2,5-Dimethylphenacyl carbonates: A photoremovable protecting group for alcohols and phenols

Abstract

Synthesis and photochemistry of a photochemically removable protecting group for alcohols and phenols, based on the 2,5-dimethylphenacyl (DMP) chromophore, is described. DMP carbonates release the corresponding hydroxy group containing molecules in high isolated yields (>70%), with quantum yields Φ = 0.1–0.2 in methanol and Φ = 0.36–0.51 in cyclohexane. The reactions proceed predominantly by the triplet pathway via E-photoenols, the lifetimes of which of approximately 2 s or 3 ms in cyclohexane or methanol, respectively, were determined by laser flash photolysis.