Synthesis of 1,2-azidoalcohols from epoxides using a task-specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide

Article abstract of DOI:10.1016/j.crci.2013.08.008

A task-specific ionic liquid as an environmentally eco-friendly green catalyst has been synthesized and used in the ring opening of epoxides under green conditions. In order to use protic ionic liquids (PIL), we decided to synthesize 1,2-azidoalcohols via

Full text of DOI:10.1016/j.crci.2013.08.008

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Full paper/Memoire
Synthesis of 1,2-azidoalcohols from epoxides using a
task-specific protic ionic liquid: 1-hydrogen-3-
methylimidazolium azide
*
Fariba Heidarizadeh , Ali BeitSaeed, Eshagh Rezaee-Nezhad
Department of Chemistry, Faculty of Sciences, Shahid Chamran University, Ahvaz 6135743169, Iran
A R T I C L E I N F O
A B S T R A C T
Article history:
A task-specific ionic liquid as an environmentally eco-friendly green catalyst has been
synthesized and used in the ring opening of epoxides under green conditions. In order to
use protic ionic liquids (PIL), we decided to synthesize 1,2-azidoalcohols via a ring opening
reaction of epoxides with 1-hydrogen-3-methylimidazolium azide ([Hmim]N3), which
actually acts as a solvent, a reagent and an activator of the epoxide ring. The reaction was
carried out in short times (50–70 min) at 70 8C to give 1,2-azidoalcohol in 80–94% isolated
yields.
Received 21 June 2013
Accepted after revision 12 August 2013
Available online xxx
Keywords:
Protic ionic liquid
Ionic liquid
´
ß 2013 Published by Elsevier Masson SAS on behalf of Academie des sciences.
[Hmim]N3: 1,2-azidoalcohol
Epoxide
Ring opening
1. Introduction
few years using a variety of catalysts [6]. But development
of a new and efficient protocol for this transformation
1,2-azidoalcohol has been considered increasingly, since
this compound is very important in both organic chemistry
– for the synthesis of amino sugars, carboxylic nucleosides,
lactames, and oxazolines [1]– and inmedicalchemistry– for
under mild and more convenient conditions is still needed.
Herein we report an efficient method for the conversion
of epoxides to 1,2-azidoalcohols. In this method we used a
triple-function protic ionic liquid that contains an azide
nucleophile for ring opening of epoxides. Various aliphatic
and aromatic epoxides were converted into their azidoal-
cohols derivatives in excellent yields and in short time
(Scheme 1).
PILs are a class of ionic liquids which are formed by
mixing equimolar amounts of Brønsted acids and bases
[16,6]. The strength of the acid/base combination deter-
mines the degree of the proton activity.
Recently, Welton et al. described the conversion of
biomass to fuels and chemical products by ionic liquids
[17]. On the other hand, Wasserscheid et al. studied the
surface and the near-surface region of ionic liquid systems
with a clear focus on reactions [18]. Finally, Davis Jr. et al.
reported, for the first time, task-specific ionic liquids [19],
non-toxic ions in the formulation of ionic liquids [20], and
‘‘boronium-ion’’-based ionic liquids [21].
the synthesis of
b-blockers and its presence in various
natural products and different bioactive compounds [2–4].
The ring opening of epoxides, which have been innovative
ways to obtain direct azidolysis of epoxides in the presence
of sodium azide, are frequently performed under several
different conditions [5–9].
The ring cleavage of epoxides with azide [10–14]
generally requires a long reaction time (12–48 h) and is
often accompanied by isomerization, epimerization, rear-
rangement of the products [15], and tedious work-up. In
order to overcome some of these limitations, a number of
alternative procedures have been reported over the past
*
Corresponding author.
E-mail address: heidarizadeh@scu.ac.ir (F. Heidarizadeh).
1631-0748/$ – see front matter ß 2013 Published by Elsevier Masson SAS on behalf of Acade´mie des sciences.
http://dx.doi.org/10.1016/j.crci.2013.08.008
Please cite this article in press as: Heidarizadeh F, et al. Synthesis of 1,2-azidoalcohols from epoxides using a task-
specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.08.008

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N3
OH
O
70 °C
[Hmim]N3
OH
N3
R
R
R
Scheme 1. Preparation of azidohydrines in the presence of TSIL.
2. Results and discussion
Considering the emerging importance of [Hmim]N3
as novel reactions media, we wish to report the use of
task-specific ionic liquids as efficient promoters for the
ring opening of various epoxides. The procedure gives
products in good yields and short reaction times and
avoids using organic solvents (handling, cost, safety,
pollution). Environmental-friendly ionic liquid afforded
a valuable alternative to promote numerous efficient
catalytic systems that have already been proposed for
the ring opening of epoxides. As it can be seen in Table 3,
Task-specific protic ionic liquids combine the advan-
tageous characteristics of solid acids and mineral acids,
and can be good candidates for traditional mineral liquid
acids, such as sulfuric acid and hydrochloric acid, in
chemical processes [22,23]. Thus, as
a part of our
continuing interest in the development of clean chemical
processes, we synthesized a task-specific protic ionic
liquid, [Hmim]N3. This ionic liquid has an acidic hydrogen
that catalyzes the reaction and has an azide anion that
takes part in the reaction. In this process, the remaining
part of [Hmim]N3 is methylimidazole, which can be used
in the preparation of any other ionic liquids without any
more purification, and this is in agreement with the
atomic economy of green chemistry principles. We
believe that this paper is the first report of this kind of
task-specific protic ionic liquid.
In a typical experiment, phenyl glycidyl ether and
[Hmim]N3 was selected. The effect of the amount of ionic
liquid on the reaction time was studied by varying the
quantity of ionic liquid (1, 1.2, 1.5, 2, and 3 mmol/
1 mmol phenyl glycidyl ether). The reactions were
carried out under similar reaction conditions. It was
observed that, with an increase in the proportion of ionic
liquid, the azidolysis of phenyl glycidyl ether increases.
The highest conversion of epoxide was obtained when
the amount of ionic liquid used was 3 mmol/1 mmol
epoxide (Table 1).
[Hmim]N3 as
a catalyst afforded good results in
comparison to the other catalysts. In order to evaluate
the efficiency of the method we introduce, more recently
developed methods were compared with our present
one on the basis of the yields and reaction times
parameters; the results are given in Table 4.
Scheme 2 shows a plausible mechanism for the ring
opening of epoxides in the [Hmim]N3 as reagent, catalyst,
and solvent.
3. Experimental
Products were characterized by comparison of their
spectroscopic data (1H NMR, 13C NMR, and IR) and
physical properties with those reported in the literature.
NMR spectra were recorded in CDCl3 on Bruker Avance
DPX 500 and 400 MHz spectrometers using TMS as
an internal standard. FTIR spectra of KBr powder-
pressed pellets were recorded on a BOMEM MB-Series
1998 FT–IR spectrometer. All yields refer to isolated
products.
The effect of the reaction temperature on the reaction
time of phenyl glycidyl ether azidolysis was investigated
at reaction temperatures ranging from 25 to 70 8C. The
results show that the suitable reaction temperature is
70 8C (Table 2).
3.1. Procedure for the preparation of task-specific ionic
liquids [Hmim]N3 from [Hmim]Cl
After optimizing the conditions, we examined the
generalization of these conditions to other substrates
using several epoxides. Table 3 shows the results that
clarify the fact that the reaction proceeds very efficiently
in all cases. Different epoxides underwent ring opening
easily in the presence of [Hmim]N3 at 70 8C. The products
were formed in excellent yields. The conversion was
complete in 50–70 min.
1-hydrogen-3-methylimidazolium chloride was pre-
pared according to [24]. [Hmim]Cl (11.80 g, 0.1 mol) was
dissolved in dry acetonitrile (25 mL) and stirred at room
temperature for 25 min; NaN3 (0.1 mol) dissolved in dry
acetonitrile (40 mL) was added dropwise to [Hmim]Cl
Table 1
Table 2
Optimization study of azidolysis reaction of phenyl glycidyl ether with
Optimization study of azidolysis reaction of phenyl glycidyl ether (mmol)
with [Hmim]N3 (3 mmol) at different temperatures.
different amounts of [Hmim]N3 at 70 8C.
Entry
[Hmim]N3 (mmol)
Reaction progress
Time (min)
Entry
Temperature (8C)
Reaction progress
Time (min)
1
2
3
4
5
1
–
–
1
2
3
4
5
25
40
50
60
70
–
–
1.2
1.5
2
–
–
–
–
Complete
Complete
Complete
100
85
55
completed
completed
completed
85
60
55
3
Please cite this article in press as: Heidarizadeh F, et al. Synthesis of 1,2-azidoalcohols from epoxides using a task-
specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.08.008

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3
Table 3
Preparation of 1,2-azidoalcohols using [MIM]N3.
Entry
1
Epoxide
Product
Time (min)
55
Yield (%)
94
O
OH
O
O
Ph
Ph
N3
2
3
70
50
89
88
OH
O
O
O
N3
N3
O
Ph
Ph
OH
4
5
60
60
80
87
OH
O
O
O
O
N3
OH
O
O
O
O
O
N3
6
7
65
70
83
82
N3
OH
N3
OH
O
NaN3
H3C
N
H3C
H3C
60 min, r.t.
N
r.t., 30min
N
N
H
N
H
+
HCl
N
-
Acetonitrile
Cl
N3
Hmim N3
Hmim Cl
Scheme 2. Mechanism of the epoxide ring opening reaction by a task-specific ionic liquid.
over a period of 60 min at room temperature. The reaction
mixture was magnetically stirred for 24 h at room
temperature. The obtained white solid was washed with
acetonitrile and the ionic liquid present in the filtrate was
obtained by evaporation of the solvent under reduced
pressure (Scheme 1).
HO
R
N3
CH3
H3C
-
N3
H
N3
N
N
N
H
O
N
3.2. General procedure for the preparation of 2-azidoalcohols
H
R
A
mixture of epoxide (1 mmol) and [Hmim]N3
O
(3 mmol) was heated at 70 8C under stirring for the
time shown in Table 1 (Scheme 3). Progress of reaction
was monitored by TLC using ethyl acetate:n-hexane
(1:5). After reaction completion, the mixture was
extracted with ethyl ether (10 mL Â 3), washed with
brine, dried with CaCl2 and evaporated under reduced
pressure. The desired azidohydrines were obtained in
good to excellent isolated yields (80–94%).
R
CH3
H
N
O
-
N3
N
H
R
Scheme 3. Synthesis of a task-specific ionic liquid.
Please cite this article in press as: Heidarizadeh F, et al. Synthesis of 1,2-azidoalcohols from epoxides using a task-
specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.08.008

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Table 4
Comparison of efficiency of various catalysts in synthesis of 1,2-azidoalcohol.
Entry
Catalyst/reagent/solvent
Temperature
Time (min)
Yield (%)
References
1
2
5
2
3
4
6
7
8
[Hmim]N3
70 8C
80 8C
Reflux
r.t
55
90
94
89
95
45
99
95
90
85
86
This work
[5]
Network Polymer/NaN3/water
SiO2–PEG/NaN3/H2O
120
300
180
180
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b-cyclodextrine/TMSN3/H2O
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MPTC/NaN3/H2O
30
Er(OTf) 3/TMSN3/Solvent free
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support of this work by Shahid Chamran (Ahvaz)
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Please cite this article in press as: Heidarizadeh F, et al. Synthesis of 1,2-azidoalcohols from epoxides using a task-
specific protic ionic liquid: 1-hydrogen-3-methylimidazolium azide. C. R. Chimie (2013), http://dx.doi.org/10.1016/
j.crci.2013.08.008