Table 2.

Optimization for the synthesis of pyrimidine-5-carbonitrile with 4-chlorobenzaldehyde, urea, malononitrile and bone char-nPrN-SO₃H as catalyst.

Entry	Catalyst (mol%)	Solvent	Temperature (°C)	Time (min)	Yield%
1	0.00	-	80	240	40
2	0.24	-	80	65	92
3	0.32	-	80	40	95
4	0.4	-	80	5	97
5	0.4	Water	Reflux	240	75
6	0.4	Acetonitrile	Reflux	240	50
7	0.4	n-hexane	Reflux	240	35
8	0.4	Ethanol	Reflux	240	67
9	0.4	Ethanol: water 50:50	Reflux	240	71
10	0.4	-	30	60	45
11	0.4	-	50	35	67
12	0.4	-	70	15	85