Convenient synthesis and antimicrobial evaluation of some novel 2-substituted-3-methylbenzofuran derivatives

Article abstract of DOI:10.1016/j.ejmech.2009.02.020

The reaction of 3-methylbenzofuran-2-carbohydrazide (1) with l-phenyl-2-bromoethanone (2a) or 2-chloro-1-(4-chlorophenyl)ethanone (2b) afforded (Z)-1,2-di[(3-methylbenzofuran-2-carbohydrazido]-1-arylethenes 5a and 5b, respectively. Single crystal X-ray an

Full text of DOI:10.1016/j.ejmech.2009.02.020

European Journal of Medicinal Chemistry 44 (2009) 3637–3644
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Convenient synthesis and antimicrobial evaluation of some novel 2-substituted-
3-methylbenzofuran derivatives
,
b
c
Hatem A. Abdel-Aziz a , Amal A.I. Mekawey , Kamal M. Dawood
*
a Department of Applied Organic Chemistry, National Research Centre, Dokki, Cairo 12622, Egypt
b Regional Center of Mycology and Biotechnology, Al-Azhar University, Cairo, Egypt
c Department of Chemistry, Faculty of Science, Cairo University, Giza 12613, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of 3-methylbenzofuran-2-carbohydrazide (1) with l-phenyl-2-bromoethanone (2a) or
2-chloro-1-(4-chlorophenyl)ethanone (2b) afforded (Z)-1,2-di[(3-methylbenzofuran-2-carbohydrazido]-
1-arylethenes 5a and 5b, respectively. Single crystal X-ray analyses of compound 5a proved that the
reaction proceeds in 2:1 molar ratio and ruled out the other possible structures 1,3,4-oxadiazine
derivative 6 or E-isomer 7. Furthermore, both of 3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile (9)
and 3-methyl-2-benzofuranoyl chloride (15) were used as starting materials for the synthesis of several
compounds, such as pyrazoles 10 and 14, oxime 11, hydrazones 12a, b and 3,1-bezoxazine 19. The newly
synthesized compounds were tested for their antimicrobial activity against five fungal species and four
bacterial species also their minimum inhibitory concentration (MIC) against most of test organisms was
performed. Some of these compounds exhibited a significant antimicrobial activity.
Received 24 December 2008
Received in revised form
18 February 2009
Accepted 19 February 2009
Available online 27 February 2009
Keywords:
Benzofurans
Pyrazoles
3,1-Benzoxazine
Antimicrobial activity
X-ray single crystal
Ó 2009 Elsevier Masson SAS. All rights reserved.
1. Introduction
10S-Bufuralol is a non-selective
b-adrenoceptor antagonist, it is
a good substrate of cytochrome P450 (CYP) and undergoes
enantioselective and regioselective oxidations in liver [19] (Fig. 1).
Encouraged by our recently reported results on the preparation
of new biologically active benzofuran derivatives [4,5,20–24], we
herein continue our research work on the synthesis of some new 2-
substituted-3-methylbenzofuran derivatives to evaluate their
antimicrobial activity.
In the recent years, benzofuran derivatives have attracted
much interest due to their useful biological and pharmacological
properties [1–3], such as anticonvulsant [4,5], anti-inflammatory
[4,5], antitumor [6,7] and antihistaminic [8] activities. They were
also found to be useful as antifungal [9,10], anthelmintic [11] and
antihyper-glycemic [12] agents. In addition, the benzofuran
derivative Amiodarone is one of the most important benzofuran-
based synthetic pharmaceutics, it is a highly effective antiar-
rhythmic agent and used in the treatment of both ventricular
and supraventricular arrhythmias [13]. The recently developed
R-(ꢀ)-1-(benzofuran-2-yl)-2-propylaminopentane, (ꢀ)-BPAP, is
hundred times more potent than the well-known antidepressant
agent (ꢀ)-Deprenyl in drug therapy of major depression with
unusual safeness [14]. On the other hand, C-2-substituted
benzofurans constitute a structural unit of a series of natural
products [15–17] such as Cicerfuran, antifungal benzofuran
derivative, was first obtained from the roots of wild species
of chickpea, Cicer bijugum, reported to be a major factor in
the defense system against Fusarium wilt [18]. Furthermore,
2. Results and discussion
2.1. Chemistry
The reaction of 3-methylbenzofuran-2-carbohydrazide (1) with
l-phenyl-2-bromoethanone (2a) in refluxing ethanol afforded
a single product based on TLC. The elemental analysis and mass
spectrum of the reaction product proved that the reaction pro-
ceeded in 2:1 molar ratio (1:2a), compatible with the molecular
formula C28H24N4O4. Spectroscopic data (IR, 1H and 13C NMR) and
X-ray single crystal analysis of the reaction product confirmed its
structure as (Z)-1,2-di[(3-methylbenzofuran-2-carbohydrazido)]-
1-phenylethene (5a) (Scheme 1) and ruled out the other possible
structure 6 [25] (Fig. 2). Essential bond lengths of 5a are listed in
Table 1. 3-Methylbenzofuran-2-carbohydrazide (1) reacted simi-
larly with 2-chloro-1-(4-chlorophenyl)ethanone (2b) under the
* Corresponding author. Tel.: þ20 2 3371635; fax: þ20 2 37601877.
E-mail address: hatem_741@yahoo.com (H.A. Abdel-Aziz).
0223-5234/$ – see front matter Ó 2009 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2009.02.020

3638
H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
I
E-one 7, which may be attributed to the hindrance factor of aryl
groups. Also, intra- and intermolecular hydrogen bonding may play
an important role in directing the molecular assembly of structure 5
in its solid state [26,27] as outlined in Fig. 3. Distances and angles of
hydrogen bonds are listed in Table 2.
O
O
N
O
NH
I
The mechanistic pathway of latter reaction is assumed to
proceed via a preliminary formation of the non-isolable interme-
diates 3a, b followed by its reaction with another molecule of
hydrazide 1 with elimination of water molecule to form the inter-
mediate 4 which was consequently tautomerized into compounds
5a, b as final products. The 1H NMR spectrum of 5a revealed two
O
(-)-BPAP
Amiodarone
MeO
NH
doublets at
J ¼ 8.1 Hz. When D2O was added to the DMSO-d6 in the NMR tube of
compound 5a, the doublet signal of H24 at 7.63 was changed to
a singlet one and the doublet one at 8.01 of H6 was disappeared.
Single crystal X-ray analysis of compound 5a showed unequivocally
that H24 and H6 are trans to each other.
d 7.63 and 8.01 due to H24 and H6, respectively, with
O
1'S-Bufuralol
Fig. 1. Structures of Amiodarone, (ꢀ)-BPAP, Cicerfuran and Bufuralol.
O
OH
O
HO
d
O
d
Cicerfuran
3-(3-Methylbenzofuran-2-yl)-3-oxopropanenitrile (9) was
prepared from the reaction of 2-bromo-1-(3-methylbenzofuran-2-
yl)ethanone (8) with potassium cyanide in ethanol at ambient
temperature. The mp, IR, mass, and 1H NMR spectra of compound 9
were found to be identical with that reported by us [23]. The
same reaction condition to give (Z)-1,2-di[(3-methylbenzofuran-2-
oyl)hydrazino]-1-(4-chlorophenyl)ethene (5b) (Scheme 1).
Single crystal X-ray analysis of compound 5a showed that its
structure exists predominantly in the Z-configuration and not the
Me
O
O
X
+
Y
O
HN NH2
1
2a,b
- HY
Me
O
H
N
O
N
O
H
X
3
1
Me
H
H
N
O
O
N
Me
O
H
H
Me
N
N
N
O
O
N
O
X
6
X
4
Me
O
O
O
H
N
H
N
(E)
O
H
N
N
H
H
Me
N
H
N
N
O
O
H
(Z)
N
5
X
Y
H
H
a
b
H
Br
Cl
X
Cl
7: (E)-isomer
5: (Z)-isomer
X
Scheme 1.

H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
3639
Table 1
Characteristic bond length [Å] of 5a.
O
C21
H
H
N8
H
N3
N
C9
O
N
N
N6
N5
N
C24
C10
H
H
N3–N5
.
N3–C9
1.351 (3)
1.377 (4)
1.293 (3)
1.364 (3)
1.275 (4)
1.358 (4)
1.447 (4)
N5–C10
N6–N8
N6–C24
N8–C21
C10–C24
corresponding hydrazones 12a, b, respectively. The IR spectra of the
latter products showed, in each case, absorption bands around
3210, 2220 and 1620 cmL1 corresponding to hydrazone NH, nitrile
and carbonyl groups, respectively.
Fig. 2. X-Ray structure of compound 5a.
reaction of compound 9 with phenylhydrazine in refluxing ethanol
afforded the corresponding 5-amino-3-(3-methylbenzofuran-2-
yl)-1-phenyl-1H-pyrazole (10) (Scheme 2). The IR spectrum of 10
showed absorption bands at 3449 and 3233 cmꢀ1 due to NH2 group
whereas its 1H NMR appeared D2O-exchangeable broad signal of
Moreover, 3-ethoxy-2-[(3-methylbenzofuran-2-yl)carbonyl]a-
crylonitrile (13) was synthesized by neat refluxing of equimolar
quantities of 3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile (9)
and triethyl orthoformate. The 1H NMR spectrum of compound 13
revealed a triplet and quartet signals at
d
0.86 and 3.7 due to the
2.59 and 8.1 due to 3-
NH2 group at d 3.45. The mass spectrum of 10 revealed a peak at m/z
ethoxy protons in addition to two singlets at
d
289 corresponding to its molecular ion.
methyl and C]CH– protons, respectively. Reaction of compound 13
with hydrazine hydrate in absolute ethanol afforded a compound
identified as 3-(3-methylbenzofuran-2-yl)-1H-pyrazole-4-carbon-
itrile (14) (Scheme 2). The IR spectrum of the latter compound
revealed two absorption bands at 3125 and 2230 cmꢀ1 assignable
to NH function and nitrile group, respectively and its 1H NMR
Next, the reaction of propanenitrile 9 with nitrous acid afforded
3-(3-methylbenzofuran-2-yl)-2-hydroximoyl-3-oxopropanenitrile
(11) as shown in Scheme 2. Its IR spectrum revealed absorption
band at 1643 cmꢀ1 assignable to carbonyl group in addition to
broad band of OH function at 3263 cmꢀ1. Interestingly, the IR
spectrum of 11 was free of nitrile absorption band due to the
presence of both nitrile function and hydroximoyl group attached
to the same carbon, in fact such cases are already known [28]. 13C
spectrum displayed a D2O-exchangeable singlet at
d 13.9 due to
pyrazole NH and characteristic singlet at 8.7 due to H-4 of pyr-
d
azole moiety in addition to a multiplet in the region
four aromatic protons.
d 7.3–7.72 of
NMR spectrum of compound 11 exhibited signal at
d 109.0 due to
the carbon of nitrile function.
Furthermore, treatment of the hydrazide 1 with 3-methyl-2-
benzofuranoyl chloride (15) in pyridine afforded the bis-ben-
zofuranoylhydrazide derivative 16 as shown in Scheme 3. The
structure of the latter product was assigned on the basis of its
Propanenitrile derivative 9 reacted also with diazonium chlo-
rides of 4-toluidine or 4-chloroaniline in cold ethanol in the pres-
ence of sodium acetate and afforded high yields of the
Me
O
O
O
H
Me
H
N
H
N
N
N
O
H
N
H
H
H
H
N
O
H
O
N
N
N
Me
H
H
O
O
HN
Me
Fig. 3. Part of the hydrogen bonding scheme in the structure of 5a.

3640
H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
Table 2
activities are shown in Tables 3 and 4, respectively. The results
revealed that most of the synthesized compounds showed variable
degrees of inhibition against the tested microorganisms. Suscepti-
bilities of the fungal and bacterial isolates to our synthesized
benzofuran derivatives were investigated by measuring their
inhibitory effect on the growth of microorganisms compared to the
solvent used.
Intra- and intermolecular hydrogen bonds of 5a.
Type, D–H/A
D–H
H/A
D/A
<(DHA)
Intramolecular
N3–H3/N6
Intermolecular
N8–H8/O2
0.960(2)
0.960(2)
1.910
2.658
3.066
132.9
157.9
2.145(2)
Distances (D–H, H/A, D/A) are given in Å, angles in ꢁ, D: donor, A: acceptor.
2.2.1. Antifungal activity
elemental analysis and spectral data (IR, 1H and 13C NMR).
Similarly, the reaction of anthranilic acid with 3-methyl-
2-benzofuranoyl chloride (15) in refluxing pyridine afforded 2-
(3-methylbenzofuran-2-carboxamido)benzoic acid (18). Our
attempts to synthesize compound 18 by reaction of the ester
20 with anthranilic acid under different reaction conditions
were failed. The IR spectrum of compound 18 showed
absorption bands at 3171 and at 1697, 1659 cmꢀ1 due to one
NH and two carbonyl functions, respectively, whereas its mass
The results obtained from the present study recorded
a remarkable difference in the antifungal effect of compounds 13,
14, 16 and 19. The inhibition zone of the latter compounds ranged
from 5 mm against Aspergillus niger to 30 mm against Syncepha-
lastrum racemosum. Compounds 12b and 18 showed weak anti-
fungal activities against tested organisms where S. racemosum was
the most susceptible strain (22 mm) followed by Candida albicans
(20 mm), Penicillium italicum (13 mm) and Aspergillus fumigatus
(12 mm). In addition, compound 12a showed 16 mm inhibition
against C. albicans (Table 3). Alternatively, compounds 5b, 10 and 11
recorded different effects where their inhibition of fungal growth
ranged from 5 mm against A. niger to 18 mm against C. albicans.
P. italicum and S. racemosum showed high ability to resist the latter
compounds. Compound 5a exhibited no ability to inhibit the
growth of any fungal species (Table 3).
spectrum showed
molecular ion.
a peak at m/z 295 corresponding to its
Compound 18 was cyclized by anhydrous sodium acetate in acetic
anhydride with heating at 140 ꢁC to afford 2-(3-methylbenzofuran-2-
yl)-4H-3,1-benzoxazin-4-one (19) (Scheme 3). The 1H NMR spectrum
of compound 23 showed the disappearance of signals due to protons
of amide and acid functions and its mass spectrum revealed a peak at
m/z 277 corresponding to its molecular ion.
2.2.2. Antibacterial activity
Compounds 12b and 18 showed moderate effects against
Staphylococcus aureus and Bacillus subtilis whereas they revealed no
effect against Pseudomonas aeruginosa and Escherichia coli (Table 4).
Compound 5a showed moderate activity against all bacterial
species (inhibition zone varied from 5 mm against E. coli to 15 mm
against S. aureus). On the other hand, compound 12a showed weak
activity against S. aureus (5 mm). In addition, data in Table 4
revealed that Gram-positive bacteria were highly susceptible
2.2. Biological activity
All synthesized compounds were screened for their antibacte-
rial and antifungal activities at 100 mg concentration. Some of our
compounds showed excellent antimicrobial activities with respect
to the control drugs. The results of the antifungal and antibacterial
Me
O
O
Br
8
KCN
Me
Me
Me
O
O
CH(OEt)3
Ph
N
PhNHNH2
N
O
CN
CN
O
O
9
NH2
10
13
OEt
NaNO2
ArN2Cl
Me
NH2NH2
CH3COOH
Me
O
Me
O
CN
O
N
NH
N
OH
O
O
11
CN
N
NC
Ar
12
12a,b
NH
14
4-Cl-C6H4
4-Me-C6H4
a
Ar
b
Scheme 2.

H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
3641
Me
O
O
OEt
20
17
HOOC
Me
Me
H2N
COOH
O
O
17
O
HN
pyridine
O
Cl
15
18
(Ac)2O
pyridine
1
Me
O
O
Me
Me
O
O
O
N
HN NH
O
O
19
16
Scheme 3.
where B. subtilis was the most susceptible strain against compound
18 (12 mm) while S. aureus showed weak effect against compound
16 (3 mm). Furthermore, compounds 5b, 10 and 11 showed ability
to inhibit the growth of all bacterial species except P. aeruginosa (no
inhibition) (Table 4).
their MIC against all test organisms. The highest antifungal and
antibacterial activities were showed by ethoxymethylene deriva-
tive 13 and ethylene 5a, respectively. The presence of pyrazole
moiety beside benzofuran ring in compounds 10 and 14 was found
to be essential for their high antifungal and antibacterial activities.
The significant antimicrobial activity of 5a and 16 may be due to the
presence of two benzofuran moieties in addition to hydrazide
function in both of them. The MIC of compounds 5a, 10, 13, 14 and
2.2.3. Minimum inhibitory concentration (MIC)
The minimum inhibitory concentration (MIC) of the synthesized
compounds against highly inhibited organisms is reported in Table
16 are 500, 250, 250, 50, 50 mg/ml, respectively.
5. Compounds 5a and 5b revealed high MIC (500
S. aureus and A. fumigatus, respectively. On the other hand,
compounds 12b, 14 and 16 exhibited low MIC (50 g/ml) against
C. albicans, A. fumigatus, P. italicum and S. racemosum. Compound 11
showed MIC 125 g/ml against B. subtilis. Additionally, compounds
10, 12a, 13, 18 and 19 exhibited MIC 250 g/ml against B. subtilis,
mg/ml) against
3. Experimental
3.1. Chemistry
3.1.1. General
m
m
m
C. albicans, A. niger and S. racemosum (Table 5).
Melting points were measured on a Gallenkamp apparatus. IR
spectra were recorded on Shimadzu FT-IR 8101PC infrared spec-
trophotometer. NMR spectra were determined in DMSO-d6 at
In conclusion, eleven benzofuran-based compounds were
synthesized and screened for their antimicrobial activity as well as
Table 3
Table 4
In vitro antifungal activity of the synthesized compounds.
In vitro antibacterial activity of the synthesized compounds.
Compound Inhibition zone [mm]
Compound
Inhibition zone [mm]
Aspergillus Aspergillus Penicillium Syncephalastrum Candida
Staphylococcus
aureus
Pseudomonas
aeruginosa
Bacillus
subtilis
Escherichia
coli
fumigatus
niger
italicum
racemosum
albicans
5a
5b
10
11
12a
12b
13
14
–
–
5
7
12
–
–
18
6
13
–
5
–
–
–
–
–
–
10
–
12
13
6
–
6
–
–
–
–
22
30
18
22
18
35
–
–
9
18
16
20
10
12
6
5a
5b
10
11
12a
12b
13
14
15
4
4
15
5
4
13
10
3
3
4
6
–
–
–
–
–
–
–
–
–
8
20
14
4
25
20
–
6
7
18
12
12
8
5
3
5
8
–
–
–
–
–
–
–
30
10
10
8
–
12
19
20
4
–
8
16
18
19
16
18
19
–
7
30
Terbinafin
30
25
20
Amoxicilline
30
25

3642
H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
Table 5
3.1.2.3. X-ray crystallography of compound 5a. The single crystal X-
ray measurement was made using maXus (Bruker Nonius, Delft &
MacScience, Japan) [33]. Mo K radiation (
Minimum inhibitory concentration (MIC).
Compounda
Microorganism
MIC [
m
g/ml]
a
l
¼ 0.71073 Å) and
a graphite monochromator were used for data collection. Crystal
data for compound 5a: C28H24N4O4, Mr, 480.524; system, mono-
clinic; Space group, P21/c; unit cell dimensions, a ¼ 7.6399 (3) Å,
5a
5b
10
Staphylococcus aureus
Aspergillus fumigatus
Bacillus subtilis
Bacillus subtilis
Candida albicans
500
500
250
125
250
50
250
50
50
50
50
250
250
11
b ¼ 22.4018 (10) Å, c ¼ 14.0064 (7) Å,
a
¼ 90.00ꢁ,
b
¼ 99.357 (3)ꢁ;
12a
12b
13
V ¼ 2365.3 (2) Å3; Z ¼ 4; Dx ¼ 1.349 mg mꢀ3
;
q
range for data
Candida albicans
Aspergillus niger
collection, 2.910–19.980ꢁ;
m(Mo Ka ; T, 298 K;
), 0.09 mmꢀ1
14
Aspergillus fumigatus
Syncephalastrum racemosum
Penicillium italicum
Syncephalastrum racemosum
Syncephalastrum racemosum
Syncephalastrum racemosum
measured reflections, 3908; independent reflections, 2397;
observed reflections, 1325; Rint, 0.030; R (all), 0.093; wR (ref), 0.094;
16
wR (all), 0.105; S (ref), 1.778; S (all), 1.795;
D/smax, 0.012; Drmax,
0.31 e Å3, Drmin, ꢀ0.43 e Å3. Crystallographic data for the structure
5a has been deposited with the Cambridge Crystallographic Data
Center (CCDC) under the number 700682. Copies of the data can be
obtained, free of charge, on application to CCDC 12 Union Road,
Cambridge CB2 1EZ, UK [Fax: þ44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or http://www.ccdc.cam.ac.uk].
18
19
a
Terbinafin and Amoxicilline exhibited 50
mg/ml against all MIC measured
organisms.
300 MHz (1H NMR) and at 75 MHz (13C NMR) on a Varian Mercury
VX 300 NMR spectrometer using TMS as an internal standard. Mass
spectra were measured on a GCMS-QP1000 EX spectrometer at
70 eV. Elemental analysis was carried out at the Microanalytical
Center of Cairo University. 3-Methyl-2-benzofurancarbohydrazide
(1) [29], 2-bromo-1-(3-methylbenzofuran-2-yl)ethanone (8) [30],
3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile (9) [23], 3-
methyl-2-benzofuranoyl chloride (13) [31] and ethyl 3-methyl-2-
benzofurancarboxylate (20) [32] were prepared by the reported
methods. 2-Bromo-1-phenylethanone 2a and 2-chloro-1-(4-
chlorophenyl)ethanone 2b were used as commercially received.
3.1.3. 3-(3-Metylbenzofuran-2-yl)-3-oxopropanenitrile (9)
To a solution of 2-bromo-1-(3-methylbenzofuran-2-yl)etha-
none (8) (5.06 g, 50 mmol) in absolute ethanol (30 ml) was added
a solution of potassium cyanide (1.3 g, 50 mmol in 5 ml water) with
stirring. The reaction mixture was stirred at room temperature for
further 4 h, then diluted with water. The solid that precipitated was
filtered off, washed with water, dried and finally recrystallized from
ethanol to afford a product identical in all respects (mp, mixed mp,
IR, mass and 1H NMR) with that we reported in previous study [23],
mp. 115–117 ꢁC.
3.1.2. General procedure for the synthesis of (Z)-1,2-di[(3-
methylbenzofuran-2-carbohydrazido)]-1-arylethene 5a, b
To a solution of 3-methyl-2-benzofurancarbohydrazide (1)
(1.9 g, 10 mmol) in ethanol (50 ml), 2-bromo-1-phenylethanone 2a
or 2-chloro-1-(4-chlorophenyl)ethanone 2b (5 mmol) was added.
The reaction was refluxed for 7 h, then to cool to room temperature.
The formed solid was filtered off, washed with ethanol and
recrystallized from EtOH/DMF to afford compounds 5a and 5b,
respectively.
3.1.4. 5-Amino-3-(3-methylbenzofuran-2-yl)-1-phenyl-1H-
pyrazole (10)
A mixture of 3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile
(9) (1.0 g, 5 mmol) and phenylhydrazine (0.54 g, 5 mmol) in ethanol
(20 ml) was refluxed for 5 h, then left to cool to room temperature.
The precipitated product was collected by filtration, washed with
ethanol and dried. Recrystallization from ethanol afforded the
pyrazole derivative 10. Yield (68%); mp 150–152 ꢁC; IR (KBr) nmax
cmꢀ1: 3449, 3233 (NH2), 1620 (C]N); 1H NMR (DMSO-d6)
: 2.58
(s, 3H, CH3), 3.45 (s, 1H, D2O exchangeable), 6.42–7.65 (m, 10H,
/
d
3.1.2.1. (Z)-1,2-Di[(3-methylbenzofuran-2-carbohydrazido)]-1-pheny-
lethene (5a). Pale yellow crystals, yield (67%); mp 292–294 ꢁC; IR
(KBr) nmax/cmꢀ1: 3450–3139 (4NH), 1688, 1658 (2C]O), 1602
ArH); 13C NMR (DMSO-d6)
d: 9.1, 111.8, 121.4, 123.2, 124.2, 127.7,
128.3, 128.7, 129.0, 129.5, 142.0, 153.5, 161.1; MS m/z (%): 289 (Mþ,
12.8), 253 (11.3), 176 (100), 159 (22.9), 131 (86.7), 102 (44.9), 77
(51.3), 51 (80.9). Anal. Calcd for C18H15N3O: C, 74.72; H, 5.23; N,
14.52. Found: C, 74.96; H, 5.13; N, 14.30%.
(C]N); 1H NMR (DMSO-d6)
d: 2.61 (s, 3H, CH3), 2.71 (s, 3H, CH3),
7.31–7.55 (m, 9H, ArH), 7.63 (d,1H, J ¼ 8.1 Hz, C]CH–), 7.71–7.81 (m,
4H, ArH), 8.01 (d, 1H, D2O exchangeable, J ¼ 8.1 Hz, NH), 8.86 (s, 1H,
D2O exchangeable, NH), 12.39 (s, 1H, D2O exchangeable, NH), 14.33
3.1.5. 3-(3-Methylbenzofuran-2-yl)-2-hydroximoyl-3-
oxopropanenitrile (11)
(s, 1H, D2O exchangeable, NH); 13C NMR (DMSO-d6)
d: 8.7, 8.8, 111.6,
112.6,120.9,121.3,123.2,123.5,123.8,124.4,126.5,127.5,127.9,128.6,
128.9, 129, 129.2, 136.7, 140.9, 141.5, 142.8, 153, 153.4, 155.7, 156.7;
MS m/z (%): 481 (Mþ þ 1, 30.7), 480 (Mþ, 33.0), 291 (6.8), 159 (100),
116 (22.5), 77 (28.7). Anal. Calcd for C28H24N4O4: C, 69.99; H, 5.03; N,
11.66. Found: C, 69.86; H, 4.92; N, 11.79%.
To a stirred cold solution of 3-(3-methylbenzofuran-2-yl)-3-
oxopropanenitrile (9) (1.99 g, l0 mmol) in glacial acetic acid (30 ml),
cold solution of sodium nitrite (0.7 g, 10 mmol) in water (10 ml) is
added drop-wise with stirring at such a rate that the temperature
remains in the range 0–5 ꢁC over a period of 30 min The mixture is
stirred for extra 30 min and then allowed to stand for 4 h, during
which time it warms up to room temperature. The solid that
precipitated was collected, washed with water and dried. Recrys-
tallization from EtOH/DMF afforded 89% yield of compound 11; mp
205–207 ꢁC; IR (KBr) nmax/cmꢀ1: 3263 (OH), 1643 (C]O); 1H NMR
3.1.2.2. (Z)-1,2-Di[(3-methylbenzofuran-2-carbohydrazido)]-1-(4-chl-
orophenyl)ethene (5b). Pale yellow crystals, yield (63%); mp
>300 ꢁC; IR (KBr) nmax/cmꢀ1: 3157 (4NH), 1680, 1658 (2C]O), 1600
(C]N); 1H NMR (DMSO-d6)
d: 2.62 (s, 3H, CH3), 2.71 (s, 3H, CH3),
7.36–7.65 (m, 5H, ArH), 7.66 (d, 1H, D2O exchangeable, J ¼ 8.4 Hz,
C]CH–), 7.77–7.83 (m, 4H, ArH), 8.02 (d, 1H, D2O exchangeable,
J ¼ 8.4 Hz, NH), 8.90 (s, 1H, D2O exchangeable, NH), 12.51 (s, 1H, D2O
exchangeable, NH),14.33 (s, 1H, D2O exchangeable, NH); MS m/z (%):
516 (Mþ þ 2, 29.8), 515 (Mþ þ 1, 31.2), 514 (Mþ, 97.9), 291 (9.5), 159
(100), 116 (26.3). Anal. Calcd for C28H23ClN4O4: C, 65.31; H, 4.50; N,
10.88. Found: C, 65.18; H, 4.68; N, 10.81%.
(DMSO-d6) d: 2.57 (s, 3H, CH3), 3.50 (br s, D2O exchangeable, 1H,
OH), 7.39–7.44 (m, 1H, ArH), 7.57–7.67 (m, 2H, ArH), 7.89 (d, 1H,
ArH, J ¼ 7.83 Hz); 13C NMR (DMSO-d6)
d: 9.8, 109, 112.1, 122.2, 123.8,
128.3, 128.4, 129.4, 132.9, 145.8, 154.1, 175.2; MS m/z (%): 228 (Mþ,
16.7), 211 (31.1), 159 (100), 103 (39.1), 77 (54.9), 51 (57.4). Anal.
Calcd for C12H8N2O3: C, 63.16; H, 3.53; N, 12.28. Found: C, 62.95; H,
3.45; N, 12.43%.

H.A. Abdel-Aziz et al. / European Journal of Medicinal Chemistry 44 (2009) 3637–3644
3643
3.1.6. General procedure for the synthesis of 3-(3-
methylbenzofuran-2-yl)-2-(4-arylhydrazono)-3-oxopropanenitrile
12a, b
chloride (15) (1.94 g, 10 mmol) was added portion-wise while
stirring over a period of 30 min. After complete addition, the
reaction mixture was stirred for further 1 h at room temperature
and then the reaction mixture was poured onto an ice–water
mixture with stirring. The precipitated solid was collected by
filtration, washed with dilute hydrochloric acid followed by cold
water, then finally dried and recrystallized from EtOH/DMF to
afford 1,2-di(3-methylbenzofuran-2-ylcarbonyl)hydrazine (16) as
To a stirred cold solution of 3-(3-methylbenzofuran-2-yl)-3-
oxopropanenitrile (9) (1.99 g, l0 mmol) in ethanol (30 ml) and
sodium acetate trihydrate (2 g), was added the appropriate diazo-
nium chloride solution (20 mmol) portion-wise over a period of
30 min at 0–5 ꢁC. After complete addition, the reaction mixture was
stirred for further 3 h at 0–5 ꢁC. The solid that precipitated was
collected, washed with water and dried. Recrystallization from
EtOH/DMF afforded the corresponding hydrazone 12a, b,
respectively.
white powder in 75% yield; mp 224–226 ꢁC; IR (KBr) nmax/cmꢀ1
3222 (NH), 1658 (C]O); 1H NMR (DMSO-d6)
: 2.57 (s, 6H, 2CH3),
:
d
7.37–7.42 (m, 2H, ArH), 7.51–7.56 (m, 2H, ArH), 7.65 (d, 2H, ArH,
J ¼ 8.28 Hz), 7.80 (d, 2H, ArH, J ¼ 7.59 Hz), 10.58 (s, 2H, D2O
exchangeable, NH); 13C NMR (DMSO-d6)
d 8.7, 111.7, 121.2, 122.5,
3.1.6.1. 3-(3-Methylbenzofuran-2-yl)-2-(4-chlorophenylhydrazono)-
3-oxopropanenitrile (12a). Yield (85%); mp 203–205 ꢁC (DMF/H2O);
IR (KBr) nmax/cmꢀ1: 3217 (NH), 2222 (C^N), 1651 (C]O), 1543
123.4, 127.6, 128.8, 141.8, 152.9, 158.8; MS m/z (%): 349 (Mþ þ 1, 2.8),
348 (Mþ, 11.1), 159 (100), 103 (18.2). Anal. Calcd for C20H16N2O4: C,
68.96; H, 4.63; N, 8.04. Found: C, 69.18; H, 4.46; N, 8.22%.
(C]N); 1H NMR (DMSO-d6)
d: 2.52 (s, 3H, CH3), 7.19–7.54 (m, 8H,
ArH), 15.11 (s, 1H, D2O exchangeable, NH); MS m/z (%): 339 (Mþ þ 2,
20.1), 338 (Mþ þ 1, 31.0), 337 (Mþ, 89.8), 159 (100). Anal. Calcd for
C18H12ClN3O2: C, 64.01; H, 3.58; N, 12.44. Found: C, 64.19; H, 3.35;
N, 12.27%.
3.1.11. 2-(3-Methylbenzofuran-2-carboxamido)benzoic acid (18)
This compound was synthesized by the same method
mentioned above for compound 16 by using 3-methyl-2-benzo-
furanoyl chloride (15) and 2-aminobenzoic acid (17) instead of
hydrazide 1. Yield (87%); mp 275–277 ꢁC (EtOH/DMF); IR (KBr)
3.1.7. 3-(3-Methylbenzofuran-2-yl)-2-(4-tolylhydrazono)-3-
oxopropanenitrile (12b)
nmax/cmꢀ1: 3171 (NH), 1697, 1659 (2C]O); 1H NMR (DMSO-d6)
d:
2.58 (s, 3H, CH3), 4.34 (s, 2H, D2O exchangeable), 6.36–7.86 (m, 8H,
ArH), 9.28 (s, 1H, D2O exchangeable); MS m/z (%): 295 (Mþ, 21.9),
159 (100), 120 (40.2), 77 (37.8). Anal. Calcd for C17H13NO4: C, 69.15;
H, 4.44; N, 4.74. Found: C, 69.33; H, 4.68; N, 4.50%.
Yield (83%); mp 177–179 ꢁC; IR (KBr) nmax/cmꢀ1: 3209 (NH),
2214 (C^N), 1620 (C]O), 1542 (C]N); 1H NMR (DMSO-d6)
d: 2.30
(s, 3H, CH3), 2.53 (s, 3H, CH3), 7.24–7.87 (m, 8H, ArH),12.48 (br s,1H,
NH); MS m/z (%): 317 (Mþ, 46.2), 159 (100). Anal. Calcd for
C19H15N3O2: C, 71.91; H, 4.76; N, 13.24. Found: C, 72.14; H, 4.49; N,
13.07%.
3.1.12. 2-(3-Methylbenzofuran-2-yl)-4H-3,
1-benzoxazin-4-one (19)
A solution of compound 18 (0.59 g, 2 mmol) and anhydrous
sodium acetate (0.16 g, mmole) in acetic anhydride (10 ml) was
heated at 140 ꢁC while stirring for 2 h, then left to cool to room
temperature. The reaction mixture was poured onto crushed ice
and the solid that formed was filtered off, washed with water and
dried. Recrystallization from EtOH/DMF afforded compound 23 in
72% yield; mp 190–192 ꢁC; IR (KBr) nmax/cmꢀ1: 1762 (C]O), 1593
3.1.8. 3-Ethoxy-2-[(3-methylbenzofuran-2-yl)
carbonyl]acrylonitrile (13)
A mixture of 3-(3-methylbenzofuran-2-yl)-3-oxopropanenitrile
(9) (1.99 g, l0 mmol) and triethyl orthoformate (1.5 g, 10 mmol) was
refluxed for 2 h, then left to cool, the resulting brown precipitate
was collected by filtration, washed with ethanol, dried and finally
recrystallized from ethanol to afford compound 13 in 65% yield; mp
158–160 ꢁC; IR (KBr) nmax/cmꢀ1: 3402 (NH2), 2214 (C^N), 1682
(C]N); 1H NMR (DMSO-d6)
d: 2.73 (s, 3H, CH3), 7.37–7.42 (m, 1H,
ArH), 7.52–7.57 (m, 1H, ArH), 7.60–7.66 (m, 1H, ArH), 7.72–7.76 (m,
(C]O), 1589 (C]N); 1H NMR (DMSO-d6)
d
: 0.86 (t, 3H, CH3,
2H, ArH), 7.84 (d, 1H, ArH, J ¼ 7.80 Hz), 7.93–7.99 (m, 1H, ArH), 8.16
J ¼ 7.2 Hz), 2.59 (s, 3H, CH3), 3.7 (q, 2H, CH2, J ¼ 7.2 Hz), 7.26–7.68
(m, 4H, ArH), 8.1 (s, 1H, CH); MS m/z (%): 254 (Mþ, 5.8), 227 (45.0),
210 (21.2), 199 (22.0), 159 (100), 131 (74.8), 105 (52.1), 77 (98.2), 51
(78.8). Anal. Calcd for C15H13NO3: C, 70.58; H, 5.13; N, 5.49. Found:
C, 70.36; H, 5.30; N, 5.74%.
(d, 1H, ArH, J ¼ 7.87 Hz); 13C NMR (DMSO-d6)
d: 9.6, 111.8, 116.9,
121.3, 123.6, 124, 126.8, 128, 128.1, 128.6, 129.1, 136.9, 140.5, 146.3,
150.7, 153.9, 158.2; MS m/z (%): 277 (Mþ, 100), 249 (20.2), 220
(39.0), 146 (17.0), 125 (10.4), 102 (26.9), 77 (33.4), 51 (21.0). Anal.
Calcd for C17H11NO3: C, 73.64; H, 4.00; N, 5.05. Found: C, 73.86; H,
3.82; N, 4.80%.
3.1.9. 3-(3-Methylbenzofuran-2-yl)-1H-pyrazole-4-
carbonitrile (14)
3.2. Antimicrobial activity
A mixture of 3-ethoxy-2-[(3-methylbenzofuran-2-yl)carbony-
l]acrylonitrile (13) (1.27 g, 5 mmol) and hydrazine hydrate (1 ml,
80%) in ethanol (20 ml) was refluxed for 6 h, then cooled. The
precipitated product was collected by filtration, washed with
ethanol and dried. Recrystallization from ethanol afforded the
pyrazole 14 in 62% yield; mp 168–170 ꢁC; IR (KBr) nmax/cmꢀ1 3125
3.2.1. Culture media
Two specific media were used for detecting the antimicrobial
activity, malt extract agar (MEA) for fungal isolates [malt extract,
20 g; bacteriological peptone, 5 g; agar, 20 g, the pH was adjusted to
5.4 ꢂ 0.2 at 25 (ꢂ2) ꢁC] while nutrient agar medium was used for
bacterial growth [beef extract, 3 g; bacteriological peptone, 5 g;
agar, 20 g, the pH was adjusted to 6.2 ꢂ 0.2 at 25 (ꢂ2) ꢁC]. Each
medium was prepared by dissolving the solid ingredients in 1 l of
cold distilled water and then heated to 60–70 ꢁC with stirring.
Media were sterilized by autoclaving at 121 ꢁC (1.5 atm) for 15–
20 min [34].
(NH), 2230 (C^N), 1628 (C]O); 1H NMR (DMSO-d6)
d: 2.52 (s, 3H,
CH3), 7.31–7.43 (m, 2H, ArH), 7.61 (d, 1H, ArH, J ¼ 7.96 Hz), 7.72 (d,
1H, ArH, J ¼ 7.35 Hz), 8.74 (s, 1H, pyrazole), 13.9 (s, 1H, D2O
exchangeable, NH); 13C NMR (DMSO-d6)
d: 8.7, 88.9, 111.2, 114.1,
120.2, 121.0, 123.1, 125.6, 126.3, 129.5, 153.4; MS m/z (%): 241 (Mþ,
18.5), 210 (22.9), 159 (100). Anal. Calcd for C13H9N3O: C, 69.95; H,
4.06; N, 18.82. Found: C, 70.17; H, 4.13; N, 18.74%.
3.2.2. Microorganisms
3.1.10. 1,2-Di(3-methylbenzofuran-2-ylcarbonyl)hydrazine (16)
To a cold solution of 3-methyl-2-benzofurancarbohydrazide (1)
(1.90 g, 10 mmol) in pyridine (20 ml), 3-methyl-2-benzofuranoyl
Nine clinical fungal strains employed for this investigation
include four filamentous fungi (A. fumigatus, A. niger, P. italicum and
S. racemosum) and one unicellular fungi (C. albicans) and two Gram

3644
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