Catalyst-free visible-light-induced decarbonylative C–H alkylation of quinoxalin-2(1H)-ones

Abstract

Direct functionalization of C(sp3)–H bonds is an effective, straightforward method for accessing a diverse array of heteroarene derivatives. However, its wide application is limited by the need for to use...

NPh3-Mediated WO3-Photocatalyzed Semiheterogeneous Hydroxylation of Aryl and Alkyl Boronic Acids

“…Conducting the semiheterogeneous hydroxylation with other semiconductor photocatalysts, including g-C 3 N 4 , TiO 2 , CdS, CdSe, and ZnO, gave lower efficiencies (entry 2). Without any photocatalyst, the template reaction gave 2a in 28% yield (entry 3), presumably due to the fact that 1a can absorb ultraviolet–visible light and act as a photosensitizer (entry 3) . Exchanging NPh 3 with a different redox mediator diminished the reaction yield, delivering product 2a in 69–79% yields when NHPI, Cp 2 Fe, or DIPEA was used (entry 4).…”

Visible Light‐Enabled Decarboxylative Alkylation of Quinoxalin‐2(1H)‐ones using Alkyl Carboxylic Acids via Energy Transfer Process

“…Speaking of energy transfer processes in the context of the present work, the excited photosensitizers are known to transfer its energy to ground‐state molecular oxygen ( 3 O 2 ) to generate singlet oxygen ( 1 O 2 ), to attain selective chemical transformations [71–73] . Also, literature precedents suggested that quinoxalin‐2(1 H )‐ones could assist energy transfer to ground‐state molecular oxygen ( 3 O 2 ) to generate a singlet oxygen ( 1 O 2 ), to accomplish the chemical conversions [19,74–76] . So, we harped upon an observation that singlet oxygen ( 1 O 2 ), could help in the generation of alkyl radical via a hydrogen‐atom‐transfer ( HAT ) process, which upon coupling with quinoxalin‐2(1 H )‐ones, would be converted to 3‐functionalized quinoxalin‐2(1 H )‐ones.…”

“…[71][72][73] Also, literature precedents suggested that quinoxalin-2(1H)-ones could assist energy transfer to ground-state molecular oxygen ( 3 O 2 ) to generate a singlet oxygen ( 1 O 2 ), to accomplish the chemical conversions. [19,[74][75][76] So, we harped upon an observation that singlet oxygen ( 1 O 2 ), could help in the generation of alkyl radical via a hydrogen-atomtransfer (HAT) process, which upon coupling with quinoxalin-2(1H)-ones, would be converted to 3functionalized quinoxalin-2(1H)-ones. Corroborating the above hypothesis, we have developed an efficient, catalyst-and oxidant-free protocol to construct C-3 alkylated quinoxalin-2(1H)-ones using visible light.…”

Self-Catalyzed, Visible-Light-Induced Selective C3–H Aroylation of Quinoxalin-2(1H)-ones with Arylaldehydes by Air as an Oxidant

“…9 reported a visible-light-induced decarbonylative C−H alkylation of quinoxalin-2(1H)-ones using alkyl aldehydes as alkyl radical precursors. 10 ■…”

“…Herein, we report a visible-light-induced photocatalyst-free strategy for selective C3–H aroylation of quinoxalin-2­(1 H )-ones by employing arylaldehydes as acyl radical precursors with air as the sole oxidant (Scheme D). During the course of our research, Wang and co-workers reported a visible-light-induced decarbonylative C–H alkylation of quinoxalin-2­(1 H )-ones using alkyl aldehydes as alkyl radical precursors …”