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211.
Yasuaki Nakayama Ruriko Sekiya Hiroki Oishi Naoto Hama Miki Yamazaki Dr. Takaaki Sato Prof. Dr. Noritaka Chida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12052-12058
This article describes the details of two new types of Overman rearrangement from allylic vicinal diols. Starting from identical diols, both bis(imidate)s and cyclic orthoamides were selectively synthesized by simply changing the reaction conditions. Whilst exposure of the bis(imidate)s to thermal conditions initiated the double Overman rearrangement to introduce two identical nitrogen groups in a single operation (the cascade‐type Overman rearrangement), the reaction of cyclic orthoamides resulted in a single rearrangement (the orthoamide‐type Overman rearrangement). The newly generated allylic alcohols from the orthoamide‐type reaction can potentially undergo a variety of further transformations. For instance, we demonstrated an Overman/Claisen sequence in one pot. The most conspicuous feature of this method is that it offers precise control over the number of Overman rearrangements from the same allylic vicinal diols. This method also excludes the tedious protecting‐group manipulations of the homoallylic alcohols, which are necessary in conventional Overman rearrangements. All of the performed rearrangements proceeded in a completely diastereoselective fashion through a chair‐like transition state. 相似文献
212.
Nine novel types of dialkyldithiol mesaconates (DRTM, M1) were synthesized and copolymerized with styrene (Ma) in tetrahydro-furan at 60 °C in order to clarify the polymerization behavior of DRTM and the substituent effects on the copolymerization. From the results obtained, the monomer reactivity ratio r1, r2 and Q1, e1 values were determined. It was found that the relative reactivities l/r2 of DRTM toward an attack by polystyryl radical were correlated only by the polar substituent constant σ? of the alkyl group in DRTM, but not by the steric substituent constant E, in Taft's equation: log (l/r2) = σ?σ? + ΔEs. It was also observed that the Q1 and e1 values for DRTM were correlated by Taft's σ? constant. The number-average molecular weights of the DRTM-ST copolymer were found to be between 5.0 × 103 and 1.2 × 104. 相似文献
213.
Sina Schwendemann Shunsuke Oishi Prof. Dr. Susumu Saito Dr. Roland Fröhlich Dr. Gerald Kehr Prof. Dr. Gerhard Erker 《化学:亚洲杂志》2013,8(1):212-217
D ‐(+)‐Camphor forms the enamine 2 with piperidine. Compound 2 adds HB(C6F5)2 at the enamine carbon atom C3 to form a Lewis acid/Lewis base adduct (exo‐/endo‐isomers of 3 ). Exposure of 3 to dihydrogen (2.5 bar, room temperature) leads to heterolytic splitting of H2 to form the H+/H? addition products ( 4 , two diastereoisomers) of the “invisible” frustrated Lewis pairs ( 5 , two diastereoisomers) that were apparently generated in situ by enamine hydroboration under equilibrium conditions. 相似文献
214.
Jing Yu Oishi Sanyal Andrew P. Izbicki Ilsoon Lee 《Macromolecular rapid communications》2015,36(18):1669-1674
This work focuses on the design of porous polymeric films with nano‐ and micro‐sized pores existing in distinct zones. The porous thin films are fabricated by the post‐treatment of layer‐by‐layer assembled poly(allylamine hydrochloride) (PAH)/poly(acrylic acid) (PAA) multilayers. In order to improve the processing efficiency, the deposition time is shortened to ≈10 s. It is found that fine porous structures can be created even by significantly reducing the processing time. The effect of using polyelectrolytes with widely different molecular weights is also studied. The pore size is increased by using high molecular weight PAH, while high molecular weight PAA minimizes the pore size to nanometer scale. Having gained a precise control over the pore size, layered multiscale porous thin films are further built up with either a microsized porous zone on top of a nanosized porous zone or vice versa.
215.
Azusa Kondoh Masafumi Oishi Hikaru Tezuka Masahiro Terada 《Angewandte Chemie (International ed. in English)》2020,59(19):7472-7477
In the field of chiral Brønsted base catalysis, a new generation of chiral catalysts has been highly anticipated to overcome the intrinsic limitation of pronucleophiles that are applicable to the enantioselective reactions. Herein, we reveal conceptually new chiral Brønsted base catalysts consisting of two different organobase functionalities, one of which functions as an organosuperbase and the other as the substrate recognition site. Their prominent activity, which stems from the distinctive cooperative function by the two organobases in a single catalyst molecule, was demonstrated in the unprecedented enantioselective direct Mannich‐type reaction of α‐phenylthioacetate as a less acidic pronucleophile. The present achievement would provide a new guiding principle for the design and development of chiral Brønsted base catalysts and significantly broaden the utility of Brønsted base catalysis in asymmetric organic synthesis. 相似文献
216.
Dr. Lei Zhang Takumi Oishi Liuzhou Gao Shiyu Hu Linlin Yang Prof. Dr. Wei Li Shengjun Wu Prof. Dr. Rong Shang Prof. Dr. Yohsuke Yamamoto Prof. Dr. Shuhua Li Prof. Dr. Wei Wang Prof. Dr. Guxiang Zeng 《Chemphyschem》2020,21(23):2573-2578
A new efficient metal-based frustrated Lewis pair constructed by (PtBu3)2Pt and B(C6F5)3 was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H2 liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C6F5)3 moiety. Two equivalents of H2 were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively. 相似文献
217.
218.
219.
Francesco Boschetto Hoan Ngoc Doan Phu Phong Vo Matteo Zanocco Kenta Yamamoto Wenliang Zhu Tetsuya Adachi Kenji Kinashi Elia Marin Giuseppe Pezzotti 《Molecules (Basel, Switzerland)》2021,26(10)
The present work investigated the effect of Polylactic acid (PLA) fibers produced by centrifugal spinning with incorporated BaTiO3 particles to improve their bacteriostatic behavior. The PLA matrix and three composites, presenting three different amounts of fillers, were subjected to UV/O3 treatment monitoring the possible modifications that occurred over time. The morphological and physical properties of the surfaces were characterized by different microscopic techniques, contact angle, and surface potential measurements. Subsequently, the samples were tested in vitro with human dermal fibroblasts (HDF) to verify the cytotoxicity of the substrates. No significant differences between the PLA matrix and composites emerged; the high hydrophobicity of the fibers, derived by the polymer structure, represented an obstacle limiting the fibroblast attachment. Samples underwent bacterial exposure (Staphylococcus epidermidis) for 12 and 24 h. Increasing the concentration of BT, the number of living bacteria and their distribution decreased in comparison with the PLA matrix suggesting an effect of the inorganic filler, which generates a neutralization effect leading to reactive oxygen species (ROS) generation and subsequently to bacterial damages. These results suggest that the barium titanate (BT) fillers clearly improve the antibacterial properties of PLA fibers after aging tests made before bacterial exposure, representing a potential candidate in the creation of composites for medical applications. 相似文献
220.
Kenta Sato Dr. Masashi Hasegawa Yuki Nojima Nobuyuki Hara Dr. Tomohiko Nishiuchi Prof. Dr. Yoshitane Imai Prof. Dr. Yasuhiro Mazaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(4):1323-1329
A curved stereogenic [6]paraphenylene ([6]PP), anchoring a chiral binaphthyl scaffold at 7,7’-positions, was prepared and investigated for its properties as a solid-state circularly polarized luminescence (CPL) dye. X-ray analysis revealed a helically twisted structure of PP units induced by axial chirality of binaphthyl framework. The curved [6]PP exhibits fluorescence in powder and polymethyl methacrylate (PMMA) film as well as solution. A significant increase in quantum yield was observed for a non-fluid PMMA film owing the suppression of the molecular motion. The gCPL values of the dye in solution and as PMMA film were almost the same (4.3–4.4×10−3) and lager than that in powder. TD-DFT calculations in the excited state suggest that the exciton can be delocalized into a twisted PP unit to produce a larger magnetic transition dipole moment. 相似文献