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81.
Koichi Mikami Tatsushi Murase Lili Zhai Susumu Kawauchi Yoshimitsu Itoh Shigekazu Ito 《Tetrahedron letters》2010,51(10):1371-8183
Highly enantio-enriched perfluoroalkyl amines are shown to be synthesized by perfluoroalkylation and asymmetric reduction of nitriles. Perfluoroalkylation of nitriles can be attained by the Lewis acidic perfluoroalkyl titanate reagents to give acyclic ketimines. Catalytic asymmetric hydrogenation of the acyclic ketimines affords the perfluoroalkyl amine products in up to 93% ee. 相似文献
82.
Hidetaka Kasai Taizo Kawauchi Xiao-Wei Zhang Takumi Kikegawa Tatsuo Okano 《Applied Surface Science》2009,256(4):984-986
We applied the time-domain analysis of nuclear resonant scattering (NRS) of X-rays for the study of the hydrogen-induced enhancement of atomic diffusion. The time-domain analysis of NRS is a powerful technique for studying diffusion processes on an atomic scale. The NRS measurement combined with high-pressure technique enables the direct measurement of self-diffusion processes under high hydrogen pressures. In this preliminary experiment, self-diffusion in 4 μm thick 57Fe foils at 0.8 GPa was investigated. The samples of the 57Fe were encapsulated with MgO or NaCl. Faster decays caused by diffusion of Fe atoms were observed in the time spectra of NRS at high temperatures. This enhancement of diffusion is believed to be the hydrogen-induced effect. In the present experiment, hydrogen should have been supplied to the samples by reaction with water originally adsorbed on NaCl/MgO powder particles. It was concluded that the diffusion of 57Fe atoms under high pressure can be studied by nuclear resonant scattering of X-rays using a compact cubic-anvil press. The NRS method can also be extended to the study of atomic diffusion in the subsurface region by doping 57Fe layer(s) at known depths. 相似文献
83.
[Structure: see text] We synthesized oligodeoxynucleotide (ODN, 3), which contains 4'-o-nitrobenzyloxythymidine (4) as a caged precursor of C4'-oxidized abasic site (1). Photoirradiation of 3 at 365 nm followed by amine treatment under neutral conditions afforded the lactam (2) efficiently. Duplexed ODN 3 was converted to 1 faster and more efficiently than single stranded 3, whereas amine treatment of 1 formed from single stranded 3 resulted in slightly faster lactam formation than with the duplex. 相似文献
84.
A gold-catalyzed alkylation of alcohols and aromatic compounds is described. The reaction of ortho-alkynylbenzoic acid alkyl esters with alcohols or aromatic compounds occurs in the presence of catalytic amounts of Ph3PAuCl and AgOTf under mild conditions to produce corresponding ethers or Friedel-Crafts alkylation products in good to high yields. The reaction likely proceeds through the gold-induced in situ construction of leaving groups and subsequent nucleophilic attack of alcohols or aromatic compounds. 相似文献
85.
In this article, we will review the phenomena on circularly-polarized-light (CPL)-induced chirality in polymeric systems with photochromophores in their side-chain or main-chain. In the side-chain polymeric systems, the photoinduced chirality arises from superstructural chirality, i.e., helix structure, via aggregating of achiral azobenzene molecules in side chains. On the other hand, in the main-chain polymeric system, the macroscopically induced chirality can originate from individual chirality of chromophores in their main-chain backbone. The CPL irradiation on polymeric films with photochromophores to produce macroscopic chirality has been realized as potentially useful in the development of optical-switching, optical-storage, and light-driven devices. 相似文献
86.
The analogy used to solve some thermoelastic problems is extended to include a region with an eccentric hole. The relation is shown to be a little more complicated in this case than in the one for the concentric hole. Three bending tests of an analogous thin plate are required. As an experimental proof, an eccentric circular region is considered and mental proof, an eccentric circular region is considered and the analogous thin plate is prepared. The heat-conduction equation is first solved to give the required temperature terms. The measured strains on the plate and the coefficients specified from the transverse loads and moments applied to the plate are combined effectively to get the estimated thermal stress. The experimentally estimated thermal stress of the region and the numerical result are shown to be in agreement.Paper was presented at V International Congress on Experimental Mechanics held in Montreal, Quebec, Canada on June 10–15, 1984. 相似文献
87.
Sonoko Kikuchi Kazuteru Kawauchi Masaru Kurosawa Hisashi Honjho Teruo Yagishita 《Analytical sciences》2005,21(3):197-198
The European Union has banned chromium(VI) compounds in electrical and electronic equipment (EEE), such as chromate conversion coating films. Chromium(III) compounds are not banned. Using Raman spectroscopy without any preparation, we distinguished chromium(VI) oxide from chromium(III) oxide and chromium(III) hydroxide in chromate conversion coating films. Raman bands of chromium(VI) oxide were detected in films at around 1000 and 500 cm(-1), while chromium(III) compounds generated no bands in the region between 2000 and 200 cm(-1). The analysis took about 1 min, whereas the usual diphenylcarbazide-colorimetric method for analyzing chromium(VI) compounds takes about 10 h. 相似文献
88.
Minoru Ashizawa Takuro Niimura Yan Yu Kazuma Tsuboi Hidetoshi Matsumoto Ryo Yamada Susumu Kawauchi Akihiko Tanioka Takehiko Mori 《Tetrahedron》2012,68(13):2790-2798
Dialkyl quarter- and quinquethiophenes end-capped with β-connected thiophenes are prepared, and the field-effect transistor (FET) properties are investigated. Molecular orbital calculation as well as the redox and optical measurements indicate that the β-isomers have low-lying HOMO levels and large energy gaps compared with the α-isomers. Molecular packing of the dihexylquaterthiophene with β-isomers consists of a typical herringbone motif analogous to the α-isomers. In the single crystal, the alkyl chains are extending in the tilted directions from the core molecular plane, but straightly extending in the thin films, resulting in even more perpendicular molecular arrangement to the substrate than the α-isomers. These β-isomers show p-type FET performance comparable to the corresponding α-isomers, whereas all new oligothiophenes show air stability better than the corresponding α-isomers. In particular, dihexylquinquethiophene with β-isomers has shown significantly improved air stability maintained over 270 days. This stabilization effect is ascribed to the low-lying HOMO level and the dense packing realized by perpendicular molecular arrangement. 相似文献
89.
Dr. Tomoki Ogoshi Daiki Yamafuji Takamichi Aoki Keisuke Kitajima Prof. Tada‐aki Yamagishi Yoshihiro Hayashi Dr. Susumu Kawauchi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(24):7493-7500
Planar chiral [2]‐ and [3]rotaxanes constructed from pillar[5]arenes as wheels and pyridinium derivatives as axles were obtained in high yield using click reactions. The process of rotaxane formation was diastereoselective; the obtained [2]rotaxane was a racemic mixture consisting of (pS, pS, pS, pS, pS) and (pR, pR, pR, pR, pR) forms of the per‐ethylated pillar[5]arene ( C2 ) wheel, and other possible types of the [2]rotaxane did not form. Isolation of the enantiopure [2]rotaxanes with one axle through (pS, pS, pS, pS, pS)‐ C2 or (pR, pR, pR, pR, pR)‐ C2 wheels was accomplished. Furthermore, pillar[5]arene‐based [3]rotaxane was successfully synthesized by attachment of two pseudo [2]rotaxanes onto a bifunctional linker. [3]Rotaxane formed in a 1:2:1 mixture with one axle threaded through two (pS, pS, pS, pS, pS)‐ C2 , one (pS, pS, pS, pS, pS)‐ C2 and one (pR, pR, pR, pR, pR)‐ C2 (meso form), or two (pR, pR, pR, pR, pR)‐ C2 wheels. The [3]rotaxane enantiomers and the meso form were successfully isolated using appropriate chiral HPLC column chromatography. The procedure developed in this study is the starting point for the creation of pillar[5]arene‐based interlocked molecules. 相似文献
90.