Vol. 25, No. 1 (2013)
Synthesis of Alkyl-3-amino-2-arylimino-1,3-thiazolan-4-ones-5-ylidene Acetate 307
Surprisingly di-tert-butyl acetylene dicarboxylate have diffe-
rent treatment and instead of cyclization product, we isolated
condensation product and thiosemicarbazon derivatives are
chief products (Scheme-II).
= 7.1, Me), 4.36 (q, 3JHH = 7.1, CH2O), 4.80 (brs, NH2), 5.21
(s, NH), 6.94 (s, CH) ppm. 13C NMR: δ = 166.2, 163.9 (2C=O),
146.7 (C=N), 142.9 (C), 137.5 (C), 121.0 (CH), 60.5 (CH2O),
16.4 (CH3) ppm. MS: m/z (%) 215 (28, M+), 170 (14), 142
(36), 135 (26), 107 (40), 85 (100), 57 (20), 44 (54). Anal.
calcd. for C7H9N3O3S (215.21): C, 39.01; H, 4.18; N, 19.53
%. Found: C, 38.48; H, 4.13; N, 21.41 %.
CO2CMe3
CO2CCMe3
CO2CMe3
CO2CCMe3
H
N
H
N
H
N
N
N
H2N
The structures of compounds were deduced from their
elemental analyses and their IR, 1H and 13C NMR spectra. The
mass spectra of these compounds displayed molecular ion
peaks at the appropriate m/z- values. The 1H NMR spectrum,
of 3a in CDCl3 showed three singlets for methoxy δ = 3.80,
amino δ = 4.79 and olefinic δ = 7.08 protons δ, along with
multiplets δ = 7.13 - δ = 7.66 for the aromatic protons. The
13C NMR spectra of 3a showed ten signals in agreement whit
the proposed structure. Partial assignments of these resonance
S
S
Scheme-II: Product of 4-Phenylthiosemicarbazide and thiosemicarbazide
with di-tert-butyl acetylene dicarboxylate
RESULTS AND DISCUSSION
In our continuous approach toward developing biologi-
cally active heterocyclic synthesis via acetylenic esters-based
reactions involving CH-, NH- or OH-acid compounds30-34
,
1
13
are given in the experimental section. The H and C NMR
spectra of 3b-3d are similar to those for 3a, except for the
ester and aryl moieties, which exhibit characteristic signals at
appropriate chemical shift. On the basis of well established
chemistry of electrophilic acetylenes it is reasonable to assume
that compounds 3 results from the initial conjugate addition
of the sulfur atom of 1 to the acetylenic ester and the subse-
quent conversion of the 1:1 adduct to 3. Then the ester group
of intermediate 3 is attacked by the amino moiety to yield 3
by elimination of ROH (Scheme-III). When the bulky di-t-
butylacetylenedicarboxylate is used, the steric hindrance
prevent the usual mechanism and the adduct product is not
reasonable. In conclusion, we have prepared novel thiazolidine-
4-one derivatives via one-pot reaction between 4-phenyl-
thiosemicarbazide and thiosemicarbazide with dialkyl acetylene
dicarboxylate. The present method carries the advantage that,
not only is the reaction performed under neutral conditions,
but the substances can be mixed without any activation or
modification.
herein we wish to explain an expedient method for construction
of some novel 2-imino-thiazolidine-4-one-5-ylidene acetate
derivatives (3) from one-pot reaction between 4-phenylthio-
semicarbazide (1a) and thiosemicarbazide (1b) with appro-
priate acetylenic esters (2) in good yields (Scheme-I).
Methyl-3-amino-2-Phenylimino-4-oxo-1,3-thiazolan-
5-ylidene acetate (3a): Pale yellow crystals; yield: 72 %, m.p.
162-163 ºC. IR (KBr, νmax, cm-1): 3316, 3125 (NH2), 1728,
1635 (2C=O), 1684 (C=C), 1610 (C=N). 1H NMR: δ = 3.80
(s, MeO), 4.79 (s, NH2), 7.08 (s, CH), 7.13-7.66 (5H, Ph) ppm.
13C NMR: δ = 168.1, 160.1 (2C=O), 152.6 (C=N), 143.1 (C),
136.2 (C), 128.1 (2CH), 126.8 (CH), 123.7 (2CH), 114.3 (CH),
51.0 (MeO) ppm. MS:m/z (%) = 277 (28, M+), 160 (8), 142
(1), 117 (23), 85 (86), 77 (100), 58 (63), 44 (24). Anal calcd.
for C12H11N3O3S (277.24): C, 51.19; H, 3.96; N, 15.14 %.
Found: C, 51.71; H, 3.77; N, 15.43 %.
Ethyl-3-amino-2-phenylimino-4-oxo-1,3-thiazolan-5-
ylidene acetate (3b): Pale yellow powder; yield: 72 %, m.p.:
162-164 ºC. IR (KBr, νmax, cm-1): 3309, 3146 (NH2), 1719,
1642 (2C=O), 1688 (C=C), 1593 (C=N). 1H NMR: δ = 1.38
(t, 3JHH = 7.3, Me), 4.18 (q, 3JHH = 7.2, CH2O), 4.55 (brs, NH2),
6.78 (s, CH), 7.03-7.49 (5H, Ph) ppm. 13C NMR: δ = 162.2,
160.9 (2C=O), 146.7 (C=N), 146.0 (C), 138.5 (C), 127.9
(2CH), 124.0 (CH), 120.5 (2CH), 115.8 (CH), 62.9 (CH2O),
14.7 (CH3) ppm. MS: m/z (%) 291 (24, M+), 264 (4), 142
(23), 135 (26), 107 (40), 5 (66), 77 (100), 57 (20), 44 (54).
Anal. calcd. for C13H13N3O3S (291.28): C, 53.55; H, 4.46; N,
14.01 %. Found: C, 51.38; H, 4.73; N, 16.01 %.
CO2
R
RHN
RHN
S
CO2R
+
S
H2NHN
H2NHN
CO2
R
RO2
C
RO2
C
Methyl-3-amino-2-imino-4-oxo-1,3-thiazolan-5-
ylidene acetate (3c): Yellow crystals; yield: 89 %, m.p. 180-
181 ºC. IR (KBr, νmax, cm-1): 3300, 3167 (NH2), 1742, 1649
H
RO2
C
RN
S
S
H-Transfer
-ROH
H
1
(2C=O), 1654 (C=C), 1606 (C=N). H NMR: δ = 3.80 (s,
O
H2NHN
RN
MeO), 4.81 (s, NH2), 5.20 (s, NH), 7.11 (s, CH), ppm. 13C
NMR: δ = 164.2, 160.8 (2C=O), 145.6 (C=N), 141.1 (C), 133.8
(C), 122.3 (CH), 51.3 (MeO) ppm. MS: m/z (%) 201 (38, M+),
170 (8), 142 (5), 126 (25), 85 (86), 56 (100), 44 (24). Anal.
calcd. for C6H7N3O3S (201.3): C, 35.82; H, 3.48; N, 20.89 %.
Found: C, 35.74; H, 3.17; N, 21.74 %.
N
NH2
RO
O
Scheme-III: Mechanism of reaction
ACKNOWLEDGEMENTS
Ethyl-3-amino-2-imino-4-oxo-1,3-thiazolan-5-ylidene
acetate (3d): Green yellow powder; yield: 96 %, m.p. 170-
171 ºC. IR (KBr, νmax, cm-1): 3294, 3153 (NH2), 1727, 1648
(2C=O), 1680 (C=C), 1596 (C=N). 1H NMR: δ = 1.33 (t, 3JHH
Financial support for this work by the Research Council
of Islamic Azad University, Tonekabon Branch, is gratefully
acknowledged.