Table 1. Optimization of solvent and Fe₃O₄@BTC NCs loading in the synthesis of in dihydropyrano[2,3-c]pyrazoles derivatives^a.

Entry	Catalyst (g)	Solvent	Condition	Time (min)	Yieldb (%)
1	Without catalyst	—	RT	10	Trace
2	Without catalyst	—	Reflux	10	25
3	Without catalyst	—	U.S.(60 W) (RT)	10	30
4	Fe3O4@BTC (0.01)	—	U.S.(60 W) (RT)	10	50
5	Fe3O4@BTC (0.02)	—	U.S.(60 W) (RT)	10	75
6	Fe3O4@BTC (0.03)	—	U.S.(60 W) (RT)	10	80
7	Fe3O4@BTC (0.04)	—	U.S.(60 W) (RT)	10	92
8	Fe3O4@BTC (0.05)	—	U.S.(60 W) (RT)	10	92
9	Fe3O4@BTC (0.04)	H2O	U.S.(60 W) (RT)	20	30
10	Fe3O4@BTC (0.04)	DCM	U.S.(60 W) (RT)	10	40
11	Fe3O4@BTC (0.04)	CH3OH	U.S.(60 W) (RT)	15	41
12	Fe3O4@BTC (0.04)	C2H5OH	U.S.(60 W) (RT)	7	45
13	Fe3O4 (0.04)	—	U.S.(60 W) (RT)	15	35
14	FeCl2 (0.04)	—	U.S.(60 W) (RT)	20	30
15	BTC (0.04)	—	U.S.(60 W) (RT)	14	37

^aRT – room temperature; reaction conditions: benzaldehyde (1 mmol), hydrazine hydrate (1 mmol), ethyl acetoacetate (1 mmol), malononitrile (1 mmol), ultra-sonication (60 W).

^bIsolated yield.