Radical Chain Breaking Bis(ortho‐organoselenium) Substituted Phenolic Antioxidants

Abstract

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.

Benzimidazole- and Imidazole-Fused Selenazolium and Selenazinium Selenocyanates: Ionic Organoselenium Compounds with Efficient Peroxide Scavenging Activities

“… Among these, diselenide-based GPx mimics, such as compounds 2 – 4 , are extensively studied and reported as very active catalysts in the effective reduction of peroxides . Additionally, a series of selenenylamides, cyclic selenenate ester ( 5 ), and various monoselenides are reported as GPx mimics. For example, Back and co-workers have reported bis­(3-hydroxypropyl) selenide 6 as a novel GPx mimic that exhibits catalytic activity via the formation of spirodioxaselenanonane species …”

Isolation of monomeric copper(ii) phenolate selenoether complexes using chelating ortho-bisphenylselenide-phenolate ligands and their electrocatalytic hydrogen gas evolution activity

“…Our initial effort to isolate copper phenolate selenoether complexes from the ortho -bisphenylselenide-phenol ligands was unsuccessful, even though several variations in the base and copper salts were made. The ortho -bisphenylselenide-phenol chelating ligands ( 1a–1d ) 27 with 1,10-phenanthroline copper( i ) iodide in the presence of a triethylamine base have led to the successful precipitation of green-colored copper phenolate selenoether complexes (Scheme 1). The crystallization from CH 2 Cl 2 : hexane provided green-colored copper( ii ) phenolate selenoether 2a in a 96% yield.…”

“…The synthesis of 2d was carried out in a similar way as described for 2a from 5,5′selenobis(4-hydroxy-3-( phenylselanyl)benzonitrile) 1d. 27 The obtained orange precipitate was filtered and dried under vacuum. The precipitate was then crystallized in a CH 2 Cl 2 / hexane (1 : 3) solvent mixture to yield orange-colored crystals.…”

Exploring Chain-Breaking Antioxidants Profile Dependent at Various pH and co-Antioxidants

“…32 Very recently, Kumar et al exhibited the chain-breaking antioxidant properties of hydroxy spiroselenurane 5 33 containing tetravalent selenium and bis-phenylselenide phenols as well as tris-selenol-bisphenol 6. 34…”