The mineral alum: an effective and low-cost heterogeneous catalyst for the successful synthesis of 5-substituted-1H-tetrazoles

Article abstract of DOI:10.1080/24701556.2020.1762220

A simple, efficient, and green procedure for the synthesis of 5-substituted-1H-tetrazoles via [3 + 2] cycloaddition reaction of nitriles with sodium azide is described. The reaction was catalyzed by natural and mesoporous alum nanoparticles (NPs) in DMSO

Full text of DOI:10.1080/24701556.2020.1762220

Inorganic and Nano-Metal Chemistry
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The mineral alum: an effective and low-cost
heterogeneous catalyst for the successful
synthesis of 5-substituted-1H-tetrazoles
Azam Karimian, Nahid Emarloo & Samira Salari
To cite this article: Azam Karimian, Nahid Emarloo & Samira Salari (2020): The mineral alum:
an effective and low-cost heterogeneous catalyst for the successful synthesis of 5-substituted-1H-
tetrazoles, Inorganic and Nano-Metal Chemistry, DOI: 10.1080/24701556.2020.1762220
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INORGANIC AND NANO-METAL CHEMISTRY
https://doi.org/10.1080/24701556.2020.1762220
The mineral alum: an effective and low-cost heterogeneous catalyst
for the successful synthesis of 5-substituted-1H-tetrazoles
Azam Karimiana, Nahid Emarlooa, and Samira Salarib
b
aDepartment of Chemistry, Faculty of Sciences, University of Gonabad, Gonabad, Iran; Department of Environmental Health Engineering,
School of Health, Gonabad University of Medica Sciences, Gonabad, Iran
ABSTRACT
ARTICLE HISTORY
Received 14 January 2020
Accepted 22 April 2020
A simple, efficient, and green procedure for the synthesis of 5-substituted-1H-tetrazoles via [3 þ 2]
cycloaddition reaction of nitriles with sodium azide is described. The reaction was catalyzed by
natural and mesoporous alum nanoparticles (NPs) in DMSO at 140ꢀC. Alum NPs have been pre-
pared as the new catalytic system by heating and calcination of mineral alum in a furnace. Alum
NPs were characterized using FT-IR, BET, SEM-EDS, XRD, and TGA analysis. The results showed that
alum, as an amorphous mineral and natural low-cost heterogeneous catalyst, provides 5-substi-
tuted-1H-tetrazoles easily with high efficiency. Some of the advantages of this method are high
yields of the desired product, short reaction times, the safe catalyst, prevention of using the toxic
metal catalysts, readily accessible of the catalyst, and low-cost heterogeneous catalyst.
KEYWORDS
Safe catalyst;
heterogeneous catalyst;
mineral alum; green
method; nanopar-
ticles; tetrazoles
Introduction
achievement, hard reaction conditions, and difficulty in
work up.
In the recent decades, the importance of tetrazoles synthesis
has been considered due to a great range of their usage in
medicinal,[1–4], material sciences,[5] coordination chemis-
try,[6] and known as practical heterocyclic compounds in
synthetic organic chemistry.[7,8] Heterocycles containing
tetrazole moiety have exhibited biological activities such as
antiulcer,[9] antiviral,[4,10] anti-inflammatory,[11,12] and anti-
fungal[13,14] properties. Accordingly, it is essential to develop
the synthetic method of obtaining 5-substituted 1H-tetra-
zoles. For this purpose, many synthetic procedures have
been reported for the synthesis of 5-substituted 1H-tetra-
zoles. The commonly employed method involves the
[3 þ 2]-cycloaddition reaction between nitriles and azides.
Other routes for the synthesis of these compounds including
the use of thioamides, imidoyl chlorides, oximes, heterocu-
mulenes, ketones, amines, alkenes, or isocyanides and in the
presence of azide ion source have also been reported. For
this procedure, numerous catalysts and nano catalysts have
also been employed such as CuI,[15] CuO,[16] Cu2O,[16]
ZnO,[17] CuFe2O4,[18] CuSO4ꢁ5H2O,[19] Fe(OAc)2,[20]
Fe3O4@chitin,[21] Cu–MCM-41,[22] InCl3,[23] AgNO3,[24]
FeCl3–SiO2,[25] ZnCl2,[26] ZrOCl2ꢁ8H2O,[27] B(C6H5)3,[28]
DPPA/DBU,[29] BaWO4,[30] Ln(OTf)3–SiO2,[31] Zn–Cu
alloy,[32] I2/NaHSO4–SiO2,[33] mesoporous ZnS nano-
spheres,[34] COY zeolite,[35] Cuttlebone,[36] P2O5.[37]
Recently, a few researchers have also used microwave heat-
ing to decrease reaction times.[38–42] But, in many of these
ways, there are challenges involving the use of high-cost and
Today, because of significant environmental concerns and
considerable reduction of pollution caused by employing the
metal catalysts and toxic and corrosive reagents, there is a
high demand for the use of metal-free, eco-friendly, green,
and safe synthetic methods for the desired products that
prevent the formation of hazardous environmen-
tal wastes.[36]
Based on the previously mentioned details and also in the
continuation of our research program on the successful syn-
thesis of heterocyclic compounds,[43–-47] we presently decide
to report the mineral alum nanoparticles (NPs) as a new,
green, and natural heterogeneous catalyst with significant
catalytic. The alum is a white, porous, and crystalline double
solid. That is inexpensive, safe, nontoxic, and readily avail-
able. Recently, mineral alum was also used for fluoride
adsorption from aqueous samples.[48]
In this paper, we report a new procedure for the synthe-
sis of 5-substituted 1-H-tetrazoles using porous alum as an
amorphous mineral, new, green, and natural heterogeneous
catalyst with significant catalytic activity.
Then, in the present study, the synthesis of 5-substituted
1H-tetrazoles via the reaction between nitriles and sodium
azide using porous alum NPs as an adsorbent catalyst was
investigated in DMSO. Alum NPs are shown to be an effect-
ive, heterogeneous, and natural catalyst for this cycloadd-
ition reaction. The catalyst employed has some of the
considerable advantages such as, easy availability, low-cost
heterogeneous catalyst, great activity, safe, without any toxic
toxic metals, expensive reagents, long reaction times, low or hazardous reagents, green, and environment-friendly.
CONTACT Azam Karimian
a_karimian87@yahoo.com Department of Chemistry, Faculty of Sciences, University of Gonabad, Gonabad, Iran.
ß 2020 Taylor & Francis Group, LLC

2
A. KARIMIAN ET AL.
The spectral data of some representative 5-substituted-
1H-tetrazoles are as follows:
Experimental section
Materials
5-Phenyl-1H-tetrazole (Table 2, Entry 1). White solid,
FT-IR (KBr, ꢀmax, cmꢃ1): 3125 (N–H), 3044, 2982, 2835,
2766, 2692, 2607, 2557, 1614, 1564, 1486, 1466, 1409, 1254
(N–N ¼ N–), 1164 (C–N), 1056, 988, 784. 1H NMR
(400 MHz, DMSO-d6, ppm): dH 3.49 (br s, 1H, NH), 7.62 (s,
3H, Ar–H), 8.05 (s, 2 H, Ph). MS (EI): m/z (%) 146 [M]þ.
Anal. Calcd. for C7H6N4: C, 57.53; H, 4.14; N, 38.34. Found:
C, 57.52; H, 4.18; N, 38.30.
Materials and all reagents were purchased from Merck and
used without further purification. The mineral alum used
in this study was taken out of mines in northeast Iran.
The melting points of products were determined with an
Electrothermal Type 9200 melting point apparatus. The FT-
IR spectra were recorded on an Avatar 370 FT-IR Thermal
Nicolet spectrometer. BET analysis was carried out on a
Belsorp mini II (Microtrac Bel Corp). TGA analysis was car-
ried out on a Shimadzu Thermogravimetric Analyzer (TG-
50) in the temperature range of 35–900 ꢀC at a heating rate
of 5 ꢀC/min under air atmosphere. TEM was performed
with a Leo 912 AB microscope (Zeiss, Germany) with an
accelerating voltage of 120 kV. SEM images were also
5-(4-Bromophenyl)-1H-tetrazole (Table 2, Entry 2).
Yellow solid, FT-IR (KBr, ꢀmax, cmꢃ1): 3330 (N–H), 3089,
2996, 2845, 2730, 1652, 1605, 1483, 1278 (N–N ¼ N–), 1157
1
(C–N), 1054, 830. H NMR (400 MHz, DMSO-d6, ppm): dH
7.76–7.97 (m, 4H, Ar–H). MS (EI): m/z (%) 226 [Mþ þ 2],
224 [Mþ]. Anal. Calcd. for C7H5BrN4: C, 37.36; H, 2.24; N,
recorded using Leo 1450 VP scanning electron microscope 24.90. Found: C, 37.71; H, 2.83; N, 24.60.
operating at an acceleration voltage of 20 kV. The crystal
5-(4-Nitrophenyl)-1H-tetrazole (Table 2, Entry 4).
structure of catalyst was analyzed by XRD using a D8 Yellow solid, FT-IR (KBr, ꢀmax, cmꢃ1): 3440 (N–H), 3334,
ADVANCE-Bruker diffractometer operated at 40 kV and 3110, 2975, 2819, 1633, 1488, 1341, 1242 (N–N ¼ N–), 1144
1
1
1
30 mA utilizing Cu Ka radiation (l = 0. A). The H NMR
(C–N), 995. H NMR (400 MHz, DMSO-d6, ppm): dH 3.20
4
spectra were recorded on a Brucker Avance 400 MHz
instrument in [d6] DMSO and CDCl3. Mass spectra were
recorded with a CH7AV aria mat Bremen instrument
at 70 eV. Elemental analyses were performed on a Thermo
Finnigan Flash EA microanalyzer.
(br s, 1H, NH), 8.30–8.33 (m, 2H, Ar–H), 8.45–8.48 (m, 2H,
Ar–H). MS (EI): m/z (%) 191 [M]þ. Anal. Calcd. for
C7H5N5O2: C, 43.98; H, 2.64; N, 36.64. Found: C, 43.70; H,
2.83; N, 36.65.
5-m-Tolyl-1H-tetrazole (Table 2, Entry 6). White solid,
FT-IR (KBr, ꢀmax, cmꢃ1): 3303 (N–H), 3121, 2980, 2870,
1
2612, 1605, 1486, 1250 (N–N ¼ N–), 1150 (C–N), 890. H
Preparation of the mineral alum NPs
NMR (400 MHz, DMSO-d6, ppm): dH 2.50 (s, 3H, CH3),
7.42 (d, J ¼ 7.6 Hz, 1H, Ar–H), 7.47–7.52 (m, 1H, Ar–H),
7.83–7.89 (m, 2H, Ar–H), MS (EI): m/z (%): 160 [M]þ.
Anal. Calcd. for C8H8N4: C, 59.99; H, 5.03; N, 34.98. Found:
C, 59.90; H, 5.05; N, 35.02.
The mineral alum (5 g) was crushed in a mortar, washed
with distilled water, and dissolved in 100 mL deionized
water under vigorous stirring at 80 ꢀC temperature. After
5 h, NaOH solution (1 N) was added dropwise into the
solution until the pH of the solution was adjusted to 8. The
stirring of the solution remained for 2 h at 80 ꢀC tempera-
ture. After that, the solution was cooled. The resulting
white precipitate was then collected by centrifugation
5-(4-Methoxyphenyl)-1H-tetrazole14 (Table 2, Entry 7).
White solid, FT-IR (KBr, ꢀmax, cmꢃ1) 3300 (N–H), 2930,
2650, 1620, 1445, 1278 (N–N ¼ N–), 1184 (C–N), 1034, 752.
1H NMR (400 MHz, DMSO-d6, ppm): dH 4.22 (s, 3H,
(4000–6000 rpm, 20 min) and decantation, followed by OMe), 7.30 (t, J ¼ 7.6 Hz, 2H, Ar–H), 7.35 (t, J ¼ 7.6 Hz, 2H,
washing three times with deionized water and drying Ar–H). MS (EI): m/z (%) 175 [M]þ. Anal. Calcd. for
in vacuo at 70 ꢀC for 2 h. Next, the resulting particles were C8H8N4O: C, 54.54; H, 4.58; N, 31.80. Found: C, 54.60; H,
placed in a furnace and calcined at 400 ꢀC for 4 h. At last,
4.83; N, 31.75.
an amorphous powder remained.
5-(3,5-Dimethoxyphenyl)-1H-tetrazole (Table 2, Entry
8). White solid, FT-IR (KBr, ꢀmax, cmꢃ1): 3130 (N–H),
3101, 2942, 2758, 1605, 1559, 1431, 1288 (N–N ¼ N–), 1166
The typical procedure for the preparation of 5-phenyl-
1H-tetrazole in the presence of mineral alum NPs
1
(C–N), 1054, 846. H NMR (400 MHz, DMSO-d6, ppm): dH
3.85 (s, 6H, –OMe), 6.72 (t, J ¼ 2.2 Hz, 1H, Ar–H), 7.22 (d,
J ¼ 2.2 Hz, 2H, Ar–H), 16.90 (br s, 1H, NH), MS (EI) m/z
(%) 206 [M]þ. Anal. Calcd. for C9H10N4O2: C, 52.42; H,
4.89; N, 27.17. Found: C, 52.42; H, 4.85; N, 27.20.
5-(Naphthalen-1yl)-1H-tetrazole (Table 2, Entry 11).
White solid, FT-IR (KBr, ꢀmax, cmꢃ1): 3412 (N–H), 3050,
2721, 1625, 1525, 1389, 1257 (N–N ¼ N–), 1131 (C–N),
965, 864, 1H NMR (400 MHz, DMSO-d6, ppm): dH
7.65–7.73 (m, 3H, Ar–H), 7.98–8.0 (m, 1H, Ar–H),
8.02–8.08 (m, 1H, Ar–H), 8.12–8.19 (m, 1H, Ar–H),
8.57–8.60 (m, 1H, Ar–H), MS (EI): m/z (%) 196 [M]þ.
A mixture of benzonitrile (1 mmol), sodium azide (1 mmol),
and alum NPs (0.05 g) in DMSO (5 mL) was stirred at
140 ꢀC for 30 min. The progress of the reaction was carefully
monitored by TLC (thin layer chromatography). After com-
pletion of the reaction, the reaction mixture was cooled, and
the catalyst was filtered. The filtrate was treated with HCl
(4 N, 10 mL) and then with ethyl acetate (2 ꢂ 10 mL). The
resulting organic layer was washed with distilled water and
extracted, then was dried over anhydrous sodium sulfate,
and concentrated to give the crude solid crystalline 5-phe-
nyl-1H-tetrazole. The product was recrystallized from n-hex- Anal. Calcd. for C11H8N4: C, 67.34; H, 4.11; N, 28.55.
ane/ethyl acetate (1:1) to obtain white crystals. Found: C, 67.35; H, 4.10; N, 28.55.

INORGANIC AND NANO-METAL CHEMISTRY
3
Scheme 1. Synthesis of different structurally 5-substituted-1H-tetrazoles in the
presence of alum NPs.
Results and discussion
Characterization of alum NPs
Alum used in this study was taken out of local mines in the
northeast of Iran. Mineral alum is a natural material with
high porosity, composed of Al, S, O elements. Following our
attention in the synthesis of heterocycles, we thought about
the possibility of using alum as a green catalyst to produce
5-substituted-1H-tetrazoles by [3 þ 2] cycloaddition reaction
of nitriles with sodium azide (Scheme 1).
Figure 1. The FT-IR spectrum of alum NPs.
For the preparation of alum NPs, the extracted alum was pow-
dered, washed with distilled water, and dissolved in deionized
water at 80 ꢀC temperature. After that, the NaOH solution was
added dropwise into the solution until the pH of the solution
reached 8. The resulting white precipitate was then collected and
washed with deionized water and dried in vacuo and calcined at
400 ꢀC, and at last, an amorphous powder was obtained.
The FT-IR spectrum of alum NPs is shown in Figure 1.
In general, the FT-IR pattern of calcined powders exhibited
an absorption band at 3454 cmꢃ1, which belongs to the
stretching vibration of O–H groups in the absorbed water,
and a weak band at 1628 cmꢃ1, which are assigned to the
deformation vibration of water molecules. Additionally, an
absorption band at 600–677 cmꢃ1 can be attributed to the
vibrations of the (Al–O–Al) group. The bands at 1150 and
1250 are assigned to the (SO42ꢃ) vibration.[49]
Figure 2 shows the nitrogen adsorption–desorption isotherms
and the pore size distribution of alum NPs in air at 300 ꢀC tem-
perature. As shown in Figure 2, the sample has type III adsorp-
tion isotherm with a H3-type hysteresis loop. According to
IUPAC classification, type H3 hysteresis is usually found on sol-
ids with a very wide distribution of pore size [50]. The BET sur-
face area is 0.86 (m2/g) and average pore diameter is 7–9 (nm).
The composition, morphology, and size of the prepared
NPs were analyzed by SEM and TEM (Figure 3). It is evi-
dent from the SEM image (Figure 3(a)) that the alum NPs
are constructed from a random agglomeration of particles,
and the shape of NPs is spherical.
Figure 2. The nitrogen absorption–desorption isotherms of alum NPs in air at
temperatures 130 ꢀC, the blue curve presents adsorption and orange curve pre-
sent desorption processes.
Figure 6 shows the typical thermogravimetric analysis
(TGA) curve of the alum NPs to determine the weight loss
for nanocatalyst. As shown in Figure 6, as the temperature
increases a weight loss is observed. Initially, the diagram
slope is almost constant and horizontal, this shows that the
NPs are pure with a little moisture. The weight loss percent
in this step was 4–5, mainly due to the loss of water. At
higher temperature (in the range of 450–650 ꢀC), thermal
dihydroxylation process has occurred and the weight loss
observed is about 3–4%. The third weight loss (18–15% in
the range of 700–900 ꢀC) is attributed to the desulphation
process related to the removal of all sulfate ions. These mass
losses correspond principally to the removal of the NH3 gas
and SO2. As shown in the results, the used alum NPs have
thermal stability with heating to 640–680 ꢀC. At higher tem-
perature, the nanocatalyst decomposed completely.[51]
The TEM micrograph of the alum NPs shown in Figure
3(b) revealed that the sample has a full mesoporous struc-
ture. As evident from SEM image, the average size of the
pores is almost in agreement with the data obtained from
the nitrogen adsorption–desorption analysis.
Also, the EDS analysis of alum NPs indicated the pres-
ence of Al, O, and S elements in the chemical composition
of the alum NPs (Figure 4).
The structure of alum NPs was also analyzed by XRD
spectroscopy. As shown in Figure 5, the alum NPs yielded a
diffuse pattern. The broadening and the weak peaks inten-
sity could be due to the amorphous and non-crystalline
structure of alum NPs that may be produced during drying
process at 400 ꢀC.
The catalytic application of alum NPs for the synthesis
of 5-substituted 1H-tetrazoles
The formation of 5-substituted 1H-tetrazoles from aryl
nitriles and NaN3 was reported with alum NPs. To

4
A. KARIMIAN ET AL.
Figure 3. (a) SEM image of alum NPs. (b) TEM image of alum NPs.
Figure 4. The EDS analysis of alum NPs.
determine the optimum conditions, the reaction between solvents tested, the best result has been obtained at DMSO
benzonitrile with sodium azide was explored as a model solvent for [3 þ 2] cycloaddition reaction. Other solvents,
reaction. Different amount of used catalyst, various solvents, like H2O, DMF, and CH3CN gave the desired product in
and temperatures were examined to optimize the reaction the low yield, despite prolonged reaction time. In DMF solv-
conditions (Table 1). In the absence of catalyst, 5-phenyl- ent, 5-phenyl1H-tetrazole was produced in 100% yield after
1H-tetrazole was obtained at DMSO for 10 h in 40% yield a long period of time (Table 1, entry 6).
(Table 1, entry 1). Various solvents were examined for
At lower reaction temperature (120 ꢀC and 110 ꢀC, Table
cycloaddition reaction in the presence of alum NPs (Table 1, 1, entries 7–8), the reaction was progressed in low yield. To
entries 2–6). As shown in Table 1, among the different study the effect of catalyst loading, the formation of 5-

INORGANIC AND NANO-METAL CHEMISTRY
5
Figure 5. The XRD patterns of alum MNPs.
Figure 6. Thermogravimetric analysis curve of alum in air atmosphere (heating rate of 5 ꢀC/min from 37.5 ꢀC to 900 ꢀC in air).
Table 1. Synthesis of 5-phenyl-1H-tetrazole in different conditions (in various solvents, in the presence of varying amounts of alum,
at different temperatures, and in the presence of different catalysts).
Entry
Solvent
Catalyst
Catalyst loading (g)
Time (h)
Temp. (ꢀC)
Yield (%)
1
2
3
4
5
6
7
8
DMSO
DMSO
H2O
DMF
CH3CN
DMF
DMSO
DMSO
DMSO
DMSO
DMSO
–
–
10
1
3
3
3
10
1
1
1
3
140
140
Reflux
120
Reflux
120
120
110
140
140
40
100
55
50
13
100
90
75
100
70
40
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Alum NPs
Al2(SO4)3
0.05
0.05
0.05
0.05
0.05
0.05
0.05
0.07
0.03
0.05
9
10
11
10
140
phenyl-1H-tetrazole was carried out in DMSO at 140 ꢀC in cause the higher rate of reaction (Table 1, entry 9),
the presence of 0.05 g, 0.07 g, and 0.03 g of the catalyst. while the lower catalyst has decreased the reaction yield
According to this investigation, the best result has
been obtained at 0.05 g of the catalyst and DMSO solvent
even after longer reaction time (Table 1, entry 10).
Based on the results obtained from Table 1 (entries 2),
(Table 1, entry 2). Increasing the catalyst loading did not components and matrix of NPs play an essential role in

6
A. KARIMIAN ET AL.
Table 2. Synthesis of different structurally 5-substituted-1H-tetrazoles in the presence of alum (0.05 g) in DMSO at 140 ꢀC.
Entry
1
Substrate
Product
Time (min)
60
Yield (%)
100
Mp (ꢀC)
Lit. Mp (ꢀC)
214[29]
215–216
2
3
4
70
50
50
95
265–266
268–270[52]
261–262[36]
218–219[36]
100
100
261
216–218
5
6
120
100
90
90
252
251–252[22]
149–150
151–152[53]
7
8
1.5 h
88
85
230–231
205–207
229–230[54]
3 h
204–205[36]
9
2 h
85
80
234–236
278–280
234–235[36]
10
2.5 h
282–284[55]
(continued)

INORGANIC AND NANO-METAL CHEMISTRY
7
Table 2. Continued.
Entry
11
Substrate
Product
Time (min)
2.5 h
Yield (%)
90
Mp (ꢀC)
Lit. Mp (ꢀC)
212–214[54]
214–215
12
10 h
Trace
96
95–96[36]
Scheme 2. Proposed mechanism for the synthesis of 5-substituted-1H-tetrazoles in the presence of alum NPs.
catalytic activity. To show the effect of alum NPs as an effi- converted into their corresponding tetrazoles with longer
cient heterogeneous catalyst, synthesis of the model com- reaction time (Table 2, entries 5–10).
Further, the alkyl nitrile such as 4-methylpentanenitrile,
in the presence of alum NPs reacted smoothly to give the
product in trace yield after 10 h (Table 2, entry 12).
Then, useful features of the presented method include:
availability, inexpensive, and environmentally amiable of
catalyst, prevention of using the dangerous and harmful
metals, high activity and reusability of catalyst, high yields
of products, high reaction rate, that make this method as a
sufficient process for the synthesis of 5-substituted-
pound of 5-phenyl-1H-tetrazole was also investigated using
Al2(SO4)3. The results are given in Table 1 and as shown, at
the same reaction condition, 100% conversion was obtained
after 1 h in the presence of alum NPs at 140 ꢀC (entry 2).
But the yield of the reaction was not high by using the
Al2(SO4)3 as the catalyst despite longer reaction time (entry
11). Therefore, alum NPs can be introduced as an effective,
heterogeneous, and natural catalyst for the synthesis of 5-
substituted 1H-tetrazoles derivatives.
Then, synthesis of different structurally 5-substituted-1H- 1H-tetrazoles.
All synthesized compounds were distinguished by 1H
tetrazoles in the presence of 0.05 g of alum at 140 ꢀC was
done (Table 2). The reaction times and product yields of
aromatic nitriles bearing electron withdrawing and electron
donating groups showed a significant difference.
Among the various nitriles, benzonitrile and the aromatic
nitriles containing electron-withdrawing substituents such as
–Br, –Cl, –NO2 gave the corresponding tetrazoles with
excellent yields in short reaction time (Table 2, entries 1–4).
NMR, FT-IR, mass spectra, and also by comparison of their
melting points with the data reported in the literature. For
example, FT-IR spectroscopy of all products showed absorp-
tion bands at 3100–3400 cmꢃ1 (N–H), and bands at
1000–1300 cmꢃ1 due to tetrazole ring. Any absorption band
at 2240 cmꢃ1 related to CꢄN group was not observed.
A plausible mechanism is shown in Scheme 2. It has
The aromatic rings with electron-donating groups (CH3, been suggested that the cycloaddition of nitriles and sodium
ꢃOCH3, ꢃOCH2CH3, and –NMe2) were successfully azide occurs through adsorption of nitrile by the

8
A. KARIMIAN ET AL.
Table 3. Comparison of various catalysts for the synthesis of 5-phenyl-1H-tetrazole.
Entry
Catalyst
Conditions: solvent/temperature/time
Yield (%)
1
2
3
4
5
6
7
8
Mesoporous ZnS nanospheres[34]
DMF, 120 ꢀC, 36 h
DMF, 120 ꢀC, 14 h
DMSO, 110 ꢀC, 20 min
Solvent-free, 110 ꢀC, 20 min
DMSO, 130 ꢀC, 1 h
DMF, 120–130 ꢀC, 12 h
DMF, 120 ꢀC, 12 h
DMF, 120 ꢀC, 15 h
Toluene, reflux, 16 h
DMF, reflux, 4 h
96
90
98
95
95
84
92
92
93
90
83
90
98
96
90
100
COY zeolite[35]
Cuttlebone[36]
Fe3O4@chitin[21]
CAES[56]
Zn/Al hydrocalcite[57]
[18]
CuFe2O4
[23]
InCl3
9
DPPA/DBU[29]
[37]
10
11
12
13
14
15
16
P2O5
[24]
AgNO3
DMF, 120 ꢀC, 5 h
TEA. HCl[54]
Toluene, 100 ꢀC, 24 h
DMSO, 120 ꢀC, 1 h
H2O, 85 ꢀC, 1 h
Cu(II)/Fe3O4@APTMS-DFX[58]
[t-Bu2Sn(OH)(H2O)]22þ2OTfꢃ[59]
[55]
ChCl–ZnCl2
140 ꢀC, 30 min
Alum(present work)
DMSO, 120 ꢀC, 1 h
Figure 7. Synthesis of 5-phenyl-1H-tetrazole in the presence of reused alum nanoparticles.
mesoporous alum that accelerated the azide addition to cooled, and the catalyst was filtered, washed with 100 mL
distilled water, and calcined at 400 ꢀC for 4 h. Then, reused
in later reactions with a similar condition. The nanocatalyst
was successfully applied for four times in the new reactions
without significant loss in the product yield (Figure 7).
nitrile. Additionally, the coordination of nitrile compound
with surface cations of alum NPs can form complex I, which
helps for the cyclization step via increasing the electrophilic-
ity of nitrile group. The [3 þ 2] cycloaddition between the
CꢄN bond of nitrile compound and azide ion occurs
instantly to form the intermediate II. After removing the
catalyst by simple filtration and acidic work-up, affords III
and IV tautomers. The more stable tautomer IV (5-substi-
tuted-1H-tetrazole) was as significant product.
In continuation, we did a comparative study of reported
method with the other catalysts recently reported for the
synthesis of tetrazole derivatives in the literature. As it is
found (Table 3), the alum is a more effective catalyst than
many of the methods reported in the literature for
this reaction.
Conclusion
In summary, we introduced alum NPs as a green, efficient,
and natural heterogeneous catalyst for the facile synthesis of
5-substituted 1H-tetrazoles via [3 þ 2] cycloaddition reaction
between nitriles and sodium azide in DMSO. The advan-
tages of this investigation are short reaction times, high
yields of the desired product, low-cost heterogeneous cata-
lyst, prevention of using the dangerous and harmful metals,
easily available, green, and environmental friendly catalyst.
Recycling of catalyst
References
The reusability of alum nanocatalyst was also studied. For
this purpose, the reaction of benzonitrile and sodium azide
in the presence of alum was checked. In this procedure,
after completion of the reaction, the reaction mixture was
1. Kumar, C. N. S. S. P.; Parida, D. K.; Santhoshi, A.; Kota, A. K.;
Sridhar, B.; Rao, V. Synthesis and Biological Evaluation of
Tetrazole Containing Compounds as Possible Anticancer Agents.
Med. Chem. Commun. 2011, 2, 486–492.

INORGANIC AND NANO-METAL CHEMISTRY
9
2. DolusꢀIcꢁ, E.; Larrieu, P.; Moineaux, L.; Stroobant, V.; Pilotte, L.;
Catalyst Free and Copper Catalyzed Reactions of
Cyanochromenes and Sodium Azide. Tetrahedron 2013, 69,
1841–1848. DOI: 10.1016/j.tet.2012.12.062.
Colau, D.; Pochet, L.; Van den Eynde, Bt.; Masereel, Bernard;
ꢁ ꢁ
€
Wouters, Johan; Frederick, Raphael. 3-Dioxygenase (TDO)
Inhibitors. 3-(2-(Pyridyl)Ethenyl)Indoles as Potential Anticancer 16. Jin, T.; Kitahara, F.; Kamijo, S.; Yamamoto, Y. Copper-Catalyzed
Immunomodulators. J. Med. Chem. 2011, 54, 5320–5334. DOI:
10.1021/jm2006782.
3. Modarresi-Alam, A. R.; Khamooshi, F.; Rostamizadeh, M.;
Synthesis of 5-Substituted 1H-Tetrazoles via the [3 þ 2]
Cycloaddition of Nitriles and Trimethylsilyl Azide. Tetrahedron
Lett. 2008, 49, 2824–2827. DOI: 10.1016/j.tetlet.2008.02.115.
Keykha, H.; Nasrollahzadeh, M.; Bijanzadeh, H. R.; Kleinpeter, E. 17. Kantam, M. L.; Shiva Kumar, K. B.; Sridhar, C. Nanocrystalline
Dynamic 1H NMR Spectroscopic Study of the Restricted S–N
Rotation in Aryl-N-(Arylsulfonyl)-N-
(Triphenylphosphoranylidene)Imidocarbamates. J. Mol. Struct.
2007, 841, 61–66. DOI: 10.1016/j.molstruc.2006.11.058.
ZnO as an Efficient Heterogeneous Catalyst for the Synthesis of
5-Substituted 1H-Tetrazoles. Adv. Synth. Catal. 2005, 347,
1212–1214. DOI: 10.1002/adsc.200505011.
18. Akula, R. K.; Adimulam, C. S.; Gangaram, S.; Kengiri, R.; Banda,
N.; Pamulaparthy, S. R. CuFe2O4 Nanoparticle Mediated Method
for the Synthesis of 5-Substituted 1H-Tetrazoles from (E)-
Aldoximes. LOC 2014, 11, 440–445. DOI: 10.2174/
1570178611666140210213157.
4. Vieira, E.; Huwyler, S.; Jolidon, S.; Knoflach, F.; Mutel, V.;
Wichmann, J. 9H-Xanthene-9-Carboxylic Acid [1,2,4]Oxadiazol-
3-yl- and (2H-Tetrazol-5-yl)-Amides as Potent, Orally Available
mGlu1 Receptor Enhancers. Bioorg. Med. Chem. Lett. 2005, 15,
4628–4631. DOI: 10.1016/j.bmcl.2005.05.135.
19. Akhlaghinia, B.; Rezazadeh, S.
A Novel Approach for the
5. Hiskey, M.; Chavez, D. E.; Noud, D. C.; Son, S. F.; Berghout,
H. L.; Bome, C. A. Progress in High-Nitrogen Chemistry in
Synthesis of 5-Substituted-1H-Tetrazoles. J. Braz. Chem. Soc.
2012, 23, 2197–2203. DOI: 10.1590/S0103-50532013005000005.
Explosives, Propellants and Pyrotechnics. Proc. Int. Pyrotech. 20. Bonnamour, J.; Bolm, C. Iron Salts in the Catalyzed Synthesis of
Semin. 2000, 27, 3–14.
5-Substituted 1H-Tetrazoles. Chem. Eur. J. 2009, 15, 4543–4545.
6. Frija, L. M. T.; Fausto, R.; Loureiro, R. M. S.; Cristiano, M. L. S.
DOI: 10.1002/chem.200900169.
Synthesis and Structure of Novel Benzisothiazole-Tetrazolyl 21. Zarghani, M.; Akhlaghinia, B. Magnetically Separable
Derivativesfor Potential Application as Nitrogen Ligands. J. Mol.
Cat. A Chem. 2009, 305, 142–146. DOI: 10.1016/j.molcata.2008.
12.007.
Fe3O4@Chitin as an Eco-Friendly Nanocatalyst with High
Efficiency for Green Synthesis of 5-Substituted-1H-Tetrazoles
under Solvent-Free Conditions. RSC Adv. 2016, 6, 31850–31860.
DOI: 10.1039/C6RA07252F.
7. Cantillo, D.; Gutmann, B.; Kappe, C. O. Mechanistic Insights on
Azide-Nitrile Cycloadditions: On the Dialkyltin Oxide- 22. Abdollahi-Alibeika, M.; Moaddeli, A. Efficient Iodine-Catalyzed
Trimethylsilyl Azide Route and a New Vilsmeier-Haack-Type
Organocatalyst. J. Org. Chem. 2012, 77, 10882–108090. DOI: 10.
1021/ja109700b.
One Pot Synthesis of Highly Functionalised Pyrazoles in Water.
New. J. Chem. 2014, 38, 3102–3111. DOI: 10.1039/C3NJ01149F.
23. Guggilapu, Sravanthi; Prajapti, Santosh; Nagarsenkar, Atulya;
Gupta, Keshav; Babu, Bathini. Indium(III) Chloride Catalyzed
Synthesis of 5-Substituted1H-Tetrazoles from Oximes and
Sodium Azide. Synlett 2016, 27, 1241–1244. DOI: 10.1055/s-
0035-1561559.
8. Kumarn, Sirirat; Shaw, David M.; Ley, StevenV. A Highly
Selective, Organocatalytic Route to Chiral 1,2-Oxazines from
Ketones. Chem. Commun. 2006, 66, 3211–3213. DOI: 10.1039/
b606338a.
9. Hayao, S.; Havera, H. J.; Strycker, W. G.; Leipzig, T. J.; 24. Mani, A. K.; Singh, S. K.; Wasthi, A. AgNO3 Catalyzed Synthesis
Rodriguez, R. Synthesis, In Vitro Antifungal and Antitubercular
Evaluation of Novel Amino Pyrimidines Based Tetrazole
Derivatives. J. Med. Chem. 1967, 10, 400–402. DOI: 10.1021/
jm00315a025.
of 5-Substituted-1H-Tetrazole via [3 þ 2] Cycloaddition of
Nitriles and Sodium Azide. Tetrahedron Lett. 2014, 55,
1879–1882. DOI: 10.1016/j.tetlet.2014.01.117.
25. Nasrollahzadeh, Mahmoud; Bayat, Yadollah; Habibi, Davood;
10. Song, W. H.; Liu, M. M.; Zhong, D. W.; Zhu, Y. L.; Bosscher,
M.; Zhou, L.; Ye, D. Y.; Yuan, Z. H. Tetrazole and Triazole as
Bioisosteres of Carboxylic Acid: Discovery of Diketo Tetrazoles
and Diketo Triazoles as Anti-HCV Agents. Bioorg. Med. Chem.
Lett. 2013, 23, 4528–4531. DOI: 10.1016/j.bmcl.2013.06.045.
Moshaee, Saeed. FeCl3–SiO2 as a Reusable Heterogeneous
Catalyst for the Synthesis of 5-Substituted 1H-Tetrazoles via
[2 þ 3] Cycloaddition of Nitriles and Sodium Azide.
Tetrahedron Lett. 2009, 50, 4435–4438. DOI: 10.1016/j.tetlet.
2009.05.048.
11. Hallinan, E. Ann; Tsymbalov, Sofya; Dorn, Clifford R.; Pitzele, 26. Vorona, S.; Artamonova, T.; Zevatskii, Y.; Myznikov, L. An
Barnett S.; Hansen, Donald W.; Moore, William M.; Jerome,
Gina M.; Connor, Jane R.; Branson, Linda F.; Widomski,
Deborah L.; et al. Synthesis and Biological Characterization of L-
Improved Protocol for the Preparation of 5-Substituted
Tetrazoles from Organic Thiocyanates and Nitriles. Synthesis
2014, 46, 781–486. DOI: 10.1055/s-0033-1340616.
N(6)-(1-Iminoethyl)Lysine 5-Tetrazole-Amide, a Prodrug of a 27. Gowd, M. R. M. B.; Pasha, M. A. A Versatile and an Efficient
Selective iNOS Inhibitor. J. Med. Chem. 2002, 45, 1686–1689.
DOI: 10.1021/jm010420e.
Synthesis of 5-Substituted-1H- Tetrazoles. J. Chem. Sci. 2011,
123, 75–79. DOI: 10.1007/s12039-011-0065-8.
12. Rajib, K. P.; Hasina, Y.; Lutfun, N.; Bidyut, K. D.; Abul, 28. Prajapti, S. K.; Nagarsenkar, A.; Babu, B. N. An Efficient
K. A. C.; Joydeb, K.; Sitesh, C. B.; Satyajit, D. S. Synthesis of 5,6-
Dichloroindan-1-Acids and Their Tetrazolyl Derivatives as
Analgesic and Anti-Inflammatory Agents. Med. Chem. 2012, 8,
874–882. DOI: 10.2174/157340612802084234.
Synthesis of 5-Substituted 1H-Tetrazoles via B(C”6F”5)”3
Catalyzed [3 þ 2] Cycloaddition of Nitriles and Sodium Azide.
Tetrahedron Lett. 2014, 55, 3507–3510. DOI: 10.1016/j.tetlet.
2014.04.089.
13. Upadhayaya, R. S.; Sinha, N.; Jain, S.; Kishore, N.; Chandra, R.; 29. Ishihara, K.; Kawashima, M.; Shioiri, T.; Matsugi, M. Synthesis
Arora, S. K. Synthesis of 5,6-Dichloroindan-1-Acids and Their
Tetrazolyl Derivatives as Analgesic and Anti-Inflammatory
Agents. Bioorg. Med. Chem. 2004, 12, 2225–2238. DOI: 10.1016/
j.bmc.2004.02.014.
of 5-Substituted 1H-Tetrazoles from Aldoximes Using Diphenyl
Phosphorazidate. Synlett 2016, 27, 2225–2228. DOI: 10.1055/s-
0035-1561668.
30. He, J.; Li, B.; Chen, F.; Xu, Z.; Yin, G. Novel Heterogeneous
Catalysts for the Synthesis of 5-Substituted 1H-Tetrazoles. J. Mol.
Catal. A 2009, 304, 135–138. DOI: 10.1016/j.molcata.2009.01.037.
14. Veeraswamy, B.; Santhosh, K. G.; Sambasiva Rao, P.;
Kurumurthy, C.; Narsaiah, B. Optically Active Antifungal Azoles:
Synthesis and Antifungal Activity of (2R,3S)-2-(2,4- 31. Meshram, G. A.; Deshpande, S. S.; Wagh, P. A.; Vala, V. A.
Difluorophenyl)-3-(5-[2-[4-Aryl-Piperazin-1-yl]-Ethyl]-Tetrazol-
2-yl/1-yl)-1-[1,2,4]-Triazol-1-yl-Butan-2-ol. J. Heterocyclic Chem.
2014, 51, 1073–1077. DOI: 10.1016/j.bmc.2004.02.014.
Silica Supported Lanthanum Triflate Mediated Synthesis of 5-
Substituted-1H Tetrazoles. Tetrahedron Lett. 2014, 55,
3557–3560. DOI: 10.1016/j.tetlet.2014.04.101.
15. Gawande, S. D.; Raihan, M. J.; Zanwar, M. R.; Kavala, V.; 32. Aridoss, G.; Laali, K. K. Highly Efficient Synthesis of 5-
Janreddy, D.; Kuo, C.; Chen, M.; Kuo, T.; Yao, C. The Study of Substituted 1H-Tetrazoles Catalyzed by Cu-Zn Alloy

10
A. KARIMIAN ET AL.
Nanopowder, Conversion into 1,5- AND 2,5-Disubstituted 46. Karimian, A.; Eshghi, H.; Bakavoli, M.; Shiri, A.;
Tetrazoles, and Synthesis and NMR Studies of New Tetrazolium
Ionic Liquids. Eur. J. Org. Chem. 2011, 2011, 6343–6355. doi:10.
1002/ejoc.201100957.
Saadatmandzadeh, M.; Asghari, T.; Moradi, H. Dipyrimido[4,5-
b:5,4-e][1,4]Thiazine: Synthesis and Their Enzyme Inhibitory
Activity Assessment on Soybean 15-Lipoxygenase. J. Iran. Chem.
Soc. 2015, 12, 1501–1508. DOI: 10.1007/s13738-015-0620-1.
33. Das, B.; Reddy, C. R.; Kumar, D. N.; Krishnaiah, M.; Narender,
R.
A
Simple, Advantageous Synthesis of 5-Substituted 1H- 47. Karimian, A.; Eshghi, H.; Bakavoli, M.; Shiri, A. Synthesis of
Tetrazoles. Synlett 2010, 2010, 391–394. DOI: 10.1055/s-0029-
1219150.
34. Lang, L.; Li, B.; Liu, W.; Li, J.; Xu, Z.; Yin, G. Mesoporous ZnS
New Derivatives of 4-(4,7,7-Trimethyl-7,8-Dihydro-6H-Benzo
[b]Pyrimido[5,4-e][1,4]Thiazin-2-yl)Morpholine. J. Heterocycl
Chem. 2015, 85, 275–279. DOI: 10.1002/jhet.2556.
Nanospheres:
A High Activity Heterogeneous Catalyst for 48. Afsharnia, M.; Shams, Sh.; Ghasemi, M.; Biglar, H.; Salari, S.;
Synthesis of 5-Substituted 1H-Tetrazoles from Nitriles and
Sodium Azide. Chem. Commun. 2010, 46, 448–450. DOI: 10.
1039/B912284B.
Moteallemi, A. Modeling and Optimization of Fluoride
Adsorption from Aqueous Samples by Ammonium Aluminium
Sulfate Using Response Surface Methodology (RSM). Fluoride
2019, 52, 77–98.
35. Rama, V.; Kanagaraj, K.; Pitchumani, K. Syntheses of 5-
Substituted 1 H -Tetrazoles Catalyzed by Reusable CoY Zeolite. J. 49. Iaiche, S.; Djelloul, A. ZnO/ZnAl2O4 Nanocomposite Films
Org. Chem. 2011, 76, 9090–9095. DOI: 10.1021/jo201261w.
36. Ghodsinia, S. S. E.; Akhlaghinia, B. Rapid Metal Free
Synthesis of 5-Substituted-1H-Tetrazoles Using Cuttlebone as a
Studied by X-Ray Diffraction, FTIR, and XRay Photoelectron
Spectroscopy. J. Spectrosc. 2015, 2015, 1–9. DOI: 10.1155/2015/
836859.
A
Natural High Effective and Low Cost Heterogeneous Catalyst. 50. Chang, S.-S.; Clair, B.; Ruelle, J.; Beauchene, J.; Di Renzo, F.;
RSC Adv. 2015, 5, 49849–49860. DOI: 10.1039/C5RA08147E.
37. Khan, K. M.; Fatima, I.; Saad, S. M.; Taha, M.; Voelter, W. An
Efficient One-Pot Protocol for the Conversion of Benzaldehydes
into Tetrazole Analogs. Tetrahedron Lett. 2016, 57, 523–525.
DOI: 10.1016/j.tetlet.2015.12.067.
38. Bosch, L.; Vilarrasa, J. Cu2(OTf)2-Catalyzed and Microwave-
Controlled Preparation of Tetrazoles from Nitriles and Organic
Azides under Mild, Safe Conditions. Angew. Chem. Int. Ed.
2007, 46, 3926–3930. DOI: 10.1002/anie.200605095.
39. Patil, V. S.; Nandre, K. P.; Borse, A. U.; Bhosale, S. V. InCl3-
Catalysed [2 þ 3] Cycloaddition Reaction: A Rapid Synthesis of
5substituted 1H-Tetrazoles under Microwave Irradiation. J.
Chem. 2012, 9, 1145–1152. DOI: 10.5402/2012/415645.
40. Marvi, Omid; Alizadeh, Abdolhamid; Zarrabi, Saeid.
Montmorillonite K-10 Clay as an Efficient Reusable
Heterogeneous Catalyst for the Solvent-Free Microwave
Quignard, F.; Zhao, G.-J.; Yamamoto, H.; Gril, J. J. Mesoporosity
as New Parameter for Understanding Tension Stress
Generation in Trees. J. Exp. Bot. 2009, 60, 3023–3030. DOI: 10.
1093/jxb/erp133.
a
51. Frost, R. L.; Wain Daria, L.; Wills, R. A.; Musemeci, A.; Martens,
W. A Thermogravimetric Study of the Alunites of Sodium,
Potassium and Ammonium. Thermochim. Acta 2006, 443, 56–61.
DOI: 10.1016/j.tca.2005.12.019.
52. Du, Z.; Si, C.; Li, Y.; Wang, Y.; Lu, J. Improved Synthesis of 5-
Substituted 1H-Tetrazoles via the [3 þ 2] Cycloaddition of
Nitriles and Sodium Azide Catalyzed by Silica Sulfuric Acid. Int.
J. Mol. Sci. 2012, 13, 4696–4703. DOI: 10.3390/ijms13044696.
53. Rostamizadeh, S.; Ghaieni, H.; Aryan, R.; Amani, A. Zinc
Chloride Catalyzed Synthesis of 5-Substituted 1H-Tetrazoles
under Solvent Free Condition. Chin. Chem. Lett. 2009, 20,
1311–1314. DOI: 10.1016/j.cclet.2009.06.020.
Mediated Synthesis of 5-Substituted 1H-Tetrazoles. Bull. Korean 54. Paudel, S.; Min, X.; Achary, S.; Khadka, D. B.; Yoon, G.; Kim,
Chem. Soc. 2011, 32, 4001–4004. DOI: 10.5012/bkcs.2011.32.11.
4001.
K. M.; Cheon, S. H. Triple Reuptake Inhibitors: Design,
Synthesis and Structure–Activity Relationship of
41. Cantillo, D.; Gutmann, B.; Kappe, C. O. Mechanistic Insights on
Azide-Nitrile Cycloadditions: On the Dialkyltin Oxide-
Benzylpiperidine–Tetrazoles. Bioorg. Med. Chem. Lett. 2017, 25,
5278–5289. DOI: 10.1016/j.bmc.2017.07.046.
Trimethylsilyl Azide Route and a New Vilsmeier-Haack-Type 55. Padvi, Swapnil A.; Dalal, Dipak S. Choline Chloride–ZnCl2:
Organocatalyst. J. Am. Chem. Soc. 2011, 133, 4465–4475. DOI:
10.1021/ja109700b.
42. Myznikov, L. V.; Efimova, Y. A.; Artamonova, T. V.; Koldobskii,
G. I. Synthesis of 5-Substituted Tetrazoles under Microwave
Recyclable and Efficient Deep Eutectic Solvent for the [2 þ 3]
Cycloaddition Reaction of Organic Nitriles with Sodium Azide.
Synth. Commun. 2017, 47, 779–787. DOI: 10.1080/00397911.
2017.1285033.
Activation in the Presence of Heterogeneous Catalyst (Zinc 56. Razavi, N.; Akhlaghinia, B. Cu (II) Immobilized on Aminated
Oxide). Russ. J. Org. Chem. 2011, 47, 728–730. DOI: 10.1134/
S1070428011050125.
43. Karimian, A.; Mohammadzadeh Kakhki, R.; Kargar Beidokhti, H.
Epichlorohydrin Activated Silica (CAES): As a New, Green and
Efficient Nanocatalyst for Preparation of 5-Substituted-1H-
Tetrazoles. RSC Adv. 2015, 5, 12372–12381.
Magnetic Co-Doped NiFe2O4 Nanocomposite: A Heterogeneous 57. Kantam, M. L.; Shiva Kumar, K. B.; Phani Raja, K. J. An
and Recyclable Catalyst for the One-Pot Synthesis of
Benzimidazoles, Benzoxazoles and Benzothiazoles under Solvent-
Free Conditions. J. Chin. Chem. Soc. 2017, 64, 1316–1325. DOI:
10.1002/jccs.201700060.
Efficient Synthesis of 5-Substituted 1H-Tetrazoles Using Zn/Al
Hydrotalcite Catalyst. J. Mol. Catal. A: Chem. 2006, 247,
186–188. DOI: 10.1016/j.molcata.2005.11.046.
58. Taghavi, F.; Gholizadeh, M.; Saljooghi, A. Sh.; Ramezani, M.
Cu(II) Immobilized on Fe3O4@APTMS-DFX Nanoparticles: An
Efficient Catalyst for the Synthesis of 5-Substituted 1H-
Tetrazoles with Cytotoxic Activity. Med. Chem. Commun. 2017,
8, 1953–1964. DOI: 10.1039/C7MD00302A.
44. Karimian,
A.
Synthesis
of
New
Pyrimido[50,40:5,6][1,4]Thiazino[2,3-b]Quinoxaline Derivatives
in One Step. J. Heterocyclic Chem. 2018, 55, 645–649. DOI: 10.
1002/jhet.3082.
45. Karimian, A.; Karimian, H. Synthesis of New Derivatives of 4- 59. Wang, H.; Zhao, W.; Du, J.; Wei, F.; Chen, Q.; Wang, X.
(4-Methyl-5H-Pyrimido[4,5-b][1,4]Thiazin-2-yl)Morpholine and
4-Methyl-2–(Piperidin-1-yl)-5H-Pyrimido[4,5-b][1,4]Thiazine. J.
Cationic Organotin Cluster [t-Bu2Sn(OH)(H2O)]22þ2OTfꢃ
Catalyzed One-Pot Three-Component Syntheses of 5-Substituted
1H-Tetrazoles and 2,4,6-Triarylpyridines in Water. Appl.
Organom. Chem. 2019, 33, 5132–5139. DOI: 10.1002/aoc.5132.
Chem.
Res.
2017,
41,
406–407.
DOI:
10.3184/
174751917X14967701767049.