A mild and efficient synthesis of new 3-phenyl-thienotriazolopyrimidine derivatives using iodobenzene diacetate

Article abstract of DOI:10.3987/COM-08-11465

New 3-phenylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine 9a-i and 3-phenylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine 10a-i derivatives were easily synthesized at rt in high yield by the oxidative cyclization of thienopyrimidinyl hydrazones using iodobenzene diacetate.

Full text of DOI:10.3987/COM-08-11465

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HETEROCYCLES, Vol. 75, No. 12, 2008, pp. 3091 - 3097. © The Japan Institute of Heterocyclic Chemistry
Received, 15th June, 2008, Accepted, 14th July, 2008, Published online, 17th July, 2008. COM-08-11465
A MILD AND EFFICIENT SYNTHESIS OF NEW 3-PHENYL-
THIENOTRIAZOLOPYRIMIDINE DERIVATIVES USING
IODOBENZENE DIACETATE
Byeoung Sun Joe, Hoon Young Son, and Yang-Heon Song*
Department of Chemistry, Mokwon University, Daejeon 302-729, Republic of
Korea, e-mail address: yhsong@mokwon.ac.kr
Abstract – New 3-phenylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine 9a-i and
3-phenylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine 10a-i derivatives were
easily synthesized at rt in high yield by the oxidative cyclization of
thienopyrimidinyl hydrazones using iodobenzene diacetate.
INTRODUCTION
Various thienopyrimidines have been synthesized and investigated in relation with their biological and
pharmacological activities. Recently, a novel class of thieno[3,2-d]pyrimidine has been identified as
potent inhibitors of VEGF receptor-2 kinase, which is a key component of the signaling pathway
responsible for the sprouting and maturation of new blood vessels from tumors.1 New
thieno[2,3-d]pyrimidine derivatives were also prepared and studied as selective and potent ligands for the
5-HT3 receptor.2 Furthermore, derivatives of 1,2,4-triazole have also received considerable attention
because of their therapeutic importance. The 1,2,4-triazole moiety is present, for example, in certain
antiviral,3 antiasthmatic4 and antibacterial5 drugs.
Therefore, we have planned to synthesize new 3-phenylthienotriazolopyrimidine derivatives 9 and 10 that
are fused with thienopyrimidine and 1,2,4-triazole moiety, which may have a broad range of biological
activities.
Many substituted thienotriazolopyrimidine derivatives have been prepared since the first synthesis of
thienotriazolopyrimidine by Robba et al.6 But, literature survey showed that only two 3-substituted
thienotriazolopyrimidine derivatives have been reported.6
As a continuation of our previous work on thienopyrimidines,7 we wish to report herein the synthesis of
new 3-phenylthienotriazolopyrimidine derivatives using iodobenzene diacetate in oxidative cyclization
reaction.

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HETEROCYCLES, Vol. 75, No. 12, 2008
O
CN
S
NH2
NH2
S
HCO2H
reflux
NH2
HC(OEt)3
CN
2
1
reflux
O
S
NH
N
N
R
N
R
N
N
S
S
N=CHOEt
N
N
4
3
i)POCl3
ii)N2H4
S
N
reflux
N
N2H4
reflux
10
9
NHNH2
N
NHNH2
S
N
N
PhI(OAc)2
rt
PhI(OAc)2
rt
N
S
R
R
5
6
reflux
NHN=CH
N
NHN=CH
N
reflux
OHC
OHC
R
S
R
p-TsOH(cat.)/
piperidine(cat.)/
EtOH
toluene
S
7
8
N
N
R: a; H, b; 4-Cl, c; 4-Me, d; 4-MeO, e; 4-Br,
f; 3-Cl, g; 3-Me, h; 3-Br, i; 2-MeO
Scheme 1
RESULTS AND DISCUSSION
The oxidative cyclization of pyrimidine hydrazone to triazolopyrimidine compound has been usually
accomplished using bromine/acetic acid or thionyl chloride. These reagents are often associated with
several drawbacks such as toxicity, poor yield, and need of high reaction temperature. Iodobenzene
diacetate as one of organohypervalent iodine reagent has been used for many chemical transformations
due to its low toxicity, ready availability and ease of handling.8
The target compounds 9 and 10 were prepared as shown Scheme 1 through a series of reactions starting
with 2-aminothiophene-3-carbonitrile (1) or ethyl 3-amino-thiophene-2-carboxamide (2)7 which were
obtained by the method of Gewald.9 Cyclization of 1 and 2 with triethyl orthoformate or formic acid
afforded N-(3-cyanothiophen-2-yl)formimidic acid ethyl ester (3) or 3H-thieno[3,2-d] pyrimidin-4-one
(4), respectively. Reaction of 3 with hydrazine hydrate gave 4-hydrazinothieno[2,3-d]pyrimidine (5),
while treatment of 4 with phosphorus oxychloride in the presence of dimethylaniline as catalyst led to
4-chlorothieno[3,2-d]pyrimidine which then underwent nucleophilic substitution with hydrazine hydrate
resulting in 4-hydrazinothieno[3,2-d]pyrimidine (6). The hydrazone derivatives, 7a-i or 8a-i, were
synthesized by condensation of 5 or 6 with the corresponding benzaldehydes in toluene in the presence of

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3093
catalytic amount of p-TsOH. For 8a-i, marked improvement in yield could be made when the reaction
took place in absolute EtOH in the presence of few drops of piperidine as catalyst.
The oxidative cyclization of 7a-i and 8a-i to 3-phenylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine 9a-i
and 3-phenylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine 10a-i derivatives, respectively, was achieved
easily using iodobenzene diacetate. For instance, when a solution of 7a or 8a in dichloromethane was
treated with iodobenzene diacetate at rt for 1 h, rapid reaction occurred to give 9a or 10a as crystalline
solid in 75–85% yield.
The mechanism of cyclization reaction is not certain, but it is assumed that the reaction took place via
cyclizaton of intermediate through the electrophilic attack of iodobenzene diacetate on 7, followed by
elimination of iodobenzene and acetic acid (Scheme 2).
Ph
AcO
AcO
Ph
I
R
R
I
N
N
NHN=CH
AcO
N
N
C
H
N
S
S
N
7
R
R
+
N
_
+
N
N
N
_
9
N
N
S
S
N
N
intermediate
Scheme 2
The structures of all compounds were confirmed by elemental analyses and spectroscopic studies.
In conclusion, the facile and mild synthesis of new 3-phenylthienotriazolopyrimidine derivatives using
iodobenzene diacetate in oxidative cyclization reaction was developed.
EXPERIMENTAL
Melting points were determined in capillary tubes on Büchi apparatus and are uncorrected. Each
compound of the reactions was checked on thin-layer chromatograpohy of Merck Kieselgel 60F254 and
1
purified by column chromatography using Merck silica gel (70-230 mesh). The H NMR spectra were
recorded on Bruker DRX-300 FT-NMR spectrometer (300 MHz) with Me4Si as internal standard and

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chemical shifts are given in ppm (δ). Electron ionization mass spectra were recorded on a HP 59580 B
spectrometer. Elemental analyses were performed on a Carlo Erba 1106 elemental analyzer.
General procedure for the preparation of N-substituted benzylidene-N’-thieno[2,3-d]pyrimidin-4-yl-
hydrazine 7a-i and N-substituted benzylidene-N’-thieno[3,2-d]pyrimidin-4-ylhydrazine 8a-i
derivatives:
A mixture of 4-hydrazinothieno[2,3-d]pyrimidine (5) (0.1 mol), each benzaldehyde (0.12 mol) and
p-TsOH monohydrate (0.3 g) in toluene (200 mL) was stirred and refluxed for 24 h with a Dean-Stark
trap. The reaction mixture was cooled in an ice-water bath and the solid which had formed was collected
by filtration, washed with Et2O and crystallized to give 7a-i.
A mixture of 4-hydrazinothieno[3,2-d]pyrimidine (6) (0.1 mol), each benzaldehyde (0.12 mol) and
piperidine (0.1 g) in absolute EtOH (100 mL) was stirred and refluxed for 24 h. The solvent was
evaporated and the residue was purified by recrystallization in CHCl3 or column chromatography in
EtOAc-hexane to give 8a-i.
General procedure for the preparation of 3-phenylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine 9a-i
and 3-phenylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine 10a-i derivatives:
To a solution of N-substituted benzylidene-N’-thieno[2,3-d]pyrimidin-4-yl hydrazine 7a-i or
N-substituted benzylidene-N’-thieno[3,2-d]pyrimidin-4-yl hydrazine 8a-i (0.01 mol) in dry CH2Cl2 (20
mL), iodobenzene diacetate (0.01 mol) was slowly added. The reaction mixture was stirred for 1 h at rt.
After evaporation the precipitate was filtered and recrystallized from CHCl3.
3-Phenylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9a):
1
85% Yield, mp 206 - 207 °C; H NMR (CDCl3): δ (ppm) 9.00 (s, 1H, H-5), 7.97 (d, J = 5.9 Hz, 1H,
thiophene H-8), 7.87 (d, 2H, H-2’ and H-6’), 7.72 (d, J = 5.9 Hz, 1H, H-9), 7.63 (m, 3H, H-3’,H-4’ and
H-5’); MS: (m/z) 252 (M+), 149, 122. Anal. Calcd for C13H8N4S: C, 61.89; H, 3.20, N, 22.21. Found: C,
61.80; H, 3.14; N, 22.30.
3-(4-Chlorophenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9b):
82% Yield, mp 269 - 270 °C; 1H NMR (CDCl3): δ 8.97 (s, 1H, H-5), 7.97 (d, J = 5.9 Hz, 1H, H-8), 7.86
(d, 2H, H-3’ and H-5’), 7.74 (d, J = 5.9 Hz, 1H, H-9), 7.65 (d, 2H, H-2’and H-6’); MS: (m/z) 286 (M+),
152, 134. Anal. Calcd for C13H7ClN4S: C, 54.45; H, 2.46, N, 19.54. Found: C, 54.39; H, 2.40; N, 19.62.
3-p-Tolylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9c):
75% Yield, mp 195 - 196 °C; 1H NMR (CDCl3): δ 8.99 (s, 1H, H-5), 7.97 (d, J = 6.0 Hz, 1H, H-8), 7.78
(d, 2H, H-2’and H-6’), 7.71 (d, J = 5.9 Hz, 1H, H-9), 7.46 (d, 2H, H-3’ and H-5’), 2.49 (s, 3H, methyl);
MS: (m/z) 266 (M+), 149, 132. Anal. Calcd for C14H10N4S: C, 63.14; H, 3.78, N, 21.04. Found: C, 62.99;
H, 3.68; N, 21.92.

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3-(4-Methoxyphenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9d):
83% Yield, mp 239 - 240 °C; 1H NMR (CDCl3): δ 8.97 (s, 1H, H-5), 7.98 (d, J = 6.0 Hz, 1H, t H-8), 7.79
(d, 2H, H-2’and H-6’), 7.71 (d, J = 5.9 Hz, 1H, H-9), 7.17 (d, 2H, H-3’ and H-5’), 3.93 (s, 3H, methyl);
MS: (m/z) 282 (M+), 151, 132. Anal. Calcd for C14H10N4OS: C, 59.56; H, 3.57, N, 19.85. Found: C,
60.48; H, 3.62; N, 20.12.
3-(4-Bromophenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9e):
80% Yield, mp 258 - 259 °C; 1H NMR (CDCl3): δ 8.97 (s, 1H, H-5), 7.96 (d, J = 6.0 Hz, 1H, H-8), 7.79 -
7.71 (m, 4H, H-2’, H-3’, H-5’ and H-6’), 7.61 (d, J = 6.0 Hz, 1H, H-9); MS: (m/z) 331 (M+), 251, 149,
135. Anal. Calcd for C13H7BrN4S: C, 47.15; H, 2.13, N, 16.92. Found: C, 46.98; H, 2.22; N, 17.03.
3-(3-Chlorophenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9f):
79% Yield, mp 242 - 243 °C; 1H NMR (CDCl3): δ 9.00 (s, 1H, H-5), 7.98 (d, J = 6.0 Hz, 1H, H-8), 7.91
(s, 1H, H-2’), 7.74 - 7.72 (m, 2H, H-9, H-4’), 7.60 - 7.56 (m, 2H, H-5’ and H-6’); MS: (m/z) 286 (M+),
149, 135, 122. Anal. Calcd for C13H7ClN4S: C, 54.45; H, 2.46, N, 19.54. Found: C, 54.88; H, 2.32; N,
19.39.
3-m-Tolylthieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9g):
70% Yield, mp 198 - 199 °C; 1H NMR (CDCl3): δ 8.62 (s, 1H, H-5), 7.99 (d, J = 6.0 Hz, 1H, H-8), 7.82
(d, 1H, H-6’), 7.70 (d, J = 6.0 Hz, 1H, H-9), 7.68 (s, 1H, H-2’), 7.30 (t, 1H, H-5’), 7.26 (d, 1H, H-4’);
MS: (m/z) 265 (M+-H), 149, 132. Anal. Calcd for C14H10N4S: C, 63.14; H, 3.78, N, 21.04. Found: C,
62.88; H, 3.64; N, 21.43.
3-(3-Bromophenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9h):
84% Yield, mp 262 - 263 °C; 1H NMR (CDCl3): δ 9.00 (s, 1H, H-5), 8.06 (s, 1H, H-2’) 7.98 (d, J = 6.0
Hz, 1H, H-8), 7.84 - 7.77 (m, 3H, H-9, H-4’ and H-6’), 7.56 (t, 1H, H-5’); MS: (m/z) 331 (M+), 196, 148.
Anal. Calcd for C13H7BrN4S: C, 47.15; H, 2.13, N, 16.92. Found: C, 46.88; H, 2.31; N, 17.01.
3-(2-Methoxy phenyl)thieno[3,2-e][1,2,4]triazolo[4,3-c]pyrimidine (9i):
80% Yield, mp 162 - 164 °C; 1H NMR (CDCl3): δ 9.01 (s, 1H, H-5), 7.96 (d, J = 6.0 Hz, 1H, H-8), 7.71
(d, J = 5.9 Hz, 1H, H-9), 7.64 - 7.55 (m, 2H, H-4’and H-6’), 7.50 (t, 1H, H-4’) 7.41 (d, 1H, H-3’), 2.50 (s,
3H, methyl); MS: (m/z) 282 (M+). Anal. Calcd for C14H10N4OS: C, 59.56; H, 3.57, N, 19.85. Found: C,
59.88; H, 3.74; N, 20.26.
3-Phenylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10a):
75% Yield, mp 156 - 157 °C; 1H NMR (CDCl3): δ 9.30 (s, 1H, H-5), 8.34 (m, 2H, H-2’ and H-6’), 7.87 (d,
J = 5.9 Hz, 1H, thiophene H-8), 7.66 (d, J = 5.9 Hz, 1H, H-7), 7.54 - 7.45 (m, 3H, H-3’,H-4’ and H-5’);
MS: (m/z) 252 (M+), 149, 118. Anal. Calcd for C13H8N4S: C, 61.89; H, 3.20, N, 22.21. Found: C, 62.30;
H, 3.26; N, 22.50.

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3-(4-Chlorophenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10b):
77% Yield, mp 264 – 265 °C; 1H NMR (CDCl3): δ 9.02 (s, 1H, H-5), 7.87 - 7.79 (m, 3H, H-8, H-3’ and
H-5’), 7.65 - 7.60(m, 3H, H-7, H-2’ and H-6’); MS: (m/z) 286 (M+), 134. Anal. Calcd for C13H7ClN4S: C,
54.45; H, 2.46, N, 19.54. Found: C, 54.29; H, 2.41; N, 19.68.
3-p-Tolylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10c):
70% Yield, mp 206 – 208 °C; 1H NMR (CDCl3): δ 9.20 (s, 1H, H-5), 8.23 (m, 2H, H-2’ and H-6’), 7.86(d,
J = 5.9 Hz, 1H, H-8), 7.63 (d, J = 6.0 Hz, 1H, H-7), 7.35 (m, 2H, H-3’and H-5’); MS: (m/z) 266 (M+),
131, 91. Anal. Calcd for C14H10N4S: C, 63.14; H, 3.78, N, 21.04. Found: C, 62.85; H, 3.71; N, 21.35.
3-(4-Methoxyphenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10d):
70% Yield, mp 142 – 143 °C; 1H NMR (CDCl3): δ 9.29 (s, 1H, H-5), 8.25 (m, 2H, H-2’ and H-6’), 7.87
(d, J = 5.9 Hz, 1H, H-8), 7.64 (d, J = 6.0 Hz, 1H, H-7), 7.05 (m, 2H, H-3’and H-5’), 3.90 (s, 3H, methyl);
MS: (m/z) 282 (M+), 132. Anal. Calcd for C14H10N4OS: C, 59.56; H, 3.57, N, 19.85. Found: C, 60.20; H,
3.68; N, 20.22.
3-(4-Bromophenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10e):
78% Yield, mp 168 – 169 °C; 1H NMR (CDCl3): δ 9.01 (s, 1H, H-5), 7.96 (d, J = 6.0 Hz, 1H, H-8), 7.75 -
7.66 (m, 4H, H-2’, H-3’, H-5’ and H-6’), 7.65 (d, J = 6.0 Hz, 1H, H-7); MS: (m/z) 331 (M+). Anal. Calcd
for C13H7BrN4S: C, 47.15; H, 2.13, N, 16.92. Found: C, 46.84; H, 2.29; N, 17.26.
3-(3-Chlorophenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10f):
81% Yield, mp 158 – 159 °C; 1H NMR (CDCl3): δ 9.04 (s, 1H, H-5), 7.91 (d, J = 6.0 Hz, 1H, H-8), 7.81
(s, 1H, H-2’), 7.75 - 7.72 (m, 2H, H-7, H-4’), 7.62 - 7.59 (m, 2H, H-5’ and H-6’); MS: (m/z) 286 (M+).
Anal. Calcd for C13H7ClN4S: C, 54.45; H, 2.46, N, 19.54. Found: C, 54.63; H, 2.30; N, 19.30.
3-m-Tolylthieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10g):
72% Yield, mp 274 – 276 °C; 1H NMR (CDCl3): δ 9.06 (s, 1H, H-5), 7.79 (d, J = 6.0 Hz, 1H, H-8), 7.72
(s, 1H, H-2’), 7.67 (d, 1H, H-6’), 7.62 (d, J = 6.0 Hz, 1H, H-7), 7.55 (t, 1H, H-5’), 7.44 (d, 1H, H-4’);
MS: (m/z) 266 (M+), 149, 132. Anal. Calcd for C14H10N4S: C, 63.14; H, 3.78, N, 21.04. Found: C, 63.43;
H, 3.60; N, 21.33.
3-(3-Bromophenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10h):
77% Yield, mp 186 – 187 °C; 1H NMR (CDCl3): δ 8.98 (s, 1H, H-5), 8.05 (s, 1H, H-2’) 7.95 (d, J = 6.0
Hz, 1H, H-8), 7.86 - 7.79 (m, 3H, H-9, H-4’ and H-6’), 7.59 (t, 1H, H-5’); MS: (m/z) 331 (M+). Anal.
Calcd for C13H7BrN4S: C, 47.15; H, 2.13, N, 16.92. Found: C, 46.94; H, 1.91; N, 17.10.
3-(2-Methoxyphenyl)thieno[2,3-e][1,2,4]triazolo[4,3-c]pyrimidine (10i):
70% Yield, mp 191 – 192 °C; 1H NMR (CDCl3): δ 9.00 (s, 1H, H-5), 7.94 (d, J = 6.0 Hz, 1H, H-8), 7.75
(d, J = 5.9 Hz, 1H, H-9), 7.68 - 7.57 (m, 2H, H-4’and H-6’), 7.52 (t, 1H, H-4’) 7.46 (d, 1H, H-3’), 2.52 (s,

HETEROCYCLES, Vol. 75, No. 12, 2008
3097
3H, methyl); MS: (m/z) 282 (M+). Anal. Calcd for C14H10N4OS: C, 59.56; H, 3.57, N, 19.85. Found: C,
59.48; H, 3.78; N, 19.66.
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