Photoinduced One-Electron Oxidation of Aromatic Selenides: Effect of the Structure on the Reversible Dimerization Reaction

Abstract

The photochemical one-electron oxidation of alkyl aryl selenides was studied by means of laser flash photolysis (355 nm). Quenching of the sensitizers in their excited state leads to selenide radical cation in the presence of selenium derivatives. The π-type dimer of methyl phenyl selenide radical cation was detected at 630 nm at expenses of the monomeric radical cation (530 nm). The effect of modification of the aryl and alkyl substituents was also studied, resulting that the formation of dimers depends on both, the electronic properties and steric hindrance of the substituents. Both effects, an increase in steric hindrance in the alkyl moiety or the presence of strongly electron donor groups in the aromatic substituent that stabilizes the radical cation, prevent the dimer formation.

Synthetic and Mechanistic Studies on 2,3-Dihydrobenzo[b][1,4]-oxaselenines Formation from Selenocyanates

“…Therefore, due to the scarce bibliographic background about this reaction, it was decided to use other selenocyanates and different conditions in order to carry out a more detailed study of this captivating transformation. In this sense, on reaction with m-chloroperbenzoic acid in reflux-ing dichloromethane 4-phenoxyphenoxyetyl selenocyanate (19) 16 was converted into 8-phenoxy-2, 3-dihydrobenzo- [1,4]oxaselenine (20) in a low but reproducible yield (Table 1, entry 2). However, it was not possible to access this heterocyclic system 23 when 2,4-dichlorophenoxyethyl selenocyanate (22) 16 was used as a substrate, which furnished 2,4-dichlorophenoxyethanol (24) instead of 23 (entry 3).…”

“…19 Therefore, at the present time, selenium chemistry is positively an active area of research not only for its potential broad biological action, but also for its interesting chemical behavior. [20][21][22][23] Particularly, seleniumcontaining heterocycles are of growing attention due to their fascinating chemistry and potential pharmacological relevance. [24][25][26] On the other hand, it was described that on treatment with m-chloroperoxybenzoic acid a thiocyanate moiety can be transformed into a sulfinyl cyanide functional group, as it was the case in such a reaction of benzyl thiocyanate with this oxidizing reagent in refluxing dichloromethane, to yield benzylsulfinyl cyanide (Scheme 1).…”

Reactivity of oxidants towards phenyl and benzyl substituted 5-selanylpentanoic acids: radiolytic and theoretical insights

“…22 Interestingly, there is a lack of a detailed discussion regarding the one-electron oxidations of aromatic organoselenium compounds, particularly in an aqueous environment. 23 The hydroxyl radical ( OH) is an extremely reactive oxidant that plays a significant role in biological and environmental systems. 24 Consequently, the development of effective and compatible scavengers or antioxidants for OH and similar oxidants is crucial in the fields of biology and the environment.…”

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)–H and N–H Bonds: Amination of Naphthoquinones with Amines

“…Consequently, an environmentally benign, green, and mild approach is highly desirable for C–N bond construction, which can afford densely substituted C2-aminated naphthoquinones and quinones. In recent decades, visible-light-driven photocatalyzed strategies have been developed, serving as a mild and powerful tool for carbon–carbon, − carbon–heteroatom, − and particularly C–N coupling reactions. − In 2016, MacMillan and co-workers reported photocatalyzed aryl amination using ligand-free Ni salt. The visible-light-mediated C 2 -amination of thiophenes with engineered amine substrates by using DDQ as an organo-photocatalyst has been achieved recently by Lei and co-workers .…”