An Efficient One-Pot Green Protocol for the Synthesis of 5-Unsubstituted 3,4-Dihydropyrimidin-2(1H)-Ones Using Recyclable Amberlyst 15 DRY as a Heterogeneous Catalyst via Three-Component Biginelli-Like Reaction

Table 5

Amberlyst 15 DRY catalyzed reaction of cyclohexanone, aldehyde, and urea.

Entry	R	Products^a	Yield^b (%)	M.P (°C)
1	C6H5	3a	93	327–329
2	4-(NO2)C6H4	3b	85	341–343
3	4-(CH3)C6H4	3c	89	348–351
4	2-(Cl)–C6H4	3d	88	321–323

^aReaction conditions: cyclohexanone (1.0 mmol), aldehyde (2.0 mmol), and urea (3.0 mmol) in dry ethanol (10 mL), ion exchange resin (50 mg) at refluxing temperature. ^bIsolated yields.