Topic
Hydrogen atom abstraction
About: Hydrogen atom abstraction is a research topic. Over the lifetime, 7059 publications have been published within this topic receiving 151781 citations.
Papers published on a yearly basis
Papers
More filters
TL;DR: The utility of the transformation is demonstrated in the late-stage site-selective functionalization of natural products and pharmaceuticals, allowing rapid derivatization for investigation of structure-activity relationships.
Abstract: We report a simple one-pot protocol that affords functionalization of N-CH3 groups in N-methyl-N,N-dialkylamines with high selectivity over N-CH2R or N-CHR2 groups. The radical cation DABCO+•, prepared in situ by oxidation of DABCO with a triarylaminium salt, effects highly selective and contra-thermodynamic C–H abstraction from N-CH3 groups. The intermediates that result react in situ with organometallic nucleophiles in a single pot, affording novel and highly selective homologation of N-CH3 groups. Chemoselectivity, scalability, and recyclability of reagents are demonstrated, and a mechanistic proposal is corroborated by computational and experimental results. The utility of the transformation is demonstrated in the late-stage site-selective functionalization of natural products and pharmaceuticals, allowing rapid derivatization for investigation of structure–activity relationships.
72 citations
TL;DR: A density functional theory (DFT) study on the free radical and OOH(•) scavenging properties of some mono- and polysaccharides is presented and it is suggested that the carbohydrates are not able to directly scavenge O OH(•).
Abstract: A density functional theory (DFT) study on the free radical (OH• and OOH•) scavenging properties of some mono- and polysaccharides is presented. Two mechanisms, single electron transfer (SET) and hydrogen atom transfer (HAT), are considered. The former mechanism is studied by making use of the vertical ionization energy and vertical electron affinity of the radicals and carbohydrates. It is confirmed that the SET mechanism is not plausible to occur. With respect to the HAT, not only does the OH• radical react preferably with one hydrogen atom bonded to one carbon atom, but also the reaction with a hydrogen atom bonded to an oxygen is possible. Finally, it is suggested that the carbohydrates are not able to directly scavenge OOH•.
72 citations
TL;DR: In this article, a transfert d'hydrogene sigmatrope-1,4 dans un hexahydrocarbazole is described, as well as an enlevement of hydrogene par des radicaux libres dans le dimethylglyoxime cristallise.
Abstract: Application: 1) a l'isomerisation du tri-t-butyl-2,4,6 phenyle en di-t-butyl-3,5 neophyle, 2) a la tautomerie cetoenolique de la methyl-2' acetophenone, 3) au transfert d'hydrogene sigmatrope-1,4 dans un hexahydrocarbazole, 4) a l'enlevement d'hydrogene par des radicaux libres dans le dimethylglyoxime cristallise et 5) au transfert d'hydrogene du dihydrophenanthrene a l'oxygene
72 citations
TL;DR: It is found that the efficiency of these compounds as enhancers of lipid peroxidation increases with increasing electron density, suggesting that, at least in the model system, the oxidation of the substrates is the limiting step in causing lipidperoxidation.
Abstract: The peroxidation of liposomes by a haem peroxidase and hydrogen peroxide in the presence of indole-3-acetic acid and derivatives was investigated. It was found that these compounds can accelerate the lipid peroxidation up to 65 fold and this is attributed to the formation of peroxyl radicals that may react with the lipids, possibly by hydrogen abstraction. The peroxyl radicals are formed by peroxidase-catalyzed oxidation of the enhancers to radical cations which undergo cleavage of the carbon-carbon bond on the side-chain to yield CO2 and carbon-centred radicals that rapidly add oxygen. In competition with decarboxylation, the radical cations deprotonate reversibly from the Nl position. Rates of decarboxylation,pKa values and rate of reaction with the peroxidase compound I indicate consistent substituent effects which, however, can not be quantitatively related to the usual Hammett or Brown parameters. Assuming that the rate of decarboxylation of the radical cations taken is a measure of the electron dens...
72 citations
TL;DR: The kinetics of the hydrogen abstraction reactions of hydrogen atom with n-propyl radical and isopropyl radical were studied using the direct ab initio dynamics approach to optimize the geometries of stationary points as well as the points on the minimum energy path (MEP).
Abstract: The kinetics of the hydrogen abstraction reactions of hydrogen atom with n-propyl radical and isopropyl radical were studied using the direct ab initio dynamics approach. BHandHLYP/cc-pVDZ method was employed to optimize the geometries of stationary points as well as the points on the minimum energy path (MEP). The energies of all the points for the two reactions were further refined at the QCISD(T)/cc-pVTZ level of theory. No barrier was found at the QCISD(T)/cc-pVTZ//BHandHLYP/cc-pVDZ level of theory for both reactions. The forward and reverse rate constants were evaluated with both canonical variational transition state theory (CVT) and microcanonical variational transition state theory (μ VT) in the temperature range of 300–2,500 K. The fitted three-parameter Arrhenius expression of the calculated CVT rate constants at the QCISD(T)/cc-pVTZ//BHandHLYP/cc-pVDZ level of theory are kCVT (n – C3H7)=1.68×10−14 T0.84 e(319.5/T) cm3 molecule−1 s−1 and kCVT (iso-C3H7)=4.99×10−14 T0.90 e(159.5/T) cm3 molecule−1 s−1 for reactions of n-C3H7 + H and iso-C3H7 + H, respectively, which are in good agreement with available literature data. The variational effects were analysed. Figure Comparison of the calculated forward rate constants at the QCISD(T)/cc-pVTZ//BHandHLYP/cc-pVDZ level of theory and the available experimental and theoretical data of the reaction vs 1,000/T for the two reactions.
72 citations