Efficient Knoevenagel Condensation Reactions Catalyzed by Activated Gel Zirconium(IV) Oxide

Table 4

Screening of solvents.

Entry	Solvent	Temperature (^°C)	Time (h)	Yield (%)^a
1	Dichloromethane	25		—
2	Chloroform	25		Trace
3	Ethyl acetate	25		Trace
4	Methanol	25		Trace
5	Water	25		Trace
6	Tetrahydrofurane (dry)	25		88

Reaction condition: 1a (1 mmol), 2 (1 mmol), ZrOCl₂·8H₂O/NaNH₂ (15 mol %), in solvent (5 mL) at 25^°C.
^aIsolated yields.