Chemoselective electrochemical seleno-cyclization of dienes to medium-sized benzo[b]azocines

Abstract

The preparation of medium-sized benzo[b]azocines has always been challenging because of inherently unfavorable enthalpy and entropy factors. This report presents a novel approach for accessing 8-membered seleno-benzo[b]azocines via electrochemically-driven seleno-cyclization. This method enables room-temperature preparation of various structurally diverse medium-sized seleno-benzo[b]azocines. The facile deselenation of the seleno-cyclization products to generate functionalized dienes is an additional benefit of this indispensable reaction. Mechanistic insights are presented based on radical inhibition experiments and cyclic voltammetry measurements, which elucidate the radical pathway. Finally, density functional theory calculations further rationalize the rate-determining step and the unique chemoselectivity observed in this transformation.