Visible‐Light Photoredox Catalyzed C−N Coupling of Quinoxaline‐2(1H)‐ones with Azoles without External Photosensitizer

Abstract

A visible-light photoredox catalyzed CÀ N coupling of quinoxaline-2(1H)-ones with azoles in the absence of external photosensitizer has been developed. The protocol employs commercially available pyrazoles and triazoles as amination reagents and shows wide substrate scope, providing the corresponding C3-position amination products in good yields and high regioselectivity under ambient conditions. Investigations indicate that the starting materials and products can act as photosensitizers avoiding use of additional photocatalyst in an autocatalytic manner. In addition, 1 O 2 coexists with O 2 * À from molecular oxygen (3 O 2) via an energy transfer (ET) and single electron transfer (SET) process during the reaction.

Metal‐Free Direct Oxidative C−N Bond Coupling of Quinoxalin‐2(1H)‐ones with Azoles under Mild Conditions

“…These data are similar to the reported one. [16] 1-Ethyl-3-(1H-pyrazol-1-yl)quinoxalin-2(1H)-one (3 l)…”

“…These data are similar to the reported one. [16] 1 40, 143.31, 142.60, 133.19, 131.77, 131.55, 130.43, 130.00, 124.37, 113.67, 108.19, 44.67, 20.66, 11.35…”

“…These data are similar to the reported one. [16] 85, 142.49, 141.66, 132.31, 132.26, 131.80, 131.06, 130.95, 130.54, 129.27, 129.11, 128.04, 126.70, 126.68, 125.52, 125.23, 124.49, 123.66, 123.48, 113.48, 107.35, 45.82…”

“…[15] Very recently, Li and co-workers reported a visiblelight-promoted C-N coupling of quinoxaline-2(1H)-ones with azoles (Scheme 1d). [16] However, long reaction time (20 h) were required and NH unprotected quinoxalin-2(1H)-ones were not tolerated for this reaction. As a continuation of our previous work, herein, we report a simple, efficient and convenient method for the direct amination of quinoxalinones at their C3 positions using PhI(OTFA) 2 , which mediates oxidative CÀ N bond coupling between the quinoxalin-2(1H)-one and azole.…”

“…We recently reported the NBS or NIS mediated direct N ‐sulfonylation of azoles with sodium sulfinates [15] . Very recently, Li and co‐workers reported a visible‐light‐promoted C‐ N coupling of quinoxaline‐2(1 H )‐ones with azoles (Scheme 1d) [16] . However, long reaction time (20 h) were required and N H unprotected quinoxalin‐2(1H)‐ones were not tolerated for this reaction.…”