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The predictions for density-density-type response functions of a quasi-one dimensional electron gas are compared in detail for various models (Hubbard and Tomonaga model) and for various approximations (Monte-Carlo calculations, RPA and extended RPA). It is shown that RPA does not lead to intrinsic contradictions for electron densities larger than 1.5 inverse exciton Bohr radii. Even in this high-density regime local field corrections enhance spin- and density susceptibilities significantly. 相似文献
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Synthesis, Properties, and Crystal Structure of Cl3(bpy)Ta≡NOCH3, a Methoxynitrene Complex of Tantalum TaCl5 reacts in the presence of 2,2′-bipyridine with O-methyl-hydroxylamine or bis(trimethylsilyl)-O-methyl-hydroxylamine to yield the methoxynitrene complex Cl3(bpy)Ta≡NOCH3. The red complex decomposes only slowly at moist air. It crystallizes in the monoclinic space group C2/c with the lattice constants a = 1588.5, b = 1515.9, c = 1414.2 pm, β = 122.78°, Z = 8. The monomeric complex exhibits a distorted octahedral coordination for the tantalum atom. The methoxynitrene ligand is coordinated by a Ta? N triple bond resulting in a linear Ta≡N? O arrangement with Ta? N? O = 174.0° and distances Ta? N = 174.4 pm and N? O = 134.8 pm. v(Ta? N) is observed in the i.r. spectrum at 950 cm?1. 相似文献
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Umland KD Palisse A Haug TT Kirsch SF 《Angewandte Chemie (International ed. in English)》2011,50(42):9965-9968
Two cats, two paths: Two novel domino reactions starting from 6-hydroxy-2-alkyl-2-alkynylcyclohexanones have been discovered. While redox-neutral platinum catalysis gives rise to furans through a sequence of cyclization, 1,2-shift, and Grob fragmentation, oxidative copper catalysis provides an entry to bicyclic 2,3-dihydrofurans. Upon cyclization and oxidation, an unusual benzilic acid rearrangement can take place in this case. 相似文献
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Vu T. Nguyen Viet D. Nguyen Graham C. Haug Ngan T. H. Vuong Hang T. Dang Hadi D. Arman Oleg V. Larionov 《Angewandte Chemie (International ed. in English)》2020,59(20):7921-7927
The development of efficient and selective C?N bond‐forming reactions from abundant feedstock chemicals remains a central theme in organic chemistry owing to the key roles of amines in synthesis, drug discovery, and materials science. Herein, we present a dual catalytic system for the N‐alkylation of diverse aromatic carbocyclic and heterocyclic amines directly with carboxylic acids, by‐passing their preactivation as redox‐active esters. The reaction, which is enabled by visible‐light‐driven, acridine‐catalyzed decarboxylation, provides access to N‐alkylated secondary and tertiary anilines and N‐heterocycles. Additional examples, including double alkylation, the installation of metabolically robust deuterated methyl groups, and tandem ring formation, further demonstrate the potential of the direct decarboxylative alkylation (DDA) reaction. 相似文献
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Vu T. Nguyen Graham C. Haug Viet D. Nguyen Ngan T. H. Vuong Hadi D. Arman Oleg V. Larionov 《Chemical science》2021,12(18):6429
Sulfonamides feature prominently in organic synthesis, materials science and medicinal chemistry, where they play important roles as bioisosteric replacements of carboxylic acids and other carbonyls. Yet, a general synthetic platform for the direct conversion of carboxylic acids to a range of functionalized sulfonamides has remained elusive. Herein, we present a visible light-induced, dual catalytic platform that for the first time allows for a one-step access to sulfonamides and sulfonyl azides directly from carboxylic acids. The broad scope of the direct decarboxylative amidosulfonation (DDAS) platform is enabled by the efficient direct conversion of carboxylic acids to sulfinic acids that is catalyzed by acridine photocatalysts and interfaced with copper-catalyzed sulfur–nitrogen bond-forming cross-couplings with both electrophilic and nucleophilic reagents.Sulfonamides are now accessible directly from carboxylic acids by a one-step, tricomponent decarboxylative amidosulfonation that provides the missing link between the two key functionalities. 相似文献