Rearrangements of Quinoxalin(on)es for the Synthesis of Benzimidazol(on)es

3-(2-Nitrobenzyl)quinoxalin-2-ones, and pyrido- and 1,2,5-oxadiazolo-fused 2-(2-nitrobenzyl)pyrazin-3-ones in the synthesis of bi-, bis- and condensed heterocyclic systems

“…Recently, quinoxalinone derivatives have been of great importance in the synthesis of benzimidazole systems, [1][2][3] while Mamedov rearrangement 4 is a convenient way to obtain various biheterocycles with a benzimidazole fragment in the composition. Mamedov rearrangement assumes the presence of a functional group in the third position of the quinoxalinone system, in particular, in the synthesis of 2-(indole-2-yl)benzimidazoles, such a group is a benzyl fragment with an amino group in the ortho position.…”

“…8 In this work, we subjected oxazolidinone 3b to hydrolysis in boiling mixture AcOH with H2SO4 (50:1 by volume) and isolated 3-(5-chloro-2-nitrophenyl)pyruvic acid (5), which was further successfully used in the syntheses of quinoxalinones 4b and 4d (Schema 3) under Hinsberg-Körner reaction condition. 1 The acid 5, under the conditions of registration of NMR spectra in DMSO-d6, existed in a mixture of two tautomeric forms A and B (Scheme 3) with a slight predominance of the latter (1:1.2). We have previously shown that derivatives of glycidic and pyruvic acids, oxiranyl ethanone, oxiranylaryl ketone, and quinazoline, containing a 2-nitrophenyl group, under the action of sodium dithionite in a boiling water-dioxane solution, along with the reduction of the nitro group to the amino group, undergo further transformations leading to the formation of various heterocyclic systems depending on the nature of the functional groups in the initial compound (Scheme 4).…”