The results of optimization of reaction conditions for compound 4j synthesis^a.

Entry	Solvent	Temperature (°C)	Time (h)	Yieldb (%)
1	Ethanol	Reflux	24	75
2	Water	Reflux	24	50
3	Methanol	Reflux	24	61
4	DMSO	100	24	52
5	DMF	100	24	52
6	Dioxane	100	24	28
7	THF	Reflux	24	40
8	Acetonitrile	Reflux	24	38
9	Ethyl acetate	Reflux	24	30
10	Chloroform	Reflux	24	0
11	Toluene	100	24	0
12	Solvent-free	100	24	0
13	Ethanol	RT	24	0
14	Ethanol	40	24	0
15	Ethanol	60	24	34
16	Ethanol	Reflux	24	75
17	Ethanol	Reflux	10	75
18	Ethanol	Reflux	2	75
19	Ethanol	Reflux	1.5	60
20	Ethanol	Reflux	1	41

^aReaction conditions: 5-chloroisatin (1 mmol), 3-amino-4-bromo-1H-pyrazole (1 mmol), tert-butyl isocyanide (1 mmol), solvent (3 mL).

^bIsolated yield in the presence of CeCl₃·7H₂O catalyst (30 mol%).