Mechanistic Insight into the Oxidation of Organic Phenylselenides by H₂O₂

Abstract

The oxidation of organic phenylselenides by H O is investigated in model compounds, namely, n-butyl phenyl selenide (PhSe(nBu)), bis(phenylselanyl)methane (PhSeMeSePh), diphenyl diselenide (PhSeSePh), and 1,2-bis(phenylselanyl)ethane (PhSeEtSePh). Through a combined experimental ( H and Se NMR) and computational approach, we characterize the direct oxidation of monoselenide to selenoxide, the stepwise double oxidation of PhSeMeSePh that leads to different diastereomeric diselenoxides, the complete oxidation of the diphenyldiselenide that leads to selenium-selenium bond cleavage, and the subsequent formation of the phenylseleninic product. The oxidation of PhSeEtSePh also results in the formation of phenylseleninic acid along with 1-(vinylseleninyl)benzene, which is derived from a side elimination reaction. The evidence of a direct mechanism, in addition to an autocatalytic mechanism that emerges from kinetic studies, is discussed. By considering our observations of diselenides with chalcogen atoms that are separated by alkyl spacers of different length, a rationale for the advantage of diselenide versus monoselenide catalysts is presented.

Role of the Chalcogen (S, Se, Te) in the Oxidation Mechanism of the Glutathione Peroxidase Active Site

“…Two possible mechanisms were investigated for the formation of tellurinic acid, the first proceeding in a single step with direct formation of the product (Scheme a) and the second consisting of a two‐step path that involves the intermediate formation of a hydroxy perhydroxy tellurane (Scheme b). On the basis of the energetics, the stepwise mechanism is disfavored over the direct oxidation (Table ), in analogy with results recently reported for the oxidation of organic selenides by H 2 O 2 . In fact, an activation energy of 16.7 kcal mol −1 is computed for the direct oxidation versus a barrier of 33.1 kcal mol −1 for the formation of the hydroxy perhydroxy tellurane.…”

“…This oxidation results in the formation of a strongly stabilized (−43.6 kcal mol −1 ) telluroxide [ E ‐Te(O)H]. An analogous reaction mechanism was proposed for the direct oxidation of numerous selenides and diselenides . The telluroxide E ‐Te(O)H can then be converted into tellurenic acid F , which is further stabilized by −28.4 kcal mol −1 via an isomerization transition state (TS iso ) with a barrier of 32.1 kcal mol −1 .…”

The Unexpected Role of SeVISpecies in Epoxidations with Benzeneseleninic Acid and Hydrogen Peroxide

“…When 3 was heated in acetonitrile solution at 80 °C, isomerization to 4 was reported, via the proposed selenadioxirane 5 , which had been previously suggested as a potential alternative intermediate in the epoxidation of cyclooctene by Hori and Sharpless (Scheme ). More recently, Orian et al . employed NMR and computational methods to study the hydrogen peroxide oxidation of diphenyl diselenide to 1 and then to the peroxy acid 3 , but did not address the possible formation of the selenonic acid 4 .…”

Study of 8 Types of Glutathione Peroxidase Mimics Based on β-Cyclodextrin

“…A lower k a1 also shows the enzyme activity of the bis-bridged mimics was lower than that of the dual-bridged mimics. Diselenide reacts directly with the thiol substrate [18]. However, the monoselenides must be react first with the peroxide [19].…”