Computational Investigation of Reaction Pathways and Electronic Structure in a Prototypical Organic Cyclization System

<title>Abstract</title> <p>A density functional theory (DFT) investigation was conducted to characterize the mechanistic landscape, transition‑state energetics, and electronic structure of a model intramolecular cyclization reaction relevant to heterocycle formation. Geometry optimizations, frequency analyses, and intrinsic reaction coordinate (IRC) calculations were performed using the B3LYP/6‑311 + G(d,p) level of theory. Results indicate that cyclization proceeds through a single, well‑defined transition state featuring significant charge redistribution and early bond formation. Natural bond orbital (NBO) analysis reveals stabilization driven by hyperconjugative interactions between the nucleophilic lone pair and the forming σ‑framework. These findings provide mechanistic clarity for synthetic chemists designing analogous cyclization systems and demonstrate the utility of computational methods for predicting reactivity trends in organic transformations.</p>