Acid-catalyzed rearrangement of 3-(β-2-aminostyryl)quinoxalin-2(1H)ones—a new and efficient method for the synthesis of 2-benzimidazol-2-ylquinolines

ANRORC type rearrangement/intermolecular cyclocondensation cascade of 5,6-dicyano-3-(2-oxo-2-ethyl)pyrazin-2(1H)-ones with hydrazine hydrate for the synthesis of 2-(pyrazol-3-yl)imidazo[4,5-d]pyridazines

A novel H2SO4-catalyzed ANRORC-type rearrangement of pyrazinones to imidazoles proceeding through pyridazino[d]annulation with simultaneous introduction of a pyrazole ring at position 2 of the imidazole system has been developed, which offers efficient and expedited access to new biheterocyclic systems - 2-(pyrazol-3-ul)imidazoles and 2-(pyrazol-3-yl)imidazo[4,5-d]pyridazines. Diverse bi-N-heterocyclic systems with the imidazo[4,5-d]pyridazine-4,7-diamine moiety could be obtained in excellent yield when 5,6-dicyano-3-(2-oxo-2-ethyl)pyrazin-2(1H)-ones interact with hydrazines via the selective spiro-formation in a tandem ring-opening/ring-closing process, which allowed the simultaneous construction of five new C-N bonds. This new method is compatible with an array of functional groups, proceeds under mild reaction conditions with the involvement of commercially available reagents. Control experiments and DFT studies elucidate the detailed reaction mechanism.

Three metal(II) complexes constructed using the 2-(1H-benzo[d]imidazol-2-yl)quinoline ligand

2-(1H-benzo[d]imidazol-2-yl)quinoline (BQ) as ligand and three coordination compounds of formula {Zn(BQ)Cl2} (1), {Pb(BQ)Cl2} n (2) and {[Cu(BQ)2(OC(O)CH3)]OC(O)CH3 · CH3COOH} (3) have been synthesized and fully characterized. The complexes crystallize in triclinic space group P 1 ‾ $P‾{1}$ . In complexes 1 and 2, the coordination geometry is a distorted tetrahedral environment around the zinc center and a distorted sixfold coordination geometry around the lead center, respectively. In complex 3 the central Cu(II) center is in a trigonal bipyramidal coordination geometry. The Cu(II) ion is surrounded by two bidentate 2-(2′-quinolyl)benzimidazole (BQ) ligands and one coordinated acetate molecule. One further acetate anion associated by a strong hydrogen bond with a molecule of acetic acid balances the charge of the compound.

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

The review describes all the quinoxaline-benzimidazole rearrangements as a whole and the new quinoxalinone-benzimidazol(on)e rearrangements in particular when exposed to nucleophilic rearrangements which can be used for the synthesis of various biheterocyclic motifs.