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

Moisture-resistant radical anions of quinoxalin-2(1H)-ones in aerial dioxygen activation

This study demonstrates the successful formation of a radical anion intermediate in a moist atmosphere, facilitating chemical reactions by activating aerial dioxygen through a single electron transfer (SET) mechanism. Derived from deprotonating quinoxaline-2(1H)-one with KOtBu, it shows potential in oxygenation chemistry. Validation comes from radical scavenging and EPR experiments.

Visible-Light-Promoted Selenylation/Cyclization of o-Alkynyl Benzylazides/o-Propargyl Arylazides: Synthesis of Seleno-Substituted Isoquinolines and Quinolines

A simple and efficient visible-light-promoted selenylation/cyclization of o-alkynyl benzylazides/o-propargyl arylazides have been realized for the practical synthesis of seleno-substituted isoquinolines and quinolines. This strategy provides the synthesis of valuable seleno-substituted isoquinoline and quinoline derivatives via the construction of one C(sp2)-Se bond and one C-N bond within one process.

Atom Transfer Radical Addition Reactions of Quinoxalin-2(1H)-ones with CBr4 and Styrenes Using Mes-Acr-MeClO4 Photocatalyst

The atom transfer radical addition (ATRA) reaction is defined as a method for introducing halogenated compounds into alkenes via a radical mechanism. In this study, we present an ATRA approach for achieving regioselective functionalization of quinoxalin-2(1H)-ones by activating C-Br bonds of CBr4 and subsequent trihaloalkyl-carbofunctionalization of styrenes employing the 9-mesityl-10-methylacridinium perchlorate (Fukuzumi) photocatalyst under 3W blue LED (450-470 nm) irradiation. This three-component radical cascade process demonstrates remarkable efficiency in the synthesis of 1-methyl-3-(3,3,3-tribromo-1-(4-chlorophenyl)propyl)quinoxalin-2(1H)-one derivatives.

Direct Access to Strained Fused Dihalo-Aziridino Quinoxalinones via C3-Alkylation Followed by Tandem Cyclization

Quinoxalinones are a privileged class of compounds, and their structural framework is found in many bioactive compounds, natural compounds, and pharmaceuticals. Quinoxalinone is a promising scaffold for different types of functionalization, and the slight modification of the quinoxalinone skeleton is known to offer a wide range of compounds for drug discovery. Owing to the importance of the quinoxalinone scaffold, we have developed a base-mediated protocol for the C3-alkylation of quinoxalinone followed by tandem cyclization to access novel types of strenuous and fused dihalo-aziridino-quinoxalinone heterocycles via the construction of C-C and C-N bonds. The protocol proved to be simple and practical to access desired fused quinoxalinone heterocycles in excellent yields (up to 98% yield). As an application, the highly functionalized fused dihalo-aziridino-quinoxalinone molecule has been further utilized for mono-dehalogenation under visible light irradiation and selective amide reduction. Moreover, the protocol has also been demonstrated on a gram scale.

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

Herein, we report the activation of the C-Br bond of CBrX₃ (X = Cl, Br) using 9-mesityl-10-methylacridinium perchlorate as a visible-light (12W blue LED, 450-455 nm) photocatalyst for the synthesis of gem-dihaloenones from terminal alkynes. An electron transfer from CBrX₃ to Mes-Acr-MeClO₄ led to the formation of ^•+CBrX₃ which subsequently resulted in the intermediate ⁺CX₃. Next, C-C cross-coupling of ⁺CX₃ with terminal alkynes was the key path to obtain the gem-dihaloenones. Radical trapping experiments with TEMPO, BHT, and Stern-Volmer quenching studies helped to understand that the reaction proceeded via the SET mechanism.