Visible‐Light‐Promoted Iminyl‐Radical Formation from Acyl Oximes: A Unified Approach to Pyridines, Quinolines, and Phenanthridines

Abstract

A unified strategy involving visible-light-induced iminyl-radical formation has been established for the construction of pyridines, quinolines, and phenanthridines from acyl oximes. With fac-[Ir(ppy)3 ] as a photoredox catalyst, the acyl oximes were converted by 1 e(-) reduction into iminyl radical intermediates, which then underwent intramolecular homolytic aromatic substitution (HAS) to give the N-containing arenes. These reactions proceeded with a broad range of substrates at room temperature in high yield. This strategy of visible-light-induced iminyl-radical formation was successfully applied to a five-step concise synthesis of benzo[c]phenanthridine alkaloids.

Visible‐Light‐Induced Direct Oxidative C−H Amidation of Heteroarenes with Sulfonamides

“…[12] Nicewicz [13a] and Xia [13b] reported visible-light-induced oxidative CÀHa mination of (hetero)arenes via arene cation radicals using nonactivatedN -heterocyles as nucleophiles ( Figure 1b). Inspired by these work, as well as our research interests on visible-light-mediatedN CR chemistry, [16][17] we soughtt od evelop ad irect oxidative CÀHa midationo f( hetero)arenes with nonactivateds ulfonamides under photoredox catalysis [18] (Figure 1c). Inspired by these work, as well as our research interests on visible-light-mediatedN CR chemistry, [16][17] we soughtt od evelop ad irect oxidative CÀHa midationo f( hetero)arenes with nonactivateds ulfonamides under photoredox catalysis [18] (Figure 1c).…”

A new era for homolytic aromatic substitution: replacing Bu3SnH with efficient light-induced chain reactions

“…Iminyl radical intramolecular HAS using acyl oximes, 67 and chloroimines 68 allowed the respective formation of a variety of phenanthridines and quinoxalin-2-ones (Scheme 22). The generation of iminyl radicals from acyl oximes is reminiscent of earlier approaches by Walton using UV-light (Scheme 11), 41,42 and allow aldehydes to act as precursors for in situ generated acyl oximes.…”

Visible‐Light‐Mediated Generation of Nitrogen‐Centered Radicals: Metal‐Free Hydroimination and Iminohydroxylation Cyclization Reactions

“…[15] Such an approach would clearly benefit from the facile synthesis of aryl oximes,and we hoped that the high structural modularity of the O-aryl hydroxylamines would allow us to identify substrates that do not require the use of transition-metalbased photocatalysts. [16] Herein, we describe the successful implementation of this approach and the development of novel, transition-metal-free,v isible-light-mediated hydroimination and iminohydroxylation cyclization reactions (Scheme 1B).…”