Synthesis of various pyrazolines 4a–m^a.

Entry	R =	Ar =	Product	Yieldb (%)
1	4-Me–C6H4– 1a	C6H5– 2a	4a	82
2	4-MeO–C6H4– 1b	C6H5– 2a	4b	73
3	3-MeO–C6H4– 1c	C6H5– 2a	4c	57
4	C6H5– 1d	C6H5– 2a	4d	63
5	4-Br–C6H4– 1e	C6H5– 2a	4e	61
6	4-Cl–C6H4– 1f	C6H5– 2a	4f	58
7	4-F–C6H4– 1g	C6H5– 2a	4g	39
8	4-NO2–C6H4– 1h	C6H5– 2a	4h	24
9	2-NO2–C6H4– 1i	C6H5– 2a	4i	45
10	2-HO–C6H4– 1j	C6H5– 2a	4j	82
11	CH3CH2CH2– 1k	C6H5– 2a	4k	86
12	(CH3)2CH– 1l	C6H5– 2a	4l	58
13	4-Me–C6H4– 1a	4-Me–C6H4– 2b	4m	82

^aA solution of aldehyde 1a–l (1.0 mmol) and arylhydrazine 2a, 2b (1.0 mmol) in CH₃CN (1.0 mL) was treated with TfOH followed by styrene 3 (1.0 mmol) and stirred.

^bIsolated yield.