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41.
Diaryl ditellurides were conveniently reduced by a system consisting of samarium and zirconium tetrachloride in tetrahydrofuran to produce samarium aryltellurolates. This new tellurolate anion species reacted smoothly with α, β-unsaturated esters (and nitriles) to give β-telluroesters (and nitriles) in good yields. 相似文献
42.
43.
Davide Toniolo Aurélien R. Willauer Dr. Julie Andrez Yan Yang Dr. Rosario Scopelliti Prof. Laurent Maron Prof. Marinella Mazzanti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(33):7831-7834
The activation of CS2 is of interest in a broad range of fields and, more particularly, in the context of creating new C−C bonds. The reaction of the dinuclear ytterbium(II) complex [Yb2L4], 1 , [L=(OtBu)3SiO−] with carbon disulfide led to the isolation of unprecedented reduction products. In particular, the crystallographic characterization of complex [Yb2L4(μ-C2S2)], 2 , provided the first example of an acetylenedithiolate ligand formed from metal reduction of CS2. Computational studies indicated that this unprecedented reactivity can be ascribed to the unusual binding mode of CS22− in the isolated “key intermediate” [Yb2L4(μ-CS2)], 3 , which results from the dinuclear nature of 1 . 相似文献
44.
Mengmeng Ma Ying Wang Nan Gao Xinping Liu Yuhuan Sun Prof. Jinsong Ren Prof. Dr. Xiaogang Qu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11852-11858
Proteolysis of amyloid-β (Aβ) is a promising approach against Alzheimer's disease. However, it is not feasible to employ natural hydrolases directly because of their cumbersome preparation and purification, poor stability, and hazardous immunogenicity. Therefore, artificial enzymes have been developed as potential alternatives to natural hydrolases. Since specific cleavage sites of Aβ are usually embedded inside the β-sheet structures that restrict access by artificial enzymes, this strongly hinders their efficiency for practical applications. Herein, we construct a NIR (near-IR) controllable artificial metalloprotease (MoS2-Co) using a molybdenum disulfide nanosheet (MoS2) and a cobalt complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (Codota). Evidenced by detailed experimental and theoretical studies, the NIR-enhanced MoS2-Co can circumvent the restriction by simultaneously inhibition of β-sheet formation and destroying β-sheet structures of the preformed Aβ aggregates in living cell. Furthermore, our designed MoS2-Co is an easy to graft Aβ-target agent that prevents misdirected or undesirable hydrolysis reactions, and has been demonstrated to cross the blood brain barrier. This method can be adapted for hydrolysis of other kinds of amyloids. 相似文献
45.
Dr. Mads Østergaard Dr. Narendra Kumar Mishra Prof. Dr. Knud J. Jensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(38):8341-8357
Insulin is a small protein crucial for regulating the blood glucose level in all animals. Since 1922 it has been used for the treatment of patients with diabetes. Despite consisting of just 51 amino acids, insulin contains 17 of the proteinogenic amino acids, A- and B-chains, three disulfide bridges, and it folds with 3 α-helices and a short β-sheet segment. Insulin associates into dimers and further into hexamers with stabilization by Zn2+ and phenolic ligands. Selective chemical modification of proteins is at the forefront of developments in chemical biology and biopharmaceuticals. Insulin's structure has made it amenable to organic and inorganic chemical reactions. This Review provides a synthetic organic chemistry perspective on this small protein. It gives an overview of key chemical and physico-chemical aspects of the insulin molecule, with a focus on chemoselective reactions. This includes N-acylations at the N-termini or at LysB29 by pH control, introduction of protecting groups on insulin, binding of metal ions, ligands to control the nano-scale assembly of insulin, and more. 相似文献
46.
Qing Liu Yibin Liu Hua Zheng Chunmei Li Yi Zhang Qiuyu Zhang 《Journal of polymer science. Part A, Polymer chemistry》2020,58(8):1092-1104
Thermoset polymer elastomers that are capable of autonomous repairability upon physical damage at ambient temperature are highly desirable because of their thermal and environmental resistance, outstanding mechanical toughness and stability. To aim at this goal, we demonstrated that tris(diethylamino)phosphine was initially proven as an efficient catalyst for the aliphatic disulfide exchange at mild condition. By making use of the aliphatic disulfide bond reshuffling and elasticity of polyurethane elastomers, the inherently cross-linked polysulfide-based poly(thiourethane-urethane) elastomers were prepared and exhibited the ability to mend without extrinsic stimuli in the presence of phosphorus catalyst at room temperature after artificially damaged. The self-healing efficiency via the mechanical recovery approach was investigated to be mainly dependent upon the cross-linking density of polysulfide and hard segments chemistry, which in turns determined the molecular chain diffusion and reshuffling that was corroborated by the stress-relaxation study. The thermoset elastomer based on asymmetric diisocynate showed a maximum self-healing efficiency of 85.6% compared to 71.6% for the elastomer with symmetric monomer building blocks. The self-healable polymer was confirmed to be recyclable and reprocessable through a cut-compression processing cycle under a quite mild pressure and temperature thanks to the disulfide bond reshuffling. Meanwhile, the recycled thermoset elastomer well maintained the mechanical properties to its original material. 相似文献
47.
Copper‐Catalyzed Reaction Cascade of Thiophenol Hydroxylation and S‐Arylation through Disulfide‐Directed C−H Activation
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Prof. Dr. Dawei Wang Xin Yu Wei Yao Wenkang Hu Chenyang Ge Prof. Dr. Xiaodong Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(16):5543-5546
Copper‐catalyzed thiophenol C?H activation is described. Through an initial attempt to conduct C‐arylation with arylboronic acid, a rather surprising sequential C?H activation and S‐arylation was discovered. Mechanistic investigation revealed the disulfide intermediate as the key component in directing C?H oxidation. The overall reaction proceeded under mild conditions with molecular oxygen as the oxidant. Discovery of disulfide as the directing group provides a potential new direction for catalytic C?H functionalization under mild conditions. 相似文献
48.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1119-1134
Abstract The degree of randomization, q, of structural units in melt blends of the polysulfide homopolymers A(PS1) and B(PS2), wherein the disulfide equivalents D A/D B = 1, were studied by electron ionization mass spectrometry. Over the temperature range of 207–219°C, the relaxation process, due to the dominant disulfide–disulfide interchange reactions, is postulated to follow an associative reaction mechanism. These intermolecular disulfide–disulfide interactions promote a transient enhancement of the sulfur rank in the activated complex resulting in formation of the randomized co‐polymer AB. The mass spectrometric experimental design enabled measurement of concentrations of reactants A(PS1) and B(PS2), as well as the randomized copolymer AB, by monitoring the abundance of dimer units a2, b2, and ab, respectively as a function of time. The degree of randomization, q, was observed in the absence of catalysts or solvents, notwithstanding the solvent/solute and solute/solvent characteristics of the polymer melt blend. The mechanism of this randomization process, was rationalized on the basis of the properties of sulfur, aided by the observation of macrocyclic monomeric and dimeric units during the retro‐polymerization reactions under the EI/MS conditions employed. The model polysulfide polymers A(PS1) and B(P52), used in this study were synthesized from bis(2‐chloroethyl)ether and bis(2‐chloro ethoxy)methane, respectively. 相似文献
49.
Yuping Liu Hongxing Wang Fengru Liu Jialing Kang Dr. Feng Qiu Prof. Changchun Ke Dr. Yu Huang Prof. Sheng Han Prof. Fan Zhang Prof. Xiaodong Zhuang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2155-2164
Transition metal-based nanoparticle-embedded carbon materials have received increasing attention for constructing next-generation electrochemical catalysts for energy storage and conversion. However, designing hybrid carbon materials with controllable hierarchical micro/mesoporous structures, excellent dispersion of metal nanoparticles, and multiple heteroatom-doping remains challenging. Here, a novel pyridinium-containing ionic hypercrosslinked micellar frameworks (IHMFs) prepared from the core–shell unimicelle of s-poly(tert-butyl acrylate)-b-poly(4-bromomethyl) styrene (s-PtBA-b-PBMS) and linear poly(4-vinylpyridine) were used as self-sacrificial templates for confined growth of molybdenum disulfide (MoS2) inside cationic IHMFs through electrostatic interaction. After pyrolysis, MoS2-anchored nitrogen-doped porous carbons possessing tunable hierarchical micro/mesoporous structures and favorable distributions of MoS2 nanoparticles exhibited excellent electrocatalytic activity for hydrogen evolution reaction as well as small Tafel slope of 66.7 mV dec−1, low onset potential, and excellent cycling stability under acidic condition. Crucially, hierarchical micro/mesoporous structure and high surface area could boost their catalytic hydrogen evolution performance. This approach provides a novel route for preparation of micro/mesoporous hybrid carbon materials with confined transition metal nanoparticles for electrochemical energy conversion. 相似文献
50.
Dongyao Li Chunmiao Ma Prof. Junfeng Xiang Kai Zhang Ling Yang Prof. Quan Gan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(45):11663-11669
A strategy to reversibly switch the parallel/antiparallel helical conformation of aromatic double helices through the formation/breakage of a disulfide bond is presented. Single-crystal X-ray structures, NMR, and circular dichroism spectroscopy demonstrate that the double helices with terminal thiol groups favor an antiparallel helical arrangement both in the solid state and in solution, while the P/M bias of helicity induced by chiral segments from another extremity of the sequence is weak in this structural motif. The antiparallel helices can be rearranged to parallel helices through the disulfide connection of the sequences. This change enhances the bias of helical handedness and results in absolute chirality control of the double helices. The handedness-mediated process can be governed by the oxidation-reduction cycle, thereby switching the structural arrangement and the enhancement of chiral bias. In addition, we find that the sequences can dimerize into an intermolecular double helix with the disulfide connection. And the helical handedness is also fully controlled due to the head-to-head structural motif. 相似文献