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21.
A novel, rational‐designed approach to access various heteroaryl‐substituted alkyl thioethers was developed via docking‐migration cascade process. By utilizing three components involving alkene, dual‐function reagent, and thioetherificating reagent, radical heteroarylalkylation of alkenes followed by thiolation of the alkyl radical intermediates proceeded smoothly, manifesting well compatibility of substrates and cascade transformations. Furthermore, this protocol also features mild conditions, broad substrate scope, and wide product diversity. 相似文献
22.
X-ray imaging functionalization of biodegradable polyesters is a great demand and challenge in biomedical applications.In this work,a strategy of in-chain functionalization through the combination of ring opening copolymerization and oxime "Click" postfunctionalization was developed towards X-ray opaque polylactide copolymers.A functionalized cyclic carbonate was first synthesized and used as comonomer of polylactide copolymers,which were subjected to postfunctionalization of oxime "Click" reaction towards iodinated polylactide copolymers.The chemical structure and physical properties of the target products were traced and confirmed.In vitro cytotoxicity evaluation with 3T3-Swiss albino by Alamar blue demonstrated a low cytotoxicity.The X-ray radiopacity was analyzed by Micro-CT and quantified by Hounsfield Units value,which could be tailorable by the feedstock.It is a promising X-ray visible implantable biomaterial in biomedical applications. 相似文献
23.
Simen Gjelseth Antonsen Arne Joakim C. Bunkan Tomas Mikoviny Yngve Stenstrøm Armin Wisthaler 《Molecular physics》2020,118(15)
The kinetics of the O3, OH and NO3 radical reactions with diazomethane were studied in smog chamber experiments employing long-path FTIR and PTR-ToF-MS detection. The rate coefficients were determined to be k CH2NN+O3?=?(3.2?±?0.4)?×?10?17 and k CH2NN+OH?=?(1.68?±?0.12)?×?10?10 cm3 molecule?1 s?1 at 295?±?3?K and 1013?±?30 hPa, whereas the CH2NN?+?NO3 reaction was too fast to be determined in the static smog chamber experiments. Formaldehyde was the sole product observed in all the reactions. The experimental results are supported by CCSD(T*)-F12a/aug-cc-pVTZ//M062X/aug-cc-pVTZ calculations showing the reactions to proceed exclusively via addition to the carbon atom. The atmospheric fate of diazomethane is discussed. 相似文献
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《中国化学快报》2020,31(7):1768-1772
In recent years, the research of nitrogen reduction reaction (NRR) under ambient conditions has attracted wide attention for their relatively low energy consumption, in which rational design of electrocatalysts is the key to achieve high-performance NRR. Metal-organic frameworks (MOFs), as a new kind of porous material, have been intensively studied in the past few decades owing to not only their structural versatility and tunability but also intrinsic porosity. Due to their structural features, MOFs also have potential applications in mild condition electrocatalysis of NRR. In this review, the recently experimental and theoretical studies of MOFs in NRR electrocatalysts are briefly summarized. 相似文献
27.
Wei Ouyang Prof. Jongyoon Han 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):11074-11081
Nucleic acid amplification tests (NAATs)integrated on a chip hold great promise for point-of-care diagnostics. Currently, nucleic acid (NA) purification remains time-consuming and labor-intensive, and it takes extensive efforts to optimize the amplification chemistry. Using selective electrokinetic concentration, we report one-step, liquid-phase NA purification that is simpler and faster than conventional solid-phase extraction. By further re-concentrating NAs and performing polymerase chain reaction (PCR) in a microfluidic chamber, our platform suppresses non-specific amplification caused by non-optimal PCR designs. We achieved the detection of 5 copies of M. tuberculosis genomic DNA (equaling 0.3 cell) in real biofluids using both optimized and non-optimal PCR designs, which is 10- and 1000-fold fewer than those of the standard bench-top method, respectively. By simplifying the workflow and shortening the development cycle of NAATs, our platform may find use in point-of-care diagnosis. 相似文献
28.
Chase A. Salazar Joseph J. Gair Kaylin N. Flesch Ilia A. Guzei Jared C. Lewis Shannon S. Stahl 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(27):10965-10969
Mono-N-protected amino acids (MPAAs) are increasingly common ligands in Pd-catalyzed C−H functionalization reactions. Previous studies have shown how these ligands accelerate catalytic turnover by facilitating the C−H activation step. Here, it is shown that MPAA ligands exhibit a second property commonly associated with ligand-accelerated catalysis: the ability to support catalytic turnover at substoichiometric ligand-to-metal ratios. This catalytic role of the MPAA ligand is characterized in stoichiometric C−H activation and catalytic C−H functionalization reactions. Palladacycle formation with substrates bearing carboxylate and pyridine directing groups exhibit a 50–100-fold increase in rate when only 0.05 equivalents of MPAA are present relative to PdII. These and other mechanistic data indicate that facile exchange between MPAAs and anionic ligands coordinated to PdII enables a single MPAA to support C−H activation at multiple PdII centers. 相似文献
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Dr. Yuan Liu Dr. Jin-Cheng Liu Teng-Hao Li Zeng-Hui Duan Dr. Tian-Yu Zhang Ming Yan Dr. Wan-Lu Li Prof. Dr. Hai Xiao Prof. Dr. Yang-Gang Wang Prof. Dr. Chun-Ran Chang Prof. Dr. Jun Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18745-18749
The direct, nonoxidative conversion of methane on a silica-confined single-atom iron catalyst is a landmark discovery in catalysis, but the proposed gas-phase reaction mechanism is still open to discussion. Here, we report a surface reaction mechanism by computational modeling and simulations. The activation of methane occurs at the single iron site, whereas the dissociated methyl disfavors desorption into gas phase under the reactive conditions. In contrast, the dissociated methyl prefers transferring to adjacent carbon sites of the active center (Fe1©SiC2), followed by C−C coupling and hydrogen transfer to produce the main product (ethylene) via a key −CH−CH2 intermediate. We find a quasi Mars–van Krevelen (quasi-MvK) surface reaction mechanism involving extracting and refilling the surface carbon atoms for the nonoxidative conversion of methane on Fe1©SiO2 and this surface process is identified to be more plausible than the alternative gas-phase reaction mechanism. 相似文献