HClO4-SiO2: An efficient reusable catalyst for the synthesis of 3,4,5-trisubstituted 1,2,4-triazoles under solvent-free conditions

Article abstract of DOI:10.1007/s10562-011-0665-4

A series of 3,4,5-trisubstituted 1,2,4-triazoles have been synthesized from N³-substituted amidrazones and anhydrides using HClO ₄-SiO₂ at 80 °C under solvent-free conditions. The products were obtained in excellent yields

Full text of DOI:10.1007/s10562-011-0665-4

Catal Lett (2011) 141:1511–1520
DOI 10.1007/s10562-011-0665-4
HClO4-SiO2: An Efficient Reusable Catalyst for the Synthesis
of 3,4,5-Trisubstituted 1,2,4-Triazoles Under Solvent-Free
Conditions
•
Vidavalur Siddaiah Gajula Mahaboob Basha
•
•
Rayavarapu Srinuvasarao Santosh Kumar Yadav
Received: 28 May 2011 / Accepted: 1 July 2011 / Published online: 28 July 2011
Ó Springer Science+Business Media, LLC 2011
Abstract A series of 3,4,5-trisubstituted 1,2,4-triazoles
have been synthesized from N3-substituted amidrazones
and anhydrides using HClO4-SiO2 at 80 °C under solvent-
free conditions. The products were obtained in excellent
yields within 5–10 min. Therefore, the present method will
be of wide application in organic chemistry and medicinal
chemistry.
known to possess significant biological activities such
as antibacterial [9–11], antifungal [12], antitumor [13, 14],
anti-inflammatory [15, 16], antiviral [17, 18], analgesic
[19] and central nervous system (CNS) depressant activity
[20]. 3,4,5-Trisubstituted 1,2,4-triazoles also act as inter-
mediates in the synthesis of many drugs available in the
market such as maraviroc (UK-427,857) (1) [21], triazo-
lam (2) [22] and sitagliptin (MK-0431) (3) [23]. Owing to
their important applications, various synthetic methodol-
ogies of 1,2,4-triazole derivatives have been developed
[6]. Generally 1,2,4-triazole derivatives are synthesized by
the cyclodehydration of N-acylamidrazones [6, 24]. 1,2,4-
Triazole derivatives were also synthesized directly from
amidrazones and anhydrides using acetic acid or diethyl
ether as a solvent [20, 25]. However, these methods
always suffered from the limitation of harsh conditions,
tedious synthetic procedures, long reaction times and
unsatisfactory yields. Therefore, developing a milder and
more general procedure to access 1, 2, 4-triazole deriva-
tives is still highly desirable.
Keywords 1,2,4-Triazole Á HClO4-SiO2 Á Solvent-free
conditions Á Amidrazone Á Heterogeneous catalyst
1 Introduction
The ubiquitous triazoles have attracted more attention in
both industrial and academic fields for decades [1–6]. This
interest arises from the fact that a variety of natural and
synthetic compounds which contain the triazole sub-
structure exhibit a broad spectrum of biological activity
[7, 8]. Compounds bearing 1,2,4-triazole scaffolds are
F
F
N
F
N
F
F
N
O
F
F
N
N
H3C
H3C
N
N
NH
N
N
Cl
N
NH2
O
N
F
N
Cl
CH3
Maraviroc
Triazolam
Stiagliptin
1
2
3
V. Siddaiah (&) Á G. M. Basha Á R. Srinuvasarao Á S. K. Yadav
Department of Organic Chemistry & FDW, Andhra University,
Vishakapatnam 530 003, India
In recent years heterogeneous catalysts are gaining
more importance due to enviro-economic factor [26].
They have successfully been utilized in several organic
e-mail: sidduchem@gmail.com
123

1512
V. Siddaiah et al.
N
N
The scope of HClO4-SiO2 catalyzed cascade reactions of
N3-substituted amidrazones with anhydrides was investi-
gated under optimized conditions. As shown in Table 2 all
the examined substrates provided, moderate to good yields
at 80 °C in 5–10 min. For example, N3-phenylbenzamid-
razones with different substitutions could provide the cor-
responding products with high yields regardless of the
difference of the substituent. This meant that steric effect
and electronic effect had little influence on the reaction.
When the reaction substrates switched from N3-phenyl-
benzamidrazones to N3-phenylalkylamidrazones, the reac-
tions can be carried out smoothly to give the corresponding
products with good yields (Table 2, 6g–6h). Acyclic anhy-
drides such as, symmetrical and mixed anhydrides (5a, 5b,
5c, 5d, & 5e) were more beneficial for this transformation,
while the cyclic anhydride (5f) decreased the reaction yields.
The superiority of this method over previous methods
could be established while comparing the results obtained
with maleic anhydride, and acetic anhydride. Thus, maleic
anhydride was condensed with N3-phenylbenzamidrazone at
ambient temperature in ether, respective Z-3-(3,4-diphenyl-
1,2,4-triazole-5-yl)prop-2-enoic acid afforded 72% yield in
48 h [20], whereas the corresponding product could be
obtained in 85% yield within 10 min in the present method.
The reaction of N3-phenylbenzamidrazone with acetic
anhydride in acetic acid under reflux conditions resulted in
80% yield of the 3-methyl-4,5-diphenyl-4H-[1,2,4]triazole
in 2 h [25], whereas the present method affords a 95% yield
of the corresponding product in 5 min.
NH2
NH
N
HClO4-SiO2
R3
R3 CO-O-COR4
N
R1
+
80 οC, 5-10 min
solvent -free
R1
5
R2
6
R2
4
Scheme 1 Synthesis of 3,4,5-trisubstituted-1,2,4-triazoles
transformations to minimize undesirable waste causing
environmental pollution. To the best of our knowledge, no
report has been developed for the synthesis of 3,4,5-tri-
substituted 1,2,4-triazoles using heterogeneous catalyst.
Thus, in continuation of our work [27–29] on the devel-
opment of efficient and environmentally benign synthetic
methodologies using economic and eco-friendly heteroge-
neous catalysts, herein, we reported a simple and efficient
method for the synthesis of 3,4,5-trisubstituted-1,2,4-tria-
zoles using silica-supported perchloric acid (HClO4-SiO2)
[30, 31] at 80 °C under solvent-free conditions (Scheme 1).
2 Results and Discussion
To initiate our study, the reaction of N3-phenylbenzamid-
razone (4a) with acetic anhydride (5a) was chosen as a
model reaction in the presence of HClO4-SiO2 at room
temperature under solvent-free conditions. It was found that
the reaction led to desired 3-methyl-4,5-diphenyl-4H-
[1,2,4]triazole with an yield of 55% after 3 h (Table 1, entry
1). Then we optimized the reaction conditions to increase the
yield of the product and to reduce the reaction time. Thus,
temperature was initially increased to 50 °C and then to
80 °C, correspondingly yields were 75 and 95% (Table 1,
entries 2 & 3), respectively. When the temperature was
further increased to 100 and 120 °C, no improvement but a
slight lowering in the yield was observed (Table 1, entries 4
& 5). Further it was observed in our investigations that when
the reaction temperature was increased to 80 °C, surpris-
ingly, the reaction was completed within 5 min. In order to
determine the potency of HClO4-SiO2 as catalyst, the same
reaction was carried out with various heterogeneous cata-
lysts under similar experimental conditions. The results
summarized in Table 1 (entries 6–9) revealed that these
heterogeneous catalysts afforded comparatively lower
yields of the desired product, even with high catalyst load-
ings, while very low yield of the product was obtained
without any catalyst (Table 1, entries 10 & 11). Moreover,
HClO4-SiO2 catalyst was recovered, activated and reused
for three consecutive times with only slight variation in the
yields of the products (93, 92, and 90%).
3 Conclusions
In Conclusion, we have developed a simple, efficient and
eco-friendly method for the synthesis of 3,4,5-trisubstituted
1,2,4-triazoles using HClO4-SiO2. The protocol uses N3-
substituted amidrazones and anhydrides as starting mate-
rials, and the corresponding products were obtained in
moderate to good yields at 80 °C under solvent free con-
ditions. The HClO4-SiO2 catalyst was reused for three
consecutive times with only slight variation in the yields of
the products. The 1,2,4-triazole derivatives are biologically
and pharmaceutically active molecules, and therefore, the
present method will be of wide application in organic
chemistry and medicinal chemistry.
4 Experimental
4.1 General Remarks
Melting points were recorded on a Mel-Temp melting point
apparatus, in open capillaries and are uncorrected. IR
123

HClO4-SiO2: An Efficient Reusable Catalyst
1513
Table 1 Optimization of reaction conditions
Entry
Catalyst
Amount of
catalyst (mol %)
Temperature (°C)
Time (min)
Yield (%)
1
HClO4-SiO2
HClO4-SiO2
HClO4-SiO2
HClO4-SiO2
HClO4- SiO2
Activated SiO2
NaHSO4-SiO2
PTSA-SiO2
Amberlyst-15
–
1
1
rt
180
30
5
55
75
95
93
89
50
60
85
75
30
40
2
50 °C
80 °C
100 °C
120 °C
80 °C
80 °C
80 °C
80 °C
rt
3
1
4
1
5
5
1
5
6
10
5
5
7
5
8
5
5
9
5
5
10
11
240
60
–
80 °C
All the reactions were performed using N3-phenylbenzamidrazone (4a) (0.66 mmol) and acetic anhydride (5a) (0.80 mmol)
4.3 Product Characterization Data
spectra were recorded on a Perkin-Elmer BX1 FTIR
1
Spectrophotometer and H NMR (400 MHz), 13C NMR
4.3.1 3-Methyl-4,5-diphenyl-4H-[1,2,4]triazole (6a)
(100 MHz) spectra were recorded on a Bruker AMX
400 MHz NMR spectrometer using TMS as internal stan-
dard and the values for chemical shifts (d) being given in
ppm and coupling constants (J) in Hertz (Hz). Mass spectra
were recorded on an Agilent 1100 LC/MSD. Acme silica
gel G and silica gel (100–200 mesh) were used for ana-
lytical TLC and column chromatography, respectively.
Silica-supported perchloric acid (HClO4-SiO2) [30] and
compounds 4a–h, & 5e were prepared according to the
literature procedure [32, 33]. Other chemicals were pur-
chased from Sigma Aldrich and used without further
purification.
Mp: 158–161 °C. 1H NMR (400 MHz, CDCl3): d = 7.52–7.49
(3H, m), 7.42–7.39 (2H, m), 7.33–7.23 (3H, m), 7.20–7.18
(2H,m), 2.35 (3H, s). 13C NMR (100 MHz, CDCl3):
d = 153.95, 152.6, 135.1, 130.1, 129.6, 129.4, 128.4,
128.2, 127.2, 127.1, 11.3. ESIMS: m/z 236 [M ? 1]?.
Anal. Calcd. for C15H13N3: C, 76.57; H, 5.57; N, 17.86.
Found: C, 76.51; H, 5.64; N, 17.81.
4.3.2 3-Methyl-5-phenyl-4-p-tolyl-4H-[1,2,4]triazole (6b)
1
Mp: 159–162 °C. H NMR (400 MHz, CDCl3): d = 7.41
(2H, d, J = 8.0 Hz), 7.33–7.23 (5H, m), 7.06 (2H, d,
J = 8.0 Hz), 2.43 (3H, s), 2.33 (3H, s). 13C NMR
(100 MHz, CDCl3): d = 153.92, 152.8, 139.8, 132.4,,
130.6, 129.3, 128.3, 128.1, 127.2, 126.9, 21.1, 11.3.
ESIMS: m/z 250 [M ? 1]?. Anal. Calcd. for C16H15N3: C,
77.08; H, 6.06; N, 16.85. Found: C, 77.03; H, 6.10; N,
16.80.
4.2 Synthesis of 3,4,5-Trisubstituted 1,2,4-Triazoles.
General Procedure
A mixture of N3-substituted amidrazone (4) (0.66 mmol),
anhydride (5) (0.80 mmol) and 1 mol % of HClO4-SiO2
was stirred at 80 °C for the given time (Table 2). After
completion of the reaction, as indicated by TLC, the
mixture was cooled to room temperature. Then the reaction
mixture was diluted with DCM (5 mL) and the catalyst
allowed to settle down. The supernatant DCM solution was
decanted off, the catalyst washed with DCM (2 mL) and
Et2O (2 mL) and the combined organic solution was
washed with water, dried over anhydrous MgSO4 and
concentrated under vacuum to afford the crude product,
which was purified by column chromatography on silica
gel (9:1, CHCl3-MeOH) to afford the pure product. The
recovered catalyst was activated by heating at 80 °C under
vacuum for 2 h and reused three times with only a little
variation in the yields of the products.
4.3.3 4-(4-Methoxy-phenyl)-3-methyl-5-phenyl-4H-
[1,2,4]triazole (6c)
1
Mp: 158–160 °C. H NMR (400 MHz, CDCl3): d = 7.42
(2H, d, J = 6.8 Hz), 7.33–7.24 (3H, m), 7.11 (2H, d,
J = 8.8 Hz), 6.98 (2H, d, J = 8.8 Hz), 3.86 (3H, s), 2.32
(3H, s). 13C NMR (100 MHz, CDCl3): d = 160.2, 154.0,
152.9, 129.3, 128.3, 128.1, 127.5, 127.2, 115.2, 55.5, 11.2.
ESIMS: m/z 266 [M ? 1]?. Anal. Calcd. for C16H15N3O:
C, 72.43; H, 5.70; N, 15.84. Found: C, 72.38; H, 5.77; N,
15.79.
123

1514
V. Siddaiah et al.
Table 2 HClO4-SiO2 catalyzed synthesis of 3,4,5-trisubstituted 1,2,4-triazoles
Amidrazone
(4)
Anhydride
(5)
Product
(6)
Time
(min)
Yield
(%)b
Entry
NH2
N
O
N
N
N
NH
5
5
5
O
1
95
95
O
6a
6b
5a
4a
NH2
NH
N
N
N
N
N
2
3
4
5a
5a
5a
4b
4c
NH2
NH
N
N
N
95
93
O
O
6c
NH2
N
N
N
N
NH
6
6
7
Br
6d
Br
4d
NH2
N
N
N
NH
N
5
6
5a
5a
93
Cl
4e
Cl
6e
NH2
NH
N
N
N
N
91
93
F
6f
F
4f
NH2
NH
N
N
N
N
7
5a
5a
5
5
6g
4g
NH2
NH
N
N
N
N
8
93
6h
4h
123

HClO4-SiO2: An Efficient Reusable Catalyst
1515
Table 2 continued
Amidrazone
Anhydride
(5)
Product
(6)
Time
(min)
Yield
(%)b
Entry
(4)
NH2
N
O
O
N
N
N
NH
9
5
6
5
6
95
95
95
95
O
6i
6j
5b
4a
NH2
N
N
N
N
NH
10
5b
Br
Br
4d
NH2
N
O
O
N
N
N
NH
11
O
6k
5c
4a
NH2
N
N
N
N
NH
12
5c
Br
6l
Br
4d
N
N
NH2
N
O
N
NH
O
13
6
6
5
93
93
92
O
6m
4a
5d
NH2
N
N
N
N
NH
14
5d
Br
Br
6n
4d
N
N
NH2
N
O
O
O
N
NH
15
O
4a
6o
5e
123

1516
V. Siddaiah et al.
Table 2 continued
Amidrazone
Anhydride
(5)
Product
(6)
Time
(min)
Yield
(%)b
Entry
16
(4)
N
NH2
NH
N
N
N
5e
5e
5
8
92
90
4b
4d
6p
6q
N
N
N
NH2
NH
N
17
Br
Br
NH2
NH
N
N
N
N
18
19
5e
8
90
85
F
6r
F
4f
O
HO
NH2
NH
O
O
N
N
N
N
10
O
5f
4a
6s
O
HO
NH2
NH
N
N
N
N
20
5f
10
85
4b
6t
O
HO
NH2
NH
N
N
N
N
21
5f
10
83
Br
4d
Br
6u
123

HClO4-SiO2: An Efficient Reusable Catalyst
1517
Table 2 continued
Amidrazone
Anhydride
(5)
Product
(6)
Time
(min)
Yield
(%)b
Entry
(4)
O
HO
NH2
N
N
N
N
NH
22
5f
10
80
F
4f
F
6v
O
HO
NH2
N
N
N
NH
23
5f
10
85
N
4h
6w
Reaction conditions: N3-phenylsubstituted benzamidrazone (0.66 mmol), Anhydrides (0.80 mmol), HClO4-SiO2 (1 mol %), 80 °C, solvent-free
conditions
a
isolated yield
4.3.4 4-(4-Bromo-phenyl)-3-methyl-5-phenyl-4H-
[1,2,4]triazole (6d)
d = 164.12, 154.0, 152.6, 131.1, 131.0, 129.6, 129.1,
128.5, 128.2, 126.9, 117.3, 117.1, 11.3. ESIMS: m/z 254
[M ? 1]?. Anal. Calcd. for C15H12FN3: C, 71.13; H, 4.78;
F, 7.50; N, 16.59. Found: C, 71.09; H, 4.85; F, 7.45; N,
16.53.
1
Mp: 197–200 °C. H NMR (400 MHz, CDCl3): d = 7.64
(2H, d, J = 8.4 Hz), 7.39–7.26 (5H, m), 7.09 (2H, d,
J = 8.4 Hz), 2.34 (3H, s). 13C NMR (100 MHz, CDCl3):
d = 153.8, 152.3, 134.1, 133.3, 129.6, 128.8, 128.5, 128.2,
126.8, 123.7, 11.3. ESIMS: m/z 314 [M ? 1]?; Anal.
Calcd. for C15H12BrN3: C, 57.34; H, 3.85; Br, 25.43; N,
13.37. Found: C, 57.29; H, 3.90; Br, 25.38; N, 13.32.
4.3.7 3-Isopropyl-5-methyl-4-phenyl-4H-[1,2,4]triazole
(6g)
Mp: 95–98 °C. 1H NMR (400 MHz, CDCl3): d = 7.58–7.55
(3H, m), 7.23–7.20 (2H, m), 2.78 (1H, septet, J = 7.2 Hz),
2.23 (3H, s), 1.25 (6H, d, J = 7.2 Hz). 13C NMR (100 MHz,
CDCl3): d = 159.4, 151.3, 134.4, 130.0, 129.7, 127.2, 25.3,
21.1, 11.0. ESIMS: m/z 202 [M ? 1]?. Anal. Calcd. for
C12H15N3: C, 71.16; H, 7.51; N, 20.88. Found: C, 71.09; H,
7.57; N, 20.83.
4.3.5 4-(3-Chloro-phenyl)-3-methyl-5-phenyl-4H-
[1,2,4]triazole (6e)
Mp: 188–190 °C. IR (KBr): 3059, 1593, 1484, 1406, 792,
770, 700, cm-1 1H NMR (400 MHz, CDCl3): d =
.
7.51–7.42 (2H, m), 7.40–7.26 (5H, m), 7.23 (1H, d,
J = 2.0 Hz), 7.10 (1H, d, J = 8.0 Hz), 2.35 (3H, s). 13C
NMR (100 MHz, CDCl3): d = 153.7, 152.3, 136.2, 135.7,
131.0, 130.0, 129.6, 128.5, 128.2, 127.4, 126.7, 125.6, 11.3;
ESIMS: m/z 270 [M ? 1]?. Anal. Calcd. for C15H12ClN3: C,
66.79; H, 4.48; Cl, 13.14; N, 15.58. Found: C, 66.73; H, 4.54;
Cl, 13.10; N, 15.54.
4.3.8 3,5-Dimethyl-4-phenyl-4H-[1,2,4]triazole (6h)
Mp: 234–236 °C. 1H NMR (400 MHz, CDCl3): d =
7.50–7.34 (5H, m), 2.25 (6H, s). 13C NMR (100 MHz,
CDCl3): d = 151.1, 133.1, 129.6, 129.4, 126.9, 11.0. ESIMS:
m/z 174 [M ? 1]?. Anal. Calcd. for C10H11N3: C, 69.34; H,
6.40; N, 24.26. Found: C, 69.28; H, 6.45; N, 24.21.
4.3.6 4-(4-Fluoro-phenyl)-3-methyl-5-phenyl-4H-
[1,2,4]triazole (6f)
4.3.9 3-Ethyl-4,5-diphenyl-4H-[1,2,4]triazole (6i)
1
Mp: 125–127 °C. 1H NMR (400 MHz, CDCl3):
d = 7.50–7.49 (3H,m), 7.40–7.38 (2H, m), 7.32–7.18 (5H,
Mp: 155–157 °C. H NMR (400 MHz, CDCl3): d = 7.38
(2H, d, J = 7.2 Hz), 7.34–7.25 (5H, m), 7.20 (2H, d,
J = 7.2 Hz), 2.33 (3H, s). 13C NMR (100 MHz, CDCl3):
m), 2.66 (2H, q, J = 8.0 Hz), 1.27 (3H, t, J = 8.0 Hz). 13
C
123

1518
V. Siddaiah et al.
4.3.14 4-(4-Bromo-phenyl)-3-cyclohexyl-5-phenyl-4H-
[1,2,4]triazole (6n)
NMR (100 MHz, CDCl3): d = 157.0, 153.9, 135.0, 130.0,
129.6, 129.3, 128.6, 128.3, 128.2, 127.4, 127.1, 18.9, 11.7.
ESIMS: m/z 250 [M ? 1]?; Anal. Calcd for C16H15N3: C,
77.08; H, 6.06; N, 16.85. Found: C, 77.02; H, 6.12; N,
16.80.
1
Mp: 234–236 °C. H NMR (400 MHz, CDCl3): d = 7.62
(2H, d, J = 8.8 Hz), 7.38–7.25 (5H, m), 7.06 (2H, d,
J = 8.8 Hz), 2.50–2.45 (1H, m), 1.80–1.73 (6H, m),
1.35–1.12 (4H, m). 13C NMR (100 MHz, CDCl3):
d = 159.6, 153.5, 134.1, 133.3, 129.5, 129.2, 128.9, 128.5,
127.0, 123.7, 34.7, 31.6, 26.0, 25.6. ESIMS: m/z 382
[M ? 1]?; Anal. Calcd for C20H20BrN3: C, 62.83; H, 5.27;
Br, 20.90; N, 10.99. Found: C, 62.77; H, 5.32; Br, 20.87; N,
10.94.
4.3.10 4-(4-Bromo-phenyl)-3-ethyl-5-phenyl-4H-
[1,2,4]triazole (6j)
1
Mp: 225–227 °C. H NMR (400 MHz, CDCl3): d = 7.61
(2H, d, J = 6.8 Hz), 7.39-7.27 (5H, m), 7.08 (2H, d,
J = 6.8 Hz), 2.65 (2H, q, J = 7.2 Hz), 1.28 (3H, t,
J = 7.2. Hz). 13C NMR (100 MHz, CDCl3): d = 156.7,
153.8, 134.0, 133.3, 129.6, 128.9, 128.8, 128.5, 128.3,
126.8, 123.7, 18.9, 11.6. ESIMS: m/z 328 [M ? 1]?; Anal.
Calcd for C16H14BrN3: C, 58.55; H, 4.30; Br, 24.35; N,
12.80. Found: C, 58.50; H, 4.36; Br, 24.32; N, 12.75.
4.3.15 3-Pentyl-4,5-diphenyl-4H-[1,2,4]triazole (6o)
Mp: 128–131 °C. 1H NMR (400 MHz, CDCl3): d =
7.51–7.49 (3H, m), 7.41–7.38 (2H, m), 7.32–7.16 (5H, m),
2.63 (2H, t, J = 8.0 Hz), 1.67 (2H, quintet, J = 8.0 Hz),
1.32-1.20 (4H, m), 0.82 (3H, t, J = 8.0 Hz). 13C NMR
(100 MHz, CDCl3): d = 156.1, 153.8, 135.1, 129.9, 129.6,
129.3, 128.3, 128.2, 127.4, 127.2, 31.3, 26.9, 25.2, 22.1,
13.7. ESIMS: m/z 292 [M ? 1]?. Anal. Calcd. for
C19H21N3: C, 78.32; H, 7.26; N, 14.42. Found: C, 78.26; H,
7.34; N, 14.37.
4.3.11 3,4-Diphenyl-5-propyl-4H-[1,2,4]triazole (6k)
Mp: 155–157 °C. 1H NMR (400 MHz, CDCl3): d =
7.51–7.49 (3H, m), 7.39-7.38 (2H, m), 7.32–7.17 (m, 5H),
2.61 (2H, t, J = 8.0 Hz), 1.70 (2H, hexate, J = 8.0 Hz), 0.92
(3H, t, J = 8.0 Hz); 13C NMR (100 MHz, CDCl3):
d = 155.9, 153.8, 135.0, 129.9, 129.5, 129.3, 128.6, 128.3,
127.4, 127.1, 27.2, 20.7, 13.7; ESIMS: m/z 264 [M ? 1]?;
Anal. Calcd for C17H17N3: C, 77.54;H, 6.51; N, 15.96. Found:
C, 77.49; H, 6.58; N, 15.92.
4.3.16 3-Pentyl-5-phenyl-4-p-tolyl-4H-[1,2,4]triazole (6p)
1
Mp: 140–143 °C. H NMR (400 MHz, CDCl3): d = 7.41
(2H, d, J = 8.0 Hz), 7.40–7.21 (5H, m), 7.05 (2H, d,
J = 8.0 Hz), 2.61 (2H, t, J = 8.0 Hz), 1.72–165 (2H, m),
1.30–1.20 (4H, m), 0.83 (3H, t, J = 8.0 Hz). 13C NMR
(100 MHz, CDCl3): d = 156.3, 153.8, 139.7, 132.4, 130.5,
129.2, 128.7, 128.3, 127.1, 126.9, 31.3, 27.0, 25.2, 22.1,
13.7. ESIMS: m/z 306 [M ? 1]?. Anal. Calcd. for
C20H23N3: C, 78.65; H, 7.59; N, 13.76. Found: C, 78.60; H,
7.65; N, 13.70.
4.3.12 4-(4-Bromo-phenyl)-3-phenyl-5-propyl-4H-
[1,2,4]triazole (6l)
1
Mp: 209–212 °C. H NMR (400 MHz, CDCl3): d = 7.63
(2H, d, J = 8.4 Hz), 7.39–7.26 (5H, m), 7.07 (2H, d,
J = 8.0 Hz), 2.60 (2H, t, J = 8.0 Hz), 1.71 (2H, hexate,
J = 8.0 Hz), 0.94 (3H, t, J = 8.0 Hz). 13C NMR (100 MHz,
CDCl3): d = 155.8, 152.9, 132.1, 131.3, 127.6, 127.0, 126.5,
126.4, 124.9, 121.8, 25.3, 18.8, 11.8. ESIMS: m/z 342
[M ? 1]?;Anal.CalcdforC17H16BrN3: C, 59.66; H, 4.71; Br,
23.35; N, 12.28. Found: C, 59.60; H, 4.76; Br, 23.30; N, 12.23.
4.3.17 4-(4-Bromo-phenyl)-3-pentyl-5-phenyl-4H-
[1,2,4]triazole (6q)
Mp: 158–161 °C. IR (KBr): 3036, 2957, 2930, 2860, 1489,
1
1417, 1069, 976, 826, 692, cm-1. H NMR (400 MHz,
4.3.13 3-Cyclohexyl-4,5-diphenyl-4H-[1,2,4]triazole (6m)
CDCl3): d = 7.63 (2H, d, J = 8.8 Hz), 7.39–7.26 (5H, m),
7.07 (2H, d, J = 8.8 Hz), 2.61 (2H, t, J = 8.0 Hz), 1.68
(2H, quintet, J = 8.0 Hz), 1.29–1.20 (4H, m), 0.84 (3H, t,
J = 8.0 Hz). 13C NMR (100 MHz, CDCl3): d = 155.9,
153.7, 134.0, 133.3, 129.5, 129.0, 128.5, 128.3, 126.8,
123.7, 31.3, 26.9, 25.2, 22.1, 13.7. ESIMS: m/z 370
[M ? 1]?. Anal. Calcd. for C19H20BrN3: C, 61.63; H,
5.44; Br, 21.58; N, 11.35. Found: C, 61.57; H, 5.51; Br,
21.53; N, 11.29.
Mp: 147–149 °C. 1H NMR (400 MHz, CDCl3):
d = 7.50–7.47 (3H, m), 7.38-7.36 (2H, m), 7.30–7.17 (5H,
m), 2.52–2.45 (1H, m), 1.86–1.72 (6H, m), 1.34–1.11 (3H,
m). 13C NMR (100 MHz, CDCl3): d = 159.8, 153.6,
135.1, 129.9, 129.6, 129.2, 128.7, 128.4, 128.3, 127.7,
127.3, 34.7, 31.6, 26.0, 25.6. ESIMS: m/z 304 [M ? 1]?;
Anal. Calcd for C20H21N3: C, 79.17; H, 6.98; N, 13.85.
Found: C, 79.12; H, 7.04; N, 13.81.
123

HClO4-SiO2: An Efficient Reusable Catalyst
1519
4.3.18 4-(4-Fluoro-phenyl)-3-pentyl-5-phenyl-4H-
[1,2,4]triazole (6r)
4.3.22 (Z)-3-[4-(4-Fluoro-phenyl)-5-phenyl-4H-
[1,2,4]triazol-3-yl]prop-2-enoic acid (6v)
1
Mp: 125–130 °C. H NMR (400 MHz, CDCl3): d = 7.69
Mp: 200–203 °C. 1H NMR (400 MHz, DMSO-d6):
d = 14.15 (1H, s), 7.40 (2H, d, J = 7.2 Hz), 7.37–7.27
(5H, m), 7.26 (2H, d, J = 7.2 Hz), 6.35 (1H, d,
J = 12.8 Hz), 6.28 (1H, d, J = 12.8 Hz). 13C NMR
(100 MHz, DMSO-d6): d = 168.1, 164.2, 154.8, 151.8,
130.9, 130.0, 129.6, 129.2, 129.1, 128.9, 128.6, 125.0,
121.2, 117.9, 117.7. ESIMS: m/z 308 [M-1]?. Anal. Calcd.
for C17H12FN3O2: C, 66.02; H, 3.91; F, 6.14; N, 13.59.
Found: C, 65.96; H, 3.98; F, 6.10; N, 13.54.
(2H, d, J = 7.6 Hz), 7.33-7.26 (5H, m), 7.19 (2H, d,
J = 7.6 Hz), 2.61 (2H, t, J = 8.0 Hz), 1.67 (2H, quintet,
J = 8.0 Hz), 1.31-1.21 (4H, m), 0.84 (3H, t, J = 8.0 Hz).
13C NMR (100 MHz, CDCl3): d = 164.1, 161.6, 154.8,
153.9, 131.1, 130.1, 129.4, 129.2, 128.5, 128.2, 127.0,
117.3, 117.0, 31.3, 27.0, 25.3, 22.1, 13.8. ESIMS: m/z 310
[M ? 1]?. Anal. Clacd. for C19H20FN3: C, 73.76; H, 6.52;
F, 6.14; N, 13.58. Found: C, 73.71; H, 6.58; F, 6.09; N,
13.52.
4.3.23 (Z)-3-(5-Isopropyl-4-phenyl-4H-[1,2,4]triazol-3-
yl)prop-2-enoic acid (6w)
4.3.19 (Z)-3-(4,5-Diphenyl-4H-[1,2,4]triazol-3-yl)prop-2-
enoic acid (6s)
Mp: 190–192 °C. IR (KBr): 3057, 2979, 1699, 1504, 1445,
1
Mp: 233–236 °C. IR (KBr): 3054, 2920, 1703, 1445, 1203,
1204, 829, 692, cm-1. H NMR (400 MHz, DMSO-d6):
830, 772, 723 cm-1
.
1H NMR (400 MHz, DMSO-d6):
d = 13.94 (1H, s), 7.65–7.62 (3H, m), 7.55–7.53 (2H, m),
6.34 (1H, d, J = 12.8 Hz), 6.22 (1H, d, J = 12.8 Hz), 2.84
(1H, septet, J = 7.2 Hz), 1.18 (6H, d, J = 7.2 Hz). 13C
NMR (100 MHz, DMSO-d6): d = 165.5, 159.4, 149.8,
132.5, 130.2, 130.0, 129.1, 127.6, 120.3, 24.6, 20.7.
ESIMS: m/z 256 [M-1]?. Anal. Calcd. for C14H15N3O2: C,
65.35; H, 5.88; N, 16.33. Found: C, 65.30; H, 5.94; N,
16.27.
d = 14.04 (1H, s), 7.58–7.54 (3H, m), 7.44–7.32 (7H, m),
6.46 (1H, d, J = 12.4 Hz), 6.33 (1H, d, J = 12.4 Hz). 13C
NMR (100 MHz, DMSO-d6): d = 165.9, 153.3, 150.9,
133.5, 130.0, 129.9, 128.5, 128.2, 127.7, 126.2, 120.7.
ESIMS: m/z 290 [M-1]?. Anal. Calcd. for C17H13N3O2: C,
70.09; H, 4.50; N, 14.42. Found: C, 70.03; H, 4.57; N,
14.36.
Acknowledgment We thank the Department of Science and
Technology (DST), New Delhi for financial support (through a pro-
ject SR/FT/CS-052/2008).
4.3.20 (Z)-3-(5-Phenyl-4-p-tolyl-4H-[1,2,4]triazol-3-
yl)prop-2-enoic acid (6t)
Mp: 215–219 °C. 1H NMR (400 MHz, DMSO-d6):
d = 13.99 (1H, s), 7.44–7.30 (7H, m), 7.14 (2H, d,
J = 7.6 Hz), 6.42 (1H, d, J = 12.8 Hz), 6.31 (1H, d,
J = 12.8 Hz), 2.45 (3H, s). 13C NMR (100 MHz, DMSO-
d6): d = 167.1, 154.3, 151.2, 141.5, 131.2, 130.7, 130.1,
128.8, 128.5, 127.3, 126.9, 125.3, 118.0, 21.3. ESIMS: m/
z 304 [M-1]?. Anal. Calcd for C18H15N3O2: C, 70.81; H,
4.95; N, 13.76. Found: C, 70.74; H, 5.03; N, 13.71.
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