Silica-ZnCl₂: An Efficient Catalyst for the Synthesis of 4-Methylcoumarins

Table 1

Optimization of the reaction conditions using silica-ZnCl₂.

Entry	Amount of silica-ZnCl2 (mg)	Solvents	Temperature (°C)	Time	Yield (%)^a
1	100	Ethanol	60	5 h	ND
2	100	Ethanol	80	5 h	25
3	100	Methanol	reflux	5 h	Trace
4	100	MeCN	80	5 h	10
5	100	DCM	reflux	5 h	ND
6	100	Neat	80	15 min	95
7	200	Neat	80	15 min	89
8	50	Neat	80	15 min	65

aIsolated yields. Reaction conditions: ethyl acetoacetate (2 mmol), resorcinol (2 mmol), solvent (5 mL), and silica-ZnCl₂.