Energy Transfer Photolysis of N-Enoxybenzotriazoles into Benzotriazolyl and a-Carbonyl Radicals

초록

Irradiation of N-enoxybenzotriazoles with blue LEDs in the presence of photosensitizers productively rendered two reactive radical intermediates, that is, benzotriazolyl-and alpha-carbonyl radicals. The formation of these radicals as discrete species was suggested in the cross-over experiment, and this N-O fragmentation initiated synthetically useful transformations, such as an atom-economical [1,3]-shift and group transfer radical addition, leading to biologically interesting benzotriazolyl derivatives. The facility of these transformations (< 5 min) was rationalized by the triplet state energy transfer and the presence of a very long-lived radical chain (phi = 210 and 131, respectively, for [1,3]-shift and carboamination), which was initiated by the addition of electrophilic benzotriazolyl radicals to the olefin moieties. The N-O homolysis was further characterized by electrochemical and photophysical studies, as well as density functional theory computation.

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