Photolabile Protection of Alcohols, Phenols, and Carboxylic Acids with 3-Hydroxy-2-Naphthalenemethanol

Irradiation of alcohols, phenols, and carboxylic acids “caged” with the (3-hydroxy-2-naphthalenyl)methyl group results in fast (k_release ≈ 10⁵ s⁻¹) release of the substrates with good quantum (Φ = 0.17−0.26) and chemical (>90%) yields. The initial byproduct of the photoreaction, 2-naphthoquinone-3-methide, reacts rapidly with water (k_H2O = 144 ± 11 s⁻¹) to produce parent 3-hydroxy-2-naphthalenemethanol. The o-quinone methide intermediate can be also trapped by other nucleophiles or converted into a photostable Diels−Alder adduct with ethyl vinyl ether.