Isoindolo[1′,2′:2,3]pyrido[3″,2″:4′,5′] thieno[3′,2′:4,5]-pyrimido[1,6-a]benzimidazol-8(12bH)-one. A novel polycondensed heterocyclic system [10]

Full text of DOI:10.1007/s10593-006-0275-z

Chemistry of Heterocyclic Compounds, Vol. 42, No. 11, 2006
ISOINDOLO[1',2':2,3]PYRIDO[3",2":4',5']THIENO[3',2':4,5]-
PYRIMIDO[1,6-a]BENZIMIDAZOL-8(12bH)-ONE. A NOVEL
POLYCONDENSED HETEROCYCLIC SYSTEM
Mokhamed Abdel-Moneim Makhmud, V. K. Vasilin, and G. D. Krapivin
Keywords: 2-(2,4-diphenyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidin-6-
yl)benzoic
acid,
4,6-diphenylisoindolo[1',2':2,3]pyrido[3'',2'':4',5']thieno[3',2':4,5]pyrimido[1,6-a]-
benzimidazol-8(12bH)-one, intramolecular cyclization.
Previous studies by us [1-3] and others [4-6] have described 3-amino-2-(benzimidazol-
2-yl)thieno[2,3-b]pyridines. It was shown that carboxylic acid anhydrides or orthoesters react readily with
3-amino-2-(benzimidazol-2-yl)thieno[2,3-b]pyridines to give the pentacyclic heteroaromatic systems benzo[4,5]-
imidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidines and with aldehydes to give 5,6-dihydrobenzo-
[4,5]imidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidines.
4'
3'
5'
6'
HOOC
2'
1'
Ph
H
Ph
NH2
6
5
8
N
4
2
9
N
N
3
TsOH
10
Ph
Ph
N
S
N
N
12
S
13
N
1
2
11
1
4
– H2O
PPA
10
9
8
11
12
O
OHC
Ph
Ph
N
7
12b
14
N
6
N
15
16
5
N
Ph
N
S
N
Ph
4
N
1
S
2
N
17
3
3
5
__________________________________________________________________________________________
Kuban State Technological University, Krasnodar 350072, Russia, e-mail: krapivin@kubstu,ru. Translated
from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1742-1744, November, 2006. Original article submitted
July 13, 2006.
0009-3122/06/4208-1101©2006 Springer Science+Business Media, Inc.
1501

It was of interest to study the reaction of 3-amino-2-(benzimidazol-2-yl)thieno[2,3-b]pyridines with
compounds containing aldehyde and carboxyl groups in the same molecule. In particular, in the case of 3-amino-
(benzimidazol-2-yl)-4,6-diphenylthieno[2,3-b]pyridine (1) we have investigated the route of the reaction
with ortho-formylbenzoic acid (2). It was found that, when the reaction was carried out in toluene in the
presence of a catalytic amount of p-toluenesulfonic acid it gave not the 22π-electron heteroaromatic system 3 but
rather the pentacyclic heterocycle 4 which contains conjugated thienopyridine and benzimidazole systems.
Compound 4 is readily dehydrated in polyphosphoric acid to give the novel heterocyclic system 5.
As shown by an AM1 quantum chemical-calculation of the geometry of compound 5 its pentacyclic
framework consists of two planes intersecting at the N(7) – C(12B) at an angle of 120° and this uniquely controls
the optimal configuration of the sp3-hybridized C(12b) atom in the molecule.
The remarkable simplicity of the mass spectra of compounds 4 and 5 was noted. The molecular ion
(I = 5%) of compound 4 sequentially loses a molecule of H2 (aromatization of the pyrimidine ring) and of CO2
(decarboxylation)to give the stable cation radical [M-46] (I = 100%). Compound 5, on the other hand, appears
stable to electron impact and its mass spectrum has only two significant strong peaks for the molecule ion
(I = 84%) and [M-28] ([M-CO]) (I = 100%).
IR spectra were taken on a Specord-M80 instrument as a suspension in vaseline oil and 1H NMR spectra
of a Bruker AM-300 instrument (300 MHz) using DMSO and with TMS as internal standard. Mass spectra were
taken on a Varian CH-6 instrument (EI, 70 eV).
2-(2,4-Diphenyl-5,6-dihydrobenzo[4,5]imidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidin-6-yl)-
benzoic acid (4). Yield 78% with mp 220°C (decomp.) (from DMF). IR spectrum, ν, cm-1: 1710 (COOH).
1H NMR spectrum, δ, ppm (J, Hz): 6.19 (1H, d, JCHNH = 7.5, H-6); 7.02-7.23 (6H, m, 4 meta-H and 2 para-H
phenyl substituents); 7.28-7.35 (4H, m, H-8,9,10,11); 7.37 (1H, d, JCHNH = 7.5, H-5); 7.42-7.62 (4H, m, 4
ortho-H phenyl substituents); 7.68 (1H, m, H-4'); 7.77 (1H, s, H-3); 8.08 (1H, d, J = 8, H-3'); 8.22 (2H, m,
H-5',6'): the protons of the COOH group exchange with solvent water protons and give a broad singlet signal
at 3.3 ppm (in contrast to all of the other spectra in which this signal is very sharp). Mass spectrum, m/z (Irel, %):
550 (5), 548 (15), 504 (100). Found, %: C 74.25; H 3.96; N 10.25. C34H22N4O2S. Calculated, %: C 74.16;
H 4.08; N 10.17.
4,6-Diphenylisoindolo[1',2':2,3]pyrido[3'',2'':4',5']thieno[3',2':4,5]pyrimido[1,6-a]benzimidazol-
1
8(12bH)-one (5). Yield 67% with mp 345 C (decomp.) (from DMF). IR spectrum, ν, cm-1: 1670 (amide). H
NMR spectrum, δ, ppm (J, Hz): 7.15-7.25 (3H, m) and 7.40-7.50 (2H, m) – 4-C6H5 protons: 7.52-7.62 (3H, m)
and 7.65-7.68 (2H, m) – 6-C6H5 protons; 7.28 (2H, m, H-14, H-16); 7.70 (1H, m, H-15); 7.75 (1H, m, H-17);
7.95 (1H, dd, J = 7.7, J' = 7.6, H-10); 8.22 (2H, m, H-11, H-12); 8.63 (1H, d, J' = 7.6, H-9). Mass spectrum, m/z
(Irel, %): 532 (84), 504 (100), 266 (12), 43 (12). Found, %: C 76.58; H 3.85; N 10.48. C34H20N4OS.
Calculated, %: C 76.67; H 3.78; N 10.52.
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