Rose Bengal Catalyzed Coupling of 1, 2 ‐ Dicarbonyls and Phenylene 1, 2 ‐Diamines: Visible‐Light Mediated Synthesis of Quinoxalines

Abstract

A new approach for the formation of quinoxaline derivatives (indolo [2, 3‐b] quinoxaline or 2, 3‐Diphenyl‐quinoxaline derivatives) from several phenylene 1, 2‐diamines and 1, 2‐dicarbonyls has been developed by utilizing Rose Bengal as an organo‐ photoredox catalyst. The reported method focuses on the utilization of visible light photoredox catalysis for the formation of C−N bond in quinoxalines via radical chemistry. The developed strategy is simple, mild, exhibits excellent atom economy and is more viable toward the synthesis of biologically interesting quinoxaline frame work without the involvement of any transition metal or strong oxidant.

Recent applications of Rose Bengal catalysis in N-heterocycles: a short review

“…Jaiswal et al 97 reported a novel protocol for photocatalyzed coupling of phenylene 1,2-diamines and 1,2-dicarbonyls for the synthesis of quinoxaline derivatives (Scheme 15). The protocol is an improvement over the already reported conventional methods, is sustainable and exhibits excellent atom economy.…”

Visible-light-induced organophotocatalytic and singlet oxygen-initiated domino construction of 1,4-dihydropyridines, C-3 functionalized spiro[indoline-3,4′-pyridines] and C-11 functionalized spiro[indeno-[1,2-b]quinoxaline-11,4′-pyridines]

“…On the basis of the aforementioned control experiments and previous studies, 67–74 a mechanism was proposed for the rose bengal catalyzed formation of dimethyl 2′-amino-3′-cyano-2-oxo-1′-phenyl-1′ H -spiro[indoline-3,4′-pyridine]-5′,6′-dicarboxylate 7aa (Scheme 4). First, it starts with the formation of excited state RB* from the ground state of RB upon exposure to visible light irradiation.…”

“…On the basis of the aforementioned control experiments and previous studies, [67][68][69][70][71][72][73][74]…”

Recent advances in the transition-metal-free synthesis of quinoxalines

“…At the same time, Singh and their groups disclosed a visible light promoted organo-photoredox catalyzed chemoselective strategy toward the synthesis of a variety of quinoxalines ( Scheme 6 ). 73 With the help of 20 mol% of Rose Bengal C-3 as the organo-photoredox catalyst, the treatment of 1,2-diamines and 1,2-dicarbonyl compounds including substituted benzil 18 or substituted isatin 13 were found to take place at room temperature to afford the desired quinoxaline products 19 and 20 in moderate to excellent yield respectively. The mechanism to explain this reaction has been covered in Scheme 7 .…”