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1.
A variety of allylic, benzylic, primary, and secondary saturated alcohols have been converted into the corresponding iodides using NaI supported on KSF clay. Selective conversion of allylic and benzylic alcohols in the presence of primary and secondary saturated alcohols has also been demonstrated. 相似文献
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Wen J Chowdhury P Fulton DB Datta A Das K Andreotti AH Petrich JW 《Photochemistry and photobiology》2003,77(1):5-9
Nuclear magnetic resonance measurements indicate that hypericin exists in the same "normal" tautomeric form irrespective of whether the solvent is dimethyl sulfoxide or tetrahydrofuran. This result is discussed in the context of previous experimental and theoretical work. It is concluded that solvent perturbations cannot induce tautomerization in hypericin. 相似文献
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Emanuel Makrlík Ji?í Dybal Ji?ina ?vor?íková Jan Budka Petr Vaňura 《Monatshefte für Chemie / Chemical Monthly》2010,287(1):507-510
Abstract
From extraction experiments in the two-phase water/nitrobenzene system, the stability constant of the silver ionophore IV (i.e., 5,11,17,23-tetra-tert-butyl-25,27-bis[2-(methylthio)ethoxy]calix[4]arene)–Ag+ complex in nitrobenzene saturated with water was determined. Furthermore, the most probable structure of the resulting complex was derived by means of density functional level of theory calculations. 相似文献5.
IntroductionAggregationisacommonphenomenonformanysim pleorganicmoleculesaswellascomplexmoleculeswithimportantbiologicalactivity .Formationofaggregatesmaybedrivenbydifferentnon covalentinteractions ,suchashydrogenbonding ,1electrostaticinteraction ,2 orhy dr… 相似文献
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Dr. A. Carel N. Kwamen Judith Jenniches Prof. Dr. Iris M. Oppel Prof. Dr. Markus Albrecht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(46):10550-10554
Hierarchical helicates based on ketone-substituted titanium(IV)triscatecholates show different monomer-dimer behavior depending on different solvents. The dimerization constants of a whole series of differently alkyl-substituted complexes is analyzed to show that the solvent has a very strong influence on the dimerization. Hereby, effects like solvophobicity/philicity, sterics, electronics of the substituents and weak side-chain—side-chain interactions seem to act in concert. 相似文献
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Dr. Dimitri Komiotis George Agelis Stella Manta Niki Tzioumaki Evangelia Tsoukala Kostas Antonakis 《Journal of carbohydrate chemistry》2013,32(6):441-450
A convenient method has been developed for a facile and high‐yield conversion of 6‐O‐tert‐butyldimethylsilyl and 6‐O‐trityl protected monosaccharides to their formate esters, which may serve as useful intermediates for the replacement of the primary hydroxyl group of sugars by other functional groups. 相似文献
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Brennan Ashwood Marvin Pollum Prof. Dr. Carlos E. Crespo‐Hernández 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16648-16656
In 2014, two unnatural nucleosides, d5SICS and dNaM, were shown to selectively base pair and replicate with high fidelity in a modified strain of E. coli, thus effectively expanding its genetic alphabet from four to six letters. More recently, a significant reduction in cell proliferation was reported in cells cultured with d5SICS, and putatively with dNaM, upon exposure to brief periods of near‐visible radiation. The photosensitizing properties of the lowest‐energy excited triplet state of both d5SICS and dNaM were implicated in their cytotoxicity. Importantly, however, the excited‐state mechanisms by which near‐visible excitation populates the triplet states of d5SICS and dNaM are currently unknown. In this study, steady‐state and time‐resolved spectroscopies are combined with quantum‐chemical calculations in order to reveal the excited‐state relaxation mechanisms leading to efficient population of the triplet states in these unnatural nucleosides in solution. It is shown that excitation of d5SICS or dNaM with near‐visible light leads overwhelmingly to ultrafast population of their triplet states on the femtosecond time scale. The results presented in this work lend strong support to the proposal that photoexcitation of these unnatural nucleosides can accelerate oxidatively generated damage to DNA and other biomolecules within the cellular environment. 相似文献
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A simple two-step, one-pot procedure based on the treatment of sodium 2-naphthoxide with bromine yields 1,1′-binaphthalene-2,2′-diol in a high yield and an excellent purity. The procedure is applicable also to preparation of the symmetrically disubstituted analogues. 相似文献
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Victor Akpe Abimbola Ogunsipe Christian Madu Hjalmar Brismar 《Journal of solution chemistry》2015,44(2):307-326
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The effect of random reshuffling of amino acids on the properties of dimers formed by Aβ peptides is studied using replica exchange molecular dynamics and united atom implicit solvent model. We show that thermodynamics of dimer assembly and the dimer globule-like state are not affected by sequence permutation. Furthermore, sequence reshuffling does not change the distributions of non-local interactions and, to a large extent, amino acids in the dimer volume. To rationalize these results, we demonstrate that Gaussian statistics applies surprisingly well to the end-to-end distances of the peptides in the dimer implying that non-bonded interactions between distant along the chain amino acids are effectively screened. This observation suggests that peptides in the dimer behave as ideal chains in polymer melt, in which amino acids lose their "identity" and therefore the memory of sequence position. As a result large-scale properties of the dimer become universal or sequence independent. Comparison of our simulations with the prior theoretical studies and their implications for experiments are discussed. 相似文献
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The stereoselective synthesis of Z-β-siloxyacrylonitriles via base-induced ring cleavage of isoxazole precursors is described. Z-β-siloxyacrylonitriles react with organolithium compounds to give high yields of β-enaminoketones 1. 相似文献
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Davide Spinnato Dr. Bertrand Schweitzer-Chaput Dr. Giulio Goti Dr. Maksim Ošeka Prof. Dr. Paolo Melchiorre 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(24):9572-9577
Reported herein is a visible-light-mediated radical approach to the α-alkylation of ketones. This method exploits the ability of a nucleophilic organocatalyst to generate radicals upon SN2-based activation of alkyl halides and blue light irradiation. The resulting open-shell intermediates are then intercepted by weakly nucleophilic silyl enol ethers, which would be unable to directly attack the alkyl halides through a traditional two-electron path. The mild reaction conditions allowed functionalization of the α position of ketones with functional groups that are not compatible with classical anionic strategies. In addition, the redox-neutral nature of this process makes it compatible with a cinchona-based primary amine catalyst, which was used to develop a rare example of enantioselective organocatalytic radical α-alkylation of ketones. 相似文献
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Usama Karama 《合成通讯》2013,43(23):3447-3451
(Carboethoxymethylene)triphenylphosphorane 1 can undergo the tandem reaction of iodination–oxidation–Wittig reaction with alcohol in the presence of N-iodosuccinimide (NIS) and manganese dioxide. The reaction constitutes a stereoselective one-pot procedure for the preparation of Z-configured α-iodo-α,β-unsaturated esters in good to excellent yield. 相似文献
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Although the insertion of alkynes into transition‐metal−carbon bonds plays an important role in synthesis, the regioselectivities observed with unsymmetric alkynes have usually been interpreted on the basis of steric effects. In this perspective paper, we review the available data for such reactions with nickelacycles and present the results of some preliminary theoretical (DFT) calculations. These suggest that, even for unactivated alkynes, the regiochemistry may also be controlled by electronic factors such as frontier‐orbital interactions between the triple‐bond of the alkyne and the polarized metal−carbon bond. 相似文献
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A. V. Chistyakov P. A. Zharova A. E. Gekhman V. V. Kriventsov M. V. Tsodikov 《Kinetics and Catalysis》2016,57(6):812-820
It was found that the preliminarily reduced commercial platinum–rhenium catalyst PR-71 exhibited high activity in the conversion of ethanol into C4–C12 olefins and in the cross-condensation reactions of ethanol with glycerol, acetone, n-propanol, and isopropanol. Acetone and glycerol exhibited the highest reactivity in the cross-condensation reactions; this manifested itself in an increase in the total yield of the target fraction of C4–C12 hydrocarbons and in a more than 10-fold increase in the yield of products containing the odd numbers of carbon atoms, as compared with the conversion of individual ethanol. The structural studies performed by extended X-ray absorption fine structure (EXAFS) spectroscopy and transmission electron microscopy showed that the high selectivity of PR-71 can be caused by the formation of bimetallic Pt–Re and Pt–Al clusters in the course of the prolonged preliminary reduction of the catalyst. 相似文献
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Dr. Jean‐Pierre Costes Dr. Carine Duhayon Dr. Sonia Mallet‐Ladeira Prof. Sergiu Shova Dr. Laure Vendier 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):2171-2180
Several theoretical investigations with CASSCF methods confirm that the magnetic behavior of Cu–Gd complexes can only be reproduced if the 5d Gd orbitals are included in the active space. These orbitals, expected to be unoccupied, do present a low spin density, which is mainly due to a spin polarization effect. This theory is strengthened by the experimental results reported herein. We demonstrate that Cu–Gd complexes characterized by Cu–Gd interactions through single‐oxygen and three‐atom bridges consisting of oxygen, carbon, and nitrogen atoms, present weak ferromagnetic exchange interactions, whereas complexes with bridges made of two atoms, such as the nitrogen–oxygen oximato bridge, are subject to weak antiferromagnetic exchange interactions. Therefore, a bridge with an odd number of atoms induces a weak ferromagnetic exchange interaction, whereas a bridge with an even number of atoms supports a weak antiferromagnetic exchange interaction, as observed in pure organic compounds and also, as in this case, in metal–organic compounds with an active spin polarization effect. 相似文献