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 with under ambient conditions. We here present a series of photodegradable molecule 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 non-polar 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, rationalized that the 1,4-NQ framework is transformed to intermediate quinone methylene after photorelease, leading to the dimerization of photo-byproduct 4a. From the effect of solvent polarity, reaction rate, and the photoreaction quantum yield, we propose a possible reaction mechanism for the photorelease reaction of alcohols from a naphthoquinone-based photodegradable compound via electron transfer.