Aziridination via Nitrogen-Atom Transfer to Olefins from Photoexcited Azoxy-Triazenes

Abstract

Herein, we report that readily accessible azoxy-triazenes can serve as nitrogen atom sources under visible light excitation for the phthalimido-protected aziridination of alkenes. This approach eliminates the need for external oxidants, precious transition metals, and photocatalysts, marking a departure from conventional methods. The versatility of this transformation extends to the selective aziridination of both activated and unactivated multisubstituted alkenes of varying electronic profiles. Notably, this process avoids the formation of competing C-H insertion products. The described protocol is operationally simple, scalable, and adaptable to photoflow conditions. Mechanistic studies support the idea that the photofragmentation of azoxy-triazenes results in the generation of a free singlet nitrene. Furthermore, a mild photoredox-catalyzed N-N cleavage of the protecting group to furnish the free aziridines is reported. Our findings contribute to the advancement of sustainable and practical methodologies for the synthesis of nitrogen-containing compounds, showcasing the potential for broader applications in synthetic chemistry.

Scheme 1. Aziridination of Alkenes

Scheme 2. Synthetic Utility. (A) Deprotection of Aziridine. (B) Derivatization of Aziridine Products

8 mol % 4-CzIPN. Denotes ¹H NMR yield of the aziridine using CH₂Br₂ as an external standard. 0.5 mol % [Ir(dtbbpy)(ppy)₂]PF₆. Isolated yield. Isolated as Bz-protected aziridine. Literature-reported yield.