Click 1,4-regioselective synthesis, characterization, and antimicrobial screening of novel 1,2,3-triazoles tethering fluorinated 1,2,4-triazole and lipophilic side chain

Article abstract of DOI:10.1007/s11164-016-2679-4

Base-catalyzed alkylation of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (3) with one or two equivalents of propargyl bromide in presence of triethylamine as catalyst selectively produced the thiopropargylated 1,2,4-triazole 7 in 90?% yield. Un

Full text of DOI:10.1007/s11164-016-2679-4

Res Chem Intermed
DOI 10.1007/s11164-016-2679-4
Click 1,4-regioselective synthesis, characterization,
and antimicrobial screening of novel 1,2,3-triazoles
tethering fluorinated 1,2,4-triazole and lipophilic side
chain
Nadjet Rezki1,2 Mariem Mohammed Mayaba1
•
•
Fawzia Faleh Al-blewi1 Mohamed Reda Aouad1,2
El Sayed Helmi El Ashry3
•
•
Received: 29 May 2016 / Accepted: 26 July 2016
Ó Springer Science+Business Media Dordrecht 2016
Abstract Base-catalyzed alkylation of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-tria-
zole-3-thione (3) with one or two equivalents of propargyl bromide in presence of
triethylamine as catalyst selectively produced the thiopropargylated 1,2,4-triazole 7 in
90 % yield. Under the same reaction conditions, 4-ethyl-5-(4-fluorophenyl)-3-(prop-
2-yn-1-ylthio)-1,2,4-triazole (8) was produced. Conversely, when the propargylation
was carried out in presence of sodium bicarbonate, a mixture of S,N4- (24) and
S,N2-bis(propargylated) triazoles (25) was obtained in 85 % overall yield. The click
1,3-dipolar cycloaddition reaction of the mono- (7, 8) and/or bis(propargylated)-1,2,4-
triazoles (24) with a variety of long-chain alkyl azides, conducted in t-BuOH:H2O
(10:1) in presence of sodium ascorbate and copper(II) sulfate at room temperature,
afforded the regioselective 1,4-disubstituted mono- (14–18) and bis(1,2,3-triazole)
derivatives (26–30) containing a fluorinated 1,2,4-triazole moiety and a lipophilic side
chain. The structures of the new products were elucidated by infrared (IR), 1H and 13
C
nuclear magnetic resonance (NMR), and mass spectrometry. They were also assessed
in vitro for their antimicrobial potency against six bacteria (Bacillus subtilis, Strep-
tococcus pneumonia, Staphylococcus aureus, Escherichia coli, Pseudomonas
aeruginosa, and Klebsiella pneumonia) and two fungi (Aspergillus fumigatus and
Electronic supplementary material The online version of this article (doi:10.1007/s11164-016-2679-4)
contains supplementary material, which is available to authorized users.
&
Nadjet Rezki
dr.nadjetchem@gmail.com
1
2
Department of Chemistry, Faculty of Sciences, Taibah University,
PO Box 344, Al-Madinah Al-Munawarah, Saudi Arabia
´
Laboratoire de Chimie and Electrochimie des Complexes Metalliques (LCECM), Department
of Chemistry, Faculty of Sciences, University of Sciences and Technology Mohamed Boudiaf,
USTO-MB, PO Box 1505, Oran, El M’nouar, Algeria
3
Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt
123

N. Rezki et al.
Candida albicans). The bioassay results revealed that some of the tested compounds
displayed promising antimicrobial activity.
Keywords Click synthesis Á 1,2,3-Triazoles Á 1,2,4-Triazoles Á Nonionic
surfactants Á Antimicrobial activity
Introduction
In recent years, considerable effort has been focused on synthesis of nonionic
surfactants due to their relatively simple synthesis and broad applications in
biochemical research and drug delivery systems [1, 2]. They are also widely
employed in industry as detergents, solubilizers, and emulsifiers [3]. Heterocyclic
surfactants have commanded attention from many research groups around the
world; however, progress with such compounds has been limited [4].
Five-membered nitrogen-containing heterocycles, including 1,2,4-triazoles and
1,2,3-triazoles, have gained significant importance in modern heterocyclic chem-
istry, promising a wide range of medicinal applications, e.g., as antiinflammatory
[5], anti-human immunodeficiency virus (HIV) [6], anticancer [7, 8], antibacterial
[9], antifungal [10], antiviral [11], and antimalarial agents [12]. Triazole derivatives
attached to long hydrocarbon chains form nonionic surfactants, being the most
frequently used surfactants in medicinal and industrial chemistry [13].
Recently, synthesis of 1,2,3-triazoles that provide a connection between two
pharmacophores has provided an ideal opportunity for design of novel classes of
bifunctional bioactive molecules [14, 15]. In fact, there is growing interest in the
concept of so-called click chemistry for construction of five-membered nitrogen-
containing heterocycles, namely 1,2,3-triazoles, via 1,3-dipolar cycloaddition of
terminal alkynes with organoazides [16, 17]. Cu(I)-catalyzed Huisgen ligation of
azides and alkynes has been shown to be the most elegant and efficient approach for
selective preparation of the regioisomer 1,4-disubstituted 1,2,3-triazole [18, 19].
Presence of a fluorine atom in a given drug structure often dramatically increases
its thermal stability and lipophilicity, resulting in an enhanced transportation rate of
the drug to an active site [20, 21]. In addition, some fluorinated drugs bearing a
1,2,3-triazole nucleus have generated much research interest in view of their
important applications in medicinal chemistry and agrochemistry [22–25].
We describe herein the design and synthesis of a new series of regioselective
mono- and bis-1,2,3-triazoles tethering a fluorinated 1,2,4-triazole scaffold and long
alkyl side chains as novel classes of nonionic surfactants via a Cu-catalyzed azide–
alkyne cycloaddition reaction. The antimicrobial activities of the propargylated
1,2,4-triazoles and their respective 1,2,3-triazoles were also evaluated.
Results and discussion
The synthetic protocol adopted for construction of novel 1,2,3-triazole nonionic
surfactants with a 1,2,4-triazole tether linked through a flexible methylene spacer
involved Huisgen 1,3-dipolar cycloaddition of propargylated 1,2,4-triazoles and
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Click 1,4-regioselective synthesis, characterization, and…
long-chain alkyl azides. The procedure for synthesis of the key intermediate 5-(4-
fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (3) was based on a modified
literature method [26] in which the reaction of 4-fluorobenzoylchloride (1) with
thiosemicarbazide in refluxing acetone afforded the unsubstituted acylthiosemicar-
bazide 2 which was thermally cyclized to 3 in 90 % yield in presence of aqueous
NaOH (Scheme 1). Furthermore, the 4-ethyl-5-(4-fluorophenyl)-2,4-dihydro-1,2,4-
triazole-3-thione (6) was previously prepared in lower yield by initial treatment of
4-fluorobenzoylchloride (1) with ethylthiosemicarbazide to yield the corresponding
ethylthiosemicarbazide 5, followed by subsequent intramolecular ring closure in
aqueous NaHCO3 at 100 °C [27]. In the present study, synthesis of compound 6 was
achieved in higher yield (89 %) by condensation of 4-fluorobenzohydrazide (4) with
ethylisothiocyanate in refluxing ethanol to furnish the corresponding thiosemicar-
bazide 5 in 92 % yield. The latter compound was cyclized in basic medium (10 %
NaOH) to obtain the 4-ethyl-1,2,4-triazole-3-thione (Scheme 1).
The structures of the substituted triazoles 3 and 6 were established based on their
IR, 1H NMR, and 13C NMR spectra. Their IR spectra displayed the main
characteristic absorptions at 3267–3382 cm-1 (NH), 1289–1295 cm-1 (C=S), and
1610–1620 cm-1 (C=N). Moreover, proton NMR analysis confirmed the absence of
signals attributed to the NH groups of their corresponding thiosemicarbazides 2, 5
and the appearance of characteristic triazole-NH singlets at d 13.83–13.95 ppm,
thus confirming the presence of the two triazoles in thione form. The phenyl protons
resonated at their normal chemical shifts at d 7.40–7.87 ppm, and the characteristic
ethyl protons appeared as a triplet at dH 1.14 ppm and a quartet at d 4.00–4.05 ppm.
Signals related to ethyl carbons were observed at d 13.32 and 30.64 ppm in the
13C NMR spectrum of compound 6. Formation of triazoles 3 and 6 in thione form
was further confirmed by the appearance of the C=S signal at d 166.77–169.25 ppm.
The thiopropargylated triazole 7 was regioselectively prepared in satisfactory
yield (90 %) according to our reported procedures [28–30] by refluxing the triazole
3 with one equivalent of propargyl bromide in presence of triethylamine as basic
catalyst and ethanol as solvent (Scheme 2). The reaction completed in a very short
period of time (30 min) with simple workup. Under the same basic reaction
conditions (Et3N, EtOH), propargylation of the ethyltriazole 6 furnished the
corresponding 5-(4-fluorophenyl)-4-ethyl-1,2,4-triazole-3-thio(prop-2-yne) (8) in
excellent yield (88 %) (Scheme 2).
H
N
N
COR1
CONHNHCSNHR2
NH2NHCSNH2
Acetone, reflux
10% NaOH
Reflux
S
N
R
F
F
F
2 R2 = H
5 R2 =Et
1 R1 = Cl
4 R1 = NHNH2
3 R = H
6 R = Et
EtNCS
EtOH, reflux
Scheme 1 Synthesis of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thiones 3 and 6
123

N. Rezki et al.
H
N
N
N N
Br
EtOH, Et3N
S
+
C
CH
S
C
CH
N
R
N
R
F
F
7 R = H
8 R = Et
3 R = H
6 R = Et
Scheme 2 Synthesis of the thiopropargylated 1,2,4-triazoles 7 and 8
Formation of the thiopropargylated triazoles 7 and 8 was confirmed by their IR,
1H NMR, 13C NMR, and mass spectra. In the IR spectra, the sharp band at
3305–3310 cm-1 clearly indicated the presence of acetylenic hydrogen :C–H,
while the C:C group appeared as a sharp band at 2149–2154 cm-1
.
The 1H NMR spectra of compounds 7 and 8 clearly indicated successful
S-alkylation reaction via the appearance of two new singlets in the aliphatic region.
Integration of the first singlet indicated the presence of two protons which appeared
at d 4.02–4.07 ppm relative to SCH2, while the second singlet at d 3.20–3.25 ppm
possessed one proton by integration, being related to an sp-CH. In addition, the
presence of one broad singlet at d 14.53 ppm was attributed to one triazolic NH
proton, confirming formation of the mono S-propargylated triazole 7. The spectrum
of compound 8 also showed the presence of ethyl protons as a triplet and multiplet
at d 1.20 and 4.02–4.07 ppm, respectively. The four aromatic protons resonated at
their usual chemical shifts (7.38–8.04 ppm).
The 13C NMR analysis also revealed the incorporation of the propargyl residue
by the appearance of diagnostic carbon signals at d 20.41–21.85, 74.54–74.80, and
79.51–80.82 ppm, which were attributed to alkyne SCH2 and C:C groups,
respectively. The signals observed at d 115.98–164.57 ppm were associated with
aromatic and C=N carbons.
A new series of regioselective 1,4-disubstituted mono-1,2,3-triazoles 14–23
containing fluorinated 1,2,4-triazoles and lipophilic side chains were successfully
synthesized in 80–96 % yield via the Cu(I)-catalyzed click 1,3-dipolar cycloaddi-
tion reaction of 5-(4-fluorophenyl)-4H/ethyl-1,2,4-triazole-3-thio(prop-2-yne) (8, 9)
with freshly prepared azido long-chain alkyl 9–13. The reaction was conducted at
room temperature using sodium ascorbate and copper sulfate as catalysts and t-
BuOH/H2O (10:1) as solvent (Scheme 3). The azides 9–13 were prepared via a
metathesis reaction of the appropriate long-chain alkyl halides with sodium azide in
acetone–water mixture according to a reported procedure [31].
Formation of compounds 14–23 was confirmed based on their spectroscopic data
(IR, 1H NMR, 13C NMR, and mass). Their IR spectra clearly confirmed the absence
of peaks belonging to C:C at 2149–2154 cm-1 and :CH at 3305–3310 cm-1
,
1
thus confirming success of the cycloaddition reaction. The H NMR spectrum of
compound 15 revealed the disappearance of the signal attributed to :C–H proton at
d 3.20 ppm of the precursor S-alkyne 7 and the appearance of one singlet at d
8.00 ppm, which was assigned to the 1,2,3-triazole CH proton. The spectrum also
contained two pairs of singlets for the SCH2 protons at d 4.43 and 4.52 ppm at ratio
123

Click 1,4-regioselective synthesis, characterization, and…
N
N
C
CH
S
N
F
R
7 R = H
8 R = Et
CH3(CH2)nN3
9-13
i
H
N
N
N
N
S
S
N
N
(CH2)nCH3
(CH2)nCH3
+
F
F
N
N
N
N
R
N
N
14b-18b
14a-18a R = H
19-23 R = Et
i : CuSO4, Na-ascorbate, t-BuOH, H2O (10:1)
n = 9, 10, 11, 13, 15
Scheme 3 Regioselective synthesis of 1,4-disubstituted mono-1,2,3-triazoles 14–23 containing 1,2,4-
triazole and lipophilic side chains
of 2:3, and for the triazolic NH proton at d 14.16 and 14.51 ppm with the same ratio
(2:3). This pairing of signals could presumably be due to the tautomerism in 1,2,4-
triazole due to the mobility of the NH proton between the N-2 and N-4 nitrogen
atoms. Consequently, the two tautomeric forms 15a and 15b may exist in
equilibrium with predominance of form 15b. Additionally, the 13C NMR spectrum
revealed the disappearance of the two sp-carbons from their chemical shifts of 74.54
and 80.82 ppm, and the SCH2-carbon resonated at 31.74 ppm. New signals also
appeared in the aliphatic region, being assigned to the methylene and methyl
carbons. All sp2 carbons were observed in the aromatic region.
The bisalkylation on the triazole nitrogen atom depends on the ability of these
basic catalysts (Et3N, NaHCO3) to deprotonate the triazolic N–H group. In this
context, all trials attempting to prepare the S,N-bis(propargylated) triazoles by using
two equivalents of Et3N were unsuccessful. In contrast, alkylation of 3 with 2.2
equivalents of propargyl bromide in refluxing dimethylformamide (DMF) using
NaHCO3 as base for 10 h produced a mixture of S,N4- and S,N2-bis(propargy-
lated)triazoles 24 as major product, and 25 as minor product in overall yield of 85 %
(Scheme 4). These results are in accordance with those reported in our previous
work concerning regioselective dialkylation of unsubstituted 1,2,4-triazole-3-thione,
where the S,N4- and S,N2-bis(alkylated)triazoles were also formed with preferential
formation of the S,N4-isomer in high yield [28–30].
The reactions were monitored by thin-layer chromatography (TLC), where the
bis(propargylated) triazoles could be identified by their Rf values (RNf -4 [ RfN-2).
1H NMR analysis was used to differentiate between the N-2 and N-4 isomers,
where the –CH2-N2 protons should be deshielded relative to the –CH2-N4 protons.
123

N. Rezki et al.
H
C
CH
C
N
N
N
N
N
N
Br
C
CH
C
CH
S
S
S
N
N
N
+
F
DMF, NaHCO3
F
F
CH
H
C
CH
24
Scheme 4 Synthesis of S,N4- and S,N2-bis(propargylated) triazoles 24 and 25
25
3
Due to the similar Rf values of the two isomers, the isomeric ratio was determined
1
from the H NMR spectrum of the crude mixture prior to separation by column
chromatography, which was very tedious. The proportion of the S-,N4-isomer 24
was much higher than that of the S-,N2 isomer (80:20). Moreover, in the 13 C NMR
spectrum, the appearance of the characteristic propargyl groups (SCH2, NCH2, and
C:C) as two sets of signals provided definitive proof of formation of a mixture of
S,N4- and S,N2-bis(propargylated) triazoles 24, 25.
The absence of the NH stretch at 3284–3348 cm-1 in the IR spectra of
compounds 24 and 25, and the appearance of the characteristic C:C and :C–H
bands at 2145–2153 and 3298–3306 cm-1, respectively, confirmed the incorpora-
tion of two alkyne side chains.
The NCH2- protons appeared as a doublet at d 4.98 ppm in the 1H NMR
spectrum of compound 24, resonating at lower field than for the isomeric structure
1
25 at d 5.70 ppm. Their H NMR spectra confirmed the presence of two alkyne
protons (:CH) as two triplets at d 2.29 and 2.47 ppm for 24 and as one triplet at d
2.29 ppm for 25.
The presence of characteristic signals in the 13C NMR spectrum of compound 24
at d 22.78 and 38.64 ppm, attributed to SCH2 and NCH2, respectively, confirmed
the presence of two alkyne side chains. Conversely, compound 25 showed these
carbons at d 22.32 and 89.18 ppm, respectively.
The regioselective synthesis of the S,N4-bis(1,4-disubstituted 1,2,3-triazoles) 26–
30 carrying fluorinated 1,2,4-triazole and lipophilic side chains was performed by a
copper-catalyzed click reaction between the S,N4-bis(propargylated) triazole 24 and
the appropriate long-chain alkyl azides 9–13 in aqueous t-BuOH (Scheme 5). The
synthesis required regular stirring for 16 h at room temperature to afford the desired
1,2,3-triazoles 26–30 in 84–95 % yield.
N
N
N N
CH3(CH2)nN3
9-13
(CH2)nCH3
C
CH
N
N
S
S
N
N
N
F
i
F
C
CH
(CH2)nCH3
N
N
N
26-30
24
i : CuSO4, Na-ascorbate, t-BuOH, H2O (10:1)
n = 9, 10, 11, 13, 15
Scheme 5 Synthesis of 1,4-disubstituted S,N4-bis-1,2,3-triazoles 26–30 containing 1,2,4-triazole and
lipophilic side chains
123

Click 1,4-regioselective synthesis, characterization, and…
1
The formation of the S,N4-bis(1,2,3-triazoles) 26–30 was supported by IR, H
NMR, 13C NMR, and mass spectrometric analyses. In the IR spectrum of compound
29, the disappearance of the C:C and :C–H absorption bands at 2145 and
3306 cm-1, respectively, confirmed involvement of the alkyne linkage in the
formation of the 1,2,3-triazole ring. Its 1H NMR spectrum showed the appearance of
two =C–H protons at d 8.06 ppm, confirming the presence of two 1,2,3-triazole
moieties. The SCH2 and NCH2 protons resonated as two singlets at d 4.59 and
5.39 ppm, respectively. The spectrum also revealed the presence of a triplet at d
0.88 ppm, which was attributed to the two terminal methyl groups of the lipophilic
side chain. The methylene protons resonated at their appropriate aliphatic region
(see ‘‘Experimental’’ section).
Further elucidation of the chemical structure of compound 29 was obtained from its
13C NMR spectrum, which exhibited signals at d 44.41 and 50.64 ppm, which are
characteristic of SCH2 and NCH2 carbons, respectively. New signals also appeared in
the aliphatic region, being assigned to the lipophilic side-chain carbons. The spectrum
also revealed the disappearance of the sp carbons of its starting material 24.
Antimicrobial screening
Three Gram-positive bacterial strains (Bacillus subtilis, Streptococcus pneumonia,
and Staphylococcus aureus), three Gram-negative bacteria (Escherichia coli,
Pseudomonas aeruginosa, and Klebsiella pneumonia), and two fungi (Aspergillus
fumigatus and Candida albicans) were selected as pathogenic strains to evaluate the
antimicrobial activity of the synthesized compounds by the broth dilution method
[32, 33].
The antimicrobial activity, expressed as minimum inhibitory concentration
(MIC) values (Table 1), demonstrated that most of the screened compounds
exhibited excellent inhibitory activity with MIC values of 4–8 lg/mL. 5-(4-
Fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (3) and 4-ethyl-5-(4-fluo-
rophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (7) displayed moderate to good
antibacterial activity towards all bacterial strains with MIC values of
16–31.25 lg/mL, and good to excellent antifungal activity with MIC values of
8–16 lg/mL. Moreover, the mono- (7, 8) and bis(propargylated)-1,2,4-triazoles (24)
were found to be more potent against Gram-negative bacterial strains with MIC of
16 lg/mL, showing moderate to no antifungal activity against both fungal species.
The antimicrobial screening results for the mono-1,2,3-triazoles 14–23 demon-
strated that all of the screened compounds exhibited good to excellent antibacterial
activity against Gram-positive bacteria with MIC values of 8–16 lg/mL, and
moderate to good inhibitory activity against Gram-negative bacteria with MIC
values of 16–31.25 lg/mL.
From the antibacterial bioassay results, it can be concluded that the bis-1,2,3-
triazoles 26–30 were more effective against all of the bacterial strains with MIC
values of 4–16 lg/mL. Among these, the bis-1,2,3-triazoles 28–30 including C12–
C16 alkyl side chains exhibited promising antibacterial activity with MIC of 4–8 lg/
mL against all of the bacterial strains.
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N. Rezki et al.
Table 1 Antimicrobial activity of compounds 3–30 expressed as MIC (lg/mL)
Compound
Gram-positive organismsa
Gram-negative organismsb
Fungic
Sp
Bs
Sa
Pa
Ec
Kp
Af
Ca
3
16
16
31.25
31.25
16
16
8
16
31.25
31.25
62.5
16
16
16
8
31.25
31.25
31.25
62.5
16
16
16
8
31.25
31.25
16
31.25
31.25
16
31.25
31.25
16
8
8
6
8
16
7
62.5
125
62.5
125
8
16
16
16
14
31.25
16
31.25
16
31.25
16
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
62.5
62.5
31.25
31.25
31.25
31.25
31.25
–
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
31.25
62.5
62.5
31.25
31.25
16
15
16
16
16
16
17
8
16
16
16
18
8
8
8
16
16
16
19
16
16
8
16
16
16
8
16
16
16
16
8
31.25
31.25
31.25
31.25
31.25
16
31.25
31.25
31.25
31.25
31.25
16
31.25
31.25
31.25
31.25
31.25
16
20
21
22
8
23
8
8
24
62.5
62.5
8
62.5
62.5
16
8
62.5
62.5
16
8
25
31.25
16
16
31.25
16
26
16
27
8
16
16
16
28
8
4
4
8
4
8
29
8
4
4
8
4
8
16
30
4
4
4
8
4
8
16
Ciprofloxacin
Fluconazole
a
B5
–
B1
–
B5
–
B5
B1
–
B1
–
–
–
B1
B1
MIC minimum inhibitory concentration
b
Gram-positive bacteria: Streptococcus pneumonia (RCMB 010010, Sp), Bacillus subtilis (RCMB
010067, Bs), Staphylococcus aureus (RCMB 010025, Sa)
c
Gram-negative bacteria: Pseudomonas aeruginosa (RCMB 010043, Pa), Escherichia coli (RCMB
010052, Ec), Klebsiella pneumonia (RCMB 010058, Kp)
d
Fungi: Aspergillus fumigatus (RCMB 02568, Af), Candida albicans (RCMB 05036, Ca)
On the other hand, the preliminary results of the antifungal activity assays
revealed that, among the synthesized 1,2,3-triazole derivatives, the greatest
antifungal inhibition was displayed by compounds 26–30 against all of the fungal
species with MIC values of 16–31.25 lg/mL.
From the results of the antimicrobial activity studies and the structure–activity
relationship, it can be concluded that propargylation of the 1,2,4-triazoles 3 and 6 to
the corresponding propargylated-1,2,4-triazole derivatives 7, 8, and 24 resulted in
lower inhibitory activities against Gram-positive bacterial strains and fungal
species. In addition, the clubbing of a 1,2,4-triazole moiety with a 1,2,3-triazole
carrying long alkyl side chain was found to confer excellent antibacterial activity
compared with their propargylated precursors.
123

Click 1,4-regioselective synthesis, characterization, and…
Experimental
Apparatus and analysis
Melting points were measured on a melt-temp apparatus (SMP10) and are
uncorrected. TLC was performed on precoated silica gel (Kieselgel, 0.25 mm, 60
F254, Merck, Germany), and spots were visualized by ultraviolet (UV) light
absorption using a developing solvent system of ethyl acetate/hexane. IR spectra
were measured using a PerkinElmer 1430 series Fourier-transform infrared (FTIR)
spectrometer from potassium bromide pellets. 1H NMR spectra were recorded using
an Advance Bruker NMR spectrometer at 400–600 MHz, whereas 13C NMR spectra
were obtained on the same instrument at 100–150 MHz using tetramethylsilane
(TMS) as internal standard. Mass spectra were obtained on a Finnegan mass
spectrometer (MAT312) for electron ionization mass spectroscopy (EIMS); High-
resolution mass spectroscopy (HRMS) was carried out using a Thermo Finnegan
MAT 95XP mass spectrometer.
Synthesis and characterization of 1,2,4-triazole precursors 3 and 6
Synthesis of 3-fluorophenyl thiosemicarbazide (2)
A mixture of 4-fluorobenzoyl chloride (1) (10 mmol) and thiosemicarbazide
(10 mmol) in acetone (100 mL) was heated under reflux for 2 h. The solid thus
obtained on cooling was recrystallized from ethanol to give compound 2 in 90 %
yield; M.p.: 202–204 °C (lit. [26] 205 °C).
Synthesis and characterization of 5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-
thione (3)
To 10 mmol of compound 2, 100 mL of 10 % aqueous sodium hydroxide solution
was added, followed by heating under reflux for 6 h. The reaction mixture was
cooled and filtered, and the obtained filtrate was acidified with hydrochloric acid.
The crude triazole thus obtained was filtered and recrystallized from ethanol to give
compound 3 in 87 % yield; M.p.: 173 °C (lit. [26] 174 °C). IR (KBr) (cm-1):
1
3267–3382 (NH), 3067 (CH-Ar), 1610 (C=N), 1578 (C=C), 1290 (C=S). H NMR
(400 MHz, DMSO-d6) d 7.60–7.87 (m, 4H, Ar–H), 13.83, 13.89 (2bs, 2H, 2 9 NH).
13C NMR (100 MHz, DMSO-d6) d 122.84, 127.52, 129.05, 131.92, 133.45, 137.18,
149.63, 162.52, 165.61 (Ar–C, C=N), 169.25 (C=S).
Synthesis of 1-(4-fluorobenzoyl)-4-ethylthiosemicarbazide (5)
A mixture of 4-fluorobenzohydrazide (4) (10 mmol) and ethyl isothiocyanate
(10 mmol) in ethanol (50 mL) was heated under reflux for 6 h. The solid thus
obtained on cooling was recrystallized from ethanol to give compound 5 in 92 %
yield; M.p.: 201–202 °C (lit. [27] 203 °C).
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N. Rezki et al.
Synthesis of 4-ethyl-5-(4-fluorophenyl)-2,4-dihydro-1,2,4-triazole-3-thione (6)
To 10 mmol of compound 5, 100 mL of 10 % aqueous sodium hydroxide solution
was added, followed by heating under reflux for 6 h. The reaction mixture was
cooled and filtered, and the obtained filtrate was acidified with hydrochloric acid.
The crude triazole thus obtained was filtered and recrystallized from ethanol to give
compound 6 in 89 % yield; M.p.: 242–243 °C (lit. [27] 244 °C); IR (KBr) (cm-1):
1
3284–3348 (NH), 3032 (CH-Ar), 1620 (C=N), 1559 (C=C), 1295 (C=S). H NMR
(400 MHz, DMSO-d6) d 1.14 (t, 3H, J = 4 Hz, CH3), 4.00–4.05 (q, 2H, J = 4,
J = 8 Hz, CH2), 7.40–7.46 (m, 2H, Ar–H), 7.74–7.79 (m, 2H, Ar–H), 13.95 (s, 1H,
NH); 13C NMR (100 MHz, DMSO-d6) d 13.32 (CH3), 30.64 (CH2), 116.09, 116.31,
122.61, 122.64, 131.16, 131.25, 150.28, 162.11, 164.58 (Ar–C, C=N), 166.77
(C=S).
General procedure for synthesis of mono-thiopropargylated 1,2,4-triazoles (7, 8)
To a solution of compound 3 and/or 6 (10 mmol) in ethanol (50 mL) and
triethylamine (10 mmol), propargyl bromide (10 mmol) was added with stirring,
followed by heating under reflux for 1 h. Ethanol was removed under reduced
pressure, and the resulting crude product was recrystallized from ethanol to afford
the desired product.
5-(4-Fluorophenyl)-3-[(prop-2-ynyl)thio]-4H-1,2,4-triazole (7) Yield 90 %; M.p.:
140–142 °C. IR (KBr) (cm-1): 3373 (NH), 3305 (:CH), 3029 (Ar–H), 2154
(C:C), 1603 (C=N). 1H NMR (400 MHz, DMSO-d6) d 3.20 (s, 1H, :CH), 4.02 (s,
2H, SCH2), 7.35–7.38 (m, 2H, Ar–H), 8.04 (dd, 2H, J = 6, 12 Hz, Ar–H), 14.53
(bs, 1H, NH). 13C NMR (100 MHz, DMSO-d6) d 20.41 (SCH2), 74.54 (:CH),
80.82 (C:C), 116.75, 129.06, 162.91, 164.57 (Ar–C, C=N); HRMS (ESI) 234.0496
[M ? 1].
4-Ethyl-5-(4-fluorophenyl)-3-(prop-2-yn-1-ylthio)-1,2,4-triazole (8) Yield 88 %;
M.p.: 254–255 °C. IR (KBr) (cm-1): 3310 (:CH), 3084 (Ar–H), 2149 (C:C),
1
1614 (C=N). H NMR (400 MHz, DMSO-d6) d 1.20 (t, 3H, J = 4 Hz, CH3), 3.25
(t, 1H, J = 4 Hz, :CH), 4.02–4.07 (m, 4H, SCH2, NCH2), 7.38–7.44 (m, 2H, Ar–
H), 7.70–7.74 (m, Ar–H). 13C NMR (100 MHz, DMSO-d6) d 15.10 (CH3), 21.85
(SCH2), 39.82 (NCH2-overlapped with DMSO-d6), 74.80 (:CH), 79.51 (C:C),
115.98, 116.19, 123.69, 123.72, 130.82, 130.90, 148.77, 154.23, 161.81, 164.28
(Ar–C, C=N); HRMS (ESI) 262.0776 [M ? 1].
General procedure for synthesis of mono-1,2,3-triazoles (14–23)
To a solution of compound 7 and/or 8 (1.5 mmol) in a 10:1 mixture of tert-butanol
and water (10 mL), CuSO4 (0.8 mmol), Na-ascorbate (1.1 mmol), and the
appropriate long-chain alkyl azide 9–13 (2 mmol) were added with stirring. Then,
stirring was continued for 30 h at room temperature. The consumption of the
123

Click 1,4-regioselective synthesis, characterization, and…
starting materials was monitored using TLC. Water was added to the reaction
mixture, and the product was then extracted three times with dichloromethane and
dried over sodium sulfate. Removal of the solvent in vacuum gave the title
compounds 14–23, which were crystallized from ethanol.
1-Decyl-4-(((5-(4-fluorophenyl)-4H-1,2,4-triazol-3-yl)thio)methyl)-1H-1,2,3-tria-
zole (14) Yield 96 %; M.p.: 140–141 °C. IR (KBr) (cm-1): 3324 (NH), 3048 (Ar–
1
H), 1610 (C=N). H NMR (600 MHz, DMSO-d6) d 0.9 (t, 3H, J = 6 Hz, CH3),
1.27–1.33 (m, 14H, 7 9 CH2), 1.92 (bs, 2H, NCH2CH2), 4.37 (bs, 4H, NCH2,
SCH2), 7.14 (t, 2H, J = 6 Hz, Ar–H), 7.29 (bs, 2H, Ar–H), 7.58 (s, 1H, NH), 8.10
(s, 1H, CH-1,2,3-triazole). 13C NMR (150 MHz, DMSO-d6) d 14.09 (CH3), 22.65,
26.48, 28.94, 29.23, 29.34, 29.45 (CH2), 30.15 (SCH2), 31.84 (NCH2), 115.61,
115.75, 124.11, 128.37, 130.56, 131.56, 149.48, 153.03, 161.37, 163.52 (Ar–C,
C=N); MS (EI) 416.23 [M?].
4-(((5-(4-Fluorophenyl)-4H-1,2,4-triazol-3-yl)thio)methyl)-1-undecyl-1H-1,2,3-tri-
azole (15) Yield 93 %; M.p.: 124–125 °C. IR (KBr) (cm-1): 3347 (NH), 3072
1
(Ar–H), 1604 (C=N). H NMR (600 MHz, DMSO-d6) d 0.85 (t, 3H, J = 6 Hz,
CH3), 1.17–1.26 (m, 16H, 8 9 CH2), 1.73 (bs, 2H, NCH2CH2), 4.29 (t, 2H,
J = 6 Hz, NCH2), 4.43 (s, 1.2H, SCH2), 4.52 (s, 0.8H, SCH2), 7.29 (t, 0.8H,
J = 6 Hz, Ar–H), 7.40 (t, 1.2H, J = 6 Hz, Ar–H), 8.00–8.03 (m, 3H, Ar–H, CH-
1,2,3-triazole), 14.16 (s, 0.4H, NH), 14.51 (s, 0.6H, NH). 13C NMR (150 MHz,
DMSO-d6) d 14.41 (CH3), 26.20, 28.78, 29.15, 29.26, 29.38, 29.39, 30.09 (CH2),
31.74 (SCH2), 55.35 (NCH2), 116.14, 116.77, 120.87, 123.92, 125.28, 128.35,
128.97, 130.05, 148.21, 153.44, 161.05, 162.16 (Ar–C, C=N); MS (EI) 430.33
[M?].
1-Dodecyl-4-(((5-(4-fluorophenyl)-4H-1,2,4-triazol-3-yl)thio)methyl)-1H-1,2,3-tria-
zole (16) Yield 95 %; M.p.: 117–118 °C. IR (KBr) (cm-1): 3318 (NH), 3018 (Ar–
1
H), 1600 (C=N). H NMR (600 MHz, DMSO-d6) d 0.85 (t, 3H, J = 6 Hz, CH3),
1.05–1.35 (m, 18H, 9 9 CH2), 1.74 (bs, 2H, NCH2CH2), 4.30 (bs, 2H, NCH2), 4.43
(s, 2H, SCH2), 7.38 (bs, 2H, Ar–H), 8.03 (bs, 3H, Ar–H, CH-1,2,3-triazole), 14.17
(s, 0.4H, NH), 14.50 (s, 0.6H, NH). 13C NMR (150 MHz, DMSO-d6) d 14.40 (CH3),
22.55, 26.29, 28.78, 29.16, 29.38, 29.26, 29.37, 29.45, 30.07 (CH2), 31.75 (SCH2),
49.92 (NCH2), 116.27, 116.63, 124.01, 128.51, 128.70, 130.12, 148.36, 153.43,
161.29, 162.78 (Ar–C, C=N); MS (EI) 444.35 [M?].
4-(((5-(4-Fluorophenyl)-4H-1,2,4-triazol-3-yl)thio)methyl)-1-tetradecyl-1H-1,2,3-
triazole (17) Yield 84 %; M.p.: 134–135 °C. IR (KBr) (cm-1): 3351 (NH), 3037
(Ar–H), 1615 (C=N). 1H NMR (600 MHz, DMSO-d6) d 0.85 (dd, 3H, J = 6, 12 Hz,
CH3), 1.17–1.25 (m, 22H, 11 9 CH2), 1.73 (t, 2H, J = 6 Hz, NCH2CH2), 4.29 (t,
2H, J = 6 Hz, NCH2), 4.46 (s, 2H, SCH2), 7.37 (bs, 2H, Ar–H), 7.99–8.03 (m, 3H,
Ar–H, CH-1,2,3-triazole), 14.19 (s, 0.4H,NH), 14.53 (s, 0.6H, NH). 13C NMR
(150 MHz, DMSO-d6) d 14.49 (CH3), 22.55, 26.19, 28.77, 29.17, 29.25, 29.36,
29.43, 29.47, 29.49, 30.08 (CH2), 31.82 (SCH2), 49.74 (NCH2), 115.82, 116.35,
123

N. Rezki et al.
124.48, 128.90, 129.62, 130.32, 149.08, 153.77, 161.45, 162.51 (Ar–C, C=N); MS
(EI) 472.37 [M?].
4-(((5-(4-Fluorophenyl)-4H-1,2,4-triazol-3-yl)thio)methyl)-1-hexadecyl-1H-1,2,3-
triazole (18) Yield 80 %; M.p.: 122–123 °C. IR (KBr) (cm-1): 3319 (NH), 3090
1
(Ar–H), 1611 (C=N). H NMR (600 MHz, DMSO-d6) d 0.85 (t, 3H, J = 6 Hz,
CH3), 1.17–1.26 (m, 26H, 13 9 CH2), 1.73 (t, 2H, J = 6 Hz, NCH2CH2), 4.29 (bs,
2H, NCH2), 4.43 (s, 1.1H, SCH2), 4.52 (s, 1H, SCH2), 7.29 (s, 1H, Ar–H), 7.42 (d,
1.3H, Ar–H), 8.00–8.03 (d, 3H, Ar–H, CH-1,2,3-triazole), 14.16 (s, 0.4H, NH),
14.50 (s, 0.6H, NH). 13C NMR (150 MHz, DMSO-d6) d 14.43 (CH3), 22.55, 26.20,
28.77, 29.17, 29.25, 29.36, 29.42, 29.49, 30.08 (CH2), 31.75 (SCH2), 49.76 (NCH2),
116.63, 116.90, 124.02, 128.79, 129.17, 130.87, 149.92, 153.44, 161.23, 162.80
(Ar–C, C=N); MS (EI) 500.44 [M?].
1-Decyl-4-(((4-ethyl-5-(4-fluorophenyl)-1,2,4-triazol-3-yl)thio)methyl)-1H-1,2,3-tri-
azole (19) Yield 85 %; M.p.: 87–88 °C. IR (KBr) (cm-1): 3056 (Ar–H), 1607
1
(C=N). H NMR (600 MHz, DMSO-d6) d 0.86 (dd, 3H, J = 6, 12 Hz, CH3), 1.13
(dd, 3H, J = 6, 12 Hz, NCH2CH3), 1.17–1.25 (m, 14H, 7 9 CH2), 1.71–1.79 (m,
2H, NCH2CH2), 3.87–3.92 (q, 3H, J = 6,12 Hz, NCH2CH3), 4.30 (q, 2H,
J = 6 Hz, NCH2), 4.49 (s, 2H, SCH2), 7.43 (dd, 2H, J = 6, 12 Hz, Ar–H), 7.71
(ddd, 2H, J = 6, 12 Hz, Ar–H), 7.99 (s, 1H, CH-1,2,3-triazole). 13C NMR
(150 MHz, DMSO-d6) d 14.40 (CH3), 15.44 (NCH2CH3), 22.54, 26.25, 28.51,
28.81, 29.1, 29.29, 29.35, 30.16 (CH2), 31.73 (SCH2), 39.98 (NCH2-overlapped
with DMSO-d6), 49.76 (NCH2), 116.49, 116.64, 124.02, 124.66, 131.25, 131.41,
143.00, 150.00, 154.49, 162.95, 164.55 (Ar–C, C=N); MS (ESI) 444.36 [M?].
4-(((4-Ethyl-5-(4-fluorophenyl)-1,2,4-triazol-3-yl)thio)methyl)-1-undecyl-1H-1,2,3-
triazole (20) Yield 83 %; M.p.: 91–92 °C. IR (KBr) (cm-1): 3042 (Ar–H), 1602
(C=N). 1H NMR (600 MHz, DMSO-d6) d 0.85 (bt, 3H, CH3), 1.10 (bt, 3H,
NCH2CH3), 1.20–1.25 (m, 16H, 8 9 CH2), 1.74 (t, 3H, J = 6 Hz, NCH2CH2),
3.91–3.96 (q, 2H, J = 6, 12 Hz, NCH2CH3), 4.31 (t, 2H, J = 6 Hz, NCH2), 4.50 (s,
2H, SCH2), 7.40–7.46 (m, 2H, Ar–H), 7.70–7.77 (m, 2H, Ar–H), 8.01 (s, 1H, CH-
1,2,3-triazole). 13C NMR (150 MHz, DMSO-d6) d 14.53 (CH3), 15.41 (NCH2CH3),
22.55, 26.23, 28.48, 28.82, 29.15, 29.29, 29.41, 30.17 (CH2), 31.74 (SCH2), 39.98
(NCH2-overlapped with DMSO-d6), 49.82 (NCH2), 116.49, 116.63, 124.17, 131.28,
131.33, 162.68, 164.33 (Ar–C); MS (EI) 458.33 [M?].
1-Dodecyl-4-(((4-ethyl-5-(4-fluorophenyl)-1,2,4-triazol-3-yl)thio)methyl)-1H-1,2,3-
triazole (21) Yield 82 %; M.p.: 99–100 °C. IR (KBr) (cm-1): 3076 (Ar–H), 1611
(C=N). 1H NMR (600 MHz, DMSO-d6) d 0.86 (dd, 3H, J = 6, 12 Hz, CH3), 1.11 (t,
3H, J = 6 Hz, NCH2CH3), 1.20–1.27 (m, 18H, 9 9 CH2), 1.71–1.76 (m, 2H,
NCH2CH2), 3.89–3.93 (q, 2H, J = 6 Hz, NCH2CH3), 4.32 (dd, 2H, J = 6, 12,
NCH2), 4.50 (s, 2H, SCH2), 7.42 (dd, 2H, J = 6, 12, Ar–H), 7.72 (ddd, 2H, J = 6,
12, Ar–H), 8.01 (s, 1H, CH-1,2,3-triazole). 13C NMR (150 MHz, DMSO-d6) d
14.41 (CH3), 15.41 (NCH2CH3), 22.55, 26.23, 28.47, 28.82, 29.16, 29.29, 29.40,
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Click 1,4-regioselective synthesis, characterization, and…
29.46, 30.17 (CH2), 31.75 (SCH2), 39.98 (NCH2-overlapped with DMSO-d6), 49.82
(NCH2), 116.49, 116.63, 124.18, 131.28, 131.34, 162.68, 164.33 (Ar–C, C=N); MS
(EI) 472.43 [M?].
4-(((4-Ethyl-5-(4-fluorophenyl)-1,2,4-triazol-3-yl)thio)methyl)-1-tetradecyl-1H-
1,2,3-triazole (22) Yield 83 %; M.p.: 106–107 °C; IR (KBr) tmax/cm-1 3028 (Ar–
1
H), 1605 (C=N). H NMR (600 MHz, DMSO-d6) d 0.86 (t, 3H, J = 6 Hz, CH3),
1.13 (dd, 3H, J = 6, 12 Hz, NCH2CH3), 1.17–1.26 (m, 22H, 11 9 CH2), 1.71–1.76
(m, 2H, NCH2CH2), 3.89–3.93 (q, 2H, J = 6, 12 Hz, NCH2CH3), 4.32 (dd, 2H,
J = 6, 12 Hz, NCH2), 4.50 (s, 2H, SCH2), 7.41 (dd, 2H, J = 6, 12 Hz, Ar–H), 7.72
(ddd, 2H, J = 6, 12 Hz, Ar–H), 8.00 (s, 1H, CH-1,2,3-triazole). 13C NMR
(150 MHz, DMSO-d6) d 14.52 (CH3), 15.48 (NCH2CH3), 22.55, 26.22, 28.80,
29.16, 29.28, 29.39, 29.46, 29.50, 30.17 (CH2), 31.75 (SCH2), 39.98 (NCH2-
overlapped with DMSO-d6), 49.92 (NCH2), 116.50, 116.64, 131.26, 131.32, 162.67,
164.32 (Ar–C, C=N); MS (EI) 500.39 [M?].
4-(((4-Ethyl-5-(4-fluorophenyl)-1,2,4-triazol-3-yl)thio)methyl)-1-hexadecyl-1H-
1,2,3-triazole (23) Yield 86 %; M.p.: 115–116 °C. IR (KBr) (cm-1): 3067 (Ar–
1
H), 1616 (C=N). H NMR (600 MHz, DMSO-d6) d 0.86 (t, 3H, J = 6 Hz, CH3),
1.11 (t, 3H, J = 6 Hz, NCH2CH3), 1.16–1.24 (m, 26H, 13 9 CH2), 1.71–1.75 (m,
2H, NCH2CH2), 3.90–3.93 (q, 2H, J = 6, 12 Hz, NCH2), 4.31 (dd, 2H, J = 6,
12 Hz, NCH2), 4.50 (s, 2H, SCH2), 7.41 (dd, 2H, J = 6, 12 Hz, Ar–H), 7.71 (m, 2H,
Ar–H), 8.03 (s, 1H, CH-1,2,3-triazole); 13C NMR (150 MHz, DMSO-d6) d 14.41
(CH3), 15.40 (NCH2CH3), 22.55, 26.23, 28.48, 28.81, 29.16, 29.28, 29.39, 29.44,
29.46, 29.49, 30.16 (CH2), 31.75 (SCH2), 39.98 (NCH2-overlapped with DMSO-
d6), 49.86 (NCH2), 116.49, 116.63, 131.28, 131.34, 162.69, 164.33 (Ar–C, C=N);
MS (EI) 528.46 [M?].
General procedure for synthesis of S,N-bis(propargylated)-1,2,4-triazoles (24, 25)
To 10 mmol of compound 3 in 25 mL DMF, 22 mmol sodium bicarbonate and
22 mmol propargyl bromide were added, and the reaction mixture was heated under
reflux for 8 h. After cooling, it was poured into ice water and the resulting solid was
filtered and purified by column chromatography to afford a mixture of S,N4- and
S,N2-bis(propargylated)-1,2,4-triazoles 24 and 25 in 85 % overall yield.
5-(4-Fluorophenyl)-4-(prop-2-yn-1-yl)-3-(prop-2-yn-1-ylthio)-4H-1,2,4-triazole
(24) Obtained after separation by column chromatography (eluent hexane:EtOAc,
95:5) in 62 % yield; M.p.: 147–148 °C. IR (KBr) (cm-1): 3306 (:CH), 3043 (Ar–
1
H), 2145 (C:C), 1606 (C=N). H NMR (400 MHz, DMSO-d6) d 2.29 (t, 1H,
J = 4 Hz, :CH), 2.47 (t, 1H, J = 4 Hz, :CH), 4.01 (d, 2H, J = 4 Hz, SCH2),
4.98 (d, 2H, J = 4 Hz, NCH2), 7.08–7.14 (m, 2H, Ar–H), 8.05–8.10 (m, 2H, Ar–H).
13C NMR (100 MHz, DMSO-d6) d 22.78 (SCH2), 38.64 (NCH2), 72.72 (:CH),
74.60 (:CH), 75.76 (C:C), 78.20 (C:C), 115.43, 115.65, 126.71, 126.74,
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N. Rezki et al.
128.27, 128.36, 150.81, 161.62, 162.42, 164.89 (Ar–C, C=N). HRMS (ESI)
272.0638 [M ? 1].
5-(4-Fluorophenyl)-2-(prop-2-yn-1-yl)-3-(prop-2-yn-1-ylthio)-4H-1,2,4-triazole
(25) Obtained after separation by column chromatography (eluent hexane:EtOAc,
95:5) in 13 % yield; M.p: 168–169 °C. IR (KBr) (cm-1): 3298 (:CH), 3054 (Ar–
1
H), 2153 (C:C), 1600 (C=N). H NMR (400 MHz, DMSO-d6) d 2.29 (t, 2H,
J = 4 Hz, 2 9 :CH), 4.07 (d, 2H, J = 4 Hz, SCH2), 5.70 (d, 2H, J = 4 Hz,
NCH2), 7.08–7.17 (m, 2H, Ar–H), 8.06–8.09 (m, 2H, Ar–H). 13C NMR (100 MHz,
DMSO-d6) d 22.32 (SCH2), 72.48 (:CH), 78.23 (:CH), 89.18 (NCH2), 96.98
(C:C), 115.44, 115.66, 126.58, 126.61, 128.38, 128.47, 151.60, 161.53, 162.47,
164.94 (Ar–C, C=N); HRMS (ESI) 272.0642 [M ? 1].
General procedure for synthesis and characterization of bis-1,2,3-triazoles (26–30)
To a solution of compound 24 (1.5 mmol) in a 10:1 mixture of tert-butanol and
water (10 mL), CuSO4 (1.6 mmol), Na-ascorbate (2.2 mmol), and the appropriate
long-chain alkyl azide 9–13 (4 mmol) were added with stirring. Stirring was then
continued for 30 h at room temperature. The consumption of the starting materials
was monitored using TLC. Water was added to the reaction mixture, then the
product was extracted three times with dichloromethane and dried over sodium
sulfate. Removal of the solvent in vacuum gave the title compounds 26–30, which
were crystallized from ethanol.
1-Decyl-4-(((4-((1-decyl-1H-1,2,3-triazol-4-yl)methyl)-5-(4-fluorophenyl)-4H-
1,2,4-triazol-3-yl)thio)-methyl)-1H-1,2,3-triazole
(26) Yield
95 %;
M.p.:
66–67 °C. IR (KBr) (cm-1): 3067 (Ar–H), 1616 (C=N). 1H NMR (400 MHz,
DMSO-d6) d 0.87 (t, 6H, J = 4 Hz, 2 9 CH3), 1.24–1.30 (m, 28H, 14 9 CH2),
1.82–1.88 (m, 4H, 2 9 NCH2CH2), 4.24, 4.33 (2t, 4H, J = 8 Hz, 2 9 NCH2CH2),
4.59 (s, 2H, SCH2), 5.40 (s, 2H, NCH2), 7.12 (dd, 2H, J = 8, 12 Hz, Ar–H),
7.58–7.74 (bs, 2H, Ar–H), 8.07 (s, 2H, CH-1,2,3-triazole). 13C NMR (100 MHz,
DMSO-d6) d 14.08 (CH3), 22.65, 26.47, 26.52, 28.95, 28.97, 29.24, 29.34, 29.38,
29.46, 29.70, 30.14, 30.19, 31.85 (CH2), 44.94 (SCH2), 50.63 (NCH2), 115.43,
115.65, 127.04, 128.11, 128.20, 162.35, 164.82 (Ar–C, C=N). HRMS (ESI):
638.4088 [M ? 1].
4-(((5-(4-Fluorophenyl)-4-((1-undecyl-1H-1,2,3-triazol-4-yl)methyl)-4H-1,2,4-tria-
zol-3-yl)thio)methyl)-1-undecyl-1H-1,2,3-triazole (27) Yield 89 %; M.p.:
78–79 °C. IR (KBr) (cm-1): 3086 (Ar–H), 1602 (C=N). 1H NMR (400 MHz,
DMSO-d6) d 0.88 (t, 6H, J = 4 Hz, 2 9 CH3), 1.24–1.29 (m, 32H, 16 9 CH2),
1.82–1.88 (m, 4H, 2 9 NCH2CH2), 4.25, 4.33 (2t, 4H, J = 8 Hz, 2 9 NCH2CH2),
4.58 (s, 2H, SCH2), 5.39 (s, 2H, NCH2), 7.12 (dd, 2H, J = 8, 12 Hz, Ar–H),
7.77–7.82 (m, 2H, Ar–H), 8.07 (s, 2H, CH-1,2,3-triazole). 13C NMR (100 MHz,
DMSO-d6) d 14.09 (CH3), 28.96, 28.98, 29.30, 29.34, 29.38, 29.52, 29.54, 30.14,
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Click 1,4-regioselective synthesis, characterization, and…
30.20, 31.89 (CH2), 44.47 (SCH2), 50.79 (NCH2), 115.44, 115.65, 127.06, 127.08,
128.09, 128.17, 162.35, 164.82 (Ar–C, C=N); HRMS (ESI) 665.4533 [M ? 1].
1-Dodecyl-4-(((4-((1-dodecyl-1H-1,2,3-triazol-4-yl)methyl)-5-(4-fluorophenyl)-4H-
1,2,4-triazol-3-yl)thio)methyl)-1H-1,2,3-triazole (28) Yield 84 %; M.p.: 74–75 °C. IR
(KBr) (cm-1): 3029 (Ar–H), 1601 (C=N). 1H NMR (400 MHz, DMSO-d6) d 0.88 (t,
6H, J = 4 Hz, 2 9 CH3), 1.24–1.30 (m, 36H, 18 9 CH2), 1.82–1.88 (m, 4H,
2 9 NCH2CH2), 4.26, 4.32 (2t, 4H, J = 8 Hz, 2 9 NCH2CH2), 4.59 (s, 2H, SCH2),
5.40 (s, 2H, NCH2), 7.11 (dd, 2H, J = 8, 12 Hz, Ar–H), 7.67–7.79 (m, 2H, Ar–H),
8.07 (s, 2H, CH-1,2,3-triazole). 13C NMR (100 MHz, DMSO-d6) d 14.10 (CH3),
22.68, 26.48, 26.54, 28.96, 28.98, 29.33, 29.35, 29.39, 29.52, 29.60, 30.13, 30.18,
31.91 (CH2), 44.58 (SCH2), 50.66 (NCH2), 115.44, 115.65, 127.01, 128.11, 128.20,
162.35, 164.83 (Ar–C, C=N); HRMS (ESI) 694.4680 [M ? 1].
4-(((5-(4-Fluorophenyl)-4-((1-tetradecyl-1H-1,2,3-triazol-4-yl)methyl)-4H-1,2,4-
triazol-3-yl)thio)methyl)-1-tetradecyl-1H-1,2,3-triazole (29) Yield 84 %; M.p.:
78–80 °C. IR (KBr) (cm-1): 3090 (Ar–H), 1608 (C=N). 1H NMR (400 MHz,
DMSO-d6) d 0.88 (t, 6H, J = 4 Hz, 2 9 CH3), 1.25–1.30 (m, 44H, 22 9 CH2),
1.81–1.89 (m, 4H, 2 9 NCH2CH2), 4.23, 4.32 (2t, 4H, J = 8 Hz, 2 9 NCH2CH2),
4.59 (s, 2H, SCH2), 5.39 (s, 2H, NCH2), 7.12 (dd, 2H, J = 8, 12 Hz, Ar–H),
7.65–7.75 (m, 2H, Ar–H), 8.06 (s, 2H, CH-1,2,3-triazole). 13C NMR (100 MHz,
DMSO-d6) d 14.11 (CH3), 22.69, 26.46, 26.51, 28.96, 28.99, 29.35, 29.39, 29.53,
29.60, 29.65, 29.68, 30.17, 30.21, 31.93 (CH2), 44.41 (SCH2), 50.52, 50.64 (NCH2),
115.44, 115.66, 127.06, 128.11, 128.20, 161.33, 162.35, 164.83 (Ar–C, C=N);
HRMS (ESI) 750.5380 [M ? 1].
4-(((5-(4-Fluorophenyl)-4-((1-hexadecyl-1H-1,2,3-triazol-4-yl)methyl)-4H-1,2,4-
triazol-3-yl)thio)methyl)-1-hexadecyl-1H-1,2,3-triazole (30) Yield 90 %; M.p.:
82–84 °C. IR (KBr) (cm-1): 3070 (Ar–H), 1615 (C=N). 1H NMR (400 MHz,
DMSO-d6) d 0.88 (t, 6H, J = 4 Hz, 2 9 CH3), 1.24–1.30 (m, 52H, 26 9 CH2),
1.82–1.89 (m, 4H, 2 9 NCH2CH2), 4.27, 4.32 (2t, 4H, J = 8 Hz, 2 9 NCH2CH2),
4.58 (s, 2H, SCH2), 5.40 (s, 2H, NCH2), 7.09 (dd, 2H, J = 8, 12 Hz, Ar–H),
7.69–7.81 (m, 2H, Ar–H), 8.07 (s, 2H, CH-1,2,3-triazole). 13C NMR (100 MHz,
DMSO-d6) d 14.11 (CH3), 22.69, 26.50, 26.55, 28.97, 29.36, 29.40, 29.53, 29.61,
29.66, 29.69, 31.93 (CH2), 44.50 (SCH2), 50.87 (NCH2), 115.43, 115.65, 127.01,
128.11, 128.19, 162.35, 164.82 (Ar–C, C=N); HRMS (ESI) 806.3018 [M ? 1].
Antimicrobial activity
Cell lines
The newly synthesized 1,2,3-triazole derivatives 3–30 were evaluated for antimi-
crobial activity against several isolated clinical strains from the Regional Center for
Mycology and Biotechnology (RCMB). Three Gram-positive bacteria (Bacillus
subtilis RCMB 010067, Streptococcus pneumonia RCMB 010010, and
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N. Rezki et al.
Staphylococcus aureus RCMB 010025), three Gram-negative bacteria (Escherichia
coli RCMB 010052, Pseudomonas aeruginosa RCMB 010043, and Klebsiella
pneumonia RCMB 010058), and two fungi (Aspergillus fumigatus RCMB 02568
and Candida albicans RCMB 05036) were selected for use in the assay.
Antimicrobial evaluation using MIC assay
Preliminary in vitro evaluation of antimicrobial activity was performed using the
broth microdilution method [32, 33]. The minimum inhibitory concentration of the
tested compounds was defined as the lowest concentration of each chemical
compound in the tubes with no growth of inoculated bacteria/fungi. Thus, 10 mg of
analyte was dissolved in dimethylsulfoxide (DMSO, 1 mL), then diluted in culture
medium (Mueller–Hinton broth for bacteria and Sabouraud liquid medium for
fungi). Additional dilutions with distilled water afforded different concentrations (1,
2, 4, 8, 16, 31.25, 62.5, 125, 250, and 500 mg/mL) of the tested compounds. The
tubes were incubated at 37 °C for 24 h.
Conclusions
We report on Huisgen click synthesis of novel bioactive 1,2,3-triazole nonionic
surfactants carrying a 1,2,4-triazole scaffold. The approach involved first regios-
elective propargylation of the 1,2,4-triazole-3-thione in presence of an appropriate
basic catalyst, followed by Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction with
several long-chain alkyl azides to afford corresponding S-mono- and S,N4-bis(1,2,3-
triazoles) tethering fluorinated 1,2,4-triazole and lipophilic side chains. The
antimicrobial bioassay results revealed that the structural combination of 1,2,3-
triazole, 1,2,4-triazole, and lipophilic side chains furnished novel, potentially active,
antibacterial and antifungal agents.
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