General method: 1,3-Cyclohexanedione (8.9 mmol, 1 eq.) was mixed with acrylic acid (10.6 mmol, 1.2 eq.) in a reaction vial. Ammonium acetate (10.6 mmol, 1.2 eq.) was then added. The reaction mixture was thoroughly mixed using a spatula and heated with stirring at 80 °C for 5 h under nitrogen protection. After completion of the reaction, it was cooled to room temperature and the reaction mixture was diluted with 10 mL of distilled water followed by two extractions with ethyl acetate (2 × 10 mL). The organic extracts were combined and dried with anhydrous Na2SO4. After filtration, the solvent was removed by evaporation under reduced pressure and the resulting crude product was purified by column chromatography (eluent: ethyl acetate/hexane) to afford the target compound 3,4,7,8-tetrahydroquinoline-2,5(1H,6H)-dione. Characterization data of the compounds are provided.
