Three-component imino Diels–Alder reaction with essential oil and seeds of anise: generation of new tetrahydroquinolines

A simple and efficient one-pot method for the synthesis of 4-anisyl-2-phenyl-1,2,3,4-tetrahydroquinoline derivatives using a three-component imino Diels–Alder cycloaddition (Povarov reaction) between anilines, benzaldehyde, and trans-anethole in the presence of acidic catalysts is shown. New substituted tetrahydroquinolines are reported and their direct preparation from the anise essential oil is described. Also, a simple procedure of the same tetrahydroquinolines from the anise seeds under supercritical fluid (CO2) conditions has been reported.