Facile synthesis of heterocycles via 2-picolinium bromide and antimicrobial activities of the products

Article abstract of DOI:10.3390/molecules13051066

The 2-picolinium N-ylide 4, generated in situ from the N-acylmethyl-2- picolinium bromide 3, underwent cycloaddition to N-phenylmaleimide or carbon disulfide to give the corresponding cycloadducts 6 and 8, respectively similar reactions of compound 3 with

Full text of DOI:10.3390/molecules13051066

Molecules 2008, 13, 1066-1078; DOI: 10.3390/molecules13051066
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.org/molecules
Article
Facile Synthesis of Heterocycles via 2-Picolinium Bromide and
Antimicrobial Activities of the Products
Elham S. Darwish
Department of Chemistry, Faculty of Science, University of Cairo, Giza, 12613, Egypt; E-mail:
elham_darwish@yahoo.com
Received: 3 April 2008; in revised form: 24 April 2008 / Accepted: 24 April 2008 / Published: 1 May
2008
Abstract: The 2-picolinium N-ylide 4, generated in situ from the N-acylmethyl-2-
picolinium bromide 3, underwent cycloaddition to N-phenylmaleimide or carbon disulfide
to give the corresponding cycloadducts 6 and 8, respectively similar reactions of
compound 3 with some electron-deficient alkenes in the presence of MnO2 yielded the
products 11 and 12. In addition, reaction of 4 with arylidene cyanothioacetamide and
malononitrile derivatives afforded the thiophene and aniline derivatives 15 and 17,
respectively. Heating of picolinium bromide 3 with triethylamine in benzene furnished 2-
(2-thienyl)indolizine (18). The structures of the isolated products were confirmed by
1
elemental analysis as well as by H- and 13C-NMR, IR, and MS data. Both the
stereochemistry and the regioselectivity of the studied reactions are discussed. The
biological activity of the newly synthesized compounds was examined and showed
promising results.
Keywords: Dihydrothiophene, indolizine, aniline derivatives, biological activity
Introduction
Many thiophene derivatives have been reported to exhibit interesting pharmaceutical properties,
including antimicrobial [1], anticancer [2], anti-inflammatory [3], bacteriostatic and fungistatic activity
[4]. Some other derivatives exhibit strong inhibition of NHE-1 and cardioprotective efficacy [5].
Indolizine derivatives also possess valuable biological activities and have been studied for their

Molecules 2008, 13
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psychotropic, anti-inflammatory, analgesic, antimicrobial, antiexudative and hypoglycemic properties
[6-9]. Herein, the synthesis of some new aromatic and heteroaromatic compounds having a thiophene
moiety utilizing the highly reactive nitrogen ylide 4 is described. Some of the newly synthesized
compounds were tested for their antimicrobial activities.
Results and Discussion
The required starting material 2-bromoacetylthiophene (1) was prepared as previously described
[4]. Treatment of 1 with 2-picoline (2) in refluxing dry THF afforded the 2-picolinium salt 3 in 80%
1
yield (Scheme 1). The structure of product 3 was elucidated by its spectroscopic (MS, IR, H-NMR)
and elemental analysis data (see Experimental).
Scheme 1
Br
Br
+
N
N+
S
S
1
O
O
3
Me
2
Me
Initially, the cycloaddition reactions of the N-ylide 4, generated in situ by base-catalyzed
dehydrobromination of 3, with symmetrical dipolarophiles were examined (Scheme 2). Thus, reaction
of the salt 3 with N-phenylmaleimide (5) in refluxing benzene in the presence of triethylamine
afforded one product, as evidenced by tlc analysis. The structure of the isolated product proved to be 6,
as evidenced by its spectroscopic and elemental analysis data. Thus, its 1H-NMR spectrum in DMSO-
d6 revealed two characteristic doublet signals at δ = 4.28 and 5.72 ppm, with a coupling constant (J) of
7.6 Hz, assignable to the 3a and 9b protons. This observed value of the coupling constant indicates that
the product 6 has cis-configuration [10-12] and this, in turn, suggests that the cycloaddition of the N-
ylide 4 to N-phenylmaleimide 5 is a concerted cycloaddition.
Also, treatment of 3 with carbon disulfide in dimethylformamide in the presence of potassium
carbonate at room temperature yielded one product, identified as 8 on the basis of its spectroscopic
1
data (1H-NMR, MS and IR) and elemental analysis. For example, its H-NMR spectrum showed a
D2O-exchangable singlet signal at δ = 11.80 ppm, assignable to the SH proton. This finding suggests
that the isolated cycloadduct exists predominantly in the depicted thiol tautomeric form 8.
Next, in order to shed some light on the regiochemistry of the cycloaddition of the N-ylide 4, its
reactions in refluxing dry benzene in the presence of triethylamine and manganese dioxide with each
of ω-nitrostyrene (9a), benzylideneacetophenone (9b) and ethyl α-cyano-4-chlorocinnamate (9c) were
investigated (Scheme 2). In each case, only one product was isolated, as evidenced by tlc analysis,
indicating that such cycloadditions are regioselective. On the basis of their spectroscopic (1H-NMR,
MS and IR) and elemental analysis data (see Experimental) the isolated products were identified as
12a, 12b and 11c, respectively and the other regioisomeric structures 13 were discarded. To account
for the formation of the latter products 12a,b and 11a,b it is suggested that the N-ylide 4, generated in

Molecules 2008, 13
1068
situ by dehydrobromination of 3, undergoes cycloaddition to the C=C double bond to form the
respective cycloadduct 10, which underwent in situ oxidation to form 11 as end product. The products
11a,b underwent further in situ oxidation and afforded 12a,b, respectively. The regioselectivity in the
studied reactions of 4 with 9a-c can be satisfactorily rationalized by the electrostatic attraction during
the approach of both reagents. As shown in Scheme 3, the electrostatic interaction will favor bonding
of the α- and β-carbon atoms of each of the used dipolarophiles 9 with the ring and exocyclic carbon
atoms of the N-ylide 4, respectively. Such approach will lead to the cycloadducts 10, rather than the
regioisomers 13 [13].
Scheme 2
Br
Het-CO-CH2 N+
3
Me
O
H
H
Et3N
-HBr
N Ph
O
1
H
H
9
9a
9b
+
_
8
2
O
N Ph
3
Het-CO-CH N
N
4
7
5
5
3a
6
H
H
Me
4
O
6
Me
COHet
S=C=S
7
S
S
N
N
SH
COHet
S
H
Me
Me
COHet
8
X
Ar
X
H
X
[O]
W
X=H
[O]
W
W
H
N
H
Ar
N
Ar
9a-c
H
Me
Me
COHet
11
COHet
W
10
N
Ar
COHet
12
Het = 2-thienyl
Ar/X/W: a, Ph/H/NO2; b,Ph/H/PhCO; c, 4-ClC6H4/CN/EtOOC
Me

Molecules 2008, 13
1069
Scheme 3
Me
_
3
CO-Het
N
[O]
+
H
10
+
11
- HBr
Et3N
_
X
Ar
9
W
4
Me
Me
_
CO-Het
N
+
_
X
N
CO-Het
+
H
W
X
H
Ar
Ar
13
W
Het = 2-thienyl
Ar/X/W: a, Ph/H/NO2; b,Ph/H/PhCO; c, 4-ClC6H4/CN/EtOOC
The reaction of the N-ylide 4 with each of arylidenecyanothioacetamides 14a,b in refluxing ethanol
in the presence of Et3N was found to afford the corresponding trans-4,5-dihydrothiophene derivatives
15a,b, respectively (Scheme 4). The IR spectra of these products showed absorption bands in the υ
3360 – 3364, 3192 – 3212, 2215 and 1720 – 1723 cm-1 regions, assignable to NH2, CN and CO groups,
1
respectively. Their H-NMR in DMSO-d6 revealed two characteristic doublet signals (J = 17 Hz) in
the δ = 4.0 – 5.0 ppm region, due to the 4-CH and 5-CH protons of the dihydrothiophene ring. The
suggested pathway for the formation of 15 from 3 and 14 is depicted in Scheme 4. This pathway is
analogous to that reported in the literature for the preparation of trans-4,5-dihydrothiophene
derivatives from pyridinium salts and benzylidenecyanothioacetamides [14-17].
Scheme 4
3
S
NH2
NH2
CN
H
S
+
H
Et3N
-HBr
CN
Ar
Ar
CN
14
- 2-picoline
4
N
Et3N
Het-OC
S
NH2
15
Ar
H
CO-Het
Me
Het = 2-thienyl
14,15; a, Ar = 4-BrC6H4
b, Ar = 4-CH3OC6H4

Molecules 2008, 13
1070
Reactions of 3 with each of the arylidenemalononitrile derivatives 16a-c in refluxing pyridine were
also investigated (Scheme 5). In our hands, these reactions afforded in each case one product, as
evidenced by tlc, which proved to be the respective aniline derivatives 17a-c.
Scheme 5
CN
NC
3
CN
NC
CN
CN
CN
CN
Ar
R
Ar
Ar
15
Ar
R
H
Ar
16
Et3N
-HBr
H
H
CN
4
NC
Me
N
Me
N
pyridine
+
+
A
CN
CN
NC
Ar
H
CN
NC
H
Ar
R
Ar
CN
17
Ar
Ar
R
Ar
H
H
CN
-2-picoline
-HCN
R
CN
NC
+
NH2
NH
+
H
Me
N
Me
N
R = 2-thenoyl
B
16-17; a, Ar = phenyl
b, Ar = 2-furyl
c, Ar = 2-thienyl
For example, the corresponding IR spectra revealed in each case four characteristic bands due to
NH2, CN and CO groups in the ν 3326 – 3342, 3104 – 3205, 2197 – 2211 and 1658 – 1667 cm-1
regions, respectively. Their mass spectra showed the molecular ion peaks at the expected m/z values
(see Experimental). To account for the formation of 17, the reaction mechanism outlined in Scheme 5
is suggested.
According to this mechanism, the reaction starts with nucleophilic attack of the N-ylide at the β-
carbon atom of 16 to form the intermediate A, which in turn adds to another arylidenemalonitrile
molecule to give the intermediate B. The latter undergoes concurrent cyclization and elimination of
picoline to give 17 as end product [18,19].
Finally, when the salt 3 was heated in benzene in the presence of triethylamine, it yielded a product
that was identified as 2-(2-thienyl)indolizine (18). A plausible pathway leading to the latter product is
shown in Scheme 6. The structure of product 18 was elucidated by its spectroscopic (MS, IR, 1H- and
13C-NMR) and elemental analysis data. Its IR spectrum revealed the absence of the carbonyl group,
but showed bands due to C=C stretching at υ = 1626 cm-1.

Molecules 2008, 13
1071
Scheme 6
H
Br
H
H
Et3N
..
+
N+
N
S
N
S
O
3
S
- HBr
O
O
Me
H
H
H
N
H
H
N
- H2O
S
S
HO
H
18
The electronic absorption spectra of compounds 3, 6, 8, 11a-b, 12c, 15a-b, 17a-c and 18 in ethanol
were recorded and the data are given in Table 1.
Table 1: Electronic Absorption and Spectral Data of the Compounds 3-18 in ethanol.
Cpd. no.
λ
max (log ε)
Cpd. no.
15a
λmax (log ε)
3
6
290 (4.67), 265 (4.93)
347 (3.90), 269 (4.30), 224 (4.35
345 (4.09), 257 (4.84), 229 (4.83)
351 (4.28), 247 (4.87)
296 (4.28), 260 (4.43)
15b
8
400 (4.49), 354 (4.60), 267 (4.88)
299 (4.50), 247 (4.83)
17a
11c
12a
12b
17b
358 (4.06), 260 (4.60
348 (4.38), 295 (4.65), 248 (4.93)
378 (4.06), 303 (4.79), 245 (5.05)
17c
295 (4.00), 265 (4.54), 230 (4.64)
310 (3.95), 264 (4.62)
18
Antimicrobial activity.
Most of the compounds were tested in vitro against a Gram negative bacterium [Escherichia coli
anaerobic (EC)], a Gram positive bacterium [Staphylococcus albus (SA)] and for antifungal activity
against Candida albicans (CA) and Aspergillus flavus (AF). The antibiotics ampicillin and tetracycline
were used as references to evaluate the potency of the tested compounds under the same conditions.
The solvent used was DMSO and the concentration of the sample used is 100 µg/mL. The test results
are summaized in Table 2. They reveal that all compounds exhibited moderate activity against the two
tested bacteria species and Candida albicans.

Molecules 2008, 13
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Table 2. Antibacterial and Antifungal Activities of the Synthesized Compounds a.
Inhibition Zone Diameter (mm/mg tested compound)
Gram (-)
(EC)
++
Gram (+)
(SA)
++
Fungi
Compd. No.
(AF)
++
(CA)
++
6
++
++
–
++
8
++
++
++
11c
–
–
–
–
–
–
–
++
++
++
++
++
++
++
++
++
++
++
++
++
+
12a
12b
15a
17a
17b
18
++
++
++
++
tetracyclin
ampicillin
+++
+++
+++
+++
a) + = low activity, ++ = moderate activity, +++ = high activity, – = no activity.
Conclusions
The synthesis of new indolizine derivatives by cycloaddition of the 2-picolinium N-ylide 4 with N-
phenylmaleimide, carbon disulfide, and electron-deficient alkenes to give the corresponding
cycloadducts 6, 8, 11 and 12 is reported. Also, reaction of 4 with arylidene derivatives of
cyanothioacetamide and malononitrile afforded the thiophene and aniline derivatives 15 and 17. A
novel synthesis of new indolizine derivatives by heating of picolinium bromide 3 with triethylamine in
benzene furnished 2-(2-thienyl) indolizine (18). The structures of all new synthesized compounds were
established from their spectral data and elemental analysis. Additionally, the antimicrobial activity of
selected compounds was examined.
Experimental
General
All melting points were determined on an Electrothermal Gallenkamp apparatus and are
uncorrected. The IR spectra (KBr disks, cm-1) were measured on a Pye-Unicam SP300 instrument in
1
potassium bromide discs. The H- and 13C-NMR spectra were recorded in DMSO-d6 on a Varian
Mercury VXR-300 spectrometer operated at 300 and 75.46 MHz, respectively. The mass spectra were
recorded on a GCMS-Q1000-EX Shimadzu and GCMS 5988-A HP spectrometers, the ionizing voltage
was 70 eV. Electronic absorption spectra were recorded on Perkin-Elmer Lambada 40
spectrophotometer. Elemental analyses were carried out by the Microanalytical Center of Cairo
University, Giza, Egypt. The starting materials 2-bromoacetylthiophene (1) [4], N-phenylmaleimide
(5) [20], ethyl (4-chlorophenylmethylene)cyanoacetate 9c, benzylidene acetophenone and 2-

Molecules 2008, 13
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substituted 3-aryl-or heteroarylprop-2-ene nitriles 16 and 14, were prepared as previously reported in
the literature [21].
1-(Thiophen-2-yl)-1-oxo-ethane-2-picolinium bromide (3)
2-picoline (0.93 g, 10 mmol) was added to a solution of 2-bromoacetylthiophene (1) (2.05 g, 10
mmol) in dry THF (50 mL), the mixture was refluxed for 30 min and then left to cool. The solid was
filtered off, washed with ether, and dried to afford the title compound 3 as yellowish white crystals;
o
1
mp 110-112 C (from EtOH); yield 80%; IR: ν = 1672 (CO); H-NMR: δ (ppm) = 2.41 (s, 3H, CH3),
4.89 (s, 2H), 7.09-7.88 (m, 3H), 7.94-8.02 (m, 3H), 8.61 (d, 1H); MS m/z (%) = 299 (M++1, 10.5), 298
(M+, 22.6), 111 (100.0), 92 (33.7), 83 (31.1), 64 (15.7); Anal. Calcd. for C12H12BrNOS (298.20): C,
48.33; H, 4.06; Br, 26.80; N, 4.70; S, 10.75%. Found: C, 48.25; H, 3.69; Br, 26.22; N, 4.24; S, 10.63.
6-Methyl-2-phenyl-4-(2-thienylcarbonyl)-3a,4,9a,9b-tetrahydro-1H-pyrrolo[3,4-a]indolizine-1,3(2H)
dione (6)
To a mixture of 3 (0.298 g, 1 mmol) and the N-phenylmaleimide (5) (0.173 g, 1 mmol) in benzene
(30 mL) was added triethylamine (0.15 mL, 1.5 mmol). The mixture was refluxed for 6 hours while
stirring, then cooled. The precipitated salt was filtered off and the filtrate was evaporated under
vacuum. The residue was treated with methanol and the solid formed was filtered and crystallized from
ethanol to give the product 6 as pale yellow crystals; mp 218 oC; yield 80%; IR: ν = 1665, 1709, 1776
(3CO) cm-1; 1H-NMR: δ (ppm) = 2.48 (s, 3H, CH3), 4.28 (d, 1H, J = 7.6 Hz ), 4.85 (d, 1H, J = 3.8 Hz),
5.54 (d, 1H, J = 3.8 Hz ), 5.72 (d, 1H, J = 7.6 Hz), 5.96-6.65 (m, 3H), 6.68 (d, 2H), 6.96 (dd, 2H), 7.72
(dd, 1H), 7.85-8.02 (m, 3H); MS: m/z (%)= 390 (M+, 19.4), 388 (10.6), 265 (10.2), 173 (10.7), 158
(22.2), 111 (100.0), 104 (12.5), 91 (35.8), 83 (14.0), 77 (15.4%), 64 (13.8); Anal. Calcd. for
C22H18N2O3S (390.46): C, 67.67; H, 4.65; N, 7.17; S, 8.21%. Found: C, 67.11; H, 4.28; N, 7.24; S,
8.11.
2-Mercapto-5-methyl-8aH-[1,3]thiazolo[3,2-a]pyridin-3-yl)(2-thienyl)methanone (8)
To a stirred suspension of 3 (0.59 g, 2 mmol) in dimethylformamide (20 mL) and potassium
carbonate (0.28 g), carbon disulphide (7) (4 mL) was added, and the mixture was stirred for 20 hours.
The reaction mixture was diluted with water and the so-formed precipitate was filtered off and
crystallized from ethanol to afford compound 8 as yellow crystals; mp 160-161 oC; yield 60%; IR: ν =
1662 (CO); 1H-NMR: δ (ppm) = 2.49 (s, 3H, CH3), 5.91 (s, 1H), 6.15-6.58 (m, 3H), 6.95-8.21 (m, 3H),
11.80 (s, 1H, SH); 13C-NMR: δ (ppm) = 19.27, 55.99, 115.51, 118.05, 124.23, 127.18, 130.08, 135.96,
138.48, 141.64, 146.14, 148.28, 188.97 (CO); MS: m/z (%) = 294 (M++1, 10.6), 293 (M+, 35.6), 181
(85.4), 111 (100), 92 (23.6), 83 (22.5), 75 (14.2), 63 (11.3); Anal. Calcd. for C13H11NOS3 (293.43): C,
53.21; H, 3.78; N, 4.77; S, 32.78%. Found: C, 53.38; H, 3.65; N, 4.88; S, 32.51.

Molecules 2008, 13
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General procedure for the preparation of the indolizine derivatives 11c and 12a,b
To a mixture of 1-(thiophene-2-yl)-1-oxo-ethane-2-picolinium bromide (3) ( 0.298 g, 1 mmol) and
the nitrostyrene (9a), benzylideneacetophenone (9b) or ethyl (4-chlorobenzylidene) cyanoacetate (9c)
(6 mmol) in benzene (30 mL), triethylamine (0.15 mL, 1.5 mmol) and manganese dioxide (0.7 g, 8
mmol) were added. The mixture was refluxed for 6 hours then cooled to room temperature. The
precipitate was filtered, and the filtrate was evaporated under vacuum. The residue was treated with
methanol and the solid precipitate was filtered off, washed with methanol, and dried. Crystallization
from ethanol afforded the corresponding indolizine derivatives 11c and 12a-c respectively. The
physical constants and spectroscopic data of the isolated products11c and 12a-c are given below.
Ethyl 2-(4-chlorophenyl)-1-cyano-5-methyl-3-(2-thienylcarbonyl)-1,8a-dihydroindolizine-1-carboxyl-
ate (11c): yellow crystals; mp 200 oC; yield 75%; IR: ν = 2217 (C=N), 1725, 1663 (2CO); 1H-NMR: δ
(ppm) = 1.30 (t, 3H, CH3, J= 6.9 Hz), 2.48 (s, 3H, CH3), 4.33 (q, 2H, CH2, J= 6.9 Hz), 5.42 (s, 1H),
13
6.21-7.60 (m, 6H, aromatic protons), 7.64 (d, 2H), 8.03 (d, 2H); C-NMR: δ (ppm) = 17.75, 24.36,
54.85, 60.16, 64.52, 115.23, 117.00, 121.23, 126.46, 130.23, 131.77, 132.65, 133.41, 133.85, 134.61,
135.10, 135.26, 139.21, 140.82, 145.01, 169.08, 180.63; MS: m/z (%) = 452 (M++2, 11.3) 451 (M++1,
10.1), 450 (M+, 20.5), 448 (36.2), 323 (55.2), 322 (100.0), 242 (11.3), 212 (52.0), 201 (9.3), 199
(80.8), 154 (16.3), 122 (11.5), 111 (7.9), 105 (18.6), 93 (5.9), 83 (4.8), 77 (20.1), 76 (12.9), 63 (16.1),
60 (20.4); Anal. Calcd. for C24H19ClN2O3S (450.93): C, 63.92; H, 4.25; Cl, 7.86; N, 6.21; S, 7.11%.
Found: C, 63.98; H, 4.01; Cl, 7.65; N, 6.02; S, 7.51.
(5-Methyl-1-nitro-2-phenylindolizin-3-yl)(2-thienyl)methanone (12a): yellow crystals; mp 179-181 oC;
1
yield 75%; IR: ν = 1670 (CO); H-NMR: δ (ppm) = 2.50 (s, 3H, CH3), 6.90-8.25 (m, 6H, aromatic
protons), 7.52 (dd, 1H), 7.68 (d, 2H), 7.79 (dd, 2H); 13C-NMR: δ (ppm) = 17.54, 116.68, 118.92,
120.73, 121.13, 122.63, 125.96, 126.79, 129.37, 130.85, 131.60, 132.35, 132.85, 133.33, 133.93,
134.76, 140.57, 178.15; MS: m/z (%) = 362 (M+, 31.1), 322 (40.0), 280 (26.7), 263 (31.1), 255 (42.2),
236 (60.0), 149 (100.0), 128 (24.4), 113 (22.2), 111 (22.2), 104 (31.1), 92 (4.4), 83 (9.5), 77 (75.6), 62
(26.7), 50 (62.2); Anal. Calcd. for C20H14N2O3S (362.41): C, 66.28; H, 3.89; N, 7.73; S, 8.85%. Found:
C, 66.51; H, 3.62; N, 7.52; S, 8.25.
(1-Benzoyl-5-methyl-2-phenylindolizin-3-yl)(2- thienyl)methanone (12b): pale yellow crystals; mp 210
1
oC; yield 76%; IR: ν = 1670, 1655 (2CO); H-NMR: δ (ppm) = 2.49 (s, 3H, CH3), 6.69-8.21 (m, 6H,
aromatic protons) 7.45 (d, 2H), 7.54 (dd, 1H), 7.69, (dd, 2H), 7.77 (dd, 2H), 7.83 (dd, 1H), 8.09 (d,
2H); 13C-NMR: δ (ppm) = 17.52, 40.73, 114.65, 119.79, 122.64, 125.31, 125.76, 126.17, 126.59,
126.96, 127.32, 129.81, 130.87, 131.13, 131.53, 131.89, 133.95, 135.73, 136.27, 139.31, 140.23,
173.64, 190.56; MS: m/z (%) = 421 (M+, 16.8), 407 (13.0), 288 (26.6), 208 (23.1), 207 (24.3), 199
(15.4), 131 (14.8), 111 (49.1), 105 (85.2), 103 (20.7), 78 (33.1), 77 (100.0), 76 (11.8), 63 (9.5); Anal.
Calcd. for C27H19NO2S (421.52): C, 76.94; H, 4.54; N, 3.32; S, 7.61%. Found: C, 76.95; H, 4.21; N,
3.24; S, 7.63.

Molecules 2008, 13
1075
4,5-Dihydrothiophene-3-carbonitriles 15a,b
A mixture of the picolinium salt 3 (0.59 g, 2 mmol) and the appropriate arylidenecyanothio-
acetamide 14 (2 mmol) were refluxed in absolute ethanol (30 mL) in the presence of triethylamine
(0.15 mL) for 4 hours and then cooled. The reaction mixture was poured onto ice cold water and
neutralized with 10 % hydrochloric acid. The solid product was collected, washed with water, dried
and finally recrystallized from dioxane and ethanol, respectively, to afford the corresponding 4,5-
dihydrothiophene derivatives 15a and b.
2-Amino-4-(4-bromophenyl)-5-(2-thienylcarbonyl)-4,5-dihydrothiophene-3-carbonitrile (15a): yellow
crystals from ethanol; mp 250 oC; yield 70%; IR: ν = 3364, 3212 (NH2), 2215 (C=N), 1720 (CO); 1H-
NMR: δ (ppm) = 3.94 (d, 1H, J = 17 Hz), 4.89 (d, 1H, J = 17 Hz), 7.21 (d, 2H), 7.34-7.94 (m, 3H),
13
7.88 (d, 2H), 8.65 (br. S, 2H, NH2, D2O exchangeable); C-NMR: δ (ppm) = 44.09, 53.08, 68.29,
110.73, 118.15, 130.67, 131.42, 131.78, 132.97, 137.93, 139.13, 141.98, 161.27, 186.49; MS: m/z (%)
= 393 (M++2, 6.4), 392 (M++1, 7.4), 391 (M+, 18.3), 279 (16.5), 111 (44.5), 83 (11.8), 80 (100.0), 64
(70.6); Anal. Calcd. for C16H11BrN2OS2 (391.30): C, 49.11; H, 2.83; Br, 20.42; N, 7.16; S, 16.39%.
Found: C, 49.22; H, 2.54; Br, 20.32; N, 7.22; S, 16.15.
2-Amino-4-(4-methoxyphenyl)-5-(2-thienylcarbonyl)-4,5-dihydrothiophene-3-carbonitrile (15b):
o
yellow crystals from ethanol; mp 170-172 C; yield 60%; IR: ν = 3360, 3192 (NH2), 2215 (C=N),
1723 (CO); 1H-NMR: δ (ppm) = 3.70 (s, 3H, OCH3), 4.02 (d, 1H, J = 17 Hz), 4.96 (d, 1H, J = 17 Hz),
6.65 (br. S, 2H, NH2, D2O exchangeable ), 6.96 (d, 2H), 7.27-8.31 (m, 3H), 7.45 (d, 2H); 13C-NMR: δ
(ppm) = 49.64, 56.90, 57.82, 70.39, 113.58, 116.82, 130.80, 131.35, 131.93, 132.72, 135.89, 144.82,
155.92, 161.59, 184.18; MS: m/z (%) = 343 (M++1, 11.4), 342 (M+, 26.8), 233 (18.6), 124 (16.7), 111
(86.1), 107 (48.5), 83 (100.0), 80 (18.3), 64 (10.2); Anal. Calcd. for C17H14N2O2S2 (342.43): C, 59.63;
H, 4.12; N, 8.18; S, 18.73%. Found: C, 59.58; H, 3.99; N, 8.02; S, 18.51.
General procedure for the synthesis of 2-(thiophene-2-yl)carbonyl-3,5-diaryl-4,6-dicyanoaniline
derivatives 17a-c:
A mixture of compound 3 (0.59 g, 2 mmol) and the appropriate arylidenemalononitrile 16a-c (4
mmol) was refluxed in pyridine (20 mL) for 6 hours, then cooled. The reaction mixture was poured
onto ice cooled water, neutralized with 10% hydrochloric acid. The solid product was collected,
washed with water, dried, and finally recrystallized from a mixture of ethanol and dimethylformamide
(3:1) to afford the corresponding compounds 17a-c.
o
2-(Thiophene-2-yl)carbonyl-3,5-diphenyl-4,6-dicyanoaniline (17a): yellow crystals; mp 224 C; yield
1
70%; IR: ν = 3335, 3104 (NH2), 2197(CN), 1665(CO); H-NMR: δ (ppm) = 6.86-7.80 (m, 3H), 7.45
(dd, 1H), 7.60 (dd, 1H), 7.78 (d, 2H), 7.92 (dd, 2H), 8.00 (d, 2H), 8.10 (dd, 2H), 8.20 (br. s, 2H, NH2,
D2O exchangeable); 13C-NMR: δ (ppm) = 92.08, 96.95, 99.15, 120.96, 125.37, 127.59, 129.20, 129.37,
130.65, 130.57, 131.12, 131.93, 134.82, 135.66, 136.94, 137.96, 139.50, 148.36, 151.49, 152.29,
193.42(CO); MS: m/z (%) = 405 (M+, 18.8), 293 (15.6), 207 (12.6), 180 (18.5), 179 (31.9), 178 (40.2),

Molecules 2008, 13
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136 (20.3), 111 (70.2), 105 (16.8), 104 (32.8), 83 (100), 77 (86.6), 66 (25.2); Anal. Calcd. for
C25H15N3OS (405.48): C, 74.05; H, 3.73; N, 10.36; S, 7.91%. Found: C, 74.11; H, 3.25; N, 10.24; S,
7.63.
o
2-(Thiophene-2-yl)carbonyl-3,5-di-2-furyl -4,6-dicyanoaniline (17b): yellow crystals; mp 280 C;
yield 80%; IR: ν = 3342, 3119 (NH2), 2211 (C=N), 1667 (CO); 1H-NMR: δ (ppm) = 6.70-7.95 (m, 9H,
aromatic protons), 8.20 (br. s, 2H, NH2, D2O exchangeable); MS m/z (%) 385 (M+, 22.6), 301 (16.6),
111 (100), 83 (20.5), 67 (20.5), 64 (15.1); Anal. Calcd. for C21H11N3O3S (385.40): C, 65.45; H, 2.88;
N, 10.90; S, 8.32%. Found: C, 65.38; H, 2.65; N, 10.88; S, 8.30.
o
2-(Thiophene-2-yl)carbonyl-3,5-di-2-thienyl-4,6-dicyanoaniline (17c): yellow crystals; mp 276 C;
yield 65%; IR: ν = 3326, 3205 (NH2), 2210 (C=N), 1658 (CO); 1H-NMR: δ (ppm) = 7.00-7.86 (m, 9H,
aromatic protons), 8.00 (br. s, 2H, NH2, D2O exchangeable); MS: m/z (%) = 417 (M+, 11.3), 304
(15.6), 253 (9), 236 (8), 111 (35), 94 (46), 83 (100.0), 66 (10.5), 54 (15.1); Anal. Calcd. for
C21H11N3OS3 (417.53): C, 60.41; H, 2.66; N, 10.06; S, 23.04%. Found: C, 60.38; H, 2.65; N, 10.88; S,
23.30.
2-(2-Thienyl)indolizine (18)
To a solution of compound 3 (0.59 g, 2 mmol), in benzene (30 mL), triethylamine (0.15 mL, 1.5
mmol) was added and the mixture was refluxed for 6 hours, then cooled to room temperature. The
solid salts were removed by filtration, and the filtrate was evaporated under vacuum. The residue was
treated with methanol and the solid precipitate was filtered off, washed with methanol, and dried.
o
Recrystallization from ethanol afforded 18 as yellow crystals; mp 170 C; yield 45%; IR: ν = 3098
1
(CH, aromatic), 1626 (C=C stretching); H-NMR: δ (ppm) = 6.55-8.21 (m, 4H), 6.73 (s, 1H), 7.07-
7.41 (m, 3H), 7.83 (s, 1H); 13C-NMR: δ (ppm) = 99.82, 111.73, 114.82, 115.51, 116.25, 124.15,
125.87, 127.18, 127.91, 129.17, 137.20, 141.64; MS: m/z (%) = 200 (M++1, 15.3), 199 (M+, 100.0),
198 (20.8), 154 (32.2), 141 (18.8), 113 (7.5), 100 (12.3), 93 (9.9), 86 (14.4), 83 (2.5), 82 (9.9), 77
(11.6), 69 (17.5), 64 (10.7), 50 (29.2); Anal. Calcd. for C12H9NS (199.28): C, 72.33; H, 4.55; N, 7.03;
S, 16.09%. Found: C, 72.21; H, 4.36; N, 7.22; S, 16.11.
Biological activity
The antibacterial and antifungal activity assays were carried out in the Microbiology Division of
Microanalytical Center of Cairo University using the diffusion plate method [22-24]. A bottomless
cylinder containing a measured quantity (1mL, mg/mL) of the sample is placed on a plate (9 cm
diameter) containing a solid bacterial medium (nutrient agar broth) or fungal medium which has been
heavily seeded with a spore suspension of the test organism. After incubation (24 hours for bacteria
and 5 days for fungi), the diameter of the clear zone of inhibition surrounding the sample is taken as
measure of the inhibitory power of the sample against the particular test organism.

Molecules 2008, 13
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Sample availability: Available from the author.
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