Computational study on stereoselective synthesis of substituted 1H-tetrazoles via a click reaction: DFT and QTAIM approaches.

In the present research, the observed stereoselectivity in catalyst-free click synthesis of 1H-tetrazole-5-yl-acrylonitriles has been modeled by means of density functional theory (DFT) employed to investigate the structural and thermochemical aspects of this synthesis in the gas and solution phases. Comparison of our calculated structural parameters of the title compound with the available X-ray crystallographical data demonstrated a reliable agreement. Then, the effect of five different solvents, benzene, chloroform, ethanol, methanol and water was examined via polarized continuum model (PCM) calculations, showing a significant decrease in the computed values of the reaction enthalpy and free energy changes compared with the gas phase results and also the thermodynamical preference in using water solution in comparison with nonpolar solvents such as benzene and other protic and aprotic polar ones such as methanol, ethanol and chloroform that is in confirmation with the experimental observations. Additionally, we have concentrated on origins of the observed stereoselectivity by means of topological electronic indices via quantum theory of atoms in molecule (QTAIM) approach. In this respect, we have assessed the variation of electronic density and its Laplacian at some selected bond critical points of stereoisomer products, their corresponded transition states and intermediate and also construe the experimental elucidations. [ABSTRACT FROM AUTHOR]