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

Abstract

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.

Recent progress in the electrochemical selenofunctionalization of alkenes and alkynes

“…In 2022, Ruan et al reported a catalyst and metal-free synthesis of selenylbenzo[ b ]furans using 2-alkynylanisole and diselenide under electrochemical conditions (Scheme 38). 92 The reaction was conducted at a constant current of 10 mA using n Bu 4 NBF 4 as the electrolyte in an undivided cell, in which graphite acted as the anode and a platinum plate acted as the cathode in the co-solvent of CH 3 CN and HFIP. The optimized reaction conditions were then applied to different 2-alkynylanisoles bearing various substituents.…”

Recent Developments in the Synthesis of Organoselenium Compounds Based on the Reactions of Organic Diselenides with Acetylenes

“…A series of electrochemical methods, including the direct electrooxidative selenylation/cyclization of alkynes [112] and the versatile electrochemical synthesis of selenylbenzo[b]furan derivatives [113], were developed.…”

“…An efficient electrochemical protocol for the formation of valuable organylselenylated benzo[b]furan derivatives via the cyclization of 2-alkynylanisoles through an electrooxidative process was developed. Various 3-substituted benzofurans were obtained in good to excellent yields under metal-and oxidant-free mild reaction conditions (Scheme 28) [112]. This approach exhibited good functional group tolerance and could be easily scaled up with good efficiency, providing access to a diverse range of selenylated benzo[b]furans derivatives from available starting materials [112].…”

“…Various 3-substituted benzofurans were obtained in good to excellent yields under metal-and oxidant-free mild reaction conditions (Scheme 28) [112]. This approach exhibited good functional group tolerance and could be easily scaled up with good efficiency, providing access to a diverse range of selenylated benzo[b]furans derivatives from available starting materials [112]. The possibility of using Scheme 27.…”

Direct Electrooxidative Selenylamination of Alkynes: Access to 3‐Selenylindoles

“…Recently, the electrochemical synthesis strategy has emerged as a powerful tool in organic synthesis due to its convenience, environmental sustainability, and controllability. [12] We were inspired by recent achievements in electrochemical transformations on selenylations, [13] and our continuous interest in electrochemical synthesis. [14] Herein, we developed a metal and oxidant-free electrochemical selenylation protocol for the synthesis of 3-selenylindoles from simple 2-alkynylanilines (Figure 2c).…”