Synthesis and antitubercular activity of 3-aryl substituted-2-(1H(2H) benzotriazol-1(2)-yl)acrylonitriles

Article abstract of DOI:10.1016/S0223-5234(00)00144-6

A series of 223-aryl substituted-2-(1H(2H)-benzotriazol-1(2)- yl)acrylonitriles was synthesized for a preliminary in vitro evaluation of antitubercular activity according to an international program with the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF). This work reports the synthetic approach and analytical and spectroscopic characterization (UV, IR, ¹H- and ¹³C-NMR) of all compounds synthesized. Several compounds showed an interesting activity in the preliminary screening with a percent growth inhibition of the virulent Mycobacterium tuberculosis between 40 and 99% at the concentration of 12.5 μg/mL. The most effective derivatives E-5a and E-5e were also tested against M. avium in vitro. (C) 2000 Editions scientifiques et medicales Elsevier SAS.

Full text of DOI:10.1016/S0223-5234(00)00144-6

Eur. J. Med. Chem. 35 (2000) 535−543
© 2000 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
S0223523400001446/SCO
535
Short communication
Synthesis and antitubercular activity of 3-aryl substituted-2-(1H(2H)
benzotriazol-1(2)-yl)acrylonitriles#
Paolo Sanna*, Antonio Carta, Mohammad E. Rahbar Nikookar
Dipartimento Farmaco-Chimico-Tossicologico, via Muroni 23/a, 07100 Sassari, Italy
Received 23 July 1999; revised 29 November 1999; accepted 2 December 1999
Abstract – A series of 22 3-aryl substituted-2-(1H(2H)-benzotriazol-1(2)-yl)acrylonitriles was synthesized for a preliminary in vitro
evaluation of antitubercular activity according to an international program with the Tuberculosis Antimicrobial Acquisition & Coordinating
1
Facility (TAACF). This work reports the synthetic approach and analytical and spectroscopic characterization (UV, IR, H- and 13C-NMR)
of all compounds synthesized. Several compounds showed an interesting activity in the preliminary screening with a percent growth inhibition
of the virulent Mycobacterium tuberculosis between 40 and 99% at the concentration of 12.5 µg/mL. The most effective derivatives E-5a and
E-5e were also tested against M. avium in vitro. © 2000 Éditions scientifiques et médicales Elsevier SAS
antimycobacterial activity / 3-aryl substituted-2-(1H(2H)-benzotriazol-1(2)-yl)acrylonitriles / Knoevenagel condensation
1. Introduction
drugs of choice in the therapy of tuberculosis [4].
However the protracted use in time of these molecules
represents the main cause of outbreak of new resistant
strains. Therefore, there is an urgent need for the devel-
opment of new drugs having a mechanism different from
those mentioned above. Unfortunately, at present, with
the exception of rifampicin, little is known about the
mechanism of action and the structure–activity relation-
ship of these drugs and that represents an important
obstruction to a rational approach of the research in this
field. In spite of these difficulties, the numerous reports in
the literature of the last years on this matter give in
evidence the renewed interest of researchers for antitu-
bercular agents. Among a large amount of molecules
tested for this purpose the heterocycles benzofurane [5],
benzothiazole [6, 7], benzoisothiazole [8] and benzimi-
dazole [9–11] have to be cited for their interesting and
promising results. Thus, with this in mind we have taken
into account the bioisosteric replacement of those hetero-
cycles with a benzotriazole ring, as a part of our continu-
ous interest for both chemical [12–15] and biological
properties [16–19] of this heterocycle. For this project,
developed in agreement with an international program
with the Tuberculosis Antimicrobial Acquisition & Coor-
dinating Facility (TAACF), we designed a series of 3-aryl
Tuberculosis today still represents one of the major
problems for public health world-wide. After a long
period in which it seemed to be declining, in the last two
decades an unexpected return has been recorded for this
disease [1, 2]. This resurgence affected both in develop-
ing countries, where infection is endemic, and industri-
alized countries. In particular, it is generally well ac-
cepted that factors which determined the return of
tuberculosis in industrialized countries are: the migrant
flow from low income countries, the diffusion of HIV
infection and the development of multidrug-resistance of
Mycobacterium strains. The World Health Organization
has estimated that every year about eight million new
cases of tuberculosis occur and up to three million
individuals die due to this disease [3]. Isoniazid, pyrazin-
amide, ethambutol, rifampicin and streptomycin, gener-
ally used in combination among them, are still today the
#
Part of this work was presented as a poster communication at
the 2nd European Symposium on Antimicrobial Agents, Hradec
Kralove, Czech Republic, 1–4 July 1998.
* Correspondence and reprints: psanna@ssmain.uniss.it

536
In this paper we report the preparation of compounds
5a–i and 6a–i (figure 2) which represent the first part of
this project in which we considered preliminarily the
characterization of the best substituents connected with
the aryl moiety. For this purpose the nature of R was
selected within groups with various electron-accepting or
donor properties and lipophilic–hydrophilic balance. In
particular the electronegative substituents F, Cl, Br and
the most electron-withdrawing NO2 and CF3 groups were
compared either with unsubstituted terms or with those
bearing electron-releasing groups such as CH3 and NH2.
Finally, a COOH group was also introduced which
possesses both electron-withdrawing and hydrophilic
properties. On the whole the structural features of these
compounds allowed us a preliminary evaluation of the
structure–activity relationship.
Figure 1. 3-aryl derivatives of 2-(1H(2H)-benzotriazol-1(2)-
yl)acrylonitriles.
derivatives of 2-(1H(2H)-benzotriazol-1(2)-yl)acrylo-
nitriles of figure 1 which were tested at the Southern
Research Institute, GWL Hansen’s Disease Center, Colo-
rado (USA), against Mycobacterium tuberculosis in order
to discover a new lead for the development of a new class
of antitubercular agents.
Figure 2. (i) TEA/toluene/reflux, (ii) Na/ethanol/reflux, (iii) piperidine/toluene/reflux, (iv) Fe/H+.

537
2. Chemistry
tion maximum in the range 289–422 nm while isomers
E-5a–i exhibited two absorption maxima ranging be-
tween 388–317 and 293–254 nm, in accordance with
previous reports for similar cases [24]. An analogous
bathochromic effect (30–60 nm) was also observed in
two series of derivatives for the E-isomers compared to
the Z-isomers.
The desired compounds 5a–h and 6a–h were synthe-
sized according to the sequence of reactions depicted in
figure 2, by Knoevenagel condensation of the appropriate
2-(1H-benzotriazol-1-yl)- 2 or 2-(2H-benzotriazol-2-
yl)acetonitrile 3 with the suitable para-substituted benz-
aldehyde 4a–h in refluxing toluene, using triethylamine
(TEA) as basic catalyst.
3. Pharmacology
This approach represents a straightforward method for
preparation of these compounds, taking advantage of the
acidic character of the methylene group of the interme-
diate 2 or 3, activated by both cyano group and benzot-
riazolyl moiety. Formation of these acrylonitriles is very
critical where different basic catalysts are used. The
reaction conditions have been optimized by us in the case
of preparation of compounds 5a and 6a and the procedure
was then extended to all compounds. Thus, we observed
that when sodium in ethanol was used in the reaction of
2 with 4a the only known 2-(1H-benzotriazol-1-yl)acetic
acid 7 [20] was isolated, while when the same conden-
sation was carried out in toluene in the presence of
piperidine, afforded compounds 5a and 6a in lower
yields. Although from the Knoevenagel condensation two
geometric isomers may be obtained, we observed that in
most cases the E-isomer was the only one formed, while
in a few cases a mixture of E/Z-isomers was obtained.
The amines E-5i and E-6i were prepared by reduction of
the parent nitro-derivatives E-5h and E-6h, respectively.
The intermediates 2 and 3 were known and have been
prepared by condensation of the chloroacetonitrile with
1H-benzotriazole 1 in DMF at reflux in the presence of
triethylamine, modifying the method previously described
by Danan et al. [21].
All described compounds were tested in vitro for their
antitubercular activity at the GWL Hansen’s Disease
Center (Colorado State University) within the Tubercu-
losis Antimicrobial Acquisition & Coordinating Facility
(TAACF) screening program for the discovery of novel
drugs for treatment of tuberculosis. The purpose of the
screening program is to provide a resource whereby new
experimental compounds can be tested for their capacity
to inhibit the growth of virulent M. tuberculosis.
4. Results
Results of the in vitro evaluation of antitubercular
activity are reported in table I and they show an interest-
ing activity for several compounds. Compounds E-5a,
E-5b, E-5d, E-5e, E-5f, E-5h, Z-5h, E-6a and E-6h
exhibited a growth inhibition against M. tuberculosis at a
concentration of 12.5 µg/mL in the range 40–99%. These
data were compared with those of rifampicin, as reference
drug, that showed an inhibition activity of 98% at a
concentration of 0.25 µg/mL. Compounds E-5a and E-5e,
which exhibited a growth inhibition greater than 90%
were selected for confirmatory and advanced screening in
order to determine the actual MIC and their activity
against the opportunistic pathogen M. avium in compari-
son with clarithromycin. Results of the latter tests are
reported in table II.
These data show, for the phenyl derivative E-5a, an
actual MIC = 6.25 µg/mL (IC50 = 2 µg/mL), while the
4-bromophenyl derivative E-5e exhibited an MIC =
12.5 µg/mL. Results of the primary screening against
M. avium demonstrated a low activity for compound E-5a
(growth inhibition of 30% at a concentration of 12.5 µg/
mL), while compound E-5e resulted the most interesting
having an inhibitory activity of 93% at the same concen-
tration.
Separation of the isomeric mixtures was performed by
column chromatography and the structures to the single
1
isomers were assigned on the basis of their UV, H- and
13C-NMR spectra. In particular, by using the ‘gate
decoupling’ technique a 13C–H coupling was evidenced
for vinylic-H with the nitrilic-C and, according to the data
of the literature [22, 23], the E-isomers showed high
3
values of JC–H constants (12–13 Hz) while those of the
Z-isomers were much lower (0–6 Hz). Moreover, we
observed that the vinylic-H in 1H-benzotriazol-1-yl-
derivatives E-5a–i resonates as a singlet at higher field (δ
8.38–7.65) in comparison with that of 2H-benzotriazol-
2-yl derivatives E-6a–i (δ 8.83–8.38). Furthermore, we
also observed, within the E/Z isomeric pairs of two series
of compounds, that the vinylic-H of the E-isomers
exhibited a down-field shift (δ 8.81–7.65) compared to
the Z-isomers (δ 7.60–6.03). In addition, the UV spectra
in ethanol of compounds E-6a–i showed a single absorp-
5. Discussion
In spite of the restricted number of compounds tested
in this first study, some preliminary considerations of

538
Table I. In vitro evaluation of antitubercular activity as % growth inhibition at 12.5 µg/mL concentration (rifampicin MIC = 0.25 µg/mL)
versus Mycobacterium tuberculosis.
Compound
MIC (µg/mL)
% inhibition
Compound
MIC (µg/mL)
% inhibition
E-5a
E-5b
E-5c
E-5d
E-5e
E-5f
E-5g
E-5h
Z-5h
E-5i
< 12.5
> 12.5
> 12.5
> 12.5
< 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
98
55
5
86
99
82
0
43
49
33
E-6a
E-6b
E-6c
E-6d
E-6e
E-6f
E-6g
E-6h
Z-6h
E-6i
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
> 12.5
76
31
0
12
6
17
6
67
31
28
structure–activity relationships can be put forward. From
analysis of the data reported in table I, it can be generally
deduced that 1-substituted benzotriazole derivatives 5
resulted more active than the 2-benzotriazolyl isomers 6,
with the only exception for the compound E-6h. At the
present stage of research no deduction can be advanced
about the influence of the geometric isomerism (E/Z) on
the biological activity owing to the exiguousness of the
Z-isomers obtained and tested. The effect of substituents
present in the phenyl moiety were observed within each
series of all substituted derivatives which resulted less
active than the unsubstituted terms (E-5a and E-6a) with
the exception of E-5e, which in turn exhibited the highest
antimycobacterial activity in vitro and also demonstrated
a good activity against M. avium. Furthermore, the data of
biological activity seem to show that a balance between
both lipophilic and electronegative effects of the substitu-
ent in the phenyl moiety is necessary to determine an
appreciable antimycobacterial activity. That appears evi-
dent from results of compounds E-5d, E-5e and E-5f
containing a Cl, Br or CF3 group respectively. In fact
when R is represented by both a hydrophilic electron-
withdrawing group (COOH, NO2) or an electron-releasing
group with both lipophilic (CH3) and hydrophilic (NH2)
properties, the activity resulted lower than that of the
unsubstituted terms E-5a and E-6a. In the light of the
above results we can conclude that the benzotriazole
appears to be a useful substrate for antitubercular agents.
6. Experimental protocols
6.1. Chemistry
Melting points were determined in open capillaries in a
Digital Electrothermal IA9100 melting point apparatus
and are uncorrected. IR spectra were recorded as nujol
mulls with a Perkin-Elmer 781 spectrophotometer. UV
spectra are qualitative and were recorded in nm for
solutions in ethanol with a Perkin-Elmer Lambda 5
spectrophotometer. Nuclear magnetic resonance (1H- and
13C-NMR) spectra were obtained with a Varian XL-200
1
instrument (200 MHz for H- and 50 MHz for 13C-),
using TMS as internal standard. Chemical shift values are
reported in ppm (δ) and coupling constants (J) in hertz
(Hz). Signal multiplicities are represented by: s (singlet),
d (doublet), dd (double doublet), t (triplet), q (quadru-
plet), m (multiplet), and br s (broad singlet). MS spectra
were performed on a combined HP 5790-HP 5970 GC/MS
apparatus. Silica gel 60 (Merck 70–230 and 230–400
mesh silica gel) was used for column chromatography.
The progress of the reactions and the purity of the final
compounds was monitored by TLC using Merck F-254
commercial plates. Elemental analyses were performed
by the Laboratorio di Microanalisi, Dipartimento di
Scienze Farmaceutiche, Università di Padova (Padua).
The analytical results for C, H, N, and halogen, when
present, were within ± 0.4% of the theoretical values.
Table II. Actual MIC against Mycobacterium tuberculosis (rifam-
picin) and % growth inhibition against M. avium (clarithromycin)
of compounds E-5a and E-5e.
Compound
Actual MIC against % inhibition against
M. tuberculosis (µg/ M. avium at 12.5 µg/
mL)
mL
E-5a
E-5e
Rifampicin
Clarithromycin
6.25
12.5
0.125
–
30
93
–
98*
* Determined at 2 µg/mL.

539
6.1.1. 2-(1H-Benzotriazol-1-yl)acetonitrile 2
and 2-(2H-benzotriazol-2-yl)acetonitrile 3
(0.71 g, 8.0 mmol) and piperidine (0.68 g, 18 mmol) in
toluene (30 mL) after reflux for 8 h and purification by
column chromatography on silica gel (eluent: diethyl
ether–light petroleum 8:2) of the residue obtained from
evaporation of the solvent.
To a stirred solution of benzotriazole (Aldrich) (10.0 g,
84 mmol) and triethylamine (9.46 g, 93 mmol) in DMF
(30 mL), chloroacetonitrile (9.54 g, 126 mmol) was slowly
added dropwise. After the addition was complete, the
reaction mixture was stirred at 110 °C for 12 h and then
allowed to reach room temperature. The resulting precipi-
tate of triethylamine hydrochloride was filtered off and
the filtrate evaporated to dryness under reduced pressure.
The resulting residue was taken up with diethyl ether and
washed twice with water. The organic layer was then
dried (Na2SO4), evaporated and the solid residue ob-
tained flash chromatographed on silica gel (eluent: di-
ethyl ether–light petroleum 8:2) affording in sequence:
2-(2H-benzotriazol-2-yl)acetonitrile 3 (2.64 g, 20%), m.p.
78–79 °C (literature [21]: m.p. 78 °C), a 1:1 mixture of
isomers 2 and 3 (0.33 g, 2.5%) and then 2-(1H-
benzotriazol-1-yl)acetonitrile 2 (9.54 g, 71.9%), m.p.
86–87 °C (literature [21]: m.p. 87 °C).
6.1.2.2. E-2-(2H-Benzotriazol-
2-yl)-3-phenylacrylonitrile E-6a
Method A: starting from 3 (1 g, 6.3 mmol) and 4a
(1.29 g, 12.2 mmol) after 15 h under reflux and crystalli-
zation from acetone compound E-6a was obtained in 84%
yield (1.30 g); m.p. 152–153 °C; IR (cm–1): 2 230 (CN),
1 625, 1 590, 1 555; UV (nm): λmax 339, 276, 264, 222;
1H-NMR (CDCl3): δ 8.53 (s, 1H, vinylic-H), 8.02–7.90
(m, 4H, H-4 + H-7 + H-2′ + H-6′), 7.56–7.45 (m, 5H, H-5
+ H-6 + H-3′ + H-4′ + H-5′); 13C-NMR (CDCl3): δ
144.98 (s), 137.11 (d), 131.89 (d), 130.22 (s), 129.91 (d,
2 CH), 129.28 (d, 2 CH), 128.15 (d, 2 CH), 127.86 (s),
118.23 (d, 2 CH), 112.93 (s, CN), 112.17 (s); MS m/z 246
(M+). Anal. C15H10N4 (C, H, N).
Method B: the title compound was also obtained in
39% yield (0.60 g) starting from 3 (1 g, 6.3 mmol), 4a
(0.71 g, 8.0 mmol) and piperidine (0.68 g, 18 mmol) in
toluene (30 mL) after reflux for 15 h and purification by
column chromatography on silica gel (eluent: diethyl
ether–light petroleum 7:3) of the residue obtained from
evaporation of the solvent.
6.1.2. General procedure for preparation
of 2-(1H-benzotriazol-1-yl)-3-arylacrylonitriles 5a–h
and 2-(2H-benzotriazol-2-yl)-3-arylacrylonitriles 6a–h
A mixture of 2 or 3 (6.3–12.6 mmol) and triethylamine
(18.9–37.8 mmol) in toluene (25–30 mL) was stirred at
room temperature for 20 min. Then a solution of the
appropriate arylaldheyde 4a–h (8–16 mmol) in toluene
(10 mL) was slowly added and the reaction mixture was
heated under reflux for the time indicated below. After
removal of the solvent, the solid crude residue was
purified according to the indications described below.
6.1.2.3. (E/Z)-2-(1H-Benzotriazol-1-yl)-
3-(4-methylphenyl) acrylonitrile E-5b and Z-5b
Starting
from
2
(2 g,
12.6 mmol)
and
4-methylbenzaldheyde 4b (1.48 g, 25.2 mmol) after 20 h
under reflux, by trituration of the crude reaction residue
with diethyl ether, compound E-5b was obtained in
19.6% yield (0.64 g,); m.p. 98–100 °C; IR (cm–1): 2 220
(CN), 1 600, 1 580; UV (nm): λmax 324, 292, 231, 205;
1H-NMR (CDCl3): δ 8.14 (d, 1H, J = 8.4, H-4), 7.89 (s,
1H, vinylic-H), 7.91 (d, 1H, J = 8.4, H-7), 7.84 (d, 2H,
J = 8.2, H-2′ + H-6′), 7.63 (dd, 1H, J = 7.4 and 1.2, H-6),
7.49 (dd, 1H, J = 7.4 and 1.2, H-5), 7.34 (d, 2H, J = 8.2,
H-3′ + H-5′), 2.45 (s, 3H, CH3); 13C-NMR (DMSO-d6):
δ 145.32 (s), 142.25 (s), 141.20 (d), 131.46 (s), 129.71 (d,
2 CH), 129.51 (d, 2 CH), 129.14 (d), 127.73 (s), 125.18
(d), 119.87 (d), 114.10 (s, 3JC–H = 12.3, CN), 110.85 (d),
105.03 (s), 21.09 (t); MS m/z 260 (M+). Anal. C16H12N4
(C, H, N).
Chromatography of the residue obtained from evapo-
ration of the ethereal mother liquors (eluent: diethyl
ether–light petroleum 7:3) afforded a further amount of
E-5b (0.4 g, 12.2%) accompanied with compound Z-5b
(0.07 g, 2.1%) as white needles with m.p. 152–153 °C; IR
(cm–1): 2 225 (CN), 1 630, 1 610; UV (nm): λmax 302 infl,
6.1.2.1. E-2-(1H-Benzotriazol-
1-yl)-3-phenylacrylonitrile E-5a
Method A: the title compound was obtained in 60%
yield (0.93 g) after purification by chromatography (elu-
ent: mixtures of diethyl ether–light petroleum from 1:1 to
7:3 ratio), starting from 2 (1 g, 6.3 mmol) and benzalde-
hyde 4a (0.85 g, 8 mmol) after 8 h under reflux. M.p.
112–114 °C; IR (cm–1): 2 260 (CN), 1 640, 1 600, 1 570;
UV (nm): λmax 317, 285, 222 sh, 208; 1H-NMR (CDCl3):
δ 8.16 (d, 1H, J = 8.4, H-4), 7.96 (s, 1H, vinylic-H),
8.00–7.91 (m, 3H, H-7 + H-2′ + H-6′), 7.65 (dd, 1H, J =
7.4 and 1.2, H-6), 7.60–7.45 (m, 3H, H-3′ + H-4′ + H-5′),
7.50 (dd, 1H, J = 7.4 and 1.2, H-5); 13C-NMR (CDCl3):
δ 146.31 (s), 140.51 (d), 131.94 (d), 131.65 (s), 130.44
(s), 129.61 (d, 2 CH), 129.32 (d, 2 CH), 129.11 (d),
125.08 (d), 120.64 (d), 113.55 (s, CN), 110.21 (d), 106.54
(s); MS m/z 246 (M+). Anal. C15H10N4 (C, H, N).
Method B: the title compound was also obtained in
25% yield (0.39 g) starting from 2 (1 g, 6.3 mmol), 4a

540
293, 264 infl, 230, 207; 1H-NMR (CDCl3): δ 8.17 (d, 1H,
J = 7.4, H-4), 7.60 (s, 1H, vinylic-H), 7.55–7.46 (m, 2H,
H-5 + H-6), 7.36 (d, 1H, J = 7.4, H-7), 7.00 (d, 2H, J =
7.4, H-2′ + H-6′), 6.75 (d, 2H, J = 7.4, H-3′ + H-5′), 2.27
(s, 3H, CH3); 13C-NMR (DMSO-d6): δ 145.66 (s),
145.03 (s), 142.62 (d), 131.46 (s), 129.95 (d, 2 CH),
129.61 (d, 2 CH), 129.56 (d), 127.77 (s), 125.35 (d),
223, 202; 1H-NMR (CDCl3 + DMSO-d6): δ 8.63 (s, 1H,
vinylic-H), 8.08 (dd, 4H, J = 8.8 and 5.4, H-2′ + H-6′),
7.96–7.90 (m, 2H, H-4 + H-7), 7.54–7.46 (m, 2H, H-5 +
H-6), 7.31 (dd, 2H, J = 8.8 and 8.6, H-3′ + H-5′);
13C-NMR (DMSO-d6): δ 166.38 (s), 161.37 (s), 144.32
(s), 136.83 (d), 132.64 (d), 132.46 (d), 128.53 (d, 2 CH),
128.37 (s), 126.90 (s), 118.04 (d, 2 CH), 116.76 (d),
116.32 (d), 113.03 (s, CN); MS m/z 264 (M+). Anal.
C15H9FN4 (C, H, N, F).
3
120.07 (d), 115.70 (s, JC–H = 6.0, CN), 110.16 (d),
103.88 (s), 20.94 (t); MS m/z 260 (M+). Anal. C16H12N4
(C, H, N).
6.1.2.7. E-2-(1H-Benzotriazol-1-yl)-
6.1.2.4. E-2-(2H-Benzotriazol-2-yl)-
3-(4-methylphenyl)acrylonitrile E-6b
3-(4-chlorophenyl)acrylonitrile E-5d
This compound was prepared in 54.5% yield (2.24 g)
from 2 (2.5 g, 15.8 mmol) and 4-chlorobenzaldheyde 4d
(2.5 g, 17.8 mmol) after reflux for 20 h and purification
by column chromatography (eluent: diethyl ether–light
petroleum 3:7) of the reaction residue; m.p. 145–146 °C
(from acetone); IR (cm–1): 2 230 (CN), 1 610, 1 590; UV
(nm): λmax 324, 289, 229, 205; 1H-NMR (CDCl3): δ 8.16
(d, 1H, J = 8.4, H-4), 7.95 (d, 1H, J = 8.4, H-7), 7.94 (s,
1H, vinylic-H), 7.88 (d, 2H, J = 8.6, H-2′ + H-6′), 7.66
(dd, 1H, J = 8.2 and 1.2, H-6), 7.52 (d, 2H, J = 8.6, H-3′
+ H-5′), 7.47 (dd, 1H, J = 8.2 and 1.2, H-5); 13C-NMR
(DMSO-d6): δ 145.39 (s), 139.06 (d), 136.28 (s), 131.33
(s), 131.17 (d, 2 CH), 129.53 (s), 129.29 (d), 129.24 (d, 2
CH), 125.36 (d), 119.94 (d), 113.68 (s, CN), 111.08 (d),
106.95 (s); MS m/z 280 (M+). Anal. C15H9ClN4 (C, H, N,
Cl).
This compound was prepared in 89% yield (0.73 g)
starting from 3 (0.5 g, 3.1 mmol) and 4b (2.27 g,
18.9 mmol) after refluxing for 8 h and cooling at room
temperature; m.p. 182–184 °C; IR (cm–1): 2 220 (CN),
1 580, 1 550; UV (nm): λmax 346, 279, 235, 225, 203;
1H-NMR (CDCl3): δ 8.47 (s, 1H, vinylic-H), 8.00–7.80
(m, 4H, H-4 + H-7 + H-2′ + H-6′), 7.47–7.42 (m, 2H, H-5
+ H-6), 7.32 (d, 2H, J = 8.2, H-3′ + H-5′), 2.44 (s, 3H,
CH3). 13C-NMR (DMSO-d6): δ 144.56 (s), 142.82 (s),
138.00 (d), 130.01 (d, 2 CH), 129.95 (d, 2 CH), 128.40
(d, 2 CH), 127.62 (s), 118.03 (d, 2 CH), 117.91 (s),
113.13 (s, CN), 110.87 (s), 20.93 (t); MS m/z 260 (M+).
Anal. C16H12N4 (C, H, N).
6.1.2.5. E-2-(1H-Benzotriazol-1-yl)-
3-(4-fluorophenyl)acrylonitrile E-5c
This compound was obtained in 67.9% yield (2.26 g)
6.1.2.8. E-2-(2H-Benzotriazol-2-yl)-
3-(4-chlorophenyl)acrylonitrile E-6d
starting from
2
(2 g, 12.6 mmol) and 4-fluoro-
benzaldheyde 4c (1.17 g, 9.45 mmol), refluxing for 48 h.
An additional amount of 4c (1.17 g, 9.45 mmol) was
added after 24 h. The crude reaction residue was purified
by crystallization from acetone; m.p. 180–181 °C; IR
(cm–1): 2 230 (CN), 1 640, 1 600, 1 510; UV (nm): λmax
Starting from 3 (2.5 g, 15.8 mmol) and 4d (2.5 g,
17.8 mmol) after reflux for 20 h and crystallization from
acetone of the crude reaction residue, the title compound
was obtained in 59% yield (2.03 g); m.p. 152–154 °C; IR
(cm–1): 2 240 (CN), 1 590, 1 580; UV (nm): λmax 343,
280, 233, 202; 1H-NMR (CDCl3): δ 8.47 (s, 1H, vinylic-
H), 7.94–7.89 (m, 4H, H-4 + H-7 + H-2′ + H-6′),
7.54–7.43 (m, 4H, H-5 + H-6 + H-3′ + H-5′); 13C-NMR
(CDCl3): δ 145.05 (s), 138.03 (s), 135.44 (d), 131.08 (s),
131.03 (d, 2 CH), 129.62 (d, 2 CH), 128.70 (s), 128.26 (d,
2 CH), 118.24 (d, 2 CH), 112.68 (s, CN), 112.22 (s); MS
m/z 280 (M+). Anal. C15H9ClN4 (C, H, N, Cl).
1
319, 285, 227, 204; H-NMR (CDCl3): δ 8.15 (d, 1H, J
= 8.4, H-4), 7.99–7.90 (m, 3H, H-7 + H-2′ + H-6′), 7.93
(s, 1H, vinylic-H), 7.65 (dd, 1H, J = 8.2 and 1.2, H-6),
7.50 (dd, 1H, J = 8.2 and 1.2, H-5), 7.26 (dd, 2H, J = 8.8
and 8.4, H-3′ + H-5′); 13C-NMR (CDCl3 + DMSO-d6): δ
164.55 (s), 159.54 (s), 143.69 (s), 137.88 (d), 130.45 (d),
130.27 (d), 129.67 (s), 127.39 (d), 125.31 (s), 123.43 (d),
116.17 (d), 114.77 (d), 114.32 (d), 111.98 (s, CN), 109.04
(d); MS m/z 264 (M+). Anal. C15H9FN4 (C, H, N, F).
6.1.2.9. E-2-(1H-Benzotriazol-1-yl)-
3-(4-bromophenyl)acrylonitrile E-5e
6.1.2.6. E-2-(2H-Benzotriazol-2-yl)-
3-(4-fluorophenyl)acrylonitrile E-6c
In the same manner for E-5c, the title compound was
obtained in 75% yield (1.25 g) after crystallization from
diethyl ether starting from 3 (1 g, 6.3 mmol) and 4c
(1.17 g, 9.5 mmol); m.p. 195–196 °C; IR (cm–1): 2 230
(CN), 1 610, 1 600, 1 550; UV (nm): λmax 339, 277, 268,
This compound was prepared in 51.6% yield (2.1 g)
from 2 (2 g, 12.6 mmol) and 4-bromobenzaldehyde 4e
(2.33 g, 12.6 mmol) after reflux for 30 h and purification
by column chromatography on silica gel (eluent: diethyl
ether–light petroleum 7:3) of the crude reaction residue;
m.p. 130–131 °C (from diethyl ether); IR (cm–1): 2 230
(CN), 1 590, 1 480; UV (nm): λmax 325, 290, 229, 203;

541
1H-NMR (DMSO-d6): δ 8.16 (d, 1H, J = 8.4, H-4), 7.95
(d, 1H, J = 8.4, H-7), 7.92 (s, 1H, vinylic-H), 7.80 (d, 2H,
J = 8.6, H-2′ + H-6′), 7.68 (d, 2H, J = 8.6, H-3′ + H-5′),
7.64 (dd, 1H, J = 8.2 and 1.8, H-6), 7.51 (dd, 1H, J = 8.2
and 1.8, H-5); 13C-NMR (CDCl3): δ 146.33 (s), 138.55
(d), 132.62 (d, 2 CH), 131.48 (s), 130.83 (d, 2 CH),
129.33 (s), 129.21 (d), 126.46 (s), 125.16 (d), 120.67 (d),
113.26 (s, CN), 110.18 (d), 107.09 (s); MS m/z 325 (M+).
Anal. C15H9BrN4 (C, H, N, Br).
110–112 °C; IR (cm–1): 2 230 (CN), 1 635; UV (nm):
λmax 270, 206; 1H-NMR (CDCl3): δ 8.21 (d, 1H, J = 8.2,
H-4), 7.74 (d, 2H, J = 8.2, H-2′ + H-6′), 7.60–7.46 (m,
2H, H-5 + H-6), 7.44 (d, 2H, J = 8.2, H-3′ + H-5′), 7.04
(d, 1H, J = 8.2, H-7), 6.03 (s, 1H, vinylic-H); 13C-NMR
(CDCl3): δ 150.02 (s), 135.74 (s), 134.42 (s), 133.76 (s),
132.26 (s), 131.47 (s), 129.18 (d), 128.26 (d, 2 CH),
126.41 (m, 2 CH), 125.27 (d), 120.93 (d), 114.27 (s,
3JC–H = 0.0, CN), 110.87 (d), 94.12 (d); MS m/z 314
(M+). Anal. C16H9F3N4 (C, H, N, F).
6.1.2.10. E-2-(2H-Benzotriazol-2-yl)-
3-(4-bromophenyl)acrylonitrile E-6e
6.1.2.12. E-2-(2H-Benzotriazol-2-yl)-
3-(4-trifluoromethylphenyl)acrylonitrile E-6f
In the same manner for E-5e, this compound was
prepared in 61.5% yield (1.26 g) starting from 3 (1 g,
6.3 mmol) and 4e (1.16 g, 6.3 mmol) after reflux for 22 h
and purification by flash chromatography (eluent: diethyl
ether–light petroleum 1:1) of the reaction residue; m.p.
137–138 °C (from diethyl ether); IR (cm–1): 2 240 (CN),
This compound was prepared starting from 3 (1 g,
6.3 mmol) and 4f after 28 h under reflux and chromatog-
raphy (eluent: mixtures of diethyl ether–light petroleum
from 1:1 to 7:3) of the reaction residue; E-6f (1.48 g,
75%); m.p. 126–127 °C (from diethyl ether); IR (cm–1):
2 240 (CN), 1 620, 1 570; UV (nm): λmax 331, 272, 262,
1
1 600, 1 590; UV (nm): λmax 344, 280, 235, 201; H-
1
220; H-NMR (Me2CO-d6): δ 8.81 (s, 1H, vinylic-H),
NMR (CDCl3): δ 8.63 (s, 1H, vinylic-H), 8.00–7.90 (m,
4H, H-4 + H-7 + H-2′ + H-6′), 7.72 (d, 2H, J = 8.2, H-3′
+ H-5′), 7.60–7.40 (m, 2H, H-5 + H-6); 13C-NMR
(CDCl3): δ 145.08 (s), 135.55 (d), 132.62 (d, 2 CH),
131.51 (s), 131.14 (d, 2 CH), 121.12 (s), 128.30 (d, 2
CH), 126.54 (s), 118.59 (s), 118.26 (d, 2 CH), 112.70 (s,
CN); MS m/z 325 (M+). Anal. C15H9BrN4 (C, H, N, Br).
Further elution of the column gave a small amount of
unreacted 3 (0.15 g, 15%) and 1H-benzotriazole 1 (0.16 g,
21%).
8.35 (d, 2H, J = 8.2, H-2′ + H-6′), 8.10–7.90 (m, 4H, H-4
+ H-7 + H-3′ + H-5′), 7.70–7.60 (m, 2H, H-5 + H-6);
13C-NMR (CDCl3): δ 145.18 (s), 134.73 (d, 2 CH),
133.65 (s), 133.33 (s), 132.68 (s), 129.97 (d, 2 CH),
128.54 (d, 2 CH), 126.20 (m, 2 CH), 120.76 (s), 118.33
(d, 2 CH), 114.15 (s), 112.32 (s, CN); MS m/z 314 (M+).
Anal. C16H9F3N4 (C, H, N, F).
6.1.2.13. E-2-(1H-Benzotriazol-1-yl)-
3-(4-carboxyphenyl)acrylonitrile E-5g
This compound was prepared in 19.6% yield starting
from 2 (2 g, 12.6 mmol) and 4-carboxybenzaldheyde 4g
(1.9 g, 12.6 mmol) after reflux for 20 h followed by
column chromatography (eluent: mixtures of diethyl
ether–acetone with increasing percent of acetone) of the
reaction residue. M.p. 259–260 °C (from acetone); IR
(cm–1): 3 250–3 000 (OH), 2 230 (CN), 1 700 (CO),
1 610, 1 570; UV (nm): λmax 326, 287, 224 infl, 205;
1H-NMR (DMSO-d6): δ 8.38 (s, 1H, vinylic-H), 8.25 (d,
1H, J = 8.4, H-4), 8.15–8.04 (m, 5H, H-7 + 4 phenyl H),
7.78 (dd, 1H, J = 7.4 and 1.2, H-6), 7.60 (dd, 1H, J = 7.4
and 1.2, H-5), 3.50 (br s, 1H, OH); 13C-NMR (DMSO-
d6): δ 166.66 (s, CO), 145.56 (s), 138.75 (d), 134.71 (s),
133.23 (s), 131.36 (s), 129.91 (d, 2 CH), 129.66 (d, 2
CH), 129.51 (d), 125.58 (d), 120.10 (d), 113.66 (s, CN),
111.34 (d), 108.30 (s); MS m/z 290 (M+). Anal.
C16H10N4O2 (C, H, N).
6.1.2.11. (E/Z)-2-(1H-Benzotriazol-1-yl)-
3-(4-trifluoromethylphenyl)acrylonitrile E-5f and Z-5f
These compounds were prepared starting from 2 (2 g,
12.6 mmol) and 4-trifluoromethylbenzaldehyde 4f (2.19 g,
12.6 mmol) after reflux for 48 h and purification by
chromatography on silica gel column (eluent: diethyl
ether–light petroleum 7:3). E-5f (0.62 g, 64.5%); m.p.
136–137 °C (from diethyl ether); IR (cm–1): 2 240 (CN),
1
1 610; UV (nm): λmax 320, 277, 205; H-NMR (DMSO-
d6): δ 8.16 (d, 1H, J = 8.2, H-4), 8.06 (s, 1H, vinylic-H),
8.04 (d, 2H, J = 8.4, H-2′ + H-6′), 7.97 (d, 1H, J = 8.2,
H-7), 7.80 (d, 2H, J = 8.4, H-3′ + H-5′), 7.67 (dd, 1H, J
= 8.2 and 1.8, H-6), 7.51 (dd, 1H, J = 8.2 and 1.8, H-5);
13C-NMR (CDCl3): δ 146.44 (s), 137.36 (d), 133.88 (s),
133.30 (s), 132.67 (s), 131.41 (s), 129.72 (d, 2 CH),
129.45 (d), 126.26 (m, 2 CH), 125.36 (d), 120.80 (d),
3
112.92 (s, JC–H = 12.2 CN), 110.26 (d), 108.86 (s); MS
m/z 314 (M+). Anal. C16H9F3N4 (C, H, N, F).
6.1.2.14. E-2-(2H-Benzotriazol-2-yl)-
Further elution of the column gave a mixture (0.51 g)
of isomers E-5f and Z-5f in 2:1 ratio. This recrystallized
from diethyl ether afforded an additional small amount of
E-5f (0.14 g, 3.5%) and Z-5f (0.12 g, 3%); m.p.
3-(4-carboxyphenyl)acrylonitrile E-6g
In the same manner reported for E-5g, the title com-
pound was obtained in 16.2% yield (0.59 g) starting from
3 (2 g, 12.6 mmol) and 4g (1.9 g, 12.6 mmol); m.p.

542
277–279 °C; IR (cm–1): 3 500–3 200 (OH), 2 240 (CN),
1 680 (CO), 1 610, 1 560, 1 510; UV (nm): λmax 344,
277, 228 infl, 204; H-NMR (CDCl3): δ 10.15 (br s, H,
OH), 8.64 (s, 1H, vinylic-H), 8.17 (d, 2H, J = 8.4, H-3′ +
H-5′), 8.05 (d, 2H, J = 8.4, H-2′ + H-6′), 7.95–7.85 (m,
2H, H-4 + H-7), 7.53–7.40 (m, 2H, H-5 + H-6); 13C-
NMR (DMSO-d6): δ 167.79 (s, CO), 144.37 (s), 137.00
(d), 136.85 (s), 132.98 (s), 129.80 (d, 2 CH), 129.63 (d, 2
CH), 128.65 (d, 2 CH), 127.90 (s), 118.05 (d, 2 CH),
112.80 (s, CN), 112.54 (s); MS m/z 290 (M+). Anal.
C16H10N4O2 (C, H, N).
7.57–7.52 (m, 2H, H-5 + H-6); 13C-NMR (DMSO-d6): δ
148.75 (s), 144.73 (s), 136.88 (s), 135.37 (d), 131.16 (d,
2 CH), 129.26 (d, 2 CH), 129.05 (s), 124.37 (d, 2 CH),
1
3
118.36 (d, 2 CH), 114.70 (s, JC–H = 13.3, CN), 112.71
(s); MS m/z 291 (M+). Anal. C15H9N5O2 (C, H, N).
Z-6h (0.18 g, 6.5%): m.p. 157–159 °C (from acetone);
IR (cm–1): 2 220 (CN), 1 630, 1 600, 1 530; UV (nm):
λmax 289, 260 sh, 206; 1H-NMR (CDCl3): δ 8.32 (d, 2H,
J = 8.4, H-3′ + H-5′), 8.23 (d, 1H, J = 8.2, H-4),
7.60–7.45 (m, 4H, H-5 + H-6 + H-2′ + H-6′), 7.07 (d, 1H,
J = 8.2, H-7), 6.12 (s, 1H, vinylic-H), 13C-NMR (CDCl3):
δ 149.87 (s), 149.19 (s), 146.11 (s), 138.02 (s), 132.09 (s),
129.33 (d), 128.94 (d, 2 CH), 125.42 (d), 124.47 (d, 2
CH), 120.98 (d), 114.06 (s, 3JC–H = 0.0, CN), 110.76 (d),
95.19 (d); MS m/z 291 (M+). Anal. C15H9N5O2 (C, H, N).
6.1.2.15. (E/Z)-2-(1H-Benzotriazol-1-yl)-
3-(4-nitrophenyl)acrylonitrile E-5h and Z-5h
These compounds were prepared from 2 (1 g, 6.3 mmol)
and 4-nitrobenzaldheyde 4h (1.10 g, 7.28 mmol) after
refluxing for 20 h followed by column chromatography
(eluent: diethyl ether–light petroleum 1:1). E-5h (0.79 g,
43.2%); m.p. 212–214 °C (from acetone); IR (cm–1):
2 230 (CN), 1 620, 1 595; UV (nm): λmax 332, 282, 203;
1H-NMR (DMSO-d6): δ 8.50–8.40 (m, 3H, vinylic-H +
H-3′ + H-5′), 8.30–8.20 (m, 3H, H-4 + H-2′ + H-6′), 8.16
(d, 1H, J = 8.2, H-7), 7.78 (dd, 1H, J = 8 and 1.4, H-6),
7.60 (dd, 1H, J = 8 and 1.4, H-5); 13C-NMR (DMSO-d6):
δ 148.54 (s), 145.68 (s), 142.18 (s), 137.28 (s), 136.67
(d), 131.25 (s), 130.74 (d, 2 CH), 129.65 (d), 125.75 (d),
6.1.2.17. E-2-(1H-Benzotriazol-1-yl)-
3-(4-aminophenyl)acrylonitrile E-5i
A suspension of E-5h (0.2 g, 0.69 mmol) and iron
activated powder (0.38 g, 6.8 mmol) in ethanol (15 mL)
was refluxed for 30 min when an aqueous solution of 2 N
HCl (2 mL) and 50% ethanol (10 mL) was then added
and the reflux continued for an additional 2 h. The
unchanged iron was then filtered off, thoroughly washed
with 50% ethanol solution, and the filtrate was evapo-
rated in vacuo. The crude residue recrystallized from a
2:1 diethyl ether–acetone mixture, afforded E-5i (0.14 g,
78%); m.p. 177–179 °C; IR (cm–1): 3 440 and 3 340
(NH2), 2 200 (CN), 1 650, 1 620, 1 585, 1 550, 1 530;
3
124.18 (d, 2 CH), 120.17 (d), 113.28 (s, JC–H = 12.8,
CN), 111.56 (d); MS m/z 291 (M+). Anal. C15H9N5O2 (C,
H, N).
1
UV (nm): λmax 388, 254, 203; H-NMR (DMSO-d6): δ
Z-5h (0.30 g, 16.4%) (from acetone); m.p. 158–160 °C;
IR (cm–1): 2 230 (CN), 1 630, 1 600, 1 520; UV (nm):
λmax 290, 260, 205; 1H-NMR (DMSO-d6): δ 8.34 (d, 2H,
J = 7.6, H-3′ + H-5′), 8.31 (d, 1H, J = 8.4, H-4), 7.71 (d,
2H, J = 7.6, H-2′ + H-6′), 7.69–7.50 (m, 2H, H-5 + H-6),
7.34 (d, 1H, J = 8.4, H-7), 7.18 (s, 1H, vinylic-H);
13C-NMR (DMSO-d6): δ 149.34 (s), 148.05 (s), 145.24
(s), 137.57 (s), 132.11 (s), 129.33 (d), 129.19 (d, 2 CH),
125.34 (d), 124.19 (d, 2 CH), 120.12 (d), 114.92 (s, 3JC–H
= 0.0, CN), 111.26 (d), 98.42 (d); MS m/z 291 (M+). Anal.
C15H9N5O2 (C, H, N).
8.10 (d, 1H, J = 8.4, H-4), 7.82 (d, 1H, J = 8.4, H-7), 7.76
(d, 2H, J = 8.6, H-2′ + H-6′), 7.65 (s, 1H, vinylic-H), 7.60
(d, 1H, J = 8.4, H-6), 7.52 (dd, 1H, J = 8.4 and 1.2, H-5),
6.75 (d, 2H, J = 8.6, H-3′ + H-5′), 5.72 (br s, 2H, NH2);
MS m/z 261 (M+). Anal. C15H11N5 (C, H, N).
6.1.2.18. E-2-(2H-Benzotriazol-2-yl)-
3-(4-aminophenyl)acrylonitrile E-6i
Using the same procedure described for E-5i, the title
compound was prepared in 57% yield (0.25 g) starting
from E-6h (0.5 g, 1.7 mmol); m.p. 220–222 °C; IR (cm–1):
3 450 and 3 360 (NH2), 2 220 (CN), 1 630, 1 610, 1 590,
1
6.1.2.16. (E/Z)-2-(2H-Benzotriazol-2-yl)-
3-(4-nitrophenyl)acrylonitrile E-6h and Z-6h
1 570, 1 520; UV (nm): λmax 422, 298, 255, 204; H-
NMR (CDCl3): δ 8.38 (s, 1H, vinylic-H), 7.95–7.85 (m,
2H, H-4 + H-7), 7.86 (d, 2H, J = 8.6, H-2′ + H-6′),
7.50–7.40 (m, 2H, H-5 + H-6), 6.74 (d, 2H, J = 8.6, H-3′
+ H-5′), 4.26 (br s, 2H, NH2); MS m/z 261 (M+). Anal.
C15H11N5 (C, H, N).
These compounds were prepared from 3 (1.5 g,
9.5 mmol) and 4h (2.86 g, 19 mmol) after refluxing for
4 h followed by column chromatography (eluent: diethyl
ether–light petroleum 1:1). E-6h (1.03 g, 37.3%): m.p.
224–226 °C (from acetone); IR (cm–1): 2 230 (CN),
1 590, 1 560, 1 510; UV (nm): λmax 348, 269, 210 sh,
204; 1H-NMR (CDCl3 + DMSO-d6): δ 8.83 (s, 1H,
vinylic-H), 8.40 (d, 2H, J = 8.4, H-3′ + H-5′), 8.26 (d, 2H,
J = 8.4, H-2′ + H-6′), 8.00–7.95 (m, 2H, H-4 + H-7),
6.1.2.19. 2-(1H-Benzotriazol-1-yl)acetic acid 7
A solution of 2 (2 g, 12.6 mmol) in absolute ethanol
(15 mL) was slowly added to a solution of Na (0.31 g,
13.5 mmol) in absolute ethanol (30 mL). After stirring at

543
room temperature for 15 min 4a (1.34 g, 12.6 mmol) was
added dropwise and the resulting mixture was refluxed
for 4 h. The mixture was allowed to stand at room
temperature and the formed precipitate was collected by
filtration, obtaining the known 7 as sodium salt. This was
dissolved with water and the solution was made acidic
(pH = 2–3) with 2 N hydrochloric acid aqueous solution
affording 7 (1.80 g, 80%) with m.p. 215–217 °C (litera-
ture [20]: m.p. 215–217 °C).
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