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1.
Dr. Manussada Ratanasak Takumi Murata Taishin Adachi Prof. Jun-ya Hasegawa Prof. Tadashi Ema 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(58):e202202210
BPh3 catalyzes the N-methylation of secondary amines and the C-methylenation (methylene-bridge formation between aromatic rings) of N,N-dimethylanilines or 1-methylindoles in the presence of CO2 and PhSiH3; these reactions proceed at 30–40 °C under solvent-free conditions. In contrast, B(C6F5)3 shows little or no activity. 11B NMR spectra suggested the generation of [HBPh3]−. The detailed mechanism of the BPh3-catalyzed N-methylation of N-methylaniline ( 1 ) with CO2 and PhSiH3 was studied by using DFT calculations. BPh3 promotes the conversion of two substrates (N-methylaniline and CO2) into a zwitterionic carbamate to give three-component species [Ph(Me)(H)N+CO2−⋅⋅⋅BPh3]. The carbamate and BPh3 act as the nucleophile and Lewis acid, respectively, for the activation of PhSiH3 to generate [HBPh3]−, which is used to produce key CO2-derived species, such as silyl formate and bis(silyl)acetal, essential for the N-methylation of 1 . DFT calculations also suggested other mechanisms involving water for the generation of [HBPh3]− species. 相似文献
2.
Takumi Watanabe Yuichiro Nishizawa Haruka Minato Dr. Chihong Song Prof. Dr. Kazuyoshi Murata Prof. Dr. Daisuke Suzuki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(23):8934-8938
The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications. 相似文献
3.
Hiroshi Noguchi Masanori Ueda Yoshinobu Baba Masako Takasu 《Journal of Polymer Science.Polymer Physics》2003,41(12):1316-1322
The electrophoresis of DNA chains in uncrosslinked polymer solutions with a Brownian dynamics simulation with an anisotropic friction tensor was analyzed. According to the degree of anisotropy, three types of migration behavior are obtained: fluctuation without or with periodicity between U‐shaped and compact conformations, or migration with linear conformation. We found good agreement between our simulation results and the direct observations of DNA by fluorescence microscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1316–1322, 2003 相似文献
4.
Asymmetric Horner-Wadsworth-Emmons reactions of selected meso-α-dicarbonyl compounds with chiral phosphonate reagents, which possessed axially dissymmetric 1,1′-bi-2- or 8-naphthol at the carboxylate moiety as a chiral auxiliary, were examined. The reactions proceeded smoothly with good chemical yields as well as with high diastereoselectivities. Z-olefins were preferentially formed, and it was found that the free hydroxy group at the 2′- or 8′-position on the naphthalene ring plays a crucial role in the high diastereoselectivity, probably due to a complex-induced proximity effect. Mechanistic considerations are also described. 相似文献
5.
A new method for rotation and brightness invariant pattern recognition was proposed by applying multiple circular harmonic expansions to the joint transform correlator. The amplitudes of the multiple orders of circular harmonic expansions made from a detecting image were synthetically modified to respond to the same auto-correlation peaks. These modified circular harmonic expansions were arranged in the input plane as reference patterns together with an arbitrary target pattern, and the correlation signals between them were calculated in the subtracted joint transform correlator. The fraction of the correlation-peak intensities between the target and the references were extracted as a new discrimination parameter. This new parameter performs pattern recognition under rotation and brightness invariance with good discriminability. Its high discriminability has been proved in computer simulations using the face image patterns of many individuals. 相似文献
6.
Masayuki Kuzuya Akihiro Noguchi Hideki Ito Shin-Ichi Kondo Nahoko Noda 《Journal of polymer science. Part A, Polymer chemistry》1991,29(1):1-7
Plasma-induced polystyrene radicals were first studied by electron spin resonance (ESR). The room temperature ESR spectrum was compared with those obtained by γ-irradiation, UV-irradiation, and mechanical fracture. It was found that even less than a few seconds of plasma-irradiation gave rise to a large amount of polystyrene radicals and the ESR spectrum consisted of two types of spectra, a triplet and a single broad line. The spectral feature of the triplet was nearly identical with that of γ-irradiated polystyrene. Thus, it was assigned to the structure of a cyclohexadienyl-type radical formed by a nearly random addition of a hydrogen atom to the aromatic ring. The single broad line, thought to be an outline of multicomponent spectrum, was assigned to an immobilized dangling-bond sites at the plasma-induced crosslinked portion of the polystyrene surface. 相似文献
7.
The Heat Kernel on Hyperbolic Space 总被引:1,自引:0,他引:1
The purpose of this note is to provide a new proof for the explicitformulas of the heat kernel on hyperbolic space. By definition,the hyperbolic space Hn is a (unique) simply connected completen-dimensional Riemannian manifold with a constant negative sectionalcurvature 1. 1991 Mathematics Subject Classification58G32, 58G11. 相似文献
8.
Brick DH Widgoff M Beilliere P Lutz P Narjoux JL Gelfand N Alyea ED Bloomer M Bober J Busza W Cole B Frank TA Fuess TA Grodzins L Hafen ES Haridas P Huang D Huang HZ Hulsizer R Kistiakowsky V Ledoux RJ Milstene C Noguchi S Oh SH Pless IA Steadman S Stoughton TB Suchorebrow V Tether S Trepagnier PC Wadsworth BF Wu Y Yamamoto RK Cohn HO Calligarich E Castoldi C Dolfini R Introzzi G Ratti S Badiak M DiMarco R Jacques PF Kalelkar M Plano RJ Stamer PE Brucker EB Koller EL Alexander G Grunhaus J 《Physical review D: Particles and fields》1990,41(3):765-773
9.
Adachi I Aihara H Dijkstra HB Enomoto R Fujii H Fujii K Fujii T Fujimoto J Fujiwara N Hayashii H Higashi S Iida N Imanishi A Ikeda H Ishii T Itoh R Iwasaki H Iwata S Kajikawa R Kamae T Kato S Kawabata S Kichimi H Kishida T Kobayashi M Kuroda S Kusuki N Maruyama A Maruyama K Masuda H Matsuda T Miyamoto A Morimoto T Nakamura K Nitoh O Noguchi S Ochiai F Okuno H Okusawa T Ohshima T Ozaki H Sato T Sai F Shimonaka J Shimozawa K Shirahashi A Sugahara R Sugiyama A Suzuki S Suwada T Takahashi K 《Physical review letters》1988,60(2):97-100
10.
Sakuratani Y Yamada J Kasai K Noguchi Y Nishihara T 《SAR and QSAR in environmental research》2005,16(5):403-431
External validation of the biodegradability prediction model CATABOL was conducted using test data of 338 existing chemicals and 1123 new chemicals under the Japanese Chemical Substances Control Law. CATABOL predicts that 1089 chemicals will have a BOD < 60% while 925 (85%) actually have an observed BOD<60%. The percentage of chemicals with an observed BOD value <60% tends to increase as the predicted BOD values decrease. In contrast, 340 chemicals were predicted to have a BOD > or = 60% and 234 (69%) actually had an observed BOD > or = 60%. The prediction of poor biodegradability was more accurate than the predictions of high biodegradability. The features of chemical structures affecting CATABOL predictability were also investigated. 相似文献