Abstract
Nitrene transfer reactions represent one of the key reactions to rapidly construct new carbon-nitrogen bonds and typically require transition metal catalysts to control the reactivity of the pivotal nitrene intermediate. Herein, we report on the application of iminoiodinanes in amination reactions under visible light photochemical conditions. While a triplet nitrene can be accessed under catalyst-free conditions, the use of a suitable photosensitizer allows the access of a nitrene radical anion. Computational and mechanistic studies rationalize the access and reactivity of triplet nitrene and nitrene radical anion and allow the direct comparison of both amination reagents. We conclude with applications of both reagents in organic synthesis and showcase their reactivity in the reaction with olefins, which underline their markedly distinct reactivity. Both reagents can be accessed under mild reaction conditions at room temperature without the necessity to exclude moisture or air, which renders these metal-free, photochemical amination reactions highly practical.
Highlights
Nitrene transfer reactions represent one of the key reactions to rapidly construct new carbonnitrogen bonds and typically require transition metal catalysts to control the reactivity of the pivotal nitrene intermediate
We show that iminoiodinanes are suitable, benchstable reagents that can be used to access either a triplet nitrene or a nitrene radical anion intermediate under photochemical or photocatalytic conditions, respectively
While the HOMO of 1a is predominantly associated to electron density at the nitrogen atom (Fig. 2a), the electron distribution in the LUMO is shifted to the iodine atom (Fig. 2a and Supplementary Fig. 6), which could facilitate photolysis reactions and formation of nitrene intermediates
Summary
Nitrene transfer reactions represent one of the key reactions to rapidly construct new carbonnitrogen bonds and typically require transition metal catalysts to control the reactivity of the pivotal nitrene intermediate. One concept harnesses the use of metalcatalyzed nitrene transfer reactions under UV light photochemical conditions to facilitate the formation of metal-nitrene intermediates (Fig. 1b)[24,25,26,27,28]. Further exploration concerned the evaluation of the reaction mechanism and an understanding of the distinct reactivity of triplet nitrene and nitrene radical anion by theory and experiment (Fig. 4).
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