Mechanistic Insights Into the 1,3‐Dipolar Cycloaddition of Diethyl Phosphorylazidate With Isothiocyanates: A DFT Approach

The synthesis of novel 1‐diethylphosphoryl‐4‐substituted tetrazoline‐5‐thiones was achieved in good yields via the 1,3‐dipolar cycloaddition of diethylphosphoryl azidate with phenyl‐ and allyl isothiocyanates. Density functional theory (DFT) calculations were carried out to determine the most stable conformations of resulting tetrazoline‐5‐thiones. The study of the reaction mechanism, based on the evolution of the intrinsic reaction coordinate (IRC) calculation parameters (energy, bond lengths, angles, and dihedral angles) through the different reaction states (SM, TS, Product, and optimized product) and using the Molecular Electron Density Theory (MEDT) method at the SMD‐M062X‐D3/6‐311G(d,p) level of theory, indicates that the reaction may follow an asynchronous, concerted, or two‐step mechanism depending on the specific starting isothiocyanate used conformer.