Photorelease Reaction of Alcohol from 1,4-Naphthoquinone-Based Photodegradable Molecules

Photodegradable molecules have been extensively studied and practically used for on-demand generation of chemical substances under ambient conditions. We here present a series of photodegradable molecules based on 1,4-naphthoquinone (1,4-NQ) with a carbonate linker unit and their substituent effect on the photochemical reactivity for alcohol release. The new compounds 3a-d are synthesized and accessed in methanol, acetonitrile (MeCN), and toluene under UV light irradiation by ¹H NMR and spectroscopy analysis. The aryl ring substituent on the C-2 position significantly affects the photosensitivity of the photorelease reaction in polar and nonpolar solvents. In addition, the coexistence of an external reagent (ethyl vinyl ether) in this photoreaction led to the isolation of Diels-Alder adduct compound 5, rationalizing that the 1,4-NQ framework is transformed to intermediate quinone methylene after photorelease, leading to the dimerization of photobyproduct 4a. From the effect of solvent polarity, reaction rate, and photoreaction quantum yield, we propose a possible reaction mechanism for the photorelease reaction of alcohols from a naphthoquinone-based photodegradable compound via electron transfer.