Optimization of conditions for the synthesis of calyx[4]resorcinol conformers containing 4-dimethylammoniophenyl fragments on the lower rim of the molecule based on the response surface methodology using three-level box-behnken plans

The response surface methodology using three-level Box-Behnken plans was applied in order to optimize the yield of the cone and chair conformers in the synthesis of calix[4]resorcinol functionalized with 4-dimethylammoniophenyl group along the lower rim. We used data from one-factor experiments in which the temperature, reaction time, and molar ratio of HCl to the reactants of the reaction mixture were varied to plot the response surfaces. The ratio of conformers was calculated based on the analysis of ¹H NMR spectra of the products isolated from the reaction mixture. The adequacy of the proposed mathematical models for determining the yields of chair and cone conformations is confirmed by a high correlation coefficient ( R 0.99979). Optimal conditions were found for the maximum yield of the chair conformation (50°C, 2 h, molar ratio of HCl to reagents in the reaction mixture is 1-1.5, yield 100%). The optimal conditions for obtaining the cone conformation are: temperature 68.6°С, stirring time in the range of 2.24-6.44 h and the molar ratio of HCl to reagents in the reaction mixture is 2. Carrying out the synthesis under these conditions leads to the yield of the cone conformation in the range of 57.70-58.07%.

Calix[4]resorcinol, cone and chair conformers, response surface methodology, three-level Box- Behnken designs