The presence of a chalcogen atom at the orthoposition of phenols enhances their radical chain-breaking activity. Here, a copper(I)-catalyzed reaction of 2,6-dibromoand 2,6-diiodophenols with diorganodiselenides has been studied for the introduction of two organoselenium substituents at both ortho-positions of the phenolic radical chainbreaking antioxidants, which afforded 2,6-diorganoselenosubstituted phenols in 80-92% yields having electron-donating CH 3 , and electron-withdrawing CN and CHO functionalities. Additionally, 2,6-diiodophenols with electron-withdrawing CHO and CN groups also afforded novel 5,5'selenobis(4-hydroxy-3-(phenylselanyl)benzaldehyde) and 5,5'selenobis(4-hydroxy-3-(phenylselanyl)benzonitrile) consisting of three selenium and two phenolic moieties along with 2,6diorganoseleno-substituted phenols has been synthesized. The electron-withdrawing CHO group has been reduced by sodium borohydride to the electron-donating alcohol CH 2 OH group, which is desirable for efficient radical quenching activity of phenols. The developed copper-catalyzed reaction conditions enable the installation of two-arylselenium group ortho to phenolic radical chain-breaking antioxidants, which may not be possible by conventional organolithium-bromine exchange methods due to the sluggish reactivity of trianions (dicarba and phenoxide anion), which are generated by the reaction of organolithium with 2,6-dibromophenols, with diorganodiselenides. The antioxidant activities of the synthesized bis and tris selenophenols have been accessed by DPPH, thiol peroxides, and singlet oxygen quenching assay. The radical quenching antioxidant activity has been studied for the synthesized compounds by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The bis-selenophenols show comparable radical deactivating activity, while tris seleno-bisphenols show higher radical deactivating activity than α-tocopherol. Furthermore, the tris seleno-bisphenol shows comparable peroxide decomposing activity with ebselen molecules.
Iodine-mediated intramolecular coupling of CÀ H and NÀ H bonds through radical pathways has been achieved for the synthesis of substituted phenanthridinones from 2phenylbenzamides using iodine, succininmide and di-tertbutylperoxide (DTBP) oxidant in dichloroethane at 130°C. The developed protocol provides substituted phenanthridinones, particularly N-alkyl substituted, which are difficult to access either by base-mediated or transition-metal-catalyzed methodologies due to acidic nature of the CÀ H bond adjacent to nitrogen atom in the amides. Serendipitously, switching the oxidant from DTBP to phenyliodine(III) diacetate (PIDA) afforded spiro-isoindolinones, involving intramolecular CÀ N, intermolecular CÀ O coupling and dearomatization of the phenyl ring in one pot.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.