Efficient one-pot synthesis of alkyl 3-(alkyl)-4-methyl-2-thioxo-2,3- dihydrothiazole-5-carboxylates in a multi component reaction

Article abstract of DOI:10.1002/jccs.201200109

A simple and efficient one-pot synthesis of alkyl 2-(alkyl)-4-methyl-2- thioxo-2,3-dihydrothiazole-5-carboxylates from the reaction of primary alkylamines and carbon disulfide in the presence of 2-chloro-1,3-dicarbonyl compounds is described. This new pro

Full text of DOI:10.1002/jccs.201200109

JOURNAL OF THE CHINESE
CHEMICAL SOCIETY
Article
Efficient One-pot Synthesis of Alkyl 3-(alkyl)-4-methyl-2-thioxo-2,3-dihydrothiazole-5-
carboxylates in a Multi Component Reaction
Nasir Iravani,a* Jalal Albadi,a Somaieh Varnaseri,b Zahra Jaberi,b Nahid Karamib and
Marzieh Khadamatib
aYoung Researchers Club, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran
bDepartment of Chemistry, Gachsaran Branch, Islamic Azad University, Gachsaran, Iran
(Received: Feb. 29, 2012; Accepted: Jun. 4, 2012; Published Online: ??; DOI: 10.1002/jccs.201200109)
A simple and efficient one-pot synthesis of alkyl 2-(alkyl)-4-methyl-2-thioxo-2,3-dihydrothiazole-5-
carboxylates from the reaction of primary alkylamines and carbon disulfide in the presence of 2-
chloro-1,3-dicarbonyl compounds is described. This new protocol has several advantages such as lack of
necessity of the catalyst, good yields, mild conditions and short times for reaction.
Keywords: 2-Chloro-1,3-dicarbonyl compounds; 2-Thioxo-2,3-dihydrothiazole; Carbon disulfide;
Primary alkylamines.
The three-component one-pot synthesis of
Scheme I
INTRODUCTION
Thiazoles and their derivatives exhibit various bio-
2-thioxo-2,3- dihydrothiazoles 4
logical activities such as antimicrobial, anti-inflammatory,
antiviral, antituberculosis and cytotoxic activities.1-6 For
example, the thiazolium ring present in vitamine B1 serves
as an electron sink, and its coenzyme form is important for
the decarboxylation of a-keto-acids.7 Specially some thi-
azolines show interesting anti-HIV or anticancer activities
and can inhibit cell division.8-10 In view of the importance
of thiazoles and their derivatives, several methods for their
synthesis have been developed. The most widely used
method is Hantzsch synthesis involving the reaction of a-
halocarbonyl compounds with thioureas or thioamides.11-13
Recently, a synthesis of thiazol-2-imine derivative from
benzoyl phenylthioureas and the in situ generated a-bro-
moketones obtained by the reaction of enolizable ketones
with 1,10-(ethane-1,2-diyl)dipyridinium bistribromide has
been reported.14,15 Also thiazole derivatives were synthe-
sized by using catalysts such as ammonium 12-molybdo-
phosphate,16 cyclodextrin,17 iodine,18a and silica chlo-
ride18b in organic solvents such as 1-methyl-2-pyrrolidi-
none,19 and with the use of microwave irradiation.20
EXPERIMENTAL SECTION
Amines, carbon disulfide, and 2-chloro-1,3-dicar-
bonyl compounds were obtained from Fluka and were used
without further purification; IR spectra: Shimadzu IR-460
spectrometer; 1H and 13C NMR spectra: Bruker DRX-400
AVANC instrument; in CDCl3 at 400 MHz and 100 MHz,
respectively, d in ppm J in Hz; Elemental analyses (C, H,
and N) were performed with a Heraeus CHN-O-Rapid ana-
lyzer. The analyses data were in agreement with the pro-
posed structures.
However, in spite of their potential utility, many of
these method suffer from drawbacks, such as harsh reac-
tion conditions, cumbersome product isolation procedures,
and often expensive catalysts. As a part of our current stud-
ies, on the development of new routes in heterocyclic syn-
thesis, 21,22 in this article, we wish to report a convenient
and facile synthesis of new functionalized 2,3-dihydrothi-
azole 4 derivatives in good yields (See Scheme I).
General procedure for the preparation of compounds
4a-l
A mixture of 0.175 g of carbon disulfide (2.3 mmol)
and the primary alkylamine 1 (2 mmol) was stirred at room
* Corresponding author. Tel.: +98 742 333923; Fax: +98 742 3332003; E-mail: iravaninasir56@gmail.com, iravani.nasir@yahoo.com
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1

Article
Iravani et al.
n
Ethyl 3-( propyl)-4-methyl-2-thioxo-2,3-dihydrothi-
temperature for 30 min. Then, 2-chloro-1,3-dicarbonyl
compound 3 (2 mmol) was added to the reaction mixture
and stirred at room temperature. After completion of the re-
action [3–6 h; TLC (n-hexane/AcOEt 3:1)], the reaction
mixture was purified by column chromatography [silica gel
(230–240 mesh; Merck), n-hexane/AcOEt 4:1)] to afford
the pure title compounds.
azole-5-carboxylate (4d)
Colorless oil, Yield: 0.42 g (85%). IR (KBr): n =
2850-2900 (CH aliph), 1700 (C=O), 1585 (C=C), 1170
(C=S) cm-1. 1H NMR: d = 0.98 (3H, t, 3JHH = 7.3 Hz, CH3),
1.31 (3H, t, 3JHH = 7.1 Hz, CH3), 1.75 (2H, six, 3JHH = 7.5
3
Hz, CH2), 2.66 (3H, s, CH3), 4.15 (2H, t, JHH = 7.4 Hz,
CH2), 4.27 (2H, q, 3JHH = 7.2 Hz, OCH2) ppm. 13C NMR: d
= 11.1 (CH3), 14.1 (CH3), 14.2 (CH2), 20.8 (CH3), 48.9
(CH2), 61.5 (OCH2), 111.8 (C), 147.8 (C), 160.1 (C=O),
188.6 (C=S) ppm. Anal. Calcd for C10H15NO2S2 (245.36):
C, 48.95; H, 6.16; N, 5.71. Found: C, 48.98; H, 6.21; N,
5.62%.
Ethyl 3-(4-methoxybenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4a)
Yellow oil, Yield: 0.52 g (81%). IR (KBr): n = 3020
(CH arom), 2850 (CH aliph), 1710 (C=O), 1580 (C=C),
1170 (C=S) cm-1. 1H NMR: d = 1.34 (3H, t, 3JHH = 7.2 Hz,
CH3), 2.56 (3H, s, CH3), 3.79 (3H, s, CH3), 4.29 (2H, q,
3JHH = 7.2 Hz, OCH2), 5.51 (2H, s, CH2), 6.87 (2H, d, 3JHH
= 8.4 Hz, 2 CH), 7.18 (2H, d, 3JHH = 8.4 Hz, 2 CH) ppm. 13C
NMR: d = 14.2 (CH3), 14.4 (CH3), 49.9 (CH2), 55.3
(OCH3), 61.5 (OCH2), 111.8 (C), 114.3 (2 CH), 126.3 (C),
128.1 (2 CH), 140.4 (C), 159.3 (C), 160 (C=O), 189.7
(C=S) ppm. Anal. Calcd for C15H17NO3S2 (323.43): C,
55.7; H, 5.3; N, 4.33. Found: C, 55.11; H 5.51; N, 4.28%.
Ethyl 3-(4-methylbenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4b)
Ethyl 3-(4-fluorobenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4e)
Yellow oil, Yield: 0.56 g (89%). IR (KBr): n = 2850-
2900 (CH aliph), 1715 (C=O), 1588 (C=C), 1165 (C=S)
cm-1. 1H NMR: d = 1.33 (3H, t, 3JHH = 7.2 Hz, CH3), 2.55
(3H, s, CH3), 4.28 (2H, q, 3JHH = 7.2 Hz, OCH2), 5.52 (2H,
s, CH2), 7.03 (2H, t,3JHH = 8.4 Hz, 2CH), 7.21 (2H, t, 3JHH
=
5.2 Hz, 2 CH), 13C NMR: d = 14.2 (CH3), 14.4 (CH3), 49.7
(CH2), 61.7 (CH2O), 112.1 (C), 115.9 (2 CH, 2JCF= 22 Hz),
128.5 (2 CH, 3JCF = 8 Hz), 130.05 (C, 4JCF = 2 Hz), 148.1
(C), 160 (C-F, 1JCF = 121 Hz), 163.6 (C=O), 189.7 (C=S)
ppm. Anal. Calcd for C14H14FNO2S2 (311.39): C, 53.99; H,
4.53; N, 4.5. Found: C, 54; H, 4.38; N, 4.46%.
Yellow oil, Yield: 0.54 g (88%). IR (KBr): n = 3000
(CH arom), 2910 (CH aliph), 1710 (C=O), 1586 (C=C),
1168 (C=S) cm-1. 1H NMR: d = 1.33 (3H, t, 3JHH = 6.8 Hz,
CH3), 2.33 (3H, s, CH3), 2.54 (3H, s, CH3), 4.28 (2H, q,
3JHH = 6.4 Hz, OCH2), 5.52 (2H, s, CH2), 7.09 (2H, d, 3JHH
= 6.8 Hz, 2 CH), 7.14 (2H, d, 3JHH = 7.6 Hz, 2 CH) ppm. 13C
NMR: d = 14.25 (CH3), 14.44 (CH3), 21.1 (CH3), 50.2
(CH2), 61.59 (OCH2), 111.8 (C), 126.57 (2 CH), 129.67 (2
CH), 131.2 (C), 137.8 (C), 148.48 (C), 160 (C=O), 189.7
(C=S) ppm. Anal. Calcd for C15H17NO2S2 (307.43): C,
58.6; H, 5.58; N, 4.56. Found: C, 58.53; H 5.49; N, 4.51%.
Ethyl 3-(2-chlorobenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4f)
Yellow oil, Yield: 0.5 g (83%). IR (KBr): n = 3050
(CH arom), 2800 (CH aliph), 1700 (C=O), 1582 (C=C),
1175 (C=S) cm-1. 1H NMR: d = 1.35 (3H, t, 3JHH = 7.2 Hz,
CH3), 2.50 (3H, s, CH3), 4.32 (2H, q, 3JHH = 7.2 Hz, OCH2),
5.64 (2H, s, CH2), 6.79-6.81 (1H, m, CH), 7.21-7.26 (2H,
m, 2 CH), 7.41-7.43 (1H, m, CH) ppm. 13C NMR: d = 14.1
(CH3), 14.2 (CH3), 47.7 (CH2), 61.7 (OCH2), 112.1 (C),
126.5 (CH), 127.5 (CH), 129.2 (CH), 129.8 (CH), 131.4
(C), 132.3 (C), 148 (C), 160 (C=O), 189.8 (C=S) ppm.
Anal. Calcd for C14H14ClNO2S2 (317.85): C, 52.9; H, 4.36;
N, 4.4. Found: C, 53; H 4.5; N, 4.33%.
n
Ethyl 3-( butyl)-4-methyl-2-thioxo-2,3-dihydrothiazole-
5-carboxylate (4c)
Colorless oil, Yield: 0.42 g (80%). IR (KBr): n =
2850-2900 (CH aliph), 1720 (C=O), 1580 (C=C), 1175
(C=S) cm-1. 1H NMR: d = 0.97 (3H, t, 3JHH = 6.8 Hz, CH3),
1.32 (3H, t, 3JHH = 6.4 Hz, CH3), 1.42 (2H, six, 3JHH = 7.2
Hz, CH2), 1.69 (2H, qui, 3JHH = 6.8 Hz, CH2), 2.67 (3H, s,
Methyl 3-(4-methylbenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4g)
CH3), 4.19 (2H, t, 3JHH = 7.6 Hz, CH2), 4.27 (2H, q, 3JHH
=
Yellow oil, Yield: 0.53 g (90%). IR (KBr): n = 3100
(CH arom), 2800 (CH aliph), 1690 (C=O), 1580 (C=C),
1160 (C=S) cm-1. 1H NMR: d = 2.36 (3H, s, CH3), 2.58 (3H,
s, CH3), 3.86 (3H, s, OCH3), 5.55 (2H, s, CH2), 7.11 (2H, d,
3JHH = 8 Hz, 2 CH), 7.17 (2H, d, 3JHH = 8 Hz, 2 CH) ppm.
13C NMR: d = 14.4 (CH3), 21.1 (CH3), 50.3 (CH2), 52.4
7.2 Hz, OCH2) ppm. 13C NMR: d = 13.6 (CH3), 14.1 (CH3),
14.2 (CH2), 20.1 (CH3), 29.4 (CH2), 47.4 (CH2), 61.5
(OCH2), 111.8 (C), 147.8 (C), 160.1 (C=O), 188.5 (C=S)
ppm. Anal. Calcd for C11H17NO2S2 (259.39): C, 50.93; H,
6.61; N, 5.4. Found: C, 50.86; H 6.42; N, 5.12%.
2
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2-Chloro-1,3-dicarbonyl Compounds
(OCH3), 125.04 (C), 126.56 (2 CH), 129.7 (2 CH), 131.1
(C), 137.9 (C), 148.7 (C), 160.5 (C=O), 189.8 (C=S) ppm.
Anal. Calcd for C14H15NO2S2 (293.4): C, 57.3; H, 5.15; N,
4.77. Found: C, 57.85; H 5.2; N, 4.81%.
6.5 Hz, 2CH), 7.34 (1H, d, 3JHH = 7.6 Hz, CH), 7.39 (1H, d,
3JHH = 7.6 Hz, CH) ppm. 13C NMR: d = 14.01 (CH3), 44.01
(CH2), 55.27 (OCH3), 110.2 (C), 113.2 (CH), 120.4 (CH),
124.7 (2CH), 127.4 (C), 128.5 (C), 156.9 (C=O), 189.9
(C=S) ppm. Anal. Calcd for C13H12NO2S2 (313.83): C,
49.75; H, 3.86; N, 4.46. Found: C, 49.8; H, 3.73; N, 4.36%.
Methyl 3-(4-methoxybenzyl)-4-methyl-2-thioxo-2,3-di-
hydrothiazole-5-carboxylate (4l)
Methyl 3-(benzyl)-4-methyl-2-thioxo-2,3-dihydrothi-
azole-5-carboxylate (4h)
Yellow oil, Yield: 0.49 g (89%). IR (KBr): n = 3020
(CH arom), 2950 (CH aliph), 1715 (C=O), 1583 (C=C),
1180 (C=S) cm-1. 1H NMR: d = 2.57 (3H, s, CH3), 3.86 (3H,
s, OCH3), 5.59 (2H, s, CH2), 7.22 (2H, d, 3JHH = 6.8 Hz, 2
CH), 7.34-7.37 (3H, m, 3 CH) ppm. 13C NMR: d = 14.2
(CH3), 50.42 (CH2), 53.5 (OCH3), 112.8 (C), 126.7 (CH),
127.5 (2CH), 128.4 (2CH), 136.5 (C), 149.3 (C), 167.6
(C=O), 187.8 (C=S) ppm. Anal. Calcd for C13H13NO2S2
(279.37): C, 55.89; H, 4.69; N, 5.01. Found: C, 55.3; H 4.5;
N, 4.95%.
Dark yellow oil, Yield: 0.51 g (82%). IR (KBr): n =
3050 (CH arom), 2950 (CH aliph), 1715 (C=O), 1580
(C=C), 1168 (C=S) cm-1. 1H NMR: d = 2.41 (3H, s, CH3),
3.31 (3H, s, OCH3), 3.85 (3H, s, OCH3), 5.6 (2H, s, CH2),
6.93 (2H, d, 3JHH = 8.4 Hz, 2CH), 7.34 (2H, d, 3JHH = 8.4
Hz, CH) ppm. 13C NMR: d = 14.4 (CH3), 50.1 (CH2), 52.5
(OCH3), 55.4 (OCH3), 114.1 (C), 114.49 (2CH), 127.67
(C), 129.5 (2 CH), 159.7 (C), 171.6 (C), 186.8 (C=O),
191.5 (C=S) ppm. Anal. Calcd for C14H15NO3S2 (309.4): C,
54.34; H, 4.89; N, 4.53. Found: C, 54.31; H, 4.5; N, 4.55%.
n
Methyl 3-( butyl)-4-methyl-2-thioxo-2,3-dihydrothi-
azole-5-carboxylate (4i)
Colorless oil, Yield: 0.36 g (75%). IR (KBr): n = 3050
(CH arom), 2950 (CH aliph), 1710 (C=O), 1580 (C=C),
1185 (C=S) cm-1. 1H NMR: d = 0.99 (3H, t, 3JHH = 7.2 Hz,
CH3), 1.4 (2H, six, 3JHH = 7.2 Hz, CH2), 1.75 (2H, qui, 3JHH
= 7.2 Hz, CH3), 2.44 (3H, s, CH3), 3.84 (3H, s, OCH3), 4.21
(2H, t, 3JHH = 7.2 Hz, CH2) ppm. 13C NMR: d = 13.7 (CH3),
14.1 (CH3), 20.3 (CH2), 29.7 (CH2) 45.3 (CH2), 57.38
(OCH3), 111.38 (C), 148.02 (C), 160.5 (C=O), 188.69
(C=S) ppm. Anal. Calcd for C10H15NO2S2 (245.36): C,
48.95; H, 6.16; N, 5.71. Found: C, 48.5; H, 6.5; N, 5.68%.
Methyl 3-(2-methoxybenzyl)-4-methyl-2-thioxo-2,3-
dihydrothiazole-5-carboxylate (4j)
RESULTS AND DISCUSSION
The reaction of alkyl amines 1 and carbon disulfide 2
in the presence of 2-chloro-1,3-dicarbonyl compounds 3
proceeds smoothly at room temperature to produce alkyl
2-(alkyl)-4-methyl-2-thioxo-2,3-dihydrothiazole-5-carbo
xylates 4a-4l in good yields (Scheme I).
In this procedure, we have reported a simple method
for thiazole synthesis via the reaction of Alkyl-dithiocar-
bamic acids (5, see Scheme II) with 2-chloro-1,3-dicar-
bonyl compounds 3. Thus, various Alkyl-dithiocarbamic
acid derivatives were prepared from 1 and 2. Function-
alized 2,3-dihydrothiazoles 4 were obtained from the reac-
tion of these dithiocarbamic acids with 3.
Dark yellow oil, Yield: 0.48 g (77%). IR (KBr): n =
3050 (CH arom), 2980 (CH aliph), 1720 (C=O), 1550
(C=C), 1170 (C=S) cm-1. 1H NMR: d = 2.41 (3H, s, CH3),
3.49 (3H, s, OCH3), 3.89 (3H, s, OCH3), 4.73 (2H, s, CH2),
6.93 (1H, d, 3JHH = 8 Hz, CH), 7.01 (1H, t, 3JHH = 7.6 Hz,
CH), 7.35 (2H, d, 3JHH = 7.6 Hz, 2 CH) ppm. 13C NMR: d =
14.2 (CH3), 47.8 (CH2), 52.48 (OCH3), 54.4 (OCH3), 126.5
(C), 126.9 (CH), 127.5 (CH), 128.3 (CH), 129.1 (CH),
129.9 (C), 142.2 (C), 148.03 (C), 169.01 (C=O), 182.5
(C=S) ppm. Anal. Calcd for C14H15NO3S2 (309.4): C,
54.34; H, 4.89; N, 4.53. Found: C, 54.31; H, 4.5; N, 4.55%.
Methyl 3-(2-chlorobenzyl)-4-methyl-2-thioxo-2,3-dihy-
drothiazole-5-carboxylate (4k)
Plausible mechanism for the formation of
Scheme II
2-thioxo-2,3- dihydrothiazoles 4
Dark yellow oil, Yield: 0.5 g (80%). IR (KBr): n =
3020 (CH arom), 2900 (CH aliph), 1750 (C=O), 1520
(C=C), 1176 (C=S) cm-1. 1H NMR: d = 1.71 (3H, s, CH3),
The structures of compounds 4a-4l were deduced
from their elemental analyses and their IR, 1H NMR, and
13C NMR spectral data.
3.87 (3H, s, OCH3), 5.33 (2H, s, CH2), 7.25 (2H, t, 3JHH
=
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Article
Iravani et al.
The 1H NMR spectrum of 4a in CDCl3 showed seven
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CONCLUSIONS
In conclusion, we report a novel transformation in-
volving carbon disulfide and primary alkyl amines in the
presence of 2-chloro-1,3-dicarbonyl compounds, which af-
fords alkyl 2-(alkyl)-4-methyl-2-thioxo-2,3-dihydrothi-
azole-5-carboxylates. This new protocol has several ad-
vantages such as lack of necessity of the catalyst, good
yields, short times for reaction, simple experimental and
work-up procedure, and reaction is performed at room tem-
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starting materials. The procedure described here provides
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ACKNOWLEDGEMENTS
We are thankful to the Gachsaran branch, Islamic
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J. Chin. Chem. Soc. 2012, 59, 000-000