Table 2.

Synthesis of 1,3,4,5-tetrasubstituted pyrazoles by eliminative 1,3-dipolar cycloaddition.

Entry a	Hydrazonyl Chloride	X	Enaminone	R1	R2	Product	t (h)	Yield 6a–6o (%) b	6:7 c
1	4a	H	5a	CH3	CH3	6a	2	90	97:3
2	4b	4-OCH3	5a	CH3	CH3	6b	2	95	97:3
3	4c	4-CH3	5a	CH3	CH3	6c	2	94	96:4
4	4d	4-NO2	5a	CH3	CH3	6d	2	90	95:5
5	4e	2-Cl	5a	CH3	CH3	6e	2	92	96:4
6	4f	3-Cl	5a	CH3	CH3	6f	2	90	94:6
7	4g	4-Cl	5a	CH3	CH3	6g	2	92	98:2
8	4a	H	5b	Ph	CH3	6h	4	81	93:7
9	4b	4-OCH3	5b	Ph	CH3	6i	4	83	96:4
10	4c	4-CH3	5b	Ph	CH3	6j	4	82	96:4
11	4d	4-NO2	5b	Ph	CH3	6k	4	80	95:5
12	4e	2-Cl	5b	Ph	CH3	6l	4	82	95:5
13	4f	3-Cl	5b	Ph	CH3	6m	4	84	96:4
14	4g	4-Cl	5b	Ph	CH3	6n	4	81	96:4
15	4a	H	5c	Ph	Ph	6o	4	76	94:6

^a Reaction conditions: enaminone 5a–5c (1 eq), K₂CO₃ (2.5 eq), hydrazonyl chloride 4a–4g (1.3 eq) in 12 mL of solvent mixture. ^b isolated yield. ^c regioisomeric ratio values were determined by ¹H NMR analysis of the crude reaction mixture (see Supplementary Materials).