Synthesis of some fused heterocycles based on thieno[2,3-B]pyridine and their antimicrobial activity

Article abstract of DOI:10.1007/s10593-010-0508-z

The reaction of 3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carbonitrile with ethylenediamine in the presence of a catalytic amount of carbon disulfide afforded 2-(4,5-dihydro-1H-imidazol-2-yl)-4,6-dimethylthieno-[2,3-b]pyridine-3- amine while its reaction with triethyl orthoformate followed by the reaction with hydrazine hydrate gave 4-imino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d] pyrimidine-3(4H)-amine. These two derivatives underwent cyclocondensation reactions with commercially available reactants to afford new heterocycles containing the thieno[2,3-b]pyridine moiety. Some of the synthesized derivatives were tested for antimicrobial and antifungal activity. 2010 Springer Science+Business Media, Inc.

Full text of DOI:10.1007/s10593-010-0508-z

Chemistry of Heterocyclic Compounds, Vol. 46, No. 3, 2010
SYNTHESIS OF SOME FUSED HETEROCYCLES
BASED ON THIENO[2,3-b]PYRIDINE AND THEIR
ANTIMICROBIAL ACTIVITY
F. A. El-Essawy1*, M. A. Hawatta1, A. E.-S. Abdel-Megied1,
and D. A. El-Sherbeny1
The reaction of 3-amino-4,6-dimethylthieno[2,3-b]pyridine-2-carbonitrile with ethylenediamine in the presence of
a
catalytic amount of carbon disulfide afforded 2-(4,5-dihydro-1H-imidazol-2-yl)-4,6-dimethylthieno-
[2,3-b]pyridine-3-amine while its reaction with triethyl orthoformate followed by the reaction with hydrazine
hydrate gave 4-imino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine-3(4H)-amine. These two derivatives
underwent cyclocondensation reactions with commercially available reactants to afford new heterocycles
containing the thieno[2,3-b]pyridine moiety. Some of the synthesized derivatives were tested for antimicrobial and
antifungal activity.
Keywords: imidazole, pyridothienopyrimidine, 1,2,3,4-tetrazoles, 1,2,4-triazoles, antibacterial, antifungal
activity, cyclocondensation.
The biological activities of condensed pyrimidines as sedatives, antibacterials, and antimalarials are well
documented [1, 2]. Compounds containing a fused pyrimidine ring have attracted attention due to their wide
range of biological activities, particularly in cancer and virus research [3]. Among these heterocycles the
thienopyrimidine class is also of interest because some derivatives such as Tiprinast [4] have been shown to be
clinically effective antiallergics. Several thieno[2,3-b]pyridine derivatives are known to possess antibacterial
[5-7], antihypertensive [8], and gonadotropin releasing hormone antagonizing [9, 10] activity.
Many thienopyridines have been evaluated pharmacologically and have been found to show activity in
diabetes mellitus [11-13] and also as analgesics and anti-inflammatory agents [14-16], sedatives [14],
anticoagulants [16], and antiartherosclerotics [17-20]. Considerable attention has been drawn to the synthesis of
condensed heterocyclic systems derived from 1,2,4-triazoles, pyrazoles, and pyridothienopyrimidine [21-25]. In
continuation of our ongoing search for new heterocycles [26-29] we have prepared a series of compounds
containing a pyridothienopyrimidine moiety and tested their antimicrobial properties.
3-Amino-4,6-dimethylthieno[2,3-b]pyridine-2-carbonitrile (1) [30] reacted with ethylenediamine in the
presence of carbon disulfide to afford 2-(4,5-dihydro-1H-imidazol-2-yl)-4,6-dimethylthieno[2,3-b]pyridine-
3-amine (2). Its IR spectrum showed the disappearance of the characteristic absorption band at 2190 cm–1 of the
_______
* To whom correspondence should be addressed, e-mail: el_essawy2000@yahoo.com.
1Chemistry Department, Faculty of Science, Shebin El-Koam, Egypt.
__________________________________________________________________________________________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 415-424, March, 2010. Original
article received August 17, 2009.
0009-3122/10/4603-0325©2010 Springer Science+Business Media, Inc.
325

CN group, while the 1H NMR spectrum showed the appearance of a characteristic signal of methylene protons at
3.50-3.98 ppm, as well as a singlet at 7.98 ppm for the NH group. Compound 2 was subjected to cyclization to
tetracyclic imidazopyridothienopyrimidine systems in different ways. Treatment of compound 2 with triethyl
orthoformate (TEO) gave 7,9-dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine (3),
1
which showed a new signal in its H NMR spectrum at δ 8.14 ppm due to H-5 of the pyrimidine ring. The
reaction of compound 2 with benzaldehyde under conditions analogous to those reported in [31] led to the
formation of 7,9-dimethyl-5-phenyl-2,3,5,6-tetrahydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine
(4). Its 1H NMR spectrum showed signals at δ 5.22 and 6.32 because of NH and H-5 of the cyclized pyrimidine
ring. On the other hand, 7,9-dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine-5-thione
(5) was obtained by heating compound 2 with CS2 in boiling pyridine. The IR spectrum of compound 5 showed
1
absorption bands at 3250 (NH) and 1220 cm–1 (C=S). Also its H NMR spectrum showed a broad signal at
δ 7.88 ppm due to the NH group. Mass spectra of these derivatives 3, 4, and 5 showed an [M+] peak in
agreement with their molecular weight.
Me
N
N
HCOOH
N
and/or TEO
S
Me
Me
N
3
Ph
Me
Me
HN
S
NH2
N
H
N
PhCHO
N
S
N
N
Me
N
4
2
NH2
NH2
CS2
S
Me
HN
S
N
Me
NH2
N
Py/CS2
CN
Me
N
S
Me
N
5
1
Thione derivative 5 was readily converted into the corresponding 5-hydrazino-7,9-dimethyl-2,3-di-
hydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine (6) by treating with hydrazine hydrate at reflux
temperature. Its 1H NMR spectrum agreed with the structure, which showed a broad band at δ 4.41 and 7.20 ppm
corresponding to the NHNH2, and its mass spectrum revealed a molecular ion peak at 286, confirming the
molecular weight of compound 6. Cyclization of hydrazino derivative 6 by the action of TEO and sodium nitrite
in acetic acid gave the fused 9,11-dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e][1,2,4]-
triazolo[3,4-a]pyrimidine (7) and 10,12-dimethyl-5,6-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]tetra-
zolo[5,1-a]pyrimidine (8), respectively. The mass spectrum showed a molecular ion peak for each derivative at
m/z 296 and 297, respectively. Alkylation of compound 5 with ethyl 2-chloroacetate under alkaline condition
affords the S-alkylated compound 9, which was readily converted into the corresponding acetohydrazide 10
after treatment with hydrazine hydrate in absolute ethanol. The structure of derivatives 9 was confirmed by IR
1
spectrum, which showed absorption bands at 1729 cm–1 due to COOEt, besides its H NMR spectrum, which
showed signals as a triplet at δ 1.23, a quartet at δ 4.32 ppm due to the ester group, and a singlet at δ 4.98 for SCH2.
326

Also derivative 10 was assigned by IR spectroscopy, which revealed the absorption band at 3427-3248 cm–1 due
to NHNH2, and its 1H NMR spectrum showed the appearance of broad signals at δ 4.90 and 9.30 corresponding
to the NHNH2 group. The mass spectra of these derivatives 9 and 10 demonstrated the molecular ion peak for
each compound at m/z 374 and 360 corresponding to their molecular weight. The latter acetohydrazide
derivative 10 was treated with phenyl isothiocyanate in absolute ethanol to afford the corresponding
thiosemicarbazide derivative 11.
N
N
NHNH2
Me
Me
N
S
N
N
N
TEO
N2H4
N
N
S
Me
N
Me
N
7
6
AcOH
NaNO2
CONHNHCSNHPh
S
N
N
N
N
Me
Me
N
S
N
N
N
5
N
S
Me
N
Me
N
8
11
CONHNH2
S
PhNCS
S
CO2Et
N2H4
Me
Me
N
S
N
S
N
N
N
Cl
CO2Et
Me
N
N
Me
N
10
9
The thienopyridine derivative 1 reacted with TEO to give ethyl (2-cyano-4,6-dimethylthieno-
[2,3-b]pyridin-3-yl)imidoformate (12). This compound was used as an intermediate for the preparation of
1
compound 13 by cyclization with hydrazine hydrate. Its structure was elucidated using IR, MS, and H NMR
spectra, the latter showing two signals at δ 5.80 and 8.17 ppm corresponding to the vicinal amino and imino
groups, respectively. 4-Imino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidine-3(4H)-amine (13) is consi-
dered as a key intermediate for preparing fused heterocycles such as triazolo[1,5-c]pyrimidines, which may
possess pharmacological properties similar to those of theophylline [32, 33]. 7,9-Dimethylpyrido[3',2':4,5]-
thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine (14) was prepared by cyclocondensation reaction of derivative 13
with neat formic acid (yield 33%), while it was prepared by heating the derivative 13 with the
triethylorthoformate to afford the derivative 14 in good yield (83%). The structure of compound 14 was
elucidated by the mass spectrum, which showed a molecular ion peak at m/z 255 corresponding to the molecular
weight. 2,7,9-Trimethylpyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine (15) was obtained by boiling
1
compound 13 in glacial acetic acid. Its structure was elucidated, besides the mass spectrum, by the H NMR
spectrum, which showed a new signal corresponding to the methyl group of fused triazole ring at δ 3.06 ppm.
Moreover, the interaction of diethylmalonate with compound 13 afforded ethyl (7,9-trimethylpyrido[3',2':4,5]-
thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidin-2-yl)acetate (16) in good yield. Its structure was proven by the
327

1H NMR spectrum, which showed a triplet at δ 1.23 ppm, a quartet at δ 4.25 ppm, and a singlet at δ 4.10 ppm
corresponding to the ester and methylene groups, respectively, and the mass spectrum, which showed
a molecular ion peak at m/z 269 and 270 corresponding to [M+] and [M++1], respectively.
Investigation of the antimicrobial activity of compounds 3-6, 15, and 16 demonstrated that imidazoline 3
was active against the Gram-positive bacteria Bacillus cereus and Staphylococcus aureus while derivative 5
showed moderate inhibition zones against Bacillus cereus only. The other derivatives 4, 6, 15, and 16 were
inactive against the two examined species of Gram-positive bacteria. Compounds 3, 5, and 16 showed strong to
moderate activity against the fungi Candida albicans, Trichophyton rubrum, and Chrysosporium tropicum. The
relatively high antifungal activity of compound 16 may be due to the presence of fused 1,2,4-triazoles in its
molecule. The other derivatives showed no activity against the examined fungi species.
Me
Me
N
N
OEt
CN
N
NH2
N2H4
TEO
1
NH
S
Me
S
Me
N
N
13
12
CO2Et
CO2Et
TEO
AcOH
Me
N
Me
N
N
N
N
N
N
N
Me
N
N
N
N
S
Me
S
Me
N
N
EtO2C
14
16
N
Me
S
Me
15
TABLE 1. Antimicrobial Activity of Derivatives 3-6, 15, and 16
(Inhibition Zone, mm)*
Gram-positive bacteria
Fungi
Candida Trichophyton
Compound
Bacillus
Staphylococcus
aureus
Chrysosporium
tropicum
cereus
albicans
rubrum
3
18
—
12
—
—
—
52
21
—
—
—
—
—
54
14
—
13
—
—
12
12
31
—
24
—
—
21
50
31
—
24
—
—
28
52
4
5
6
15
16
Reference*2
_______
* Inhibition zone around the discs: 26-52 mm: very strong activity;
13-25 mm: strong activity; 0-7 mm: weak activity; dash denotes no activity.
*2 Chloramphenicol (5%, antibacterial activity); terbinafine (5%, anti-
fungal activity).
328

EXPERIMENTAL
IR spectra were recorded on a Nicolet FT-IR spectrophotometer on KBr discs. 1H and 13C NMR spectra
were recorded on a Varian Germini-2000 (300 and 75.5 MHz, respectively) and registered in DMSO-d6
(compounds 4–11) and CDCl3 (compounds 2, 3, 12–16), respectively. Mass spectra were measured on a Kratos
50 tc spectrometer. Microanalyses were performed in the microanalysis lab at Cairo University. Common
reagent-grade chemicals were either commercially available and were used without further purification or
prepared by standard literature procedures. All reactions were monitored by TLC carried out on 0.2 mm silica
gel 60 F-254 (Merck) plates using UV light (254 and 360 nm) for detection. Melting points were determined on
a Buchi melting point apparatus. The antimicrobial activity of the synthesized compounds was conducted at the
Botany Department, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt.
2-(4,5-Dihydro-1H-imidazol-2-yl)-4,6-dimethylthieno[2,3-b]pyridine-3-amine (2). To a suspension of
nitrile 1 (2.03 g, 10 mmol) in ethylenediamine (3 ml), carbon disulfide (1 ml) was added dropwise. The reaction
mixture was heated on a water bath for 2 h. The precipitated solid was triturated with ethanol (10 ml), filtered
off, and recrystallized from methanol to give a golden yellow crystals of compound 2 (2.22 g, 90%); mp
196-198ºC. IR spectrum, ν, cm–1: 3447-3330 (NH) and (NH2), 2917, 2860 (CH aliphatic), 1640 (C=N). 1H NMR
spectrum, δ, ppm: 2.59 (3H, s, CH3); 2.75 (3H, s, CH3); 3.50-3.98 (4H, m, CH2 imidazoline); 6.38 (2H, s, NH2);
6.86 (1H, s, Ar); 7.89 (1H, br. s, NH). Found, %: C 58.44; H 5.65; N 22.90. C12H14N4S. Calculated, %: C 58.51;
H 5.73; N 22.74.
7,9-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine (3). A mixture of
compound 2 (0.27 g, 1.1 mmol), TEO (5 ml), and a catalytic amount of glacial acetic acid (0.2 ml) was heated
for 4 h under reflux. The precipitate was filtered off and recrystallized from ethanol to afford pale-yellow
crystals of compound 3 (0.24 g, 86%); mp 173-175ºC. IR spectrum, ν, cm–1: 2915, 2860 (CH aliphatic), 1654
(C=N). 1H NMR spectrum, δ, ppm: 2.53 (3H, s, CH3); 2.77 (3H, s, CH3); 3.89-4.15 (4H, m, CH2 imidazoline);
7.14 (1H, s, H-8); 8.14 (1H, s, H-5). Mass spectrum, m/z (I, %): 256 [M]+ (85), 255 (100). Found, %: C 60.51;
H 4.65; N 21.74; S 12.44. C13H12N4S. Calculated, %: C 60.91; H 4.72; N 21.86; S 12.51.
7,9-Dimethyl-5-phenyl-2,3,5,6-tetrahydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine
(4). Concentrated HCl (0.1 ml) was added to a mixture of compound 2 (0.14 g, 0.55 mmol) and benzaldehyde
(0.16 g, 1.5 mmol) in anhydrous ethanol (5 ml). The mixture was stirred under reflux for 8 h, cooled, and
neutralized with an aqueous solution of sodium carbonate. The precipitate was filtered off and recrystallized
from methanol to afford pale-yellow powder of compound 4 (0.15 g, 79%); mp 112-115ºC. IR spectrum, ν, cm-1:
3250 (NH); 2934, 2864 (CH aliphatic); 1623 (C=N). 1H NMR spectrum, δ, ppm: 2.52 (3H, s, CH3); 2.62 (3H, s,
CH3); 3.60-3.97 (4H, m, CH2 imidazoline); 5.22 (1H, s, H-5); 6.32 (1H, br. s, NH); 7.07 (1H, s, H-8); 7.23-7.86
(5H, m, Ph). 13C NMR spectrum, δ, ppm: 20.48 (CH3); 24.83 (CH3); 50.90, 54.01 (2CH2 imidazoline);
76.00 (C-5), 122.88, 124.00, 129.26, 129.33, 129.60, 129.73, 139.92, 144.42, 145.22, 146.97, 152.53, 156.05,
159.05, 161.76 (C Ar). Mass spectrum, m/z (I, %): 334 [M]+ (20), 331 (70), 257 (100). Found, %: C 68.51;
H 5.65; N 16.40. C19H18N4S. Calculated, %: C 68.23; H 5.42; N 16.75.
7,9-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine-5-thione (5).
A
mixture of compound 2 (1.82 g, 7.4 mmol), CS2 (10 ml), and anhydrous pyridine (20 ml) was heated for 13 h on
water bath. The mixture was cooled and the precipitate was filtered off and recrystallized from methanol to give
light-yellow crystals of compound 5 (1.80 g, 85%); mp 250-152ºC. IR spectrum, ν, cm–1: 3123 (NH), 2950,
2857 (CH aliphatic), 1651 (C=N), 1220 (C=S). 1H NMR spectrum, δ, ppm: 2.66 (3H, s, CH3); 2.88 (3H, s, CH3);
3.59-3.77 (4H, m, CH2 imidazoline); 7.06 (1H, s, H-8); 7.88 (1H, br. s, NH). Mass spectrum, m/z (I, %): 288
[M]+ (100). Found, %: C 54.25; H 5.13; N 19.40; S 22.43. C13H12N4S2. Calculated, %: C 54.14; H 4.19;
N 19.43; S 22.24.
5-Hydrazino-7,9-dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]pyrimidine (6). A
mixture of thione 5 (1.84 g, 6.4 mmol), hydrazine hydrate (10 ml), and absolute ethanol (20 ml) was refluxed
329

for 5 h. The precipitate was filtered off and recrystallized from DMF to give a yellow powder of compound 6
(1.51 g, 83%); mp 230-232ºC. IR spectrum, ν, cm–1: 3400-3150 (NH2NH), 2920, 2854 (CH aliphatic), 1646
(C=N). 1H NMR spectrum, δ, ppm: 2.52, 2.56 (6H, 2s, CH3); 3.82-3.95 (4H, m, CH2 imidazoline); 4.41 (2H, s,
NH2); 7.10 (1H, s, H-8); 7.20 (1H, br. s, NH). Mass spectrum, m/z (I, %): 286 [M]+ (60), 270 [M+ -NH2] (100).
Found, %: C 54.70; H 5.02; N 29.36; S 11.43. C13H14N6S. Calculated, %: C 54.53; H 4.93; N 29.35; S 11.20.
9,11-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[3,4-a]pyrimi-
dine (7). A mixture of compound 6 (0.72 g, 2.5 mmol) and TEO (10 ml) was heated under reflux for 5 h. After
concentration and cooling at room temperature the reaction mixture was poured into ice-cold water. The
resulting solid product was collected by filtration, washed with methanol, dried, and recrystallized from
methanol to give compound 7 (0.51 g, 68%); mp 270–272ºC. IR spectrum, ν, cm–1: 2925, 2840 (CH aliphatic),
1
1640 (C=N). H NMR spectrum, δ, ppm: 2.55 (3H, s, CH3); 2.67 (3H, s, CH3); 3.77-3.98 (4H, m, CH2
imidazoline); 7.43 (1H, s, H-11); 9.20 (1H, s, H triazole). Mass spectrum, m/z (I, %): 296 [M]+ (100). Found, %:
C 56.65; H 4.11; N 28.45. C14H12N6S. Calculated, %: C 56.74; H 4.08; N 28.36.
10,12-Dimethyl-5,6-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[2,3-e]tetrazolo[5,1-a]pyrimidine
(8). A solution of sodium nitrite (0.4 g, 5 mmol) in 5 ml H2O was added dropwise under vigorous stirring at room
temperature to a solution of compound 6 (0.46 g, 1.6 mmol) in acetic acid (10 ml). After the addition was
complete, the reaction mixture was stirred for an additional 3 h and then neutralized with a sodium carbonate
solution. The solid product was separated by filtration and recrystallized from ethanol to give compound 8 (0.32
g, 67%); mp 235–237ºC. IR spectrum, ν, cm–1: 2930, 2822 (CH aliphatic), 1620 (C=N). 1H NMR spectrum, δ,
ppm: 2.60 (3H, s, CH3); 2.69 (3H, s, CH3); 3.80-3.96 (4H, m, CH2 imidazoline); 7.50 (1H, s, H-11). Mass
spectrum, m/z (I, %): 298 [M++1] (60), 297 [M+] (100). Found, %: C 52.35; H 3.55; N 32.63. C13H11N7S.
Calculated, %: C 52.51; H 3.73; N 32.97.
Ethyl [(7,9-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[3,2-e]pyrimidin-2-yl)sulfan-
yl]acetate (9). To a stirred suspension of thione 5 (1.44 g, 5 mmol) in dry DMF (10 ml), ethyl chloroacetate
(0.92 g, 7.5 mmol) and K2CO3 (1.04 g, 7.5 mmol) were added. The reaction mixture was stirred at room
temperature for 13 h and then poured into ice cold water with stirring. The obtained solid product was collected
by filtration, washed with water, and recrystallized from ethanol to afford pale-yellow crystals of compound 9
(1.68 g, 90%); mp 176-178ºC. IR spectrum, ν, cm–1: 2922, 2850 (CH aliphatic), 1729 (COOEt), 1653 (C=N). 1H
NMR spectrum, δ, ppm (J, Hz): 1.23 (3H, t, J = 7.1, CH2CH3); 2.62 (3H, s, CH3); 2.80 (3H, s, CH3); 4.10-4.22
(4H, m, CH2 imidazoline); 4.32 (2H, q, J = 7.0, CH2CH3); 4.98 (2H, s, SCH2); 7.31 (1H, s, H-8). 13C NMR
spectrum, δ, ppm: 15.13, 20.23 (2CH3); 25.23 (CH3CH2); 43.32 (CH3CH2); 48.28, 49.99 (2CH2 imidazoline);
62.71 (SCH2); 109.10, 123.71, 124.23, 125.13, 147.58, 153.17, 157.17, 161.54, 163.25 (Ar); 168.83 (CO). Mass
spectrum, m/z (I, %): 374 [M]+ (100). Found, %: C 54.41; H 4.65; N 14.40; S 17.08. C17H18N4O2S2. Calculated,
%: C 54.52; H 4.84; N 14.96; S 17.13.
2-(7,9-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[3,2-e]pyrimidin-5-yl)sulfanyl-
acetohydrazide (10). A solution of ester 9 (3.74 g, 10 mmol) in ethanol (30 ml) was refluxed with hydrazine
hydrate (1.25 g, 25 mmol) for 4 h. After cooling to room temperature a pale-yellow solid appeared. It was
recrystallized from methanol to afford hydrazide 10 (3.20 g, 89%); mp 295-296ºC. IR spectrum, ν, cm–1:
3330-3140 (NH2NH), 2939, 2820 (CH aliphatic), 1651 (CO). 1H NMR spectrum, δ, ppm: 2.55 (3H, s, CH3);
2.64 (3H, s, CH3); 3.88-4.10 (4H, m, CH2 imidazoline); 3.88 (2H, s, SCH2); 4.90 (2H, br. s, NHNH2); 7.40 (1H,
s, H-8); 9.30 (1H, br. s, NHNH2). Mass spectrum, m/z (I, %): 360 [M+] (100). Found, %: C 49.65; H 4.20;
N 23.16; S 17.59. C15H16N6OS2. Calculated, %: C 49.98; H 4.47; N 23.31; S 17.79.
1-(7,9-Dimethyl-2,3-dihydroimidazo[1,2-c]pyrido[3',2':4,5]thieno[3,2-e]pyrimidin-5-yl)sulfanyl-
acetyl-4-phenylthiosemicarbazide (11). To a solution of hydrazide 10 (1.80 g, 5 mmol) in absolute ethanol
(10 ml) phenyl isothiocyanate (0.68 g, 5 mmol) was added. The reaction mixture was heated under reflux for
4 h. The product that separated on cooling was filtered off, washed with ethanol, and dried well to give
compound 11 (2.10 g, 85%); mp 170-171ºC. IR spectrum, ν, cm–1: 3313 (NH), 2929, 2815 (CH aliphatic), 1680
330

(CO). 1H NMR spectrum, δ, ppm: 2.44, 2.54 (6H, 2s, CH3); 3.90-4.30 (4H, m, CH2 imidazoline); 4.53 (2H, s,
SCH2); 7.20-7.32 (6H, m, H-8, Ph); 9.60 (1H, br. s, PhNH); 9.71 (1H, br. s, CSNH); 10.17 (1H, br. s, CONH).
Mass spectrum, m/z (I, %): 495 [M+] (100). Found, %: C 53.18; H 4.09; N 19.56. C22H21N7OS3. Calculated, %:
C 53.31; H 4.27; N 19.78.
Ethyl (2-Cyano-4,6-dimethylthieno[2,3-b]pyridin-3-yl)imidoformate (12). A mixture of nitrile 1
(0.89 g, 4.4 mmol), TEO (10 ml), and acetic anhydride (3 ml) was heated on a water bath at 60ºC for 4 h. The
mixture was cooled and the precipitate was filtered off followed by recrystallization from ethanol to afford white
crystals of compound 12 (0.96 g, 83%); mp 128–130ºC. IR spectrum, ν, cm–1: 2199 (CN), 1644 (C=N). 1H NMR
spectrum, δ, ppm (J, Hz): 1.45 (3H, t, J = 7.4, OCH2CH3); 2.62 (3H, s, CH3); 2.65 (3H, s, CH3); 4.46 (2H, q,
J = 7.4, OCH2CH3); 6.99 (1H, s, H-5); 8.02 (1H, s, N=CH). Mass spectrum, m/z (I, %): 259 [M+] (30), 258 (40),
203 (100). Found, %: C 60.12; H 4.96; N 16.12; S 12.23. C13H13N3OS. Calculated, %: C 60.21; H 5.05;
N 16.20; S 12.36.
4-Imino-7,9-dimethylpyrido[3',2':4,5]thieno[3,2-d]pyrimidin-3(4H)-amine (13). A mixture of
compound 12 (5.70 g, 22 mmol) and hydrazine hydrate (8 ml, 80%) in ethanol (20 ml) was heated under reflux
for 2 h. The white precipitate formed after cooling was filtered off and dried. Recrystallization from ethanol
afforded white crystals of imine 13 (4.55 g, 84%); mp 218–220ºC. IR spectrum, ν, cm–1: 3322–3278 (NH2NH),
1624 (C=N). 1H NMR spectrum, δ, ppm: 2.55 (3H, s, CH3); 2.81 (3H, s, CH3); 5.80 (2H, s, NH2); 7.18 (1H, s, H-
8); 8.17 (1H, s, NH). Mass spectrum, m/z (I, %): 245 [M+] (20), 184 (100). Found, %: C 53.43; H 4.32; N 28.22;
S 12.84. C11H11N5S. Calculated, %: C 53.86; H 4.52; N 28.55; S 13.07.
7,9-Dimethylpyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine (14). A. A mixture of
imine 13 (0.61g, 2.5 mmol) and formic acid was refluxed for 10 h and then cooled and poured into ice water to
give a white precipitate, which was filtered off, washed several times with water, dried and recrystallized from
ethanol to afford gray crystals of compound 14 (0.21 g, 33%); mp 244–245ºC. IR spectrum, ν, cm–1: 2917, 2852
(CH aliphatic), 1618 (C=N). 1H NMR spectrum, δ, ppm: 2.70 (3H, s, CH3); 3.03 (3H, s, CH3); 7.20 (1H, s, H-8);
8.50 (1H, s, H-5); 9.43 (1H, s, H triazole). Mass spectrum, m/z (I, %): 255 [M+] (12), 69 (100). Found, %:
C 56.23; H 3.33; N 27.24; S 12.36. C12H9N5S. Calculated, %: C 56.45; H 3.55; N 27.43; S 12.56.
B. A mixture of imine 13 (0.61 g, 2.5 mmol) and TEO (2.2 g, 20 mmol) in DMF (10 ml) was refluxed for
7 h. After cooling and dilution with ice water (30 ml), the solid product formed was filtered off and
recrystallized from ethanol to furnish gray crystals of compound 14 (0.52g, 83%). Mass spectrum, m/z (I, %): 255
[M+] (12), 69 (100).
2,7,9-Trimethylpyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidine (15). A mixture of imine
13 (0.25 g, 1 mmol) and acetic acid (15 ml) was refluxed for 10 h. After cooling and dilution with ice water
(20 ml), the white precipitate formed was filtered off and recrystallized from ethanol to give white crystals of
compound 15 (0.21 g, 78%); mp 236-238ºC. IR spectrum, ν, cm–1: 2920, 2852 (CH aliphatic), 1621 (C=N). 1H
NMR spectrum, δ, ppm: 2.71 (3H, s, CH3); 2.73 (3H, s, CH3); 3.06 (3H, s, CH3); 7.19 (1H, s, H-8); 9.32 (1H, s,
H-5). Mass spectrum, m/z (I, %): 269 [M+] (100). Found, %: C 57.77; H 4.09; N 25.86; S 11.66. C13H11N5S.
Calculated, %: C 57.97; H 4.12; N 26.00; S 11.91.
Ethyl (7,9-Trimethylpyrido[3',2':4,5]thieno[2,3-e][1,2,4]triazolo[1,5-c]pyrimidin-2-yl)acetate (16). A
suspension of imine 13 (0.25 g, 1 mmol) and diethyl malonate (5 ml) was heated under reflux over its boiling
point for 2 h. The yellow solid product formed was triturated with ethanol, filtered off, and recrystallized from
ethanol to afford yellow crystals of ester 16 (0.29 g, 83%); mp 184-186ºC. IR spectrum, ν, cm–1: 2923, 2847
(CH aliphatic), 1714 (CO2Et), 1619 (C=N). 1H NMR spectrum, δ, ppm (J, Hz): 1.23 (3H, t, J = 7.2, CH3CH2);
2.72 (3H, s, CH3); 3.05 (3H, s, CH3); 4.10 (2H, s, CH2); 4.25 (2H, q, J = 7.2, CH3CH2); 7.20 (1H, s, H-8); 9.36
(1H, s, H-5). Mass spectrum, m/z (I, %): 341 [M+] (40), 269 (100). Found, %: C 56.15; H 4.31; N 20.22; S 9.17.
C16H15N5O2S. Calculated, %: C 56.29; H 4.43; N 20.51; S 9.39.
The Antimicrobial Activity of compounds 3-6, 15, and 16 was tested against the Gram-positive
bacteria Bacillus cereus and Staphylococcus aureus and against the fungi Candida albicans, Trichophyton
331

rubrum, and Chryosporium tropicum using chloramphenicol (5%) and terbinafine (5%) as standards by the disc-
diffusion technique [34, 35]. Samples were dissolved in DMSO to a concentration of 5%, and filter paper discs
(Whatman No. 3, 5 mm in diameter) were impregnated with the solutions. The discs were placed on the surface
of solidified nutrient agar dishes seeded by the test bacteria or Czapek's Dox agar dishes seeded by the test
fungi. The inhibition zones were measured in millimeters by the end of the incubation period (48 h at 37ºC for
bacteria and 28ºC for fungi). The results are collected in Table 1.
The authors are thankful to Prof. Dr. Mohamed Tawfeek, Botany Department, Faculty of Science,
Menoufia University, for help in the studies of biological activity of some compounds.
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