Stereoselectivity and kinetics of [4 + 2] cycloaddition reaction of cyclopentadiene to para‐substituted E‐2‐arylnitroethenes

In spite of diversified electrophilicity of E‐2‐arylnitroethenes, their 4 + 2] cycloaddition reactions with cyclopentadiene leads to the corresponding 6‐endo‐aryl‐5‐exo‐nitronorbornenes and 6‐exo‐aryl‐5‐endo‐nitronorbornenes as the only reaction products. Stereoselectivity, substituent and solvent effects, and activation parameters, suggest that these reactions occur via a synchronous concerted mechanism on both competing pathways. The experimental results obtained are consistent with the data from B3LYP/6‐31G(d) calculations. Due to high electrophilicity of E‐2‐arylnitroethenes, the reactions studied should be considered as polar 4 + 2] cycloadditions. Copyright © 2011 John Wiley & Sons, Ltd.