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741.
Dr. Motoki Ito Haruna Yamazaki Aguri Ito Ryuhei Oda Moeka Komiya Dr. Kazuhiro Higuchi Prof. Dr. Shigeo Sugiyama 《European journal of organic chemistry》2023,26(31):e202300458
We have developed an improved method for generating aryne from o-triazenylarylboronic acids. Unlike the previous method that required excess o-triazenylarylboronic acids as aryne precursors, we used corresponding boronates as limiting reagents, which resulted in high yields. By combining the formation of boronates and aryne generation through silica gel treatment in one-pot, we were able to effectively use a wide range of o-triazenylarylboronic acids in reactions with various arynophiles. This one-pot method was particularly suitable for transforming complex aryne precursors with different functional groups. 相似文献
742.
Effect of reactive oxygen species generated with ultraviolet lamp and plasma on polyimide surface modification
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Takahiro Kondo Ryota Watanabe Yuta Shimoyama Kazuho Shinohe Sergei A. Kulinich Satoru Iwamori 《Surface and interface analysis : SIA》2017,49(11):1069-1077
Understanding the effect of reactive oxygen species (ROS), such as singlet oxygen molecule and atomic oxygen, on polyimide (PI) film properties, such as wettability, morphology, and chemical bonding state, is essential for further development of PI‐based surfaces. We investigated the effect of different ROS generated during ultraviolet (UV) and plasma treatment in oxygen gas on surface modification of Kapton PI. Different surface modification techniques, UV and plasma treatment, are known to generate different ROS. In this work, we demonstrate the effect of different ROS on PI surface modification. From the diagnostics of ROS by means of electron spin resonance and optical emission spectroscopy, we confirmed that during UV treatment, excited singlet oxygen molecules are the main ROS, while plasma treatment mainly generated atomic oxygen. The wettability of PI surface treated by UV and plasma resulted in hydrophilic PI surfaces. XPS results show that the wettability of PI samples is mainly determined by their surface O/C ratio. However, chemical bonding states were different: while UV treatment tended to generate C=O bonds, while plasma treatment tended to generate both C―O and C=O bonds. Singlet oxygen molecules are concluded to be the main oxidant during UV treatment, and their main reaction with PI was concluded to be of the addition type, leading to an increase of C=O groups on the surface of PI film. Meanwhile, atomic oxygen species were the main oxidant during plasma treatment, reacting with the PI surface through both etching and addition reaction, resulting in a wider variety of bonds, including both C―O and C=O groups. 相似文献
743.
Polycyclic N‐Heterocyclic Compounds. Part 84: Reaction of N‐(pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidin‐4‐yl)amidines or N‐(pyrido[2′,3′:4,5]furo[3,2‐d]pyrimidin‐4‐yl)amidines with Hydroxylamine Hydrochloride
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Kensuke Okuda Ryota Ide Naoto Uramaru Takashi Hirota 《Journal of heterocyclic chemistry》2015,52(3):880-887
The reactions of nine N‐(pyrido[3′,2′:4,5]thieno[3,2‐d]pyrimidin‐4‐yl)amidines ( 3 ) with hydroxylamine hydrochloride produced new cyclization products. These were formed via ring cleavage of the pyrimidine component followed by a 1,2,4‐oxadiazole‐forming ring closure to give N‐[2‐([1,2,4]oxadiazol‐5‐yl)thieno[2,3‐b]pyridin‐3‐yl]formamide oximes ( 11 ). Reaction of six N‐(pyrido[2′,3′:4,5]furo[3,2‐d]pyrimidin‐4‐yl)amidines ( 12 ) with hydroxylamine hydrochloride gave similar results. Effects of the newly synthesized compounds on pentosidine formation were also evaluated. 相似文献
744.
Dr. Tsuyoshi Mita Yuki Higuchi Prof. Dr. Yoshihiro Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16391-16394
Various allylic alcohols were carboxylated in the presence of a catalytic amount of PdCl2 and PPh3 using ZnEt2 as a stoichiometric transmetalation agent under a CO2 atmosphere (1 atm). This carboxylation proceeded in a highly regioselective manner to afford branched carboxylic acids predominantly. The β,γ‐unsaturated carboxylic acid thus obtained was successfully converted into an optically active γ‐butyrolactone, a known intermediate of (R)‐baclofen. 相似文献
745.
Prof. Ying‐Wu Lin Dr. Satoshi Nagao Mohan Zhang Dr. Yasuhito Shomura Prof. Yoshiki Higuchi Prof. Shun Hirota 《Angewandte Chemie (International ed. in English)》2015,54(2):511-515
Protein design is a useful method to create novel artificial proteins. A rational approach to design a heterodimeric protein using domain swapping for horse myoglobin (Mb) was developed. As confirmed by X‐ray crystallographic analysis, a heterodimeric Mb with two different active sites was produced efficiently from two surface mutants of Mb, in which the charges of two amino acids involved in the dimer salt bridges were reversed in each mutant individually, with the active site of one mutant modified. This study shows that the method of constructing heterodimeric Mb with domain swapping is useful for designing artificial multiheme proteins. 相似文献
746.
Efficient Synthesis,Structure, and Complexation Studies of Electron‐Donating Thiacalix[n]dithienothiophene
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Ryota Inoue Dr. Masashi Hasegawa Prof. Tohru Nishinaga Dr. Kenji Yoza Prof. Yasuhiro Mazaki 《Angewandte Chemie (International ed. in English)》2015,54(9):2734-2738
A series of thiacalix[n]dithiothiophenes (n=4–10) was prepared by a facile method and X‐ray analysis was used to determine the molecular structures of square‐ (4‐mer) and pentagonal‐shaped macrocycles (5‐mer). In the cyclic voltammograms, reversible multielectron redox processes, which are due to electronic delocalization, were observed at low oxidation potentials. The cyclic 4‐mer acted as a “Janus‐head” cavitand for two C60 molecules, whereas the 5‐ and 6‐mer formed stable 1:1 complexes with C60 . 相似文献
747.
祝向荣 沈鸿烈 沈勤我 李铁 邹世昌 Koichi Tsukamoto Mamoru Okutomi Takeshi Yanagisaw Noboru Higuchi 《物理学报》1999,48(13):40-46
用固相反应法制备了二元掺杂的镧锰氧化物La0.67(Ca0.6Ba0.4)0.33MnOz(LCBMO)立方多晶体材料,研究了其磁特性和庞磁电阻特性,并与用类似方法制备的一元掺杂的La0.67Ca0.33MnOz(LCMO)及La0.67Ba0.33MnOz(LBMO)的庞磁电阻特性进行了比较.研究表明,LCBMO的居里温度TC为312K,介于LCMO和LBMO的TC(分别为280,362K)之间,其金属-半导体转变温度Tp和μ0H=0.6T下的磁电阻(MR)峰值温度Tm分别为306,298K,接近于其TC,也介于LCMO和LBMO的Tp和Tm之间.μ0H=0.6T下,在各自的Tm处,LCMO,LCBMO和LBMO的庞磁电阻值分别达到41%,24.7%和8%,但在室温(300K)处,LCBMO的MR值仍达到20%,远大于LCMO和LBMO的值(分别为2.0%和2.4%).研究还发现,在温度远低于Tm时,LCMO仍保持一定的磁电阻效应,而LCBMO和LBMO的磁电阻温度降低而增加,这些低温磁电阻特性与材料的结构特征(如晶界和致密度)有关.
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748.
We have investigated, in terms of the Cohen-Turnbull theory, a relationship for polycarbonate (PC) glasses between average stress relaxation times, <to, and average free volume sizes, 〈vf〉, obtained from positron annihilation lifetime spectroscopy. This examination suggests that the minimum free volume required for stress relaxation, v*, decreases with decreasing temperature and that, near the glass transition temperature, only a subset of extremely large free volume elements contributes to the stress relaxation of PC glasses. This suggestion is consistent with the idea that near the glass transition temperature, the viscoelastic response is dominated by large-scale, main-chain motion, whereas at lower temperature it is controlled by local motion. Moreover, comparison with the v* value estimated from gas diffusivity through various PC species at room temperature shows that the required free volume size for stress relaxation in the glass transition region is much larger than that for gas diffusion. Previously we showed that the Doolittle equation fails to correlate viscoelastic relaxation times of polymer glasses with changing temperature; determining the free volume fraction, h, from theoretical analysis of volume recovery data and theory, the Doolittle equation is shown to be valid in PC above 135°C (Tg - 14°C) irrespective of temperature and physical aging times. This result supports the idea suggested in the previous article that, as glassy polymers approach the transition region, viscoelastic properties increasingly tend to be controlled by free volume. © 1996 John Wiley & Sons, Inc. 相似文献
749.
Kanta Ogawa Ryota Sakamoto Chengchao Zhong Hajime Suzuki Kosaku Kato Osamu Tomita Kouichi Nakashima Akira Yamakata Takashi Tachikawa Akinori Saeki Hiroshi Kageyama Ryu Abe 《Chemical science》2022,13(11):3118
Separation of photoexcited charge carriers in semiconductors is important for efficient solar energy conversion and yet the control strategies and underlying mechanisms are not fully established. Although layered compounds have been widely studied as photocatalysts, spatial separation between oxidation and reduction reaction sites is a challenging issue due to the parallel flow of photoexcited carriers along the layers. Here we demonstrate orthogonal carrier flow in layered Bi4NbO8Cl by depositing a Rh cocatalyst at the edges of nanoplates, resulting in spatial charge separation and significant enhancement of the photocatalytic activity. Combined experimental and theoretical studies revealed that lighter photogenerated electrons, due to a greater in-plane dispersion of the conduction band (vs. valence band), can travel along the plane and are readily trapped by the cocatalyst, whereas the remaining holes hop perpendicular to the plane because of the anisotropic crystal geometry. Our results propose manipulating carrier flow via cocatalyst deposition to achieve desirable carrier dynamics for photocatalytic reactions in layered compounds.An efficient spatial separation of photoexcited carriers is demonstrated in a layered-oxyhalide nanoplate by controlling the direction of carrier flows upon Rh cocatalyst loading, which leads to drastic photocatalytic H2 evolution activity. 相似文献
750.