Efficient Formation and Cleavage of Benzylidene Acetals by Sodium ­Hydrogen Sulfate Supported on Silica Gel

NaHSO4·SiO2 was used as an efficient heterogeneous catalyst for both the formation and the cleavage of benzylidene ­acetals. This catalyst is compatible with many functional or protective groups. Under different solvent systems, either the formation or the cleavage of benzylidene acetals was carried out smoothly in ­excellent yields and with good chemoselectivity.