Fused polycyclic nitrogen-containing heterocycles

The condensation of methyl phenylchloropyruvate with 1-phenyl-3-(2-pyridyl)thiourea and its 3-and 4-picolyl homologs affords the corresponding 4-hydroxythiazolidines, which react with o-phenylenediamine to give one of two possible thiazolo[3,4-a]quinoxalines containing the pyridyl-or picolylimine substituents at position 1. 3a-Hydroxy-3-phenylimino-1-(2-pyridyl)thiazolo[3,4-a]quinoxalin-4-(3H,5H)-one, which is a covalent hydrate of the final product, was isolated as an intermediate in this reaction.     

Polyfused nitrogen-containing heterocycles 23. Methyl 4-hydroxy-3-phenyl-5-phenyl(alkyl)-2-phenyliminoselenazolidine-4-carboxylates and selenazolo[3,4-a]quinoxalin-4(5H)-one derivatives on their basis

Russian Chemical Bulletin - Condensation of methyl phenyl(alkyl)halopyrotartrates with N,N′-diphenylselenourea leads to the formation of methyl...     

A novel one-step efficient method for the synthesis of tetrahydroindoles from 1-(1-pyrrolidino)cyclohexene and chloropyruvates

A highly efficient, one-step, versatile method for the synthesis of tetrahydroindoles has been developed on the basis of new ring formation in the reactions of 1-(1-pyrrolidino)cyclohexene with chloropyruvates.     

Fused polycyclic nitrogen-containing heterocycles 20. Thiazolo[3,4-<Emphasis Type="Italic">a</Emphasis>]quinoxalines from 4-hydroxy-2-phenyliminothiazolidines and C-substituted 1,2-phenylenediamines

The condensation of 4-hydroxy-3,5-diphenyl-2-phenyliminothiazolidine with 4,5-dimethyl-1,2-phenylenediamine affords 7,8-dimethyl-3-phenyl-1-phenyliminothiazolo[3,4-a]quinox-alin-4(5 H)- one; the condensation with 1,2-phenylenediamines containing different substituents at positions 4 and 5 gives both theoretically possible isomeric thiazolo[3,4-a]quinoxalines, which differ in the distribution of these substituents between positions 7 and 8 in the benzene ring of the quinoxaline system. 3a-Hydroxy-7,8-dimethyl-3-phenyl-l-phenylimino-3,3a-di-hydrothiazolo[3,4-a]quinoxalin4(5 H)- one was isolated and characterized as the intermediate of the reaction giving rise to thiazolo[3,4-a]quinoxaline from 4,5-dimethyl-1,2-phenylene-diamine. This intermediate is a covalent hydrate of the final product.     

One-pot synthesis of thiazolo[3,4-a]quinoxalines and the related heterocyclic systems using 4-hydroxy-4-alkoxycarbonyl-3,5-diaryl-2-aryliminothia(selena)zolidines as versatile reagents

An efficient and versatile one-step method for the synthesis of thiazolo[3,4-a]quinoxalines and related new heterocyclic systems have been developed on the basis of a new strategy for the construction of the pyrazine ring system. The key step of the process involves the cascade annulation of the iminothiazolopyrazine system to benzene in the reaction of 4-hydroxy-3,5-diaryl-2-phenyliminothiazolidines with 1,2-diaminobenzenes. The use of selenium analogues instead of thiazolidine derivatives in this reaction, leads to selenazolo[3,4-a]quinoxalines and the use of aza analogues instead of 1,2-diaminobenzenes gives aza analogues of thiazolo[3,4-a]quinoxalines.     

Three Questionable Cases in the Chemistry of Quinoxalines and Benzodiazepines in the Way of the Syntheses of Benzimidazoles

The reaction of 3‐ethoxycarbonylmethylene‐3,4‐dihydroquinoxalin‐2(1H)‐one 5 with the Vilsmeier reagent, the treatment of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one hydrochloride 7 with 10% sodium hydroxide and 3‐benzimidazoylquinoxaline‐2(1H)‐one 3 with both 1,2‐phenylenediamine dihydrochloride, and the reactions of 1,2‐phenylenediamine have been reinvestigated, and the structures of these reaction products have been revised. The aforementioned reactions have been shown to proceed with the formation of 1‐N,N‐dimethylaminomethylene‐2‐oxo‐1,2‐dihydrofuro[2,3‐b]quinoxaline 10 in the first case, the formation of 3‐[2‐(benzimidazol‐2‐on‐1‐yl)vinyl]‐1H‐quinoxalin‐2‐one 12 in the second case, and the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 in the third case and not the formation of 3‐(N,N‐dimethylaminocarbonyl)furo[2,3‐b]quinoxaline hydrochloride 6 , the free base of 3‐(3,4‐dihydroquinoxalin‐2(1H)‐on‐3‐yl)‐1,2‐dihydro‐1,5‐benzodiazepin‐2(1H)‐one 7 , that is, compound 11 and benzodiazepine derivative 4 , as has been described earlier. In the third case, the formation of 2,3‐bis‐(1H‐benzimidazol‐2‐yl)quinoxaline 17 occurs according to the novel quinoxalin‐2(1H)‐one benzimidazole rearrangement discovered by us. The potential mechanisms for the investigated reactions are discussed.     

An efficient metal-free synthesis of 2-(pyrazin-2-yl)benzimidazoles from quinoxalinones and diaminomaleonitrile via a novel rearrangement

A simple and highly efficient metal-free method for the synthesis of 2-(pyrazin-2-yl)benzimidazoles has been developed on the basis of the novel ring contraction of 3-aroyl- and 3-alkanoylquinoxalin-2-ones with diaminomaleonitrile.     

A reaction for the synthesis of benzimidazoles and 1H-imidazo[4,5-b]pyridines via a novel rearrangement of quinoxalinones and their aza-analogues when exposed to 1,2-arylenediamines

An efficient and one-step versatile method for the synthesis of benzimidazoles and 1H-imidazo[4,5-b]pyridines from quinoxalinones and their aza-analogues have been developed on the basis of the novel ring contractions of 3-aroyl-quinoxalinones and their aza-analogues with 1,2-arylenediamines.     

Environmentally friendly and efficient method for the synthesis of the new α,α′-diimine ligands with benzimidazole moiety

The new α,α′-diimine ligands with benzimidazole moiety were synthesized based on the rearrangement of 3-aroylquinoxalin-2(1H)-ones when exposed to 4,5-diamino-2,1,3-benzoxadiazole, 4,5-diamino-2,1,3-benzothiadiazole and 5,6-diaminoquinoxaline. Among them, we report the first examples of the new heterocyclic system namely benzo[4′,5′]imidazo[1′,2′:1,2]quinolino[3,4-b and 4,3-b][1,2,5]oxadiazolo[3,4-f]quinoxalines, which exhibits an interesting electrochemical behavior. All compounds were fully characterized by IR, ¹H and ¹³C NMR spectroscopies, and mass spectrometry.