Sulfur‐Catalyzed Oxidative Condensation of Aryl Alkyl Ketones with o‐Phenylenediamines: Access to Quinoxalines

Abstract

While elemental sulfur has been largely used as oxidant or sulfurating agent, its role as a catalyst has not been developed. We report here its catalytic activity in the oxidative condensation of ophenylenediamines with acetophenones in DMSO to provide quinoxalines. The method was also extended to α-tetralones, propiophenones (R = Me) as well as higher homologues (R = Et, n-Pr) in place of acetophenones, leading to a wide range of naphthoquinoxalines and 3-substituted 2-arylquinoxalines.

Base-catalyzed multicomponent access to quinoxalin-2-thiones from o-phenylenediamines, aryl ketones and sulfur

“…1). 13 Interestingly, we found also that when a base was used as a catalyst instead of an acid, the formation of quinoxalines 3′ was significantly inhibited and sulfurated quinoxalines 3aa was obtained as the major product. Our first attempt performed under catalyst-free conditions using DMSO as an oxidant at 80 °C led to quinoxaline 3aa as a yellow solid.…”

Fe/S cluster catalyzed cascade cyclization of N,S-1,6-enynes for the synthesis of thieno[3,4-b]indoles

“…6 S atom has a higher polarization than other heteroatoms (N, O, etc . ), which can be used as a reductant, 7 oxidant, 8 catalyst (activator), 9 or a building block in a reaction. 10…”

Sodium sulfide-promoted regiodefined redox condensation of o-nitroanilines with aryl ketones to benzo[a]phenazines and quinoxalines

“…Classical approaches toward benzo[ a ]phenazines 3 have been achieved so far mainly via isohypsic condensation of unstable and air-sensitive o -phenylenediamines 4 with diketones 5 5 or oxidative coupling with α-tetralones 2 . 6 Additionally, it should be noted that o -phenylenediamines 4 were generally obtained from reductions of parent o -nitroanilines 1 . This analysis led us to investigate a direct redox condensation of o -nitroanilines 1 with α-tetralones 2 to benzo[ a ]phenazines 3 .…”