Synthesis and characterization of a novel paramagnetic functionalized ionic liquid as a highly efficient catalyst in one-pot synthesis of 1-amidoalkyl-2-naphtols

Article abstract of DOI:10.1016/j.molliq.2014.07.003

A novel paramagnetic ionic liquid, 3-(2-hydroxyethyl)-1-methyl imidazolium bromotrichloro ferrate (III), was synthesized and exhibited high catalytic performance in the synthesis of 1-amidoalkyl-2-naphthols via one-pot three-component condensation reactio

Full text of DOI:10.1016/j.molliq.2014.07.003

MOLLIQ-04338; No of Pages 7
Journal of Molecular Liquids xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
1
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Synthesis and characterization of a novel paramagnetic functionalized
ionic liquid as a highly efficient catalyst in one-pot synthesis
of 1-amidoalkyl-2-naphtols
Q24Q1 Soheil Sayyahi, Atena Azin, Seyyed Jafar Saghanezhad
5
Department of Chemistry, College of Chemical Engineering, Mahshahr Branch, Islamic Azad University, Mahshahr, Iran
OOF
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a r t i c l e i n f o
a b s t r a c t
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Article history:
A novel paramagnetic ionic liquid, 3-(2-hydroxyethyl)-1-methyl imidazolium bromotrichloro ferrate (III), was 16
synthesized and exhibited high catalytic performance in the synthesis of 1-amidoalkyl-2-naphthols via one- 17
pot three-component condensation reaction of aromatic aldehydes, 2-naphthol and acetamide at 85 °C under 18
solvent-free conditions. The catalyst showed response to an external magnet and was characterized by Fourier 19
transform infrared spectroscopy (FT-IR), UV–Visible spectroscopy, Thermal gravimetric analysis (TGA) and 20
Received 17 April 2014
Received in revised form 15 June 2014
Accepted 7 July 2014
Available online xxxx
Raman spectroscopy.
21
12
22
13
14
15
Keywords:
© 2014 Elsevier B.V. All rights reserved.
Magnetic ionic liquid
1-Amidoalkyl-2-naphthol
Multi-component reaction
26
34
25
27
1. Introduction
range of biological, medicinal, and pharmacological activities [19–21]. 53
Although many catalytic systems have been developed for the synthesis 54
of amidoalkyl naphthols, some of them suffer from drawbacks such as 55
prolonged reaction times, low yields, using carcinogenic solvents, toxic- 56
ity and reusability of highly acidic and expensive catalysts, higher reac- 57
tion temperature, harsh conditions, large waste production and 58
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50
51
52
Due to their unique properties (such as low vapor pressure, wide
liquid range, low flammability, high conductivity, excellent stability
and large electrochemical window), ionic liquids (ILs) have offered
great potential for developing clean catalytic technologies and have
been studied widely in catalytic reactions. ILs can be designed for
specific catalytic processes and using them usually presents the ad-
vantages of high catalytic activity and good selectivity [1,2].
Recently, the term “magnetic ionic liquid” (MIL) was proposed
by Hamaguchi and co-workers to introduce ILs with paramagnetic
like temperature dependence of susceptibility [3,4]. The MILs are
primarily based on high-spin d5 Fe (III) in the form of tetrachloro-
or tetrabromoferrate(III) with various counter cations. Owing to
the high single-ion magnetic moments, these MILs exhibited a
strong response to magnetic fields [5]. Since then, much attention
has been paid to the design and synthesis of this new class of ILs
[6–10]. Moreover, the catalytic activities of MILs have been studied
in Friedel Crafts acylation [11], aryl grignard cross coupling of alkyl
halides [12], preparation of 1,2-azidoalcohols [13], glycolysis of
undesirable byproducts [22–29].
59
In this paper, we report on the preparation of 3-(2-hydroxyethyl)-1- 60
methyl imidazolium bromotrichloro ferrate (III) ([C2OHmim]FeCl3Br−) 6Q13
as a novel paramagnetic ionic liquid. The catalytic activity of the MIL was 62
investigated for the one-pot synthesis of 1-amidoalkyl-2-naphtols.
63
2. Experimental
64
All compounds were purchased from Aldrich and Merck companies 65
and used as received without further purification. Progress of the reac- 66
tion was monitored by TLC on Merck DC-Alufolien plates pre-coated 67
with silica gel F254
.
68
2.1. Synthesis of MIL [C2OHmim]FeCl3Br−
69
UNCORRECTED PR
poly(ethylene terephthalate) [14], “liquid fixed-bed” catalysts in
flow application [15], oxidative desulfurization of fuels [16] and
multi-component synthesis of 1- and 5-substituted 1H-tetrazoles
[17] and quinazoline derivatives [18].
1-Amidoalkyl-2-naphthol derivatives containing 1,3-amino-
oxygenated functional groups are an important class of heterocyclic
compounds. This is mainly due to the fact that they possess a broad
3-(2-Hydroxyethyl)-1-methyl imidazolium bromide (2.0 g) [30] 70
and iron (III) chloride hexahydrate (2.7 g) were dissolved in dry 71
methanol (10 mL). The resulting mixture was stirred at room tem- 72
perature for 24 h. After the solution was filtered, methanol was re- 73
moved under vacuum. The obtained ionic liquid was redissolved in 74
ethyl acetate (10 mL) and the solution was centrifuged to separate 75
possible residue of the inorganic salts. Then, ethyl acetate was evap- 76
orated and the resulting dark brown liquid, 3-(2-hydroxyethyl)-1- 77
E-mail address: sayyahi.soheil@gmail.com (S. Sayyahi).
http://dx.doi.org/10.1016/j.molliq.2014.07.003
0167-7322/© 2014 Elsevier B.V. All rights reserved.
Please cite this article as: S. Sayyahi, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.07.003

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S. Sayyahi et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
Scheme 1. Synthesis of the magnetic ionic liquid.
Fig. 1. Image of the [C2OHmim]FeCl3Br− ionic liquid droplet attracted toward a NbFeB magnet.
in a glass test tube and heated at 85 °C in an oil bath for the time 84
shown in Table 2. After completion of the reaction as judged by TLC 85
(using n-hexane/ethylacetate (4:1) as eluent), the mixture was 86
allowed to cool to room temperature. Then, to separate the catalyst, 87
diethyl ether (2 × 5 mL) was added to the reaction mixture and 88
stirred for 5 min. The ethereal phase was decanted and evaporated 89
to get the ionic liquid. The solid residue from previous step was iso- 9Q04
lated and purified by recrystallization in hot ethanol. The desired 91
pure product was characterized by comparison of their physical 92
data with those of known 1-amidoalkyl-2-naphthol derivatives.
93
3. Results and discussions
94
3.1. Synthesis and characterization of the paramagnetic ionic liquid
[C2OHmim]FeCl3Br−
9Q55
Fig. 2. Visible absorption spectrum of [C2OHmim]FeCl3Br− at a concentration of 0.1 M in
acetonitrile.
96
The magnetic ionic liquid ([C2OHmim]FeCl3Br−) was prepared 97
following the straightforward synthesis procedure shown in Scheme 1. 98
A dark brown liquid was obtained by mixing equimolar amount of 99
100
[C2OHmim]FeCl3Br− exhibits paramagnetism response to an ex- 101
ternal neodymium iron boride (NeFeB) magnet. A droplet of the 102
78
79
methyl imidazolium bromotrichloro ferrate (III), was dried in a vac-
uum oven at 60 °C overnight.
[C2OHmim]Br− and FeCl3.6H2O in dry methanol for 24 h.
80
81
2.2. General procedure for the synthesis of 1-amidoalkyl-2-naphthols by
[C2OHmim]FeCl3Br−
ionic liquid is distorted, as the magnet is approached (Fig. 1).
103
82
83
A mixture of 2-naphthol (1 mmol), aryl aldehyde (1 mmol), acet-
amide (1 mmol) and [C2OHmim]FeCl3Br− (0.05 mmol) was placed
The visible absorption spectrum was recorded on a Jenway UV– 104
Visible spectrometer model Genova Plus in acetonitrile (0.1 M, 105
Fig. 3. FT-IR spectrum of [C2OHmim]FeCl3Br−
.
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S. Sayyahi et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
3
Fig. 4. Raman spectrum of [C2OHmim]FeCl3Br−
.
stretching vibration. The peaks at 3157 cm−1 and 2955 cm−1 are relat- 111
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ed to the stretching vibration of aromatic and aliphatic C\H bonds, re- 112
spectively. Also, a relatively strong peak at 1563 cm−1 is assigned to 113
C_N stretching vibration of imidazole ring (Fig. 3.).
114
Raman measurements were carried out on an Almega Thermo 115
Nicolet Dispersive Raman spectrometer at a wavelength of 532 nm 116
of a Nd:YLF laser. Vibrational Raman spectrum of the MIL shows a 117
peak at 307 cm1 and a shorter one at 166 cm−1, which is most likely 118
due to the formation of FeCl3Br− anion (Fig. 4.).
119
The thermal stability of the MIL was investigated by the thermal 120
gravimetric analysis (TGA) and carried out on a BÄHR-Thermoanalyse 121
GmbH instrument from room temperature to 600 °C under nitrogen at- 122
mosphere at a heating rate of 15 °C/min. According to the TGA curve, 123
the weight loss (b200 °C) is most probably due to the evaporation of 124
adsorbed water. Moreover, the weight loss observed between 300 °C 125
and 460 °C is attributed to the decomposition of the organic cation of 126
Fig. 5. TGA of [C2OHmim]FeCl3Br−
.
the MIL (Fig. 5.).
127
t1:1
t1:2
Table 1
Optimization of reaction condition.a
3.2. Application of [C2OHmim]FeCl3Br− for the synthesis of 1-aminoalkyl-2- 128
naphthols 129
t1:3
Entry
Catalyst (mmol)
Temperature (ºC)
Time (min)
Yieldb (%)
t1:4
t1:5
t1:6
t1:7
t1:8
t1:9
t1:10
1
2
3
4
5
6
7
0
1
1
0.5
0.2
0.05
0.05
85
r.t.
65
80
70
70
85
140
150
35
15
20
34
26
65
90
80
73
94
In view of ionic liquid catalysis, the combination of FeCl3Br− as a 130
magnetoactive metal complex anion [8] and alcohol-functionalized 131
imidazolium base as counter-cation [31], may have unique catalytic po- 132
30
15
tential applications.
133
Literature surveys indicate that, there is no report in MIL-catalyzed 134
synthesis of 1-aminoalkyl-2-naphthols. In this regard, the performance 135
of the MIL as catalyst was tested using condensation of benzaldehyde 136
(1.0 mmol), 2-naphthol (1.0 mmol) with acetamide (1.0 mmol) as 137
model substrates under solvent-free conditions. As seen from the data 138
shown in Table 1, using 5 mol% of [C2OHmim]FeCl3Br− was sufficient 139
to promote the multi-component reaction efficiently at 85 °C, to afford 140
the product in excellent yields and in appropriate reaction time 141
(Scheme 2), and also giving turn over number (TON) and turn over fre- 142
a
t1:11
t1:12
Solvent-free.
Isolated yield.
b
106 500–1000 nm). The MIL showed bands for the [FeCl3Br]− ion similar
107 to those for the [FeBr4]− ion (Fig. 2.) [10].
108
The FT-IR spectrum of [C2OHmim]FeCl3Br− in the range of 400–
UNCORRECTED PR
109 4000 cm−1 was obtained on a BOMEM MB-Series 1998 FT-IR spectrom-
110 eter. The broad peak at 3547 cm−1 is due to the hydroxyl group
quency (TOF) up to 18.8 and 75.2 h−1, respectively.
143
Scheme 2. One-pot synthesis of 1-aminoalkyl-2-naphthols.
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S. Sayyahi et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
t2:1
t2:2
Table 2
[C2OHmim]FeCl3Br− catalyzes synthesis of 1-aminoalkyl-2-naphthols from 2-naphthol, aryl aldehydes and acetamide.
t2:3
t2:4
Entry
1
Aldehyde
Producta
Time (min)
15
Yield (%)b
94
M.p. (°C) (Lit.)
242–244 (238–240)
t2:5
t2:6
t2:7
2
3
4
40
20
35
94
94
82
225–228 (220–222)
230–232 (228–230)
223–225 (226–228)
t2:8
5
30
93
238–240 (246–248)
t2:9
6
20
80
258–261 (260–262)
t2:10
7
70
80
187–190 (183–185)
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S. Sayyahi et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
5
Table 2 (continued)
t2:11
t2:12
Entry
8
Aldehyde
Producta
Time (min)
40
Yield (%)b
87
M.p. (°C) (Lit.)
221–224 (223–225)
t2:13
t2:14
t2:15
t2:16
9
45
60
75
15
92
206–210 (197–199)
202–205 (197–199)
188–191 (177–179)
236–239 (238–240)
OOF
91
10
11
12
90
91
UNCORRECTED10PR
t2:17
13
87
238–241 (245–247)
(continued on next page)
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S. Sayyahi et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
Table 2 (continued)
t2:18
t2:19
Entry
14
Aldehyde
Producta
Time (min)
110
Yield (%)b
94
M.p. (°C) (Lit.)
125–128 (119–121)
a
t2:20
t2:21
All products are known and were identified by comparison of their physical and spectral data with those of authentic samples [25,27,32].
Isolated yield.
b
144
With these optimized conditions in hand, we decided to examine
attack becomes easier to obtain ortho-quinomethide (c). Finally, 162
through condensation of (c) with acetamide after H+ transferring by 163
145 the scope and limitation of this MIL-catalyzed reaction. A wide variety
1Q466 of aryl benzaldehydes were applied and the results showed a highly
the catalyst, the desired 1-aminoalkyl-2-naphthol is generated.
164
147
effective performance of the catalyst in the preparation of 1-aminoalkyl-
2-naphthols as shown in Table 2. According to Table 2, the electron-
To show the efficiency and superiority of using [C2OHmim]FeCl3Br− 165
as catalyst for the synthesis of 1-amidoalkyl-2-naphthols, this proce- 166
dure has been compared with that of the previously reported methods 167
148
149 withdrawing groups enhance the reaction (entry 5, 6, 12) relative
150 to electron-donating groups, which decrease the reaction rate
151 (entry 7, 14). These effects can be explained in this way that, in the
1Q527 α,β-unsaturated intermediate (Scheme 3 (d)), the β-carbon is more
153 electrophilic with electron-withdrawing groups thus the rate is in-
154 creased. It is also noteworthy that the reaction time for the ortho-
155 substituted-substrates are prolonged; due to the steric hindrance.
in Table 3.
168
4. Conclusion
169
In conclusion, we have prepared a novel paramagnetic ionic liquid, 170
3-(2-hydroxyethyl)-1-methyl imidazolium bromotrichloro ferrate (III) 171
and characterized it by FT-IR, TGA, UV–Visible and Raman spectroscopy. 172
The MIL shows remarkable catalytic activity in the preparation of 1- 173
amidoalkyl-2-naphthol derivatives. In addition, the procedure provides 174
some advantages like easy workup, short reaction time and high isolated 175
156
It has been assumed that, magnetic ionic liquids could act as efficient
157 catalysts due to the synergic effect of the cation and anion [14]. A plau-
158 sible mechanism to rationalize this catalytic condensation is illustrated
159 (Scheme 3). Initially, the carbonyl group in aldehyde is activated by
160 the [C2OHmim]+ cation and meanwhile FeCl3Br− anion interacts with
161 the hydrogen in hydroxyl group of 2-naphthol. Hence, the nucleophilic
yields.
176
Scheme 3. The proposed mechanism for [C2OHmim]FeCl3Br−-catalyzed synthesis of 1-amidoalkyl-2-naphtols.
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t3:3
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