Efficient synthesis and free-radical scavenging capacity of new 2,4-substituted tetrahydroquinolines prepared via BiCl₃-catalyzed three-component Povarov reaction, using N-vinylamides.

Efficient synthesis of new structurally different 2-(het)aryl-4-amidyl-substituted tetrahydroquinolines 8-29 is reported. The synthesis based on BiCl(3)-catalyzed three-component Povarov reaction between anilines, (het)aryl aldehydes and enamides offers a fast, safe, and cheap way for efficient tetrahydroquinoline libraries construction. Using N-vinylamides (N-vinylpyrrolidin-2-one and N-vinylacetamide) in this reaction, it was possible to obtain two series of different cis tetrahydroquinolines with antioxidant properties. Among 14 tested compounds, 7 tetrahydroquinolines revealed a prominent anti-radical capacity, equal or higher than that of the commercial antioxidants. Being the most active molecule, the N-[2-(α-furanyl)-6-methoxy-1,2,3,4-tetrahydroquinolin-4-yl] acetamide 21 was ca. 2.2-fold more potent than the well-known antioxidant, vitamin E (α-tocopherol).