Synthesis of a novel multi-SO3H functionalized ionic liquid and its catalytic activities

Article abstract of DOI:10.1134/S0023158412020127

A novel multi-SO3H functionalized ionic liquid is synthesized and a detailed account of its cata- lytic activities in acetalization and acetylation is given. The results showed that the ionic liquid is very efficient in the conventional acid-catalyzed reactions with good to excellent yields within a short reaction time. Oper- ational simplicity, small amounts required, low cost of the catalyst, high yields, scalability and reusability are the key features of this methodology, which indicates the high potentialities of the novel ionic liquid to be used in environmentally friendly processes. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0023158412020127

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2012, Vol. 53, No. 3, pp. 301–305. © Pleiades Publishing, Ltd., 2012.
Synthesis of a Novel MultiꢀSO3H Functionalized Ionic Liquid
and Its Catalytic Activities1
Sun Xudong, Xiao Huiquan, Du Yijun, Zhang Jingjing, Liang Xuezheng, and Qi Chenze
Institute of Applied Chemistry, Shaoxing University, China
eꢀmail: xzliang@usx.edu.cn*, qichenze@usx.edu.cn**
Received March 19, 2011
Abstract—A novel multiꢀSO3H functionalized ionic liquid is synthesized and a detailed account of its cataꢀ
lytic activities in acetalization and acetylation is given. The results showed that the ionic liquid is very efficient
in the conventional acidꢀcatalyzed reactions with good to excellent yields within a short reaction time. Operꢀ
ational simplicity, small amounts required, low cost of the catalyst, high yields, scalability and reusability are
the key features of this methodology, which indicates the high potentialities of the novel ionic liquid to be
used in environmentally friendly processes.
DOI: 10.1134/S0023158412020127
Currently, ionic liquids (IL) are of intense interest immiscible with many organic solvents and they could
as media for a variety of reactions because of their be used as dual solvent and catalysts [6–12]. In most
properties such as very low or negligibly low vapor cases ionic liquids were functionalized with one sulꢀ
pressure, remarkable solubility and possibility to vary fonic acid group only and that resulted in a reduced
structure to control the parameters like density and acidity of the liquid compared to the acidity shown by
solubility, [1–3]. Recently, the synthesis of ionic liqꢀ conventional acid catalysts. The synthesis of multiꢀ
uids functionalized with sulfoalkyl groups was SO3H functionalized ionic liquids was reported in our
reported. Due to the combination of the advantages previous works [13, 14]. High activities showed by
offered by liquid and solid acids, e.g. uniform acid these ionic liquids prompted us to expand a variety of
sites, stability in water and air, easy separation and these multiꢀSO3H functionalized ionic liquids. Here
reusability, new possibilities for developing environꢀ we describe a novel strong Brønsted acidic ionic liquid
mentally friendly acidic catalysts can be envisaged [4]. with two SO3H groups. The novel ionic liquid was synꢀ
Since Cole et al. [5] first described functional IL with thesized using the reaction of N,N,N',N'ꢀtetramethylꢀ
strong Br
ø
nsted acidity, the research and application ethyleneꢀ1,2ꢀdiamine (TMEDA) and 1,2ꢀoxathianeꢀ
of various SO3H functionalized strong Br
ønsted acidic 2,2ꢀdioxide (Scheme 1). The catalytic activities of the
ionic liquids received an increased attention. Their novel ionic liquid in acetalization and acetalization
potential in replacing conventional homogenous/hetꢀ were investigated. The results show that the catalyst is
erogeneous acidic catalysts is considerable because very efficient in the conventional acidꢀcatalyzed reacꢀ
they are flexible, nonvolatile, noncorrosive and tions with the average yields over 90%.
The synthesis route of the novel ionic liquid
−
HSO4
O
O
+N
+N
S
−
SO3
O
H SO
2
4
+
N
N
−
SO3
SO 3H
+N
+N
−
HSO4
Scheme 1.
EXPERIMENTAL
Reagents
reactions without further purification. Cyclohexanone,
butanꢀ2ꢀone, butyraldehyde, cyclopentanone, benzaldeꢀ
hyde, methanol, ethanol, butanol and acetic anhydride
were purchased from “Shanghai Chemicals Co.”
All organic reagents were commercial products of
the highest purity available (>98%) and were used for the
1
The article is published in the original.
301

302
XUDONG et al.
Table 1. Acetalization of cyclohexanone and ethanediol
Amount of catalyst, mg
(mol %)
Entry
Reaction time, min
Conversion, %
Selectivity, %
1
2
3
4
5
6
30
30
30
30
40
50
10 (0.0856)
7 (0.0599)
5 (0.0428)
4 (0.0342)
4 (0.0342)
4 (0.0342)
98
98
97
89
98
99
100
100
100
100
100
100
Notes: All reactions were carried out under Dean–Stark conditions (cyclohexanone 20 mmol, ethaneꢀ1,2ꢀdiol 30 mmol, cyclohexane
10 mL). The yields were taken by GC according to cyclohexanone.
Synthesis of the Catalyst
Catalytic acetalization of oxo compounds
We used the next procedure for synthesizing the
novel IL. TMEDA (11.6 g, 0.1 mol) and 1,2ꢀ
oxathianeꢀ2,2ꢀdioxide (58.4 g, 0.4 mol) were mixed
O
O
O
catalyst
reflux
OH
+
OH
R1
R2
R2
R1
and stirred with a magnet for 72 h at 80
white solid zwitterion was filtrated and washed repeatꢀ
edly with ether. After drying up in vacuum (110 C,
°C. Formed
Scheme 2.
°
1.33 Pa), the white solid zwitterion was obtained in a
good yield (94%). A stoichiometric amount of sulfuric
acid was added to the zwitterion and the mixture was
stirred for 6 h at 80°C to form the ionic liquid. The IL
phase was then washed repeatedly with toluene and
ether to remove nonꢀionic residues, and dried in vacꢀ
Acetylation of Alcohols
Alkyl acetates were synthesized by the acetylation
of alcohols. In the typical procedure (Scheme 3), the
ionic liquid (50 mg) was added to a mixture of
hydroxyl compound (10 mmol) and acetic anhydride
at room temperature and the mixture was stirred at the
same temperature. The reaction was monitored by GC
analysis of the small aliquots withdrawn. When the
reaction was completed, the catalyst was recovered by
centrifugation. All the compounds were characterized
by GC–MS (Agilent 6890N GC/5973N MS, DMꢀ5MS)
and NMR 1H methods.
uum (110°C, 1.33 Pa). The product of high purity
(>98%) was formed quantitatively in the form of colꢀ
orless liquid (melting point 20–22°C, viscosity 78 ×
10–3 Pa s). The IL shows high thermal stability with the
1
decomposition temperature above 230
°
C
. NMR H
spectrum for the zwitterion (400 MHz, D2O, TMS):
1.74 (m, 4H), 1.91 (m, 4H), 2.91 (t, JH–H = 7.0 Hz,
4H), 3.14 (s, 12H), 3.40 (t, = 8.4Hz, 4H), 3.85
(s, 4H). IR spectrum in KBr, cm–1: 1037 and 907
δ
J
Catalitic acetylation of alcohols
(
⎯
SO3H), 1166 (C–N), 3409 (O–H).
O
catalyst
room temperature
+
R1 OH
R1 OAc
O
O
Acetalization of Carbonyl Compounds
Scheme 3.
Acetals were synthesized via the acetalization of
carbonyl compounds with diols. In the typical proceꢀ
dure (Scheme 2), carbonyl compound (0.1 mol),
cyclohexane (10 mL), diols and the catalyst were
mixed together in a 3–neck round bottom flask
equipped with a magnetic stirrer and thermometer. A
DeanꢀStark apparatus was used to remove the water
continuously from the reaction mixture. The mixture
was refluxed for a specified period. The progress of the
reaction was monitored by GC analysis of the small
aliquots withdrawn. When the reaction was comꢀ
pleted, the catalyst was recovered by centrifugation,
RESULTS AND DISCUSSION
Acetalization of Cyclohexanone
with Ethaneꢀ1,2ꢀdiol
At the first step, catalytic activity in the acetalizaꢀ
tion of cyclohexanone with ethaneꢀ1,2ꢀdiol was invesꢀ
tigated (Table 1). The results show that the novel ionic
liquid was very efficient
for the reaction. The high yield was achieved after a
short reaction time. The turnover number (TON) of
the reaction achieved a value of 2920.
washed with acetone and dried in an oven at 80
°C for
about 1 h.
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2012

SYNTHESIS OF A NOVEL MULTIꢀSO3H FUNCTIONALIZED IONIC LIQUID
303
Table 2. Preparation of various acetals from the corresponding carbonyl compounds
Entry
Substrate
Product
O
Reaction time, h
Yield, %
99
1
O
1.0
O
O
O
O
O
2
3
1.0
2.5
99
98
O
O
O
O
4
5
3.0
1.5
95
88
O
O
O
O
O
O
O
O
6
7
8
9
1.5
2.5
1.5
1.0
99
99
99
99
CHO
CHO
O
O
O
O
CHO
O
O
CHO
CHO
10
11
1.5
1.5
89
99
O
O
O
CHO
O
O
O
12
1.5
98
CHO
CHO
13
14
1.5
1.5
97
95
O
O
O
Notes: All reactions were carried out under Dean–Stark conditions (catalyst 0.15 g, diols 0.14 mol, carbonyl compound 0.1 mol, cycloꢀ
hexane 10 mL, refluxed for 1.5 h). The conversion and selectivity were taken by GC according to carbonyl compounds. In all
cases, the corresponding products were exclusively obtained.
KINETICS AND CATALYSIS Vol. 53
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2012

304
XUDONG et al.
Table 3. Preparation of various acetates from hydroxyl compounds
Entry
1
Substrate
OH
Product
OAc
OAc
Reaction time, min
10
Yield, %
99
2
3
4
5
10
10
15
10
99
99
99
99
OH
OH
OH
OH
3
3
4
OAc
4
OAc
OAc
11
11
OAc
OAc
OH
OH
6
10
99
7*
8*
10
20
99
99
HO
HO
AcO
AcO
OH
OAc
Notes: All reactions were taken at room temperature (25°C), hydroxyl compounds 10 mmol, acetic anhydride 15 mmol, catalyst 5 wt %.
The yields were taken by GC.
*Hydroxyl compounds 10 mmol, acetic anhydride 24 mmol.
Acetalization of Carbonyl Compounds
is efficient, with almost quantitative conversion and
exclusive selectivity for the most of reactions. Aliꢀ
phatic aldehydes were transformed to the correspondꢀ
ing acetals smoothly under the reaction conditions
(entries 11–14). Aromatic aldehyde, such as benzalꢀ
dehyde could also be acetalized to afford the correꢀ
sponding 1,3ꢀacetal with the yield of 99% (entries 7–
10), The linear chain ketone (butanone) showed a relꢀ
atively low activity and reacted with a product yield of
88% (entry 5). Not only the traditional five and six
member ring acetals were formed smoothly, but also
the seven member ring products could be formed sucꢀ
cessfully in high yields (entries 1–4, 7–10), The activꢀ
ities in the transformation of butanediol were someꢀ
what lower than in the case of ethanediol because of
the steric hindrances and stability of the correspondꢀ
ing products (entries 1 and 4, 11 and 14, 7 and 10). The
aldehydes show much higher reactivities than the
ketones due to the presence of more active carbonyl
groups (entries 5, 11, 14).
To study the scope of this protocol, the acetalizaꢀ
tion of various carbonyl compounds and alcohols catꢀ
alyzed by the novel IL was performed (Table 2). As
expected, all carbonyl compounds were successfully
transformed into the corresponding acetals. The
results in Table 2 clearly demonstrate that the novel IL
Yield, %
100
80
60
40
20
0
The ReꢀUse of the Catalyst
One of properties of the novel catalyst is the reusꢀ
ability of the catalyst. We received evidence that the
recovery of the catalyst is very easyꢀtoꢀuse. Once a
reaction was completed, the reaction mixture was
extracted with ethyl acetate and ethyl ether mixture
(1 : 1) and the lower phase, the ionic liquid, could be
reused easily. Activities of recovered catalysts were
investigated through the reaction of benzaldehyde and
1
2
3
Run number
4
5
The reꢀuse of the catalyst.
KINETICS AND CATALYSIS Vol. 53
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SYNTHESIS OF A NOVEL MULTIꢀSO3H FUNCTIONALIZED IONIC LIQUID
305
glycol carefully (see Diagram). The yields remained
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