Chemistry With N-Centered Radicals Generated by Single-Electron Transfer-Oxidation Using Photoredox Catalysis

Abstract

This review covers the recent literature on oxidative generation of N-centered radicals using photoredox catalysis. The concept of proton-coupled electron transfer is briefly discussed. Applications of such reactive N-centered radicals in cascade processes comprising arene amidation, alkene amidation, C—C bond cleavage reactions, and remote C—H functionalization are addressed. In addition, novel reagents allowing for clean oxidative N-radical generation are discussed.

Intermolecular radical carboamination of alkenes

“…Generation of the N-radicals has to proceed under mild conditions that are compatible with the subsequent C-C bond formation. Along these lines, various N-X reagents and oxime derivatives have been exploited for amidyl radical generation [35][36][37][38][39] and the azidyl radical can be mildly accessed through SET oxidation of commercial TMSN 3 . 44,45…”

“…Considering the first class and an alkene as a C-radical acceptor, the reactivity of two different alkenes has to be controlled and the alkene carboamination selectivity is governed by polar effects. 34 Since N-radicals are electrophilic species, [35][36][37][38][39][40][41] initial C-N bond formation occurs highly chemoselective with an electron-rich alkene such as an aliphatic alkene, a vinyl ether or an enamide to give the corresponding nucleophilic C-radical adduct that gets trapped either via reaction with a p-acceptor or via oxidation and subsequent nucleophilic trapping. Transition metal mediated C-C bond formation is also possible.…”

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

“…They can be subjected to either oxidative or reductive SET with an excited photoredox catalyst. The most used scaffolds consist of electron-poor O-acyl and O-aryl hydroxylamines, which are prone to reduction, and α-N-oxy acids, which undergo oxidations followed by β-scission [128,136,139].…”

Tuning the stability of organic radicals: from covalent approaches to non-covalent approaches

“…Therefore, organic radicals serve as key intermediates in a number of organic reactions, including radical polymerization and organic photocatalysis. [8][9][10][11][12][13] Tuning the stability of radicals is crucial for their functions. For radical based functional materials, stability is indispensable.…”