2226-96-2Relevant academic research and scientific papers
Photoinduced oxidation of sterically hindered amines in acetonitrile solutions and titania suspensions (An EPR Study)
Barbierikova, Zuzana,Mihalikova, Maria,Brezova, Vlasta
, p. 1442 - 1454 (2012)
The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO2 suspensions upon exposure to monochromatic radiation, λ = 365 nm, by means of in situ EPR spectroscopy. The formation of singlet oxygen, as one of the possible oxidation agents for SHA, in these systems is affected significantly by solvent used and the experimental conditions. Experiments in homogeneous media evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species involved. In anhydrous acetonitrile solutions containing KO2, the SHA oxidation was negligible not only in the dark but also on continuous exposure. However, the presence of water, even at low concentrations, led to the transformation of O2?- to singlet oxygen and hydrogen peroxide, which served as a source of hydroxyl radicals. These species participated in oxidation of SHA resulting in the generation of nitroxide radicals. To investigate the influence of different competitive reactions of SHA with other ROS formed upon TiO2 photoexcitation, a series of experiments using different additives (e.g. KO2, H2O 2, NaN3, dimethylsulfoxide, methanol as organic cosolvents) under air or argon were performed. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using EPR spin trapping technique. The reactions of sterically hindered amines (SHA) were investigated in acetonitrile solutions and TiO 2 suspensions upon exposure to monochromatic radiation (λ = 365 nm) by in situ EPR spectroscopy. Experiments in homogeneous media using KO2 and H2O2 evidenced alternative pathways for the SHA oxidation with a variety reactive oxygen species (ROS) involved. The influence of competitive reactions of SHA with ROS formed upon TiO2 photoexcitation was investigated in a series of experiments using different additives (e.g. KO2, H2O2, NaN3, dimethylsulfoxide and methanol) under air or argon. The detailed analysis of paramagnetic intermediates formed upon the irradiation of the studied systems was accomplished using an EPR spin trapping technique. 2012 Wiley Periodicals, Inc. Photochemistry and Photobiology
EPR Study of Membrane Partitioning, Orientation, and Membrane-Modulated Alkaline Hydrolysis of a Spin-Labeled Benzoic Acid Ester
Bianconi, M. Lucia,Schreier, Shirley
, p. 2483 - 2486 (1991)
The composite EPR spectra of a spin probe (Tempobenzoate, TB) that partitions between aqueous and egg phosphatidylcholine (EPC) membrane phases provide information about (1) its location and orientation in the membrane, (2) its partition coefficient and the thermodynamics of the process, and (3) the kinetics of its alkaline hydrolysis, a novel application of spin label spectra.The broad and narrow spectral components of the probe in the membrane and aqueous phase, respectively, are sufficiently resolved in the high-field region, to permit quantitative evaluation of the narrow line (h).The line shapes of membrane spectra, obtained by spectral subtraction, indicate that the nitroxide x axis (the probe long molecular axis) is aligned preferentially parallel to the bilayer normal.Spectral subtractions, as well as measurement of h, are used to calculate the probe's partition coefficient.Thermodynamic analysis indicated that binding of the probe is endothermic and driven by an increase in entropy suggesting that dehydration is the predominant step.At alkaline pH, TB undergoes hydrolysis.Although the narrow high-field lines of both reactant (TB) and product (Tempol) overlap, the pseudo-first-order rate constants can be calculated from the time-dependent height of this line.At high ionic strength, the reaction occurs essentially in the aqueous phase, and the decrease in rate with increasing membrane concentration is due to partition modulation of reagent concentration.TB-membrane binding was also evaluated from the kinetic data.The results are in excellent agreement with those obtained by direct measurements.
Reactions of nitroxides. Part XII [1]. - 2,2,6,6-tetramethyl-l-oxyl-4- piperidyl chloroformate - A new reactive nitroxyl radical. a one-pot synthesis of 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl N,N-dialkyl-carbamates
Zakrzewski, Jerzy,Krawczyk, Maria
, p. 493 - 498 (2011)
The reactive nitroxides 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl chloroformate and 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl chlorothionoformate were synthesized from 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl and diphosgene (68percent) or thiophosgene (61 percent), respectively. The reactions of the chloroformate and chlorothionoformate with lower secondary amines lead to 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl A,A-dialkylcarbamates (59-94percent) and thionocarbamates (35-65 percent), respectively. Unexpectedly, the same 2,2,6,6-tetramethyl-1-oxyl-4-piperidyl A,A-dialkylcarbamates were obtained directly in a one-pot reaction of 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl with diphosgene and lower tertiary alkylamines by dealkylation in 32-86 percent yield. The antifungal activity of the synthesized carbamates and thionocarbamates has been demonstrated.
Light-Sensitive Alkoxyamines as Versatile Spatially- and Temporally- Controlled Precursors of Alkyl Radicals and Nitroxides
Baron, Marc,Morris, Jason C.,Telitel, Siham,Clément, Jean-Louis,Lalevée, Jacques,Morlet-Savary, Fabrice,Spangenberg, Arnaud,Malval, Jean-Pierre,Soppera, Olivier,Gigmes, Didier,Guillaneuf, Yohann
, p. 3339 - 3344 (2018)
The use of UV/visible light irradiation as a means to initiate organic syntheses is increasingly attractive due to the high spatial and temporal control conferred by photochemical processes. The aim of this work is thus to demonstrate that alkoxyamines be
Synthesis of novel spin-labeled derivatives of 5-FU as potential antineoplastic agents
Yang, Liu,Wang, Mei-Juan,Zhang, Zhi-Jun,Morris-Natschke, Susan L.,Goto, Masuo,Tian, Jing,Liu, Ying-Qian,Wang, Chih-Ya,Tian, Xuan,Yang, Xiao-Ming,Lee, Kuo-Hsiung
, p. 3269 - 3273 (2014)
Chemotherapy is a general treatment option for various cancers, including lung cancer. In order to find compounds with superior bioactivity and less toxicity against lung cancer, novel spin-labeled 5-fluorouracil (5-FU) derivatives (3a-f) were synthesized and evaluated against four human tumor cell lines (A-549, DU-145, KB, and KBvin). Two promising compounds 3d and 3f exhibited IC50 values of 2.76 and 2.38 μM, respectively, against non-small cell lung carcinoma cell line A-549. These compounds were twofold more cytotoxic than 5-FU and less toxic against other tested cell lines. Compound 3f exhibited seven times more selective cytotoxicity against A-549 than 5-FU. Our results suggest that compounds 3d and 3f merit further investigation for development into clinical trial candidates for non-small cell lung cancer.
Chemistry and anti-herpes simplex virus type 1 evaluation of 4-substituted-1H-1,2,3-triazole-nitroxyl-linked hybrids
Cunha, Anna C.,Ferreira, Vitor F.,Vaz, Maria G. F.,Cassaro, Rafael A. All?o,Resende, Jackson A. L. C.,Sacramento, Carolina Q.,Costa, Jéssica,Abrantes, Juliana L.,Souza, Thiago Moreno L.,Jord?o, Alessandro K.
, p. 2035 - 2043 (2021)
Abstract: HSV disease is distributed worldwide. Anti-herpesvirus drugs are a problem in clinical settings, particularly in immunocompromised individuals undergoing herpes simplex virus type 1 infection. In this work, 4-substituted-1,2,3-1H-1,2,3-triazole linked nitroxyl radical derived from TEMPOL were synthesized, and their ability to inhibit the in vitro replication of HSV-1 was evaluated. The nitroxide derivatives were characterized by infrared spectroscopy and elemental analysis, and three of them had their crystal structures determined by single-crystal X-ray diffraction. Four hybrid molecules showed important anti-HSV-1 activity with IC50 values ranged from 0.80 to 1.32?μM. In particular, one of the nitroxide derivatives was more active than Acyclovir (IC50 = 0.99?μM). All compounds tested were more selective inhibitors than the reference antiviral drug. Among them, two compounds were 4.5 (IC50 0.80?μM; selectivity index CC50/IC50 3886) and 7.7 times (IC50 1.10?μM; selectivity index CC50/IC50 6698) more selective than acyclovir (IC50 0.99?μM; selectivity index CC50/IC50: 869). These nitroxide derivatives may be elected as leading compounds due to their antiherpetic activities and good selectivity. Graphic abstract: [Figure not available: see fulltext.]
Ultrafast and reversible multiblock formation by the SET-nitroxide radical coupling reaction
Kulis, Jakov,Bell, Craig A.,Micallef, Aaron S.,Monteiro, Michael J.
, p. 1227 - 1236 (2010)
The single electron transfer-nitroxide radical coupling (SET-NRC) reaction has been used to produce multiblock polymers with high molecular weights in under 3 min at 50°C by coupling a difunctional telechelic polystyrene (Br-PSTY-Br) with a dinitroxide. The well known combination of dimethyl sulfoxide as solvent and Me6TREN as ligand facilitated the in situ disproportionation of CuIBr to the highly active nascent Cu 0 species. This SET reaction allowed polymeric radicals to be rapidly formed from their corresponding halide end-groups. Trapping of these carbon-centred radicals at close to diffusion controlled rates by dinitroxides resulted in high-molecular-weight multiblock polymers. Our results showed that the disproportionation of CuI was critical in obtaining these ultrafast reactions, and confirmed that activation was primarily through Cu 0. We took advantage of the reversibility of the NRC reaction at elevated temperatures to decouple the multiblock back to the original PSTY building block through capping the chain-ends with mono-functional nitroxides. These alkoxyamine end-groups were further exchanged with an alkyne mono-functional nitroxide (TEMPO-≡) and 'clicked' by a Cu I-catalyzed azide/alkyne cycloaddition (CuAAC) reaction with N 3-PSTY-N3 to reform the multiblocks. This final 'click' reaction, even after the consecutive decoupling and nitroxide-exchange reactions, still produced high-molecular-weight multiblocks efficiently. These SET-NRC reactions would have ideal applications in re-usable plastics and possibly as self-healing materials. CSIRO 2010.
Kinetics of oxidation and comproportionation reactions involving an oxammonium ion, benzyl alcohol and methyltrioxorhenium(VII)
Zauche, Timothy H.,Espenson, James H.
, p. 381 - 385 (1999)
The reactions of 4-hydroxy-2,2,6,6-tetramethylpiperidinium N-oxide, an oxammonium ion abbreviated R2NO+, have been studied. The previously unreported triflate salt was used in this study because the anions of the usual chloride and bromide salts can themselves be oxidized. Reactions between R2NO+ and alcohols produce ketones and aldehydes; the rate constant for PhCH2OH is 4.4×10-3 L mol-1 s-1 in acetonitrile at 298 K. The immediate product is the hydroxylamine, R2NOH, but its further comproportionation reaction with R2NO+ yields the stable piperidinyl oxyl radical, R2NO·. The rate constant of this reaction is 1.78×103 L mol-1 s-1 at 298 K. The possibility of using R2NO+ and MTO as co-catalysts for the oxidation of alcohols was explored, but the competitive rates are such that the resultant is not particularly attractive.
Method for preparing hindered amine nitroxide free radical compound by alkaline heterogeneous catalysis system
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Paragraph 0042-0045; 0058-0059, (2021/09/26)
The method comprises the following steps: dissolving a hindered amine compound in an organic solvent; adjusting pH by a carbonate aqueous solution; reacting with an aqueous hydrogen peroxide solution; and generating a hindered amine nitroxide free radical compound (IV). (V) Or (VI). The method is high in universality, and the hindered amine nitroxide free radical compound with various structures is prepared. The method is high in catalytic activity, short in reaction time, high in yield, simple in preparation process and convenient to operate; a high-purity target product can be obtained through simple phase separation, drying and concentration in the post-treatment process; meanwhile, the aqueous solution system and ethyl acetate can be recycled. Small by-products.
A cyanine dye based supramolecular photosensitizer enabling visible-light-driven organic reaction in water
Fujitsuka, Mamoru,Kida, Toshiyuki,Mori, Tadashi,Ohkubo, Kei,Osakada, Yasuko,Shigemitsu, Hajime,Tamemoto, Tomoe
supporting information, p. 11217 - 11220 (2021/11/09)
We report the aggregation-induced photosensitizing activity of a cyanine dye in water and the mechanism. In addition, using the supramolecular assembly, visible-light-driven photooxidation of hydrophobic aromatic compounds in water was successfully performed. This journal is
