TABLE 1.

Optimization of the reaction conditions for the model reaction (1 mmol benzaldehyde and 2 mmol β-naphthol in 10 ml solvent). All yields are reported after the separation, purification, and weighting of the product.

Entry	Catalyst	Catalyst amount (mol%)	Solvent	Temperature (°C)	Time (h)	Yield (%)	Optimization process for
1	—	—	Ethanol	Reflux	6	trace	Catalyst
2	SnCl2	5	Ethanol	Reflux	6	30
3	Nano silica	5	Ethanol	Reflux	6	trace
4	Sn (II)/nano silica	5	Ethanol	Reflux	6	40
5	Sn (II)/nano silica	5	Ethanol	Reflux	6	45	Catalyst
6	Sn (II)/nano silica	10	Ethanol	Reflux	6	60	amount
7	Sn (II)/nano silica	20	Ethanol	Reflux	6	60
8	Sn (II)/nano silica	10	-	120	6	35	Solvent
9	Sn (II)/nano silica	10	THF	Reflux	6	0
10	Sn (II)/nano silica	10	H2O	Reflux	6	10
11	Sn (II)/nano silica	10	Ethanol	Reflux	6	60
12	Sn (II)/nano silica	10	Ethanol	50	6	25	Temperature
13	Sn (II)/nano silica	10	Ethanol	25	6	0
14	Sn (II)/nano silica	10	Ethanol	Reflux	1	30	Time
15	Sn (II)/nano silica	10	Ethanol	Reflux	3	60
16	Sn (II)/nano silica	10	Ethanol	Reflux	7	60