Novel double-SO3h functionalized ionic liquid for acetylation

Article abstract of DOI:10.1134/S0023158412060080

Novel double-SO₃H functionalized ionic liquid (DFIL) was synthesized and its catalytic activities for acetylation studied. The result showed that the DFIL possess high acidity and was very efficient for the acetylation of alcohols, amines and phenols with good to excellent yields in short reaction times. Operational simplicity, stability to water and air, small amounts needed, low cost, high yields, high acidity, applicability to large-scale reactions and reusability are the key features of the DFIL, which indicated promising applications of DFIL in green chemical processes. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0023158412060080

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2012, Vol. 53, No. 6, pp. 684–688. © Pleiades Publishing, Ltd., 2012.
Published in Russian in Kinetika i Kataliz, 2012, Vol. 53, No. 6, pp. 728–732.
Novel DoubleꢀSO3H Functionalized Ionic Liquid for Acetylation1
Lili Zhu and Xuezheng Liang
Institute of Applied Chemistry, Shaoxing University, Shaoxing 312000, China
eꢀmail: xzliang@usx.edu.cn
Received September 21, 2011
Abstract—Novel doubleꢀSO3H functionalized ionic liquid (DFIL) was synthesized and its catalytic activities
for acetylation studied. The result showed that the DFIL possess high acidity and was very efficient for the
acetylation of alcohols, amines and phenols with good to excellent yields in short reaction times. Operational
simplicity, stability to water and air, small amounts needed, low cost, high yields, high acidity, applicability to
largeꢀscale reactions and reusability are the key features of the DFIL, which indicated promising applications
of DFIL in green chemical processes.
Keywords: multiꢀSO3H functionalized ionic liquid, acetylation
DOI: 10.1134/S0023158412060080
1. INTRODUCTION
Here we present a novel double SO3H functionalꢀ
ized ionic liquid (DFIL) with one SO3Н attached to
the tertiary amine and the other through sulfonation.
The DFIL was synthesized through three steps. In the
first step, zwitterion was obtained through the conꢀ
densation of isoquinoline and 1,4ꢀbutane sulfonate.
Next, doublemolar sulfuric acid and zwitterion were
mixed together to form the homogeneous liquid phase
(Scheme 1). The catalytic activities of the DFIL for
acetylation were investigated. The results showed that
the DFIL was very efficient in the reactions with the
average yields over 90% obtained within several minꢀ
utes.
Ionic liquids are widely used in chemical reactions
because they are fluxible, nonvolatile, nonꢀcorrosive
and immiscible with many organic solvents and could
be used as dual solvents and catalysts [1⎯3]. Ionic liqꢀ
uids functionalized by chloride and sulfoalkyl groups
were reported as the environmentalꢀfriendly acid catꢀ
alysts due to the combination of the advantages of liqꢀ
uid and solid acids, e.g. uniform acid sites, easy sepaꢀ
ration and reusability [4]. Chloride ionic liquids were
found to be very efficient in various reactions such as
alkylation for their strong acidity, but these ionic liqꢀ
uids were often very sensitive to water.
Cole et al. [5] first reported the functional ionic liqꢀ
uid (FIL) with strong Bransted acidity, which was staꢀ
ble to the action of water. Later, the research and
application of various –SO3Н functionalized ionic liqꢀ
uids have received increasing attention [6–12]. Proꢀ
tection of functional groups is highly essential in
organic synthesis. The protection of alcohols, phenols
and amines are fundamental and useful transformaꢀ
tions in organic synthesis. Among many protecting
methods, acetylation is an important and routinely
utilized transformation in organic chemistry because
of the facile introduction, high stability in acid reacꢀ
tion conditions and removability by mild alkaline
hydrolysis [13–15]. In our earlier works extremely
high activities of duebleꢀSO3Н functionalized ionic
liquids for the traditional acidꢀcatalyzed reactions was
demonstrated [16, 17], These –SO3Н groups were
introduced through the addition reaction to the terꢀ
tiary amines, which added the charges of the positive
ions and lead to the higher polarity of the resulting
ionic liquid.
The synthesis route of the DFIL
+
O
S
O
O
R. T. (25°C)
72 h
N
O−
O
+
S
O
HO3S
–
HSO4
H SO
2
140
4
N
OH
ᮀ
+
S
O
O
Scheme 1.
2. EXPERIMENTAL
All organic reagents were commercial products of
the highest purity available (>98%) and were used for
the reactions without further purification. Isoquinoꢀ
line, 1,4ꢀbutane sulfonate, butanone, 1,2ꢀpropylene
1
The article is published in the original.
684

NOVEL DOUBLEꢀSO3H FUNCTIONALIZED IONIC LIQUID FOR ACETYLATION
685
Table 1. The acetylation of various alcohols
glycol, neopentyl glycol, cyclohexamine, dimethyꢀ
lamine, morpholine, were purchased from Shanghai
Chemicals Co.
Reaction
time, min
Entry
Alcohols
OH
Products
OAc
1
2
1
1
2.1. Synthesis of the Novel Double Functionalized
Ionic Liquid (DFIL)
OH
OAc
The procedure for synthesizing the novel ionic liqꢀ
uid (DFIL): isoquinoline (12.9 g, 0.1 mol) and
1,4ꢀbutane sulfonate (13.6 g, 0.1 mol) were mixed and
stirred magnetically for 72 h at room temperature.
Then, the white solid zwitterion was formed. The
white solid zwitterion was filtrated and washed repeatꢀ
3
4
3
4
OH
OAc
OH
OH
OAc
OAc
5
15
edly with ether. After dried in vacuum (110 С,
°
1.33 Pa), the white solid zwitterion was obtained in
good yield (94%). A doublemolar amount of sulfuric
acid was added to the above obtained zwitterion and
6
7
4
5
3OH
7OH
4OH
3 OAc
7 OAc
4 OAc
the mixture was stirred for 4 h at 60
homogeneous liquid phase. Then, sulfonation was taken
in vacuum (140 С, 1.33 Pa) to remove the water. The
°
С to form the
°
DFIL was formed quantitatively and in high purity.
1H NMR were measured on Bruker AVANCE
400M for the zwitterion (400 MHz, D2O, TMS):
8
9
5
5
δ
1.75 (m, 2H), 2..17 (m, 2H), 2.90 (t, JH–H = 7.2 Hz,
OH
OAc
2H), 4.67 (t, JH–H = 7.2 Hz, 2H), 8.10 (d, 2H), 8.29
(d, 2H), 8.41 (s, 1H), 9.60 (s, 1H).
HO
HO
AcO
AcO
IR (KBr) was measured on NEXUS 670 FTꢀIR
Analyzer: 1037 cm–1 and 907 cm–1 (–SO3H), 1166 cm–1
(C–N), 3409 cm–1 (O–H).
10
11
7
5
OH
OAc
OH
OAc
HO
OH AcO
OAc
2.2. The Acetylation of Alcohols,
Amines and Phenols
Note: The reaction conditions: alcohol 20 mmol, caculated on
the hydroxyl groups, acetic anhydride 24 mmol, ionic liqꢀ
uid, 0.04 g, 0.1 mmol, R.T., 25°C. The yield was estimated
by GC analysis. The product yields were of 99% except for
tertꢀBuOH, entry 5.
The acetylation was taken as follows. In the typical
procedure the catalyst (50 mg) is added to a mixture of
alcohols, amines or phenols (20 mmol) and acetic
anhydride (24 mmol) at room temperature and stirred
at the same temperature. The reaction was monitored
by GC analysis of the small aliquots withdrawn. After
completion of the reaction, the catalyst was recovered
by centrifugation. All the products were fully characꢀ
terized by GC–MS (Agilent 6890N GC/5973N MS,
DM–5MS) and the usual spectral methods (NMR
and IR).
3. RESULTS AND DISCUSSIONS
3.1. The Acetylation of the Alcohols
Various alcohols have been used as substrates to
react with acetic anhydride over the DFIL. The results
in Table 1 clearly demonstrate that the novel catalyst is
very efficient with almost complete conversion for
most reactions within several minutes. Using a small
amount of the catalyst under mild and simple reaction
conditions (at room temperature in air), all the alcoꢀ
hols underwent smooth transformation to the correꢀ
sponding products in excellent yields with strong exoꢀ
thermic phenomenon. The reactivity of the liner alcoꢀ
hols was very efficient and almost the stoichiometric
amount of products obtained in very short time. Not
only the primary alcohols entered the reactions
smoothly, but also the secondary alcohol and tertꢀ
alcohol show high reactivity in the catalytic system
The acetylation of alcohols, amines and phenols
O
R
O
R OH
O
O
Cat
R. T. (25°C)
+ AcOH
+
H
R NH2
N
O
R
O
Scheme 2.
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2012

686
ZHU, LIANG
Products
Table 2. The acetylation of various phenols
Entry
Phenols
Reaction time, min
6
Yield, %
99
1
OH
OAc
2
3
4
8
99
97
OH
OAc
OH
OAc
OH
OH
OAc
OAc
4
7
97
5
6
7
5
98
99
HO
OH
AcO
OAc
OH
OH
OAc
OAc
7
8
7
8
97
98
OH
OAc
HO
AcO
OH
OAc
9
9
99
HO
OH
AcO
OAc
Note: The reaction conditions: phenol 20 mmol, caculated on the hydroxyl groups, acetic anhydride 24 mmol, ionic liquid, 0.04 g,
0.1 mmol, R.T., 25 C. The yield was estimated by GC analysis.
°
(entries 3⎯5) and no rearrangement products were acetylated when the compounds with more hydroxyl
discovered during the processes. The tertꢀbutanol groups and enough acetic anhydride were introduced
reached a peak value of 95% within 15 min probably to the reaction condition (entry 11).
because of the high steric hindrance of the hydroxyl
groups with low selectivity to alkene (entry 5). Also, the
diols underwent the reactions smoothly with both
3.2. The Acetylation of the Phenols
hydroxyl groups acetylated. The exothermic reaction
Besides the alcohols, the catalytic activities of pheꢀ
of the acetylation accelerated the reaction of the rest nols were also investigated. The results showed that the
hydroxyl groups (entries 9, 10). When the equimolar DFIL is also very efficient for the phenols with almost
mixture of ethandiol and acetic anhydride were used complete conversion (Table 2). The methyl attached
for the reaction, both the single and double acetylation to the
products were obtained, which indicated that the reacꢀ those in the
tions of the double hydroxyl groups occurred simultaꢀ tute in the
neously. Both the hydroxyl groups could be acetylated steric hindrance (entries 2, 4, 5). The tertꢀbutyl group
to the corresponding products when more than double attached to the
ꢀposition further decreased the reacꢀ
p
ꢀposition showed relatively higher activity than
ꢀ and ꢀposition. With the methyl substiꢀ
ꢀposition, the yield was reduced due to the
m
o
o
p
acetic anhydride was introduced to the reaction sysꢀ tivity because of the steric hindrance (entry 3). Both
tems (entries 9, 10). All the hydroxyl groups were hydroxyl groups were acetylated when two hydroxyl
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NOVEL DOUBLEꢀSO3H FUNCTIONALIZED IONIC LIQUID FOR ACETYLATION
Table 3. The acetylation of various amines
687
Entry
Phenols
Products
Reaction time, min
Yield, %
1
10
98
NH2
NHAc
2
25
94
NH2
NHAc
3
4
5
20
15
5
96
97
99
NH2
NH2
NH
NHAc
NHAc
NAc
O
O
6
15
94
NH
NAc
Note: The reaction conditions: amine 20 mmol, acetic anhydride 24 mmol, ionic liquid, 0.04 g, 0.1 mmol, R.T., 25
estimated by GC analysis.
°
C. The yield was
Table 4. The comparison of different catalysts
Entry
Phenols
Products
Reaction time, min
Yield, %
1
2
3
4
5
6
DFIL
0.1
1.0
2.0
5.5
2.5
6.5
25
35
94
90
88
80
90
80
H2SO4
p
ꢀCH3C6H4SO3H
60
BF3–OEt2
90
[imibSO3H][HSO4]
ZnCl2
30
120
Note: All reactions were taken at R.T., 25°C, conditions: aniline: 10 mmol; acetic anhydride: 15 mmol. GC yields.
groups were connected with the aromatic ring. The the aromatic ring and the nitrogen, which reduced the
reactions occurred quickly for the compounds with electron density of the nitrogen atom (entry 2). The
multiꢀhydroxyl groups. The exothermic reaction for reactivity of amines increased with the methyl group
the first hydroxyl group activated the rest ones and attached to the aromatic ring, which enhanced the
accelerated the reaction that was completed within electronic density (entry 3). As to the aliphatic
several minutes (entries 6
the highest activity for the less steric hindrance drances (entries 1, 4
⎯
8). Hydroquinone showed amines, their reactivity was affected by the steric hinꢀ
6). Morpholine showed
⎯
(entry 6). All the hydroxyl groups could be easily extremely high activity because the Nꢀatom enters the
acetylated under the reaction conditions and three 6ꢀmember ring, and in this way reduces the steric hinꢀ
hydroxyl groups in phloroglucinol were all acetylated drance greatly (entry 5). Both the primary and secondꢀ
within 9 min with almost complete conversion ary amines could be acetylated with high yields
(entry 9).
(entries 4, 6) and the primary amine often attain
higher yields than the secondary amines because of the
reduced steric hindrances (entries 4, 6).
3.3. The Acetylation of the Amines
The amides are also very important in chemical
industry. The results of the acetylation of various
amines are collected in Table 3. As shown in the Table
3.4. The Reuse of the Catalyst
A certain merit of the DFIL is the reusability. We
the amines possess relatively low reactivity than pheꢀ showed that the recovery of the catalyst was very conꢀ
nols in the neutralization reaction occurred with the venient. After reactions, the reaction mixture was
catalyst and acetic anhydride. Lower activities of aroꢀ extracted with ethyl acetateꢀethyl ether = 1 : 1 and the
matic amines can be attributed to the conjugation of lower phase, the ionic liquid, could be reused easily.
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688
ZHU, LIANG
The activities of the recovered DFIL were investigated
in the reaction of butanol with acetic anhydride. The
results indicated that the yields remained unchanged
even after the catalyst had been recycled for five times.
REFERENCES
1. Jiang, Y.ꢀY., Wang, G.ꢀN., Zhou, Z., Wu, Y.ꢀT., Geng, J.,
and Zhang, Z.ꢀB., Chem. Commun., 2008, p. 505.
2. Kuang, D., Uchida, S., HumphryꢀBaker, R., Zakeerꢀ
uddin, S.M., and Graetzel, M., Angew. Chem. Int. Ed.
2008, vol. 47, p. 1923.
,
3.5. The Comparative Study on the Catalytic Activities
of the Different Catalysts
3. Singh, T. and Kumar, A., J. Phys. Chem. B, 2008,
vol. 112, p. 4079.
A comparative study on the catalytic activities of
the DFIL with the traditional catalysts was carried out
using the reaction of aniline and acetic anhydride
(Table 4). From this study it can be concluded that
activities of the DFIL and the homogeneous catalysts
were commensurable, furthermore the DFIL has the
additional advantage of reusability. The extremely
high acidity and lower polarity made the DFIL more
active than the traditional single –SO3H functionalꢀ
ized ionic liquid. It clearly shows that the DFIL should
be considered as one of the best choice for the ecoꢀ
nomically convenient, environmentally friendly cataꢀ
lyst and suitable for the scaling up purpose.
4. Gupta, N.S., Kad, G.L., and Singh, J., Catal. Comꢀ
mun., 2007, vol. 8, p. 1323.
5. Cole, A.C., Jensen, J.L., Ntai, I., Tran, K.L.T.,
Weaver, K.J., Forbes, D.C., and Davis, J.H., J. Am.
Chem. Soc., 2002, vol. 124, p. 5962.
6. Sugimura, R., Qiao, K., Tomida, D., and Yokoyama, C.,
Catal. Commun., 2007, vol. 8, p. 770.
7. Silveira, NetoB.A., Ebeling, G., Goncalves, R.S.,
Gozzo, F.C., Eberlin, M.N., and Dupont, J., Synthesis
2004, p. 1155.
,
8. Wu, H.ꢀH., Yang, F., Cui, P., Tang, J., and He, M.ꢀY.,
Tetrahedron Lett., 2004, vol. 45, p. 4963.
9. Kamal, A. and Chouhan, G., Adv. Synth. Catal., 2004,
vol. 346, p. 579.
4. CONCLUSION
10. Yadav, J.S., Reddy, B.V.S., and Kondaji, G., Chem.
Lett., 2003, vol. 32, p. 672.
The novel multiꢀSO3H functionalized ionic liquid
was synthesized through three steps. The catalytic
activities of the DFIL for acetylation were investiꢀ
gated. The results showed that the DFIL was very effiꢀ
cient in the reactions with the average yields over 90%
obtained within several minutes. Because of the
extremely high acidity and low polarity the DFIL
show much higher activity than the traditional acid
catalyst and ionic liquids. The DFIL also hold great
potential to replace the tradition homogeneous acid
catalysts in the environmentally friendly processes.
11. Kamal, A. and Chouhan, G., Tetrahedron Lett., 2003,
vol. 44, p. 3337.
12. Firouzabadi, H., Iranpoor, N., Jafari, A.A., and
Jafari, M.R., J. Mol. Catal. A: Chem., 2006, vol. 247, p. 14.
13. Zhang, D., Wang, G., and Zhu, R., Tetrahedron: Asymꢀ
metry, 2008, vol. 19, p. 568.
14. Singh, R. and Goswami, T., J. Phys. Org. Chem., 2008,
vol. 21, p. 225.
15. Wang, C.ꢀJ., Zhang, Z.ꢀH., Dong, X.ꢀQ., and Wu, X.ꢀJ.,
Chem. Commun., 2008, p. 1431.
ACKNOWLEDGMENT
16. Liang, X., Gao, S.‚ Yang, J., and He, M., Catal. Lett.
2008, vol. 125, p. 396.
,
This work was supported by Zhejiang Xinmiao talent
projects Foundation No. 2011R426013 and Zhejiang
Science and technology projects (2010C31G2180006).
17. Liang, X., Wang, Y.‚ Gong, G.‚ and Yang, J., Catal.
Commun., 2008, vol. 10, p. 281.
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2012