Synthesis of 11-methyl-7,9-diphenyl-6H,11H-azepino[2,1-b]-5-benzimidazolium bromide

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

Synthesis of azepino[1,2-a]benzimidazoles and imidazo[1,2-a]azepines

“…In the remaining cases, the reaction of the J-bromodypnones 1a,b,d with 2-methylimidazole derivatives gave mixtures with salts 5b,e-i content not less than 70% (from 1 H NMR spectroscopic data). The reaction of J-bromodypnone 1c with 1,2-dimethyl-1H-imidazole also gives a quaternary imidazolium salt but its structure proved different and corresponded to the 3-[2,4-bis(4-bromophenyl)-4-oxo-1-butenyl]-1,2-dimethyl-1H-imidazol-3-ium bromide (6).…”

“…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].…”

“…Although this has been extensively developed in recent years [11][12][13][14][15], the route to building these systems via a [4+3] type cyclization has only been employed in few cases [15][16][17]. We have previously found that melting the J-bromodypnone 1a with 1,2-dimethyl-1H-benzimidazole at 110ºC and further work up of the reaction product with base (morpholine) gives the 5-methyl-7,9-diphenyl-5,10-dihydroazepino-[1,2-a]benzimidazol-11-ium bromide (2a) [6]. Under the same conditions the J-bromodypnone derivatives 1b-d also form the azepino[1,2-a]benzimidazolium bromides 2b-d (Table 1).…”