4
S. Rezayati et al. / C. R. Chimie xxx (2016) 1e5
Table 5
filtration, and the product was extracted with ethyl acetate
(3 ꢁ 5 mL). The extract was dried over anhydrous Na2SO4
The reusability of [Cmmim]Br and [Cmmim]BF4 for the preparation of 1-
azido-3-phenoxy-2-propanol.
and concentrated under vacuum to obtain b-hydroxyazide
Product
Total reusability [Cmmim]Br [Cmmim]BF4
in 85e95% and 86e96% isolated yields. For styrene oxide,
further purification was achieved by preparative TLC or by
silica gel column chromatography. The spectral data of all
the products were identical to those of the authentic
samples.
Yield (%)
Yield (%)
1
2
3
4
5
96
95
95
93
91
95
95
93
92
90
OH
O
N3
Ph
2.3.1. 1-Azido-3-phenoxy-2-propanol [37]
IR nmax/cmꢂ1: 2103 (N3); 1H NMR (CDCl3, 400 MHz):
when the reaction was performed at 60 ꢀC (Table 2, entry
1). Increasing the reaction temperature did not improve the
results and neither increased the yield nor lowered the
conversion time (Table 2, entries 4e5).
d
¼ 3.45e3.54 (2H, m), 3.89 (1H, m), 3.97e4.03 (2H, m), 4.18
(1H, s), 6.95e7.00 (m, 2H), 7.02e7.06 (m, 1H), 7.27e7.36 (m,
2H); 13C NMR (CDCl3, 100 MHz):
121.1, 129.4, 158.3.
d
¼ 53.5, 69.2, 69.3, 114.3,
After optimization of reaction conditions, the reaction
was examined in the presence of various catalysts including
citric acid, cyanuric chloride, acetic acid, oxalic acid, and
silica gel under solvent-free conditions at 60 ꢀC, and the
results are summarized in Table 3. Higher yield and short
reaction time of product were obtained when an acetic acid
functionalized imidazolium salt [Cmmim]BF4 or [Cmmim]
Br was utilized as the catalyst (Table 3, entry 6). Therefore,
this reaction was developed with various aromatic and
aliphatic epoxides with sodium azide in the presence of
Brønsted acidic ionic liquids 1a and 1b under solvent-free
conditions at 60 ꢀC, and the results are summarized in
Table 4.
2.3.2. 2-Azido-2-phenyl-1-ethanol [37]
IR nmax/cmꢂ1: 2102 (N3); 1H NMR (CDCl3, 400 MHz):
d
¼ 3.37 (1H, s), 3.74 (2H, m), 4.65e4.69 (1H, m), 7.34e7.44
(5H, m); 13C NMR (CDCl3, 100 MHz):
128.4, 128.6, 136.4.
d
¼ 66.3, 68.0, 127.4,
2.3.3. 1-Azido-3-butoxy-2-propanol [37]
IR nmax/cmꢂ1: 2102 (N3); 1H NMR (CDCl3, 400 MHz):
¼ 0.87 (3H, t), 1.31e1.35 (2H, m), 1.50e1.53 (2H, m), 3.14
d
(1H, s), 3.30e3.32 (2H, m), 3.39e3.44 (4H, m), 3.87 (1H, m);
13C NMR (CDCl3, 100 MHz):
69.74, 70.59, 70.71.
d
¼ 13.78, 19.16, 30.74, 53.52,
As can be seen in Table 4, to ascertain the scope and
limitation of the present reaction, various aliphatic epox-
ides reacted with sodium azide using BAIL 1a and BAIL 1b
under solvent-free conditions at 60 ꢀC to produce the cor-
responding 2-azidoalcohols in excellent yields and a short
reaction time. Reaction with bicyclic epoxides such as
cyclohexene epoxide, cyclopentene epoxide, and cyclo-
octene epoxide afforded 2-azidoalcohols in an excellent
and short reaction time. The structures of 1,2-azidoalcohol
products were characterized by IR, 1H NMR and 13C NMR
spectral data, and physical properties were compared with
the literature values of known compounds.
One of the characteristics of ionic liquids is recovery and
reusability. Thus, the recovery and reusability of BAILs 1a
and 1b for the condensation of phenyl glycidyl ether
(1 mmol) with sodium azide (1.1 mmol) under solvent-free
conditions at 60 ꢀC as a model reaction was investigated;
the results are shown in Table 5. As can be seen in Table 5,
the recovery and reusability for two ionic liquid was tested,
after completion of the reaction; the catalyst was recovered
by filtration and reused yields remained unchanged.
In another study, to show the merit of the our work for
the synthesis of 1,2-azidoalcohols of phenyl glycidyl ether
(1 mmol) with NaN3 (1.1 mmol) under solvent-free condi-
tions at 60 ꢀC in the presence of BAILs 1a and 1b was
selected as a model reaction, and were compared with
other catalysts such LiBF4, (TBA)4PFeW11O39$3H2O, NaN3/
NH4Cl, NaN3/Mg(ClO4)2, NaN3/LiClO4, 3D-network poly-
mer, PTC, SiO2-PEG-ImBr, sulfuric acid, and MPTC. The re-
sults are summarized in Table 6. Each of these methods
often suffer from some troubles such as long reaction times
and tediousness for the completion of the reaction (Table 6,
entries 2e7), use of organic solvents under reflux
3. Results and discussion
BAILs 1a and 1b were prepared according to the litera-
ture procedure [47e49]. BAILs 1a and 1b were also char-
acterized by thermal gravimetric analysis (TGA), X-ray
diffraction analysis (XRD), differential thermal gravimetry
(DTG), and Fourier transform infrared spectroscopy (FT-IR)
analysis [47e49]. We, herein, report the use of an acetic
acid functionalized imidazolium salt [Cmmim]BF4 or
[Cmmim]Br as an ecofriendly, inexpensive, and recyclable
catalyst for the synthesis of 1,2-azidoalcohols by regiose-
lective ring opening of some epoxides with sodium azide
under mild and neutral reaction conditions at 60 ꢀC
(Scheme 1).
In the first step, in order to optimize the catalyst for the
preparation of 2-zzido-2-phenyl-1-ethanol, the reaction of
phenyl glycidyl ether (1 mmol) with NaN3 (1.1 mmol) under
solvent-free conditions using different amounts of BAIL 1a
was chosen as a model reaction in promoting the 1,2-
azidoalcohols. The results are presented in Table 1. First,
the reaction was performed in the absence of a catalyst, and
after 24 h, no product was obtained (Table 1, entry 1). It was
found that 10 mol % of the BAIL 1a under solvent-free
conditions at room temperature gave 2-azido-2-phenyl-1-
ethanol in 91% yield and 25 min (Table 1, entry 5). More-
over, the lower yield of 2-azido-2-phenyl-1-ethanol can be
reached by increasing the amount of the catalyst (Table 1,
entry 7).
In the second step, the model reaction was tested using
different temperatures and was obtained in good to
excellent yields under solvent-free conditions (Table 2). As
it can be seen in Table 2, the best results were obtained
Please cite this article in press as: S. Rezayati, et al., Acetic acid functionalized ionic liquid systems: An efficient and recyclable
catalyst for the regioselective ring opening of epoxides with NaN3, Comptes Rendus Chimie (2016), http://dx.doi.org/10.1016/
j.crci.2016.07.004