共查询到20条相似文献,搜索用时 0 毫秒
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(28):8303-8307
It is challenging to prepare co‐organized nanotube systems with controlled nanoscale chirality in an aqueous liquid flow field. Such systems are responsive to a bubbled external gas. A liquid vortex induced by bubbling carbon dioxide (CO2) gas was used to stimulate the formation of nanotubes with controlled chirality; two kinds of achiral cationic building blocks were co‐assembled in aqueous solution. CO2‐triggered nanotube formation occurs by formation of metastable intermediate structures (short helical ribbons and short tubules) and by transition from short tubules to long tubules in response to chirality matching self‐assembly. Interestingly, the chirality sign of these assemblies can be selected for by the circulation direction of the CO2 bubble‐induced vortex during the co‐assembly process. 相似文献
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Woo‐Jin Yoo Junpei Kondo Jos A. Rodríguez‐Santamaría Thanh V. Q. Nguyen Sh Kobayashi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(20):6844-6847
A facile synthetic procedure for the preparation of α‐trifluoromethyl carboxylic acids and esters was achieved through multicomponent coupling reactions between gem‐difluoroalkenes, cesium fluoride, and carbon dioxide. The products were generated in moderate to excellent yields, and the synthetic utility of this method was demonstrated through the preparation of trifluoromethylated versions of popular nonsteroidal anti‐inflammatory drugs (NSAIDs). 相似文献
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Arnaud Thevenon Alonso Rosas‐Hernndez Jonas C. Peters Theodor Agapie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(47):17108-17114
Bridging homogeneous molecular systems with heterogeneous catalysts is a promising approach for the development of new electrodes, combining the advantages of both approaches. In the context of CO2 electroreduction, molecular enhancement of planar copper electrodes has enabled promising advancement towards high Faradaic efficiencies for multicarbon products. Besides, nanostructured copper electrodes have also demonstrated enhanced performance at comparatively low overpotentials. Herein, we report a novel and convenient method for nanostructuring copper electrodes using N,N′‐ethylene‐phenanthrolinium dibromide as molecular additive. Selectivities up to 70 % for C≥2 products are observed for more than 40 h without significant change in the surface morphology. Mechanistic studies reveal several roles for the organic additive, including: the formation of cube‐like nanostructures by corrosion of the copper surface, the stabilization of these nanostructures during electrocatalysis by formation of a protective organic layer, and the promotion of C≥2 products. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(35):10695-10699
Ionic liquids (ILs) are versatile solvents and catalysts for the synthesis of quinazoline‐2,4‐dione from 2‐aminobenzonitrile and CO2. However, the role of the IL in this reaction is poorly understood. Consequently, we investigated this reaction and showed that the IL cation does not play a significant role in the activation of the substrates, and instead plays a secondary role in controlling the physical properties of the IL. A linear relationship between the pK a of the IL anion (conjugate acid) and the reaction rate was identified with maximum catalyst efficiency observed at a pK a of >14.7 in DMSO. The base‐catalyzed reaction is limited by the acidity of the quinazoline‐2,4‐dione product, which is deprotonated by more basic catalysts, leading to the formation of the quinazolide anion (conjugate acid pK a 14.7). Neutralization of the original catalyst and formation of the quinazolide anion catalyst leads to the observed reaction limit. 相似文献
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《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(35):10466-10470
A novel methodology using CsF⋅Al2O3 as a highly efficient, environmentally benign, and reusable solid‐base catalyst was developed to synthesize glutamic acid derivatives by stereoselective 1,4‐addition of glycine derivatives to α,β‐unsaturated esters. CsF⋅Al2O3 showed not only great selectivity toward 1,4‐addtion reactions by suppressing the undesired formation of pyrrolidine derivations by [3+2] cycloadditions, but also offered high yields for the 1,4‐adduct with excellent anti diastereoselectivities. The catalyst was well characterized by using XRD, 19F MAS‐NMR and 19F NMR spectroscopy, FT‐IR, CO2‐TPD, and XPS. And highly basic F from Cs3AlF6 was identified as the most probable active basic site for the 1,4‐addition reactions. Continuous‐flow synthesis of 3‐methyl glutamic acid derivative was successfully demonstrated by using this solid‐base catalysis. 相似文献
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