Photoinduced Enhanced Decomposition of TBHP: A Convenient and Greener Pathway for Aqueous Domino Synthesis of Quinazolinones and Quinoxalines

Abstract

Catalyst-free photoinduced processes in aqueous medium represent significant advancement toward development of green and sustainable pathways in organic synthesis. tert -Butyl hydroperoxide (TBHP) is a widely used oxidant in organic reactions, where the decomposition of TBHP into its radicals by metal catalysts or other reagents is a key factor for efficient catalytic outcome. Herein, we report a simple and environmentally friendly visible light-promoted synthetic pathway for the synthesis of N-heterocyclic moieties, such as quinazolinones and quinoxalines, in the presence of TBHP as an oxidizing agent in aqueous medium that requires no catalysts/photocatalysts. The enhanced rate of decomposition to generate free radicals from TBHP upon visible light irradiation is the driving force for the domino reaction.

Photoinduced, metal- and photosensitizer-free decarboxylative C–H (amino)alkylation of heteroarenes in a sustainable solvent

“…According to the mechanistic study and literature reports, 12 j ,14,22 a plausible mechanism for the photoinduced decarboxylative C–H alkylation is suggested (Scheme 3). First of all, tert -butyl hydroperoxide (TBHP) is decomposed into oxygen-centred radicals through homolysis in the presence of light.…”

“…The tert -butyl hydroperoxide is the optimal precursor of these two oxygen-type radicals, because it is not only green and cheap, but also can be converted into tert -butoxy and hydroxyl radicals just through light-induced homolysis. 14 Inspired by these results and our long-standing research interest on developing green and sustainable reaction systems for the functionalization of heteroarenes, 15 herein, we disclose a photocatalytic procedure for the decarboxylative C–H (amino)alkylation of heteroarenes with carboxylic acids in a green solvent (dimethyl carbonate, DMC) (Scheme 1c). The features such as metal- and photosensitizer-free alkylation and use of DMC as the solvent make the approach meet the demands of green chemistry.…”

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

“…Later, Sarma and co-workers disclosed a visible light-assisted catalyst-free green protocol toward the synthesis of a series of quinoxaline derivatives 56 by employing easily accessible o -phenylenediamine 54 and α-hydroxy ketone 55 as the starting material ( Scheme 16 ). 85 With the help of tert -Butyl hydroperoxide (TBHP) as the oxidizing agent, the corresponding quinoxaline products 56 were obtained in 78–93% yields. The decomposition of TBHP into its radical was predominately promoted by metal or photocatalysts, or other reagents, however in this reaction, the decomposition of TBHP for the radical formation and its acceleration for the completion of the reaction was achieved simply by visible light irradiation and no extra metal- or photocatalyst is required.…”

H2O2-Mediated Synthesis of a Quinazolin-4(3H)-one Scaffold: A Sustainable Approach

“…A transitional metal-free approach is more desirable in terms of yield and reaction conditions, but there are still some limitations in the previous reports to use an extra additive in a stoichiometric amount or limited substrate scope. Therefore, simple, green, and affordable metal-free approaches are more desirable due to their sustainability in real life. , Some of the usual substrates used for the annulation of 2-amino benzamides are benzaldehyde, acetophenone, benzyl alcohol, methanol, methyl arene, CO 2 , isocyanides, etc. (Figure ).…”