α-Aminoradicals undergo halogen atom abstraction to form halomethyl radicals in reactions initiated by the combination of tert-butyl hydroperoxide, aliphatic trialkylamine, halocarbon, and copper(I) iodide. The formation of the α-aminoradical circumvents preferential hydrogen atom transfer in favor of halogen atom transfer, thereby releasing the halomethyl radical for addition to alkenes. The resulting radical addition products add the tert-butylperoxy group to form αperoxy-β,β-dichloropropylbenzene products that are convertible to their corresponding β,β-dichloro-alcohols and to novel pyridine derivatives. Computational analysis clearly explains the deviation from traditional HAT of chloroform and also establishes formal oxidative addition/reductive elimination as the lowest energy pathway.
Amorphous molybdenum sulfide/carbon black (MoSx/C) nanocomposites are synthesized by a facile one-step γ-ray radiation induced reduction process. Amorphous MoSx shows better intrinsic activity than crystalline MoS2. And the composition and amorphous structure of MoSx could be expediently tuned by absorbed dose for excellent catalytic activity. Meanwhile, the addition of carbon black leads to a significant decrease of charge transfer resistance and increase of active sites of MoSx/C composite. Consequently, MoSx/C nanocomposite shows Pt-like catalytic activity towards hydrogen evolution reaction (HER), which requires an onset over potential of 40 mV and over potential of 76 mV to achieve a current density of 10 mA cm−2, and the corresponding Tafel slope is 48 mV decade−1. After 6000 CV cycles, the catalytic activity of MoSx/C shows no obvious decrease. However, when platinum (Pt) foil is used as counter electrode, MoSx/C composite show better catalytic activity abnormally after long-term cycling tests. The dissolution of Pt was observed in HER and the Pt dissolution mechanism is elucidated by further analyzing the surface composition of after-cycling electrodes, which offers highly valuable guidelines for using Pt electrode in HER.
A bulky
and electron-rich N-heterocyclic carbene–palladium
complex (SIPr)Ph2
Pd(cin)Cl was synthesized and
characterized. It was found to be highly efficient and versatile for
the coupling of different (hetero)aryl chlorides with various (hetero)aryl
amines at room temperature, especially for the challenging amination
of five- or six-membered ring heteroaryl chlorides with five- or six-membered
ring heteroaryl amines. It was also successfully applied with high
yields to the synthesis of various commercial pharmaceuticals and
candidate drugs or compounds with potential pharmacological activities.
All of these demonstrate its excellent catalytic efficacy in Buchwald–Hartwig
amination and broad application prospects in relevant pharmaceutical
preparations. DFT calculations suggest that the steric-induced electronic
interaction makes the ligand more electron-donating, and the steric
effect effectively regulates the rotation of the iPr-Ph-iPr group in the catalyzed system due to the
introduction of the diphenyl skeleton. Considering the electronic
effect and the steric effect together, the oxidative addition activation
barriers of the (SIPr)Ph2
and (SIPr) ligands
are close to each other. Reductive elimination is the rate-determining
step of the (SIPr)Ph2
Pd(cin)Cl-catalyzed system
in the catalytic cycle, and the appropriate steric hindrance of the
(SIPr)Ph2
ligand greatly reduces the energy
barrier of this step. The perfect combination of the electron-donating
and steric hindrance abilities of the ligand significantly improves
the catalytic activity.
The adsorption of lithium ions(Li+) and the separation of lithium isotopes have attracted interests due to their important role in energy storage and nuclear energy, respectively. However, it is still challenging to separate the Li+ and its isotopes with high efficiency and selectivity. A novel cellulose-based microsphere containing crown ethers groups (named as MCM-g-AB15C5) was successfully synthesized by pre-irradiation-induced emulsion grafting of glycidyl methacrylate (GMA) and followed by the chemical reaction between the epoxy group of grafted polymer and 4′-aminobenzo-15-crown-5 (AB15C5). By using MCM-g-AB15C5 as adsorbent, the effects of solvent, metal ions, and adsorption temperature on the adsorption uptake of Li+ and separation factor of 6Li/7Li were investigated in detail. Solvent with low polarity, high adsorption temperature in acetonitrile could improve the uptake of Li+ and separation factor of lithium isotopes. The MCM-g-AB15C5 exhibited the strongest adsorption affinity to Li+ with a separation factor of 1.022 ± 0.002 for 6Li/7Li in acetonitrile. The adsorption isotherms in acetonitrile is fitted well with the Langmuir model with an ultrahigh adsorption capacity up to 12.9 mg·g−1, indicating the unexpected complexation ratio of 1:2 between MCM-g-AB15C5 and Li+. The thermodynamics study confirmed the adsorption process is the endothermic, spontaneous, and chemisorption adsorption. As-prepared novel cellulose-based adsorbents are promising materials for the efficient and selective separation of Li+ and its isotopes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.