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181.
Takanori Shibata Ai Kawachi Mika Ogawa Yusuke Kuwata Kyoji Tsuchikama Kohei Endo 《Tetrahedron》2007,63(52):12853-12859
A chiral rhodium complex catalyzed an enantioselective [2+2+2] cycloaddition of unsymmetrical diynes with norbornene, and tetracyclic products were obtained in good to excellent ee. The cycloaddition of a symmetrical diyne with styrene derivatives as coupling partners gave bicyclic products in good ee. 相似文献
182.
183.
Higuchi H Ohta E Kawai H Fujiwara K Tsuji T Suzuki T 《The Journal of organic chemistry》2003,68(17):6605-6610
2,2'-[2,2-Bis(4-dimethylaminophenyl)ethenyl]biphenyl (1) is a strong electron donor that undergoes oxidative C-C bond formation to give a stable dication rac-2(2+), the 9,10-dihydrophenanthrene derivative substituted with two bis(4-dimethylaminophenyl)methylium chromophores. This dication salt regenerates the starting diolefin 1 by reductive C-C bond breaking, thus realizing a new electrochromic system with high electrochemical bistability and a vivid change in color from yellow to deep blue. Similarly, the binaphthylic diolefin rac-3 and the helicene-type dication rac-4(2+) are interconvertible upon two-electron transfer. Both the UV-vis and CD spectra changed drastically upon electrochemical transformation between optically pure 3 and 4(2+), which represents a new electrochiroptical system. 相似文献
184.
Atsushi Takemura Akio Murai Hidetoshi Kawai Takanori Suzuki 《Tetrahedron letters》2004,45(41):7567-7571
A synthetic method for a branched ether system was developed. The method was based on Lewis-acid-promoted γ-position selective reduction of a γ-alkoxy β,γ-unsaturated α-silyloxy nitrile, prepared through a process including intermolecular hetero-Michael reaction of a 2-butynoate ester derivative with an alcohol. The method was efficiently applied to the synthesis of fused medium-ring ethers involving the EF-ring segment (2) of ciguatoxin (1). 相似文献
185.
The α-alkyl β-oxoesters undergo type II photoreactions. The process of back hydrogen transfer in the 1,4-biradical intermediate to revert to the starting ester is suppressed because of the intramolecular hydrogen bonding between the hydroxyl and carboalkoxyl groups in the biradical intermediate. The hydrogen bonding determines the stereochemistry of 1,4-biradical cyclization. The cyclobutanols having the hydroxyl group cis to the carboalkoxyl group are formed exclusively from the α-alkyl β-oxoesters . The enol form of the type II elimination product, the benzoylacetate , acts as an effective internal filter for the photoreaction of the α-alkyl β-oxoester . 相似文献
186.
Takanori Mizushima Kazumi Matsumoto Hironobu Ohkita Noriyoshi Kakuta 《Plasma Chemistry and Plasma Processing》2007,27(1):1-11
Plasma synthesis of ammonia was studied at atmospheric pressure using a dielectric-barrier-discharge-plasma reactor equipped
with a metal-loaded membrane-like alumina tube as a catalyst between the electrodes. Introducing the pure alumina into N2–H2 plasma resulted in an increase in the ammonia yield and the further improvement was achieved by loading the alumina with
Ru, Pt, Ni, and Fe. These results clearly demonstrate the catalytic effects of the alumina and the metals in the plasma reaction.
Temperature-programmed desorption and isotope exchange reaction of nitrogen revealed that plasma-excited N2 molecules were subjected to dissociative adsorptions mainly on the alumina to form atomic N(a) (The suffix “(a)” denotes
adsorbed species) species, which were converted into ammonia by H2 plasma. A role of the metals is considered to be acceleration of ammonia formation by the reaction of the alumina-adsorbed
N(a) atoms with plasma-activated hydrogen species. 相似文献
187.
Arylzinc compounds, ArZnX, were conveniently prepared in high yields by the reaction of zinc powder with aryl iodides, which contain electron-withdrawing groups such as CO(2)CH(3), CN, Br, or CF(3) at the ortho-, meta- or para-position, or electron-donating groups such as CH(3), OCH(3), or H, at 70 degrees C in THF, at 100 degrees C, or at 130 degrees C in diglyme, respectively. Pd(dba)(2) exhibited an outstanding efficient catalytic effect for the cross-coupling of these ethereal solutions of ArZnX with allylic halides to afford a variety of functionalized allylbenzenes in high yields; the reactions were mostly carried out at 0 degrees C for 5-30 min in the presence of 5 mol % of catalyst. The conversion of the aryl iodides to allylbenzenes via two reactions could be accomplished in one pot. 相似文献
188.
Takanori HayashiHiroyoshi Kanai Shinya YodoyaMasahito Oka Toshio Hayashi 《European Polymer Journal》2002,38(1):139-146
Two component random co-polypeptide hydrogels consisting of N-hydroxypropyl l-glutamine and l-alanine (Ala) or l-phenylalanine (Phe) were prepared by performing aminolysis reactions with 3-amino-1-propanol together with crosslinking reaction with 1,8-octamethylenediamine on hydrogels of the starting co-polymers consisted of γ-benzyl l-glutamate and Ala or Phe. The relationship between their bulk structure and properties was evaluated with regard to the swelling ratio in water (q), the rate of water vapor permeability (Vf), tensile properties, and enzymatic degradation behaviors of hydrogels in a pseudo-extracellular fluid (PECF). The tensile property of the hydrogels was highly dependent on q in PECF, and on the hydrophobicity of the side chains. A relationship was obtained between the Vf and q of hydrogels in PECF regardless of the differences in the nature of the side chains. Biodegradation of the hydrogels in vitro by bromelain indicated that degradation took place in bulk rather than on the surface, and that the rate of degradation was also highly dependent on q in the samples as well as on the hydrophobicity of the side chains of the samples. 相似文献
189.
190.
Bis(carbazolylphenyl) and bis(diphenylaminophenyl) derivatives of 1,6-methano[10]annulene, which is luminescent material and contains seven-membered rings, are synthesized. The bis(phenylcarbazole) derivative 3 have high melting point and glass transition temperature. Electroluminescence characteristics of organic light-emitting diodes using these methano[10]annulenes were investigated. 相似文献