A Computational Study on the Radical Cascade Cyclization Mechanism of Synthesis of Benzo[b]oxepinones and Chromanes

Abstract

A computational study on the reaction mechanism of the effective synthesis of sulfonated benzo[b]oxepinones and chromanes by radical cascade cyclization is carried out employing the density functional theory (DFT). Based on our computations, the rate‐determining step is the formation of arylsulfonyl radical for the reaction scheme. Our calculations show that the reaction of 1,8‐ and 1,7‐enynes with arylsulfonyl radical proceeds by forming more thermodynamically stable intermediates. Therefore, 1,8‐enynes prefer 7‐exo‐trig cyclization, while 1,7‐enynes prefer 6‐exo‐trig cyclization. Our computations are consistent with experimental results of the radical cascade cyclization of 1,8‐ and 1,7‐enynes. Moreover, our computations show that if the reaction is carried out in a proton‐free solvent, the elimination product can be obtained from the cascade radical cyclization of the 1,7‐enyne.