CONICET | Buscador de Institutos y Recursos Humanos

The photodeprotection of 1,3-dithianes in the presence of thiapyrylium to give back the parent carbonyl compound was performed and the mechanism studied by steady state photolysis, laser flash photolysis (LFP) and theoretical calculations. Electron transfer from dithianes to triplet sensitizer is extremely fast, and the decay of dithianes radical cations was not affected by the presence of water or oxygen, as a consequence of a favorable unimolecular fragmentation pathway. Similar behaviors were observed for dithianes bearing electron-releasing or electron-withdrawing substituents on the aryl moiety, evidencing a C-S bond cleavage to form a distonic radical cation species. The lack of reaction under nitrogen atmosphere, the requirement of oxygen for a good conversion yields, the inhibition of the photodeprotection process by the presence of p-benzoquinone, and the absence of labelled carbonyl final product when the reaction is performed in the presence of H218O, suggest that superoxide anion drives the deprotection reaction. DFT computational study on the reactions with water, molecular oxygen and superoxide radical anion supports the experimental findings.