578-57-4Relevant articles and documents
Chain-Breaking Phenolic 2,3-Dihydrobenzo[b]selenophene Antioxidants: Proximity Effects and Regeneration Studies
Singh, Vijay P.,Yan, Jiajie,Poon, Jia-Fei,Gates, Paul J.,Butcher, Ray J.,Engman, Lars
, p. 15080 - 15088 (2017)
Phenolic 2,3-dihydrobenzo[b]selenophene antioxidants bearing an OH-group ortho (9), meta (10, 11) and para (8) to the Se were prepared by seleno-Claisen rearrangement/intramolecular hydroselenation. meta-Isomer (11) was studied by X-ray crystallography. The radical-trapping activity and regenerability of compounds 8–11 were evaluated using a two-phase system in which linoleic acid was undergoing peroxidation in the lipid phase while regeneration of the antioxidant by co-antioxidants (N-acetylcysteine, glutathione, dithiothreitol, ascorbic acid, tris(carboxyethyl)phosphine hydrochloride) was ongoing in the aqueous layer. Compound 9 quenched peroxyl radicals more efficiently than α-tocopherol. It also provided the most long-lasting antioxidant protection. With thiol co-antioxidants it could inhibit peroxidation for more than five-fold longer than the natural product. Regeneration was more efficient when the aqueous phase pH was slightly acidic. Since calculated O?H bond dissociation energies for 8–11 were substantially larger than for α-tocopherol, an antioxidant mechanism involving O-atom transfer from peroxyl to selenium was proposed. The resulting phenolic selenoxide/alkoxyl radical would then exchange a hydrogen atom in a solvent cage before antioxidant regeneration at the aqueous lipid interphase.
Chiral secondary phosphine oxide pre-ligand and application thereof
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Paragraph 0033-0036, (2021/10/20)
The invention discloses a chiral secondary phosphine oxide pre-ligand and application thereof. The structure of the ligand is as shown in Formula I, where R. 1 . R2 , R3 And R4 Hydrogen, benzyl, substituted alkyl, substituted or unsubstituted aryl. The more preferred structural formula comprises 4 structural general formulas shown in the general formula I in the following formula: I-d, and the formula is shown in the general formula. Based on the designed asymmetric catalytic reaction system, the stability and the easy preparation of the comprehensive test ligand under the hydrocarbon activation condition are synthesized, and finally the chiral secondary oxidation phosphorus precursor with the double functional groups in the oxidation and heating environment is selected. The catalyst formed by the front ligand and the active metal compound has high activity and high selectivity in the reaction of constructing a chiral center, and has the stability.
Orthogonal Stability and Reactivity of Aryl Germanes Enables Rapid and Selective (Multi)Halogenations
Deckers, Kristina,Fricke, Christoph,Schoenebeck, Franziska
supporting information, p. 18717 - 18722 (2020/08/25)
While halogenation is of key importance in synthesis and radioimaging, the currently available repertoire is largely designed to introduce a single halogen per molecule. This report makes the selective introduction of several different halogens accessible. Showcased here is the privileged stability of nontoxic aryl germanes under harsh fluorination conditions (that allow selective fluorination in their presence), while displaying superior reactivity and functional-group tolerance in electrophilic iodinations and brominations, outcompeting silanes or boronic esters under rapid and additive-free conditions. Mechanistic experiments and computational studies suggest a concerted electrophilic aromatic substitution as the underlying mechanism.