Synthesis and biological activity of a series of new thieno[2,3-d] pyrimidines

Article abstract of DOI:10.1080/10426500903127565

Ethyl 2-amino-5-ethylthiophene-3- carboxylate 1, obtained from the reaction of butyraldehyde, ethyl cyanoacetate, sulfur, and triethylamine, reacted with benzoylisothiocyanate to give the corresponding ureido derivatives 2 in a high yield. Further reactions of the compound 2 with an aqueous-alcohol solution of potassium hydroxide and then with hydrochloric acid gave the 2-thio-thieno[2,3-d]pyrimidine-4-ones 3, which were reacted with RX to give novel compounds 4a-4i. Treating the compound 3 with dibromoalkane led to the formation of triacylic compounds 5j-5m. Their structures were clearly verified by IR, 1H NMR, EI-MS spectroscopy, and elemental analysis. The results of a preliminary bioassay indicated that some compounds possess excellent inhibitory activities against the root and the stalk of Brassica napus (rape) and Echinochloa crusgalli (barnyard grass) at a dosage of 100 mg/L. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. Copyright Taylor & Francis Group, LLC.

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Synthesis and Biological Activity of a
Series of New Thieno[2,3-d]Pyrimidines
Tao Wang a , Cai Hua Zheng a , Sue Liu a & Hui Zong Chen a
a College of Chemistry and Chemical Engineering , Jiangxi Normal
University , Nanchang, P. R. China
Published online: 02 Jul 2010.
To cite this article: Tao Wang , Cai Hua Zheng , Sue Liu & Hui Zong Chen (2010) Synthesis and
Biological Activity of a Series of New Thieno[2,3-d]Pyrimidines, Phosphorus, Sulfur, and Silicon and the
Related Elements, 185:7, 1543-1549, DOI: 10.1080/10426500903127565
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Phosphorus, Sulfur, and Silicon, 185:1543–1549, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500903127565
SYNTHESIS AND BIOLOGICAL ACTIVITY OF A SERIES
OF NEW THIENO[2,3-d]PYRIMIDINES
Tao Wang, Cai Hua Zheng, Sue Liu, and Hui Zong Chen
College of Chemistry and Chemical Engineering, Jiangxi Normal University,
Nanchang, P. R. China
Ethyl 2-amino-5-ethylthiophene-3- carboxylate 1, obtained from the reaction of butyralde-
hyde, ethyl cyanoacetate, sulfur, and triethylamine, reacted with benzoylisothiocyanate to
give the corresponding ureido derivatives 2 in a high yield. Further reactions of the compound
2 with an aqueous-alcohol solution of potassium hydroxide and then with hydrochloric acid
gave the 2-thio-thieno[2,3-d]pyrimidine-4-ones 3, which were reacted with RX to give novel
compounds 4a–4i. Treating the compound 3 with dibromoalkane led to the formation of
1
triacylic compounds 5j–5m. Their structures were clearly verified by IR, H NMR, EI-MS
spectroscopy, and elemental analysis. The results of a preliminary bioassay indicated that
some compounds possess excellent inhibitory activities against the root and the stalk of
Brassica napus (rape) and Echinochloa crusgalli (barnyard grass) at a dosage of 100 mg/L.
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental
file.
Keywords Biological activities; synthesis; thieno[2,3-d]pyrimidines
INTRODUCTION
The thieno[2,3-d]pyrimidines have been the focus of great interest over many years.
This is due to the wide range of biological activities associated with this heterocyclic
scaffold. Some of their derivatives have shown remarkable biological properties such as
anticonvulsant, anxiolytic, antihypertensive, anti-arthritic, antimicrobial, antiviral, and an-
tibronchitis, and and have also shown tranquilizer activity.1–18 Although many methodolo-
gies have been developed for the synthesis of various substituted thienopyrimidines,19–21
the synthesis and herbicidal activities of 2-substituted thio-6-ethylthieno[2,3-d]pyrimidine-
4-ones have not been reported. Recently, we have become interested in the synthesis of
new bioactive heterocycles such as 2-substituted thio-6-ethylthieno[2,3-d] pyrimidine-4-
ones, with the aim of evaluating their biological activities. In this article, we describe a
facile synthesis of 2-substituted thio-6-ethylthieno[2,3-d]pyrimidine-4-ones via the ureido
Received 29 January 2009; accepted 17 June 2009.
We are grateful to the National Natural Science Foundation of China (No. 20862007) and Natural Science
Foundation of Jiangxi Province (No. 2007GZH1399).
Address correspondence to Tao Wang, College of Chemistry and Chemical Engineering, Jiangxi Normal
University, Nanchang 330022, P. R. China. E-mail: wangtao1962@sohu.com
1543

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T. WANG ET AL.
derivatives and cyclization reaction. The results of the bioassay indicated that these title
compounds possess herbicidal activity against the root and the stalk of Brassica napus
(rape) and Echinochloa crusgalli (barnyard grass).
RESULTS AND DISCUSSION
Synthesis
The starting material, ethyl 2-amino-5-ethylthiophene-3-carboxylate 1, was synthe-
sized according to the procedures in the literature.22 Ethyl 2-amino-5-ethyl-thiophene-3-
carboxylate 1, obtained from the reaction of butyraldehyde, ethyl cyanoacetate, sulfur, and
triethylamine in DMF at room temperature, reacted with benzoylisothiocyanate to give the
corresponding ureido derivatives 2 with a high yield. Further reactions of the compound
2 with an aqueous alcohol solution of potassium hydrocide and then with hydrochloric
acid gave the 2-thio-thieno[2,3-d]pyrimidine-4-ones 3, which were reacted with RX to give
novel compounds 4a–4i (Table I). Treating compound 3 with dibromoalkane led to the
formation of triacylic compounds 5j–5m (Scheme 1).
O
NCCH2COOC2H5
PhCONCS
OC2H5
NH2
CH3CH2CH2CHO + S
O
H3CH2C
S
1
O
OC2H5
1. KOH
2. HCl
NH
3
H3CH2C
S
NH C NH C Ph
H3CH2C
S
N
H
S
S
O
2
BrRBr
O
O
N
RX
N
NH
SR
R
S
H3CH2C
S
N
H3CH2C
S
5
4
Scheme 1 Synthesis of the title compounds 4a–i and 5j-m. R: 4a, CH3; 4b, CH2CH3; 4c, CH2CH2CH3; 4d,
CH2CH2CH2CH3; 4e, CH(CH3)CH2CH3; 4f, CH2(CH2)3CH3; 4g, CH2Ph; 4h, CH2COOH; 4i, CH2COOEt; 5j,
CH2CH2; 5k, CH2CH2CH2; 5l, CH2(CH2)2CH2; 5m, CH2(CH2)3CH2.
The molecular structures of all new compounds obtained were confirmed by 1H NMR, IR
spectra, MS, and elemental analyses.
1
In the H NMR spectra of 4a–4i and 5j–5m, the proton in the thiophene moiety
exhibits a singlet. The IR spectra of all compounds showed normal stretching absorption
bands indicating the existence of the N–H (∼3400 cm−1), C O (∼1660 cm−1). The EI
mass spectra of compounds 4a–4i and 5j–5m gave the anticipated molecular ion peaks. All
the fragmentation ions of 4a–4i and 5j–5m were consistent with their structures and can
be clearly assigned.

NEW THIENO[2,3-d]PYRIMIDINES
1545
Table I The physical data of compounds 4a–4i and 5j–5m
Compound
R
Formula
Color
mp (◦C)
Rt (h)
Yield (%)a
4a
4b
4c
4d
4e
4f
4g
4h
4i
CH3
CH2CH3
C9H10N2OS2
C10H12N2OS2
C11H14N2OS2
C12H16N2OS2
C12H16N2OS2
C13H18N2OS2
C15H14N2OS2
C10H10N2O3S2
C12H14N2O3S2
C10H10N2OS2
C11H12N2OS2
C12H14N2OS2
C13H16N2OS2
Yellow
Yellow
Yellow
Yellow
Yellow
White
White
White
White
Yellow
Yellow
Yellow
Yellow
225–227
>280
>280
150–153
156–158
143–145
226–228
>300
>280
81–83
90–92
103–105
121–123
12
13
12
11
12
13
12
12
12
13
13
13
13
94
87
91
78
89
80
82
87
70
77
72
68
67
CH2CH2CH3
CH2CH2CH2CH3
CH(CH3)CH2CH3
CH2(CH2)3CH3
CH2Ph
CH2COOH
CH2COOEt
CH2CH2
5j
5k
5l
CH2CH2CH2
CH2(CH2)2CH2
CH2(CH2)3CH2
5m
aYields of isolated products based on iminophosphorane 3.
Herbicidal Activity
The herbicidal activity of all compounds 4a–4i and 5j–5m against Brassica napus
(rape) and Echinochloa crusgalli (barnyard grass) has been investigated at the dosage of
100 mg/L and 10 mg/L using a known procedure23 compared with distilled water. (See the
Supplemental Materials, Table S1, available online.)
EXPERIMENTAL
Melting points were measured on an electrothermal melting point apparatus and are
uncorrected. Mass spectra were measured on a Finnigan Trace MS 2000 spectrometer. IR
spectra were recorded on a PE-983 infrared spectrometer as KBr pellets with absorption
1
in cm−1. H NMR spectra were recorded in DMSO-d6 or CDCl3 as solvent on a Varian
Mercury 400 spectrometer, and resonances are given in ppm (δ) relative to TMS. Elementary
analyses were taken on a Vario EL III elementary analysis instrument. All of the solvents
and materials were reagent grade and purified as required.
Synthesis of 2-(N-Benzoylthioureido)-3-ethoxycarbonyl-5-
ethylthiophene 2
To a solution of 1.99 g (0.01 mol) of ethyl 2-amino-5-ethylthiophene-3-carboxylate
1 in CH3CN (20 mL) at 35◦C, benzoylisothiocyanate 1.63 g (0.01 mol) was added with
stirring. The mixture was stirred for 3 h. The precipitate was separated by filtration and
washed with diethyl ether (10 mL) to obtain 3.22 g (88.9%) of compound 2. Colorless
crystals, mp 136–138◦C; 1H NMR (400 MHz, CDCl3) δ: 14.74 (s, 1H, NH CS ), 9.14 (s,
1H, NH CO ), 7.53–7.99 (m, 5H, Ph), 7.07 (s, 1H, C4HS-4H), 4.47 (q, J = 5.6 Hz, 2H,
COOCH2CH3), 2.79 (q, J = 5.6 Hz, 2H, CH2CH3), 1.42 (t, J = 5.6 Hz, 3H, COOCH2CH3),
1.35 (t, J = 5.6 Hz, 3H, CH2CH3).

1546
T. WANG ET AL.
Synthesis of 2-Thio-thieno[2,3-d]pyrimidine-4-ones 3
A mixture of 3.62 g (0.01 mol) of compound 2 and potassium hydroxide 1.12 g
(0.02 mol) in 50% aqueous ethanol (20 mL) was boiled for 2 h. Upon cooling, the reaction
mixture was acidified with a 10% aqueous hydrochloric acid solution (6 mL) to obtain a
weakly acidic solution. The precipitated crystals were separated by filtration, washed with
water, and dried to obtain 1.23 g (58%) of compound 3; Colorless crystals, mp 261–263◦C;
1H NMR (400 MHz, DMSO-d6) δ: 6.16 (s, 1H, C4HS-4H), 2.04 (q, J = 5.6 Hz, 2H,
CH2CH3), 0.52 (t, J = 5.6 Hz, 3H, CH2CH3). MS (EI, m/z,%): 212 (M+ 56.2); Anal.
Calcd. (%) for C8H8N2OS2: C 45.26, H 3.80, N 13.20; Found C 45.33, H 4.01, N 13.41.
General Procedure for the Preparation of 2-Substituted Thio-6-
ethylthieno[2,3-d]pyrimidine-4-ones 4a–4i and 5j–5m
To a solution of compound 3 (2.12 g, 0.01 mol) and potassium hydroxide (0.56 g,
0.01 mol) in 90% aqueous ethanol (90 mL) was added dropwise to RX (0.01 mol) or
dibromoalkane (0.01 mol), and the mixture was boiled for 12–13 h. Upon cooling, the
reaction mixture was diluted with water (50 mL). The precipitated crystals were separated
by filtration, washed with water, and dried to obtain compounds 4a–4i and 5j–5m.
2-Methylthio-6-ethylthieno[2,3-d]pyrimidine-4-ones
(4a). IR
(KBr,
υ/cm−1): 3410 (NH), 1661 (C O), 1554, 1323, 794; 1H NMR (MeOD, 400 MHz): 7.01 (s,
1H, C4HS-4H), 2.84 (q, J = 5.6 Hz, 2H, CH2CH3), 2.70 (s, 3H, SCH3), 1.34 (t, J = 5.6 Hz,
3H, CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS, 400 MHz): 9.2 (SCH3), 14.6 (CH2CH3),
23.2 (CH2CH3), 116.1 (thienyl-5C), 119.4 (pyrimidine-8C), 140.6 (thienyl-6C), 160.2
(pyrimidine-9C), 163.2 (pyrimidine-2C), 164.8 (pyrimidine-4C); MS (EI, m/z,%): 226
(M+ 12.6); Anal. Calcd. (%) for C9H10N2OS2: C 47.76, H 4.45, N 12.38; Found C 47.52,
H 4.64, N 12.47.
2-Ethylthio-6-ethylthieno[2,3-d] pyrimidine-4-ones (4b). IR (KBr, υ/cm−1):
3401 (NH), 1660 (C O), 1559, 1333, 795; 1H NMR (MeOD, 400 MHz): 6.97 (s, 1H, C4HS-
4H), 3.14 (q, J = 5.6 Hz, 2H, SCH2CH3), 2.84 (q, J = 5.6 Hz, 2H, CH2CH3), 1.37 (t, J = 5.6
Hz, 3H, SCH2CH3), 1.34 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS,
400 MHz): 14.9(SCH2CH3), 15.2 (CH2CH3), 21.3 (SCH2CH3), 23.4 (CH2CH3), 116.1
(thienyl-5C), 120.3 (pyrimidine-8C), 140.5 (thienyl-6C), 160.2 (pyrimidine-9C), 163.6
(pyrimidine-2C), 165.2 (pyrimidine-4C); MS (EI, m/z,%): 240 (M+ 21.9); Anal. Calcd.
(%) for C10H12N2OS2: C 49.97, H 5.03, N 11.66; Found C 49.71, H 5.24, N 11.58.
2-n-Propylthio-6-ethylthieno[2,3-d]pyrimidine-4-ones (4c). IR (KBr,
1
υ/cm−1): 3414 (NH), 1665 (C O), 1536, 1331, 796; H NMR (MeOD, 400 MHz): 6.98
(s, 1H, C4HS-4H), 3.17 (t, J = 5.6 Hz, 2H, SCH2CH2CH3), 2.85 (q, J = 5.6 Hz, 2H,
CH2CH3), 1.70 (t, J = 5.6 Hz, 2H, SCH2CH2CH3), 1.34 (t, J = 5.6 Hz, 3H, CH2CH3),
0.97 (t, J = 5.6 Hz, 3H, SCH2CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS, 400 MHz):
13.9 (SCH2CH2CH3), 15.3 (CH2CH3), 21.4 (SCH2CH2CH3), 23.8 (CH2CH3), 27.8
(SCH2CH2CH3), 115.6 (thienyl-5C), 120.0 (pyrimidine-8C), 141.0 (thienyl-6C), 160.2
(pyrimidine-9C), 164.3 (pyrimidine-2C), 165.5 (pyrimidine-4C); MS (EI, m/z,%): 254
(M+ 19.2); Anal. Calcd. (%) for C11H14N2OS2: C 51.94, H 5.55, N 11.01; Found C 51.73,
H 5.62, N 11.26.
2-n-Butylthio-6-ethylthieno[2,3-d]pyrimidine-4-ones
(4d). IR
(KBr,
1
υ/cm−1): 3415 (NH), 1656 (C O), 1536, 1322, 793; H NMR (MeOD, 400 MHz): 6.99
(s, 1H, C4HS-4H), 3.17 (t, J = 5.6 Hz, 2H, SCH2CH2CH2CH3), 2.86 (q, J = 5.6 Hz,

NEW THIENO[2,3-d]PYRIMIDINES
1547
2H, CH2CH3), 1.70 (m, J = 5.6 Hz, 2H, SCH2CH2CH2CH3), 1.51 (m, J = 5.6
Hz, 2H, SCH2CH2CH2CH3), 1.34 (t, J = 5.6 Hz, 3H, CH2CH3), 0.98 (t, J =
5.6 Hz, 3H, SCH2CH2CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS, 400 MHz):
13.6(SCH2CH2CH2CH3), 15.4 (CH2CH3), 22.1 (SCH2CH2CH2CH3), 23.9 (CH2CH3),
30.4 (SCH2CH2CH2CH3), 31.3 (SCH2CH2CH2CH3), 116.3 (thienyl-5C), 120.5
(pyrimidine-8C), 141.2 (thienyl-6C), 160.1 (pyrimidine-9C), 164.6 (pyrimidine-2C), 165.9
(pyrimidine-4C); MS (EI, m/z,%): 268 (M+ 26.4); Anal. Calcd. (%) for C12H16N2OS2: C
53.70, H 6.01, N 10.44; Found C 53.76, H 6.12, N 10.66.
2-Isobutylthio-6-ethylthieno[2,3-d]pyrimidine-4-ones
(4e). IR (KBr,
υ/cm−1): 3413 (NH), 1641 (C O), 1554, 1322, 795; H NMR (MeOD, 400 MHz):
7.07 (s, 1H, C4HS-4H), 3.96 (m, J = 5.6 Hz, 1H, SCH(CH3)CH2CH3), 2.84 (q, J =
5.6 Hz, 2H, CH2CH3), 1.75 (m, J = 5.6 Hz, 1H, SCH(CH3)CH2CH3), 1.42 (d, J =
5.6 Hz, 3H, SCH(CH3)CH2CH3), 1.34 (t, J = 5.6 Hz, 3H, CH2CH3), 1.03 (t, J =
5.6 Hz, 3H, SCH(CH3)CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS, 400 MHz):
12.2(SCH(CH3)2CH2CH3), 15.2 (CH2CH3), 17.2 (SCH(CH3)2CH2CH3), 23.2 (CH2CH3),
28.6 (SCH(CH3)2CH2CH3), 29.3 (SCH(CH3)2CH2CH3), 115.5 (thienyl-5C), 120.2
(pyrimidine-8C), 141.0 (thienyl-6C), 159.5 (pyrimidine-9C), 164.1 (pyrimidine-2C), 165.2
(pyrimidine-4C); MS (EI, m/z,%): 268 (M+ 20.6); Anal. Calcd. (%) for C12H16N2OS2: C
53.70, H 6.01, N 10.44; Found C 53.83, H 6.26, N 10.58.
1
2-n-Pentylthio-6-ethylthieno[2,3-d]pyrimidine-4-ones
(4f). IR
(KBr,
υ/cm−1): 3415 (NH), 1662 (C O), 1547, 1321, 793; H NMR (MeOD, 400 MHz):
6.97 (s, 1H, C4HS-4H), 3.16 (t, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH3), 2.86 (q, J =
5.6 Hz, 2H, CH2CH3), 1.72 (t, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH3), 1.38∼1.48
(m, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH3), 1.33 (t, J = 5.6 Hz, 3H, CH2CH3), 0.94
(t, J = 5.6 Hz, 3H, SCH2CH2CH2CH2CH3); 13C NMR (δ/ppm, CDCl3, TMS, 400
MHz): 11.8(SCH2CH2CH2CH2CH3), 15.5 (CH2CH3), 22.2 (SCH2CH2CH2 CH2CH3),
23.7 (CH2CH3), 24.7 (SCH2CH2CH2CH2CH3), 28.4 (SCH2CH2CH2CH2CH3), 29.3
(SCH2CH2CH2CH2CH3), 115.4 (thienyl-5C), 119.6 (pyrimidine-8C), 140.6 (thienyl-6C),
159.8 (pyrimidine-9C), 164.2 (pyrimidine-2C), 166.1 (pyrimidine-4C); MS (EI, m/z,%):
282 (M+ 14.2); Anal. Calcd. (%) for C13H18N2OS2: C 55.28, H 6.42, N 9.92; Found C
55.43, H 6.54, N 10.17.
1
2-Benzylthio-6-ethylthieno[2,3-d] pyrimidine-4-ones (4g). IR (KBr,
1
υ/cm−1): 3425 (NH), 1662 (C O), 1526, 1322, 793; H NMR (MeOD, 400 MHz):
7.20–7.44 (m, 5H, Ph-H), 7.00 (s, 1H, C4HS-4H), 4.44 (s, 2H, CH2Ph), 2.84 (q, J =
5.6 Hz, 2H, CH2CH3), 1.35 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, DMSO,
TMS, 400 MHz): 15.4 (CH2CH3), 23.2 (CH2CH3), 33.8 (SCH2C6H5), 117.6 (thienyl-5C),
117.7 (phenyl-2C), 117.9 (phenyl-6C), 120.7 (phenyl-4C), 126.6 (pyrimidine-8C),
128.2 (phenyl-3C), 128.9 (phenyl-5C), 135.8 (phenyl-1C), 139.3 (thienyl-6C), 162.9
(pyrimidine-9C), 164.4 (pyrimidine-2C), 165.8 (pyrimidine-4C); MS (EI, m/z,%): 302
(M+ 17.9); Anal. Calcd. (%) for C15H14N2OS2: C 59.57, H 4.67, N 9.26; Found C 59.78,
H 4.39, N 9.06.
2-Hydroxycarbonylmethylthio-6-ethyl-thieno[2,3-d]pyrimidine-4-ones
1
(4h). IR (KBr, υ/cm−1): 3441 (NH), 1678, 1638 (C O), 1554, 1321, 791; H NMR
(MeOD, 400 MHz): 11.5 (s, 1H, COOH), 7.25 (s, 1H, C4HS-4H), 4.23 (s, 2H, CH2COOH),
2.94 (q, J = 5.6 Hz, 2H, CH2CH3), 1.39 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm,
CDCl3, TMS, 400 MHz): 15.3 (CH2CH3), 23.5 (CH2CH3), 30.2 (SCH2COOH), 116.4
(thienyl-5C), 120.4 (pyrimidine-8C), 141.3 (thienyl-6C), 160.3 (pyrimidine-9C), 164.4
(pyrimidine-2C), 165.8 (pyrimidine-4C), 177.6 (SCH2COOH); MS (EI, m/z,%): 270 (M+

1548
T. WANG ET AL.
25.3); Anal. Calcd. (%) for C10H10N2O3S2: C 44.43, H 3.73, N 10.36; Found C 44.69, H
3.56, N 10.52.
2-Ethoxycarbonylmethylthio-6-ethyl-thieno[2,3-d]pyrimidine-4-ones
1
(4i). IR (KBr, υ/cm−1): 3445 (NH), 1675, 1624 (C O), 1551, 1387, 777; H NMR
(MeOD, 400 MHz): 7.01 (s, 1H, C4HS-4H), 2.84 (q, J = 5.6 Hz, 2H, CH2CH3),
2.70 (s, 3H, SCH3), 1.34 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, CDCl3,
TMS, 400 MHz): 13.7 (SCH2COOCH2CH3), 15.3 (CH2CH3), 23.7 (CH2CH3),
28.4 (SCH2COOCH2CH3), 57.2 (SCH2COOCH2CH3), 116.1 (thienyl-5C), 120.6
(pyrimidine-8C), 141.1 (thienyl-6C), 160.5 (pyrimidine-9C), 164.2 (pyrimidine-2C), 166.3
(pyrimidine-4C), 174.4 (SCH2COOCH2CH3); MS (EI, m/z,%): 298 (M+ 12.4); Anal.
Calcd.(%) for C12H14N2O3S2: C 48.30, H 4.73, N 9.39; Found C 48.46, H 4.81, N 9.53.
6-Ethylthieno[2,3-d]thiazo[3,2-a]pyrimidine-4-ones (5j). IR (KBr, υ/cm−1):
3432 (NH), 1670 (C O), 1526, 1322, 778; 1H NMR (MeOD, 400 MHz): 7.06 (s, 1H, C4HS-
4H), 4.54 (t, J = 5.6 Hz, 2H, SCH2CH2N), 3.62 (t, J = 5.6 Hz, 2H, SCH2CH2N), 2.88 (q, J =
5.6 Hz, 2H, CH2CH3), 1.35 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, DMSO, TMS,
400 MHz): 15.2 (CH2CH3), 23.1 (CH2CH3), 26.8 (SCH2CH2N), 48.3 (SCH2CH2N), 117.0
(thienyl-5C), 120.1 (pyrimidine-8C), 142.8 (thienyl-6C), 155.9 (pyrimidine-9C), 160.4
(pyrimidine-2C), 162.8 (pyrimidine-4C); MS (EI, m/z,%): 238 (M+ 17.8); Anal. Calcd.
(%) for C10H10N2OS2: C 50.39, H 4.23, N 11.75; Found C 50.46, H 4.30, N 11.86.
6-Ethylthieno[2,3-d]thiazino[3,2-a]pyrimidine-4-ones
(5k). IR
(KBr,
υ/cm−1): 3430 (NH), 1668 (C O), 1544, 1320, 774; H NMR (MeOD, 400 MHz): 7.01
(s, 1H, C4HS-4H), 2.84 (q, J = 5.6 Hz, 2H, CH2CH3), 2.70 (s, 3H, SCH3), 1.34 (t, J
= 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, DMSO, TMS, 400 MHz): 15.2 (CH2CH3),
23.3 (CH2CH3), 25.9 (SCH2 CH2CH2N), 37.2 (SCH2CH2CH2N), 46.8 (SCH2CH2CH2N),
117.3 (thienyl-5C), 120.4 (pyrimidine-8C), 142.3 (thienyl-6C), 155.7 (pyrimidine-9C),
160.1 (pyrimidine-2C), 162.9 (pyrimidine-4C); MS (EI, m/z,%): 252(M+ 11.8); Anal.
Calcd. (%) for C11H12N2OS2: C 52.35, H 4.79, N 11.10; Found C 52.43, H 4.54, N 11.19.
6-Ethylthieno[2,3-d]thiazepino[3,2-a]pyrimidine-4-ones (5l). IR (KBr,
1
1
υ/cm−1): 3433 (NH), 1672 (C O), 1548, 1322, 791; H NMR (MeOD, 400 MHz):
7.01 (s, 1H, C4HS-4H), 2.84 (q, J = 5.6 Hz, 2H, CH2CH3), 2.70 (s, 3H, SCH3),
1.34 (t, J = 5.6 Hz, 3H, CH2CH3); 13C NMR (δ/ppm, DMSO, TMS, 400 MHz): 15.1
(CH2CH3), 23.2 (CH2CH3), 24.6 (SCH2 CH2CH2CH2N), 34.4 (SCH2CH2CH2CH2N),
36.2 (SCH2CH2CH2CH2N), 45.3 (SCH2CH2CH2CH2N), 117.7 (thienyl-5C), 121.2
(pyrimidine-8C), 143.1 (thienyl-6C), 156.4 (pyrimidine-9C), 161.2 (pyrimidine-2C), 163.8
(pyrimidine-4C); MS (EI, m/z,%): 266 (M+ 14.6); Anal. Calcd. (%) for C12H14N2OS2: C
54.11, H 5.30, N 10.52; Found C 54.22, H 5.54, N 10.77.
6-Ethylthieno[2,3-d]thiazeoctino[3,2-a]pyrimidine-4-ones (5m). IR (KBr,
1
υ/cm−1): 3432 (NH), 1670 (C O), 1558, 1328, 781; H NMR (MeOD, 400 MHz):
7.09 (s, 1H, C4HS-4H), 3.91 (t, J = 5.6 Hz, 2H, SCH2CH2 CH2CH2CH2N),
3.68 (m, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH2N), 3.60 (t, J = 5.6 Hz, 2H,
SCH2CH2CH2CH2CH2N), 2.05 (m, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH2N),
1.73 (m, J = 5.6 Hz, 2H, SCH2CH2CH2CH2CH2N), 1.34 (t, J = 5.6 Hz, 3H,
CH2CH3); 13C NMR (δ/ppm, DMSO, TMS, 400 MHz): 15.0 (CH2CH3), 23.0
(CH2CH3), 22.3 (SCH2CH2CH2CH2CH2N), 32.4 (SCH2CH2CH2CH2CH2N), 33.2
(SCH2CH2CH2CH2CH2N), 35.7 (SCH2CH2CH2CH2CH2N), 44.2 (SCH2CH2CH2CH2
CH2N), 116.5 (thienyl-5C), 120.2 (pyrimidine-8C), 141.5 (thienyl-6C), 154.1 (pyrimidine-
9C), 160.7 (pyrimidine-2C), 162.4 (pyrimidine-4C); MS (EI, m/z,%): 280 (M+ 18.2);

NEW THIENO[2,3-d]PYRIMIDINES
1549
Anal. Calcd. (%) for C13H16N2OS2: C 55.68, H 5.75, N 9.99; Found C 55.42, H 5.64, N
9.77.
Herbicidal Testing
Herbicidal testing of the newly synthesized compounds 4a–4i and 5j–5m was carried
out in a plant growth room. (See the Supplemental Materials.)
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