GENERAL METHOD: 3-chloro-4-fluorobenzaldehyde (10 mmol), malonic acid (30 mmol, 3.12 g), and piperidine (0.5 mL) were dissolved in pyridine (20 mL), and the reaction mixture was heated under reflux conditions for 4 hours. Upon completion of the reaction, the solution was cooled to room temperature and slowly poured into pre-cooled aqueous 3M HCl solution (100 mL). The precipitated white solid precipitate was collected by filtration and washed sequentially with deionized water (350 mL), 5% w/v NaHCO3 aqueous solution (20 mL) and deionized water (250 mL). The resulting solid was dried in an oven at 60 °C to constant weight. If necessary, the crude product was purified by recrystallization through EtOH/H2O mixed solvent.
