ctbd1;C bond insertion into the Ln-N bond followed by rapid protonolysis of the resulting Ln-C bond. 相似文献
32.
33.
Chul-Joong Kim Hyeon-Yeol Ryu Somin Lee Han-Joo Lee Yoon-Soek Chun Jong-Kyu Kim Chang-Yeon Yu Bimal Kumar Ghimire Jae-Geun Lee 《Molecules (Basel, Switzerland)》2021,26(10)
Wild ginseng has better pharmacological effects than cultivated ginseng. However, its industrialization is limited by the inability to grow wild ginseng on a large scale. Herein, we demonstrate how to optimize ginseng production through cultivation, and how to enhance the concentrations of specific ginsenosides through fermentation. In the study, we also evaluated the ability of fermented cultured wild ginseng root extract (HLJG0701-β) to inhibit acetylcholinesterase (AChE), as well as its neuroprotective effects and antioxidant activity. In in vitro tests, HLJG0701-β inhibited AChE activity and exerted neuroprotective and antioxidant effects (showing increased catalyst activity but decreased reactive oxygen species concentration). In in vivo tests, after HLJG0701-β was orally administered at doses of 0, 125, 250, and 500 mg/kg in an animal model of memory impairment, behavioral evaluation (Morris water maze test and Y-maze task test) was performed. The levels of AChE, acetylcholine (ACh), blood catalase (CAT), and malondialdehyde (MDA) in brain tissues were measured. The results showed that HLJG0701-β produced the best results at a dose of 250 mg/kg or more. The neuroprotective mechanism of HLJG0701-β was determined to involve the inhibition of AChE activity and a decrease in oxidative stress. In summary, both in vitro and in vivo tests confirmed that HJG0701-β administration can lead to memory improvement. 相似文献
34.
Soo Chool Lee Min Sun Cho Suk Yong Jung Chong Kul Ryu Jae Chang Kim 《Adsorption》2014,20(2-3):331-339
A range of potassium-based alumina sorbents were fabricated by impregnation of alumina with K2CO3 to examine the effects of the structural and textural properties of alumina on the CO2 sorption and regeneration properties. Alumina materials, which were used as supports, were prepared by calcining alumina at various temperatures (300, 600, 950, and 1,200 °C). The CO2 sorption and regeneration properties of these sorbents were examined during multiple tests in a fixed-bed reactor in the presence of 1 vol% CO2 and 9 vol% H2O. The regeneration capacities of the potassium-based alumina sorbents increased with increasing calcination temperature of alumina. The formation of KHCO3 increased with increasing calcination temperature during CO2 sorption, whereas the formation of KAl(CO3)(OH)2, which is an inactive material, decreased. These results is due to the fact that the structure of alumina by the calcination temperature is related directly to the formation of the by-product [KAl(CO3)(OH)2]. The structure of alumina plays an important role in enhancing the regeneration capacity of the potassium-based alumina sorbent. Based on these results, a new potassium-based sorbent using δ-Al2O3 as a support was developed for post-combustion CO2 capture. This sorbent maintained a high CO2 capture capacity of 88 mg CO2/g sorbent after two cycles. In particular, it showed a faster sorption rate than the other potassium-based alumina sorbents examined. 相似文献
35.
Sayoko Nagashima Shota Furukawa Satoshi Kamiguchi Ryu Kajio Hiroshi Nagashima Aritomo Yamaguchi Masayuki Shirai Hideki Kurokawa Teiji Chihara 《Journal of Cluster Science》2014,25(5):1203-1224
A series of molecular rhenium sulfide clusters [Re6S8(OH)6?n (H2O) n ](4?n)? (n = 0, 2, 4, 6) catalyze dehydrogenation of alcohols, and hydrogenation of ketones and olefins in a hydrogen stream at 350 °C. The catalytic activities of the dianionic and neutral clusters (n = 2, 4) are lower than those of tetraanionic and dicationic clusters (n = 0, 6) for all the reactions. When 1,4-butanediol is allowed to react over K4[Re6S8(OH)6], dehydrogenation proceeds to yield 2-hydroxytetrahydrofuran and successively γ-butyrolactone above 300 °C. Over [Re6S8(H2O)6]SO4 dehydration proceeds to yield tetrahydrofuran above 250 °C. The thermal activation mechanisms of these clusters were studied by powder X-ray diffraction analyses, Raman spectrometry, extended X-ray absorption fine structure spectrometry, thermogravimetry, and differential thermal analyses. The catalytically active site of K4[Re6S8(OH)6] is an uncoordinated metal site (Lewis acid site) developed by the loss of a water molecule from two hydroxo ligands. The active site of [Re6S8(H2O)6]SO4 is a Brønsted acid site; the anhydrous aqua cluster dication disproportionates to a hydroxo cluster monocation and a proton. Both of the octahedral cluster frameworks are retained up to 500 °C. 相似文献
36.
Dr. Nguyen Van Nghia Dr. Saibal Jana Surendran Sujith Ji Yeon Ryu Prof. Junseong Lee Prof. Sang Uck Lee Prof. Min Hyung Lee 《Angewandte Chemie (International ed. in English)》2018,57(38):12483-12488
An approach to the design of nido‐carborane‐based luminescent compounds that can exhibit thermally activated delayed fluorescence (TADF) is proposed. 7,8‐Dicarba‐nido‐undecaboranes (nido‐carboranes) having various 8‐R groups (R=H, Me, i‐Pr, Ph) are appended to the meta or para position of the phenyl ring of the dimesitylphenylborane (PhBMes2) acceptor, forming donor–acceptor compounds (nido‐ m1 – m4 and nido‐ p1 – p4 ). The bulky 8‐R group and meta substitution of the nido‐carborane are essential to attain a highly twisted arrangement between the donor and acceptor moieties, leading to a very small energy splitting between the singlet and triplet excited states (ΔEST <0.05 eV for nido‐ m2 , ‐ m3 , and ‐ p3 ). These compounds exhibit efficient TADF with microsecond‐range lifetimes. In particular, nido‐ m2 and ‐ m3 display aggregation‐induced emission (AIE) with TADF properties. 相似文献
37.
Ai Ito Takamasa Amaki Ayako Ishii Kazuo Fukuda Ryu Yamasaki Iwao Okamoto 《Tetrahedron letters》2018,59(45):3994-3998
Aromatic amides bearing 2-azulenyl group on the amide nitrogen were synthesized and their structures were investigated. The π-electron density of the N-aryl group was found to influence the cis-trans conformational preferences of these compounds in solution. X-ray crystallography revealed that the plane of the 2-azulenyl ring has a strong tendency to lie coplanar with the amide plane when the azulene group is located on the same side as the amide oxygen atom. 相似文献
38.
Ho Jin Park Jong Ho Kim J.J. Yoon J.S. Son D.Y. Lee H.H. Ryu Minhyon Jeon J.Y. Leem 《Journal of Crystal Growth》2007,300(2):319-323
The effects of multi-step rapid thermal annealing (RTA) for the self-assembled InAs quantum dots (QDs), which were grown by a molecular beam epitaxy (MBE), were investigated through photoluminescence (PL) and transmission electron microscopy (TEM). Postgrowth multi-step RTA was used to modify the structural and optical properties of the self-assembled InAs QDs. Postgrowth multi-step RTAs are as follows: one step (20 s at 750 °C); two step (20 s at 650 °C, 20 s at 750 °C); three step (30 s at 450 °C, 20 s at 650 °C, 20 s at 750 °C). It is found that significant narrowing of the luminescence linewidth (from 132 to 31 meV) from the InAs QDs occurs together with about 150 meV blueshift by two-step annealing, compared to as-grown InAs QDs. Observation of transmission electron microscopy (TEM) shows the existence of the dots under one- and two-step annealing but the disappearance of the dots by three-step annealing. Comparing with the samples under only one-step annealing, we demonstrate a significant enhancement of the interdiffusion in the dot layer under multi-step annealing. 相似文献
39.
Takeshi Kimura Shinya Ito Takashi Sasaki Satoshi Ogawa Ryu Sato Yasushi Kawai 《Heteroatom Chemistry》2008,19(4):394-401
4,9‐Diethyl[1,4]dihydrodithiino[5,6‐f]benzotrithiole (DTBT) gave a radical cation, DTBT(•+), and a dication, DTBT(2+), on treatment with a single‐electron oxidizing reagent. Both compounds showed an ESR signal, whereas the dication, generated by this procedure, was silent for 1H NMR. Hydrolysis of DTBT(2+) gave DTBT 1‐oxide (DTBT 1‐O) and 2‐oxide (DTBT 2‐O) together with DTBT and a mixture of several dioxides. A singlet‐state dication, DTBT(2+)‐S, which was generated upon treatment of DTBT 5‐oxide (DTBT 5‐O) with concentrated D2SO4, was detected by 1H and 13C NMR. After 20 h, the NMR signals disappeared while the solution was active for ESR. The results suggest that (i) a species generated from DTBT by oxidation with the single‐electron oxidizing reagent is a triplet‐state dication, DTBT(2+)‐T, and (ii) DTBT(2+)‐S, initially generated, gradually isomerizes to DTBT(2+)‐T in the solution, and DTBT(2+)‐T forms a partial spin pair. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:394–401, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20445 相似文献
40.
Seong Ho Ryu 《Liquid crystals》2016,43(13-15):1951-1972
ABSTRACTThe orientation control of liquid crystal (LC) phases is essential for fundamental studies as well as practical applications. Surface treatment and topographic confinement have emerged as two of the most effective tools to control ordering and orientation of various types of LC phases. This review is intended to give an overview of the LC phases controlled in confined geometries at micro- and nanometre scales, in which the orientation control methods and the effective analytical techniques will be covered. Finally, the review closes with the applications using such confined LC phases. 相似文献