Theoretical analysis of mechanism and regio- and stereoselectivity of 1, 3-dipolar cycloaddition of cyclic nitrone and substituted alkenes by DFT method

This study presents a theoretical investigation of the [3 + 2] cycloaddition (32CA) reaction between cyclic nitrone a1 and substituted alkene b1. The mechanism, regioselectivity, and stereoselectivity of this 32CA reaction were analyzed using transition state theory and reactivity indices obtained from conceptual density functional theory (DFT) at the B3LYP/6-311G(d) level of theory. The results indicate that this cycloaddition reaction proceeds via an asynchronous one-step mechanism, exhibiting a non-polar nature and significant activation energies. These theoretical results are in agreement with the experimental observations. The study also employs topological analyses such as ESP, RDG-NCI, and ELF to determine active sites; distinguish hydrogen bonds, van der Waals interactions, and steric repulsive interactions; and predict electron localization, respectively.