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 2

Optimization of the reaction conditions for the synthesis of 1a ^a.

Entry	Catalyst	Solvent	Time (h)	Yield (%)
1	Amberlyst 15 DRY	Water	4	90
2	Amberlyst 15 DRY	EtOH	5.5	94
3	Amberlyst 15 DRY	CH3CN	6.5	85
4	Amberlyst 15 DRY	THF	6	87
5	Amberlyst 15 DRY	Benzene	10	Trace
6	Amberlyst 15 DRY	Toluene	10	Trace

^aAll reactions were conducted at reflux temperature of the solvent used.