Mechanism of 1,3-dipolar cycloaddition reactions of indan-1-one enamines with aryl nitrile oxide: a DFT analysis

The mechanism (regioselectivity) of [3+2] cycloaddition reaction of indan-1-one enamines (1ad–1ce) with aryl nitrile oxide (2) has been investigated by density functional theory-based reactivity indices and activation energy calculations at B3LYP/6-31G(d) level of theory in the gas phase. Thermodynamic and kinetic parameters of the possible 3-regio/4-regio regioisomeric pathways have been determined. In all cases, the 3-regio pathways are more favorable compared to the 4-regio alternatives. Our results show that these cycloadditions follow an asynchronous one-step mechanism with a nonpolar character. Theoretical data are in good agreement with the experimental results.