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Journal of the Iranian Chemical Society
ORIGINAL PAPER
KIT‑6‑anchored sulfonic acid groups as a heterogeneous solid acid
catalyst for the synthesis of aryl tetrazoles
Alireza Najaf Chermahini1 · Nikzad Andisheh1 · Abbas Teimouri2
Received: 21 May 2017 / Accepted: 23 December 2017
© Iranian Chemical Society 2018
Abstract
In the current study, a simple, environmentally benign and cost-efective method is presented for the preparation of 5-sub-
stituted-1H-aryltetrazoles. To this goal, mesoporous KIT-6 silica anchored with sulfonic acid (–SO3H) groups via post-
grafting modifcation was synthesized using the sol–gel method and characterized by XRD, TGA, FTIR, BET, TEM and
SEM techniques. For the preparation of tetrazole derivatives, the efect of various parameters such as catalyst amount, aryl
nitrile:azide ratio, temperature and reaction time was tested. The hybrid organic/inorganic catalyst could be recovered easily
through a simple fltration and reused multiple times without signifcant loss in activity.
Keywords Post-grafting modifcation · Sol–gel method · Sulfonated KIT-6 · 5-Substituted-1H-tetrazoles
Introduction
products from the catalyst is a major problem, the heteroge-
neous alternatives have been received considerable attention.
So far, various heterogeneous catalysts have been reported
by research groups such as nanocrystalline ZnO [21], Cu2O
[22], Zn/Al hydrotalcite [23], COY zeolite [24], modifed
MCM-41 [25], mesoporous ZnS nanospheres [26], mont-
morillonite [27], modifed montmorillonite clays [28] and
sulfated zirconia [29].
Tetrazoles are known as a family of synthetic organic het-
erocycles, which have been of much attention due to their
numerous applications [1]. A series of tetrazole compounds
sives with high-performance ability as replace for TNT and
formulation of solid rocket propellants [2, 3]. In addition,
they are bioisosteres of the carboxylic acid group in drug
design [4] and play important roles in coordination chem-
istry as dentate aromatic N-donor ligands [5]. Also, they
have been utilized in photography [6], synthons [7], various
biological activities [8], dye-sensitized solar cells [9–11] and
information recording systems [12]. Generally, preparation
of these heterocycles is the cycloaddition reaction of azide
salts and aryl or alkyl nitriles [13]. The choice of a proper
catalyst is critical in achieving good results. In the earlier
synthetic methods, homogeneous catalysts such as BF3-OEt2
[14], AlCl3 [15], AgNO3 [16], Fe(OAc)2 [17], TBAF [18],
copper trifates [19] and zinc(II) salts [20] were used. Since
for homogeneous catalysts, the difculty in separation of the
Mesoporous KIT-6 [30] material with high thermal sta-
bility and surface area, large and tunable pore diameter
and narrow particle size distributions has been interested
for numerous applications such as sensors, drug delivery,
catalysis, adsorption, lithium-ion batteries and nanode-
vices [31–40]. This mesoporous material that is similar
to MCM-48 but benefts from much larger diameter [41]
shows a three-dimensional cubic Ia3d symmetry with the
interpenetrating bicontinuous network of chiral channels
[42]. These features let it to permit difusion of reactant to
its channels and active sites easier than other mesoporous
materials [43]. However, it should be noted that due to its
electronically neutral character, the pristine KIT-6 material
has a few weak Brönsted and Lewis acid sites. The acidity
character could be improved by incorporation of sulfonic
acid groups into the framework by employing post-grafting
methods (Scheme 1). Here we have introduced a catalytic
method for the synthesis of 5-substituted-1H-tetrazoles
using PrSO3H–KIT-6 material.
* Alireza Najaf Chermahini
1
Department of Chemistry, Isfahan University of Technology,
Isfahan 84156-83111, Iran
2
Chemistry Department, Payame Noor University,
Tehran 19395-3697, Iran
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