Synthesis, characterization and evaluation of the substituent effect on the amoebicide activity of new hydrazone derivatives

Article abstract of DOI:10.1039/c4md00075g

A series of 10 hydrazones were synthesized by condensation of the selected hydrazine and the appropriate aldehyde. After the characterization and electrochemical analysis of each compound, amoebicidal activity was evaluated in vitro against the HM1:IMSS s

Full text of DOI:10.1039/c4md00075g

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CONCISE ARTICLE
Synthesis, characterization and evaluation of the
substituent effect on the amoebicide activity of
new hydrazone derivatives†
Cite this: Med. Chem. Commun., 2014,
5, 989
Yanis Toledano-Magana,a Ruth Melendrez-Luevano,b Marisol Navarro-Olivarria,b
˜
´
´
Juan Carlos Garcıa-Ramos,c Marcos Flores-Alamo,c Luis Ortiz-Frade,d Lena Ruiz-
´
c
b
*
Azuara and Blanca M. Cabrera-Vivas
A series of 10 hydrazones were synthesized by condensation of the selected hydrazine and the
appropriate aldehyde. After the characterization and electrochemical analysis of each compound,
amoebicidal activity was evaluated in vitro against the HM1:IMSS strain of Entamoeba histolytica. The
results showed the influence of the nitrobenzene group and the hydrazone linkage over the
amoebicidal activity. Compound 1 presents a promising amoebicidal activity with an IC50 ¼ 0.98 mM,
which represents
a
7-fold increase in the potency of cell growth inhibition with respect to
6.8 mM). Moreover, compounds and present an amoebicidal activity
metronidazole (IC50
¼
2
4
Received 21st February 2014
Accepted 7th May 2014
comparable to the reference compound. These results show that the electronic environment of
hydrazone derivatives reflected in redox potential values of the hydrazone linkage and the nitro group
plays a fundamental role in the amoebicidal activity. The molecular structure of compound 1 was
reported.
DOI: 10.1039/c4md00075g
www.rsc.org/medchemcomm
indicates that “Metronidazole is reasonably anticipated to be a
human carcinogen based on sufficient evidence of carcinoge-
nicity from studies in experimental animals”.6 Therefore, new
and better alternative therapies are required to control
amoebiasis.
Introduction
Entamoeba histolytica is the parasite responsible for human
amoebiasis, a disease characterized by extensive tissue destruc-
tion.1 Amoebiasis is globally considered as a leading parasitic
cause of human mortality. About 10% of the world's population
is affected by amoebiasis and approximately 40 000–100 000
deaths per year are related to this protozoan, mainly in devel-
oping countries.2 Metronidazole and other nitroimidazole
compounds are effective for the treatment of invasive
amoebiasis but are less effective eliminating parasites located in
the intestinal lumen. Several side effects were reported
passing from vomiting and diarrhea to hallucinations,3 besides
the appearance of resistant strains to this drug.4 While some
authors still debate about whether or not metronidazole can
induce encephalopathy,5 the US National Toxicology Program
It has been reported that hydrazones present antidepres-
sant,7 anticonceptive,8 and anticancer9 activity. On the other
hand, some derivatives have been assessed as antimicrobial10
and bactericidal agents,11 showing promising results against
Mycobacterium tuberculosis12 as well as in parasitic diseases such
as leishmaniasis,13 Chagas disease14 and amoebiasis.15
In this work the synthesis, characterization, electrochemical
behavior and amoebicidal activity of 10 hydrazones sharing a
common feature, the hydrazone linkage are reported. In these
compounds, the substituent was modied to evaluate its
inuence over the amoebicidal activity. The results have shown
a clear relationship of the amoebicidal activity with the redox
potential of the evaluated molecules. The best amoebicidal
activities have been shown by hydrazones with a nitro group as a
substituent.
a
´
´
Departamento de Inmunologıa, Instituto de Investigaciones Biomedicas, Universidad
´
´
Nacional Autonoma de Mexico. Av. Universidad 3000, CU, 04510, Mexico City, Mexico
b
´
´
´
´
Departamento de Quımica Organica, Facultad de Ciencias Quımicas, Benemerita
´
Universidad Autonoma de Puebla. 72570, Puebla, Pue., Mexico. E-mail:
bmcabreravivas@yahoo.com
Results and discussion
c
´
´
´
Departamento de Quımica Inorganica y Nuclear, Facultad de Quımica, Universidad
´
´
Nacional Autonoma de Mexico, Avenida Universidad 3000, 04510 Mexico City, Mexico Synthesis
d
´
´
Electrochemistry Department, Centro de Investigacion y Desarrollo Tecnologico en
The synthesis of hydrazones derivatives consists of the
condensation reaction of the selected hydrazine with the
appropriate aldehyde as illustrated in Scheme 1. Detailed
reaction conditions can be found in our previous studies.16
´
´
´
Electroquımica S.C. Parque Tecnologico Queretaro, Sanfandila, Pedro de Escobedo,
´
C.P. 76703 Queretaro, Mexico
† Electronic supplementary information (ESI) available: Bond distances, angles
and details of data collection and renement. See DOI: 10.1039/c4md00075g
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Scheme 1 General reaction pathway used to synthesize the studied hydrazones. Syntheses were done in ethanol at room temperature.
electrogeneration of the radical anion in the redox process
R–NO2 + 1e / R–NO2cꢁ.19 On the other hand, when the potential
was switched at ꢁ1.705 V one irreversible oxidation signal IIc was
detected (Fig. 2). This signal can be associated with irreversible
electron transfer with the cleavage of the N–N bond followed by
proton release. From the voltammogram presented in Fig. 2 a
change in the potential peak value and current peak value for
signal Ia and the appearance of one oxidation process IIIa can also
be observed. This behaviour is a consequence of the protonation
of the radical anion in process Ia and the formation of a new
product in process IIIa. The absence of the corresponding
oxidation signal for process II lead us to use square wave vol-
tammetry in order to obtain a parameter related to the reduction
tendency of the studied hydrazones, which can be correlated with
the biological activity observed, as discussed below. The reduc-
tion peak potentials of the hydrazone linkage (IIc) and the
nitrobenzene group when present in the molecule (Ic) for
compounds 1–10 are listed in Table 1.
Molecular structure of compound 1
The asymmetric unit consists of one molecule of compound 1
(1-((5-(4-nitrophenyl)furan-2-yl)methylene)-2-phenylhydrazine)
that adopts an E conguration of the azomethine C]N double
bond. Molecules are approximately planar with a N2–N1–C1–C6
torsion angle of 11.1(2)ꢀ. The furan ring makes dihedral angles
of 1.2(2) and 7.5(2), respectively, with the methylidenehydrazine
C]N–N plane and the benzene ring. The N–N distance
˚
[1.3580(17) A] is similar to that found in other hydrazones
derived from phenylhydrazine such as (E)-1-(2-nitro-
benzylidene)-2-phenylhydrazine [1.349(2) A] and (E)-1-(4-
methoxybenzylidene)-2-phenylhydrazine [1.3641(16) A] and
even similar to the N–N distance found in compound 6 (E)-2-((5-
˚
17
˚
(4-nitrophenyl)furan-2-yl)methylene)-1,1-diphenyl
hydrazine
˚
˚
[1.356(3) A]. The N2C]C7 double bond distance [1.285(2) A] is
˚
in the range of a typical NC]C bond distance [1.279(8) A]
reported by Allen.18 The crystal packing shows N–H.O
˚
hydrogen bonds with interaction distance 3.0456(17) A. Three of
the molecules generates R33 (37) rings. The molecular structure
of compound 1 is shown in Fig. 1.
Electrochemical studies
Electrochemical behaviour was explored by cyclic voltammetry
and square wave voltammetry using 1 mM hydrazone in dime-
thylsulfoxide (DMSO) solution was used for all experiments.
Fig. 2 shows the typical cyclic voltammogram of compound 7
varying the switching potential E+l. When the potential scan was
inverted at ꢁ1.289 V (Fig. 2) one reduction signal Ic and its cor-
responding oxidation signal Ia were observed. The DEp value near
Fig. 1 Molecular structure of compound 1 (E)-1-((5-(4-nitrophenyl)
to 60 mV indicates reversible electron transfer, attributed to the furan-2-yl)methylene)-2-phenylhydrazine (50% probability level).
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Compound 1 has shown high capacity to inhibit the prolif-
eration of trophozoites of Entamoeba histolytica than the most
used compound in the treatment of human amoebiasis,
metronidazole. This compound presented an IC50 ¼ 0.98 mM,
which represents a 7-fold increase in the potency of cell growth
inhibition with respect to metronidazole (IC50 ¼ 6.8 mM). While,
compounds 3, 6 and 7 with the presence of the nitrobenzene
group in their structures have shown amoebicidal activities that
can be considered acceptable with IC50 values of 13, 16 and
19 mM, respectively.
The high amoebicidal activity of compound 1 could be
directly associated with the redox potential value of the nitro-
benzene moiety (E ¼ ꢁ0.425 V) which is lower than that
observed for the nitro group of metronidazole, E ¼ ꢁ0.486 V vs.
the normal hydrogen electrode (NHE)23 (Table 1). The nitro
group reduction redox potential values of compounds 1, 3, 6
and 7 have an inverse relationship with the amoebicidal activity
as seen in Fig. 3a. As the reduction redox potential becomes
more negative, a decrease in amoebicidal activity is observed.
According to these results, it is patent that structural modi-
cations producing a decrease of the reduction redox potential
values for the nitro group lead to an increase of the amoebicidal
activity. Comparing the structure of compounds 1 and 6 it is
clear that the presence of a phenyl ring in the structure instead
of a hydrogen atom (R1 in Scheme 1) produces a difference of
the redox potential of the nitrobenzene moiety of 300 mV. The 3-
nitrophenyl group instead of the 4-nitrophenylfuran-2-yl group
generates almost the same difference of the redox potential
between compounds 1 and 7.
Compounds 2 and 4 also have important growth inhibition
potency comparable with metronidazole, with an IC50 value of
18 and 7.6 mM, respectively, even with the absence of the nitro
group in their structures. The amoebicidal activity of compound
4 could be related to the presence of the thiophene group in its
structure. Thiophene can be oxidized to generate sulfoxide
derivatives, which have been already identied as highly reac-
tive compounds that could cause the parasite death through a
redox imbalance mechanism different from that exerted by the
compounds with nitrobenzene. Again, the structural modica-
Fig. 2 Electrochemical behaviour of compound 7 studied in DMSO
employing a platinum disk as the working electrode. Cyclic voltam-
mogram scan rate: 0.1 V sꢁ1
.
Table 1 Redox potential values of the hydrazone linkage and the
nitrobenzene group. Inhibitory concentration values for compounds
1–10 against E. histolytica cultures
Compound
EII a (V)
EI b (V)
IC50 (mM)
c
c
1
2
3
4
5
6
7
8
ꢁ0.896
ꢁ0.950
ꢁ1.003
ꢁ1.150
ꢁ1.167
ꢁ1.240
ꢁ1.340
ꢁ1.487
ꢁ1.541
ꢁ1.749
—
ꢁ0.425
—
0.98
18.0
13.0
7.6
47.0
16.0
19.0
96.0
120.0
78.0
6.8
ꢁ0.658
—
—
ꢁ0.725
ꢁ0.739
—
—
—
9
10
Metronidazole
ꢁ0.486
a
Reduction peak potential values associated with the hydrazone
b
linkage. Redox potential values associated with the nitrobenzene
group. Redox potential values were referenced to NHE employing E0 ¼
0.640 V vs. NHE for the Fc|Fc+ couple.
Amoebicidal activity
Metronidazole has become the drug of choice following recog- tion is manifested comparing the amoebicidal activity of
nition of its amoebicidal properties in the mid-1960s. Since compound 4 with that shown by compound 9, for the latter the
then, nitroimidazole derivatives have been assayed as amoebi- thiophene group was substituted by a furan group with a 16-fold
cides and their activities are associated with the redox decrease of the amoebicidal activity.
biotransformation of the nitro group that generates a short-
Trying to explain the amoebicidal activity of compounds
lived nitroso free radical.20 The production of reactive oxygen without the nitrobenzene group, we explored the inuence of
species (ROS) by nitroimidazoles has been proposed as the the hydrazone linkage over it. Recent reports suggest that the
principal effect that leads to the elimination of the parasite, but amoebicidal activity enhancement of hydrazone derivatives
the presence of superoxide dismutase (SOD) of Entamoeba relies on the [–NH–N]CR1R2] linkage due to their capacity to
histolytica induces ROS regulation.21 Moreover, resistance to participate in the formation of hydrogen bonds.15 Under our
metronidazole and other nitroimidazole compounds has been experimental conditions it was possible to explore the electro-
observed in the laboratory and clinically. The resistance chemical behaviour of the hydrazone linkage.
mechanism has been investigated and is related to the down
Amoebicidal activity presents a general tendency to decrease
regulation of the pyruvate ferredoxin pathway in addition to the as the reduction redox potential of the hydrazone moiety
stress mechanism including superoxide dismutase and perox- increases (Fig. 3b). Particular cases can be discussed taking into
iredoxin.22 This raises the need to generate compounds capable account the different substituents in the molecules.
of producing a higher redox imbalance in the cell environment Compounds 4, 6, 7 and 10 with two aromatic rings as substit-
which produce several effects over the parasite.
uents of the hydrazone present an inverse relationship between
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Fig. 3 Inverse relationship found for (a) nitrobenzene redox potential values and amoebicidal activity, and (b) reduction potential peak values of
hydrazone linkage and amoebicidal activity of studied hydrazones 1–10.
the reduction redox potential of the hydrazone and the IC50 in bearing a free N–H group.15 Siddiqui and co-workers concluded
E. histolytica cultures. The equation that describes this that pyridyl, azomethine groups as well as the substituents
behaviour is
played a crucial role in amoebicidal activity.21 It is also reported
that the antileishmanial activity of 2-methoxybenzoylhydrazone
mainly depends upon the presence of hydroxyl and methoxy
groups and their respective position on the ring.24
Compound 6 which has a nitro group in its structure pres-
ents an IC50 value of 16 mM, while compound 9 without a nitro
group in its structure is less active with an IC50 value of 120 mM,
which evidences again the importance of the substituents and
the relevance of the nitro group in the amoebicidal activity of
the hydrazones (Fig. 4). Even though the number of evaluated
compounds is not enough to realize a multivariable correlation
to identify the contribution of the redox potentials over the
amoebicidal activity, using both redox potential values, nitro-
benzene and hydrazone groups of compounds 1, 3, 6 and 7
IC50 ¼ ꢁ208.05 ꢁ 119.59EII , R2 ¼ 0.9978
(1)
c
The same behaviour is observed for compounds 1, 5 and 9. In
this case the structure differs by one less aromatic ring as shown
in Scheme 1, and the equation that describes it is
IC50 ¼ ꢁ185.17 ꢁ 284.98 EII , R2 ¼ 0.9970
(2)
c
From eqn (1) and (2), it can be established that structural
modications in the second group produce a higher effect on
the biological activity, due to the coefficients that quantify the
contribution of the reduction redox potential. In this way it is
interesting to note that the effect of the hydrazone linkage over
the biological activity presents the same tendency as the one
found on the nitro group reduction.
produce the equation IC50 ¼ ꢁ5.4175EII ꢁ 47.2315EI
ꢁ
c
c
23.8959; n ¼ 4; R2 ¼ 0.9708; F ¼ 50.93, where it is clear that the
main component in the description of the amoebicidal activity
of these compounds is the reduction redox potential of the
nitrobenzene group, while the hydrazone linkage function is
such as a secondary modulator, due to the 10-fold lower value of
its coefficient compared to the value that corresponds to the
nitrobenzene group. However, these values have to be consid-
ered carefully.
This effect can be appreciated comparing the reduction
redox potential of the hydrazone linkage and the amoebicidal
activities of compounds 1, 3 and 6. Compound 1 has the lowest
redox potential (ꢁ0.896 V) for this group as well as the lowest
inhibitory concentration (0.98 mM); followed by compound 3
(ꢁ1.003 V, 13 mM) and compound 6 (ꢁ1.240 V, 16 mM). Other
examples without a nitro group are compounds 2 and 5 where
the former has a reduction redox potential of ꢁ0.95 V and
IC50 ¼ 18 mM and the latter has a reduction redox potential of
ꢁ1.67 V and IC50 ¼ 47 mM. These could be extremely relevant
because Entamoeba histolytica as other parasites does not
possess the capacity to manage the redox imbalance produced
by the hydrazone derivatives administrated to the culture.
The structural–activity relationship has been observed in 2-
(quinolin-8-yloxy) acetylhydrazone derivatives which showed
excellent amoebicidal activity compared to the cyclised prod-
ucts and is associated with the presence of a quinolone nucleus
and hydrazone linkage. In this case they have reported that the
higher amoebicidal activity (0.03–0.08 mM) was exhibited by
Fig. 4 Viability of Entamoeba histolytica. Cultures of Entamoeba his-
tolytica treated with 1 mM of compounds 9 and 6 stained with car-
boxyfluorescein diacetate (CFDA) and propidium iodide (PI), 72 h after
administration. Shifting of green to yellowish fluorescence indicates
compounds with a quinolone nucleus with a hydrazone linkage the decrease of viability. Nuclei of dead cells (white arrows).
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Inuence of hydrazone substituents on the amoebicidal the thiophene group. Besides, the modulation of the reduction
activity of the compounds studied here can be appreciated redox potential due the modication of the substituents on the
comparing the redox potential and amoebicidal activity of hydrazone linkage has to be exploited to nd new amoebicidal
compounds 1 and 6. The phenyl group present in compound 6 agents.
generates an increase of 0.344 V in the reduction potential
values for hydrazone linkage and 0.3 V for the reduction of the
nitro group, while the incorporation of the 5-((4-nitrophenyl)
furan-2-yl)methylene moiety as a nitrogen substituent in
Materials and methods
Chemistry
compound 3 produces differences of 0.1 and 0.233 V for these The hydrazones were synthesized by condensation reaction
groups with respect to compound 1 (Table 1). The same effect is under the experimental conditions studied by our research
observed in the redox potential of the compound that does not group;16 briey, 1.0 chemical equivalents of the corresponding
possess the nitrobenzene moiety. The redox potential of the hydrazine were dissolved in ethanol. A chemical equivalent of
hydrazone linkage of compounds 2, 5 and 8–10 is modied as a the desired aldehyde previously dissolved in the same solvent
function of the substituent present. The presence of furan and was added drop by drop under continuous stirring. The reaction
phenyl rings produces the stabilization of the hydrazone mixture was kept at room temperature and was monitored by
linkage reected in the energy employed for the reduction of TLC, and then vacuum ltered. The hydrazones were recrystal-
this part of the molecule (compounds 8–10), while the presence lized and puried employing a chromatographic column. The
of an electron withdrawing substituent such as a carbonyl group hydrazones were characterized by mp, elemental analysis, UV-
produces the inverse effect (see Table 1). The increase of energy vis and IR spectroscopy, 1H NMR, 13C NMR, COSY, HSQC and in
employed in the reduction of the hydrazone group generates a the case of compound 1 by X-ray diffraction.
decrease in the amoebicidal activity of the compounds evalu-
UV spectra were recorded on a Varian Cary 50 Bio UV Visible
ated in this work. Thus, differences in redox potential values are spectrophotometer; IR (KBr) spectra were recorded on a Nicolet
responsible for the differences observed in the amoebicidal FTIR Magna 750. Elemental analysis data were obtained in a
activity.
Fisons Instruments Analyzer model EA 1108, using a sulfanil-
The behaviour observed in Fig. 3 between the redox potential amide standard. H NMR and 13C NMR spectra were obtained
and the amoebicidal activity is also observed employing the on a Varian VX-300 (300 MHz); chemical shis were obtained on
chemical shi of the iminic proton of the hydrazones. Our the delta scale as parts per million (ppm) with acetone d6. Mass
results suggest that the hydrazone linkage not only participates spectra were recorded on a JEOL JEM JMS-SX 102 a 70 eV, data
in the hydrogen bond formation but also in the redox process. in mass/charge units (m/z). The reactants and the deuterated
This implies that the amoebicidal activities of the studied solvents were obtained from the Aldrich Company and were
hydrazones have to be related to the capacity of the molecule to used without further purication. The reactions were moni-
distribute the electronic density over the whole molecule, which tored by TLC, aluminum Alugram Sil G/UV254 of 0.54 mm
has a direct effect over the energy employed to reduce the nitro thickness.
1
group, the hydrazone linkage and the generation of hydrogen
bonds. Other analyses have to be done with the aim of deter-
(E)-1-((5-(4-Nitrophenyl)furan-2-yl)methylene)-2-phenylhydrazine
ꢀ
˜
(1). Wine, borgona crystals; yield: 75% at 25 C, mp. 175–176
mining the mechanism of hydrazones over the cultures of ꢀC. Anal. calc. for C17H13N3O3 (MW ¼ 307 g molꢁ1) C, 66.4; H,
Entamoeba histolytica parasites, as well as cytotoxic evaluation 4.3; N, 13.7. Found: C, 66.6; H, 4.2; N, 13.7%. C17H13N3O3 UV
since hydrazones seem to be very good candidates as drugs to lmax ¼ 419 nm. FT. IR (lm): (cmꢁ1): 3098 n(C–H, Ph), 1586
treat amoebiasis.
n(C]N), 1650–2000 n(Ph). 1H NMR 300 MHz, (CD3)2CO: (d/ppm,
J/Hz):9.54 (s, 1H, NH), 8.27 (td, 2H, C300), 7.93 (td, 2H, C200), 7.78
(s, 1H, C]N), 7.24 (dd, 2H, C30), 7.19 (d, 1H, 40), 7.14 (dd, 2H,
C20), 6.82 (td, 1H, C4), 6.76 (d, 1H, C3). 13C NMR (300 MHz,
Conclusions
In this work the synthesis, characterization and amoebicidal (CD3)2CO): (d/ppm): 153.10 (C5), 151.10 (C40), 144.86 (C2),
activity of ten new hydrazone derivatives are reported. 135.97 (C10), 129.11 (C30), 126.26 (C]N), 124.29 (C300), 123.82
Compound 1 has shown a seven-fold increase in the amoebi- (C200), 119.73 (C400), 113.25 (C100), 112.37 (C200), 111.81 (C4),
cidal activity compared to the rst choice drug for human 111.02 (C3). MS-EI: m/z ¼ 307 M+.
amoebiasis, metronidazole. Other ve compounds, 2, 3, 4, 6 and
(2E,20E)-2,20-(Hydrazine-1,2-diylidene)bis(1,2-diphenyletha-
7, have shown comparable growth inhibition capacity to none) (2). Yellow solid; yield: 80% at 25 ꢀC, mp. 185–187 ꢀC.
metronidazole. The obtained results let us conclude that the Anal. calc. for C28H20N2O2 (MW ¼ 416.47 g molꢁ1) C, 80.7; H,
electronic environment of the molecule is directly related to the 4.8; N, 6.7. Found: C, 81.1; H, 4.6; N, 6.8%. C28H20N2O2. UV
amoebicidal activity. The most active compounds possess the lmax ¼ 382 nm. FT-IR (lm): (cmꢁ1): 3125 n(C–H, Ph), 1774
nitrobenzene group in their structures. Our results show that (C]O), 1680, n(C]N), 710 n(CH). 1H NMR 300 MHz, (CD3)2CO:
both reduction of potential values, nitrobenzene and hydrazone (d/ppm, J/Hz): 7.95 (m, 4H, C2), 7.77 (m, 2H, C4), 7.63 (m, 8H,
linkages, are involved in the amoebicidal activity of these C3, C30), 7.49 (m, 2H, C40), 7.41 (m, 4H, C20). 13C NMR (300 MHz,
compounds. The former is the main actor while the latter (CD3)2CO): (d/ppm): 197.45 C1A, 167.05 (C2A), 135.41 (C1),
functions as a modulator of the amoebicidal activity. The 134.12 (C4), 132.12 (C10), 131.72 (C40), 129.17 (C3), 129.01 (C30),
activity shown by compound 4 is associated with the presence of 128.66 (C2), 128.07 (C20). MS-EI: m/z ¼ 416 M+.
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(C1), 132.30 (C]N), 130.03 (C30), 126.58 (C2), 125.35 (C40),
123.88 (C3), 122.43 (C20). MS-EI: m/z ¼ 317 M+.
(1E,2E)-1,2-Bis-((5-(4-nitrophenyl)furan-2-yl)methylene) hydra-
ꢀ
ꢀ
zine (3). Orange crystals; yield: 90% at 25 C, mp. 263–269 C.
Anal. calc. for C22H14N4O6 (MW ¼ 430 g molꢁ1) C, 61.4; H, 3.3;
N, 13. Found: C, 61.7; H, 3.42; N, 12.78%. UV lmax ¼ 416 nm. FT.
IR (lm): (cmꢁ1): 3125 n(C–H, Ph), 1574 n(C]N), 1690–2000
(1E,2E)-1,2-Dibenzylidenehydrazine (8). Yellow crystals;
yield: 81% at 25 ꢀC, mp. 85–89 ꢀC. Anal. calc. for C14H12N2 (MW
¼ 208 g molꢁ1) C, 80.7; H, 5.8; N, 13.5. Found: C, 80.4; H, 5.72;
N, 13.20%. UV lmax ¼ 313 nm. FT. IR (lm): (cmꢁ1): 3125 n(C–H,
Ph), 1574 n(C]N), 1690–2000 n(Ph), 752, 691g(CH). 1H NMR 300
MHz, (CD3)2CO: (d/ppm, J/Hz): 8.67 (s, 2H, C]N), 7.91 (m, 4H,
C3), 7.50 (d, 4H, C2), 7.49 (d, 2H, C4). 13C NMR (300 MHz,
(CD3)2CO): (d/ppm): 161.56 (C]N), 134.47 (C1), 131.19 (C4),
128.83 (C2), 128.47 (C3). MS-EI: m/z ¼ 208 M+.
1
n(Ph). H NMR 300 MHz, (CD3)2CO: (d/ppm, J/Hz): 8.19 (d, 2H,
C3), 7.88 (d, 2H, C4), 7.49 (t, 4H, C30), 7.27 (s, 2H, C]N), 7.26 (t,
4H, C20). 13C NMR (300 MHz, (CD3)2CO): (d/ppm): 146.90 (C40),
143.08 (C5), 142.82 (C10), 132.33 (C]N), 130.03 (C30), 126.60
(C4), 125.35 (C2), 123.88 (C20), 122.46 (C3). MS-EI: m/z ¼ 430 M+.
(E)-1,10-Diphenyl-2-(thiophen-2-ylmethylene) hydrazine (4).
Light Yellow crystals; yield: 75% at 25 ꢀC, mp. 117–119 ꢀC. Anal.
calc. for C17H14N2S (MW ¼ 278 g molꢁ1) C, 73.3; H, 5.1; N, 10.1.
Found: C, 73.2; H, 5.0; N, 10.15%. UV lmax ¼ 412 nm. FT. IR
(lm): (cmꢁ1): 3097 n(C–H), 1667–1920 n(Ph), 1585 n(C]N),
1490 n(C]C), 695 n(C–S). 1H NMR 400 MHz, (CD3)2CO: (d/ppm,
J/Hz): 7.44 (m, 4H, C30), 7.37 (d, 1H, C5), 7.36 (s, 1H, C]N), 7.21
(m, 2H, C40), 7.17 (dd, 4H, C20) 7.02 (dd, 1H, C3), 6.98 (dd, 1H,
C4). 13C NMR (300 MHz, (CD3)2CO): (d/ppm): 143.39 (C2), 141.67
(C10), 130.52 (C5), 129.89 (C30), 127.32 (C4), 127.01 (C3), 125.61
(C]N), 124.64 (C40), 122.24 (C20). MS-EI: m/z ¼ 278.37M+.
(2E,20E)-2,20-(Hydrazine-1,2-diylidene)bis(1,2-diphenyletha-
none)(E)-1,2-diphenyl-2-(2-phenylhydrazono)ethan-1-one (5).
(E)-1-(Furan-2-ylmethylene)-2-phenylhydrazine (9). Dark
ꢀ
ꢀ
brown; yield: 70% at 25 C, mp. decomposition above 150 C.
Anal. calc. for C11H10N2O (MW ¼ 186 g molꢁ1) C, 71.0; H, 5.4; N,
15. Found: C, 71.3; H, 5.15; N, 14.82%. UV lmax ¼ 336.12 nm. FT.
IR (lm): (cmꢁ1): 3421 n(N–H), 1452 n(C]N). 1H NMR 300 MHz,
(CD3)2CO: (d/ppm, J/Hz): 9.66 (s, 1H, NH), 9.65 (s, 1H, C]N),
7.92 (m, 2H, C4, C3), 7.42 (d, 1H, C5), 7.41 (d, 2H, C20), 6.73 (m,
3H, C30, C40). 13C NMR (300 MHz, (CD3)2CO): (d/ppm): 177.62
(C]N), 167.05 (C10), 153.39 (C2), 148.52 (C20), 121.43 (C5),
121.42 (C3), 121.35 (C4), 114.50 (C40), 112.61 (C30). MS-EI: m/z ¼
186 M+.
(E)-1-Benzylidene-2,20-diphenylhydrazine (10). Colorless
crystals; yield: 79% at 25 ꢀC, mp. 116–118 ꢀC. Anal. calc. for
ꢀ
ꢀ
Yellow crystals; yield: 80% at 25 C. 158–161 C. Anal. calc. for
C
19H16N2 (MW ¼ 272 g molꢁ1) C, 83.8; H, 5.9; N, 10.3. Found:
C
20H16N2O (MW ¼ 300.35 g molꢁ1) C, 79.9; H, 5.3; N, 9.3.
83.4; 5.8; 9.95%. UV lmax ¼ 340.13 nm. FT. IR (lm): (cmꢁ1):
3060 n(C–H, Ph), 2875 n(H–C]N), 1586, 1490 n(C]N). 1H NMR
300 MHz, (CD3)2CO: (d/ppm, J/Hz): 7.64 (dd, 2H, C2), 7.46 (m,
4H, C30), 7.35 (t, 2H, C3), 7.27 (1H, C4), 7.22 (m, 6H, C20, C40),
7.18 (s, 1H, C]N). 13C NMR (300 MHz, (CD3)2CO): (d/ppm):
144.49 (C1), 137.08 (C10), 136.00 (C]N), 130.68 (C3), 129.36
(C30), 128.92 (C4), 126.99 (C2), 125.39 (C40), 123.16 (C20). MS-EI:
m/z ¼ 272 M+.
Found: C, 79.6; H, 5.1; N, 9.0%. C20H16N2O. UV 210 nm lmax
¼
210 nm. FT. IR (lm): (cmꢁ1): 3098 n(C–H, Ph), 1586 n(C]N),
1
1650–2000 n(Ph). H NMR 300 MHz, (CD3)2CO: (d/ppm, J/Hz):
9.45 (s, 1H, NH), 8.02 (m, 2H, C200), 7.59 (m, 2H, C40), 7.53 (m,
4H, C20, C30), 7.47 (m, 1H, C400), 7.42 (m, 2H, C300), 7.22 (m, 2H,
C3000), 7.16 (m, 2H, C2000), 6.92 (m, 1H, C4000). 13C NMR (300 MHz,
(CD3)2CO): (d/ppm): 190.87 (C1), 143.87 (C10), 142.01 (C1000),
139.22 (C100), 131.17 (C200), 130.27 (C30), 129.55 (C300), 129.13
(C20), 129.07 (C2), 129.00 (C40), 127.61 (C400), 121.83 (C4000),
114.34 (C3000) 113.89 (C2000). MS-EI: m/z ¼ 300 M+.
Single crystal X-ray crystallography
(E)-2-((5-(4-Nitrophenyl)furan-2-yl)methylene)-1,10-diphenyl
hydrazine (6). Red crystals; yield: 78% at 25 ꢀC, mp. 163–165 ꢀC.
Anal. calc. for C23H17N3O3 (MW ¼ 383 g molꢁ1) C, 72.1; H, 4.5;
N, 11. Found: C, 72.3; H, 4.71; N, 10.90%. UV lmax ¼ 415 nm. FT.
IR (lm): (cmꢁ1): 3119 n(C–H, Ph), 1683, 1600 n(C]N), 1667–
2000, n(Ph), 1513 na(Ph–NO2), 1221 n(]C–O), 851 n(PhNO2). 1H
NMR 300 MHz, (CD3)2CO: (d/ppm, J/Hz): 8.23 (d, 2H, C30, J ¼
8.88), 7.80 (d, 2H, C20 J ¼ 8.88), 7.46 (dd, 4H, C300), 7.22, (m, 6H,
C20, C40), 7.06 (s, 1H, C]N), 6.91 (d, 1H, C4), 6.64 (d, 1H, C3).
13C NMR (300 MHz, (CD3)2CO): (d/ppm): 153.49 (C4), 151.16
(C5), 146.14 (C2), 142.87 (C10), 135.98 (C100), 129.93 (C300), 125.06
(C200), 124.84 (C]N), 124.35 (C30), 123.75 (C20), 122.43 (C400),
111.27 (C4), 110.76 (C3). MS-EI: m/z ¼ 383 M+.
Crystals of compound 1 mounted on a glass ber were studied
with an Oxford Diffraction Gemini “A” diffractometer with a
˚
CCD area detector, with a radiation source of lCuKa ¼ 1.5418 A
using graphite-monochromatized radiation. CrysAlisPro and
CrysAlis RED soware packages25 were used for data collection
and data integration. A dataset consisted of 1190/19 frames per
run of intensity data collected with a frame width of 1ꢀ in u, a
counting time of 1.0 to 2.8 s per frame, and a crystal-to-
detector distance of 55.00 mm. The double pass method of
scanning was used to exclude any noise. The collected
frames were integrated by using an orientation matrix deter-
mined from the narrow frame scans. Final cell constants were
determined by a global renement; collected data were cor-
rected for absorbance by using analytical numeric absorption
correction26 using a multifaceted crystal model based on
expressions upon the Laue symmetry using equivalent
reections.
(E)-2-(4-Nitrobenzylidene)-1,10-diphenylhydrazine (7). Yellow
crystals, yield: 93% at 25 ꢀC, mp. 120–122 ꢀC. Anal. calc. for
C
19H15N3O2 (MW ¼ 317 g molꢁ1) C, 71.9; H, 4.8; N, 10.3. Found:
C, 72.1; H, 4.56; N, 12.93%. UV lmax ¼ 411.51 nm. FT IR (lm):
1
(cmꢁ1): 3031 n(C–H), 1591, 1556 n(C]N), 1508 n(Ph–NO2). H
Structure solution and renement were carried out with the
program(s): SHELXS97;27 SHELXL97; for molecular graphics:
ORTEP-3 for Windows;28 and the soware used to prepare the
material for publication: WinGX 1.80.05.29
NMR (400 MHz, (CD3)2CO: (d/ppm): 8.19 (m, 2H, C3), 7.87 (m,
2H, C6), 7.49 (m, 4H, C30), 7.25 (m, 7H, C20, C40, C]N). 13C NMR
400 MHz, (CD3)2CO): (d/ppm): 143.02 (C4), 143.01 (C10), 142.80
994 | Med. Chem. Commun., 2014, 5, 989–996
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Full-matrix least-squares renement was carried out by
Notes and references
2
2 2
minimizing (Fo ꢁ Fc ) . All non-hydrogen atoms were rened
anisotropically; the H atoms of the amine group (H–N) were
located in a difference map and rened isotropically with Uiso
(H) ¼ 1.2 Ueq. H atoms attached to C atoms were placed in
geometrically idealized positions and rened as riding on their
parent atoms, with C–H ¼ 0.95 A ꢀ and with Uiso (H) ¼ 1.2 Ueq (C)
for aromatic groups. Crystal data and experimental details of
the structure determination are listed in Table 1.
The crystallographic data for the structure reported in this
paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no. CCDC-
986296.
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Acknowledgements
The authors thank VIEP-BUAP (CAVB-NAT-G13 and MELR-NAT-
G13), CONACyT (130500, 179119, and 194130), UNAM-PAPIIT
(217613) and UNAM-PAIP (3590-19) for nancial support. YTM
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This journal is © The Royal Society of Chemistry 2014
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996 | Med. Chem. Commun., 2014, 5, 989–996
This journal is © The Royal Society of Chemistry 2014