Table 2.

Scope of the Biginelli condensation for the synthesis of 3,4-dihydropyrimidin-2-(1H)-ones catalyzed by MCM-41-APS-PMDA-NHSO₃H (1)^a.

Entry	Aldehyde 3	Product 5	Time (min)	Yield (%)b	mp °C (Obs.)	mp °C (Lit.)
1	4-ClC6H4–		35	95	210–211	210–21172
2	C6H5–		55	87	235–236	234–23673
3	4-NO2C6H4–		50	80	204	224–22774
4	3-NO2C6H4–		60	82	293–295	20475
5	4-CH3OC6H4–		55	89	201–203	202–20476
6	2-ClC6H4–		60	90	211–213	211–21375
7	4-OHC6H4–		55	82	234–236	233–23577
8	2-C4H3S–		45	84	212–214	210–21278
9	4-Me2NC6H4–		45	92	213–215	213–21579
10	4-FC6H4–		60	85	180	18080
11	4-OH-3-MeO-C6H3–		40	84	188–190	188.581

^aReaction conditions: ethyl acetoacetate (2, 1 mmol), aldehydes (3a–k, 1 mmol), urea (4, 1.2 mmol), MCM-41-APS-PMDA-NHSO₃H (1, 15 mg) under solvent-free conditions at 80 °C.

^bIsolated yields were reported.