Compounds 4a–e and 6a–c^a.

Entry	Diamine	Product	Time (min)	Yield (%)	Mp (°C)
1			10	98	227–229
2			25	76	240–242
3			30	85	280–282
4			15	80	231–233
5			20	73	278–280
6			120	84	314–317
7			90	82	241–243
8			100	78	185–188

^aThe reactions were performed using ninhydrin (1 mmol), malononitrile (1 mmol), diamine (1 mmol), H₂O (10 ml).