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排序方式: 共有594条查询结果,搜索用时 93 毫秒
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Electrochemical Vicinal Difluorination of Alkenes: Scalable and Amenable to Electron-Rich Substrates
Sayad Doobary Alexi T. Sedikides Henry P. Caldora Dr. Darren L. Poole Dr. Alastair J. J. Lennox 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1171-1176
Fluorinated alkyl groups are important motifs in bioactive compounds, positively influencing pharmacokinetics, potency and conformation. The oxidative difluorination of alkenes represents an important strategy for their preparation, yet current methods are limited in their alkene-types and tolerance of electron-rich, readily oxidized functionalities, as well as in their safety and scalability. Herein, we report a method for the difluorination of a number of unactivated alkene-types that is tolerant of electron-rich functionality, giving products that are otherwise unattainable. Key to success is the electrochemical generation of a hypervalent iodine mediator using an “ex-cell” approach, which avoids oxidative substrate decomposition. The more sustainable conditions give good to excellent yields in up to decagram scales. 相似文献
23.
Martin Sweeney Darren Conboy Styliana I. Mirallai Fawaz Aldabbagh 《Molecules (Basel, Switzerland)》2021,26(9)
This review article provides a perspective on the synthesis of alicyclic and heterocyclic ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles, and imidazo[5,4-f]benzimidazoles. These heterocycles have a plethora of biological activities with the iminoquinone and quinone derivatives displaying potent bioreductive antitumor activity. Synthesis is categorized according to the cyclization reaction and mechanisms are detailed. Nitrobenzene reduction, cyclization of aryl amidines, lactams and isothiocyanates are described. Protocols include condensation, cross-dehydrogenative coupling with transition metal catalysis, annulation onto benzimidazole, often using CuI-catalysis, and radical cyclization with homolytic aromatic substitution. Many oxidative transformations are under metal-free conditions, including using thermal, photochemical, and electrochemical methods. Syntheses of diazole analogues of mitomycin C derivatives are described. Traditional oxidations of o-(cycloamino)anilines using peroxides in acid via the t-amino effect remain popular. 相似文献
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Abstract The symmetric 'end-off' compartmental proligand 2,6-[N,N′-bis(2-hydroxy-phenylmethyl)-N,N′-bis(2-pyridylmethyl)aminomethyl]-4-methylphenol (H3L) has been used to generate homodinuclear nickel(II) and zinc(II) complexes. The crystal structures of the complexes reveal that the di-nickel(II) complex is donor asymmetric and the di-zinc(II) complex is coordination number asymmetric. In both complexes non-coordinated acetic acid molecules are tightly hydrogen-bonded to the pendant phenols of the ligand generating a double acid salt of the type[CH3COO…H…L…H…OOCCH3]3? in the dinickel complex and a single acid salt of the type [CH3COO…H…L]3? in the dizinc complex. In both cases the ligand periphery has been extended to provide a supraligand in which the donor potential of the original ligand has been enhanced. 相似文献
26.
Hierarchical graphene oxide (GO)‐TiO2 composite microspheres with different GO/TiO2 mass ratios were successfully prepared by mixing GO and TiO2 microspheres under ultrasonic conditions. Ultrasonication helped the GO and TiO2 microsphere to uniformly mix on the microscale. The results showed that the GO‐TiO2 composites that were prepared by ultrasonic mixing exhibited significantly higher hydrogen‐evolution rates than those that were synthesized by simple mechanical grinding, owing to synergetic effects, including enhanced light absorption and scattering, as well as improved interfacial charge transfer because of the excellent contact between the GO sheets and TiO2 microspheres. In addition, GO‐TiO2‐3 (3 wt. % GO) showed the highest hydrogen‐generation rate (305.6 μmol h?), which was about 13 and 3.3‐times higher than those of TiO2 microsphere and GO‐P25 (with 3 wt. % GO), respectively. Finally, a tentative mechanism for hydrogen production is proposed and supported by photoluminescence and transient photocurrent measurements. This work highlights the potential applications of GO‐TiO2 composite microspheres in the field of clean‐energy production. 相似文献
27.
A short and efficient synthesis of the potent 5-lipoxygenase inhibitor CMI-977 is described using as the key step a stereoselective anomeric oxygen to carbon rearrangement of an alkynyl stannane tetrahydrofuranyl ether derivative mediated by boron trifluoride etherate. 相似文献
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Nissa C. Frank Dr. Darren J. Mercer Prof. Dr. Stephen J. Loeb 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14076-14080
New dibenzo[24]crown‐8 ether derivatives were prepared that contain appendages with thioether donors that can coordinate to a metal ion. These macrocycles were then combined with 1,2‐bis(pyridinium) ethane axles to create two types of [2]rotaxane ligands; those with the four thioether donors on the crown ether and those with six donor groups, four from the crown ether and two more attached to the stoppering groups of the dumbbell. The crown ethers and both types of [2]rotaxane ligands were allowed to react with AgI ions to form metal‐organic rotaxane framework (MORF) style coordination polymers. The interlocked hexadentate ligand forms the first example of a new type of lattice containing interwoven frameworks resulting from both interpenetration of frameworks due to the presence of an interlocked ligand and more classical interpenetration of independent frameworks. 相似文献
30.
Kyriakos C. Stylianou John Bacsa Darren Bradshaw Matthew J. Rosseinsky 《无机化学与普通化学杂志》2014,640(11):2123-2131
The reaction of NiII with a tetra‐benzoate pyrene ligand produces a 3D porous framework based on infinite 1D NiII chains. The NiII–O connectivity and the formation of a hydroxo‐bridge (μ3‐OH) responsible for the connection of the central NiII atoms within the 1D NiII–(μ3‐OH)2–NiII chains can be straightforwardly compared with the TiIV–O–TiIV connectivity seen in TiO2. The arrangement of the TBAPy ligand around the 1D rutile‐based chains leads in the generation of a porous framework with two distinct types of pores; based on the chemistries of these two types of pores, one can be labelled as hydrophobic and the other as hydrophilic. The use of different activation methods results in the generation of either a porous framework free of guest molecules or a completely solvent‐free material, in which the terminal H2O molecules bound to NiII were removed, leading thus to a framework with open NiII sites. CO2 isotherms collected on both frameworks at 195 K and one barshowed type I isotherms characteristic of microporous materials (BET surface areas for: guest‐free framework: 257(3) m2 · g–1; solvent‐free framework: 362(2) m2 · g–1). The affinity of both networks at zero coverage for both CO2 and CH4 was found to be greater when the unsaturated NiII sites are available within the void space. 相似文献