Electrochemical synthesis of peptide aldehydes via C‒N bond cleavage of cyclic amines

Peptide aldehydes are crucial biomolecules essential to various biological systems, driving a continuous demand for efficient synthesis methods. Herein, we develop a metal-free, facile, and biocompatible strategy for direct electrochemical synthesis of unnatural peptide aldehydes. This electro-oxidative approach enabled a step- and atom-economical ring-opening via C‒N bond cleavage, allowing for homoproline-specific peptide diversification and expansion of substrate scope to include amides, esters, and cyclic amines of various sizes. The remarkable efficacy of the electro-synthetic protocol set the stage for the efficient modification and assembly of linear and macrocyclic peptides using a concise synthetic sequence with racemization-free conditions. Moreover, the combination of experiments and density functional theory (DFT) calculations indicates that different N-acyl groups play a decisive role in the reaction activity.

Regio- and Stereoselective Synthesis of 3-Selenylazaflavanones and 3-Selenylflavanones via Electrochemically Facilitated Selenylation Cascade

Herein, an oxidant- and metal-free electrochemical selenylation reaction of chalcones with diselenides for the synthesis of 3-selenylazaflavanones and 3-selenylflavanones at room temperature was reported. The method proceeded under mild conditions, exhibited a broad substrate scope, and provided the selenylated products in moderate to excellent yields with high regio- and stereoselectivity. The reaction could also be readily scaled up with high efficiency. Detailed mechanistic studies through control experiments disclosed that a selenium-based radical might participate in this electrochemical transformation.

Recent Advances in the Use of Diorganyl Diselenides as Versatile Catalysts

The importance of organoselenium compounds has been increasing in synthetic chemistry. These reagents are well-known as electrophiles and nucleophiles in many organic transformations, and in recent years, their functionality as catalysts has also been largely explored. The interest in organoselenium-based catalysts is due to their high efficacy, mild reaction conditions, strong functional compatibility, and great selectivity. Allied to organoselenium catalysts, the use of inorganic and organic oxidants that act by regenerating the catalytic species for the reaction pathway is common. Here, we provide a comprehensive review of the last five years of organic transformations promoted by diorganyl diselenide as a selenium-based catalyst. This report is divided into four sections: (1) cyclisation reactions, (2) addition reactions and oxidative functionalisation, (3) oxidation and reduction reactions, and (4) reactions involving phosphorus-containing starting materials.

Electrochemical Selenylation of Sulfoxonium Ylides for the Synthesis of gem-Diselenides as Antimicrobials against Fungi

Organoselenium compounds are important scaffolds in pharmaceutical molecules. Herein, we report metal-free, electrochemical, highly chemo- and regioselective synthesis of gem-diselenides through the coupling of α-keto sulfoxonium ylides with diselenides. The versatility of the electrochemical manifold enabled the selenylation with ample scope and broad functional group tolerance, as well as setting the stage for modification of complex bioactive molecules. Detailed mechanistic studies revealed that the key C-Se bond was constructed using n-Bu₄NI as an electrolyte and catalyst through the electrosynthetic protocol. Finally, the desired α-keto gem-diselenides showed excellent antimicrobial activity against Candida albicans, which can be identified as the lead compounds for further exploration.

Direct Electrooxidative Selenylation/Cyclization of Alkynes: Access to Functionalized Benzo[b]furans

A mild, practical, metal and oxidant-free methodology for the synthesis of various C-3 selenylated benzo[b]furan derivatives was developed through the intramolecular cyclization of alkynes promoted with diselenides via electrooxidation. A wide range of selenium-substituted benzo[b]furan derivatives were obtained in good to excellent yields with high regioselectivity under constant current in an undivided cell equipped with carbon and platinum plates as the anode and cathode, respectively. Moreover, the convergent approach exhibited good functional group tolerance and could be easily scaled up with good efficiency, providing rapid access to a diverse range of selenylated benzo[b]furans derivatives from simple, readily available starting materials.