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21.
Naoki Kise Yosei Takenaga Yohei Ishikawa Yoichi Morikami Toshihiko Sakurai 《Tetrahedron letters》2012,53(15):1940-1945
The reductive coupling of N-methoxycarbonyl lactams with benzophenone by Zn-TiCl4 in THF gave cross-coupled products as cyclic α-diphenylidene-N-methoxycarbonylamines and ring-opening α,α-diphenyl-α-hydroxy-ω-(N-methoxycarbonyl)amino ketones selectively depending on the reduction conditions. The reductive coupling of N-methoxycarbonyl lactams with 9-fluorenone by Zn-TiCl4 gave cyclic α-(9H-fluoren-9-ylidene)-N-methoxycarbonylamines preferentially irrespective to the conditions. 相似文献
22.
Novel aryl-β-C-glucosidation method using glucal boronate was developed. This protocol can offer several advantages including use of non-toxic, easily handling glucal boronate as a crystalline solid and storable at room temperature for several months. Tri-O-methylnorbergenin (8,10-di-O-methylbergenin), an anti-HIV active bergenin derivative, was concisely synthesized by application of the aryl-β-C-glucosidation method. 相似文献
23.
O1s core‐electron binding energies (CEBE) of the atomic oxygens on different Ag surfaces were investigated by the symmetry adapted cluster‐configuration interaction (SAC‐CI) method combined with the dipped adcluster model, in which the electron exchange between bulk metal and adsorbate is taken into account properly. Electrophilic and nucleophilic oxygens (Oelec and Onuc) that might be important for olefin epoxidation in a low‐oxygen coverage condition were focused here. We consider the O1s CEBE as a key property to distinguish the surface oxygen states, and series of calculation was carried out by the Hartree–Fock, Density functional theory, and SAC/SAC‐CI methods. The experimental information and our SAC/SAC‐CI results indicate that Oelec is the atomic oxygen adsorbed on the fcc site of Ag(111) and that Onuc is the one on the reconstructed added‐row site of Ag(110) and that one‐ and two‐electron transfers occur, respectively, to the Oelec and Onuc adclusters from the silver surface. © 2013 Wiley Periodicals, Inc. 相似文献
24.
Shuntaro Matsuta Noriaki Shima Hidenao Kakehashi Akari Ishikawa Ryutaro Asai Atsushi Nitta Misato Wada Shihoko Nakano Hiroe Kamata Yoshio Nishiyama Hirohisa Nagatani Hisanori Imura Munehiro Katagi 《Journal of mass spectrometry : JMS》2020,55(9)
Various cathinone‐derived designer drugs (CATs) have recently appeared on the drug market. This study examined the mechanism for the generation of dehydrated ions for CATs during electrospray ionization collision‐induced dissociation (ESI‐CID). The generation mechanism of dehydrated ions is dependent on the amine classification in the cathinone skeleton, which is used in the identification of CATs. The two hydrogen atoms eliminated during the dehydration of cathinone (primary amine) and methcathinone (secondary amine) were determined, and the reaction mechanism was elucidated through the deuterium labeling experiments. The hydrogen atom bonded to the amine nitrogen was eliminated with the proton added during ESI, in both of the tested compounds. This provided evidence that CATs with tertiary amine structures (such as dimethylcathinone and α‐pyrrolidinophenones [α‐PPs]) do not undergo dehydration. However, it was shown that the two major tertiary amine metabolites (1‐OH and 2″‐oxo) of CATs generate dehydrated ions in ESI‐CID. The dehydration mechanisms of the metabolites of α‐pyrrolidinobutiophenone (α‐PBP) belongs to α‐PPs were also investigated. Stable‐isotope labeling showed the dehydration of the 1‐OH metabolite following a simple mechanism where the hydroxy group was eliminated together with the proton added during ESI. In contrast, the dehydration mechanism of the 2″‐oxo metabolite involved hydrogen atoms in three or more locations along with the carbonyl group oxygen, indicating that dehydration occurred via multiple mechanisms likely including the rearrangement reaction of hydrogen atoms. These findings presented herein indicate that the dehydrated ions in ESI‐CID can be used for the structural identification of CATs. 相似文献
25.
Mechanically induced C−C bond formation was demonstrated by the laser driven shock wave generated in liquid normal alkanes at room temperature. Gas chromatography mass spectrometry analysis revealed the dehydrogenation condensation between two alkane molecules, for seven normal alkanes from pentane to undecane. Major products were identified to be linear and branched alkane molecules with double the number of carbons, and exactly coincided with the molecules predicted by supposing that a C−C bond was formed between two starting molecules. The production of the alkane molecules showed that the C−C bond formation occurred almost evenly at all the carbon positions. The dependence of the production on the laser pulse energy clearly indicated that the process was attributed to the shock wave. The C−C bond formation observed was not a conventional passive chemical reaction but an unprecedented active reaction. 相似文献
26.
Jie Zhu Dr. Ryota Osuga Prof. Ryo Ishikawa Prof. Naoya Shibata Prof. Yuichi Ikuhara Prof. Junko N. Kondo Prof. Masaru Ogura Prof. Jihong Yu Prof. Toru Wakihara Prof. Zhendong Liu Prof. Tatsuya Okubo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19837-19842
Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM-5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn-ZSM-5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity. 相似文献
27.
Keiichiro Ishikawa Nobuyasu Hanari Yoshitaka Shimizu Toshihide Ihara Akira Nomura Masahiko Numata Takashi Yarita Kenji Kato Koichi Chiba 《Accreditation and quality assurance》2011,16(6):311-322
Purity assay of high-purity materials (HPMs) of phthalic acid esters (PAEs) was carried out by means of a mass balance method.
In this method, chromatographic methods such as gas chromatography-flame ionization detector (GC-FID) and/or high-performance
liquid chromatography (HPLC) in combination with other methods such as Karl-Fischer (KF) titration and vacuum evaporation
(VE) were applied. The sum of the impurities estimated by these methods allowed the estimation of the purity of the main component
by difference. Seven PAEs with varying side chain structures and levels of impurities were analysed on a systematic way in
which impurities were classified into several groups in terms of their abundance, availability of qualitative information
and availability of authentic compounds, etc. The absolute quantity of each impurity was determined by GC-FID and/or HPLC
based on the calibration made by the authentic compounds of impurities whenever available. The purities in mass fraction of
these PAEs were certified at the National Metrology Institute of Japan (NMIJ), and the PAEs were registered as primary reference
materials playing an essential role in linking the metrological traceability of the Japan Calibration Service System (JCSS)
to the International System of Units (SI). 相似文献
28.
29.
Miki ItoFujiko Konno Takuya KumamotoNoriyuki Suzuki Masatoshi KawahataKentaro Yamaguchi Tsutomu Ishikawa 《Tetrahedron》2011,67(41):8041-8049
Both enantiomers of chelidonine, a B/C-cis-11-hydroxyhexahydrobenzo[c]phenanthridine alkaloid, were synthesized by manipulation of the B/C-dehydro ring juncture of benzo[c]phenanthridine skeleton using Sharpless asymmetric dihydroxylation and stereospecific catalytic hydrogenation after introduction of oxygen functions on the C ring as key reaction steps for the construction of stereogenic centers. 相似文献
30.