One-Pot Synthesis of Tetrahydropyridine Derivatives: Liquid Salt Catalyst vs Glycolic Acid Promoter. Structure and Antiradical Activity of the New Products

Abstract

© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Diethanolammonium hydrogensulfate (DHS), as a liquid salt, and glycolic acid (GA) were used for the synthesis of highly functionalized tetrahydropyridines (THPs). Due to the simplicity of the reaction procedure, excellent diastereoselectivity, and catalyst regeneration, these green protocols may be considered as an attractive approach for the preparation of THPs. Unlike numerous reported reactions for the synthesis of THPs that last for hours and with heating, GA-promoted reactions finished mostly within an hour and at room temperature. As improvement to other organocatalysed reactions for the synthesis of THPs with moderate yields, this protocol provided good to excellent yields. Application of these procedures produced three vanillic compounds reported here for the first time. Their structure was elucidated based on experimental and theoretical data (IR, 1H NMR, 13C NMR, NOESY, UV-Vis, and DFT). Experimental and theoretical antioxidant evaluation of these compounds has been carried out. DFT thermodynamical parameters supported experimental results that newly synthesized THPs deserve considerable attention as potent radical scavengers.