Regio- and Diastereoselectivity of 1,3-dipolar Cycloaddition Reaction Between Sugar-Derived Nitrile Oxides and trans-Ethylcinnamate: DFT and QTAIM Analysis

Various aspects of the 1,3-dipolar cycloaddition between sugar-derived nitrile oxides and trans-ethylcinnamate were analyzed using density functional theory. Frontier molecular orbitals reveal that the reaction follows normal electron demand, further supported by reactivity indices. Methyl cation/anion affinity was employed to demonstrate electron displacement. Topological parameters were analyzed at critical bond points, and non-covalent interaction gradient isosurfaces were used to analyze the nature of the newly forming α-bonds at transition state. Activation energy results align with experimental observations, demonstrating that the reaction is perfectly regioselective. However, electron density findings favor the opposite addition.