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排序方式: 共有123条查询结果,搜索用时 15 毫秒
1.
Recycling Chiral Organocatalyst (4S)-Phenoxy-(S)-proline for Direct Asymmetric Aldol Reaction in Ionic Liquid (bmim)PF6 总被引:1,自引:0,他引:1
Room temperature ionic liquid (bmim)PF6 was evaluated for recycling an organocatalyst (4S)-phenoxy-(S)-proline for direct asymmetric aldol reactions. The desired aldol products were obtained with good yields up to 93.2% and enantioselectivities up to 88.5%, and isolation of the products by simple extraction allowed recycling the ionic liquid containing the immobilized catalyst in subsequent reactions without significant decrease of yields and enantioselectivities. 相似文献
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Houjou H Kanesato M Hiratani K Mandon D 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(18):4576-4583
Novel diiron complexes with an Fe2(mu-OMe)2 core were studied as models of the active site of nonheme iron-containing enzymes. X-ray crystal structures of the complexes showed the existence of two types of ligand folding-parallel and twisted-both of which have four virtually equivalent phenolato groups sticking out from the Fe2O2 rhombic plane. Cyclic voltammetry measurements revealed two or more distinct redox waves in a region of relatively high potential, in addition to known Fe(II)/Fe(III) redox waves in a region of lower potential. These new peaks were assigned to the high-valence state of iron atoms, that is, Fe(III)Fe(IV) and Fe(IV)Fe(IV), resonating with the phenoxyl radical(s). The split width of the redox waves ranged from 0.14 to 0.20 eV, which may be a measure of the electronic interaction of the phenolate groups through the Fe2(mu-OMe)2 core. 相似文献
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A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:13,14-tribenzo-9,12-dioksa-cyclopentadeca-1,5-diene was synthesized by reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane. Then, its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes were synthesized by the template effect by the reaction of 2,6-diaminopyridine and 1,2-bis(2-carboxyaldehyde phenoxy)ethane and Cu(NO3)2 · 3H2O, Ni(NO3)2 · 6H2O, Pb(NO3)2, Co(NO3)2 · 6H2O, La(NO3)3 · 6H2O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, 1H and 13C NMR, UV-Vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements, mass spectra, and cyclic voltammetry. All complexes are diamagnetic and Cu(II) complex is binuclear. The Co(II) was oxidized to Co(III). The comparative electrochemical studies show that the nickel complex exhibited a quasi-reversible one-electron reduction process, while copper and cobalt complexes gave irreversible reduction processes in DMSO solution. 相似文献
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Matthew Thompson Carolyn Carkner Adrian Bailey Nicholas J. Mosey Nadia Kapernaum 《Liquid crystals》2013,40(9):1246-1260
Two sterically equivalent series of phenoxy-terminated 5-alkoxy-2-(4-alkoxyphenyl)pyrimidine liquid crystals were synthesised, and their mesogenic properties were characterised by polarised optical microscopy and differential scanning calorimetry (DSC). The phenoxy end-group causes a significant increase in melting point and inhibits – at least partially – the mesomorphism of these materials relative to the parent isomers; in most cases, the broad enantiotropic SmC phase formed by the parent isomers is suppressed by the addition of the phenoxy end-group. However, detailed analyses by small-angle X-ray scattering and monodomain 2D X-ray scattering suggest that these compounds form a SmA phase with a partially intercalated bilayer structure in which the phenoxy end-groups are nanosegregated. Such an intercalated bilayer structure might enable the tuning of smectogenic properties by appropriate substitution of the phenoxy end-groups. 相似文献
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Sen‐Wang Zhang Ling‐Pan Lu Bai‐Xiang Li Yue‐Sheng Li 《Journal of polymer science. Part A, Polymer chemistry》2012,50(22):4721-4731
Vanadium(III) complexes bearing phenoxy‐phosphine ligands ( 2a–g ) (2‐R1‐4‐R2‐6‐PPh2‐C6H2O)VCl2(THF)2 ( 2a : R1 = R2 = H; 2b : R1 = F, R2 = H; 2c : R1 = Ph, R2 = H; 2d : R1 = tBu, R2 = H; 2e : R1 = R2 = Me; 2f : R1 = R2 = tBu; 2g : R1 = R2 = CMe2Ph) were prepared from VCl3(THF)3 by treating with 1.0 equiv of the ligand in tetrahydrofuran (THF) in the presence of excess triethylamine (TEA). The reaction of VCl3(THF)3 with 2.0 equiv of the ligand in THF in the presence of excess TEA afforded vanadium(III) complexes bearing two phenoxy‐phosphine ligands ( 3c–f ). These complexes were characterized by FTIR and mass spectrum as well as elemental analyses. Structures of 2f and 3c were further confirmed by X‐ray crystallographic analyses. Complexes 2a–g and 3c–f were employed as the catalysts for ethylene polymerization under various reaction conditions. On activation with Et2AlCl, these complexes exhibited high catalytic activities (up to 41.3 kg PE/mmolV·h·bar) even at high temperature (70°C), and produced high molecular weight polymer with unimodal molecular weight distributions, indicating the polymerization took place in a single‐site nature. Complexes 3c–f displayed better thermal stability than the corresponding complexes 2a–g under similar conditions. In addition, copolymerizations of ethylene and 1‐hexene with precatalysts 2a–g were also explored in the presence of Et2AlCl. Catalytic activity, comonomer incorporation, and properties of the resultant polymers can be controlled over a wide range by tuning catalyst structures and reaction parameters.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
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Polycaprolactone (PCL) based α,ω-methacrylated macromonomer (DMPCL) was synthesized via enzymatic ring-opening polymerization (eROP) by using Novozyme 435 as the enzyme immobilized catalyst. DMPCL was further photopolymerized with monofunctional poly(ethylene glycol) methyl ether methacrylate (PEGMA-950) macromonomer and trimethylolpropane triacrylate (TMPTA) as tri-functionalized crosslinking agent in glass vials when CHCl3 was the solvent and Irgacure 819 was the photoinitiator. Ultraviolet (UV) Light Emitting Diode (LED) bulbs enabled photoinduced reactions at room temperature with low heat generation and high reaction efficiency. The obtained gels were characterized with Fourier Transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC). DMPCL participated as an effective crosslinking agent in the photopolymerization of PEGMA-950. Combined usage of DMPCL and PEGMA-950 resulted in significantly more effective polymerization than the separate photopolymerizations of these macromonomers. 相似文献
8.
Butylated hydroxytoluene enediyne: access to diradical and electrophilic quinone methide intermediates
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Edyta M. Greer Cesar S. Quezada Christopher V. Cosgriff 《Journal of Physical Organic Chemistry》2015,28(5):365-369
A theoretical study was carried out on the unimolecular reaction of an enediyne with a fused butylated hydroxytoluene to internally scavenge the p‐benzyne diradical sites formed after the Bergman cyclization. The calculations revealed that the conversion of the p‐benzyne diradical (2‐tert‐butyl‐4‐methyl‐5,8‐didehydro‐1‐naphthalenol) to p‐quinone methide is favored over the conversion to a phenoxy/benzene diradical 4 in an approximate 95:5 ratio. Based on this model, the Bergman cyclization leads in a bifunctional manner to intermediates for competing reactivity with intermolecular H‐atom abstraction. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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