نتایج جستجو برای: lewis acid catalyst
تعداد نتایج: 798753 فیلتر نتایج به سال:
There is significant interest in broadening the type of catalyst substrates that support the growth of high-quality carbon nanotube (CNT) carpets. In this study, ion beam bombardment has been utilized to modify catalyst substrates for CNT carpet growth. Using a combination of contact angle measurements (CAMs) and X-ray reflectivity (XRR) for the first time, new correlations between the physicoc...
This review describes our recent efforts in the development of acid-base organocatalysts, (S)-3-(N-isopropyl-N-3-pyridinylaminomethyl) BINOL (6a) and (S)-3-[2-(diphenylphosphino)phenyl] BINOL (13a), with dual activation mechanism for the aza-Morita-Baylis-Hillman (aza-MBH) reaction. In these catalysts, chiral Brønsted acid units are connected with a Lewis base unit via a spacer. The acid-base m...
The skeletal isomerisation of n-butenes to isobutene has been carried out over ferrierite catalysts (Si/Al ~ 15) containing different acid sites distribution and different amount of defects. The zeolite crystals were synthesised under hydrothermal conditions in fluoride medium in the absence of alkaline cations by using suitable combinations of structure directing agents. Template-driven low de...
10-bromo-1,8-dihydroxy-9-anthrone (10-bromoanthralin) was synthesized with precise ratio of bromine to anthralin (1.10:1), respectively. With this ratio of the reagents, the reaction is repetitive at any scale. This compound is a highly significant intermediate for the synthesis of many anthralin derivetised antipsoriatic drugs. Bromination at both benzylic and aromatic ring positions of anthra...
An effective synthesis of nucleosides using glycosyl chlorides as glycosyl donors in the absence of Lewis acid has been developed. Glycosyl chlorides have been shown to be pivotal intermediates in the classical silyl-Hilbert-Johnson reaction. A possible mechanism that differs from the currently accepted mechanism advanced by Vorbrueggen has been proposed and verified by experiments. In practice...
The first example of the boron Lewis acid catalyzed C(sp2)-H functionalization of cyclic enones was achieved using diazoacetates. The insertion of the carbon atom of diazoacetates utilizes BF3•Et2O or a newly designed oxazaborolidinium ion as a catalyst to afford β-functionalized cyclic enones from simple cyclic enones in a single step and high yields. The reaction mechanism was investigated wi...
The combinations of 1-butyl-3-methylimidazolium chloride with NbCl5 yielded ionic mixtures with different melting point temperatures and acidity depending on the niobium molar fraction. The mixtures were characterized by thermal (DSC) and spectroscopic (FT-IR and H NMR) analysis. The Pechmann reactions of different phenols with ethylacetoacetate, producing coumarins, was used as model to evalua...
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