A mixture of aldehyde (1.0 mmol), ethyl acetoacetate
(1.0 mmol), urea (1.5 mmol) and nano-g-Fe2O3eSO3H (0.1 g) was
heated at 60 C. After completion of the reaction (monitored by
TLC), the mixture was cooled to room temperature and triturated
with ethyl acetate (5 mL). In the presence of a magnetic stirrer bar,
nano-g-Fe2O3eSO3H moved onto the stirrer bar steadily and the
reaction mixture turned clear within 10 s. The catalyst can be isolated
by simple decantation. After evaporation of the solvent, the
crude product was recrystallized from EtOH/H2O to give a pure
product.