Keywords: γ-bromodypnone, imidazo[1,2-a]pyridine, pyrido[1,2-a]benzimidazole, cyclization of azolium ylides.The imidazo[1,2-a]pyridine system has been studied very actively recently, in connection with the introduction into the practice of medicine of preparations of the type of zolpidem [3], fazadinium [4], and others. The basic method for the construction of imidazo[1,2-a]pyridine system consists of the construction of the imidazole part of the bicycle. An alternative possibility is annelation, when the final closing of the imidazo[1,2-a]pyridine or pyrido[1,2-a]imidazole system is carried out during the construction of the pyridine ring, has been insufficiently studied [5][6][7].In the present work a simple variant of the construction of the pyridine ring on the imidazole or benzimidazole structure is proposed, based on the "inversion" of the A. E. Chichibabin reaction [8]. The formation of imidazo[1,2-a]pyridines according to Chichibabin consists of the interaction of α-halo ketones with 2-aminopyridine, which proceeds via the initial formation of a quaternary salt, its deprotonation, and intramolecular attack on the carbonyl group by a nucleophile. The intermediate carbinolamine is readily converted into an imidazo[1,2-a]pyridine by dehydration, but it may be isolated in pure form [9]. Our proposed inverted variant consists, in the first place, in replacing the α-halo ketones by their vinylogs (in this work we refer to γ-bromodypnone) and secondly, in using imidazole or benzimidazole without substitutions in position 2. The sequence of conversions in these reactions is identical to the stages of the Chichibabin reaction.

No abstract

Keywords: azepino[2,1-b]benzimidazole, γ-bromodipnone, 1,2-dimethyl-1H-benzimidazole.We have found that fusing 4-bromo-1,3-diphenyl-2-buten-1-one (γ-bromodipnone) with 1,2-dimethyl-1H-benzimidazole (1) leads to 11-methyl-7,9-diphenyl-6H,11H-azepino[2,1-b]-5-benzimidazolium bromide (2). We took NOESY and heteronuclear 1 H 13 C HMQC and HMBC correlation spectra in addition to 1 H and 13 C NMR spectra to prove the structure of 2. The experimental results are given in Table 1 and the signal assignments are shown in the scheme. The arrows show the HMBC serving as the basis of the assignments. This procedure permitted us to confirm the structure of the carbon skeleton of this molecule and determine which protons are close to each other in space. The alternation of the chemical shifts of the 13 C atoms within the seven-membered ring along the chain of atoms (from 110 to 150 ppm) suggests that the positive charge in 2 is considerably delocalized over the seven-membered ring.There is no reliable information in the literature on the quasiaromatic azepino[2,1-b]benzimidazole system. BrCH 2

Keywords: azepino[1,2-a]benzimidazole, J-bromodypnone, imidazo[1,2-a]azepine, cyclization.Amongst azepino[1,2-a]benzimidazole and imidazo[1,2-a]azepine condensed systems there are found highly active compounds which are proposed as antagonists of choline, histamine, and dopamine receptors [1][2][3][4], for the regulation of sodium or potassium ion transport through a cell membrane [3,5], and as antitumor agents [2]. However, the studied compounds structure in this series vary mainly in the azole part of the bicycle but the azepine part unsaturation degree and the effect of substituents in azepine ring on the compound properties has been little studied.Continuing our investigation of the heterocyclization of 4-bromo-1,3-diphenyl-2-buten-1-one (J-bromodypnone, 1a, Scheme 1) [6,7] we propose a method for the synthesis of 7,9-diarylazepino[1,2-a]benzimidazoles (2) and 6,8-diarylimidazo[1,2-a]azepines 3 and 4. Aiming the biological potential evaluation of compounds in this series we have calculated the spectrum of their biological activity using the PASS program (Prediction of Activity Spectra for Substances) [8][9][10]. Amongst a broad spectrum of predicted features the most widespread are their potential as ligands (substrates) of enzyme CYP2D16 (polypeptide 16, gene family 2, subfamily D of cytochrome P450) and as antagonists of the subtype A receptor of J-aminobutyric acid (GABA).Higher activity (Pa > 80%) is predicted for compounds with a hydrogenated azepine fragment. For these, a high likelihood of the appearance of dopamine receptor agonist and antidepressant properties should be noted.

via base initiated cyclization of corresponding quaternary azolium salts