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601.
1 INTRODUCTION Low-valent titanium reagents have exceedinglyhigh abilities to promote reductive coupling of car-bonyl compounds and they are attracting increasinginterest in organic synthesis[1]. Many other func-tional groups can also be coupled[2~8]. Recently, wehave reported some intermolecular reductive cou-pling reactions[9~12] and some new intramolecular re-ductive coupling reactions[13~16] induced by low-va-lent titanium reagents. The spiro[4.4]nonane skeleton has been found inmany… 相似文献
602.
Nonionic fluorinated surfactant: investigation of phase diagram and preparation of ordered mesoporous materials 总被引:2,自引:0,他引:2
The behavior of fluorinated surfactant F(CF2)8C2H4(OC2H4)9OH in water solution was investigated, and the preparation ofmesoporous molecular sieves was achieved. A direct micellar phase (L1) and a hexagonal (H1) liquid crystal were found. Small-angle X-ray scattering measurements proved that the hydrophobic chains are completely extended and that the cross sectional area remains constant in H1. At 80 degrees C, materials with a hexagonal array of their channel are prepared via a cooperative templating type mechanism in a wide range of surfactant concentrations (5-20 wt %). Decreasing the hydrothermal temperature leads to the formation ofwormhole-like structure. In this case the channel arrangement is no longer governed by the surfactant behavior but by the silica condensation and polymerization. An increase of the mean pore diameter with heating temperature is noted. This result is associated with changes of aggregation number with temperature. A comparison of the characteristics of the materials obtained with both hydrogenated and fluorinated surfactants is also made. 相似文献
603.
1 INTRODUCTION The insertion of unsaturated molecules into the lanthanide-ligand bond has attracted considerable attention, because it is a fundamental step for many metal-promoted transformations, in which some va- luable new methods for the formation of carbon- carbon and carbon-heteroatom bonds can be deve- loped and some complexes with novel structures or peculiar characters can be obtained[1~4]. Notably, in contrast to the wide reaction chemistry of organo- lanthanide alkyl (aryl), am… 相似文献
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1 INTRODUCTION4,4' bipyridine( bipy) is a good candidate for building open framework struc ture because of their rodlike rigidity and length.Framework structures formed bytransition metalsbridged by bipy vary with metaland anion.The structures of Zn bipy system include interpenetrating square grid sheets〔 Zn( bipy) 2 ( H2 O) 2 〕Si F6〔1〕,two dimensionallayer〔 Zn( bipy) ( H2 O) 4 〕( NO3) 2 · bipy〔2〕,〔 Zn( bipy) ( H2 O) 4 〕 ( NO3) 2 · 2 bipy· 3 H2 O〔2〕 and〔 Zn( bipy)… 相似文献
606.
采用蒸发溶剂促进插层(evaporating solvent enhanced intercalation)的方法把农药阿维菌素(Avermectin, AVM)插层到十二烷基硫酸钠(SDS)改性的类水滑石(Hydrotalcite-like compound, HTlc)层间,合成了AVM-SDS-HTlc纳米杂化物。研究发现其能够很好的控制阿维菌素的释放,表明AVM-SDS-HTlc纳米杂化物是一种很有潜力的农药控释剂型。AVM-SDS-HTlc纳米杂化物的释放受pH、温度和电解质的影响,酸性介质、较高温度以及有电解质存在会提高其缓释速率。释放过程符合准一级释放动力学,释放的活化能为279 kJ/mol。 相似文献
607.
Yue Jun Zhu~a Ye Bang Tan~ 《中国化学快报》2008,19(3):355-358
Novel double hydrophilic block copolymers with amine pendant chains were synthesized by polymerization of 4-vinyl benzylamine hydrochloric salt using 4,4′-azo-bis[4-cyanopentanoate poly(ethylene glycol) ester] as macroazoinitiator. The structures of the copolymers were characterized by ^1H NMR, FTIR spectra and acid-base titration, GPC-MALS techniques. 相似文献
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ZHAO Dong-Baoa c JIANG Yan-Fengb XI Chan-Juanb LIU Xiu-Huac② WANG Han-Qinga a 《结构化学》2005,24(6):637-640
1 INTRODUCTION The whole body of herb of Artemisia Ordosica Kraschen (Artemisia genus of Compositae) has been long used to treat rheummarthritis, parotitis, intestinal obstruction as well as to stop bleeding in traditional Chinese medicine[1]. In our systematic studies of active metabolites, we have isolated seve- ral compounds from ethanol extracts of this plant[2], including flavones, flavanones, an isocoumarine, and capillarin. Coumarines commonly occur in na- tural plants as metabo… 相似文献