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91.
92.
E. N. Adamenko L. L. Frolova M. V. Panteleeva A. V. Kuchin 《Chemistry of Natural Compounds》2007,43(1):59-62
Optically active camphordihydro-2,3-pyrazine and camphorquinoxaline were prepared from camphoroquinone enantiomers. It was
shown that (1S,4R)-(+)-camphoroquinone was formed by oxidation of (1S,3R, 4R)-(−)-3-bromocamphor and (1R,4S)-(−)-camphoroquinone from (1R,3S, 4S)-(+)-3-bromocamphor, respectively. Camphor anhydride was a side product (6–10%) of the reaction.
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 50–52, January–February, 2007. 相似文献
93.
聚(C60 甲基丙烯酸甲酯)与聚(C60 苯乙烯)的THF溶液的透射光谱随浓度的增大而不断红移.这种异常的光谱位移可能与富勒烯的纳级(10-9)簇的形成有关.用简单的办法来“调改”一物质的性质是科学家们长期梦寐以求的,而含C60的聚合物正代表了这一群新奇的物质,它们的光学性质可以预期地和可逆地调变,只要简单改变一下浓度. 相似文献
94.
N. Ropson Ph. Dubois R. Jrme Ph. Teyssi 《Journal of polymer science. Part A, Polymer chemistry》1997,35(1):183-192
Homopolymers of adipic anhydride (AA) and block copolymers of ϵ-caprolactone (ϵ-CL) and AA have been synthesized with aluminum triisopropoxide as an initiator. Homopolymerization was studied at 20°C in toluene and methylene chloride (CH2Cl2). The end-group analysis agrees with a coordination insertion mechanism based on the acyl-oxygen cleavage of the AA ring. Living poly(ϵ-caprolactone) (PCL) chains are very efficient macro-initiators for the polymerization of AA, with formation of diblock copolymers of a narrow molecular weight distribution. At our best knowledge, low molecular weight ω-aluminum alkoxide PCL macroinitiators (Mn < 1000) allow the first valuable synthesis of PAA with a molecular weight as high as 58,000 and a quite narrow polydispersity (Mw/Mn = 1.2). Size-exclusion chromatography (SEC) and 13C NMR confirm the blocky structure of the copolymers, in agreement with DSC that shows two melting endotherms and two glass transitions characteristic of the crystalline and amorphous phases of PCL and PAA, respectively. Block copolymers of ϵ-CL and AA are also sensitive to hydrolysis, which makes them possible candidates for biomedical applications. Initiation of the AA polymerization in bulk with aluminum triisopropoxide in the presence of various ligands is also discussed. © 1997 John Wiley & Sons, Inc. 相似文献
95.
本实验测定了二苄基马来酸酯甲醇溶液的荧光光谱,并发现马来酸酐对该荧光体系有猝灭作用,通过对不同马来酸酐浓度与各种浓度的二苄基马来酸酯甲醇溶液在400nm处荧光强度数据的分析,发现马来酸酐的浓度与荧光猝灭程度在一定范围内呈良好的线型关系。据此,提出了用荧光猝灭法对马来酸酐及二苄基马来酸酯的定量分析 相似文献
96.
97.
以邻氨基二苯甲酮为原料,经自身缩合环化合成了3种二苯并[1,5]二氮杂芳辛四烯衍生物(1a~1c);以邻苯二甲酸酐和溴苯为原料经傅-克反应制得中间体2-(4-溴苯甲酰溴)苯甲酸(M1);M1经叠氮化后自缩合制得6,12-二(4-溴苯基)二苯并[b,f][1,5]二氮杂环辛四烯(1d);以邻氨基苯甲酸甲酯为原料,经自身缩合环化制得中间体二苯并[b,f][1,5]二氮杂环辛四烯-6,12(5H,11H)-二酮(M2);M2经氯化合成6,12-二氯二苯并[b,f][1,5]二氮杂环辛四烯(1e),化合物1a~1e的结构经~1H NMR,~(13)C NMR和ESI-MS表征,其中化合物1c为新化合物。利用超临界色谱(SFC)技术对化合物1a~1e实现了手性拆分,获得5对具有高旋光度的光学活性异构体(ee99%)。 相似文献
98.
A new method for constructing the polycyclic skeleton of psiguadial B (1), a meroterpenoid isolated from an evergreen shrub of Myrtaceae, was developed. The terpenoid substructure of 1 was constructed on the basis of a cascade double cyclization reaction of an alkyne dicobalt complex, which afforded the bicyclo[4.3.1]decane derivative having a benzyl group with the correct configuration. The substituted aromatic ring was introduced to the bridgehead position of the intermediate, and bromination under radical conditions followed by intramolecular cyclization reaction resulted in formation of the benzopyran moiety in a stereoselective manner. 相似文献
99.
Improving the water resistance of epoxy–anhydride matrices by the incorporation of bentonite 下载免费PDF全文
Epoxy–anhydride‐based polymers are commonly used as a matrix in pipeline systems exposed to water during their in‐service life. Water absorption at moderate temperatures and/or at long exposure times could lead to irreversible hydrolysis reaction decreasing considerably the polymer overall performance. A strategy to enhance the barrier properties of epoxy resins is to add nanofillers to traditional matrices. In this work, we added bentonite and chemically modified bentonite to this purpose. Water absorption of the resulting materials at three different temperatures (22°C, 80°C, and 93°C) was studied, and simultaneously, the evolution during the immersion tests of glass transition temperature and flexural modulus was recorded. Long‐term gravimetric results showed that composites with chemically modified bentonite produce a delay on the hydrolysis of epoxy–anhydride matrix, which is a relevant result, because of the tough application and uses of the system, from the technological point of view. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
100.
Yo Hiranoi Miho Hatanaka Koji Nakano 《Journal of polymer science. Part A, Polymer chemistry》2017,55(13):2150-2159
Di‐ and trinuclear cobalt (Co)–salen complexes with a benzene ring as a rigid linker were explored for epoxide polymerizations. The dinuclear Co–salen complex with a 1,2‐phenylene linker showed higher catalytic activity than the dinuclear Co–salen complex with a 1,3‐phenylene linker and the trinuclear Co–salen complex with a 1,3,5‐benzenetriyl linker for the copolymerization of propylene oxide (PO) with carbon dioxide. A combination of the absolute configuration of the two Co–salen moieties was found to affect its catalytic activity. The optimized dinuclear Co–salen complex with a heterochiral combination demonstrated highest activity and maintained its catalytic activity under a low catalyst concentration. The heterochiral dinuclear Co–salen complex also showed high activity for the copolymerization of PO with cyclic anhydride. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2150–2159 相似文献