Synthesis of sulfonated carbon-based solid acid as a novel and efficient nanocatalyst for the preparation of highly functionalized piperidines and acylals: a DFT study

摘要

A novel carbon-based solid-acid nanocatalyst (Sta-SO3H) was simply prepared for the first time by the thermal treatment of sulfuric acid with starch at 180 A degrees C in a sealed autoclave. The catalytic activities of Sta-SO3H as an efficient and reusable catalyst were investigated by the condensation reaction of aldehyde, amine and beta-keto ester for the synthesis of functionalized piperidines under solvent-free conditions at room temperature in good to high yields. Density functional theory calculations were used to study the structure of methyl 1,2,6-triphenyl-4-(phenylamino)-1,2,5,6-tetrahydropyridine-3-carboxylate (MPPC) as well as the thermochemistry of the multicomponent reaction. The theoretically calculated infrared and H-1 nuclear magnetic resonance spectra of MPPC were compared to the experimental data. It was found that the synthesis of MPPC is exothermic accompanied by a decrease in entropy, internal energy and Gibbs free energy of reaction. Good consistency between the calculated and observed spectral data was found. Also, Sta-SO3H has been developed for the synthesis of acylals (1,1-diacetate) in high yields through the reaction of aldehydes with acetic anhydride at room temperature under solvent-free conditions. The mild conditions, eco-friendliness, excellent yields, short reaction times and use of an inexpensive and reusable catalyst are important features of this method.