This work is focused on montmorillonite (MMT)‐based “support‐activators” (S‐As) for the metallocene‐catalyzed propylene polymerization. This catalyst was previously industrialized; however, for further technological advances, the activation mechanism is investigated. The chemical and morphological requirements of the S‐A are surveyed using both commercially available raw clay minerals (non‐acid‐treated) and acid‐treated clay minerals. The S‐A possessing strong‐acid sites (pK a < ?8.2) gives a highly active catalyst. Acid treatment of MMT induces morphological changes as well as the formation of strong acid sites. Based on pore size distribution analysis and atomic force microscopy observations, it is concluded that the strong acid sites are located in the small pores around the edge of the clay mineral (not in the interlayer), where the structure is disordered by the acid treatment.
The possible inclusion complexes of Cp2NbCl2 into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, 1H NMR solution and solid state 13C CP-MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp2NbCl2. Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp2NbCl2, a band between 500 and 850 cm−1 characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp2NbCl2) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp2NbCl2(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp2NbCl2(OH). Solid State 13C CP-MAS NMR and solution 1H NMR spectroscopies together with ab-initio results showed that Cp2NbCl2 is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution 1H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp2NbCl2 in CDCl3 solution. Cp2NbCl2 is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp2NbCl2 into the cavity. 相似文献
A new synthesis of spirocyclic oxindole analogue spiro[piperidine-4,3’-pyrrolo[2,3-b]pyridin]-2’(1’H)-one 1 is described.The key steps involve dialkylation of arylacetonitrile and cyclization of the azaoxindole ring by an intramolecular Buchwald-Hartwig amidation of carboxylic ami Je and aryl chloride.A small library was obtained by reductive amination of 1 with various aldehydes and was screened against human lung cancer cell A549,human liver cancer cell BEL7402,and human colon cancer cell HCT-8.The results show that most of the 1(?)rary compounds 2 have some inhibitory activities.2-(Trifluoromethoxy) benzylic substituted spirocyclic azaoxindole 2e was identified as a nanomolar inhibitor against human lung cancer cell A-549(IC50=50 nmol/L). 相似文献
A facile microwave-assisted procedure for synthesis of novel fluorinated pyrazolo[3, 4-d]pyrimidine derivatives containing 1, 3, 4-thiadiazole is described. This protocol presented such advantages as short reaction time, high yields, simple purification and environmentally benign procedures. Their antitumor activities were evaluated against HL-60 by an MTT assay. The preliminary results indicated that some title compounds exhibit more potent antitumor inhibitory activity than doxorubicin (DOX). 相似文献