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排序方式: 共有261条查询结果,搜索用时 93 毫秒
191.
192.
Noriaki Fujita Kohsuke Mori Kohki Ebitani Kiyotomi Kaneda 《Tetrahedron letters》2006,47(29):5083-5087
Treatment of a hydrotalcite with an aqueous solution of rhodium trichloride results in a Rh-grafted hydrotalcite (Rh/HT) with monomeric Rh species on the surface, which successfully promoted 1,4-addition of organoboron reagents to α,β-unsaturated carbonyl compounds. Furthermore, this catalyst was reusable and was found to be applicable to a one-pot synthesis of 3,3-diarylnitrile. 相似文献
193.
Mori K Mitani Y Hara T Mizugaki T Ebitani K Kaneda K 《Chemical communications (Cambridge, England)》2005,(26):3331-3333
A zinc-based hydroxyapatite catalyst in conjunction with a Lewis base proved to be efficient for the coupling of CO2 and epoxide in the absence of additional organic solvents under an atmospheric CO2 pressure; the work-up procedure is straightforward and the catalyst could be reused without loss of catalytic activity and selectivity. 相似文献
194.
Isao Ikemoto Kikujiro Ishii Shuichi Kinoshita Takashi Fujikawa Haruo Kuroda 《Chemical physics letters》1976,38(3):467-470
Structures consisting of several peaks were clearly observed in the loss band regions of core electron peaks in the X-ray photoelectron spectra of KF, NaF and LiF. It is shown that, although these structures very much resemble the electron energy loss spectra of the salts obtained using an externally produced electron beam, the energies and intensities of some peaks are dependent upon the ionizing core levels. One peak definitely attributable to an intrinsic satellite was found in the loss band region of F 1s spectrum of each salt, which was concluded to be due to the shake-up process associated with F 2p → F 3p excitation. 相似文献
195.
196.
Mitsunori Oda Nguyen Chung Thanh Hisayoshi Fujikawa Shigeyasu Kuroda 《Tetrahedron》2007,63(43):10608-10614
Two title compounds, N,N,N′,N′-tetraphenyl-1,3-bis(5-aminothien-2-yl)azulene (3a) and 1,3-bis{5-(9-carbazolyl)thien-2-yl}azulene (3b), were synthesized from 1,3-di(2-thienyl)azulene (4) by a two-step sequence involving bromination and subsequent Pd-catalyzed amination. These compounds were characterized by spectroscopic analyses and the structure of 3a was determined by X-ray crystallographic analysis. Their HOMO energy levels were estimated using their electrochemical oxidation potentials, and these compounds were used as a hole-injecting material in organic light-emitting devices. The device with 3a showed greater durability than that with copper phthalocyanine. 相似文献
197.
Nucleophilic substitution reactions of alcohols with use of montmorillonite catalysts as solid Brønsted acids 总被引:1,自引:0,他引:1
Motokura K Nakagiri N Mizugaki T Ebitani K Kaneda K 《The Journal of organic chemistry》2007,72(16):6006-6015
We have developed an environmentally benign synthetic approach to nucleophilic substitution reactions of alcohols that minimizes or eliminates the formation of byproducts, resulting in a highly atom-efficient chemical process. Proton- and metal-exchanged montmorillonites (H- and Mn+-mont) were prepared easily by treating Na+-mont with an aqueous solution of hydrogen chloride or metal salt, respectively. The H-mont possessed outstanding catalytic activity for nucleophilic substitution reactions of a variety of alcohols with anilines, because the unique acidity of the H-mont catalyst effectively prevents the neutralization by the basic anilines. In addition, amides, indoles, 1,3-dicarbonyl compounds, and allylsilane act as nucleophiles for the H-mont-catalyzed substitutions of alcohols, which allowed efficient formation of various C-N and C-C bonds. The solid H-mont was reusable without any appreciable loss in its catalytic activity and selectivity. Especially, an Al3+-mont showed high catalytic activity for the alpha-benzylation of 1,3-dicarbonyl compounds with primary alcohols due to cooperative catalysis between a protonic acid site and a Lewis acidic Al3+ species in its interlayer spaces. 相似文献
198.
Oka K Yamada I Azuma M Takeshita S Satoh KH Koda A Kadono R Takano M Shimakawa Y 《Inorganic chemistry》2008,47(16):7355-7359
The magnetic properties of PbVO 3, a PbTiO 3-type perovskite with a large tetragonal distortion ( c/a = 1.229), were investigated. The temperature dependence of the measured magnetization of multidomain single-crystal samples showed a broad maximum centered around 180 K, indicating a two-dimensional antiferromagnetism. muSR measurement revealed the presence of a long-range order below 43 K. The two-dimensional magnetism is due to the ordering of d xy orbitals, which is thought to also be related to the large tetragonal distortion of PbVO 3. 相似文献
199.
Mohana Shivanna Ken-ichi Otake Shotaro Hiraide Takao Fujikawa Ping Wang Yifan Gu Hirotaka Ashitani Shogo Kawaguchi Yoshiki Kubota Minoru T. Miyahara Susumu Kitagawa 《Angewandte Chemie (International ed. in English)》2023,62(39):e202308438
Porous sorbents are materials that are used for various applications, including storage and separation. Typically, the uptake of a single gas by a sorbent decreases with temperature, but the relative affinity for two similar gases does not change. However, in this study, we report a rare example of “crossover sorption,” in which the uptake capacity and apparent affinity for two similar gases reverse at different temperatures. We synthesized two soft porous coordination polymers (PCPs), [Zn2(L1)(L2)2]n (PCP-1) and [Zn2(L1)(L3)2]n (PCP-2) (L1= 1,4-bis(4-pyridyl)benzene, L2=5-methyl-1,3-di(4-carboxyphenyl)benzene, and L3=5-methoxy-1,3-di(4-carboxyphenyl)benzene). These PCPs exhibits structural changes upon gas sorption and show the crossover sorption for both C2H2/CO2 and C2H6/C2H4, in which the apparent affinity reverse with temperature. We used in situ gas-loading single-crystal X-ray diffraction (SCXRD) analysis to reveal the guest inclusion structures of PCP-1 for C2H2, CO2, C2H6, and C2H4 gases at various temperatures. Interestingly, we observed three-step single-crystal to single-crystal (sc-sc) transformations with the different loading phases under these gases, providing insight into guest binding positions, nature of host–guest or guest-guest interactions, and their phase transformations upon exposure to these gases. Combining with theoretical investigation, we have fully elucidated the crossover sorption in the flexible coordination networks, which involves a reversal of apparent affinity and uptake of similar gases at different temperatures. We discovered that this behaviour can be explained by the delicate balance between guest binding and host–guest and guest-guest interactions. 相似文献
200.
Mizuki Yamada Mio Matsumura Yuki Murata Masatoshi Kawahata Kohki Saito Naoki Kakusawa Kentaro Yamaguchi Shuji Yasuike 《Tetrahedron》2017,73(18):2614-2622
The Cu-catalyzed azide-alkyne cycloaddition by the reaction of various ethynylstibanes with benzylazide in the presence of CuBr (5 mol%) under aerobic conditions led to the formation of trisubstituted 5-organostibano-1H-1,2,3-triazoles. Further, the acyl-induced deantimonation of 5-stibanotriazoles with acyl chlorides in the presence of N,N-dimethyl-4-aminopyridine and triethylamine afforded the corresponding trisubstituted 5-acyltriazoles in moderate-to-good yields. 相似文献