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

Full text of DOI:10.1007/s10593-008-0088-3

Chemistry of Heterocyclic Compounds, Vol. 44, No. 5, 2008
SYNTHESIS OF 11-METHYL-7,9-DIPHENYL-6H,11H-
AZEPINO[2,1-b]-5-BENZIMIDAZOLIUM BROMIDE
V. A. Kovtunenko, L. M. Potikha, A. R. Turelyk, and A. V. Turov
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-
1
H-benzimidazole (1) leads to 11-methyl-7,9-diphenyl-6H,11H-azepino[2,1-b]-5-benzimidazolium bromide (2).
1
13
1
13
We took NOESY and heteronuclear H C HMQC and HMBC correlation spectra in addition to H and
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
1
3
protons are close to each other in space. The alternation of the chemical shifts of the 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.
Ph
_
Br
Ph
4
N
N
+
BrCH2
COPh
N
N
Ph
Me
1
11
1
Me
Me
2
1
27.5
1
'
7.92
1
38.0
1
41.4
7.27
5.47
7.94
8.31
45.0
128.1
128.5
1
13.4
+
153.4
N
139.5
1
30.0
1''
110.6
148.0
134.3
7.79
N
114.2
8.04
33.1 CH3
.19
4
1
13
The IR spectra were taken on a Pye Unicam SP3-300 spectrometer. The H and C NMR spectra were
taken on a Varian Mercury 400 spectrometer at 400 and 100 MHz, respectively, in DMSO-d with TMS as the
6
internal standard. The mass spectrum was taken using high-pressure liquid chromatography on an
AGILENT/100-Series mass spectrometer and chemical ionization with acetonitrile and 0.05% formic acid.
_
_________________________________________________________________________________________
Taras Shevchenko Kiev National University, Kiev 01033, Ukraine; e-mail: potikha_l@mail.ru.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 791-793, May, 2008. Original article
submitted January 28, 2008.
6
32
0009-3122/08/4405-0632©2008 Springer Science+Business Media, Inc.

1
1
1
13
TABLE 1. H H and H C Correlations for Compound 2
1
13
Н signal,
δ, ppm
С cross peaks position
NOESY
HMQC
113.4
HMBC
8
8
7
7
7
7
7
7
5
4
.31
.04
.94
.79
.69
.57
.50
.27
.47
.19
134.3, 127.7
7.69, 5.47
114.2
128.9, 127.5
110.6
127.5
131.5
130.0
128.1
45.0
130.6, 127.5
7.69, 4.19
7.79, 7.57, 7.50, 7.27
7.94
153.4, 141.4, 131.5, 130.6, 128.1
153.4, 139.5, 128.1
130.0, 113.4, 114.2
139.5
8.31, 8.04
7.94, 7.50
7.54
138.0, 130.0
141.4, 139.5, 138.0, 110.6, 45.0
148.0, 141.4, 138.0, 130.0, 128.1
148.0, 134.3
7.94
8.31, 7.94
8.04, 7.79
33.1
1
1-Methyl-7,9-diphenyl-6H,11H-azepino[2,1-b]-5-benzimidazolium Bromide (2). A mixture of
γ-bromodipnone (1.0 g, 3.32 mmol) and 1,2-dimethyl-1H-benzimidazole (0.49 g, 3.32 mmol) was fused on an
oil bath at 110°C during 30 min. The melt was dissolved upon heating in 2.5 ml morpholine. The solution was
cooled and 50 ml water was added. The precipitate formed was filtered off, dried, and triturated with tert-butyl
methyl ether (10 ml). The yellow crystalline precipitate was filtered off and recrystallized from 2-propanol to
-
1
give compound 2 (0.36 g, 25%); mp 275-277°C (2-propanol). IR spectrum (KBr), ν, cm : 3040, 1575 (C=N),
1
1
470, 760, 690. H NMR spectrum, δ, ppm (J, Hz): 8.31 (1H, m, H-4); 8.04 (1H, m, H-1); 7.94-7.90 (4H, m,
H-2', H-6', H-2", H-6"); 7.79 (1H, s, H-10); 7.69 (2H, m, H-2, H-3); 7.57 (3H, m, H-3"–H-5"); 7.51-7.45 (3H,
1
3
m, H-3'–H-5'); 7.27 (1H, s, H-8); 5.47 (2H, s, H-6); 4.19 (3H, s, CH ). C NMR spectrum, δ, ppm: 153.4 (C-9);
3
1
48.0 (C-10a); 141.4 (C-7); 139.5 (C-1"); 138.0 (C-1'); 134.3 (C-11a); 131.5 (C-4"); 130.6 (C-4'); 130.0 (C-3',
C-5', C-5', C-5", C-4a); 128.9 (C-2", C-6"); 128.0 (C-8); 127.7 (C-2); 127.5 (C-2', C-6', C-3); 114.2 (C-1); 113.4
+
(
C-4); 110.6 (C-10); 45.0 (C-6); 33.1 (CH ). Mass spectrum, m/z (I , %): 349.5 [M-Br] (100). Found. %: Br
3
rel
1
8.60; N 6.55. C H BrN . Calculated, %: Br 18.61; N 6.52.
2
5
21
2
6
33