Organophotocatalytic Generation of N‐ and O‐Centred Radicals Enables Aerobic Oxyamination and Dioxygenation of Alkenes

Abstract

A cooperative TEMPO and photoredox catalytic strategy was applied for the first time to the direct conversion of N-H and O-H bonds into N- and O-centred radicals, enabling a general and selective oxidative radical oxyamination and dioxygenation of various β,γ-unsaturated hydrazones and oximes. In the reaction, O2 was employed not only as a terminal oxidant but also as the oxygen source. This protocol provided efficient access to the synthesis of various synthetically and biologically important pyrazoline, pyridazine and isoxazoline derivatives under metal-free and mild reaction conditions. Mechanistic studies revealed that the cooperative organophotocatalytic system functions through two single-electron-transfer (SET) processes.

Visible‐Light Promoted Distereodivergent Intramolecular Oxyamidation of Alkenes

“…[11] Very recently,A kita [12] and Leonori [13] reported the oxyamination of alkenes using visible light photocatalysis. [14] Our group is particularly interestedi nt he one-electron reduction of nitrogen-containing electron-deficient groups. To the best of our knowledge,t he use of ap hotosensitizer to promote ad iastereoselectivity controllable oxyaminationr eactiono ft he same alkeneh as not previously been described.…”

“…To the best of our knowledge,t he use of ap hotosensitizer to promote ad iastereoselectivity controllable oxyaminationr eactiono ft he same alkeneh as not previously been described. [14] Our group is particularly interestedi nt he one-electron reduction of nitrogen-containing electron-deficient groups. [15] Herein, we describe am echanistic distinctd iastereroselectivity controllable intramolecular oxyamidation of alkenesw ith functionalized hydroxylaminesi nt he presence of photocatalysts and electron sacrifices upon irradiation of visible light (see Scheme 1).…”

Recent Advances in Radical Dioxygenation of Olefins

“…[43] This is the first example of visible-light-assisted photocatalytic radical dioxygenation of unsaturated oximes without any transition-metal catalyst. [43] This is the first example of visible-light-assisted photocatalytic radical dioxygenation of unsaturated oximes without any transition-metal catalyst.…”

“…[43] The photoexcited acridinium serves as a 1e-oxidant to oxidize TEMPO through a SET process. [43] The photoexcited acridinium serves as a 1e-oxidant to oxidize TEMPO through a SET process.…”

Integrating TEMPO and Its Analogues with Visible‐Light Photocatalysis

“…Integrating TEMPO with organic photocatalysis has been reported for the activation of N−H and O−H bonds to enable the aerobic oxyamination and dioxygenation of alkenes by acridinium II (Scheme ) . This discovery is very similar to the reaction in Scheme , except that a different type of substrates is used.…”