Highly Atom‐Economic and Efficient Electrochemical Selenylative Annulation of 2‐Alkynyl Biaryls

Abstract

AbstractA catalyst‐ and oxidant‐free, highly efficient, scalable, and sustainable synthetic method is developed for the selenylative annulation of 2‐alkynyl biaryls or 2‐heteroaryl‐substituted alkynyl benzenes with readily available diselenides under electrochemical conditions to synthesize a wide variety of selanyl polycyclic aromatic hydrocarbons and polycyclic heteroaromatics in high to excellent yield up to 99% at room temperature in a short time (2‐5 h). The transformation required only electricity as a green reagent and produces hydrogen gas as the only innocuous byproduct. Notably, the green chemistry metrics of the protocol are found excellent. Mechanistic studies revealed a radical pathway being initiated by the in situ generation of the corresponding selenyl radical from diselenides under electrochemical conditions. Significantly, a direct comparison of the electrochemical approach with that of our previously developed iodine‐catalyzed chemical approach revealed that the electrochemical approach is not only catalyst‐ and oxidant‐free, but also more energy‐efficient, high‐yielding, sustainable, and practical.