Lewis acid-promoted formation of benzoselenazole derivatives using SeO2 as a selenium source

Selenium Dioxide Catalyzed Polymerization of N-doped Poly(benzodifurandione) (n-PBDF) and Its Derivatives

The recent discovery of highly conductive, solution-processable, n-doped poly(benzodifurandione) (n-PBDF) marks a milestone in the development of conducting polymers. Currently, n-PBDF is prepared by either duroquinone-mediated or copper-catalyzed polymerizations, where scalability and cost-effectiveness may present challenges. Here, we report a general, scalable, and cost-effective method for n-PBDF and its derivatives, namely selenium dioxide (SeO2) catalyzed polymerization. We discovered that a catalytic amount of selenium dioxide leads to high monomer conversions (>99 % by NMR). The obtained n-PBDF exhibits a consistently narrow hydrodynamic diameter distribution and its thin films show high conductivities. Furthermore, we revealed that this polymerization involves a mechanism distinct from the previously reported radical pathway. It involves successive Riley oxidation and aldol polycondensation processes. It was also found that the reduced selenium precipitates from dimethyl sulfoxide (DMSO) when the catalytic cycle is terminated, allowing for a straightforward purification process through centrifugation and filtration. This method thus eliminates the need for the costly and slow dialysis process. Finally, we demonstrated that SeO2 catalyzed polymerization is applicable to n-PBDF derivatives, proving the generality of this method.

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

This article describes the detailed analysis of the reaction between arylamines, such as aniline, o-anisidine, and methyl anthranilate, with selenium dioxide in acetonitrile. A systematic analysis of the reaction products with the help of 77Se NMR and single-crystal X-ray crystallography revealed that the reaction progress follows three major reaction pathways, electrophilic selenation, oxidative polymerization, and solvent oxidation. For aniline and o-anisidine, predominant oxidative polymerization occurred, leading to the formation of the respective polyaniline polymers as major products. For methyl anthranilate, the oxidative polymerization was suppressed due to the delocalization of amine lone pair electrons over the adjacent carboxylate function, which prompted the selenation pathway, leading to the formation of two of the isomeric diorganyl selenides of methyl anthranilate. The diaryl selenides were structurally characterized using single-crystal X-ray diffraction. Density functional theory calculations suggest that the highest occupied molecular orbital of methyl anthranilate was deeply buried, which suppressed the oxidative polymerization pathway. Due to solvent oxidation, oxamide formation was also noticed to a considerable extent. This study provides that utmost care must be exercised while using SeO2 as an electrophile source in aromatic electrophilic substitution reactions.

Electrochemical Multicomponent Cascade Reaction for the Synthesis of Selenazol-2-amines with Elemental Selenium

The first example of an electrochemical multicomponent synthesis of selenium-containing compounds with inexpensive and abundant elemental selenium as the selenating reagent was developed. A variety of selenazol-2-amines were constructed in high yields with good functional group tolerance under metal-free and chemical oxidant-free conditions.

Synthesis, Reactions, and Antioxidant Properties of Bis(3-amino-1-hydroxybenzyl)diselenide

Bis(3-amino-1-hydroxybenzyl)diselenide containing two ortho groups was synthesized from 7-nitro-3H-2,1-benzoxaselenole and in situ generated sodium benzene tellurolate (PhTeNa). One-pot synthesis of 1,3-benzoselenazoles was achieved from bis(3-amino-1-hydroxybenzyl)diselenide and aryl aldehydes using acetic acid as a catalyst. The X-ray crystal structure of chloro-substituted benzoselenazole revealed a planar structure with T-shaped geometry around the Se atom. Both natural bond orbital and atoms in molecules calculations confirmed the presence of secondary Se···H interactions in bis(3-amino-1-hydroxybenzyl)diselenide and Se···O interactions in benzoselenazoles, respectively. The glutathione peroxidase (GPx)-like antioxidant activities of all compounds were evaluated using a thiophenol assay. Bis(3-amino-1-hydroxybenzyl)diselenide and benzoselenazoles showed better GPx-like activity compared to that of the diphenyl diselenide and ebselen, used as references, respectively. Based on ⁷⁷Se{¹H} NMR spectroscopy, a catalytic cycle for bis(3-amino-1-hydroxybenzyl)diselenide using thiophenol and hydrogen peroxide was proposed involving selenol, selenosulfide, and selenenic acid as intermediates. The potency of all GPx mimics was confirmed by their in vitro antibacterial properties against the biofilm formation of Bacillus subtilis and Pseudomonas aeruginosa. Additionally, molecular docking studies were used to evaluate the in silico interactions between the active sites of the TsaA and LasR-based proteins found in Bacillus subtilis and Pseudomonas aeruginosa.