Synthesis and density functional theoretical study of steroidal spiro-triazolidinone

The reaction of 3β-chloro-5α-cholestan-6-one semicarbazone 1 with hydrogen peroxide at 0 °C gives 3β-chloro-5α-cholestan-6-spiro-1′,2′,4′-triazolidine-3′-one 2 as a product. The structural assignment of the product was confirmed on the basis of its elemental, analytical and spectral data. The ab initio calculations were performed by using density functional theory (DFT) at B3LYP/6-31G* basis set in order to describe a free radical reaction mechanism. The reaction proceeds through two radical intermediates formation. The mechanism of the reaction was explained by using frontier molecular orbital (FMO), spin electronic density map, encoded electrostatic potential map and atomic charges. It was found that the localization of frontier orbitals and the flow of atomic charges of all the calculated structures support the present reaction mechanism. The molecular properties like total energy, dipole moment and hardness of each optimized structure, were also explained. Stability of all the optimized structures in this study was supported by their respective fundamental frequencies and energy minima.