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131.
On irradiation arylcarbothioamides (1) undergo, in the absence of oxygen, the Paterno-Büchi reaction with olefins followed by cleavage, whereas under aerobic conditions the photoreaction proceeds to give 4 and 5 probably via nitrile sulfide intermediates. 相似文献
132.
A series of novel chiral bisazetidines in which two azetidine rings are either directly connected or coupled in tandem style, are synthesized in good yields by the hydroalane reduction of the corresponding bis-beta-lactame. 相似文献
133.
Kazuaki Kuwata Rie Fujita Kengo Hanaya Shuhei Higashibayashi Takeshi Sugai 《Tetrahedron》2018,74(7):740-745
A formal total synthesis of (?)-hamigeran B was achieved in 17 steps from commercially available ethyl 2-oxocyclopentanecarboxylate. Carbonyl reductase-catalyzed asymmetric reduction and the subsequent chemical transformations furnished an enantiomerically pure synthetic intermediate, (R)-5-formyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate. Suzuki-Miyaura coupling with Gao's arylboronate [2-(2-formyl-3-methoxy-5-methylphenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane], under PdCl2(dppf)?CH2Cl2 catalysis, and the subsequent cyclization by way of intramolecular reductive SmI2-mediated 1,2-diol formation provided a tricyclic skeleton with a tetrasubstituted double bond between C-1 and C-9b. Upon hydrogenation of this double bond, the proper stereochemistry of the remaining chiral centers was established. Exclusive addition of the hydrogen atom from the β-face occurred, owing to the shielding of the α-face with a bulky TBS protective group on the C-4 alcohol. The hydrogenation products were transformed into Clive's synthetic precursor for (?)-hamigeran B. 相似文献
134.
Hyunkook Park Ickhee Lee Kyu Seong Choi Kazuaki Wagatsuma Sang Chun Lee 《Talanta》2007,72(5):1659-1666
We present a newly designed soft plasma ionization (SPI) source developed for mass spectrometric study of organic compounds in this study. The SPI cell having a relatively small size consists of a hollow anode and a hollow mesh cathode. The voltage–current characteristic depending on the pressure was investigated, indicating that it has similar characteristics to conventional hollow cathode glow discharges. To investigate the emission characteristics of the SPI source, some molecular band emission spectra (N2, N2+ and OH+) were measured by using argon and helium discharge gases. The SPI source was installed to a commercially used quadrupole mass analyzer for analyzing organic compounds. To demonstrate the SPI source, the mass spectra of some organic compounds (methylene chloride, toluene, benzene, cyclohexane and chloroform) were measured. The organic compounds were ionized with good stability in the plasma, and the fragmentation depended on the applied current. When helium and argon gases were used as the discharge gas, the helium plasma was more suitable for SPI-MS rather than argon because the argon plasma not only suffers from spectral interference but also has lower sensitivity. 相似文献
135.
Kazuaki Yoshida 《Journal of Sol-Gel Science and Technology》2007,43(1):9-13
Abrasive properties of cocoon shaped silica particles fabricated by a sol–gel method have been studied. Since silicon wafers
are polished with slurry by the mechanism of Chemical Mechanical Polishing, polishing rates may depend on various chemical
and mechanical factors, such as particle concentration in slurry, slurry pH and kinds of basic compounds for controlling the
slurry pH.
The silicon wafer was polished by slurry continuously fed on a pad, and the polishing rate was estimated as a weight loss
of the wafer. For studying the effects of the various factors on the rate, the slurries were prepared by adding the silica
particles, basic compounds or salts, and the polishing rates of the slurry were measured.
The effects of the various factors were made clear as follows: For the effect of particle concentration, the rates increased
with increasing of the concentrations up to 1.0 wt.%. And for the effect of the slurry pH, slurries added basic compounds,
such as KOH, NaOH, ammonia, were tested, and it was found that increasing of the slurry pH brought increases of the polishing
rates. KOH-containing slurry of pH 13.2 had the fastest rate, 3.6 times as fast as the standard slurry with pH 9.4. For the
effect of the adding of salts, it was indicated that the salts, such as KCl, NaCl, NH4Cl, NaNO3 and K2SO4 increased the polishing rates, and that KCl-containing slurry of 0.36 mol/l had the highest polishing rate, 3.4 times as
fast as that of the standard slurry containing no salts. 相似文献
136.
Ito K Takayama Y Ikedo M Mori M Taoda H Xu Q Hu W Sunahara H Hayashi T Sato S Hirokawa T Tanaka K 《Journal of chromatography. A》2004,1039(1-2):141-145
The determination of seven aliphatic carboxylic acids, formic, acetic, propionic, isobutyric, n-butyric, isovaleric and n-valeric acids in anaerobic digestion process waters was examined using ion-exclusion chromatography with conductimetric detection. The analysis of these biologically important carboxylic acids is necessary as a measure for evaluating and controlling the process. The ion-exclusion chromatography system employed consisted of polymethacrylate-based weakly acidic cation-exchange resin columns (TSKgel OApak-A or TSKgel Super IC-A/C). weakly acidic eluent (benzoic acid), and conductimetric detection. Particle size and cation-exchange capacity were 5 microm and 0.1 meq./ml for TSKgel OApak-A and 3 microm and 0.2 meq./ml for TSKgel Super IC-A/C, respectively. A dilute eluent (1.0-2.0 mM) of benzoic acid was effective for the high resolution and highly conductimetric detection of the carboxylic acids. The good separation of isobutyric and n-butyric acids was performed using the TSKgel Super IC-A/C column (150 mm x 6.0 mm i.d. x 2). The simple and good chromatograms were obtained by the optimized ion-exclusion chromatography conditions for real samples from mesophilic anaerobic digestors, thus the aliphatic carboxylic acids were successfully determined without any interferences. 相似文献
137.
Nakano K Sada K Nakagawa K Aburaya K Yoswathananont N Tohnai N Miyata M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(6):1725-1733
Cholic acid (CA) forms inclusion crystals that have a sandwich-type lamellar structure constructed by the alternative stacking of host bilayers and guest layers. Five disubstituted benzenes, o-toluidine, m-fluoroaniline, o-chlorotoluene, o-bromotoluene, and indene, are accommodated in the two-dimensional void space between the host bilayers at 1:2 host-guest stoichiometries. Thermal gravimetric analysis of the inclusion crystals revealed that all the guest molecules, except o-toluidine, are released in two separate steps, indicating the formation of intermediate crystals after the first guest release. Adequate heat treatment of the four inclusion crystals induces release of half or three quarters of the guest molecules. X-ray diffraction patterns of the intermediate crystals revealed that the crystals have a bilayer structure the same as those of the common CA inclusion crystals. They have one-dimensional cavities, in which the guest molecules are included at a 1:1 or 2:1 host-guest stoichiometry. These facts indicate that the host bilayers move 1.6-4.5 A perpendicular to the layer direction by desorption of the guest molecules. Furthermore, a reverse structural change is also achieved by absorption of the guest molecules to regenerate the starting sandwich-type inclusion crystals. This reversible change in the host bilayer by the guest sorption and desorption is a novel example of organic intercalation materials. 相似文献
138.
Redox-photosensitized aminations of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia 总被引:1,自引:0,他引:1
Yasuda M Kojima R Tsutsui H Utsunomiya D Ishii K Jinnouchi K Shiragami T Yamashita T 《The Journal of organic chemistry》2003,68(20):7618-7624
1,2,4-Triphenylbenzene and 2,2'-methylenedioxy-1,1'-binaphthalene successfully photosensitized the aminations of 1,2-benzo-1,3-cycloalkadienes, arylcyclopropanes, and quadricyclane with ammonia and primary amines in the presence of m- or p-dicyanobenzene, which gave the 4-amino-1,2-benzocycloalkenes, 3-amino-1-arylpropanes, and 7-amino-5-(p-cyanophenyl)bicyclo[2.2.1]hept-2-ene, respectively. A key pathway for the photosensitized amination is the hole transfer from the cation radicals of the sensitizers that were generated by photoinduced electron transfer to the electron acceptors to the substrates. Therefore, it was found that the relationships in oxidation potentials between the sensitizers and the substrates and the positive charge distribution of the cation radicals of the substrates were important factors for the efficient amination. 相似文献
139.
Chiral calixarene analogs incorporating cystine peptide into their macrocyclic ring were easily prepared by the cyclization reactions of bis(chloromethyl)phenol-formaldehyde oligomers with cystine peptides in moderate yields. Circular dichroism (CD) spectra indicated the existence of the transmission of the chirality from peptide unit to phenol-formaldehyde oligomer moiety. 相似文献
140.
New thermal rearrangement of 2H-azirines: Formation of enamines and their cyclization into pyridines
Kazuaki Isomura Shin-ichi Noguchi Masumi Saruwatari Sumiko Hatano Hiroshi Taniguchi 《Tetrahedron letters》1980,21(40):3879-3882
Intermediary formation of enamines in the course of cyclization of vinyl nitrenes into 6-membered ring compounds showed that this reaction proceeded not by insertion but by consecutive hydrogen shift and electrocyclic reaction. 相似文献