Competing Reaction Mechanisms and Origin of Selectivity in Base-Controlled (4 + 1) versus (2 + 1)/(4 + 2) Annulations of <i>o</i> -Aminochalcones with γ-Bromocrotonates

calculations to provide a quantitative thermodynamic perspective. To further probe the origin of diastereoselectivity, we performed noncovalent interaction (NCI), atoms in molecules (AIM), and natural bond orbital (NBO) second-order perturbation analyses. Collectively, these results offer mechanistic insights into the fundamental principles governing base-mediated reactions of γ-bromocrotonates, revealing key electronic and steric factors that dictate both chemoselectivity and diastereoselectivity.