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151.
Min Zhang Takaaki Sonoda Masaaki Mishima Tsunetoshi Honda Ivo Leito Ilmar A. Koppel Werner Bonrath Thomas Netscher 《Journal of Physical Organic Chemistry》2014,27(8):676-679
The gas‐phase acidity (GA) values were determined for a number of perfluoroalkyl‐substituted sulfonylimides by measuring proton‐transfer equilibria using a Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometer. The GA scale below 286.5 kcal mol?1 for (CF3SO2)2NH was extended and partially revised. The GA value of (C4F9SO2)2NH which is currently the strongest acid was revised from 284.1 to 278.6 kcal mol?1. The effect of fluorine atoms on the acidity of perfluoroalkyl‐substituted sulfonylimides was described with the following model where N(α), N(β), N(γ), and N(δ) are the numbers of fluorine atoms at α, β, γ, and δ position in RfSO2 (Rf = perfluoroalkyl group), respectively. This correlation indicates that the electron‐withdrawing ability of the RfSO2 group can be described in terms of the number of fluorine atoms in the perfluoroalkyl group corrected by taking into account their positions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
152.
Yoshihiro Shigemasa Takaaki Ueda Hitoshi Sashiwa Hiroyuki Saimoto 《Journal of carbohydrate chemistry》2013,32(4):607-618
ABSTRACT The carbon number of the main product and the total yield of products increased with an increase in the amount of triethylamine (TEA). Furthermore, the decrease of DL-2-C-hydroxymethyl-3-pentulose (2-H-3-P) was speeded up by increasing the TEA concentration and 2,4-bis(hydroxy-methyl)-3-pentulose (2,4-BH-3-P) increased smoothly along with the progress of the reaction. In the low formaldehyde (HCHO) concentration range (ca. 0.5 M), dihydroxyacetone (DHA) and DL-glycero-tetrulose were main products. 2-H-3-P and 2,4-BH-3-P increased with an increase in the formaldehyde concentration. Dihydroxyacetone, DL-glycero-tetrulose, 2-H-3-P and 2,4-BH-3-P were favorably obtained from a formose reaction by choosing a suitable [thiamine. HCl]/[HCHO] ratio. Under the reaction conditions reported in this paper, thiamine decomposed rapidly and lost its catalytic ability. 相似文献
153.
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
154.
Yuta Yanagita Hugh Nakamura Kenji Shirokane Yusuke Kurosaki Dr. Takaaki Sato Prof. Dr. Noritaka Chida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):678-684
While the synthesis of amide bonds is now one of the most reliable organic reactions, functionalization of amide carbonyl groups has been a long‐standing issue due to their high stability. As an ongoing program aimed at practical transformation of amides, we developed a direct nucleophilic addition to N‐alkoxyamides to access multisubstituted amines. The reaction enabled installation of two different functional groups to amide carbonyl groups in one pot. The N‐alkoxy group played important roles in this reaction. First, it removed the requirement for an extra preactivation step prior to nucleophilic addition to activate inert amide carbonyl groups. Second, the N‐alkoxy group formed a five‐membered chelated complex after the first nucleophilic addition, resulting in suppression of an extra addition of the first nucleophile. While diisobutylaluminum hydride (DIBAL‐H) and organolithium reagents were suitable as the first nucleophile, allylation, cyanation, and vinylation were possible in the second addition including inter‐ and intramolecular reactions. The yields were generally high, even in the synthesis of sterically hindered α‐trisubstituted amines. The reaction exhibited wide substrate scope, including acyclic amides, five‐ and six‐membered lactams, and macrolactams. 相似文献
155.
Tetraphenylporphyrins carrying primary or tertiary alcohols in a phenyl group were bonded to silicate glass by heat treatment. The rate of base catalyzed hydrolysis of tertiary ester was 20 times slower than that of primary ester, while the rate of acid catalyzed hydrolysis of tertiary ester was only 2.5 times slower than that of primary ester. Hydrolysis of tertiary alcohol bonded silica in HCl/H218O displayed that there is a covalent bond between alcohol oxygen and silicon, and the C–O bond is cleaved under acidic conditions, while the Si–O bond is cleaved under basic conditions. 相似文献
156.
Kazuto Hatakeyama Mohammad Razaul Karim Chikako Ogata Hikaru Tateishi Asami Funatsu Takaaki Taniguchi Michio Koinuma Shinya Hayami Yasumichi Matsumoto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(27):7117-7120
Proton conductivities of layered solid electrolytes can be improved by minimizing strain along the conduction path. It is shown that the conductivities (σ) of multilayer graphene oxide (GO) films (assembled by the drop‐cast method) are larger than those of single‐layer GO (prepared by either the drop‐cast or the Langmuir‐Blodgett (LB) method). At 60 % relative humidity (RH), the σ value increases from 1×10−6 S cm−1 in single‐layer GO to 1×10−4 and 4×10−4 S cm−1 for 60 and 200 nm thick multilayer films, respectively. A sudden decrease in conductivity was observed for with ethylenediamine (EDA) modified GO (enGO), which is due to the blocking of epoxy groups. This experiment confirmed that the epoxide groups are the major contributor to the efficient proton transport. Because of a gradual improvement of the conduction path and an increase in the water content, σ values increase with the thickness of the multilayer films. The reported methods might be applicable to the optimization of the proton conductivity in other layered solid electrolytes. 相似文献
157.
Atsushi Unemoto Yoshiki IwaiSatoshi Mitani Seung-Wook BaekSeitaro Ito Takaaki TomaiJunichi Kawamura Itaru Honma 《Solid State Ionics》2011,201(1):11-20
Lithium ion conducting solid-state composites consisting of lithium ion conducting ionic liquid, lithium bis(trifluoromethanesulfonyl)amide (Li-TFSA) dissolved 1-ethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl)amide (EMI-TFSA), denoted by [yMLi+][EMI+][TFSA−] in this study, and various oxide particles such as SiO2, Al2O3, TiO2 (anatase and rutile) and 3YSZ are synthesized via a liquid route for the molar concentration of lithium, y, to be 1. The composite consists of SiO2 and the ionic liquid with y = 0.2 was also prepared. The ionic liquid are quasi-solidified at the above oxide particle surfaces when x is below 40 for y = 1 and x is below 30 for y = 0.2, corresponding to the confinable thickness of the ionic liquid at the oxides' surfaces to be approximately 5-10 nm regardless of the oxide compositions. The electrical conductivities of x vol.%[yMLi+][EMI+][TFSA-]-SiO2, Al2O3, TiO2s or 3YSZ composites are evaluated by ac impedance measurements. The quasi-solid-state composites exhibited liquid-like high apparent conductivity, e.g. 10− 3.3-10− 2.0 S cm− 1 in the temperature range of 323-538 K for SiO2-ionic liquid composites with y = 1. The self-diffusion coefficients of the constituent species of x vol.% [yMLi+][EMI+][TFSA−] (x is below 40, y = 0.2 and 1) − SiO2 are evaluated by the Pulse Gradient Spin Echo (PGSE)-NMR technique in the temperature range of 298-348 K. By the quasi-solidification of the ionic liquid at SiO2 particle surfaces, the absolute values of the diffusion coefficients of all constituent species decreased. The SiO2 surfaces work to promote ionization of ion pair, [EMI+][TFSA−], while significant influence on the solvation coordination, [Li(TFSA)n + 1]n−, was not observed. The apparent transport numbers of Li-containing species both in the bulk and the quasi-solidified ionic liquid showed similar values with each other, which was evaluated to be in the range of 0.010-0.017 for y = 0.2 and 0.051-0.093 for y = 1 in the abovementioned temperature range. 相似文献
158.
Shimokawa J Harada T Yokoshima S Fukuyama T 《Journal of the American Chemical Society》2011,133(44):17634-17637
The first total synthesis of gelsemoxonine (1) has been accomplished. Divinylcyclopropane-cycloheptadiene rearrangement of the highly functionalized substrate was successfully applied to assemble the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via the TMSCN-DBU reagent combination allowed a facile diastereoselective introduction of the latent nitrogen functionality of the unique azetidine moiety. 相似文献
159.
Takaaki Matsubara Dr. Keisuke Takahashi Dr. Jun Ishihara Prof. Dr. Susumi Hatakeyama 《Angewandte Chemie (International ed. in English)》2014,53(3):757-760
The first asymmetric total synthesis of (?)‐ophiodilactone A and (?)‐ophiodilactone B, isolated from the ophiuroid (Ophiocoma scolopendrina), is reported. The key features of the synthesis include the highly stereocontrolled construction of the structurally congested γ‐lactone/δ‐lactone skeleton through an asymmetric epoxidation, diastereoselective iodolactonization, and intramolecular epoxide‐opening with a carboxylic acid, and biomimetic radical cyclization of ophiodilactone A to ophiodilactone B. 相似文献
160.
Two‐step Synthesis of Multi‐Substituted Amines by Using an N‐Methoxy Group as a Reactivity Control Element
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Makoto Yoritate Tatsuhiko Meguro Naoya Matsuo Kenji Shirokane Dr. Takaaki Sato Prof. Noritaka Chida 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8210-8216
The development of a two‐step synthesis of multi‐substituted N‐methoxyamines from N‐methoxyamides is reported. Utilization of the N‐methoxy group as a reactivity control element was the key to success in this two‐step synthesis. The first reaction involves a N‐methoxyamide/aldehyde coupling reaction. Whereas ordinary amides cannot condense with aldehydes intermolecularly due to the poor nucleophilicity of the amide nitrogen, the N‐methoxy group enhances the nucleophilicity of the nitrogen, enabling the direct coupling reaction. The second reaction in the two‐step process was nucleophilic addition to the N‐methoxyamides. Incorporation of the N‐methoxy group into the amides increased the electrophilicity of the amide carbonyls and promoted the chelation effect. This nucleophilic addition enabled quick diversification of the products derived from the first step. The developed strategy was applicable to a variety of substrates, resulting in the elaboration of multi‐substituted piperidines and acyclic amines, as well as a substructure of a complex natural alkaloid. 相似文献