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

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

“…The proposed mechanism for the formation of regioisomeric (benzimidazol‐2‐yl)oxadiazolo[3,4‐ f ]quinoxalines 3 (Scheme , pathway a ) and 4 (Scheme , pathway b ), as previously shown for similar reactions, involves the formation of spiro‐derivatives A , B and D , E , respectively, which under the reaction conditions are converted to the corresponding anilides C and F as a result of the opening of the C3‐N bond and further intramolecular cyclisation of the latter with the formation of the benzimidazole system with the elimination of water. This mechanism is supported by the isolated spiro‐derivatives analogous to the structures A , B and D , E and 2‐aminoanylides of quinoxaline 3‐aryl‐2‐carboxylic acid similar to the structures C and F in the reactions of quinoxalin‐2‐ones with other binucleophiles 11,12a,b . As can be seen from the data in Table , in all cases, the predominant products are ″C8‐BI″ isomers 3a‐f , which is apparently due to the initial reaction involving less spatially loaded functional groups, namely the amino group at position 5 of 2a and the aroyl carbonyl group at position 3 of the quinoxalinone derivative 1a‐f .…”

“…MRs are convenient methods for the easy synthesis of complex heterocyclic compounds from easily available starting materials. In the past decade, the Mamedov heterocycle rearrangement has been used for the construction of biheterocyclic systems with α , α ′‐diimine bonds 11,12a,b …”

“…There are few papers in the literature on molecules that combine the phenanthroline or bipyridine moieties with the phenazine, quinoxaline, and tetraazanaphthacene units, but none with the benzimidazole moiety. In connection with our interest in the synthesis of fused and biheterocyclic systems, we present here the synthesis and complete characterization of the new polyheterocyclic compounds, namely the first examples of oxa(thia)diazolo[3,4‐ f ]‐ and pyrazino[2,3‐ f ]quinoxalines with the benzimidazole moiety and two new heterocyclic systems—benzo[4′,5′]imidazo[1′,2′:1,2]quinolino[3,4‐ b and 4,3‐ b ][1,2,5]oxadiazolo[3,4‐ f ]quinoxalines.…”

Recent advances in the synthesis of benzimidazol(on)es via rearrangements of quinoxalin(on)es

“…In this case the results of study on a novel rearrangement of 3-aroyl-and alkanoylquinoxalin-2(1H)ones and 2,3-diaminomaleonitrile as a N-nucleophile under the acid catalysis condition are presented. 103 Regardless of the molar ratio of the reagents (1 : 1, 1 : 1.1, 1 : 2; 37a : 121) and reaction time (3, 9 or 17 h) the reaction of 3benzoylquinoxalin-2(1H)-one (3-BQ) 37a with 2,3-diaminomaleonitrile 121 proceeded in the same way with the formation of a $45% yield of the rearrangement product 122a (Scheme 43), whereas 50% of 3-benzoylquinoxalin-2(1H)-one 37a reverted. Diaminomaleonitrile 121 apparently undergoes polymerization.…”

“…It is worthy of note that the products of the reaction of 3aroyl(alkanoyl)quinoxalin-2(1H)-ones 37a-e, g, i, t, u and Nalkyl-3-BQs 37o, v, w with diaminomaleonitrile 121 in DMSO-d 6 exist solely in spiro-cyclic-forms 123a-l, whereas in the crystalline state they exist only as open chain forms 123 0 a-l. 103 Based of the chemistry of quinoxalinones, 105 diaminomaleonitrile, 106 and the above data, it is reasonable to assume that as the rst step the formation of 2-(pyrazin-2-yl) benzimidazoles 122 involves addition of the amino group of diaminomaleonitrile 121 to the C(3) atom of quinoxalin-2(1H)one 37. The next step involves a nucleophilic attack of the second amino group of 121 on the benzoyl carbonyl group to form the spiro-quinoxaline derivative 123.…”