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A visible-light photoredox functionalization of 3,4-dihydro-quinoxalin-2-ones with pyrazolones using an inexpensive organophotoredox catalyst is described. The reaction uses 9,10-phenanthrenedione as photocatalyst, a very simple and cheap photocatalyst, a HP single Blue LED (455 nm) as visible-light source and oxygen from air as terminal oxidant, obtaining the corresponding acetylated pyrazoles with good yields. The reaction can be extended to other nitrogen heterocycles such as 5-aminopyrazoles with good results.

The functionalization at the C-3 position of 3,4-dihydroquinoxalin-2-one core has been significantly targeted over the last years. Several nucleophilic, electrophilic as well as radical catalytic functionalization of these nitrogen heterocycles have been reported. Usually, the more convenient methods are the direct photoredox functionalizations which use mild, green and sustainable conditions.

An organophotoredox 1,6-radical addition of 3,4-dihidroquinoxalin-2-ones to para-quinone methides catalyzed by Fukuzumi's photocatalyst is described under the irradiation of a HP Single LED (455 nm). The corresponding 1,1-diaryl compounds bearing a dihydroquinoxalin-2-one moiety (20 examples) are obtained with good to excellent yields under mild reaction conditions. Several experiments have been carried out in order to propose a reaction mechanism.

A visible-light photocatalytic radical addition reaction of dihydroquinoxalin-2-ones to trifluoromethyl ketones has been established using Ru(bpy)3Cl2 as photocatalyst, acetonitrile as solvent, and HP Single Blue LED as the source of light. The reaction provides a straightforward approach to the synthesis of dihydroquinoxalin-2-ones bearing a trifluoromethyl-substituted tertiary alcohol moiety in moderate to good yields under mild conditions.

Quinoxalin‐2(1H)‐one is an important class of nitrogen heterocycle in medicinal and pharmaceutical industry, which became a synthetic target in organic chemistry in recent years. This review covers the recent advances in the functionalization of this particular nitrogen heterocycle through photocatalysis.

A direct sp3 C-H amination of cyclic amines (dihydroquinoxalinones and dihydrobenzoxazinones) with dialkyl azo dicarboxylates accelerated by visible-light irradiation under metal and photocatalyst-free conditions is described. This protocol features very mild reaction conditions for the synthesis of aminal quinoxaline and benzoxazine derivatives with good to high yields (up to 99%). These aminal derivatives respresent versatile building blocks for the divergent synthesis of quinoxalin-2-one derivatives.

The asymmetric Mannich reaction is one of the most straightforward methodologies for the enantioselective synthesis of chiral amines. In general, asymmetric Mannich reactions involve the use of imines as electrophiles. However, in recent years, several asymmetric oxidative Mannich reactions have been reported using amines as electrophiles. This review provides an overview of these recent publications, including the different oxidants used and the scope and limitations of the different catalytic systems.

The visible-light photoredox-catalyzed coupling of 1,4-dihydroquinoxalin-2-ones and Michael acceptors was achieved using Ru(bpy)3Cl2 as the photocatalyst and (PhO)2PO2H as an additive. The optimized reaction conditions provide a good yield for the radical conjugate addition products (44 examples) with a wide range of structurally different Michael acceptors. A gram scale reaction using sunlight irradiation is also described. Furthermore, several transformations were carried out with the Giese addition products.

Herein, we described a ligand-free copper-catalyzed aerobic oxidative functionalization of 3,4-dihydroquinoxalin-2(1H)-ones with terminal alkynes using visible-light and oxygen as terminal oxidant to give 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-one, cyclic propargylic amines, in moderate to good yields. Moreover, we demonstrate the versatility of the 3-ethynyl-3,4-dihydroquinoxalin-2(1H)-ones obtained by preparing several 3,4-dihydroquinoxalin-2-one derivatives.

[EN] An asymmetric catalytic reaction of hydroxyindoles with nitroalkenes leading to the Friedel-Crafts alkylation in the carbocyclic ring of indole is presented. The method is based on the activating/directing effects of the hydroxy group situated in the carbocyclic ring of the indole providing nitroalkylated indoles functionalizated at the C-4, C-5, and C-7 positions with high yield, regio-, and enantioselectivity. The optically enriched nitroalkanes were transformed efficiently in optically enriched 2-amino-1,1-diarylalkanes bearing a carbocyclic ring substituted indole., Financial support from the MINECO (Gobierno de Espana; CTQ2017-84900-P) is gratefully acknowledged. C.V. thanks MINECO for a JdC contract. J.R.-B. thanks the Ministry of Education for a Collaboration grant. Access to NMR, MS, and X-ray facilities from the Servei Central de Suport a la Investigacio Experimental (SCSIE)-UV is also acknowledged

[EN] An enantioselective photooxidative Mannich reaction of dihydroquinoxalinones with ketones by the merger of organophotoredox and asymmetric organocatalysis is described. This protocol features very mild reaction conditions using simple and cheap catalysts (Eosin Y and (S)-Proline) for the synthesis of chiral quinoxaline derivatives with good to high yields (up to 94%) and excellent enantioselectivities (up to 99% ee)., Financial support from the Agencia Estatal de Investigation (AEI, Spanish Government) and Fondo Europeo de Desarrollo Regional (FEDER, European Union) (CTQ2017-84900-P) is acknowledged. J.R.-B. thanks the Ministerio de Ciencia, Innovacion y Universidades for an FPU predoctoral contract, and C.V. thanks the Agencia Estatal de Investigacion (AEI, Spanish Government) for an RyC contract (RYC-2016-20187).

A visible-light photoredox functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones through a Friedel-Crafts reaction with indoles using an inexpensive organophotoredox catalyst is described. The reaction uses a dual catalytic system that is formed by a photocatalyst simple and cheap, 9,10-phenanthrenedione, and a Lewis acid, Zn(OTf)2. 5W white LEDs are used as visible-light source and oxygen from air as a terminal oxidant, obtaining the corresponding products with good yields. The reaction can be extended to other electron-rich arenes. Our methodology represents one of the most valuable and sustainable approach for the functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones, as compared to the reported procedures. Furthermore, several transformations were carried out, such as the synthesis of the natural product cephalandole A and a tryptophol derivative.