Table 2

Entry	Solvent	condition	t	Yield^a(%)
1^b	CH₂Cl₂	Reflux	6h	45
2^b	THF	Reflux	8h	50
3	Neat	60°C	4h	62
4	Neat	80°C	2h	70
5^c	Ultrasonication,neat	200W	8min	96
6^c,d	Ultrasonication,neat	200W	8min	25

^aThe yields refer to the isolated pure products.
^bThe reaction was carried out in 5 mL of solvent.
^cThe reaction was irradiated by using ultrasonicator laboratory system.
^dThe reaction was carried out in the absence of KHSO₄-SiO₂.

Table 2: The reaction between 2-naphthol and benzaldehyde using KHSO₄-SiO₂ as a catalyst under different conditions.