Synthesis and antibacterial activities of new metronidazole and Imidazole Derivatives

Article abstract of DOI:10.3390/molecules14072431

New imidazole ring derivatives comprising 1,3-oxazoline, Schiff's bases, thiadiazole, oxadiazole and 1,2,4-triazole moieties are reported. 3-Aminobiimidazol-4-one compounds 7a-c were synthesized by the reaction of compounds 6a-c with hydrazine hydrate. Bi

Full text of DOI:10.3390/molecules14072431

Molecules 2009, 14, 2431-2446; doi:10.3390/molecules14072431
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Synthesis and Antibacterial Activities of New Metronidazole
and Imidazole Derivatives
Abdul Jabar Kh. Atia
Department of Chemistry, College of Sciences, The University of Mustansiriayah, Iraq;
E-mail: chemabdu@yahoo.com
Received: 17 May 2009; in revised form: 12 June 2009 / Accepted: 6 July 2009 /
Published: 8 July 2009
Abstract: New imidazole ring derivatives comprising 1,3-oxazoline, Schiff's bases,
thiadiazole, oxadiazole and 1,2,4-triazole moieties are reported. 3-Aminobiimidazol-4-one
compounds 7a-c were synthesized by the reaction of compounds 6a-c with hydrazine
hydrate. Biimidazole esters 9a-c were converted into biimidazole hydrazide esters 10a-c.
Compounds 7a-c and 10a-c were converted into a variety of derivatives.
Keywords: metronidazole; biimidazole; imidazole; 1,3,4-oxadiazole; 1,2,4-triazole;
1,3,4-thiadiazole
1. Introduction
Metronidazole (MTZ, 1) is a synthetic compound used in the treatment of infections caused by
Gram negative anaerobic bacteria like Helicobacter pylori and protozoa such as Giardia, Lamblia, and
Entomoeba histolytica, [1] Imidazole and its derivatives are of great significance due to their important
roles in biological systems, particularly in enzymes, as proton donors and/or acceptors, coordination
system ligands and the base of charge–transfer processes. Unlike pyrrole (a proton donor) and pyridine
(a proton acceptor), 1H-imidazole has both proton donor and acceptor properties [2,3]. Imidazole
functionalities have been used for complex reactions with different molecular components such as
carboxylic acids to obtain liquid crystalline assemblies [4]. The imidazole nucleus appears in a number
of naturally occurring products like the amino acids histidine and purines, which comprise many of the
most important bases in nucleic acids. Imidazole derivatives possess a broad spectrum of
pharmacological activities such as anticonvulsant [5], anti-Parkinson [6] and mono-aminooxidase
(MAO) inhibitory [7] activity. Oxadiazole, triazole and thiadiazole chemistry has been developed

Molecules 2009, 14
2432
extensively and are still being developed presently. There are a number of drugs used clinically [8]
which comprise oxadiazole, triazole and thiadiazole moieties in association with various heterocyclic
rings. In view of these facts, a project was undertaken to synthesize a new series of imidazoles
containing oxadiazole, triazole, thiadiazole and Schiff's bases and to evaluate the new compounds for
their biological activity
2. Results and Discussion
The designated compounds were synthesized according to Schemes 1 and 2. Reaction of 2-(5-
methyl-2-nitro-1H-imidazole-1-yl) ethanol (metronidazole, 1) with thionyl chloride afforded 1-(2-
chloroethyl)-5-methyl-2-nitro-1H-imidazole (2) [4].
Scheme 1. The synthesis of compounds 1 - 9a-c.
N
N
_ 2H2O
+
(CH2NH2)2
2AcOH
(CH2NHOAc)2
H3C
H3C
N
H
N
H
HNO3 H2SO4
N
N
N
N
KMnO4
HOCH2CH2Cl
H3C
SOCl2
HOOC
3
NO2
H3C
NO2
NO2
H3C
NO2
Na2CO3
N
N
N
H
N
1
2
CH2CH2OH
CH2CH2Cl
CH2CH2Cl
SOCl2
Metronidazole
N
ClOC
NO2
Ar
CH
NH2CH2COOH
benzene
N
Aromatic aldehydes
AC2O\ ACOH
4
N
N
N
CH2CH2Cl
NO2
HOOC-H2C-HN-OC
5
NO2
CH2CH2Cl
N2H4
O
N
O
N
6 a - c
CH2CH2Cl
Ar
CH
Ar
HC
N
N
N
N
Aromatic aldehydes
NO2
CH2CH2Cl
O
NO2
CH2CH2Cl
O
N
N
N
N
N
8 a - i
7 a - c
NH2
-
CH
Ar
Ethyl bromoacetate
EtONa
Ar
HC
N
N
Ar = 4-NO2-C6H4 , 4-Br-C6H4 , 4Cl--C6H4
Ar` = 4-CH3--C6H4 , 3-NO2-CH4 , 2-NO2--C6H4
NO2
O
N
N
CH2CH2Cl
EtOOCH2C NH
9 a - c
The IR spectrum of the product collected and recrystallized from ethanol indicated the absence of
absorption bands due to OH and the presence of a C-Cl absorption band at (768 cm-1). 1-(2-Chloro-

Molecules 2009, 14
2433
ethyl)-2-nitro-1H-imidazol-5-carboxylic acid (3) [9] which was readily prepared via oxidation of the
CH3 group of compound 2, was converted into acid chloride 4 through reaction with thionyl chloride.
The structures of compounds 3 and 4 were confirmed by 1H-NMR and IR spectral data and elemental
analysis. In the IR spectrum compound 3 the presence of an OH absorption at 3,270- 2,650 cm-1
1
besides the C=O absorption at 1,715 cm-1 was observed. The H-NMR spectrum showed a triplet at
3.51-3.88 ppm integrating for protons of the CH2-Cl and a triplet at 2.95-3.21 ppm integrating for two
protons of the N-CH2. The IR spectrum of compound 4 showed disappearance of the absorption band
due to OH and an increase in the frequency of carbonyl moiety. Reaction of compound 4 with an
amino acid (glycine) gave ({[1-(2-chloroethyl)-2-nitro-1H-imidazole-5-yl] carbonyl}amino) acetic
acid (5) [10], while on the other hand, oxidative cyclization of compound 5 with aromatic aldehydes
(Scheme 1) afforded 2-[1-(2-chloroethyl)-2-nitro-1H-imidazole-5-yl]-4-arylidene1,3-oxazol-5(4H)-
ones 6a-c [11]. The IR spectrum of compound 5 showed two sharp absorption bands, the first appears
at 1,720 cm-1 and is attributed to carbonyl function of the carboxylic acid and the other, observed at
1,690 cm-1, was assigned to a C=O stretching frequency corresponding to the amide carbonyl. In the
1H-NMR spectrum, the proton signals due to (CH2-NH) resonated at 4.42-4.67 ppm, integrating for
a
b
two protons, while the proton signals due to ethyl group (N-CH2 -CH2 -Cl) were recorded between
2.82-2.93 ppm integrating for two protons (a) and at 3.40-3.64 ppm integrating for two protons (b).
The structures of compounds 6a-c were indicated by the absence of the characteristic O—H stretching
in addition to the absorption bands for the NH. The 1H-NMR spectra of compounds 6a-c showed new
signals observed at 6.55-6.81 ppm integrating for two protons and at 7.31-7.75 ppm integrating for two
protons assigned to aryl groups. The key intermediate 3-amino-3'-(2-chloroethyl)-5-arylidene-2'-nitro-
3,5-dihydro-3'H,4H-2,4'-biimidazol-4-ones 7a-c [12] were prepared from the reaction of hydrazine
hydrate with compounds 6a-c. The structures of all compounds 7a-c were proven based on the melting
point (m.p), thin layer chromatography (TLC) and spectral data. The spectra of compounds 7a-c
exhibited a NH2 stretching vibration at 3,360-3,210 cm-1 and C=O stretching vibrations at
1,660-1,695 cm-1. Reaction of compounds 7a-c with aromatic aldehydes produced new Schiff's bases
8a-c in high yield (Scheme1). The Schiff's bases 8a-i display in their IR carbonyl and isomethine
absorptions near 1,690-1,643 cm-1 and 1640-1627 cm-1, respectively, in addition to absence of
NH2stretching vibrations. Alkylation of compounds 7a-c with ethyl bromoacetate give ethyl {[3'-(2-
chloroethyl)-4-arylidene-2'-nitro-5-oxo-4, 5-dihydro-1H, 3'H-2, 4'-biimidazol-1-yl] amino} acetates
9a-c [13]. The formation of compounds 9a-c was confirmed by the presence of a sharp absorption
near 1,730-1,715 cm-1 for the ester C=O and at 1,250-1,300 cm-1 due to C—O stretching. In the
c
d
1H NMR spectra, the proton signals due to ethyl group of ester O-CH2 -CH3 were recorded between
1.35-1.78 ppm, integrating for three protons (d) and 3.31-3.78 ppm integrating for two protons (c). The
treatment of compounds 9a-c with hydrazine hydrate, gave thiosemicarbazide compounds 10a-c [6]
and compounds 11a-c [6], respectively. The spectral data of compounds 10a-c and 11a-c are given in
the Experimental section. Acid hydrazides are useful intermediates leading to the formation of some
heterocyclic ring such as 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles. The 3'-(2-
chloroethyl)-5-arylidene-3-{[5-mercapto-1,3,4-oxadiazol-2-yl-methyl]amino}-2'-nitro-3,5-dihydro-
3'H,4H,2,4'-biimidazol-4-one compounds 12a-c [13] were synthesized from the reaction of compounds
10a-c with carbon disulfide in the presence of potassium hydroxide (Scheme 2).

Molecules 2009, 14
2434
Scheme 2. The synthesis of compounds 10(a-c) – 15(a-c).
Ar
CH
Ar
CH
N
N2H4
N
N
N
O2N
ClH2CH2C
10 a - c
CS2\ KOH
O2N
O
N
N
O
N
N
ClH2CH2C
NH
HN
CH2COOEt
CH2-CONHNH2
9 a - c
CS2\ KOH
N2H4
Thiosemicarbazide
H2NCSNHNH2
Ar
Ar
CH
CH
Ar
CH
N
N
N
N
O2N
N
O2N
N
O
N
N
O
N
O2N
ClH2CH2C
11 a - c
N
NH
ClH2CH2C
NH
N
N
ClH2CH2C
O
N
N
N
N
H2C
NH
SH
H2C
SH
CH2CONHNHCSNH2
N
O
12 a - c
13 a - c
NH2
H2SO4
NaOH
Ar
CH
N
N
O2N
Ar
CH
O
N
N
ClH2CH2C
NH
N
N
N
N
H2C
O2N
NH2
14 a - c
O
N
S
N
ClH2CH2C
N
N
NH
H2C
15 a - c
SH
N
H
The IR spectra of compounds 12a-c displayed the SH absorption at 2,470-2,580 cm-1 in addition to
the C=S absorption at 1,210-1,280 cm-1. The NH and SH protons derived from the tautomeric
equilibrium resonated between 12.55-13.19 ppm as a broad singlet integrating for one proton.
1
Moreover, NHNH2 signals disappeared from the H-NMR and IR spectra. The condensation of the
same intermediates 10a-c with carbon disulphide in basic media produced a potassium salt, that
without isolation and purification was treated with hydrazine hydrate to give 3-{[(4-amino-5-
mercapto-4H-1,2,4-triazol-3-yl)methyl]amino}-3'-(2-chloroethyl)-5-arylidene-2'-nitro-3',5-dihydro-
3'H,4H-2,4'-biimidazol-4-ones 13a-c [14]. In contrast to those of 12a-c, the IR spectra of compounds
13a-c contained additional NH2 absorption bands. Moreover, proton signals due to NH2 group of
compounds 13a-c resonated at 6.42-6.53 ppm, integrating for two protons. Oxidative cyclization of
compounds 11a-c with aqueous sodium hydroxide (Scheme 2) afforded 3'-(2-chloroethyl)-5-arylidene-
2'-nitro-3-[(4H-1,2,4-triazol-3-yl-methyl)amino]-3,5-dihydro3'H,4H-2,4'-biimidazol-4-ones 14a-c [7],
while the treatment of the same compounds 11a-c with conc. H2SO4 afforded 3-{[(5-amino-1,3,4-
thiadiazol-2-yl)
methyl]amino}-3'-(2-chloroethyl)-5-arylidene-2'-nitro-3,5-dihydro-3'H,4H-2,4'-
biimidazol-4-ones 15a-c [14].

Molecules 2009, 14
2435
The formation of the 1,2,4-triazole derivatives 14a-c as confirmed by the presence of weak
absorptions near 2,570-2,630 cm-1 for SH and 1,230-1,300 cm-1 due to C=S. The structures of
1
compounds 15a-c were confirmed by H-NMR, IR and elemental analysis. The data are shown the
Experimental section.
2.1. Antibacterial activity
The antibacterial activity of the imidazole derivatives was tested by the agar disc-diffusion method
against Staph. aureus, E. coli and Proteus mirabilis bacteria. Dimethylsulphoxide (DMSO) was used
as solvent control, and the concentration of tested compounds was 10-3 M. The results of these studies
are summarized in Table 1. It could be observed that all the tested compounds were active toward
Proteus mirabilis, except compound 8b, and all the tested compounds were active toward E. Coli,
except for compounds 7a and 8d and all the compounds were active toward Staph. aureus except 8b,
8f, 8i, 13a, 13b and 14c. On the other hand, compounds 15a-c showed high inhibition toward all kinds
of bacteria tested. In addition compounds 6a, 8c and 8h, compounds 7c, 12b, 13c and 14a and
compounds 7b, 12c, 13a-c, 14b and 14c showed high inhibition toward Staph. aureus, E. coli. and
Proteus mirabilis, respectively.
Table 1. Antibacterial Activity of New Compounds.
Compound No.
Staph. aureus
E. coli
-
Proteus mirabilis
DMSO
6a
-
+++
+
-
++
++
+
++
++
+
6b
6c
++
++
++
+
7a
-
++
+++
++
+
7b
7c
++
+++
++
+
8a
++
-
8b
8c
-
+++
++
++
-
++
-
++
++
+
8d
8e
+
8f
++
+
++
+
8g
++
+++
-
8h
8i
++
++
+
++
++
+
9a
+
9b
9c
+
+
++
+
++
++
+
10a
++
+

Molecules 2009, 14
2436
Table 1. Cont.
10b
10c
11a
11b
11c
12a
12b
12c
13a
13b
13c
14a
14b
14c
15a
15b
15c
++
++
+
++
+
+
+
+
++
++
++
+
+
++
+
++
++
+++
++
++
+
+
+
+
++
-
+++
+++
+++
+++
++
-
+
+++
+++
++
+
++
++
-
+++
+++
+++
+++
+++
+++
+++
+++
+++
+++
++
Zone diameter of growth inhibition: - = no inhibition, + = (3 – 6) mm, ++ = (7 –
10) mm and +++ = (11 – 15) mm. Conc. 10 -3 M.
3. Experimental
3.1. General
Melting points were determined in open capillary tubes on a Gallenkamp melting point apparatus
and are uncorrected. The IR spectra were recorded on KBr disks, using a Perkin-Elmer 1600 series
FTIR spectrometer. UV spectra were recorded on a Hitachi 2000 spectrophotometer. 1H-NMR spectra
were recorded in DMSO-d6 on a Varian-Mercury 200 MHz Spectrometer. Combustion analysis was
performed on a Carlo Erba 1106 elemental analyzer. Compound 1 was synthesized by a published
method [15].
3.2. Synthesis of 1-(2-chloroethyl) -5-methyl-2-nitro-1H-imidazole (2)
Thionyl chloride (1.18 g , 0.01 mole) was added to a solution of compound 1 (1.71 g, 0.01 mole) in
dry benzene (20 mL), then the reaction mixture was refluxed for 7 hrs. After evaporation, the product
was collected and crystallized from ethanol-water. Yield: 90%; m.p. 85-87 °C; IR (ν, cm-1): 2,970-
2,855 (C-Haliph.), 1,605 (C=N), 1,530-1,470 (NO2), 768 (C-Cl); 1H-NMR: δ (ppm) 1.75 (s, CH3), 2.81-
3.10 (t, N-CH2), 3.71-4.10 (t, CH2-Cl), 8.48 (s, 1H, imidazole); Anal. % calc./found for C6H8N3O2Cl
(m.w. 189.5) C, 38.01/39.67; H, 4.25/4.34, N 22.16/23.34.

Molecules 2009, 14
2437
3.3. Synthesis 1-(2-chloroethyl)-2-nitro-1H-imidazol-5-carboxylic acid (3)
Compound 2 (1.89 g, 0.01 mole) was added to a solution of sodium bicarbonate (1.06 g, 0.01 mole)
and potassium permanganate (1.57 g, 0.01 mole) in water (20 mL), then the reaction mixture was
refluxed for 15 hrs. The reaction mixture was cooled and acidified with conc. HCl and the product was
collected and recrystallized from ethanol. Yield: 55%; m.p. 181-183°C; IR (ν, cm-1): 3,270-2,650
(OHacid), 2,985-2,890 (C-Haliph.), 1,715 (C=Oacid), 1,615 (C=N), 1,530-1,370 (NO2); 1H-NMR: δ (ppm)
2.95-3.11 (t, N-CH2), 3.51-3.88 (t, CH2-Cl), 12.32 (s, acid OH), 8.82 (s, 1H, imidazole); Anal. %
calc./found for C6H6N3O4Cl (m.w. 219.5): C, 32.82/33.65; H, 2.75/3.32; N, 19.14/18.09.
3.4. Synthesis of 1-(2-chloroethyl)-2-nitro-1H-imidazole-5-carbonyl chloride (4)
This compound was synthesized following the same procedure used in synthesis of compound 2,
without purification. Yield: 83%; m.p. 127-129°C; IR (ν, cm-1): 2,988-2,850 (C-Haliph.), 1,765 (C=Oacid
chloride), 1620 (C=N), 1570-1390 (NO2); 1H-NMR: δ (ppm) 2.73-2.91 (t, N-CH2), 3.75-3.95 (t, CH2-Cl)
8.75 (s, 1H, imidazole); Anal. % calc./found for C6H5N3O3Cl2 (m.w. 238): C, 30.28/29.69; H,
2.12/2.79; N, 17.65/18.07.
3.5. Synthesis of ({[1-(2-chloroethyl)-2-nitro-1H-imidazole-5-yl] carbonyl}amino) acetic acid (5)
Compound 4 (2.38 g, 0.01 mole) was added to a stirring solution of glycine (0.75 g, 0.01 mole) and
sodium hydroxide (10 mL, 10% solution). Then, the reaction mixture was shaken vigorously for 1 hr,
and a few grams of crushed ice were added with stirring. After that, the solution was acidified with
conc. HCl and the product was collected and recrystallized from ethanol. Yield: 80%; m.p. 165-167°C;
IR (ν, cm-1): 3,220 (NH), 3,150 (OHacid), 2,985-2,870 (C-Haliph.), 1,720 (C=Oacid), 1,690 (C=Oamide),
1
1,510-1,370 (NO2); H-NMR: δ (ppm) 2.82-2.93 (t, N-CH2), 3.40-3.72 (t, CH2-Cl), 4.42-4.66 (s, CO-
CH2-NH), 8.72 (s, 1H, imidazole), 10.57 (s, NHamide), 12.20 (s, OHacid); Anal. % calc./found for
C8H9N4O5Cl (m.w. 276.5): C, 34.73/35.54; H, 3.26/3.55; N, 20.25/21.28.
3.6. Synthesis of 2-[1-(2-chloroethyl)-2-nitro-1H-imidazole-5-yl]-4-arylidene1,3-oxazol-5(4H)-ones
6a-c
Aromatic aldehyde (0.01 mole) was added to a stirring mixture of compound 5 (2.76 g, 0.01 mole)
acetic acid (5 mL) and acetic anhydride (20 mL). The temperature of reaction was increased to 70 °C
for 10 min., then the mixture was poured into crushed ice and stirred for 30 min. the product was
collected and recrystallized from ethanol to afforded the desired compound.
2-[1-(2-Chloroethyl)-2-nitro-1H-imidazole-5-yl]-4-(4-nitrophenyl)1,3-oxazol-5(4H)-one (6a): Yield:
53%; m.p. 201-204 °C; IR (ν, cm-1): 3,050 (C-Har.), 2,983-2,868 (C-Haliph.), 1,710 (C=Ooxazole), 1,620
1
(C=Calkene), 1,280 (C-O); H-NMR: δ (ppm) 2.50-2.71 (t, N-CH2), 3.11 (s, C=CH-), 3.42-363 (t, CH2-
Cl), 6.65-6.81 (d, 2H, ArH), 7.43-775 (d, 2H, ArH), 8.72 (s, 1H, imidazole); Anal. % calc./found for
C15H10N5O6Cl (m.w. 389.5): C, 45.99/45.08; H, 2.57/3.11; N, 17.88/18.79.

Molecules 2009, 14
2438
2-[1-(2-Chloroethyl)-2-nitro-1H-imidazole-5-yl]-4-(4-bromophenyl)1,3-oxazol-5(4H)-one
(6b):
Yield: 57%; m.p. 230-232 °C; IR (ν, cm-1): 3,080 (C-Har.), 2,990-2,890 (C-Haliph.), 1705 (C=Ooxazole),
1,610 (C=Calkene), 1,280 (C-O); 1H-NMR: δ (ppm) 2.33-2.56 (t, N-CH2), 3.21 (s, C=CH-), 3.59-3.72
(t, CH2-Cl), 6.55-6.71 (d, 2H, ArH), 7.31-7.59 (d, 2H, ArH), 8.85 (s, 1H, imidazole); Anal. %
calc./found for C15H10N4O4BrCl (m.w. 425.5): C, 42.33/43.64; H, 2.37/3.00; N, 13.16/14.23.
2-[1-(2-Chloroethyl)-2-nitro-1H-imidazole-5-yl]-4-(4-chlorophenyl1,3-oxazol-5(4H)-ones (6c): Yield:
51%; m.p. 236-239 °C; IR (ν, cm-1): 3,050 (C-Har.), 2,896-2,810 (C-Haliph.), 1,725 (C=Ooxazole), 1,610
(C=Calkene), 1,300 (C-O); 1H-NMR: δ (ppm) 2.11-2.31 (t, N-CH2), 2.92 (s, C=CH-), 3.40-3.61 (t, CH2-
Cl), 6.75-6.85 (d, 2H, ArH), 7.39-7.50 (d, 2H, ArH), 8.63 (s, 1H, imidazole); Anal. % calc./found for
C15H10N4O2Cl2 (m.w. 381.5): C, 47.27/47.44; H, 2.64/2.89; N, 14.70/15.06.
3.7. Synthesis of 3-amino-3'-(2-chloroethyl)-5-arylidene-2'-nitro-3,5-dihydro-3'H,4H-2,4'biimidazol-4-
ones 7a-c
Hydrazine hydrate (99%, 10 mL) was added to a mixture of compound 6 (0.01 mole) in dry
pyridine (5 mL). The reaction mixture was refluxed for 20 hrs. Then, the mixture was allowed to cool
to room temperature and pyridine was removed. The product was recrystallized from ethanol to afford
the desired compound.
3-Amino-3'-(2-chloroethyl)-5-(4-nitrophenyl)-2'-nitro-3,5-dihydro-3'H,4H-2,4'biimidazol-4-one (7a):
Yield: 47%; m.p. 198-201°C; IR (ν, cm-1): 3,360-3,290 (NH2), 3,080 (C-Har.), 2,950-2,890 (C-Haliph.),
1,695 (C=O) 1,620 (C=Calkene); 1H-NMR: δ (ppm) 2.37-2.49 ( t, N-CH2), 3.13 (s, C=CH-), 3.41-3.53 (t,
CH2-Cl), 6.40 (s, NH2), 6.73-6.91 (d, 2H, ArH), 7.37-7.72 (d, 2H, ArH), 8.49 (s, 1H, imidazole); Anal.
% calc./found for C15H12N7O5Cl (m.w. 405.5): C, 44.40/46.53; H, 2.98/3.67; N, 24.16/24.68.
3-Amino-3'-(2-chloroethyl)-5-(4-bromophenyl)-2'-nitro-3,5-dihydro-3'H,4H-2,4'biimidazol-4-one (7b):
Yield: 35%; m.p. 256-259°C; IR (ν, cm-1): 3,310-3,260 (NH2), 3,060 (C-Har.), 2,975-2,859 (C-Haliph.),
1
1,670 (C=O), 1,615 (C=Calkene); H-NMR: δ (ppm) 2.25-2.43 (t, N-CH2), 3.35 (s, C=CH-), 3.49-3.61
(t, CH2-Cl), 6.21 (s, NH2), 6.63-6.89 (d, 2H, ArH), 7.22-7.45 (d, 2H, ArH), 8.80 (s, 1H, imidazole);
Anal. % calc./found for C15H12N6O3BrCl (m.w. 439.5): C, 40.98/41.79; H, 2.75/3.43; N, 19.12/20.21.
3-Amino-3'-(2-chloroethyl)-5-(4-chlorophenyl)-2'-nitro-3,5-dihydro-3'H,4H-2,4'biimidazol-4-one (7c):
Yield: 38%; m.p. 283-285°C; IR (ν, cm-1): 3,345-3,250 (NH2), 3,080 (C-Har.), 2,990-2,890 (C-Haliph.),
1,660 (C=O), 1,610 (C=Calkene); 1H-NMR: δ (ppm) 2.19-2.31 (t, N-CH2), 3.31 (s, C=CH-), 3.52-3.73
(t, CH2-Cl), 6.11 (s, NH2), 6.61-6.85 (d, 2H, ArH), 7.42-7.69 (d, 2H, ArH), 8.74 (s, 1H, imidazole);
Anal. % calc./found for C15H12N6O3Cl2 (m.w. 395): C, 45.59/45.03; H, 3.06/3.86; N, 21.27/22.76.

Molecules 2009, 14
2439
́'-(2-chloroethyl)-5-arylidene-3-(arylideneamino)-2'-nitro-3,5-dihydro-3'H,4H-
3.8. Synthesis of (5Z)-3
2,4'-biimidazol-4-ones 8a–i
The corresponding aryl aldehyde (0.01 mole) was added to a stirred solution of compound 7 (0.01
mole) in absolute ethanol (20 mL) and the mixture was refluxed for 2 hrs. After cooling, the mixture
was filtered and the solid recrystallized from ethanol to afford the desired compound.
(5Z)-3́'-(2-Chloroethyl)-5-(4-nitrophenyl)-3-({4'-methylphenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8a): Yield: 70%; m.p. 260-263°C; IR: (ν, cm-1) 3,080 (C-Har), 2,970-2,880
(C-Haliph.), 1,685 (C=O), 1,640 (C=N), 1,610 (C=Calkene); 1H-NMR: δ (ppm) 1.59 (s, CH3), 2.31-2.47 (t,
N-CH2), 3.25 (s, C=CH-), 3.49-3.65 (t, CH2-Cl) 6.30-6.82 (d, 4H, ArH), 7.33-7.65 (d, 4H, ArH), 8.21
(s, N=CH-), 8.81 (s, 1H, imidazole); Anal. % calc. for C23H18N7O5Cl (m.w. 507.5): C, 54.39/55.43; H,
3.57/4.98; N, 19.30/20.20.
(5Z)-3́'-(2-Chloroethyl)-5-(4-nitrophenyl)-3-({3'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-2,4'-
biimidazol-4-one (8b): Yield: 78%; m.p. 267-269°C; IR: (ν, m-1) 3,060 (C-Har.), 2,985-2,880
1
(C-Haliph.), 1,690 (C=O), 1,633 (C=N), 1,612 (C=Calkene); H-NMR: δ (ppm) 2.22-2.49 (t, N=CH2),
3.19 (s, C=CH-), 3.40-3.57(t, CH2-Cl), 6.48-6.80 (d, 4H, ArH), 7.29-7.72 (d, 4H, ArH), 8.51
(s, N=CH-), 8.88 (s, 1H, imidazole); Anal. % calc./found for C22H15N8O7Cl (m.w. 538.5): C,
49.04/51.09; H, 2.81/3.29; N, 20.79/21.39.
(5Z)-3́'-(2-Chloroethyl)-5-(4-nitrophenyl)-3-({2'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-2,4'-
biimidazol-4-one (8c): Yield: 83%; m.p. 294-295°C; IR: (ν, cm-1) 3,080 (C-Har.), 2,990-2,865
1
(C-Haliph.), 1,665 (C=O), 1,628 (C=N), 1,615 (C=Calkene); H-NMR: δ (ppm) 2.38-2.46 (t, N=CH2),
3.21 (s, C=CH-), 3.42-3.60 (t, CH2-Cl), 6.38-6.81 (d, 4H, ArH), 7.22-7.82 (d, 4H, ArH), 8.31 (s,
N=CH-), 8.92 (s, 1H, imidazole); Anal. % calc./found for C22H15N8O7Cl (m.w. 538.5): C, 49.04/50.23;
H, 2.81/3.65; N, 20.79/20.87.
(5Z)-3́'-(2-Chloroethyl)-5-(4-bromophenyl)-3-({4'-methylphenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8d): Yield: 67%; m.p. 274-277°C; IR (ν, cm-1) 3,030 (C-Har.), 2,983-2,870
1
(C-Haliph.), 1,677 (C=O), 1,632 (C=N), 1,608 (C=Calkene); H-NMR: δ (ppm) 1.67 (s, CH3), 2,32-2.52
(t, N-CH2), 3.35 (s, C=CH-), 3.53-3.79 (t, CH2-Cl), 6.22-6.75 (d, 4H, ArH), 7.31-7.73 (d, 4H, ArH),
8.18 (s, N=CH-), 8.79 (s, 1H, imidazole); Anal. % calc./found for C23H18N6O3BrCl (m.w. 541.5): C,
50.99/51.45; H, 3.35/4.02; N, 15.51/16.19.
(5Z)-3́'-(2-Chloroethyl)-5-(4-bromophenyl)-3-({3'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8e): Yield: 75%; m.p. 300 °C (dec.); IR: (ν, cm-1) 3,050 (C-Har.), 2,990-2,895
(C-HalIph.), 1,685 (C=O), 1,640 (C=N), 1,612 (C=Calkene); 1H-NMR: δ (ppm) 2.28-2.47 (t, N-CH2), 3.18
(s, C=CH-), 3.42-3.69 (t, CH2-Cl), 6.37-6.82 (d, 4H, ArH), 7.45-7.81 (d, 4H, ArH), 8.33 (s, N=CH-),
8.81 (s, 1H, imidazole); Anal. % calc./found for C22H15N7O5BrCl (m.w. 572.5): C, 46.13/46.86; H,
2.64/3.75; N, 17.12/18.58.

Molecules 2009, 14
(5Z)-3'-(2-Chloroethyl)-5-(4-bromophenyl)-3-({2'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2440
́
2,4'-biimidazol-4-one (8f): Yield: 71%; m.p. 275-278°C; IR: (ν, cm-1) 3,060 (C-Har.), 2,986-2,795
(C-Haliph.), 1,660 (C=O), 1,627 (C=N), 1,607 (C=Calkene); 1H-NMR: δ (ppm) 2.33-252 (t, N-CH2), 3.17
(s, C=CH-), 3.42-3.71 (t, CH2-Cl), 6.62-6.92 (d, 4H, ArH), 7.32-7.61 (d, 4H, ArH), 8.25 (s, N=CH-),
8.69 (s, 1H, imidazole); Anal. % calc./found for C22H15N7O5BrCl (m.w. 572.5): C, 46.13/44.68; H,
2.64/2.07; N, 17.12/16.65.
(5Z)-3́'-(2-Chloroethyl)-5-(4-chlorophenyl)-3-({4'-methylphenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8g): Yield: 68%; m.p. 291-293°C; IR: (ν, cm-1) 3,055 (C-Har.), 2,978-2,865
1
(C-Haliph.), 1,655 (C=O), 1,631 (C=N), 1,610 (C=Calkene); H-NMR: δ (ppm) 1.34 (s, CH3), 2.31-2.49
(N=CH2), 3.21 (s, C=CH-), 3.45-3.83 (t, CH2-Cl), 6.58-6.83 (d, 4H, ArH), 7.35-7.85 (d, 4H, ArH),
8.29 (s, N=CH-), 8.67 (s, 1H, imidazole); Anal. % calc./found for C23H18N6O3Cl2 (m.w. 497): C,
55.55/55.79; H, 3.65/3.90; N, 16.90/16.84.
(5Z)-3́'-(2-Chloroethyl)-5-(4-chlorophenyl)-3-({3'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8h): Yield: 70%; m.p. 250-253°C; IR: (ν, cm-1) 3,063 (C-Har.), 2,990-2,895
(C-Haliph.), 1,643 (C=O), 1,633 (C=N), 1,617 (C=Calkene); 1H-NMR: δ (ppm) 2.36-256 (t, N-CH2), 3.37
(s, C=CH-), 3.47-3.88 (t, CH2-Cl), 6.32-678 (d, 4H ArH),7.33-780 (d, 4H, ArH), 8.23 (s, N=CH-),
8.58 (s, 1H, imidazole); Anal. % calc./found for C22H15N7O3Cl2 (m.w. 528): C, 50.02/52.07; H,
2.86/3.83; N, 18.56/19.78.
(5Z)-3́'-(2-Chloroethyl)-5-(4-chlorophenyl)-3-({2'-nitrophenyl}amino)-2'-nitro-3,5-dihydro-3'H,4H-
2,4'-biimidazol-4-one (8i): Yield: 86%; m.p. 303 °C (dec.); IR: (ν, cm-1) 3,057 (C-Har.), 2,977-2,863
(C-Haliph.), 1,650 (C=O), 1,629 (C=N), 1,620 (C=Calkene); 1H-NMR: δ (ppm) 2.39-265 (t, N-CH2), 3.40
(s, C=CH-), 3.59-3.96 (t, CH2-Cl), 6.39-6.83 (d, 4H, ArH), 7.32-7.85 (d, 4H ArH), 8.27 (s, N=CH-),
8.89 (s, 1H, imidazole); Anal. % calc./found for C22H15N7O3Cl2 (m.w. 528): C, 50.02/51.98; H,
2.86/3.08; N, 18.56/19.21.
3.9. Synthesis of ethyl {[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-
biimidazol-1-yl]amino}acetates 9a-c
The corresponding compound 7 (0.01 mole) was refluxed with an equivalent amount of sodium in
absolute ethanol for 2 hrs. Then, ethyl bromoacetate (1.81 g, 0.01 mole) was added and refluxed for an
additional 5 hrs. After evaporating the solvent under reduced pressure, a solid appeared that was
recrystallized from ethanol to afford the desired compound.
Ethyl {[3'-(2-chloroethyl)-4-(4-nitrophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetate (9a): Yield: 56%; m.p. 245-248°C; IR: (ν, cm-1) 3,250 (NH), 3,070 (C-Har.), 2,970-
1
2,860 (C-Haliph.), 1,727 (C=Oester), 1,680 (C=Oimidazole), 1,610 (C=Calkene) 1,270 (C-O); H-NMR: δ
(ppm) 1.35-152 (t, CH3-CH2-), 2.31-2.52 (t, N-CH2), 3.10 (s, C=CH), 3.35-3.49 (q, CH2-CH3), 3.65-
3.92 (t, CH2-Cl), 5.22 (s, N-CH2-CO), 6.63-6.88 (d, 2H, ArH), 7.41-7.62 (d, 2H, ArH), 8.53 (s, 1H,

Molecules 2009, 14
2441
imidazole), 10.72 (s, NH); Anal. % calc./found for C19H18N7O7Cl (m.w. 491.5): C, 46.40/45.97; H,
3.96/3.65; N,19.93/18.05.
Ethyl {[3'-(2-chloroethyl)-4-(4-bromophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetate (9b): Yield: 66%; m.p. 210-212°C; IR: (ν, cm-1) 3,210 (NH), 3,080 (C-Har.), 2,966-
1
2,890 (C-Haliph.), 1,715 (C=Oester), 1,656 (C=Oimidazole), 1,612 (C=Calkene), 1,300 (C-O); H-NMR: δ
(ppm) 1.41-166 (t, CH3-CH2-), 2.36-2.48 (t, N-CH2), 3.02 (s, C=CH), 3.59-3.78 (q, CH2-CH3), 3.81-
4.05 (t, CH2-Cl), 5.53 (s, N-CH2-CO), 6.71-6.93 (d, 2H, ArH), 7.37-7.52 (d, 2H, ArH), 8.69 (s, 1H,
imidazole), 10.59 (s, NH); Anal. % calc./found for C19H18N6O5BrCl (m.w. 525): C, 43.41/43.67; H,
3.45/4.32; N, 15.99/15.11.
Ethyl {[3'-(2-chloroethyl)-4-(4-chlorophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetate (9c): Yield: 65%; m.p. 189-192°C; IR: (ν, cm-1) 3,205 (NH), 3,080 (C-Har.), 2,979-
1
2,885 (C-Haliph.), 1,730 (C=Oester), 1,670 (C=Oimidazole), 1,620 (C=Calkene) 1,250 (C-O); H-NMR: δ
(ppm) 1.52-178 (t, CH3-CH2-), 2.39-2.50 (t, N-CH2), 3.15 (s, C=CH), 3.31-3.60 (q, CH2-CH3), 3.92-
4.22 (t, CH2-Cl), 5.01 (s, N-CH2-CO), 6.57-6.88 (d, 2H, ArH), 7.41-7.59 (d, 2H, ArH), 8.32 (s, 1H,
imidazole), 10.53 (s, NH); Anal. % calc./found for C19H18N6O5Cl2 (m.w. 481): C,47.42/47.97; H,
3.77/4.29;N, 17.46/17.86.
3.10. Synthesis of 2-{[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-
biimidazol-1-yl]amino}acetohydrazides 10a-c
A mixture of compound 9 (0.01, mole) and hydrazine hydrate (99%, 0.32 g, 0.01 mole) in ethanol
(25 mL) was refluxed for 8 hrs. Upon cooling the solution a solid appeared. This was recrystallized
from ethanol to afford the desired compound.
2-{[3'-(2-Chloroethyl)-4-(4-nitrophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetohydrazide (10a): Yield: 75%; m.p. 241-244°C; IR: (ν, cm-1) 3,390-3,344 (NH2), 3,180
1
(NH), 3,060 (C-Har.), 2,950-2,880 (C-Haliph.), 1,690 (C=Oimidazole), 1,650 (C=Oamide), 1,210 (C-N); H-
NMR: δ (ppm) 2.45-2.70 (t, N-CH2), 3.21 (s, C=CH), 3.51-3.72 (t, CH2-Cl), 4.65 (s, N-CH2-CO), 6.32
(s, NH2), 6.81-7.02 (d, 2H, ArH), 7.62-7.83 (d, 2H, ArH), 8.81 (s, 1H, imidazole), 10.83 (s, NH), 11.32
(s, CO-NH-N); Anal. % calc./found for C17H16N9O6Cl (m.w. 477): C, 42.73/42.99; H, 3.38/4.06; N,
26.38/27.69.
2-{[3'-(2-Chloroethyl)-4-(4-bromophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetohydrazide (10b): Yield: 64%; m.p. 167-169°C; IR: (ν, cm-1) 3,351-3,311 (NH2), 3,160
1
(NH), 3,080 (C-Har.), 2,987-2,880 (C-Haliph.), 1685 (C=Oimidazole), 1,639 (C=Oamide), 1,230 (C-N); H-
NMR: δ (ppm) 2.63-2.90 (t, N-CH2), 3.30 (s, C=CH), 3.62-3.83 (t, CH2-Cl), 4.73 (s, N-CH2-CO), 6.41
(s, NH2), 6.73-6.92 (d, 2H, ArH), 7.51-7.72 (d, 2H, ArH), 8.67 (s, 1H, imidazole), 10.92 (s, NH), 11.82
(s, CO-NH-N); Anal. % calc./found for C17H16N8O4BrCl (m.w. 511.5): C, 39.90/40.65; H, 3.15/3.95;
N, 21.90/22.73.

Molecules 2009, 14
2442
2-{[3'-(2-Chloroethyl)-4-(4-chlorophenyl)-2'-nitro-5-oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]-
amino}acetohydrazide (10c): Yield: 68%; m.p. 179-181°C; IR: (ν, cm-1) 3,363-3,300 (NH2), 3,180
1
(NH), 3,075 (C-Har.), 2,989-2,890 (C-Haliph.), 1,695 (C=Oimidazole), 1,640 (C=Oamide), 1,220 (C-N); H-
NMR: δ (ppm) 2.73-2.95 (t, N-CH2), 3.42 (s, C=CH), 3.67-3.80 (t, CH2-Cl), 4.72 (s, N-CH2-CO), 6.52
(s, NH2), 6.82-7.99 (d, 2H, ArH), 7.32-7.52 (d, 2H, ArH), 8.82 (s, 1H, imidazole), 10.85 (s, NH), 11.75
(s, CO-NH-N); Anal. % calc./found for C17H16N8O4Cl2 (m.w. 467): C, 43.70/43.12; H, 3.95/3.32; N,
23.98/25.00.
3.11. Synthesis of N-[(amino-λ4-sulfanylidyne)methyl-2-{[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-
oxo-4,5-dihydro-1H,3'H-2,4'-biimidazol-1-yl]amino} acetothiosemicarbazides 11a-c
These compounds were synthesized by the same procedure used for compounds 10a-c.
N-[(Amino-λ4-sulf{4-nitrophenyl})methyl-2-{[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-oxo-4,5-
dihydro-1H,3'H-2,4'-biimidazol-1-yl]amino}acetothiosemicarbazide (11a): Yield: 38%; m.p. 286-
289°C; IR: (ν, cm-1) 3,390-3,355 (NH2), 3,280 (NHthiosemicarbazide), 3,170 (NH), 3,050 (C-Har.), 2,983-
1
2,890 (C-Haliph.), 1,693 (C=Oimidazole), 1,645 (C=Oamide), 1,270 (C=S); H-NMR: δ (ppm) 2.56-2.78 (t,
N-CH2), 3.27 (s, C=CH), 3.53-3.72 (t, CH2-Cl), 4.83 (s, N-CH2-CO), 6.32 (s, NH2), 6.58-6.71 (d, 2H,
ArH), 7.61-7.85 (d, 2H, ArH), 8.86 (s, 1H, imidazole), 10.45 (s, NH), 10.91 (s, N-NH-CS), 11.72 (s,
CO-NH-N); Anal. % calc./found for C18H17N10O6SCl (mw. 536.5): C, 40.27/41.87; H, 3.19/3.76; N,
26.09/25.55.
N-[(Amino-λ4-sulf{4-bromophenyl})methyl-2-{[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-oxo-4,5-
dihydro-1H,3'H-2,4'-biimidazol-1-yl]amino}acetothiosemicarbazide (11b): Yield: 42%; m.p. 282-
284°C; IR: (ν, cm-1) 3,356-3,327 (NH2), 3,259 (NHthiosemicarbazide), 3,189 (NH), 3,080 (C-Har.), 2,987-
1
2,890 (C-Haliph.), 1,700 (C=Oimidazole), 1,650 (C=Oamide), 1,268 (C=S); H-NMR: δ (ppm) 2.42-2.67 (t,
N-CH2), 3.31 (s, C=CH), 3.59-3.71 (t, CH2-Cl), 4.78 (s, N-CH2-CO), 6.13 (s, NH2), 6.42-6.68 (d, 2H,
ArH), 7.53-7.72 (d, 2H, ArH), 8.65 (s, 1H, imidazole), 10.33 (s, NH), 10.75 (s, N-NH-CS), 11.23 (s,
CO-NH-N); Anal. % calc./found for C18H17N9O4SBrCl (m.w. 570.5): C, 37.87/36.31; H, 3.00/3.75; N,
22.08/23.54.
N-[(Amino-λ4-sulf{4-chlorophenyl})methyl-2-{[3'-(2-chloroethyl)-4-arylidene-2'-nitro-5-oxo-4,5-
dihydro-1H,3'H-2,4'-biimidazol-1-yl]amino}acetothiosemicarbazide (11c): Yield: 35%; m.p. 293-
294°C; IR: (ν, cm-1) 3,402-3,381 (NH2), 3,275 (NHthiosemicarbazide), 3,140 (NH), 3,090 (C-Har.), 2,981-
2,883 (C-Haliph.), 1,683 (C=Oimidazole), 1,639 (C=Oamide), 1,259 (C=S); 1H-NMR: δ (ppm) 2.45-2.70 (t,
N-CH2), 3.23 (s, C=CH), 3.62-3.80 (t, CH2-Cl), 4.86 (s, N-CH2-CO), 6.33 (s, NH2), 6.50-6.69 (d, 2H,
ArH), 7.43-7.58 (d, 2H, ArH), 8.75 (s, 1H, imidazole), 10.46 (s, NH), 10.82 (s, N-NH-CS), 11.84 (s,
CO-NH-N); Anal. % calc./found for C18H17N9O4SCl (m.w. 526): C, 41.07/41.58; H, 3.26/4.08; N,
23.95/23.21.

Molecules 2009, 14
2443
3.12. Synthesis of 3'-(2-chloroethyl)-5- arylidene-3-{[5-mercapto-1,3,4-oxadiazol-2-yl-methyl]
amino}-2'-nitro--3,5dihydro-3'H,4H,2,4'-biimidazol-4-ones 12a-c
The corresponding compound 10 (0.01 mole) and CS2 (0.6 mL, 0.01 mole) were added to a solution
of KOH (0.56 g, 0.01 mole) in ethanol (30 mL). The reaction mixture was refluxed for 3 hrs. After
evaporation under reduced pressure to dryness, a solid was obtained. This was dissolved in H2O
(200 mL) and acidified with conc. HCl. The precipitate was filtered off, washed with water and
recrystallized from ethanol to afford the desired compound.
3'-(2-Chloroethyl)-5-(4-nitrophenyl)-3-{[5-mercapto-1,3,4-oxadiazol-2-yl-methyl]amino}-2'-nitro-3,5-
dihydro-3'H,4H,2,4'-biimidazol-4-one (12a): Yield: 63%; m.p. 302-303°C; IR: (ν, cm-1) 3,220 (NH),
1
3,080 (C-Har.), 2,987-2,890 (C-Haliph.), 2,490 (SH), 1,670 (C=Oimidazole), 1,265 (C=S); H-NMR: δ
(ppm) 2.52-2.72 (t, N-CH2), 3.27 (s, C=CH), 3.51-3.78 (t, CH2-Cl), 4.63 (s, N-CH2-oxadiazole), 6.45-
6.62 (d, 2H, ArH), 7.39-7.60 (d, 2H, ArH), 8.89 (s, 1H, imidazole), 10.52 (s, NH), 12.55 (s, NH + SH
of oxadiazole); Anal. % calc./found for C18H14N9O6Cl (m.w. 519.5): C, 41.59/41.83; H, 2.71/3.57; N,
24.25/23.61.
3’-(2-Chloroethyl)-5-(4-bromophenyl)-3-{[5-mercapto-1,3,4-oxadiazol-2-yl-methyl]amino}-2'-nitro-
3,5-dihydro-3'H,4H,2,4'-biimidazol-4-one (12b): Yield: 65%; m.p. 295-297°C; IR: (ν, cm-1) 3,235
1
(NH), 3,085 (C-Har.), 2,976-2,855 (C-Haliph.), 2,470 (SH), 1,685 (C=Oimidazole), 1,280 (C=S); H-NMR:
δ (ppm) 2.91-3.22 (t, N-CH2), 3.52 (s, C=CH), 3.69-3.80 (t, CH2-Cl), 4.51 (s, N-CH2-oxadiazole),
6.34-6.50 (d, 2H, ArH), 7.50-7.69 (d, 2H, ArH), 8.49 (s, 1H, imidazole), 10.66 (s, NH), 12.95 (s, NH +
SH of oxadiazole); Anal. % calc./found for C18H14N8O4BrCl (m.w. 553.5): C, 39.04/38.53; H,
2.55/2.97; N, 20.23/21.78.
3’-(2-Chloroethyl)-5- (4-chlorophenyl)-3-{[5-mercapto-1,3,4-oxadiazol-2-yl-methyl]amino}-2'-nitro-
3,5-dihydro-3'H,4H,2,4'-biimidazol-4-one (12c): Yield: 69%; m.p. 287-289°C; IR: (ν, cm-1) 3,215
1
(NH), 3,065 (C-Har.), 2,978-2,860 (C-Haliph.), 2,580 (SH), 1,690 (C=Oimidazole), 1,210 (C=S); H-NMR:
δ (ppm) 2.49-2.70 (t, N-CH2), 3.71 (s, C=CH), 3.92-4.00 (t, CH2-Cl), 4.42 (s, N-CH2-oxadiazole),
6.46-6.70 (d, 2H, ArH), 7.45-7.65 (d, 2H, ArH), 8.12 (s, 1H, imidazole), 10.59 (s, NH), 13.91 (s, NH +
SH of oxadiazole); Anal. % calc./found for C18H14N8O4SCl2 (m.w. 509): C, 42.45/42.65; H, 2.77/3.23;
N, 22.00/23.65.
3.13. Synthesis of 3-{[(4-amino-5-mercapto-4H-1,2,4-triazol-3-yl)methyl]amino}-3'-(2-chloroethyl)-5-
arylidene-2'-nitro-3',5-dihydro-3'H,4H-2,4'-biimidazol-4-ones 13a-c
The corresponding compound 10 (0.01 mole) and CS2 (0.6 mL, 0.01 mole) in ethanol (20 mL) were
stirred for 12 hrs. Then, diethyl ether (18 mL) was added. The precipitated solid thus obtained was
filtered, washed with cold diethyl ether, and without isolation and purification dissolved in water
(10 mL) and hydrazine hydrate (99%, 0.34 g, 0.01 mole) was added. The reaction mixture was
refluxed for 1 hr. cooled, diluted with water and acidified with acetic acid. The precipitate was filtered
off, washed with water and recrystallized from ethanol to afford the desired compound.

Molecules 2009, 14
2444
3-{[(4-Amino-5-mercapto-4H-1,2,4-triazol-3-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-nitrophenyl)-
2'-nitro-3',5-dihydro-3'H,4H-2,4'-biimidazol-4-one (13a): Yield: 53%; m.p. 243-246°C; IR: (ν, cm-1)
3,400-3,370 (NH2), 3,200 (NH), 3,060 (C-Har.), 2,966-2,872 (C-Haliph.), 2,460 (SH), 1,695
1
(C=Oimidazole), 1,220 (C=S); H-NMR: δ (ppm) 2.51-2.70 (t, N-CH2), 3.38 (s, C=CH), 3.55-3.69 (t,
CH2-Cl), 4.81 (s, N-CH2-triazole), 6.42 (s, NH2), 6.57-6.70 (d, 2H, ArH), 7.35-7.60 (d, 2H, ArH), 8.71
(s, 1H, imidazole), 10.50 (s, NH), 13.20 (s, NH + SH of triazole); Anal. % calc./found for
C18H16N11O5SCl (m.w. 533.5): C, 37.90/36.54; H, 3.00/3.76; N, 27.01/27.68.
3-{[(4-Amino-5-mercapto-4H-1,2,4-triazol-3-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-bromophenyl)-
2'-nitro-3',5-dihydro-3'H,4H-2,4'-biimidazol-4-one (13b): Yield: 55%; m.p. 232-235°C; IR: (ν, cm-1)
3,480-3,300 (NH2), 3,205 (NH), 3,075 (C-Har.), 2,980-2,880 (C-Haliph.), 2,550 (SH), 1,700
1
(C=Oimidazole), 1,250 (C=S); H-NMR: δ (ppm) 2.62-280 (t, N-CH2), 3.45 (s, C=CH), 3.61-3.80 (t,
CH2-Cl), 4.52 (s, N-CH2-triazole ), 6.53 (s, NH2), 6.70-6.92 (d, 2H, ArH), 7.42-7.60 (d, 2H, ArH), 8.80
(s, 1H, imidazole), 10.94 (s, NH), 13.22 (s, NH + SH of triazole); Anal. % calc./found for
C18H16N10O3BrSCl (m.w. 567.7): C, 38.07/37.53; H, 2.84/3.72; N, 24.67/45.51.
3-{[(4-Amino-5-mercapto-4H-1,2,4-triazol-3-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-chlorophenyl)-
2'-nitro-3',5-dihydro-3'H,4H-2,4'-biimidazol-4-one (13c): Yield: 48%; m.p. 274-276°C; IR: (ν, cm-1)
3,410-3,360 (NH2), 3,190 (NH), 3,070 (C-Har.), 2,971-2,890 (C-Haliph.), 2,560 (SH), 1,700
1
(C=Oimidazole), 1,270 (C=S); H-NMR: δ (ppm) 2.36-2.52 (t, N-CH2), 3.67 (s, C=CH), 3.81-3.96 (t,
CH2-Cl), 4.50 (s, N-CH2-triazole), 6.46 (s, NH2), 6.62-6.89 (d, 2H, ArH), 7.35-7.58 (d, 2H, ArH), 8.62
(s, 1H, imidazole), 10.62 (s, NH), 13.21 (s, NH + SH of triazole); Anal. % calc./found for
C18H16N10O3SCl (m.w. 523): C, 38.62/36.99; H, 3.06/3.25; N, 25.02/25.93.
3.14. Synthesis of 3'-(2-chloroethyl)-5-arylidene-2'-nitro-3-[(4H-1,2,4-triazol-3-yl-methyl )amino]-3,5-
dihydro-3'H,4H-2,4'-biimidazol-4-ones 14a-c
A mixture of compound 11 (0.01 mole) and sodium hydroxide (0.01 mole, as 4% solution) was
stirred for 4 hrs. After cooling, the solution was acidified with conc. HCl and the precipitate was
filtered and recrystallized from ethanol to afford the desired compound.
3'-(2-Chloroethyl)-5-(4-nitrophenyl)-2'-nitro-3-[(4H-1,2,4-triazol-3-yl-methyl)amino]-3,5-dihydro-
3'H,4H-2,4'-biimidazol-4-one (14a): Yield: 43%; m.p. 202-205°C; IR: (ν, cm-1) 3,300 (triazole, NH),
3,210 (NH), 3,066 (C-Har.), 2,982-2,877 (C-Haliph.), 2,625 (SH), 1,696 (C=Oimidazole), 1230 (C=S);
1H-NMR: δ (ppm) 2.32-2.50 (t, N-CH2), 3.31 (s, C=CH), 3.62-3.81 (t, CH2-Cl), 4.68 (s, N-CH2-
triazole), 6.61-6.82 (d, 2H, ArH), 7.42-7.65 (d, 2H, ArH), 8.72 (s, 1H, imidazole), 10.39 (s, NH), 11.32
(s, triazole NH) 13.37 (s, NH + SH of triazole); Anal. % calc./found for C18H15N10O5SCl
(m.w. 518.5): C, 41.66/42.61; H, 2.91/3.61; N, 26.99/26.13.
3'-(2-Chloroethyl)-5-(4-bromophenyl)-2'-nitro-3-[(4H-1,2,4-triazol-3-yl-methyl)amino]-3,5-dihydro-
3'H,4H-2,4'-biimidazol-4-one (14b): Yield: 61%; m.p. 213-215°C; IR: (ν, cm-1) 3,353 (triazole, NH),
3,190 (NH), 3,082 (C-Har.), 2,991-2,879 (C-Haliph.), 2,630 (SH), 1,700 (C=Oimidazole), 1,300 (C=S);

Molecules 2009, 14
2445
1H-NMR: δ (ppm) 2.41-2.66 (t, N-CH2), 3.42 (s, C=CH), 3.67-3.82 (t, CH2-Cl), 4.65 (s, N-CH2-
triazole), 6.41-6.60 (d, 2H, ArH), 7.32-7.60 (d, 2H, ArH), 8.80 (s, 1H, imidazole), 10.42 (s, NH), 11.49
(s, triazole NH) 13.41 (s, NH + SH of triazole); Anal. % calc./found for C18H15N9O5SBrCl (m.w.
552.5): C, 39.11/40.71; H, 2.74/3.43; N, 22.80/23.41.
3'-(2-Chloroethyl)-5-(4-chlorophenyl)-2'-nitro-3-[(4H-1,2,4-triazol-3-yl-methyl)amino]-3,5-dihydro-
3'H,4H-2,4'-biimidazol-4-one (14c): Yield: 45%; m.p. 241-245°C; IR: (ν, cm-1) 3,300 (triazole, NH),
3254 (NH), 3,030 (C-Har.), 2,980-2,855 (C-Haliph.), 2,570 (SH), 1,689 (C=Oimidazole), 1,256 (C=S);
1H-NMR: δ (ppm) 2.51-2.79 (t, N-CH2), 3.63 (s, C=CH), 3.60-3.85 (t, CH2-Cl), 4.71 (s, N-CH2-
triazole), 6.32-6.56 (d, 2H, ArH), 7.52-7.81 (d, 2H, ArH), 8.69 (s, 1H, imidazole), 10.52 (s, NH), 11.63
(s, triazole NH) 13.39 (s, NH + SH of triazole); Anal. % calc./found for C18H15N9O3SCl2 (m.w. 508):
C, 42.53/42.00; H, 2.97/2.13; N, 24.80/45.39.
3.15. Synthesis of 3-{[(5-amino-1,3,4-thiadiazol-2-yl)methyl]amino}-3'-(2-chloroethyl)-5-arylidene-2'-
nitro-3,5-dihydro-3'H,4H-2,4'-biimidazol-4-ones 15a-c
The corresponding compound 11 (0.01 mole) was dissolved in cold conc. sulfuric acid (10 mL) and
stirred at room temperature for 24 hrs. Then, the reaction mixture was poured into crushed ice and
diluted with water; the precipitate was filtered, washed with water and recrystallized from ethanol to
afford the desired compound.
3-{[(5-Amino-1,3,4-thiadiazol-2-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-nitrophenyl-2'-nitro-3,5-
dihydro-3'H,4H-2,4'-biimidazol-4-one (15a): Yield: 69%; m.p. 263-265°C; IR: (ν, cm-1) 3,402-3,366
(NH2), 3,205 (NH), 3,065 (C-Har.), 2,990-2,879 (C-Haliph.), 1688 (C=Oimidazole); 1H-NMR: δ (ppm) 2.34-
2.62 (t, N-CH2), 3.59 (s, C=CH), 3.65-3.78 (t, CH2-Cl), 4.82 (s, N-CH2-thiadiazole), 6.41 (s, NH2),
6.47-6.62 (d, 2H, ArH), 7.35-7.47 (d, 2H, ArH), 8.87(s, 1H, imidazole), 10.43 (s, NH); Anal. %
calc./found for C18H15N10O5SCl (m.w. 518.5): C, 41.66/41.08; H, 2.91/3.86; N, 26.99/26.12.
3-{[(5-Amino-1,3,4-thiadiazol-2-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-bromophenyl-2'-nitro-3,5-
dihydro-3'H,4H-2,4'-biimidazol-4-one (15b): Yield: 78%; m.p. 271-273°C; IR: (ν, cm-1) 3,387-3,308
1
(NH2), 3,195 (NH), 3,076 (C-Har.), 2,983-2,890 (C-Haliph.), 1,703 (C=Oimidazole); H-NMR: δ (ppm)
2.53-2.67 (t, N-CH2), 3.31 (s, C=CH), 3.72-3.95 (t, CH2-Cl), 4.63 (s, N-CH2-thiadiazole), 6.45 (s,
NH2), 6.68-6.79 (d, 2H, ArH), 7.36-7.50 (d, 2H, ArH), 8.73(s, 1H, imidazole), 10.53 (s, NH); Anal. %
calc./found for C15H15N9O3SBrCl (m.w. 552.5):C, 39.11/40.87; H, 2.74/2.06; N, 22.80/22.01.
3-{[(5-Amino-1,3,4-thiadiazol-2-yl)methyl]amino}-3'-(2-chloroethyl)-5-(4-chlorphenyl-2'-nitro-3,5-
dihydro-3'H,4H-2,4'-biimidazol-4-one (15c): Yield: 62%; m.p. 300-302°C; IR: (ν, cm-1) 3,410-3,345
(NH2), 3,215 (NH), 3086 (C-Har.), 2957-2861 (C-Haliph.), 1,702 (C=Oimidazole); 1H NMR: δ (ppm) 2.56-
2.70 (t, N-CH2), 3.43 (s, C=CH), 3.65-3.81 (t, CH2-Cl), 4.83 (s, N-CH2-thiadiazole), 6.48 (s, NH2),
6.63-6.82 (d, 2H, ArH), 7.66-7.73 (d, 2H, ArH), 8.75(s, 1H, imidazole), 10.73 (s, NH); Anal. %
calc./found for C18H15N9O3SCl2 (m.w. 508): C, 42.53/42.99; H, 2.97/2.22; N, 24.80/23.10.

Molecules 2009, 14
2446
References
1. Khabnadideh, S.; Rezaei, Z.; Khalafi, A.N.; Eskandari, E. Synthesis of metronidazole derivatives
as antigiardiasis agents. DARU 2007, 15, 17-20.
2. Foster, E.J. ; Lavigueur, C. ; KE, Y.C. ; Williams, V.E. ;Synthesis of alkyl 2-(benzoylamino)-3-
(4,5-dicyano-1H-imidazol-1-yl) propenoates. J .Mater. Chem. 2005, 37, 4062-4068.
3. Brunsveld, L.; Zong, H.; Glasbeek, M. E.W. Meijer, E.W. RNA Cleavage by a DNA Enzyme
with Extended Chemical Functionality. J. Am. Chem. Soc. 2000, 122, 6175-6182.
4. Sang, H.S.; Gregory, N.T.; Chang, J.Y. Lyotropic columnar liquid crystals based on polycatenar
1H-imidazole amphiphles and their assembly into bundles at the surface of silicon. J. Soft Mater.
2006, 2, 889-891.
5. Nguyen, H.T.; Destrade, C.; Malthete, J. Synthesis, spectroscopy, thermal studies and
supramolecular structures of two new alkali-earth 4-nitrobenzoate complexes containing
coordinated imidazole. Adv. Mater. 1997, 9, 375-388.
6. Borisch, K.; Diele, S; Goring, P.; Kresse, H.; Tschierske, C. Synthesis of Novel Organometallic
Polymers Based Upon N-Heterocyclic Carbenes. J. Mater. Chem. 1998, 8, 529-543.
7. Sharba, A.H.; Al-Bayati, R.I.; Aouad, M.; Rezki N. Synthesis of Thiadiazoles and 1, 2, 4-
Triazoles Derived from Cyclopropane Dicarboxylic acid. Molecules 2005, 10, 1153-1160.
8. Frank, P.V.; Girish, K.S.; Kalluraya, B. Solvent-free microwave-assisted synthesis of oxadiazoles
containing imidazole moiety. J. Chem. Sci. 2007, 119, 41-46.
9. Norris, J.F. Preparation of Terephthalic Acid from p-Toluic Acid. In Experimental Organic
Chemistry, 2nd ed.; Mc Graw-Hill Book Company, Inc.: New York, NY, USA, 1924; p. 173
10. Vogel, A.I. Hippuric acid. In A Text Book of Practical Organic Chemistry, 4th ed.; Longmans
Green and Co. Inc.: London, UK, 1954; p. 561.
11. Shuka, S. B.; Horan, A. A. Synthesis of Amino [ 4-{dis(2- Hydroxy Ethyl)Amino} Thenyl]
Acetic Acid Chim. Acta. 1997, 40, 80-85.
12. Prakanyi, C.; Schmidt, D.S. Synthesis of 5-Chloro-2-methyl-3-(5-methylthiazol-2-yl)-4(3H)-
quinazolinone and Related Compounds with potential Biological Activity. J. Heterocycl. Chem.
2000, 37, 725-729.
13. Sharma, R.S.; Bahel, S.C. Synthesis of Aryloxy /Acetyl Thiosemicarbazides, Substituted 1,3,4-
Oxadiazolles,1,3,4-thiadiazoles, 1,2,4-Triazoles and Related Compounds as Potential Fungicides.
J. Ind. Chem. Soc. 1982, LIX, 877-880.
14. Domirbas, N.; Domirbas, A.; Karaoylu, S.;Celik, E. Synthesis and antimicrobial activities of some
new[1,2,4]-triazolo[3,4-b]thiadiazoles and [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines. ARKIVOC,
2005, 75-91
15. Kraft, M.Y.; Kochergin, T.P.M.; Tsyganova, A.M.; Shlikhunove, V.S. Synthesis of metronidazole
from ethylenediamine. Pharm. Chem. J. 1989, 23, 861-863.
Sample Availability: Samples of compounds 1 - 15a-c are available from the authors.
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).