2226-96-2Relevant articles and documents
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
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.
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.
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Weiner
, p. 526,527 (1969)
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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.
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.
Synthesis and evaluation of β-galactosidase-targeting spin-label probe: 5-o-β-d-galactosyl-5-hydroxy-1,1,3,3-tetramethylisoindoline-2-oxyl
Ito, Tomohiro,Konno, Hiroyuki,Sato, Shingo,Sugawara, Koya
, p. 1799 - 1815 (2020/11/19)
In this study, 3-hydroxymethyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl, and 5-hydroxy-1,1,3,3-tetra-methylisoindoline-2-oxyl O-galactosides (PG, TG, and IG) were synthesized. Moreover, their reduction reactivi
