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61.
Pd(OAc)2 combined with phosphines catalyzes homolytic cleavage of the C—Cl bond of CCl4 and CCl3CO2CH3 leading to facile addition to olefins under mild conditions. BrCCl3 also reacts with olefins to give 1,1,1-trichloro-3-bromoalkanes. The reaction is accelerated under CO atmosphere, and the presence of bases such as NaOAc or K2CO3 is essential to attain high yields of the adducts. 相似文献
62.
Both the enantiomers of sclerosporin and sclerosporal were synthesized from (-)-carvone. (4R,9R,10S)-(+)-Sclerosporin and (4R,9R,10S)-(-)-sclerosporal were identified as the natural enantiomers by a comparison of their CD-spectra. An intramolecular Diels-Alder route was proved to be an efficient method of preparing sufficient amounts of (+)- for the biological study. 相似文献
63.
在全球各大电信运营商同时面临增量不增收,ARPU逐年下降的问题时,日本传统电信运营商NTT集团公布了未来发展目标和经营战略。通过全面解读和深刻分析NTT集团公司未来的发展目标和经营战略,寻找提高企业竞争力的新手段。 相似文献
64.
Hiroomi Homma Kiichiro Kurihara Hajime Nakazawa 《Journal of the mechanics and physics of solids》1984,32(3):213-226
A computational model was developed to numerically analyse fatigue striations. The inclined strip yield model with continuous distributions of infinitesimal dislocations was utilized to express the crack tip plasticity in this model. The fatigue crack tip blunting process was approximated by sequential activation of two slip lines under loading, and crack closure during unloading was taken into account. The plastic zone at a growing fatigue crack tip at the maximum load was independent of the crack growth up to ten cycles while the reversed plastic zone decreased in a size to one twentieth of that at the maximum load as the crack grew. The ratio of these plastic zone sizes and also the crack tip opening displacement were quite different from the simple prediction by J.R. Rice for a stationary crack. The computed striation spacings were compared with the observed ones and moderate agreement between them obtained. 相似文献
65.
对日本STS(科学技术与社会)理论界的概况做一个背景式的描述,结合不同历史时期公众与科学事务关系的发展变化,梳理了公众理解科学运动在日本的实践活动及其发展过程。 相似文献
66.
2001年,同整个产业相比,日本的移动通信发展是比较好的,特别是在移动互联网方面遥遥领先,NTTDoCoMo已经跻身全球电信运营商第6的位置。目前,日本的几大移动运营商正在积极发展3G,形势不错,但也存在一些问题,如运营商在移动语音和移动数据方面根深蒂固的传统观念、推出能被人们接受的价格方案、发展良好的现有移动数据业务对3G的影响、令人尴尬的手机故障等。 相似文献
67.
The distribution in the silicon epitaxial growth from SiCl4 and hydrogen are observed in situ by IR absorption spectroscopy. Two methods are used complementarily, one is IR spectroscopy of reactants extracted from the reactor by a fine quartz tube which is not disturbing the reactions, and gives knowledge about the local distribution, the other is direct IR spectroscopy of hot reactants in the reactor which is useful to ascertain the results at the real high temperature situation. The intermediate species are SiHCl3, SiH2Cl2 which is estimated from the induced emission bands at 500 and 570 cm-1. HCl is a dominant waste product and contributes to reverse reactions. To investigate the reaction, HCl is intentionally injected into the reacting gas. This kind of injection method may also be very effective to analyze the reactions using other reactants such as SiCl4, SiHCl3 and SiH2Cl2. 相似文献
68.
Shinzi Kato Toshimitsu Kato Takashi Yamauchi Yutaka Shibahashi Etsuo Kakuda Masateru Mizuta Yoshio Ishii 《Journal of organometallic chemistry》1974,76(2):215-224
Some crystalline di- and tri-phenylstannyl esters [ArCS2SnPh3 and (ArCS2)2SnPh2] of aromatic dithio acids have been prepared in good yields and characterized. Preferential cleavage of the SnS bond of the ester was observed by treating them with primary and secondary amines as well as with phenacylidenetetramethylenesulfurane. 相似文献
69.
Structure of citreoviridin, a “yellowed rice toxin” produced by P. citreo-viride molded on rice, was determined as 1b. 相似文献
70.
The chemo-enzymatic synthesis of (R)-5-hydroxymethyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate, a potential chiral building block for polycyclic terpenoids containing a five–membered ring having isopropyl and angular methyl substituents, such as erinacin A and dolatriol, was achieved over 11 steps from ethyl 2-oxocyclopentane-1-carboxylate. The key synthetic precursor for this triflate was ethyl (1S,2R)-2-hydroxycyclopentanecarboxylate (>99% ee), which was prepared by a lipase-catalyzed enantioselective hydrolysis of the corresponding racemic acetate. The antipodal (S)-triflate is expected to be the synthetic intermediate for another group of terpenoids involving hamigeran B and stolonidiol. Enantiomerically pure (1R,2S)-hydroxyester (>99% ee) was prepared in high yield using the asymmetric reduction of the oxoester with commercially available carbonyl reductase, “Chiralscreen® OH”-E001. 相似文献