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61.
Tohru Takabatake Yumiko Hasegawa Minoru Hasegawa 《Journal of heterocyclic chemistry》1993,30(6):1477-1479
The cyclocondensations of benzofuroxan 1a with carbonyl compounds were smoothly and efficiently carried out by the adsorption of the components on the surface of silica gel or a molecular sieve to form a 2,3-disubstituted quinoxaline 1,4-dioxide. When the reactions using a molecular sieve 3A (powder) were carried out at 90°, the actual reaction times were reduced to 0.5-2 hours. Although Duerckheimer has reported the isolation of only the 7-substituted quinoxaline 1,4-dioxide when 5-methoxybenzofuroxan 1e was allowed to react with ethyl acetoacetate 2j , it produced only the 6-methoxy isomer as the reaction product by our method. 5-Carboxybenzofuroxan 1f did not react with the carbonyl compound. 相似文献
62.
Unique rearrangements of allyl 2,2-dichlorovinyl and 1,2,2-trichlorovinyl sulfides have been found. On heating the former gave 1,2-dichloro-l,4-pentadienes and the latter 2,3-dichloro-5-chloromethyl-4,5-dihydrothiophenes and 3,5,6-trichloro-3,4-dihydro-2H-thiopyranes . 相似文献
63.
Satoshi Yoshikawa Minoru Ueno Kenjiro Meguro 《Journal of polymer science. Part A, Polymer chemistry》1979,17(8):2491-2497
The monolayer properties of poly(n-stearyl methacrylate), poly(n-lauryl methacrylate), and their mixtures at various ratios of the two polymers have been studied from the measurements of their surface pressure–area isotherms at air–water interface. The monolayer properties of their mixtures have been compared with those of their corresponding copolymers. The results show that the isotherms of the mixed monolayers have two break points at higher pressures than that of poly(n-lauryl methacrylate). This suggests that the mixtures may form more stable films that consist of separate phases of the two homopolymers, although each phase may contain a small amount of the other. The isotherms of the copolymer monolayers indicate a phase transition from liquid condensed to solid film between 50 segment mole % and 70% poly(n-stearyl methacrylate). The monclayer of these copolymers has properties that differ from those of the corresponding mixtures of two pure homopolymers and is more compatible than the mixtures of pure homopolymers. 相似文献
64.
The bis(dibutylstannylene) derivative of 1,2-cyclohexylidene-myo-inositol reacted with (S)-O-acetylmandeloyl chloride and diphosphate tetraesters to give 3,6-dimandelate and 3-phosphate, respectively. Using the stannylene methodology for the optical resolution and regioselective phosphorylation of the ketal, a concise synthesis of phosphatidylinositol with the natural configuration was accomplished. 相似文献
65.
Spyridon Divanis Tugce Kutlusoy Ida Marie Ingmer Boye Isabela Costinela Man Jan Rossmeisl 《Chemical science》2020,11(11):2943
Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. Despite the substantial efforts, the driving force required for water oxidation is largely making the reaction inefficient. In the present work, we collected published studies involving DFT calculations for the OER, with the purpose to understand why the progress made so far, for lowering the overpotential of the reaction, is relatively small. The data revealed that the universal scaling relationship between HO* and HOO* intermediates is still present and robust, despite the variety in methods and structures used for calculating the binding energies of the intermediates. On the other hand, the data did not show a clear trend line regarding the O* binding. Our analysis suggested that trends in doped semiconducting oxides behave very differently from those in other oxides. This points towards a computational challenge in describing doped oxides in a realistic manner. We propose a way to overcome these computational challenges, which can be applied to simulations corresponding to doped semiconductors in general.Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. 相似文献
66.
67.
Norio Manabe Kenichi Kawamura Masanao Ishikawa Shoutarou Suzuki Boping Liu Minoru Terano Hisayuki Nakatani 《Polymer Testing》2005,24(8):994-997
In this study, a novel potentiometric titration of hydroperoxide in degraded polypropylene (PP) is proposed. This titration is quite sensitive compared with the conventional ones such as UV and manual titrations, and its detection limit was about 2 meq/kg. The sensitivity was equal to that of molecular weight measurement by GPC for the degraded PP and, in addition, the volatilization behavior of the hydroperoxide could be detected. This titration was found to be very effective for the determination of PP degradation. 相似文献
68.
A stereoselective synthesis of the LM-ring fragment has been achieved starting from a sugar derivative. A stereoselective synthesis of the JKLM-ring fragment has been achieved through a coupling between two segments via heteroconjugate addition, seven-membered ether ring formation mediated by an acetylene cobalt complex, and spiroketalization reaction. 相似文献
69.
Volker Seibert Corinna Prohl Ida Schoultz Edward Rhee Rebecca Lopez Kareem Abderazzaq Chunshui Zhou Dieter A Wolf 《BMC biochemistry》2002,3(1):22-15
Background
SCF ubiquitin ligases share the core subunits cullin 1, SKP1, and HRT1/RBX1/ROC1, which associate with different F-box proteins. F-box proteins bind substrates following their phosphorylation upon stimulation of various signaling pathways. Ubiquitin-mediated destruction of the fission yeast cyclin-dependent kinase inhibitor Rum1p depends on two heterooligomerizing F-box proteins, Pop1p and Pop2p. Both proteins interact with the cullin Pcu1p when overexpressed, but it is unknown whether this reflects their co-assembly into bona fide SCF complexes. 相似文献70.
Minoru Yamaji Ai Suzuki Fuyuki Ito Shozo Tero-Kubota Seiji Tobita Bronislaw Marciniak 《Journal of photochemistry and photobiology. A, Chemistry》2005,170(3):253-259
Photodissociation of the carbon-X (X = Br and Cl) bonds in p-bromo- and p-chloromethylbenzophenone (BMBP and CMBP) in solution were investigated by time-resolved EPR and laser flash photolysis techniques. BMBP and CMBP were found to undergo ω-bond cleavage to yield the p-benzoylbenzyl radical (BBR) at 295 K, and the quantum yields (ΦBBR) were determined. The CIDEP signal originated from BBR formed upon decomposition of CMBP was obtained while that for BMBP was absent. By using triplet sensitization of acetone, the efficiencies (BBR) of the CX bond fission in the triplet states of BMBP and CMBP were determined. The agreement between the ΦBBR and BBR values for CMBP indicates that the CCl bond dissociation occurs only in the triplet state. In contrast to CMBP, the cleavage of the CBr bond in BMBP upon direct excitation was concluded to be the event only in the excited singlet state without triplet formation, whereas the triplet state was also reactive for ω-bond dissociation. The rate of CBr bond dissociation seemed to be greater than that of intersystem crossing from the S1 to the T1 state. Schematic energy diagrams of the excited states of BMBP and CMBP were shown, and the reaction profiles were discussed from the viewpoint of the CX bond enthalpies. 相似文献