Pyridine-based heterocycles. Synthesis of new pyrido [4',3':4,5]thieno[2,3- d]pyrimidines and related heterocycles

Article abstract of DOI:10.3390/molecules15042651

The synthesis of the title compounds was achieved using ethyl 2-amino-6methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (1) as starting material. The reaction of the amino ester 1 with phenylisothiocyanate in boiling ethanol afforded the thiou

Full text of DOI:10.3390/molecules15042651

Molecules 2010, 15, 2651-2666; doi:10.3390/molecules15042651
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Pyridine-Based Heterocycles. Synthesis of New Pyrido
[4',3':4,5]thieno[2,3-d]pyrimidines and Related Heterocycles
Hussein El-Kashef 1,*, Abdel-Rahman Farghaly 1, Ahmed Al-Hazmi 2, Thierry Terme 3 and
Patrice Vanelle 3,*
1
Chemistry Department, Faculty of Science, Assiut University, 71516 Assiut, Egypt
2
Chemistry Department, Faculty of Science, Ibb University, Yemen
3
Laboratoire Pharmaco-Chimie Radicalaire, Faculté de Pharmacie, Universités d’Aix-Marseille I, II
et III-CNRS, UMR 6264, Laboratoire Chimie Provence, 27 Bd J. Moulin, 13385 Marseille cedex 5,
France
∗ Authors to whom correspondence should be addressed; E-Mails: elkashef@aun.edu.eg (H.E.-K.);
patrice.vanelle@univmed.fr (P.V.).
Received: 11 March 2010; in revised form: 31 March 2010 / Accepted: 6 April 2010 /
Published: 12 April 2010
Abstract: The synthesis of the title compounds was achieved using ethyl 2-amino-6-
methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (1) as starting material. The
reaction of the amino ester 1 with phenylisothiocyanate in boiling ethanol afforded the
thiourea derivative 5. The cyclization reactions of 5 under different reaction conditions led
to different pyridothienopyrimidine derivatives. Other reactions of the latter derivatives
leading to pyrido[4',3':4,5]thieno[2,3-d]triazolo[1,5-a]pyrimidines are also presented.
Keywords: pyrimidines; pyridines; thienopyrimidines; fused pyrimidines; fused pyridines
1. Introduction
Fused pyridine ring systems have received considerable attention due to their diverse biological
activity. In particular, pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4(3H)-ones were reported to be used for
the prophylaxis and therapy of cerebral ischemia [1,2], and as central nervous system agents [3]. Other
derivatives also act as 5-HT1A receptor antagonists and serotonin reuptake inhibitors [4], β-lactamase
inhibitors, analgesics, anti-inflammatory [5] and antimalarial agents [6]. Moreover, this triheterocyclic

Molecules 2010, 15
2652
system showed highly potent dual 5-HT1A and 5-HT1B antagonists as potential antidepressant drugs
[7]. The synthesis of other derivatives of this class of heterocycles were reported [8,9].
2. Results and Discussion
In view of the above findings and in continuation to our interest in the synthesis of polyfused
heterocycles of biological importance [10–23], the synthesis of the title compounds was deemed of
interest. Thus when the thienopyridine aminoester 1, which is easily accessible via the Gewald
reaction between 1-methylpiperidin-4-one, elemental sulfur and ethylcyanoacetate [7], was reacted
with triethyl orthoformate, the corresponding ethoxymethyleneamino intermediate 2 was obtained as a
reddish brown oil. This oil was reacted directly without any purification with hydrazine hydrate to give
3-amino-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one (3). Conden-
sation of 3 with aromatic aldehydes in boiling ethanol gave the corresponding arylidene derivatives
4a–h (Scheme 1).
Scheme 1. Synthesis of 3-arylideneamino-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]
thieno[2,3-d]pyrimidin-4-one (4a–h).
O
O
EtO
NH2
OEt
N
O
N2H4.H2O
N
N
CH(OEt)3
N
N
N
S
S
NH2
3
S
2
1
OEt
O
Ar
N
ArCHO
EtOH
N
a; Ar = C6H5, b; Ar = 4-ClC6H4, c; Ar = 4-OHC6H4,
d; Ar = 2-OHC6H4, e; Ar = 3-NO2C6H4, f; Ar = 4-NO2C6H4,
g; Ar = 4- OMeC6H4, h; Ar = 3,4-(OMe)2C6H3,
N
4a-h
N
S
Scheme 2. Synthesis of 3-amino-7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido
[4',3':4,5]thieno[2,3-d]pyrimidin-4-one (6) from the aminoester 1.
O
NH2
N
N
NHPh
N
S
6
O
Ph
N
COOEt
NH2
COOEt
N
NH2NH2.H2O
PhNCS
EtOH
S
N
N
N
S
H
NHCSNH-Ph
S
7
S
O
5
1
Ph
N
N
NHNH2
N
S
8
The reaction of the amino ester 1 with phenylisothiocyanate in boiling absolute ethanol gave the
corresponding thiourea derivative 5. When 5 was allowed to react with hydrazine hydrate, the three

Molecules 2010, 15
2653
possible structures 6 [24,25], 7 [5] and 8 [5] could be proposed for the reaction product (Scheme 2).
Interestingly, in our hands this reaction gave one product only. The IR spectrum of this reaction
product showed bands corresponding to primary NH2 functionality, thus from at first glance structure 7
could be ruled out.
An unequivocal synthesis was carried out to prove whether 6 or 8 is the structure of the reaction
product. Thus compound 5 was treated with concentrated sulfuric acid it gave the thiazinone derivative
9 which was then reacted with hydrazine hydrate, whereby an extrusion of the sulfur atom with its
replacement by an N-amino nitrogen atom occurred, giving 3-amino-7-methyl-2-phenylamino-5,6,7,8-
tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one (6) having the same melting point, mixed
melting point and spectral data as those of our reaction product (Scheme 3).
Scheme 3. Synthesis of 3-amino-7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido
[4',3':4,5]thieno[2,3-d]pyrimidin-4-one (6) from the thioureido ester 5.
O
O
O
NH2
OEt
S
N
N2H4.H2O
H2SO4
N
N
N
NHPh
NHPh
N
NHCSNHPh
N
S
S
S
5
9
6
On the other hand, compounds 7 and 8 could be obtained following different reaction pathways via
the procedure reported by El-Baih et al. [26]. Thus, 7 could be obtained when the thiourea derivative 5
was heated under reflux in ethanolic sodium hydroxide giving the sodium salt 10 which gave 7 upon
acidification with hydrochloric acid (Scheme 4).
Scheme 4. Synthesis of the pyridothienopyrimidinonethione 7 from 5.
O
O
Ph
COOEt
NHCSNHPh
Ph
N
N
NaOH / EtOH
HCl
N
N
S
SNa
N
N
S
N
S
S
7
H
5
10
Compound 8 was easily obtained by treatment of the 2-methylthio derivative 11 with hydrazine
hydrate in boiling ethanol. It is to be mentioned that compound 11 was obtained by methylation of
either the thione 7 in DMF, or by methylation of the sodium thiolate 10 in an aqueous solution as
shown in Scheme 5. Other alkylations of the thione 7 with ethyl chloroacetate, phenacyl bromide and
chloroacetone gave the corresponding products 13–15 respectively. When 8 was allowed to react with
ethoxymethylene malononitrile the reaction product was identified as 5-amino-1-(7-methyl-3-phenyl-
5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-2-yl)-1H-pyrazole-4-carbonitrile 12)
(Scheme 5).

Molecules 2010, 15
2654
Scheme 5. Synthesis of different pyridothienopyrimidines.
O
O
O
Ph
S
Ph
Ph
N
MeI / DMF
N
N
MeI / H2O
N
N
N
SMe
SNa
K2CO3
N
N
N
S
S
10
S
H
11
7
RX
NH2NH2.H2O
EtOH
AcONa/ EtOH
O
O
O
Ph
Ph
Ph
N
N
N
N
EtO-CH=C(CN)2
N
SR
N
N
N
NHNH2
N
S
13; R = -CH2COOEt
14; R = -CH2COPh
15; R = -CH2COCH3
N
N
S
S
8
H2N
12
CN
Compound 6 proved to be a key intermediate and served for the preparation of several new fused
heterocycles related to pyridothienopyrimidine ring system (Scheme 6).
Scheme 6. Pyridothienopyrimidine 6 as a versatile key intermediate.
O
O
O
NHCSNHPh
NHPh
N
N
SR
Ph
N
NHPh
NPh
17
N
KOH
EtOH
N
N
N
N
N
N
N
16
S
N
S
21; R = -CH2COOEt
22; R = -CH2COPh
23; R = -CH2COCH3
S
O
O
RX
AcONa
PhNCS
EtOH
N
N
EtOH
N
N
N
H
O
Ph
CH(OEt)3
Dioxane
O
S
19
NH2
N
S
N
N
CS2/ KOH
HCl
N
N
N
NHPh
N
H
N
Ph
CDI
N
S
S
N
18
6
O
N
CH2(COOEt)2
N
H
O
N
O
S
N
CH3COCl
Ph
OCH2CH3
N
20
CH3COCH2Cl
CH3COCH2COOEt
N
O
NH
Ph
O
O
H
N
S
N
27
O
N
O
O
H
O
N
N
N
NH
Ph
N
S
N
N
O
24
N
N
NH
Ph
NH
Ph
N
N
26
S
S
25
Thus the triazolo derivative 17 could be obtained via the reaction of 6 with phenylisothiocyanate in
boiling ethanol to give the thiourea derivative 16, which underwent a cyclodehydrosulfurization when
heated in ethanolic KOH under reflux to afford 7-methyl-2-phenylamino-3-phenyl-6,7,8,9-tetrahydro-
3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo[1,5-a]pyrimidin-10-one
(17).
Other
triazolo
derivatives could be obtained by the reaction of compound 6 with carbon disulfide, triethyl
orthoformate and 1',1'-carbonyldiimidazole (CDI), giving compounds 18–20 respectively. The thione
18 was alkylated with ethyl chloroacetate, phenacyl bromide and chloroacetone in boiling ethanol in

Molecules 2010, 15
2655
the presence sodium acetate to give the corresponding products 21-23 respectively. Compound 6,
when treated with acetyl chloride also gave N-(7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-
pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-3-yl)acetamide (24). The reaction of 6 with chloroacetone
in boiling ethanol afforded the corresponding 7-methyl-2-phenylamino-3-(2-oxopropylamino)-5,6,7,8-
tetrahydro-3H-pyrido- [4',3':4,5]thieno[2,3-d]pyrimidin-4-one (25). When 6 was reacted with ethyl
acetoacetate, a condensation reaction took place only between the keto carbonyl group of the ketoester
and the primary amino group of compound 6 giving ethyl 3-(7-methyl-2-phenylamino-5,6,7,8-
tetahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-3-ylimino)butanoate (26), whereas, the
reaction of 6 with diethyl malonate gave ethyl 3-(7-methyl-2-phenylamino-5,6,7,8-tetahydro-3H-
pyrido[4',3':4,5]thieno [2,3-d]pyrimidin-4-on-3-ylamino)-3-oxopropanoate (27) (Scheme 6).
It is worth mentioning that the reaction of 6 with ethyl ethoxymethylene cyanoacetate and
ethoxymethylenemalononitrile gave the triazepines 28 and 29 respectively (Scheme 7). Another
triazepine derivative was obtained when 6 was reacted with acetylacetone in boiling ethanol to give 5-
phenyl-2,4,9-trimethyl-8,9,10,11-tetrahydro-5H-pyrido[4'',3'':4',5']thieno[2',3':4,5]pyrimido[1,2-b][1,2,4]-
tri-azepin-12-one (30) (Scheme 7).
Scheme 7. Synthesis of pyridothienopyrimidotriazepines from 6.
O
N
CN
N
N
N
N
NH2
S
Ph
O
EtOCH=C(CN)2
29
N
N
COOEt
NH2
EtOCH=C(CN)(COOEt)
N
6
N
N
S
CH3COCH2COCH3
O
Ph
N
28
N
N
N
N
S
Ph
30
3. Experimental
3.1. General
All melting points are uncorrected and were measured on a Gallankamp melting point apparatus.
The IR spectra were recorded on a Shimadzu 470 IR-Spectrophotometer using the KBr wafer
1
technique. The H-NMR spectra were measured on a Jeol LA 400 MHz FT-NMR, Varian Unity-plus
300 (200 MHz) or Varian EM-390 (90 MHz) spectrometers with TMS as internal standard (δ values in
ppm). Elemental analyses were carried out using a Perkin-Elmer 240C Microanalyzer, and the results
were within an acceptable range.
3-Amino-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one
(3).
A
mixture of 1 (0.480 g, 2 mmol) and triethyl orthoformate (5 mL) was heated under reflux for 6 h. After
cooling, the solvent was removed in vacuo and the brownish red oil obtained was used directly without

Molecules 2010, 15
2656
purification in the next step. A mixture of the latter intermediate (0.592 g, 2 mmol) and excess of
hydrazine hydrate (5 mL) in ethanol (10 mL) was refluxed for 1 h. The solvent was then removed
under reduced pressure. The solid product obtained was triturated with water, filtered and
recrystallized from ethanol as pale buff crystals, yield 0.48 g (81%), m.p. 194–196 ºC. IR: υ cm-1 =
3,450, 3,300 (NH2), 2,910 (CH alph.), 1,670 (C=O).1H-NMR (CDCl3): δ = 2.50 (s, 3H, NCH3), 2.80
(m, 2H, CH2), 3.20 (m, 2H, CH2), 3.67 (s, 2H, CH2), 5.13 (bs, 2H, NH2), 8.20 (s, 1H, CH pyrimidine).
C10H12N4OS (236.30) Calcd.: C, 50.83; H, 5.12;N, 23.71; S, 13.57. Found: C, 50.93; H, 4.92; N, 23.41;
S, 13.87.
3.2. General procedure for the synthesis of 3-arylideneamino-7-methyl-5,6,7,8-tetrahydro-3H-
pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-ones 4a–h
A mixture of compound 3 (0.236 g, 1 mmol) and the appropriate aromatic aldehyde (0.001 mol) in
ethanol (10 mL) was refluxed for 2 h. After cooling, the solid precipitate was collected and
recrystalized from appropriate solvent to give 4a–h.
3-(Benzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one
(4a). This compound was obtained from ethanol as yellow crystals, yield 0.30 g (92%),
m.p. 166–168 ºC. IR: υ cm-1 = 3,050 (CH arom.), 2,920 (CH aliph.), 1,670 (C=O). 1H-NMR (CDCl3):
δ = 2.43 (s, 3H, NCH3), 2.67 (t, 2H, CH2), 3.10 (t, 2H, CH2), 3.80 (s, 2H, CH2), 6.83 (m, 3H, Ar-H),
7.76 (m, 2H, Ar-H), 8.10 (s, 1H CH, pyrimidinone), 9.20 (s, 1H, N=CH). C17H16N4 OS (324.40)
Calcd.: C, 62.94; H, 4.97; N, 17.27; S, 9.88. Found: C, 62.72; H, 4.82; N, 16.94; S, 9.95.
3-(4-Chlorobenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d] pyrimi
din-4-one (4b). This compound was obtained from ethanol as pale yellow crystals, yield 0.21 g (85%),
m.p. 198–200 ºC. IR: υ cm-1 = 3,030 (CH arom.), 2,950 (CH aliph.), 1,675 (C=O). 1H-NMR (CDCl3): δ
= 2.43 (s, 3H, NCH3), 2.70 (t, 2H, CH2), 3.07 (t, 2H, CH2), 3.56 (s, 2H, CH2), 7.36 (d, 2H, J = 8 Hz,
Ar-H), 7.69 (d, 2H, J = 8 Hz, Ar-H), 8.14 (s, 1H, CH pyrimidinone), 9.54 (s, 1H, N=CH).
C17H15ClN4OS (358.85) Calcd.: C, 56.90; H, 4.21; Cl, 9.88; N, 15.61; S, 8.94. Found: C, 56.68; H,
4.03; Cl, 9.38; N, 15.30; S, 8.66.
3-(4-Hydroxybenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d] pyrim
idin-4-one (4c). This compound was obtained from ethanol as yellow crystals, yield 0.21 g (62%), m.p.
1
224–226 ºC. IR: υ cm-1 = 3,350 (OH), 3,050 (CH arom.), 2,900 (CH aliph.), 1,670 (C=O). H-NMR
(CDCl3): δ = 2.32 (s, 3H, NCH3), 2.61 (t, 2H, CH2), 2.93 (t, 2H, CH2), 3.49 (s, 2H, CH2), 6.89 (d, 2H,
J = 8.5 Hz, Ar-H), 7.72 (d, 2H, J = 8.5 Hz, Ar-H), 8.37 (s, 1H, CH pyrimidinone), 8.87 (s, 1H, N=CH),
11.02 (s, 1H, OH). C17H16N4O2S (340.41) Calcd.: C, 59.98; H, 4.74; N, 16.46; S, 9.42. Found: C,
59.68; H, 4.55; N, 16.16; S, 9.23.
3-(2-Hydroxybenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d] pyrim
idin-4-one (4d). This compound was obtained as white powder from ethanol, yield: 0.29 g (86%), m.p.
200–202 ºC. IR: υ cm-1 = 3,320 (OH), 3,090 (CH arom.), 2,930 (CH aliph.), 1,670 (C=O). 1H-NMR

Molecules 2010, 15
2657
(CDCl3): δ = 2.34 (s, 3H, NCH3), 2.93 (t, 2H, CH2), 3.17 (t, 2H, CH2), 3.67 (s, 2H, CH2), 7.33 (m, 4H,
Ar-H), 8.21 (s, 1H, CH pyrimidine), 9.45 (s, 1H, N=CH), 10.90 (s, 1H, OH). C17H16N4O2S (340.40)
Calcd.: C, 59.98; H, 4.74; N, 16.46; S, 9.42. Found: C, 59.66; H, 4.49; N, 16.69; S, 9.81.
3-(3-Nitrobenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-
4-one (4e). This compound was obtained from ethanol as yellow crystals, yield: 0.30 g, (81%),
m.p. 208–210 ºC. IR: υ cm-1 = 3,020 (CH arom.), 2,960 (CH aliph.), 1,675 (C=O), 1,520, 1,350 (NO2).
1H-NMR (DMSO-d6): δ = 2.47 (s, 3H, NCH3), 2.77 (t, 2H, CH2), 3.13 (t, 2H, CH2), 3.62 (s, 2H, CH2),
7.61 (m, 1H, Ar-H), 8.16 (m, 1H, Ar-H), 8.30 (m, 1H, Ar-H), 8.36 (s, 1H, Ar-H), 8.60 (s, 1H, CH
pyrimidine), 9.83 (s, 1H, N=CH). C17H15N5O3S (369.40) Calcd.: C, 55.27; H, 4.09; N, 18.96; S, 8.68.
Found: C, 54.98; H, 3.81; N, 18.88; S, 8.95.
3-(4-Nitrobenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-
4-one (4f). This compound was obtained from ethanol as yellowish crystals, yield 0.34 g (92%),
m.p. 218–220 ºC. IR: υ cm-1 = 3,020 (CH arom.), 2,950 (CH aliph.), 1,670 (C=O), 1,530, 1,330 (NO2).
1H-NMR (CDCl3): δ = 2.91 (s, 3H, NCH3), 3.18 (t, 2H, CH2), 3.44 (t, 2H, CH2), 4.39 (s, 2H, CH2),
8.27 (m, 3H, Ar-H + CH pyrimidinone), 8.37 (d, 2H, J = 8.8 Hz, Ar-H), 8.79 (s, 1H, N=CH).
C17H15N5O3S (369.40) Calcd.: C, 55.27; H, 4.09; N, 18.96; S, 8.68. Found: C, 54.99; H, 3.81; N,
18.18; S, 7.95.
3-(4-Methoxybenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-
4-one (4g). This compound was obtained from ethanol as yellowish crystals, yield 0.21 g (59%), m.p.
168–170 ºC. IR: υ cm-1 = 3,050 (CH arom.), 2,900 (CH aliph.), 1,665 (C=O). 1H-NMR (CDCl3):
δ = 2.43 (s, 3H, NCH3), 2.70 (t, 2H, CH2), 3.09 (t, 2H, CH2), 3.56 (s, 2H, CH2), 3.79 (s, 3H, OCH3),
6.89 (d, 2H, J = 8.7 Hz, Ar-H), 7.71 (d, 2H, J = 8.7 Hz, Ar-H), 8.13 (s, 1H, CH pyrimidinone), 9.24 (s,
1H, N=CH). C18H18N4O2S (354.43) Calcd.: C, 61.00; H, 5.12; N, 15.81; S, 9.05. Found: C, 60.15; H,
4.31; N, 15.55; S, 8.85.
3-(3,4-Dimethoxybenzylideneamino)-7-methyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-
4-one (4h). This compound was obtained from ethanol as yellow crystals yield 0.22 g (57%), m.p.
162–164 ºC. IR: υ cm-1 = 3,090 (CH arom.), 2,940 (CH aliph.), 1,665 (C=O).1H-NMR (CDCl3):
δ = 2.47 (s, 3H, NCH3), 2.74 (t, 2H, CH2), 3.13 (t, 2H, CH2), 3.61 (s, 2H, CH2), 3.91 (s, 3H, OCH3),
3.92 (s, 3H, OCH3), 6,99 (d, 1H, J = 8.5 Hz, Ar-H), 7.24 (dd, 1H, J = 2.5, 8.5 Hz, Ar-H), 7.36 (d, 1H J
= 2.5, Ar-H), 8.19 (s, 1H, CH pyrimidinone), 9.23 (s, 1H, N=CH). C19H20N4O3S (384.45) Calcd.: C,
59.36; H, 5.24; N, 14.57; S, 8.34. Found: C, 59.05; H, 4.94; N, 14.85; S, 8.30.
Ethyl 6-methyl-2-(3-phenylthioureido)-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate (5). A
mixture of 1 (7.2 g, 30 mmol) and phenylisothiocyanate (4.1 g, 30 mmol) in absolute ethanol (20 mL)
was heated under reflux for 2 h. After cooling, the solid product was collected, dried and recrystalized
from ethanol to give yellow crystals, yield 7.01 g (62%), m.p. 201–202 ºC. IR: υ cm-1 = 3,180 (NH),
1
2,900 (CH aliph.), 1,670 (C=O), 1,190 (C=S). H-NMR (DMSO-d6): δ = 1.24 (t, 3H, J = 7.1 Hz,
CH2CH3), 2.31 (s, 3H, NCH3), 2.57 (t, 2H, CH2), 2.75 (t, 2H, CH2), 3.54 (s, 2H, CH2), 4.19 (q, 2H,

Molecules 2010, 15
2658
J = 7.1 Hz, CH2CH3), 7.21 (m, 3H, Ar-H), 7.38 (m, 2H, Ar-H), 8.45 (s, 1H, NH), 12.07 (s, 1H, NH).
C18H21N3O2S2 (375.51) Calcd.: C, 57.57; H, 5.64; N, 11.19; S, 17.08. Found: C, 57.33; H, 5.36; N,
10.96; S, 16.80.
3-Amino-7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-
one (6): A mixture of the arylthiourea 5 (3.75 g, 10 mmol) and excess hydrazine hydrate (5 mL) was
heated under reflux for 12 h. After cooling, the precipitate formed was filtered, dried and recrystalized
from ethanol/dioxane (1:2) to give white crystals, yield: 2.03 g (62%), m.p. 252–254 ºC.
1
IR: υ cm-1 = 3,350, 3,300 (NH2), 3,200 (NH), 3,050 (CH arom.), 2,900 (CH aliph), 1,660 (C=O). H-
NMR (DMSO-d6): δ = 2.41 (s, 3H, NCH3), 2.64 (t, 2H, CH2), 2.98 (t, 2H, CH2), 3.40 (s, 2H, CH2),
4.79 (bs, 2H, NH2), 7.32 (m, 2H, Ar-H), 7.61 (m, 3H, Ar-H), 8.51 (bs, 1H, NH). MS : m/z (rel. int.)
329 (M+, 91%), 328 (40), 327 (100), 253 (22.8), 77 (20). C16H17N5OS (327.40) Calcd.: C, 58.69; H,
5.23; N, 21.39; S, 9.79. Found: C, 58.59; H, 4.95; N, 21.11; S, 9.89.
7-Methyl-3-phenyl-2-thioxo-1,2,5,6,7,8-hexahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one
(7). Method (a): A suspension of compound 5 (3.75 g, 10 mmol) in an ethanolic solution of sodium
hydroxide (2N, 5 mL) was heated under reflux for 2 h. The reaction mixture was cooled and acidified
with hydrochloric acid (2N), whereupon a solid product was separated out. The solid product formed
was filtered and recrystallized from ethanol as yellow crystals, yield 3.1 g (94%), m.p. 296–298 ºC. IR:
1
υ cm-1 = 2900 (CH aliph.), 2400 (SH), 1680 (C=O). H-NMR (DMSO-d6): δ = 2.33 (s, 3H, NCH3),
2.83 (m, 4H, 2CH2), 3.33 (s, 2H, CH2), 7.13 (m, 3H, Ar-H), 7.33 (m, 2H, Ar-H). MS : m/z (rel. int.)
329 (M-2, 57%), 324.35 (13.5), 299.22 (24.8), 285.25 (41.9), 252.70 (24.5), 76.83 (33), 17.96 (24.4).
C16H15N3OS2 (329.44) Calcd.: C, 58.33; H, 4.59; N, 12.75; S, 19.47. Found: C, 58.45; H, 4.35; N,
12.88; S, 19.25. Method (b): An aqueous solution of compound 10 (3.83 g, 10 mmol) was acidified
with concentrated hydrochloric acid whereupon a solid product was separated out which was filtered,
washed with water and recrystallized from ethanol to give as yellow crystals, yield: 3.28 g (86%).
2-Hydrazino-7-methyl-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-one
(8). A mixture of 11 (0.37 g, 1 mmol) and hydrazine hydrate (5 mL) in ethanol (10 mL) was heated
under reflux for 2 h. The reaction mixture was then allowed to cool and the solid product obtained was
collected and recrystallized from ethanol as white crystals, yield 0.17 g (52%), m.p. 148–150 ºC.
1
IR: υ cm-1 = 3,300, 3,250 (NHNH2), 3,050 (CH arom.), 2,910 (CH aliph.), 1,670 (C=O). H-NMR
(CDCl3): δ = 2.46 (s, 3H, NCH3 ), 2.75 (t, 2H, CH2), 3.03 (t, 2H, CH2), 3.61 (s, 2H, CH2), 3.90 (bs, 2H,
NH2), 5.35 (bs, 1H, NH), 7.25 (m, 3H, Ar-H), 7.56 (m, 2H, Ar-H). C16H17N5SO (327.41) Calcd.: C,
58.69; H, 5.23; N, 21.39; S, 9.79. Found: C, 58.45; H, 4.99; N, 21.27; S, 9.58.
7-Methyl-2-phenylamino-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3-d][1,3]thiazin-4-one (9).
A
mixture of the compound 5 (3.75 g, 10 mmol) and concentrated sulfuric acid (5 mL) was stirred for 6
h. The reaction mixture was then poured cautiously into cold sodium bicarbonate solution. The solid
product obtained was filtered, washed with water and recrystallized from ethanol/dioxane (2:3) to give
1
yellow crystals, yield 3.2 g (97%), m.p. 282–284 ºC. IR: υ cm-1 = 3400 (NH), 1640 (C=O). H-NMR
(DMSO-d6,): δ = 2.50 (s, 3H, NCH3), 2.67 (t, 2H, CH2), 3.03 (t, 2H, CH2), 4.40 (bs, 1H, NH), 7.40 (m,

Molecules 2010, 15
2659
2H, Ar-H), 7.67 (m, 3H, Ar-H). C16H15N3OS2 (329.44). Calcd.: C, 58.33; H, 4.59; N, 12.76; S, 19.47.
Found: C, 58.13; H, 4.24; N, 12.53; S, 19.70.
Sodium salt of 2-mercapto-7-methyl-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]
pyrimidin-4-one (10). To a solution of sodium hydroxide (0.40 g, 10 mmol) in absolute ethanol
(30 mL) compound 5 (3.75 g, 10 mmol) was added and the resulting mixture was heated under reflux
for 2 h. The precipitate that was formed on hot was filtered, washed with boiling ethanol and dried to
give yellow powder, yield 2.8 g (80%), m.p. >300 ºC. IR: υ cm-1 = 3,030 (CH arom.), 2,900 (CH
aliph.), 1,640 (C=O).
7-Methyl-2-(methylthio)-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-
one (11). Method (a): To a solution of compound 10 (3.51 g, 10 mmol) in water (15 mL) methyl iodide
(1.8 g, 13 mmol) was added under stirring at room temperature. After complete addition, the reaction
mixture was stirred for 2 h further. The solid product thus formed was filtered and recrystallized from
dioxane to give white crystals, yield 3.21 g (93%), m.p. 202–204 ºC. IR: υ cm-1 = 2,990 (CH aliph.),
1
1,680 (C=O). H-NMR (CDCl3): δ = 2.40 (s, 3H, NCH3), 2.51 (s, 3H, SCH3), 2.74 (t, 2H, CH2), 3.07
(t, 2H, CH2), 3.78 (s, 2H, CH2), 7.31 (m, 3H, Ar-H), 7.55 (m, 2H, Ar-H). MS: m/z (rel. int.) 343 (M+,
80.7%), 338 (50), 300 (100), 253 (78.8), 150 (17.8), 76.83 (33), 58 (97.9). C17H17N3OS2 (343.47)
Calcd.: C, 59.45; H, 4.99; N, 12.23; S, 18.67. Found: C, 59.11; H, 4.75; N, 12.17; S, 18.35. Method
(b): To a mixture of 7 (3.29 g, 10 mmol) and potassium carbonate (0.5 g) in dimethylformamide
(15 mL), methyl iodide (2 mL) was added and the reaction mixture was gently heated on a water bath
at 60 ºC for 2 h. After cooling, the reaction mixture was poured on water, and the solid product was
filtered, washed with water and recrystallized from dioxane to give white crystals, yield 0.97g (28%).
5-Amino-1-(7-methyl-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-2-
yl)-1H-pyrazole-4-carbonitrile (12). A mixture of compound 8 (0.65 g, 2 mmol) and
ethoxymethylenemalononitrile (0.254 g, 2 mmol) in absolute ethanol (10 mL) was heated under reflux
for 8 h. After cooling, the solvent was removed in vacuo and the solid residue was recrystallized from
ethanol to give yellow crystals, yield 0.46 g (57%), m.p. 228–230 ºC. IR: υ cm-1 = 3,300, 3,150 (NH2),
1
2,900 (CH aliph.), 2,200 (C≡N), 1,640 (C=O). H-NMR (DMSO-d6): δ = 2.57 (s, 3H, NCH3), 2.83 (t,
2H, CH2), 3.17 (t, 2H, CH2), 4.17 (s, 2H, CH2), 4.47 (bs, 2H, NH2), 7.53 (m, 6H, Ar-H + CH
pyrazole). C20H17N7SO (403.46) Calcd.: C, 59.54; H, 4.25; N, 24.30; S, 7.95. Found: C, 59.25; H,
4.19; N, 24.28; S, 7.77.
3.3. General procedure for the synthesis of compounds 13–15 (from 7) and 21–23 (from 18) with
appropriate RX
A mixture of 7 (0.66 g, 2 mmol) or 18 (0.74 g, 2 mmol), appropriate RX (2 mmol) and sodium
acetate (5 mmol for reaction with 7 or 10 mmol for reaction with 18) in ethanol (10 mL) was heated
under reflux for 3 h. After cooling, the solid product was collected by filtration, washed with water and
recrystallized from appropriate solvent.

Molecules 2010, 15
2660
Ethyl (7-methyl-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-2-yl)-
thioacetate (13). yellow crystals, yield 0.51 g (61%), m.p. 204–206 ºC (ethanol/water 3/1).
1
IR: υ cm-1 = 3,040 (CH arom.), 2,950 (CH aliph.), 1,730 (C=O), 1,650 (C=O). H-NMR (CDCl3):
δ = 1.30 (t, J = 7.1 Hz, 3H, CH2CH3), 2.53 (s, 3H, NCH3), 2.79 (t, 2H, CH2), 3.10 (t, 2H, CH2), 3.67 (s,
2H, CH2), 3.85 (s, 2H, SCH2), 4.23 (q, J = 7.1 Hz, 2H, CH2CH3), 7.33 (m, 2H, Ar-H) ; 7.55 (m, 3H, Ar-
H). MS: m/z (rel. int.) 415 (M+, 70%), 372 (75), 328 (73), 285 (24), 253 (72), 122 (24), 77 (40).
C20H21N3O3S2 (415.53) Calcd.: C, 57.81; H, 5.09; N, 10.11; S, 15.43. Found: C, 57.63; H, 5.17; N,
9.97; S, 15.35.
7-Methyl-2-(phenacylthio)-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-
one (14). yellow crystals, yield 0.75 g (84%), m.p. 220–222 ºC (ethanol). IR: υ cm-1 = 1,690 (C=O),
1,665 (C=O). 1H-NMR (CDCl3): δ = 2.48 (s, 3H, NCH3), 2.74 (t, 2H, CH2), 3.10 (t, 2H, CH2), 3.60 (s,
2H, CH2), 4.55 (s, 2H, SCH2), 7.35 (m, 3H, Ar-H), 7.53 (m, 5H, Ar-H), 8.02 (m, 2H, Ar-H).
C24H21N3O2S2 (447.57) Calcd.: C, 64.40; H, 4.37; N, 9.39; S, 14.33. Found: C, 64.05; H, 4.22; N, 9.33;
S, 14.12.
7-Methyl-2-[(2-oxopropyl)thio]-3-phenyl-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d] pyrimidin-
4-one (15). white crystals, yield: 0.52
g
(68%), m.p. 215–217 ºC (ethanol).
IR: υ cm-1 = 2,900 (CH aliph.), 1,710 (C=O), 1,680 (C=O). H-NMR (CDCl3): δ = 2.50 (s, 3H,
COCH3), 2.67 (s, 3H, NCH3), 2.95 (t, 2H, CH2), 3.23 (t, 2H, CH2), 3.81 (s, 2H, CH2), 4.03 (s, 2H,
SCH2), 7.45 (m, 2H, Ar-H), 7.68 (m, 3H, Ar-H). C19H19N3O2S2 (385.51) Calcd.: C, 59.19; H, 4.97; N,
10.90; S, 16.64. Found: C, 59.03; H, 4.79; N, 10.87; S, 16.60.
1
Ethyl (7-methyl-3-phenyl-6,7,8,9-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo[1,5-a]
pyrimidin-10-on-2-yl)thioacetate (21). pale yellow crystals, yield 0.53 g (58%), m.p. 178–180 ºC
(water/methanol 2/1). IR: υ cm-1 = 3,050 (CH arom.), 2,910 (CH aliph.), 1,730 (C=O), 1,680 (C=O).
1H-NMR (CDCl3): δ = 2.29 (t, J = 7.1 Hz, 3H, CH2-CH3), 2.73 (s, 3H, NCH3), 2.92 (t, 2H, CH2), 3.27
(t, 2H, CH2), 3.59 (s, 2H, CH2), 3.82 (q, J = 7.1 Hz, 2H, CH2-CH3), 4.27 (s, 2H, SCH2), 7.61 (m, 5H,
Ar-H). C21H21N5O3S2 (455.56) Calcd.: C, 55.37; H, 4.65; N, 15.37; S, 14.08. Found: C, 55.55; H, 4.57;
N, 15.56; S, 14.27.
7-Methyl-2-phenacylthio-3-phenyl-6,7,8,9-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4] triazolo
[1,5-a]pyrimidin-10-one (22). yellowish crystals, yield 0.13 g (33%), m.p. 200–202 ºC
(water/methanol 2/1). IR: υ cm-1 = 3,050 (CH arom.), 2,910 (CH aliph.), 1,720 (C=O), 1,680
(C=O).1H-NMR (CDCl3): δ = 2.48 (s, 3H, NCH3), 2.72 (t, 2H, CH2), 3.08 (t, 2H, CH2), 3.63 (s, 2H,
CH2), 4.70 (s, 2H, CH2), 7.34 (m, 3H, Ar-H), 7.47 (m, 5H, Ar-H), 7.79 (m, 2H, Ar-H). C25H21N5O2S2
(487.60) Calcd.: C, 61.58; H, 4.34; N, 14.36; S, 13.15. Found: C, 61.49; H, 4.35; N, 14.19; S, 12.99.
7-Methyl-2-[(2-oxopropyl)thio]-3-phenyl-6,7,8,9-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]
triazolo[1,5-a]pyrimidin-10-one (23). yellow crystals, yield 0.61 g (72%). m.p. 194–196 ºC
1
(water/methanol 3/2). IR: υ cm-1 = 2,910 (CH aliph.), 1,730 (C=O), 1,690 (C=O). H-NMR (CDCl3):
δ = 2.29 (s, 3H, COCH3), 2.48 (s, 3H, NCH3), 2.74 (t, 2H, CH2), 3.10 (t, 2H, CH2), 3.64 (s, 2H, CH2),

Molecules 2010, 15
2661
4.11 (s, 2H, SCH2), 7.45 (m, 5H, Ar-H). C20H19N5O2S2 (425.53) Calcd.: C, 56.45; H, 4.50; N, 16.46; S,
15.07. Found: C, 56.25; H, 4.25; N, 16.27; S, 15.25.
7-Methyl-2-phenylamino-3-(3-phenylthioureido)-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]
pyrimidine-4-one (16). A mixture of 6 (1.64 g, 5 mmol) and phenyl isothiocyanate (0.68 g, 5 mmol) in
absolute ethanol (10 mL) was refluxed for 4 h. After cooling, the solid precipitate obtained was filtered
and recrystallized from ethanol/dioxane (2:1) as reddish crystals, yield: 2.04 g (88%), m.p.
209–210 ºC. IR: υ cm-1 = 3,350, 3,300, (NH), 3,050 (CH arom.), 2,900 (CH aliph.), 1,680 (C=O),
1
1,220 (C=S). H-NMR (CDCl3): δ = 2.47 (s, 3H, NCH3), 3.27 (m, 6H, 3CH2), 7.31 (m, 10H, Ar-H),
9.25 (bs, 1H, NH), 9.55 (bs, 1H, NH), 9.94 (bs, 1H, NH). C23H22N6OS2 (462.59) Calcd.: C, 59.72; H,
4.79; N, 18.17; S, 13.86. Found: C, 59.55; H, 4.62; N, 18.35; S, 13.65.
7-Methyl-2-phenylamino-3-phenyl-6,7,8,9-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo
[1,5-a]pyrimidin-10-one (17). A solution of compound 16 (0.463 g, 1 mmol) in ethanolic KOH (2N,
5 mL) was heated under reflux for 2 h. The reaction mixture was cooled and acidified with
hydrochloric acid (2N), whereupon a solid product was separated out. This solid was filtered, washed
with water and recrystallized from ethanol as buff crystals, yield 0.23 g (54%), m.p. 178–180 ºC.
IR: υ cm-1 = 3,200 (NH), 3,120 (CH arom.), 2,900 (CH aliph.), 1,675 (C=O).1H-NMR (CDCl3): δ 2.50
(s, 3H, NCH3), 2.86 (t, 2H, CH2), 3.19 (t, 2H, CH2), 6.68 (s, 2H, CH2), 6.92 (m, 5H, Ar-H), 7.68
(m, 5H, Ar-H), 7.92 (bs, 1H, NH). C23H20N6OS (428.51) Calcd.: C, 64.47; H, 4.70; N, 19.61; S, 7.48.
Found: C, 64.22; H, 4.79; N, 19.50; S, 7.33.
7-Methyl-3-phenyl-2-thioxo-1,2,6,7,8,9-hexahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo
[1,5-a]pyrimidin-10-one (18). A mixture of the thienopyrimidine compound 6 (0.327 g, 1 mmol),
carbon disulfide (3 mL) and potassium hydroxide (0.5 g, 9 mmol) in absolute ethanol (10 mL) was
heated under reflux for 5 h. The solvent and the excess of carbon disulfide were removed in vacuo.
The residue was treated with cold water (100 mL) and the resulting mixture was stirred then acidified
with hydrochloric acid (2N). The precipitate thus formed was filtered and recrystallized from ethanol
to give yellow crystals, yield 0.27 g (84%), m.p. 235–237 ºC. IR: υ cm-1 = 3,300 (NH), 3,050 (CH
arom.), 2,900 (CH aliph.), 1,670 (C=O), 1,210 (C=S). 1H-NMR (CDCl3): δ = 2.40 (s, 3H, NCH3), 2.70
(t, 2H, CH2), 2.90 (t, 2H, CH2), 3.50 (s, 2H, CH2), 5.11 (bs, 1H, NH), 7.16 (m, 5H, Ar-H). MS: m/z
(rel. int.) 367.75 (M-, 36.7%), 325 (39.5), 28 (29.4), 18 (100), 17 (22). C17H15N5S2O (369.47) Calcd.:
C, 55.26; H, 4.09; N, 18.96; S, 17.37. Found: C, 54.98; H, 3.94; N, 18.65; S, 17.30.
7-Methyl-3-phenyl-6,7,8,9-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo[1,5-a] pyrimi
din-10-one (19). A mixture of 6 (1.25 g, 3.8 mmol) and triethyl orthoformate (8 mL) was maintained at
reflux for 4 h. After cooling, the excess of triethyl orthoformate was removed under reduced pressure.
The residue obtained was recrystallized from petroleum ether/ethanol (9:2) to give white crystals, yield
0.85 g (66%), mp 243–245 ºC. IR: υ cm-1 = 3,050 (CH arom.), 2,910 (CH aliph.), 1,680 (C=O).
1H-NMR (DMSO-d6): δ = 2.19 (s, 3H, NCH3), 2.96 (t, 2H, CH2), 3.17 (t, 2H, CH2), 4.55 (s, 2H, CH2),
7.44 (m, 3H, Ar-H), 7.55 (m, 2H, Ar-H), 9.36 (s, 1H, CH triazole). C17H15N5SO (337.4) Calcd.: C,
60.52; H, 4.48; N, 20.76; S, 9.50. Found: C, 60.42; H, 4.22; N, 20.69; S, 9.33.

Molecules 2010, 15
2662
7-Methyl-3-phenyl-1,2,6,7,8,9-hexahydro-3H-pyrido[4',3':4,5]thieno[2,3-d][1,2,4]triazolo[1,5-a] pyri
midine-2,10-dione (20). A mixture of the thienopyrimidine compound 6 (0.65 g, 2 mmol) and N,N`-
carbonyldimidazole (CDI) (0.64 g, 4 mmol) in dry dioxane (20 mL) was refluxed for 6 h. After
cooling, the solvent was removed and the residue was triturated with cold water. The solid product was
filtered, dried and recrystallized from water/ethanol (2:3) to give brown crystals, yield 0.61 g (86%),
m.p. 280–282 ºC. IR: υ cm-1 = 3,200 (NH), 3,050 (CH arom.), 2,910 (CH aliph.), 1,720 (C=O triazolo),
1
1,680 (C=O pyrimidinone). H-NMR (DMSO-d6): δ = 2.34 (s, 3H, NCH3), 2.48 (s, 2H, CH2), 2.87
(t, 2H, CH2), 3.53 (t, 2H, CH2), 7.43 (m, 2H, Ar-H), 7.53 (m, 3H, Ar-H), 11.95 (bs, 1H, NH).
C17H15N5SO2 (353.40) Calcd.: C, 57.78; H, 4.28; N, 19.82; S, 9.07; Found: C, 57.69; H, 4.07; N,
19.91; S, 8.89.
N-(7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-on-3-
yl)acetamide (24). To a solution of 6 (0.33 g, 1 mmol), in pyridine (5 mL), acetyl chloride (0.08 mL,
1.1 mmol) was added with stirring. The reaction mixture was stirred at room temperature for 7 h
further. After removal of the solvent, the solid residue was treated with cold diluted HCl, filtered,
washed with water and recrystallized from ethanol/dioxane (2:3) to give fine yellow crystals, yield
0.27 g (73%), m.p. 143–145 ºC. IR: υ cm-1 = 3,390 (NH), 3,050 (CH arom.), 2,910 (CH aliph.), 1,730
1
(C=O), 1,690 (C=O). H-NMR (CDCl3): δ = 2.10 (s, 3H, COCH3), 2.50 (s, 3H, NCH3), 2.73 (t, 2H,
CH2), 3.00 (t, 2H, CH2), 3.57 (s, 2H, CH2), 4.73 (bs, 2H, NH), 7.37 (m, 2H, Ar-H); 7.47 (m, 3H, Ar-
H). C18H19N5SO2 (369.44) Calcd.: C, 58.52; H, 5.18; N, 18.96; S, 8.68. Found: C, 58.35; H, 4.99; N,
18.69; S, 8.41.
7-Methyl-2-phenylamino-3-(2-oxopropylamino)-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]
pyrimidin-4-one (25). A mixture 6 (0.66 g, 2 mmol), and chloroacetone (0.19 mL, 2.2 mmol) in
ethanol (10 mL) was heated under reflux for 3 h. After cooling, the solvent was removed in vacuo and
the solid residue obtained was recrystallized from ethanol to give white crystals, yield 0.42 g (55%),
m.p. 278–280 ºC. IR: υ cm-1 = 3,300 (NH), 3,100 (CH arom.), 2,910 (CH aliph.), 1,720 (C=O), 1,680
1
(C=O). H-NMR (CDCl3): δ = 1.88 (s, 3H, COCH3), 2.10 (s, 3H, NCH3), 2.43 (t, 2H, CH2), 2.66 (t,
2H, CH2), 2.96 (s, 2H, CH2), 3.54 (s, 2H, CH2CO), 7.37 (m, 2H, Ar-H), 7.50 (m, 3H, Ar-H), 9.03 (bs,
1H, NH), 9.72 (s, 1H, NH). C19H21N5O2S (383.47) Calcd.: C, 59.51; H, 5.52; N, 18.26; S, 8.36. Found:
C, 59.41; H, 5.35; N, 17.98; S, 8.39.
Ethyl
3-(7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-
on-3-ylimino)butanoate (26). A mixture of 6 (0.82 g, 2.5 mmol) and ethyl acetoacetate (0.33 mL,
2.5 mmol), and sodium acetate (0.82 g, 10 mmol) in absolute ethanol (20 mL) was heated under reflux
for 5 h. The reaction mixture was then triturated with diethyl ether (10 mL) and the precipitate thus
formed was collected and recrystallized from ethanol to give buff crystals, yield 0.56 g (68%),
m.p. 150–152 ºC. IR: υ cm-1 = 3,350 (NH), 3,050 (CH arom.), 2,910 (CH aliph.), 1,730 (C=O), 1,680
(C=O).1H-NMR (CDCl3): δ = 1.17 (t, J = 7.1 Hz, 3H, CH2CH3), 1.93 (s, 3H, CH3), 2.48 (s, 3H,
NCH3), 2.81 (t, 2H, CH2), 3.02 (t, 2H, CH2), 3.39 (s, 2H, CH2), 3.65 (s, 2H, CH2), 4.09 (q, J = 7.1 Hz,
2H, CH2CH3), 7.43 (m, 5H, Ar-H), 8.41 (bs, 1H, NH). C22H25N5O3S (439.53) Calcd.: C, 60.12; H,
5.73; N, 15.93; S, 7.30. Found: C, 60.18; H, 5.05; N, 15.95; S, 6.40.

Molecules 2010, 15
2663
Ethyl
3-(7-methyl-2-phenylamino-5,6,7,8-tetrahydro-3H-pyrido[4',3':4,5]thieno[2,3-d]pyrimidin-4-
on-3-ylamino)-3-oxopropanoate (27). A mixture of 6 (1.64 g, 5 mmol) and diethyl malonate (5 mL)
was heated under reflux for 5 h. After cooling, the excess of diethylmalonate was removed in vacuo
and the solid residue was recrystallized from ethanol to give white platelets, yield: 1.3 g, (59%),
m.p. 194–196 ºC. IR: υ cm-1 = 3,300 (NH ), 3,050 (CH arom.), 2,950 (CH aliph.), 1,730 (C=O), 1,690
1
(C=O), 1,680 (C=O). H-NMR (CDCl3): δ = 1.24 (t, 3H, J = 7.1 Hz, CH2CH3), 2.45 (s, 3H, NCH3),
2.70 (t, 2H, CH2), 3.30 (t, 2H, CH2), 3.33 (s, 2H, CH2), 3.57 (s, 2H, CH2), 4.16 (q, J = 7.1 Hz, 2H,
CH2CH3), 7.36 (m, 2H, Ar-H), 7.52 (m, 3H, Ar-H), 8.98 (bs, 1H, NH), 10.09 (bs, 1H, NH).
C21H23N5O4S (441.51) Calcd.: C, 57.13; H, 5.25; N, 15.86; S, 7.26. Found: C, 57.05; H, 4.98; N,
15.65; S, 6.99.
Ethyl 4-amino-9-methyl-12-oxo-5-phenyl-8,9,10,11-tetrahydro-5H-pyrido[4'',3'':4',5']thieno[2',3':4,5]
pyrimido[1,2-b][1,2,4]triazepine-3-carboxylate (28). A mixture of 6 (0.33 g, 1 mmol) and ethyl
ethoxymethylenecyanoacetate (0.17 g, 1 mmol) in absolute ethanol (10 mL) was heated under reflux
for 8 h. After cooling, the solvent was removed under reduced pressure and the solid residue obtained
was recrystallized from ethanol/dioxane (3:1) as yellow crystals, yield: 0.39 g (87%),
m.p. 214–217 ºC. IR: υ cm-1 = 3,400, 3,290 (NH2), 3,100 (CH arom.), 2,910 (CH aliph.), 1,680 (C=O),
1,630 (C=O). 1H-NMR (DMSO-d6): δ = 1.14 (t, 3H, J = 7.1 Hz, CH2CH3), 2.44 (s, 3H, NCH3), 2.67 (t,
2H, CH2), 3.02 (t, 2H, CH2), 3.64 (s, 2H, CH2) 4.09 (q, 2H, J = 7.1 Hz, CH2CH3), 6.08 (bs, 2H, NH2),
7.26 (m, 5H, Ar-H), 8.29 (s, 1H, CH triazepine). MS: m/z (rel. int.) 450 (M+, 87%), 408 (22), 407 (40),
217.91 (100), 361 (29), 337 (85), 336 (45), 294 (98), 293 (19), 267 (34), 254 (13), 253 (55), 163 (13),
122 (17), 94 (13), 77 (34.6), 64 (11), 58 (27), 50.97 (13), 52 (19), 51 (16). C22H22N6O3S (450.51).
Calcd.: C, 58.65; H, 4.92; N, 18.55; S, 7.12. Found: C, 58.48; H, 4.95; N, 18.40; S, 6.99.
4-Amino-9-methyl-12-oxo-5-phenyl-8,9,10,11-tetrahydro-5H-pyrido[4'',3'':4',5']thieno[2',3':4,5] pyrim
ido[1,2-b][1,2,4]triazepin-3-carbonitrile (29). A mixture of 6 (0.33 g, 1 mmol) and
ethoxymethylenemalononitrile (0.13 g, 1 mmol) in absolute ethanol (10 mL) was heated under reflux
for 4 h. After cooling, the solvent was removed in vacuo and the solid residue was recrystallized from
ethanol/dioxane (2:1) to give reddish crystals, yield: 0.33 g (82%), m.p. 214–216 ºC. IR:
υ cm-1 = 3,400, 3,300 (NH2), 3,100 (CH arom.), 2,910 (CH aliph.), 2,210 (CN), 1,680 (C=O). 1H-NMR
(CDCl3): δ = 2.75 (s, 3H, NCH3), 2.86 (t, 2H, CH2), 3.12 (t, 2H, CH2), 3.24 (s, 2H, CH2), 5.60 (bs, 2H,
NH2), 7.35 (m, 5H, Ar-H), 8.59 (s, 1H, CH triazepine). C20H17N7OS (403.46). Calcd.: C, 59.54; H,
4.25; N, 24.30; S, 7.95. Found: C, 59.35; H, 4.15; N, 24.03; S, 7.88.
5-Phenyl-2,4,9-trimethyl-8,9,10,11-tetrahydro-5H-pyrido[4'',3'':4',5']thieno[2',3':4,5]pyrimido[1,2-b]
[1,2,4]triazepin-12-one (30). Compound 6 (0.33 g, 1 mmol) in excess acetyl acetone (6 mL) was
heated under reflux for 4 h, then the reaction mixture was concentrated and left to cool. The solid
precipitate was triturated with ethanol, filtered and recrystallized from isopropanol to give buff
crystals, yield 0.24 g (61%), m.p. 196–198 ºC. IR: υ cm-1 = 2,900 (CH aliph.), 1,690 (C=O). 1H-NMR
(CDCl3): δ = 2.11 (s, 3H, CH3), 2.31 (s, 3H, CH3), 2.51 (s, 3H, NCH3), 2.90 (t, 2H, CH2), 3.21 (t, 2H,

Molecules 2010, 15
2664
CH2), 3.71 (s, 2H, CH2), 5.81 (s, 1H, CH triazepine), 7.26 (m, 5H, Ar-H). C21H21N5OS (391.49)
Calcd.: C, 64.43; H, 5.41; N, 17.89; S, 8.19. Found: C, 64.25; H, 5.35; N, 17.82; S, 8.15.
4. Conclusions
New pyrido[4',3':4,5]thieno[2,3-d]pyrimidines were obtained using ethyl 2-amino-6-methyl-4,5,6,7-
tetrahydrothieno[2,3-c]pyridine-3-carboxylate (1) as starting material. The reaction of 1 with
phenylisothiocyanate in boiling ethanol afforded the thiourea derivative 5 as the key intermediate
which was reacted under different cyclization reaction conditions to form different
pyridothienopyrimidine derivatives. Moreover, the cyclization reactions of the intermediate 6 led to
pyrido[4',3':4,5]thieno[2,3-d]triazolo[1,5-a]pyrimidine or pyrido[4'',3'':4',5']thieno[2',3':4,5]pyrimido-
[1,2-b][1,2,4]triazepine derivatives. In continuation of our program directed toward the preparation of
new bioactive compounds as anti-infectious agents [27–31], the pharmacological evaluation of these
synthesized compounds is under active investigation in this area.
Acknowledgements
This work was supported by the Centre National de la Recherche Scientifique, the Assiut University
and the Université de la Méditerranée.
References and Notes
1. Steiner, G.; Schellhaas, K.; Lubisch, W.; Holzenkamp, U.; Starck, D.; Knopp, M.; Szabo, L.;
Emling, F.; Garcia-Ladona, F.J.; Hofmann, H.-P.; Unger, L. Preparation of thienopyrimidines for
use in the prophylaxis and therapy of cerebral ischemia. German Patent 19900545, 1999; [Chem.
Abstr. 2000, 133, 89541].
2. Steiner, G.; Schellhaas, K; Szabo, L.; Behl, B.; Garcia-Ladona, F.J.; Unger, L. Preparation of
5,6,7,8-tetrahydropyrido[4’,3’:4,5]thieno[2,3-d]pyrimidin-4(3H)-ones for the treatment of
cerebral ischemia. Patent WO 2002002569, 2002; [Chem. Abstr. 2002, 136, 85831].
3. Abbott GmbH & Co. Kg, Germany. 3-Substituted 3,4-dihydrothieno[2,3-d]pyrimidine-4-one
derivatives, production and use thereof. German Patent 10259382, 2002; [Chem. Abstr. 2004, 141,
89095].
4. Steiner, G.; Lubisch, W.; Bach, A.; Emling, F.; Wicke, K.; Teschendorf, H-J.; Behl, B.; Kerrigan,
F.; Cheetham, S. Preparation of 3-substituted pyrido[4’,3’:4,5]thieno[2,3-d]pyrimidines as 5-HT1A
receptor antagonists and serotonin reuptake inhibitors. German Patent 19636769, 1996; [Chem.
Abstr. 1998, 128, 217381].
5. Sakr, S.M.; Kadry, A.M.; El-Sayed, A.M.M.; Al Ashmawi, M.I. Condensed thieno[2,3-d]
pyrimidines: synthesis and biological activity. Egypt. J. Chem. 1992, 34, 147–155.
6. Eichenberger, K.; Schmidt, P.; Schweizer, E. Antimalarial 5,6,7,8-tetrahydro-
pyrido[4’,3’:4,5]thieno[2,3-d]pyrimidins. German Patent 1937459, 1969; [Chem. Abstr. 1970, 72,
100743].
7. Kling, A.; Lange, U.E.W.; Mack, H.; Bakker, M.H.M.; Drescher, K.U.; Hornberger, W.;
Hutchins, C.W.; Möller, A.; Müller, R.; Schmidt, M.; Unger, L.; Wicke, K.; Schellhaas, K.;

Molecules 2010, 15
2665
Steiner, G. Synthesis and SAR of highly potent dual 5-HT1A and 5-HT1B antagonists as potential
antidepressant drugs. Bioorg. Med. Chem. Lett. 2005, 15, 5567–5573.
8. Ahmed. E.K. Synthesis of 3-substituted pyrido[4',3':4,5]thieno[2,3-d]pyrimidines and related
fused thiazolo derivatives. Heteroatom Chem. 2003, 14, 201–207.
9. Lalezari, I.; Jabari-Sahbari, M.H. New polyheterocyclic series based on 4,5,6,7-
tetrahydrothieno[2,3-c]pyridine (1). J. Heterocycl. Chem. 1978, 15, 873–875.
10. Robba, M.; Touzot, P.; El-Kashef, H. [1]Benzothienopyrimidines. I. Study of 3H-
benzothieno[3,2-d]pyrimid-4-one. J. Heterocycl. Chem. 1980, 17, 923–928.
11. El-Kashef, H.; Rault, S.; Cugnon de Sevricourt, M.; Touzot, P.; Robba, M.
[1]Benzothienopyrimidines. II. Study of the electrophilic substitutions of [1]benzothieno[3,2-
d]pyrimidine and [1]benzothieno[3,2-d]pyrimidin-4(3H)-one. J. Heterocycl. Chem. 1980, 17,
1399–1404.
12. El-Dean, A.M.K.; El-Kashef, H.S. Synthesis of some imidazopyrazolopyrimidine derivatives.
Pharmazie 1996, 51, 155–158.
13. Bakhite, E.A.; Geies, A.A.; El-Kashef, H.S. Synthesis of novel pyrrolylthieno[2,3-d]pyrimidines
and related pyrrolo[1'',2'':1',6']pyrazino[2',3':4,5]thieno[2,3-d]pyrimidines. Phosphorus Sulfur
Silicon Relat. Elem. 2002, 177, 303–323.
14. Baraldi, P.G.; Fruttarolo, F.; Tabrizi, M.A.; Preti, D.; Romagnoli, R.; El-Kashef, H.; Moorman,
A.; Varani, K.; Gessi, S.; Merighi, S.; Borea, P.A. Design, synthesis, and biological evaluation of
C9- and C2-substituted pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines as new A2A and A3
adenosine receptors antagonists. J. Med. Chem. 2003, 46, 1229–1241.
15. Baraldi, P.G.; El-Kashef, H.; Farghaly, A.; Vanelle, P.; Fruttarolo, F. Synthesis of new
pyrazolo[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidines and related heterocycles. Tetrahedron 2004, 60,
5093–5104.
16. Baraldi, P.G.; Tabrizi, M.A.; Romagnoli, R.; El-Kashef, H.; Preti, D.; Bovero, A.; Fruttarolo, F.;
Gordaliza, M.; Borea, P.A. Pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidine template: organic and
medicinal chemistry approach. Curr. Org. Chem. 2006, 10, 259–275.
17. Farghaly, A.; El-Kashef, H. Synthesis of imidazo[1,2-c]pyrazolo[4,3-e]pyrimidines derived from
indole and related heterocycles. Monatsh. Chem. 2006, 137, 1195–1202.
18. Baraldi, P.G.; Fruttarolo, F.; Tabrizi, M.A.; Romagnoli, R.; Preti, D.; Ongini, E.; El-Kashef, H.;
Carrion, M.D.; Borea, P.A. Synthesis of a new series of pyrazolo[1,5-a]pyrimidines structurally
related to zaleplon. J. Heterocycl. Chem. 2007, 44, 355–361.
19. Baraldi, P.G.; Romagnoli, R.; El-Kashef, H.; Tabrizi, M.A.; Preti, D.; Pavani, M.G.; Zanella, L.;
Fruttarolo, F. Pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidines and linked heterocycles as
template for the adenosine receptor antagonism: medicinal chemistry approach and SAR
considerations. Targets Heterocycl. Syst. Chem. Prop. 2006, 10, 175–196.
20. Roubaud, C.; Vanelle, P.; Maldonado, J.; Crozet, M.P. Synthesis and unimolecular radical
nucleophilic substitution reactions in the 3-nitroimidazo[1,2-a]pyrimidine series. Tetrahedron
1995, 51, 9643–9656.
21. El-Kashef, H.S.; El-Emary, T.I.; Gasquet, M.; Timon-David, P.; Maldonado, J.; Vanelle P. New
pyrazolo[3,4-b]pyrazines: synthesis and biological activity. Pharmazie 2000, 55, 572–576.

Molecules 2010, 15
2666
22. Rathelot, P.; Azas, N.; El-Kashef, H.; Delmas, F.; Di Giorgio, C.; Timon-David, P.; Maldonado,
J.; Vanelle P. 1,3-Diphenylpyrazoles: synthesis and antiparasitic activities of azomethine
derivatives. Eur. J. Med. Chem. 2002, 37, 671–679.
23. Vanelle, P.; Maldonado, J.; Madadi, N.; Gueiffier, A.; Chapat, J.-P.; Crozet, M.P. SRN1 reactions
in imidazo[1,2-a]pyridine series. Tetrahedron Lett. 1990, 31, 3013–3016.
24. El-Subbagh, H. Synthesis and antitumor activity of certain thienopyridine and
pyridothienopyrimidine derivatives. S. Pharm. J. 1997, 5, 23–28.
25. El-Subbagh H. Antitumor screening of new cyclopenteno[b]thiophene, benzo[b]thiophene,
thieno[2,3-c]pyridine and pyrido[4',3':4,5]thieno[2,3-d]pyrimidine analogs. S. Pharm. J. 1999, 7,
34–38.
26. El-Baih, F.E.M.; Al-Blowy, H.A.S.; Al-Hazimi, H.M. Synthesis of some thienopyrimidine
derivatives. Molecules 2006, 11, 498–513.
27. Vanelle, P.; De Meo, M.P.; Maldonado, J.; Nouguier, R.; Crozet, M.P.; Laget, M.; Dumenil, G.
Genotoxicity in oxazolidine derivatives—Influence of the nitro group. Eur. J. Med. Chem. 1990,
25, 241–250.
28. Vanelle, P.; Crozet, M.P.; Maldonado, J.; Barreau, M. SRN1 synthesis of new 5-nitroimidazoles
highly active against protozoa and anaerobes. Eur. J. Med. Chem. 1991, 26, 167–178.
29. Jentzer, O.; Vanelle, P.; Crozet, M.P.; Maldonado, J.; Barreau, M. New 5-nitroimidazoles bearing
lactame nucleus – Synthesis and antibacterial properties. Eur. J. Med. Chem. 1991, 26, 687–697.
30. Delmas, F.; Gasquet, M.; Timon-David, P.; Madadi, N.; Vanelle, P.; Vaille, A.; Maldonado, J.
Synthesis and in vitro anti-protozoan activity of new 5-nitrothiophene oxime ether derivatives.
Eur. J. Med. Chem. 1993, 28, 23–27.
31. Upcroft, J.A.; Dunn, L.A.; Wright, J.M.; Benakli, K.; Upcroft, P.; Vanelle, P. 5-Nitroimidazole
drugs effective against metronidazole-resistant. Trichomonas vaginalis and Giardia duodenalis
Antimicrob. Agents Chemother. 2006, 50, 344–347.
Sample Availability: Available from the authors.
© 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).