Synthesis of 2,3-Dihydro-1,3,4-thiadiazole, Thiazole, and Triazolo[4,3-a]pyrimidine Derivatives from Ethyl Benzoylacetate

Article abstract of DOI:10.1002/hc.10222

Thiophene and thiazole derivatives can be obtained from potassium salt of ethyl 3-oxo-3-phenyl-2-[(phenylamino)thioxomethyl]propanoate and ethyl chloroacetate in N,N-dimethylformamide solution under different conditions. 2,3-Dihydro-1,3,4-thiadiazoles and triazolo[4,3-a]pyrimidine were obtained from reaction of hydrazonoyl halides with each of thioanilide and pyrimidine-2-thione, respectively. Structures of the newly synthesized compounds were elucidated on the basis of elemental analysis, spectral data, and alternative synthesis route whenever possible.

Full text of DOI:10.1002/hc.10222

Heteroatom Chemistry
Volume 15, Number 2, 2004
Synthesis of 2,3-Dihydro-1,3,4-thiadiazole,
Thiazole, and Triazolo[4,3-a]pyrimidine
Derivatives from Ethyl Benzoylacetate
Nora M. Rateb and Abdou O. Abdelhamid∗
Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt
Received 2 July 2003; revised 1 September 2003
2-(phenylcarbonyl)-3-sulfanylprop-2-enoate (1) to-
ward ethyl chloroacetate and hydrazonoyl halides.
ABSTRACT: Thiophene and thiazole derivatives
can be obtained from potassium salt of ethyl 3-oxo-
3-phenyl-2-[(phenylamino)thioxomethyl]propanoate
and ethyl chloroacetate in N,N-dimethylformamide
solution under different conditions. 2,3-Dihydro-
1,3,4-thiadiazoles and triazolo[4,3-a]pyrimidine were
obtained from reaction of hydrazonoyl halides
with each of thioanilide and pyrimidine-2-thione,
respectively. Structures of the newly synthesized
compounds were elucidated on the basis of elemental
analysis, spectral data, and alternative synthesis
RESULTS AND DISCUSSION
Ethyl 2-(4-ethoxy-3-phenyl(1,3-thiazolin-2-ylidene))-
3-oxo-3-phenylpropanoate (3) was claimed to be
obtained from the reaction of ethyl chloroacetate
with 1, the identity of the product from this reac-
tions has to be reinvestigated. The reaction of 1 with
ethyl chloroacetate in N,N-dimethylformamide af-
forded ethyl (2Z)-3-[(ethoxycarbonyl)-methylthio]-
3-(phenylamino)-2-(phenylcarbonyl)prop-2-enoate
(2) and not 3 [11]. Structure of 2 was confirmed
on the basis of elemental analyses, spectra, and
ꢀ
C
route whenever possible. 2004 Wiley Periodicals, Inc.
Heteroatom Chem 15:107–113, 2004; Published online
in Wiley InterScience (www.interscience.wiley.com). DOI
10.1002/hc.10222
1
chemical transformation. Thus, H NMR spectrum
showed signals at δ = 0.88 (t, 3H, CH2CH3), 1.25
(t, 3H, CH2CH3), 3.54 (s, 2H, SCH2), 3.98 (q, 2H,
CH2CH3), 4.20 (q, 2H, CH2CH3), 7.25–7.58 (m, 10H,
ArH’s), and 10.33 (s, 1H, NH). Its IR (cm−1) spectrum
showed bands at 3456 (NH), 1743, 1666 (CO’s), and
1542 (C C).
Compound 2 was converted to ethyl 5-(ethoxy-
carbonyl)-4-phenyl-2-(phenylamino)thiophene-3-
carboxylate (4) by boiling in ethanol containing
catalytic amount of piperidine, and ethyl 3-oxo-2-
[4-oxo-3-phenyl(1,3-thiazolidin-2-ylidene)]-3-phenyl-
propanoate (5) by treatment with conc. sulfuric acid
(Scheme 1).
INTRODUCTION
Thiazoles have found wide use as accelerators in
rubber vulcanization and also as antioxidants [1,2].
Also, thioanilides are versatile reagents, which have
been used as synthetic intermediate for hetero-
cyclic compounds, which possess expected biolog-
ical activity [3–6]. As an extension of our study
[7–10] and as a part of our program aiming at
the synthesis of different thiophenes, thiazoles, and
2,3-dihydro-1,3,4-thiadiazoles, we report here the re-
activity of potassium ethyl (2Z)-3-(phenylamino)-
Structures 4 and 5 were confirmed on the basis of
elemental analyses, spectra, and alternative synthe-
sis. 1H NMR spectrum of 4 showed signals at δ = 0.77
(t, 3H, CH2CH3), 1.02 (t, 3H, CH2CH3), 3.95 (q, 2H,
∗Correspondence to: Abdou O. Abdelhamid; e-mail: abdou
abdelhamid@yahoo.com.
2004 Wiley Periodicals, Inc.
c
ꢀ
107

108 Rateb and Abdelhamid
SCHEME 1
CH2CH3), 4.04 (q, 2H, CH2CH3), 7.16–7.45 (m, 10H,
ArH’s), and 10.54 (s, br, 1H, NH). Its IR (cm−1) re-
vealed bands at 3163 (NH), 1712, 1666 (CO’s), and
1596 (C C). 1H NMR spectrum of 5 showed signals
at δ = 1.01 (t, 3H, CH2CH3), 3.89 (s, 2H, CH2), 4.13 (q,
2H, CH2CH3), and 6.82–7.46 (m, 10H, ArH’s). Its IR
(cm−1) revealed bands at 1712, 1666 (CO’s), and 1596
(C C). MS spectrum of 5 showed peaks m/e 367, 291,
262, 234, 227, 190, 144, 105, and 77. More evidence
for structure 5 was obtained via reaction of 1 with
chloroacetyl chloride, which afforded identical prod-
uct in all respects (mp., mixed mp., and spectra) with
compound 5, and structure 6 was ruled out.
Also, compound 1 reacted with C-ethoxycar-
bonyl-N-phenylhydrazonoyl chloride 7a to afford
9a and ethyl 2-[5-(ethoxycarbonyl)-3-phenyl(1,3,4-
thiadiazolin-2-ylidene)]-3-oxophenylpropanoate
(10a) not as claimed [11] (Scheme 2). The reaction
takes place through intermediate 8, which converted
to 10 via elimination of aniline [12] or 9 via elimi-
nation of probably 11. Structure 9a was elucidated
on the basis of elemental analyses, spectral data,
and authentic sample [12]. 1H NMR spectrum of
10a showed signals at δ = 0.85 (t, 3H, CH2CH3),
1.39 (t, 3H, CH2CH3), 3.59 (q, 2H, CH2CH3), 4.47 (q,
2H, CH2CH3), and 7.26–7.47 (m, 10H, ArH’s). Mass
spectrum of 10a showed peaks at m/z 424, 351, 291,
270, 219, 146, 105, and 77. Analogy, C-acetyl-N-
phenylhydrazonoyl chloride reacted with 1 to afford
9b and 10b.
Compound 5 reacted with arenediazonium
chloride in pyridine to give ethyl 2-{5-[aza(aryl-
amino)methylene]-4-oxo-3-phenyl(1,3-thiazolidin-
2-ylidene)}-3-oxo-3-phenylpropanoate (13a and
13b) (Scheme 3). Structure of 13 was confirmed on
the basis of elemental analysis and spectral data.
1
Thus, H NMR spectrum of 13b showed signals at
δ = 1.03 (t, 3H, CH2CH3), 2.31 (s, 3H, 4-CH3C6H4),
4.14 (q, 2H, CH2CH3), 6.91–8.04 (m, 14H, ArH’s),
and 10.92 (s, 1H, NH).
Compound 5 reacted with the appropriate
(methylene)methane-1,1-dicarbonitrile in reflux
ethanol containing catalytic amount of piperidine
to yield ethyl 3-oxo-2-[4-oxo-3-phenyl-5-(arylmethy-
lene)(1,3-thiazolidin-2-ylidene)]-3-phenyl-propano-
ates (16) and not ethyl 2-[5-amino-6-cyano-3,7-
diphenyl(3,4,7,3a,7a-pentahydro-4-oxabenzothiazol-
2-ylidene)]-3-oxo-3-phenylpropanoates 15 on the
basis of elemental analysis, spectral data, and
alternative synthesis. Thus, 1H NMR spectrum of
16b showed signals at δ = 1.03 (t, 3H, CH2CH3),
2.43 (s, 3H, 4-CH3C6H4), 4.12 (q, 2H, CH2CH3), and
7.26–7.75 (m, 15H, ArH’s and CH). Its IR (cm−1)
revealed bands at 3028, 2900 (CH), 1706, 1693, 1674
(CO’s), and 1596 (C C) and no bands at 3100–3300
and 2000–2300 attributed the absence of each of

Synthesis of 2,3-Dihydro-1,3,4-thiadiazole, Thiazole, and Triazolo[4,3-a]pyrimidine Derivatives 109
SCHEME 2
SCHEME 3

110 Rateb and Abdelhamid
NH2 and CN groups [13]. MS spectrum of 16c
revealed peaks m/e at 490, 489, 418, 416, 339, 338,
314, 312, 248, 247, 169, 168, 133, 266, 105, and 77.
Compound 5 reacts with the appropriate aldehy-
des in ethanol containing catalytic amount of piperi-
dine afforded identical product in all respects (mp.,
mixed mp., and spectra) with the appropriate 16a–d
(Scheme 3).
hydroxide followed by iodomethane) reacted with 7b
in ethanolic triethylamine to give product identical
in all respects (mp., mixed mp., and spectra) with
20b.
Finally, the appropriate hydrazonoyl chloride
7a reacts with ethyl 4,6-diphenyl-2-thioxo-1,3,6-
trihydropyrimidine-5-carboxylate 21 [14] in refluxed
chloroform solution in presence of triethylamine
to give ethyl 5-(ethoxycarbonyl)-1,4,6-trihydro-
4,3a-dihydro-1,2,4-triazolino[4,3-a]pyrimidine-3-
carboxylate (23a). Structure of 23 was elucidated
on the basis of elemental analysis, spectral data,
and alternative synthesis. 1H NMR spectrum of
23a showed signals at δ = 0.92 (t, 3H, CH2CH3),
1.30 (t, 3H, CH2CH3), 3.90 (q, 2H, CH2CH3), 4.39
(q, 2H, CH2CH3), 5.68 (s, 1H, pyrimidine C-4), and
6.85–8.25 (m, 15H, ArH’s). Thus, ethyl 2-methylthio-
4,6-diphenyl-3,4-dihydropyrimidine-5-carboxylate
(24), which was prepared via methylation of 21 with
iodomethane in presence of sodium methoxide,
reacted with 7a to give identical product in all
respects (mp., mixed mp., and spectra) with 23a
(Scheme 4). Similarly, the appropriate hydrazonoyl
halides 7b–d react with 21 or 24 to afford 23b–d
respectively.
In contrast, compound 5 reacted with (2-
furylmethylene)methane-1,1-dicarbonitrile in reflux
ethanol in presence of catalytic amount of piperidine
to give ethyl 2-[(7R)-5-amino-6-cyano-7(2-furyl)-3-
phenyl(4H-pyrano[2,3-d]1,3-thiazolidin-2-ylidene)]-
3-oxo-3-phenylpropanoate (15a). Structure of the
latter was confirmed on the basis of elemental
1
analysis and spectral data. Its H NMR spectrum
showed signals at δ = 0.91 (t, 3H, CH2CH3), 4.04 (q,
2H, CH2CH3), 6.42 (s, 1H, pyran C-4), 6.49–7.53 (m,
13H, ArH’s and furan protons), and 8.12 (s, br, 2H,
NH2).
Also, treatment of 5 with phenyl isothio-
cyanate in presence of potassium hydroxide to
give thioanilide 17, which converted to 2,3-dihydro-
1,3,4-thiadiazoles 20a–d, respectively via its reac-
tion with the appropriate hydrazonoyl halides 7a–d
(Scheme 3). Structure 20 was confirmed on the basis
of elemental analysis, spectral data, and alternative
The formation of 23 can be explained via
1,3-dipolar cycloaddition or 1,3-addition of nitrile
imide (prepared in situ from hydrazonoyl halides
7 with triethylamine or sodium ethoxide) to C S
of pyrimidine-2-thione 21 to give intermediate 22,
with ring opening and ring closure to afford the fi-
nal products 23 by elimination of hydrogen sulfide
(Scheme 4).
1
route. H NMR spectrum of 20b showed signals at
δ = 1.24 (t, 3H, CH2CH3), 2.41 (s, 3H, CH3CO), 4.19
(q, 2H, CH2CH3), and 6.84–7.81 (m, 15H, ArH’s).
Also, methyl carbodithioate 18 (which was pre-
pared via reaction of 5 with carbon disulfide in N,N-
dimethylformamide solution containing potassium
SCHEME 4

Synthesis of 2,3-Dihydro-1,3,4-thiadiazole, Thiazole, and Triazolo[4,3-a]pyrimidine Derivatives 111
EXPERIMENTAL
Ethyl 5-(Ethoxycarbonyl)-4-phenyl-2-
(phenylamino)thiophene-3-carboxylate (4)
All melting points were determined on an elec-
trothermal apparatus and are uncorrected. IR spec-
tra were recorded (KBr discs) on a Shimadzu FT-IR
Compound 2 (1 g) was refluxed in ethanol (20 ml)
containing 2 drops of piperidine for 1 h. The re-
action mixture was cooled and the resulting solid
was collected and crystallized from ethanol to give
4 (Table 1).
1
8201 PC spectrophotometer. H NMR spectra were
recorded in CDCl3 and (CD3)2SO solutions on a Var-
ian Gemini 300 MHz spectrometer and chemical
shifts were expressed in δ units using TMS as internal
reference. Mass spectra were recorded on a GC-MS,
HB, 5988A. Elemental analyses were carried out at
the Microanalytical Center of the Cairo University.
Hydrazonoyl halides 7a–d were prepared as previ-
ously reported [15–19].
Ethyl 3-Oxo-2-[4-oxo-3-phenyl(1,3-thiazolidin-
2-ylidene)]-3-phenylpropanoate (5)
Method A. A mixture of ethyl benzoylacetate
(1.92 g, 0.01 mol), phenyl isothiocyanate (1.35 g,
0.01 mol), and potassium hydroxide (0.56 g,
0.01 mol) in N,N-dimethylformamide (20 ml) was
stirred for 3 h at room temperature. Chloroacetyl-
choride (1.12 g, 0.01 mol) was added and stir-
ring was continued for 2 h. The reaction mixture
was diluted with water, the solid precipitate was
collected and crystallized from ethanol to give 5
(Table 1).
Ethyl (2Z)-3-[(Ethoxycarbonyl)methylthio]-
3-(phenylamino)-2-(phenylcarbonyl)prop-2-
enoate (2)
A mixture of ethyl benzoylacetate (1.92 g, 0.01 mol),
phenyl isothiocyanate (1.35 g, 0.01 mol), and
potassium hydroxide (0.56 g, 0.01 mol) in N,N-
dimethylformamide (20 ml) was stirred for 3 h
at room temperature. Ethyl chloroacetate (1.2 g,
0.01 mol) was added and stirring was continued for
2 h. The reaction mixture was diluted with water and
the solid precipitate was collected and crystallized
from ethanol to give 2 (Table 1).
Method B. A mixture of 2 (1 g) in conc. sulfuric
acid (10 ml) was stirred for 1 h at room temperature,
and then poured onto crushed ice (30 g). The result-
ing solid was collected by filtration, washed with wa-
ter, and crystallized from ethanol to give 5.
TABLE 1 Characterization Data of the Newly Synthesized Compounds
Calcda (%)
Compd.
No.
mp. (◦C),
Solvent
Color,
Yield (%)
Mol. Formula
(Mol. Wt.)
C
H
N
S
2
137–140, EtOH
98–100, EtOH
175–177, EtOH
143–146, EtOH
197–198, EtOH
208–210, EtOH
242–244, EtOH
255–257, EtOH
White, 55
White, 75
Yellow, 79
Yellow, 80
Yellow, 75
Brown, 75
Orange, 73
Brown, 77
C22H23NO5S (413.50)
63.91 (64.00) 5.61 (5.70) 3.39 (3.40)
66.82 (66.80) 5.35 (5.30) 3.54 (3.50)
65.38 (65.20) 4.66 (4.50) 3.81 (3.70)
7.75 (7.80)
8.11 (8.10)
8.73 (8.60)
7.55 (7.50)
8.13 (8.10)
6.80 (6.60)
6.60 (6.60)
6.27 (6.40)
7.04 (7.00)
6.83 (6.80)
6.54 (6.50)
4
C
C
C
C
C
C
C
C
C
C
22H21NO4S (395.48)
20H17NO4S (367.43)
22H20N O5S (424.48) 62.25 (62.30) 4.75 (4.60) 6.60 (6.50)
21H18N22O4S (394.45) 63.95 (63.80) 4.60 (4.40) 7.10 (6.90)
26H21N3O4S (471.54) 66.23 (66.20) 4.49 (4.30) 8.91 (8.80)
27H23N3O4S (485.57) 66.79 (66.80) 4.77 (4.80) 8.65 (8.70)
28H21N3O5S (511.56) 65.74 (65.60) 4.14 (4.00) 8.21 (8.30)
27H21NO4S (455.54)
28H23NO4S (469.56)
27H20ClNO4S (489.98) 66.19 (66.00) 4.11 (4.00) 2.86 (2.90)
5
10a
10b
13a
13b
15a
16a
16b
16c
16d
17
219–220, Dioxane Yellow, 85
257–260, Dioxane Yellow, 83
265–267, Dioxane Yellow, 87
71.19 (71.00) 4.65 (4.60) 3.07 (3.00)
71.62 (71.60) 4.94 (4.90) 2.98 (3.00)
237–239, Dioxane Orange, 85 C25H19NO4S2 (461.56) 65.06 (65.00) 4.15 (4.00) 3.03 (3.00) 13.89 (14.00)
153–155, EtOH
285–286, DMF
165–167, EtOH
265–266, EtOH
257–260, AcOH
278–280, DMF
283–285, DMF
146–148, EtOH
129–130, EtOH
149–151, EtOH
159–161, EtOH
156–157, EtOH
Orange, 75
Yellow, 56
Yellow, 80
Yellow, 85
Orange, 75
Violet, 85
Yellow, 83
Yellow, 85
Yellow, 80
Yellow, 83
C
C
C
C
C
C
C
C
27H22N2O4S2 (502.62) 64.52 (64.30) 4.41 (4.20) 5.57 (5.50) 12.76 (12.50)
23H19NO4S3 (457.59) 57.75 (57.60) 4.19 (4.00) 3.06 (3.00) 21.02 (21.00)
23H21NO4S3 (471.62) 58.58 (58.50) 4.49 (4.40) 2.97 (3.00) 20.40 (20.40)
31H25N3O6S2 (599.69) 62.09 (62.00) 4.20 (4.00) 7.01 (7.00) 10.69 (10.60)
30H23N O5S (569.66) 63.25 (63.20) 4.07 (4.10) 7.38 (7.20) 11.26 (11.20)
35H25N3O5S2 (631.73) 66.55 (66.30) 3.99 (4.00) 6.65 (6.40) 10.15 (10.00)
18
19
20a
20b
20c
20d
23a
23b
23c
23d
24
35H26N3O5S2 (646.75) 65.00 (65.00) 4.05 (4.00) 8.66 (8.60)
9.92 (9.90)
2
29H26N44O4 (494.55)
70.43 (70.30) 5.30 (5.20) 11.33 (11.20)
69.99 (70.00) 5.03 (5.00) 11.66 (11.60)
72.40 (72.30) 5.21 (5.10) 12.06 (12.00)
75.27 (75.10) 4.98 (5.00) 10.64 (10.60)
C28 24
H
N4O4 (480.53)
C
28H24N4O3 (464.53)
H N4O3 (526.00)
Orange, 75 C33 26
White, 80
C
20H20N2O2S (352.46) 68.16 (68.00) 5.72 (5.60) 7.95 (8.00)
9.10 (9.00)
aThe values given in parentheses indicate found value.

112 Rateb and Abdelhamid
was added and stirring was continued for 2 h. The re-
action mixture was diluted with water; the so formed
solid was collected and crystallized from ethanol to
give 18 and 19, respectively (Table 1).
Ethyl 2-[5-Substituted-3-phenyl(1,3,4-
thiadiazolin-2-ylidene)]-3-
oxophenylpropanoates 10a,b
A mixture of ethyl benzoylacetate (1.92 g, 0.01 mol),
phenyl isothiocyanate (1.35 g, 0.01 mol), and potas-
sium hydroxide (0.56 g, 0.01 mol) in N,N-dimethyl-
formamide (20 ml) was stirred for 3 h at room
temperature. The appropriate hydrazonoyl chlorides
7a,b (0.01 mol) was added and stirring was contin-
ued for 4 h. The reaction mixture was diluted with
water; the resulting solid was collected to give 9a and
10a, and the filtrate was diluted with water to give
9b and 10b, respectively (Table 1).
2,3-Dihydro-1,3,4-thiadiazoles 20a–d
A mixture of 5 (1.8 g, 0.005 mol), phenyl isothio-
cyanate (0.65 g, 0.005 mol), and potassium hydrox-
ide (0.28 g, 0.005 mol) in N,N-dimethylformamide
(20 ml) was stirred for 3 h at room temperature. The
appropriate hydrazonoyl halides 7a–d (0.005 mol)
was added and stirring was continued for 2 h.
The reaction mixture was diluted with water and
the resulting solid was collected and crystallized
from the proper solvent to afford 2,3-dihydro-1,3,4-
thiadiazoles 20a–d, respectively (Table 1).
Ethyl 2-{5-[Aza(arylamino)methylene]-4-oxo-3-
phenyl(1,3-thiazolidin-2-ylidene)}-3-oxo-3-
phenylpropanoates 13a,b
Ethyl 2-Methylthio-4,6-diphenyl-3,4-dihydro-
pyrimidine-5-carboxylate (24)
An aqueous solution of the appropriate arenediazo-
nium chloride (0.005 mol) was added portionwise to
a stirred solution of 5 (1.8 g, 0.005 mol) in pyridine
(30 ml) at 0◦C. The reaction mixture was stirred for
3 h, the resulting solid was collected, washed with
water, and crystallized from ethanol to give 13a,b
respectively (Table 1).
Iodomethane (0.006 mol) was added portion-
wise with stirring to a mixture of compound 21
(0.005 mol) and sodium ethoxide solution [prepared
by dissolving sodium metal (0.11 g atom, 0.005 mol)]
in ethanol (20 ml) for 4 h. The reaction mixture was
left overnight at room temperature and then the pre-
cipitate was collected and crystallized from ethanol
to give 24 (cf. Table 1). Its 1H NMR spectrum showed
signals at δ = 1.30 (t, 3H, CH2CH3), 2.00 (s, 3H, CH3),
4.20 (q, 2H, CH2CH3), 4.59 (s, 1H), 7.04–7.30 (m,
10H, ArH’s), and 9.56 (s, 1H, NH).
Ethyl 3-Oxo-2-[4-oxo-3-phenyl-5-(arylmethylene)-
(1,3-thiazolidin-2-ylidene)]-3-phenylpropanoates
16a–d
A mixture of 5 (1.8 g, 0.005 mol) and the appropriate
aldehydes (0.005 mol) in ethanol (20 ml) contain-
ing catalytic amount of piperidine was refluxed for 1
h. The resulting solid was collected and crystallized
from dioxane to give 16a–d (Table 1).
Ethyl 5-Substituted-1,4,6-trihydro-4,3a-dihydro-
1,2,4-triazolino[4,3-a]pyrimidine-3-carboxylates
23a–d
Ethyl 3-Oxo-2-{4-oxo-3-phenyl-5-[(phenyl-
amino)thioxomethyl](1,3-thiazolidin-2-
ylidene)}-3-phenylpropanoate (17)
Method A. A mixture of 21, the appropri-
ate hydrazonoyl halides 7a–d, and triethylamine
(0.005 mol, each) in chloroform (20 ml) was refluxed
for 10 h, then the solvent was evaporated under re-
duced pressure. The oil residue was triturated with
ethanol (10 ml). The resulting solid was collected and
crystallized from ethanol to give 23a–d (Table 1).
A mixture of 5 (1.8 g, 0.005 mol), phenyl isothio-
cyanate (0.65 g, 0.005 mol), and potassium hydrox-
ide (0.28 g, 0.005 mol) in N,N-dimethylformamide
(20 ml) was stirred for 3 h. The reaction mixture was
diluted with water and acidified with acetic acid. The
solid was collected and crystallized from ethanol to
give 17 (Table 1).
Method B. A mixture of 24, the appropri-
ate hydrazonoyl halides 7a–d, and triethylamine
(0.005 mol, each) in ethanol was refluxed for 2 h. The
resulting solid was collected and crystallized from
ethanol to give 23a–d, respectively (Table 1).
Methyl Carbodithioates 18 and 19
A mixture of 5 (1.8 g, 0.005 mol), carbon disul-
fide (0.38 g, 0.005 mol), and potassium hydroxide
(0.28 g, 0.005 mol) or (0.56 g, 0.01 mol) in N,N-
dimethylformamide (20 ml) was stirred for 3 h.
Iodomethane (0.7 g, 0.005 mol) or (1.4 g, 0.01 mol)
REFERENCES
[1] Kurzer, F. Org Compd Sulfur Selenium Tellurium
1973, 2, 587.

Synthesis of 2,3-Dihydro-1,3,4-thiadiazole, Thiazole, and Triazolo[4,3-a]pyrimidine Derivatives 113
[2] Kurzer, F. Org Compd Sulfur Selenium Tellurium
[10] Abdelhamid, A. O.; Metwally, N. H.; Bishai, N.
S. J Chem Res(S) 2000, 462; Abdelhamid, A. O.;
Metwally, N. H.; Bishai, N. S. J Chem Res(M) 2000,
1144.
[11] Elwan, N. M. Int J Chem 1994, 5, 27.
[12] Abdelhamid, A. O.; El-Kathiri, M. N. Phosphorus,
Sulfur Silicon 1996, 119, 181.
1973, 2, 653.
[3] Lowe, P. A. In Heterocyclic Chemistry; Suschitzky,
H.; Meth-Cohn, O. (Eds.); Chemical Society: London,
1980; Vol. 1, p. 119.
[4] Metzger, J. V. Chem Heterocycl Compound 1979, 34,
1.
[5] Iddon, B.; Alowe, P. Org Compd Sulfur Selenium Tel-
lurium 1977, 4, 386.
[6] Kurzer, F. Org Compd Sulfur Selenium Tellurium
1975, 3, 617.
[7] Abdelhamid, A. O.; Abdelgawad, S. M.; El-Sharnoby,
S. F. Phosphorus Sulfur 2002, 177, 2699.
[8] Rateb, N. M.; Abdel-Riheem, N. A.; Al-Atoom, A.
A.; Abdelhamid, A. O. Phosphorus Sulfur 2003, 178,
1101.
[9] Abdel-Riheem, N. A.; Rateb, N. M.; Al-Atoom, A. A.;
Abdelhamid, A. O. Heteroat Chem 2003, 14, 421.
[13] Bellamy, L. J. The Infrared Spectra of Complex
Molecules, 3rd ed.; John Wiley: New York, 1975; p.
150.
[14] Sherif, S. M.; Youssef, M. M.; Mobarak, K. M.; Abdel-
Fattah, A. M. Tetrahedron 1993, 49, 9561.
[15] Fravel, G. Bull Soc Chim Fr 1904, 31, 150.
[16] Fusco, R.; Romani, R. Gazz Chim Ital 1948, 78, 322.
[17] Eweiss, N. E.; Osman, A. Tetrahedron Lett 1979, 1169.
[18] Shawali, A. S.; Abdelhamid, A. O. Bull Chem Soc Jpn
1976, 49, 321.
[19] Shawali, A. S.; Osman, A. Tetrahedron 1971, 27, 2517.