Tetrahydropyranyl Protection and Deprotection of Alcohols using a Niobium-based Brønsted Acid Catalyst

Solid niobium oxide treated with phosphoric acid (NbP) was used as a heterogeneous catalyst in the protection of a series of aliphatic alcohols as tetrahydropyranyl (THP) derivatives. Protection of primary alcohols using this material with strong Brønsted acid sites was achieved in good yields (75%–94%), while moderate values were obtained in the protection of secondary and tertiary alcohols (50%–84%), largely dependent on the steric hindrance in the proximity of the hydroxyl moiety. NbP also catalyzed deprotection of THP ethers derived from primary alcohols and phenol with moderate yields (65%–99%).