Photoredox Catalyst Free, Visible Light‐Promoted C3−H Acylation of Quinoxalin‐2(1 H )‐ones in Water

Oxidative trimerization of indoles via water-assisted visible-light photoredox catalysis and the study of their anti-cancer activities

Incorporation of water has been revealed to successfully facilitate visible-light photoredox catalysis of indole leading to increased production of C2-quaternary indolinone. The water-promoted photoreaction of indole under catalyst-free conditions by a household compact fluorescence light was also demonstrated. The antiproliferative activity of the synthesized indolinones was evaluated against three human cancer cell lines.

BI-OAc-Accelerated C3-H Alkylation of Quinoxalin-2(1H)-ones under Visible-Light Irradiation

An efficient, photoredox-catalyst-free radical alkylation of quinoxalin-2(1H)-ones has been described. This reaction utilizes 4-alkyl-1,4-dihydropyridines (R-DHPs) as alkyl radical precursors and acetoxybenziodoxole (BI-OAc) as an electron acceptor to undergo single-electron transfer with photoexcited R-DHPs. The benign conditions allow for good compatibility in the scope of both quinoxalin-2(1H)-ones and R-DHPs. The synthetic value of the protocol was also demonstrated by the successful functionalization of natural products and drug-based complex molecules.

Selective photoredox decarboxylation of α-ketoacids to allylic ketones and 1,4-dicarbonyl compounds dependent on cobaloxime catalysis

The selective synthesis of allylic ketones and 1,4-dicarbonyl compounds by photoredox/cobaloxime co-catalysis and photoredox catalysis, respectively, is described herein.

Metal-free C3–H acylation of quinoxalin-2(1H)-ones with α-oxo-carboxylic acids

Direct C3–H acylation of quinoxalin-2(1H)-ones with α-oxocarboxylic acids under thermo conditions promoted by PIDA has been achieved in a moderate to good yield in a very fast manner.

tert-Butylhydroperoxide (TBHP) mediated oxidative cross-dehydrogenative coupling of quinoxalin-2(1H)-ones with 4-hydroxycoumarins, 4-hydroxy-6-methyl-2-pyrone and 2-hydroxy-1,4-naphthoquinone under metal-free conditions

We report an efficient and atom-economical method of C-3 functionalization of quinoxalin-2(1H)-ones with 4-hydroxycoumarins, 4-hydroxy-6-methyl-2-pyrone, and 2-hydroxy-1,4-naphthoquinone via the free radical cross-coupling pathway under metal-free conditions. tert-Butylhydroperoxide (TBHP) smoothly promotes the reaction furnishing the cross-dehydrogenative coupling (CDC) products in very good to excellent yields. The protocol neither uses any toxic reagents nor metal catalysts to carry out the reaction, and all the products have been obtained without column chromatography purification. Different radical trapping experiments with 2,2,6,6-tetramethylpiperidine-1-oxyl, butylated hydroxytoluene, and diphenyl ethylene confirm the involvement of radicals.