Imidazolium-Based Ionic Network as a Robust Heterogeneous Catalyst in Synthesis of Phenacyl Derivatives

Article abstract of DOI:10.1134/S1070363219060185

A new imidazolium-based poly(ionic liquid) has been synthesized and used as a robust heterogeneous catalyst for the preparation of phenacyl derivatives by an S_N2 reaction of different phenacyl bromides with a broad range of nucleophiles. The products are obtained in high yields under mild conditions. The catalyst can be recycled efficiently.

Full text of DOI:10.1134/S1070363219060185

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ISSN 1070-3632, Russian Journal of General Chemistry, 2019, Vol. 89, No. 6, pp. 1218–1220. © Pleiades Publishing, Ltd., 2019.
Imidazolium-Based Ionic Network as a Robust Heterogeneous
Catalyst in Synthesis of Phenacyl Derivatives
N. Kakesha,b, S. Sayyahic*, R. Badria, and E. Tahanpesara
a Department of Chemistry, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
b Department of Chemistry, Khuzestan Science and Research Branch, Islamic Azad University, Ahvaz, Iran
c Department of Chemistry, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran
*e-mail: sayyahi.soheil@gmail.com
Received March 23, 2019; revised June 11, 2019; accepted June 13, 2019
Abstract—A new imidazolium-based poly(ionic liquid) has been synthesized and used as a robust
heterogeneous catalyst for the preparation of phenacyl derivatives by an SN2 reaction of different phenacyl
bromides with a broad range of nucleophiles. The products are obtained in high yields under mild conditions.
The catalyst can be recycled efficiently.
Keywords: poly(ionic liquid), phenacyl derivatives, green synthesis, nucleophilic substitution
DOI: 10.1134/S1070363219060185
INTRODUCTION
organic network (3) was prepared by condensation-
polymerization of 1,4-bis(imidazol-1-yl)-butane (1)
with commercially available 1,3,5-tris(bromomethyl)
benzene (2) via the SN2 nucleophilic substitution
reaction under conditions similar to those that had been
used earlier by Dai and co-workers [12] and our group
[13] (Scheme 1).
Polymeric ionic liquids or poly(ionic liquid)s
(PILs) refer to a subclass of polyelectrolytes efficiently
used in hydrogen energetics, catalysis, electro-
chemistry, gas separation, sorption, materials science,
bio- and membrane technology. The major advantages
of using PIL over ionic liquids (IL) are their enhanced
mechanical stability, durability, improved processing,
and spatial controllability [1–5].
Catalytic activity of the PIL was studied in the
synthesis of phenacyl derivatives in aqueous media.
Various substituted phenacyl bromides (4-Br, 4-NO2,
4-MeO, 4-H) were treated with anions N3–, SCN–,
CN–, NO2–, OAc–, and I– as nucleophiles under the
optimized conditions (see the table). The reaction
proceeded smoothly giving excellent yields of the
corresponding products.
Phenacyl derivatives constitute an important
platform for the synthesis of heterocyclic scaffolds,
that have been widely used in development of various
bio-active natural products, and pharmaceutical agents
[6]. For example, phenacyl bromides are used as
building blocks in synthesis of a wide range of five
and six membered rings such as imidazoles, selena-
zoles, and oxazoles as well as fused heterocyclic
compounds [7]. Azide and thiocyanate derivatives of
α-keto compounds are useful intermediates in the
synthesis of heterocyclic compounds including oxazoles,
pyrroles, pyrrolidines, imidazoles, and thiazoles [8].
The water insoluble catalyst 3 was also tested for
reusability in the synthesis of 5a. After the first cycle,
the PIL catalyst was separated by decanting, washed
by cold ether, and applied repeatedly five times using
the same method of its separation after each cycle. In
all cases yield of the process was higher than 90%.
In continuation of our recent studies of sustainable
catalytic reactions [9–11], we are presenting herein the
new PIL as a heterogeneous network catalyst for the
synthesis of different phenacyl derivatives.
EXPERIMENTAL
Synthesis of PIL 3. In a round-bottomed flask, a
magnetically stirred mixture of 1,4-bis(imidazol-1-yl)-
butane (1, 3 mmol, 0.285 g) with 1,3,5-tris-
(bromomethyl) benzene (2, 2 mmol, 0.357 g) in
acetonitrile (10 mL) was refluxed under the
RESULTS AND DISCUSSION
Generally, there are three common methods of
synthesis of PILs [2]. In the current study, the ionic
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IMIDAZOLIUM-BASED IONIC NETWORK AS A ROBUST HETEROGENEOUS CATALYST
Scheme 1. Synthesis of the ionic organic network catalyst and its SEM images.
1219
Br−
N+
N
N
Br−
Br
N
(
)
N+
4
C
Br−
N+
H2
N
Br−
N+
(
DMSO, N2
80oC, 72 h
Br-
+
H2C
Br−
N+
)
N
N
Br
N
Br
(
)
N
N
C
4
(
)
N+
C
4
H2
H2
N
1
2
3
20 μm
20 μm
Synthesis of phenacyl derivatives catalyzed by 3 in water
O
O
Br
Y
3 (0.01 g), NaY
X
X
H2O, reflux
4
5
X = H, NO2, MeO, Br.
Comp.
Comp.
no.
X
Nucleophile Y Time, min Yield, %a,b
X
Nucleophile Y Time, min Yield, %a,b
no.
5m
5n
5o
5p
5q
5r
5a
5b
5c
5d
5e
5f
NO2
NO2
NO2
NO2
NO2
NO2
Br
N3
10
10
15
15
15
10
10
10
15
20
15
10
94, 15c, 10d
MeO
MeO
MeO
MeO
MeO
MeO
H
N3
10
10
20
20
25
15
10
10
15
20
15
10
90
87
78
63
67
90
92
88
80
70
72
87
SCN
CN
NO2
OAc
I
92
83
72
77
91
94
91
80
70
74
90
SCN
CN
NO2
OAc
I
5g
5h
5i
N3
5s
N3
Br
SCN
CN
NO2
OAc
I
5t
H
SCN
CN
NO2
OAc
I
Br
5u
5v
5w
5x
H
5j
Br
H
5k
5l
Br
H
Br
H
a
The nature of all products was confirmed by comparing their physical and spectral data with the authentic samples [6, 14–17]. b Isolated
yields. c CH2Cl2. d n-Hexane.
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KAKESH et al.
atmosphere of nitrogen for 72 h. The cooled down
reaction mixture was filtered through filter paper, and
the solid thus retained was washed with cold ethanol
(10 mL).
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CONCLUSIONS
An efficient and environmentally benign protocol
for the synthesis of phenacyl derivatives catalyzed by
new ionic network in aqueous media is developed. The
catalyst is characterized by high performance in the
nucleophile substitution process and can be used
repeatedly without significant loss in catalytic activity.
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CONFLICT OF INTEREST
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Org. Chem. Res., 2017, vol. 3, p. 25. doi 10.22036/
org.chem.2017.41101
No conflict of interest was declared by the authors.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 89 No. 6 2019