Effect of H₃PMo₇W₅O₄₀·24H₂O loading on support kaolin for the synthesis of ethyl 6-methyl-2-oxo-4-phenyl-1,2,3,4-tetrahydropyrimidine-5-carboxylate (4a)^a.

Entry	Catalyst	Timeb (min)	Yieldc (%)
1	Pure kaolin	120	45
2	Bulk H3PMo7W5O40·24H2O	55	60
3	10% PMo7W5/kaolin	35	68
4	15% PMo7W5/kaolin	20	85
5	20% PMo7W5/kaolin	08	95
6	25% PMo7W5/kaolin	08	95

^aReaction conditions: benzaldehyde (3 mmol), ethyl acetoacetate (3 mmol), urea (3.2 mmol) and PMo₇W₅/kaolin catalyst.

^bReaction progress monitored by TLC.

^cIsolated yields.