IR, 1H NMR and DFT studies of novel bis-Betti base derivatives of 2,6-dihydroxynaphthalene: Thermodynamic control of diastereoselectivity and configurational preference

Diastereoselectivity and configurational preference for synthetic reaction of novel bis-Betti base derivatives of 2,6-dihydroxynaphthalene were studied through density functional theory (DFT). Enthalpy, entropy and Gibbs free energy of reactions as well as stereochemistry, thermodynamic stability and spectroscopic analysis of products were investigated. The calculated 1H nuclear magnetic resonance (NMR) and infrared (IR) spectra of different configurations were compared to experimental data in order to find the preferred isomer. The diastereoselectivity of reaction was estimated through the calculated equilibrium distribution of stereoisomers. According to these results, preparation of bis-Betti bases is an exothermic process accompanied by a decrease in entropy. The calculated gas phase heats of formation of title compounds are positive. Since the energy difference between stereoisomers is quite small, the change of Gibbs free energy during the reaction favors one configuration over other possibilities. These results are in good agreement with the experimental observations.