Table 2.

Synthesis of pyrrolidinones 2a–2h via four-component reactions^a.

Entry	Compd	X	Ar	Yieldb (%)
1	2a	O	p-CH3OC6H4	75c
2	2b	O	p-CH(CH3)2C6H4	73
3	2c	O	p-CH3C6H4	65
4	2d	O	C6H5	87
5	2e	O	m-NO2C6H4	79
6	2f	CH2	p-CH3C6H4	75
7	2g	CH2	m-CH3C6H4	72
8	2h	CH2	p-(CH3)3CC6H4	80

^aReaction condition: 2-aminobenzothiazole (2.0 mmol), acetylenedicarboxylate; (2.0 mmol), aromatic aldehyde (2.0 mmol), piperidine or piperidine (2.0 mmol), p-TsOH (0.5 mmol), in EtOH (10.0 mL), rt, 20 min., 50–60 °C 48 h; ^bIsolated yield.