Table 2. Screening the Model Reaction in the Presence of the Desired Catalyst and Its Related Intermediates^a.

entry	catalyst	yield (%)b
1	Fe3O4	65
2	Fe3O4@SiO2	60
3	Fe3O4@SiO2@(CH2)3–urea–thiazole	70
4	Fe3O4@SiO2@(CH2)3–urea–thiazole sulfonic acid chloride	85

^aReaction conditions:: 4-methylbenzaldehyde (1 mmol, 0.120 g), pyruvic acid (1 mmol, 0.088 g), and 1-naphthylamine (1 mmol, 0.143 g), catalyst: 10 mg.

^bIsolated yields.