Herein, we describe a simple and efficient route to access aniline-derived diselenides and evaluate their antioxidant/GPx-mimetic properties. The diselenides were obtained in good yields via ipso-substitution/reduction from the readily available 2-nitroaromatic halides (Cl, Br, I). These diselenides present GPx-mimetic properties, showing better antioxidant activity than the standard GPx-mimetic compounds, ebselen and diphenyl diselenide. DFT analysis demonstrated that the electronic properties of the substituents determine the charge delocalization and the partial charge on selenium, which correlate with the catalytic performances. The amino group concurs in the stabilization of the selenolate intermediate through a hydrogen bond with the selenium.

We developed a promising synthetic methodology for the regioselective photocatalyzed 3-selenocyanation of indoles, employing potassium selenocyanate (KSeCN) and a blue LED light. The 3-selanylindoles have been emerging as a potentially bioactive class of compounds and already have demonstrated anti-inflammatory, antinociceptive and anticancer properties. There are in the literature several methodologies for their preparation; for example, applying intermolecular cyclization with Se-based electrophilic species. Therefore, it is of interest to seek innovative and effective methodologies to selectively access this class of molecules. Furthermore, the photocatalytically formed NCSe· radical can react directly with the N-heterocycle unsaturated substrates, affording the desired compound more effectively than other electrophilic selenium species. In addition, the 3-selenocyanato-1H-indole derivatives can be employed as precursor to obtaining diselenides, through a reduction–oxidation reaction sequence. The new method employs indole as unsaturated N-heterocycle substrate, and 1.3 equiv. of potassium selenocyanate as a selenium source, in the presence of 5.0 mol% of eosin Y, an organic photocatalyst, and 1.0 mL of acetonitrile. The system was stirred and irradiated with a blue LED light for 5 h, and the crude was purified using column chromatography. Thus, as a result, we developed an efficient and smoothly methodology to prepare 3-selenocyanato-1H-indole derivatives, in good yields.

We established a new visible-light-mediated protocol for the regioselective β-hydroxyselenylation of olefins, employing benzeneseleninic acid as substrate. Regarding a novel approach, the benzeneseleninic acid emerges as an efficient and affordable reagent to be used as an electrophilic selenium source that can be easily converted to selenium-based radical species under visible-light conditions. In this sense, the photocatalytically formed PhSe• radical can react directly with unsaturated substrates, including alkenes, to access a new C–Se bond and a carbon-centered radical intermediate, which finally is trapped by a hydroxyl radical species, delivering the β-hydroxyselanyl compounds. Thus, despite the versatile utilities in organic synthesis, such as building blocks, the β-hydroxyselanyl compounds have demonstrated important biological activities. Based on that, we concentrated our efforts on developing a robust, effective, and environmentally benign methodology for their preparation. The optimal condition involves the reaction between styrene and 1.0 equivalent of phenylseleninic acid, in the presence of 5.0 mol% of eosin Y, as a cheap and easily available photocatalyst, with DMSO promoting the reaction medium. Satisfactorily, the system was irradiated with blue LED light for 2 h, to deliver the desired products in good yields.