Visible-Light Promoted Regioselective Oxygenation of Quinoxalin-2(1H)-ones Using O₂ as an Oxidant

Abstract

A visible-light-mediated sustainable approach for metal-free oxygenation of quinoxalin-2­(1H)-one by employing Mes-Acr-MeClO4 as a photocatalyst without using any additive or cocatalyst is reported here. O2 served as the eco-friendly and green oxidant source for this conversion. In addition, the protocol exhibited high regioselectivity and tolerance toward a broad spectrum of functional groups to furnish quinoxaline-2,3-diones in good to excellent yields.

Activation of C–Br Bond of CBr4 and CBrCl3 Using 9-Mesityl-10-methylacridinium Perchlorate Photocatalyst

“…Many convenient approaches are available to synthesize acridinium salts that can serve as potential visible-light photocatalysts . Mes-Acr-Me + is a powerful oxidant that activates many chemical systems in the presence of visible light. ,− We have also shown earlier that the N–Cl bond of N -chlorosuccinimide could be activated by the use of the Mes-Acr-MeClO 4 photocatalyst (Figure b) …”

Recent Advances in Carbon‐Nitrogen/Carbon‐Oxygen Bond Formation Under Transition‐Metal‐Free Conditions

“…In same year, the Mal group described a visible-light-mediated and Mes-Acr-MeClO 4 (240)-catalyzed approach for the metal-free oxygenation of quinoxaline-2(1H)-ones (238) with the utilization of O 2 as an eco-friendly and green oxidant (Scheme 50b). [137] Notably, this protocol exhibited good regioselectivity and excellent functional group tolerance, and various quinoxaline-2,3diones (239) could be delivered in 72-98 % yields. It was worth noting that similar transformation also could be achieved with the utilization of NH 4 S 2 O 8 .…”

“…Furthermore, this protocol was applied to gram‐scale reactions (10 mmol scale) and synthesis of drug derivatives (including clofibrate and mecloqualone derivatives), demonstrating promising prospect in practical applications. In same year, the Mal group described a visible‐light‐mediated and Mes‐Acr‐MeClO 4 ( 240 )‐catalyzed approach for the metal‐free oxygenation of quinoxaline‐2(1H)‐ones ( 238 ) with the utilization of O 2 as an eco‐ friendly and green oxidant (Scheme 50b) [137] . Notably, this protocol exhibited good regioselectivity and excellent functional group tolerance, and various quinoxaline‐2,3‐diones ( 239 ) could be delivered in 72–98 % yields.…”

Ionic liquid-catalysed regioselective oxygenation of quinoxalin-2(1H)-ones under visible-light conditions

“…11 In particular, metal complexes of functionalized quinoxalin-2(1 H )-one are known to exhibit antitumor, anticancer, insecticidal, anti-parasitic, antidiabetic and anticonvulsant activities. 12 A few reports on the direct C–H oxygenation of quinoxalin-2(1 H )-ones are available to date, which include; (i) graphitic carbon nitride (g-C 3 N 4 ) 13 and 9-mesityl-10-methylacridinium perchlorate as photocatalysts with blue LEDs, 14 (ii) through ipso -substitution using tert -butyl nitrite, 15 and (iii) oxidative hydroxylation with ammonium persulphate as an oxidant. 16 In addition, direct synthesis of hydroxylated quinoxalin-2(1 H )-ones from o -phenylene diamines and oxalyl chloride or ethyl chloroacetate was also reported.…”

“…Subsequently, the intermediate A engages with superoxide radicals (O 2 ˙ − ), leading to the creation of another intermediate B . 14 Through a 1,2-hydrogen atom transfer (1,2-HAT) process, intermediate B undergoes transformation into a different form of intermediate C . Finally, two species of the intermediate C react and are transformed into the formation of desired product 2a along with molecular oxygen.…”