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521.
522.
Tomoyuki Kitano Dr. Tetsuya Shishido Dr. Kentaro Teramura Prof. Dr. Tsunehiro Tanaka 《Chemphyschem》2013,14(11):2560-2569
Thermally stable Brønsted acid sites were generated on alumina‐supported niobium oxide (Nb2O5/Al2O3) by calcination at high temperatures, such as 1123 K. The results of structural characterization by using Fourier‐transform infrared (FTIR) spectroscopy, TEM, scanning transmission electron microscopy (STEM), and energy‐dispersive X‐ray (EDX) analysis indicated that the Nb2O5 monolayer domains were highly dispersed over alumina at low Nb2O5 loadings, such as 5 wt %, and no Brønsted acid sites were presents. The coverage of Nb2O5 monolayer domains over Al2O3 increased with increasing Nb2O5 loading and almost‐full coverage was obtained at a loading of 16 wt %. A sharp increase in the number of hydroxy groups, which acted as Brønsted acid sites, was observed at this loading level. The relationship between the acidic properties and the structure of the material suggested that the bridging hydroxy groups (Nb? O(H)? Nb), which were formed at the boundaries between the domains of the Nb2O5 monolayer, acted as thermally stable Brønsted acid sites. 相似文献
523.
Masaaki Yoshifuji Kozo Toyota Naoki Inamoto Ken Hirotsu Taiichi Higuchi Shigeru Nagase 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):237-243
Abstract The X-ray analyses of sterically protected Z-2-t-butyldimethylsilyloxy-2-phenylphosphaethylene (Z-2) and 3,3-diphenyl-1-phosphaallene (3) were carried out and the structures of the parent compounds, HP[dbnd]CH2 and HP[dbnd]C[dbnd]CH2, were optimized by ab initio methods. 相似文献
524.
Masaaki Yoshifuji Kozo Toyota 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):589-592
Abstract: Sterically protected low-coordinated phosphorus-containing cyclobutenes were prepared and characterized as well as [4]radialenes. The reactions were studied involving E/Z isomerization, transition-metal complex formation, and coupling reactions catalyzed by some palladium complex ligated with diphosphacyclobutenes. 相似文献
525.
Concise and efficient enantioselective total syntheses of heliannuols B and D have been accomplished using chirality transfer through a Lewis acid-promoted Claisen rearrangement for the construction of the C7 tertiary stereogenic center and a relay ring-closing metathesis for assembling the dihydrobenzo[b]oxepine backbone of the natural products as the key steps. 相似文献
526.
Synthesis of 1,3‐Bis(tetracyano‐2‐azulenyl‐3‐butadienyl)azulenes by the [2+2] Cycloaddition–Retroelectrocyclization of 1,3‐Bis(azulenylethynyl)azulenes with Tetracyanoethylene
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Dr. Taku Shoji Mitsuhisa Maruyama Akifumi Maruyama Prof. Dr. Shunji Ito Dr. Tetsuo Okujima Prof. Dr. Kozo Toyota 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11903-11912
1,3‐Bis(azulenylethynyl)azulene derivatives 9–14 have been prepared by palladium‐catalyzed alkynylation of 1‐ethynylazulene 8 with 1,3‐diiodoazulene 1 or 1,3‐diethynylazulene 2 with the corresponding haloazulenes 3–7 under Sonogashira–Hagihara conditions. Bis(alkynes) 9–14 reacted with tetracyanoethylene (TCNE) in a formal [2+2] cycloaddition–retroelectrocyclization reaction to afford the corresponding new bis(tetracyanobutadiene)s (bis(TCBDs)) 15–20 in excellent yields. The redox behavior of bis(TCBD)s 15–20 was examined by using CV and differential pulse voltammetry (DPV), which revealed their reversible multistage reduction properties under the electrochemical conditions. Moreover, a significant color change of alkynes 9–14 and TCBDs 15–20 was observed by visible spectroscopy under the electrochemical reduction conditions. 相似文献
527.
Selective Aerobic Oxidation of Primary Alcohols to Aldehydes over Nb2O5 Photocatalyst with Visible Light
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Dr. Shinya Furukawa Prof. Dr. Tetsuya Shishido Dr. Kentaro Teramura Prof. Dr. Tsunehiro Tanaka 《Chemphyschem》2014,15(13):2665-2667
Primary alcohols are selectively converted into aldehydes by using a Nb2O5 photocatalyst under visible‐light irradiation. A strong interaction between the alcohol and Nb2O5 generates a donor level within the forbidden band of Nb2O5, which provides a visible‐light‐harvesting ability. Over oxidation of aldehydes into carboxylic acids does not proceed under visible‐light irradiation. 相似文献
528.
The adsorption and desorption kinetics of water molecules on Rh(111) were investigated using temperature programed desorption (TPD). Water molecules on Rh(111) show coverage-dependent sticking probability; the initial sticking probability is estimated to be 0.46. In the desorption process, a dilute gaslike phase and two-dimensional islands of water coexist on the surface. Based on the model proposed by Kreuzer and Payne [Surf. Sci.200, L433 (1988)], the apparent fractional-order TPD spectra can be interpreted as first-order desorption from the coexistence of two phases on which the sticking probabilities are different. Based on this, the previous estimation of pre-exponential factors assuming half-order desorption [A. Beniya et al., J. Chem. Phys.125, 054717 (2006)] should be revised. 相似文献
529.
Geometrical isomerization of fac-Mo(CO)3L3 (L = P(OPh)3, P(OMe)3, P(OEt)3) to the mer form and that of cis-Mo(CO)4L2 (L = P(OPh)3, P(OMe)3, PPh2(OMe)) to the trans form were observed in CH2Cl2 at room temperature in the presence of a catalytic amount of Me3SiOSO2CF3 (TMSOTf). Crossover experiments suggest that a ligand dissociation is not involved in the isomerization. A catalytic cycle involving an interaction of the silicon atom in Me3Si+ with one oxygen in P(OR)3 ligands has been proposed. The first isolation and the X-ray structure analysis were attained for mer-Mo(CO)3{P(OPh)3}3 through the TSMOTf-assisted isomerization of fac-Mo(CO)3{P(OPh)3}3. 相似文献
530.
Koitaya T Shimizu S Mukai K Yoshimoto S Yoshinobu J 《The Journal of chemical physics》2012,136(21):214705
Novel isotope effects were observed in desorption kinetics and adsorption geometry of cyclohexane on Rh(111) by the use of infrared reflection absorption spectroscopy, temperature programmed desorption, photoelectron spectroscopy, and spot-profile-analysis low energy electron diffraction. The desorption energy of deuterated cyclohexane (C(6)D(12)) is lower than that of C(6)H(12). In addition, the work function change by adsorbed C(6)D(12) is smaller than that by adsorbed C(6)H(12). These results indicate that C(6)D(12) has a shallower adsorption potential than C(6)H(12) (vertical geometric isotope effect). The lateral geometric isotope effect was also observed in the two-dimensional cyclohexane superstructures as a result of the different repulsive interaction between interfacial dipoles. The observed isotope effects should be ascribed to the quantum nature of hydrogen involved in the C-H···metal interaction. 相似文献