The Theoretical and Experimental Study of DiazomethaneStyrene [3+2]-Cycloadditions

Pyrazolines are an important class of heterocyclic compounds known for their biological activities, making them attractive objects for medicinal chemistry. This study investigated the regioselective [3+2]-cycloaddition of diazomethane with para-substituted styrenes featuring electron-withdrawing (EWG) and electron-donating (EDG) groups. Experimental results have demonstrated that the electronic properties of substituents significantly affect the reaction efficiency and regioselectivity, as well as the product stability. At the same time, EWG provided lower activation barriers and higher reaction yields. Calculations performed by the density functional theory (DFT) method confirmed the experimental data allowing us to understand in detail the reaction mechanism, activation energy values, and thermodynamic parameters. This integrated experimental and theoretical approach improves understanding of the effects of substituents, contributing to the rational design of substituted pyrazolines.