Crown ether complex cation ionic liquids: Preparation and applications in organic reactions

Article abstract of DOI:10.1002/chem.201100112

A series of crown ether complex cation ionic liquids (CECILs) were designed, synthesised and characterised by NMR spectroscopy, HRMS, thermogravimetric differential thermal analysis (TG-DTA) and elemental analysis. Their applications in various organic reactions were investigated: [15-C-5Na][OH], [15-C-5Na][OAc], [18-C-6K][OH] and [18-C-6K][OAc] (15-C-5=[15]crown-5; 18-C-6=[18]crown-6) efficiently catalysed the Michael addition of alkenes and relevant nucleophiles; [18-C-6K][OH] and [15-C-5Na][OH] effectively catalysed the Henry reaction of nitromethane and aromatic aldehydes; [18-C-6K][OH] has excellent catalytic efficiency for Knoevenagel condensation of aromatic aldehydes and malononitrile; PdCl₂/[18-C-6K] ₃[PO₄]/K₂CO₃ efficaciously catalysed the Heck reaction of olefins and aromatic halides; [18-C-6K][BrO₃] can be used as both oxidant and solvent in the oxidation reaction of aromatic alcohols. The CECIL catalysts [15-C-5Na][OH] (Michael addition) and [18-C-6K][OH] (Henry reaction) can be recycled and reused several times without obvious loss of activity and their recovery is very simple.

Full text of DOI:10.1002/chem.201100112

FULL PAPER
DOI: 10.1002/chem.201100112
Crown Ether Complex Cation Ionic Liquids: Preparation and Applications in
Organic Reactions
Yingying Song, Huanwang Jing,* Bo Li, and Dongsheng Bai[a]
Abstract: A series of crown ether com-
plex cation ionic liquids (CECILs)
were designed, synthesised and charac-
terised by NMR spectroscopy, HRMS,
thermogravimetric differential thermal
analysis (TG-DTA) and elemental
analysis. Their applications in various
organic reactions were investigated:
Michael addition of alkenes and rele-
vant nucleophiles; [18-C-6K][OH] and
[15-C-5Na][OH] effectively catalysed
the Henry reaction of nitromethane
and aromatic aldehydes; [18-C-6K]
[OH] has excellent catalytic efficiency
for Knoevenagel condensation of aro-
matic aldehydes and malononitrile;
PdCl2/A[18-C-6K]3A[PO4]/K2CO3 effica-
ciously catalysed the Heck reaction of
olefins and aromatic halides; [18-C-
G
CHTUNGTRENNUNG
6K]ACTHNURTGNENG[U BrO3] can be used as both oxidant
and solvent in the oxidation reaction of
aromatic alcohols. The CECIL catalysts
[15-C-5Na][OH] (Michael addition)
and [18-C-6K][OH] (Henry reaction)
can be recycled and reused several
times without obvious loss of activity
and their recovery is very simple.
[15-C-5Na][OH],
[18-C-6K][OH] and [18-C-6K]
(15-C-5=[15]crown-5; 18-C-6=
[15-C-5Na]AHCTUNGTRENNNUG
Keywords: crown compounds
·
AHCTUNGTRENNUNG
Heck reaction · Henry reaction ·
ionic liquids · Michael addition
[18]crown-6) efficiently catalysed the
Table 1. The properties of the CECILS.
Introduction
Entry CECIL
Colour
M.p. [8C][a] Td [8C][b]
Ionic liquids (ILs), defined as molten salts at temperatures
lower than 1008C, have received overwhelming interest be-
cause of their unique properties, such as lack of significant
vapour pressure, ease of reuse, absence of flammability and
tolerance for large temperature variations.[1] ILs have been
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
N
G
white
white
white
white
orange
white
yellow
white
white
white
white
orange
white
yellow
yellow
38
37
39
145
202
189
200
171
192
171
213
197
203
182
147
200
174
154
167
211
R
R
77
171
174
153
92
44
113
39
À54
179
115
116
used in a number of organic reactions, for example, hydro-
[2]
À
genation, oxidation and C C bond-forming reactions. Al-
though thousands of ILs were synthesised in the past de-
cades, they commonly consisted of N,N’-dialkylimidazolium
or N-alkylpyridinium cations.[3] Besides these organic cat-
ions, could other cations be incorporated into ILs? It is
known that electrostatic interactions between large cations
and large anions are relatively weak, whereas the van der
Waals forces are strong, which induces a decrease in lattice
energy and melting point.[4] Based on these fundamental un-
derstandings, we designed and synthesised a series of novel
crown ether complex cation ionic liquids (CECILs), which
have melting points lower than 2008C, composed of crown
ether chelated alkali metal cations and various anions
(Table 1). Furthermore, to demonstrate the practicality of
these novel CECILs, they have been applied in various
carbon–carbon bond-forming reactions, such as Michael ad-
dition, Henry reaction, Knoevenagel condensation and
colourless 167
[a] All melting points were determined on a XT-4 melting point appara-
tus without calibration. [b] Decomposition temperatures (Td) were deter-
mined by TG-DTA, heating at 108CminÀ1 under nitrogen.
Heck reaction. The excellent results are disclosed in this
paper.
The Michael addition reaction is a useful method for
carbon–carbon bond formation and has been efficiently ex-
tended for carbon–sulfur and carbon–nitrogen bond forma-
tion.[5] The products of Michael addition not only constitute
components of biologically active natural products, but also
serve as key intermediates for many important organic com-
pounds.[6] Herein, the simple CECIL [15-C-5Na][OH] (15-C-
5=[15]crown-5) was applied in Michael/aza-Michael addi-
tions as an efficient catalyst. Another important pathway to
construct carbon–carbon bonds is the palladium-catalysed
arylation and vinylation of olefins by aryl and vinyl halides
[a] Dr. Y. Song, Prof. H. Jing, Dr. B. Li, Dr. D. Bai
State Key Laboratory of Applied Organic Chemistry
College of Chemistry and Chemical Engineering, Lanzhou University
Lanzhou, Gansu, 730000 (P. R. China)
Fax : (+86)931-891-2582
E-mail: hwjing@lzu.edu.cn
Chem. Eur. J. 2011, 17, 8731 – 8738
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
8731

or their derivatives, known as the Heck reaction.[7] In this
paper, CECILs [18-C-6K]3A[PO4], [18-C-6K]2A[HPO4] and [18-
C-6K][H2PO4] (18-C-6=[18]crown-6) were successfully ap-
nucleophilicities. Therefore, organic reactions traditionally
catalysed by a base, such as Michael addition, Henry reac-
tion and Knoevenagel condensation, have been used to test
the catalytic abilities of our new ILs [18-C-6K][OH], [15-C-
G
CHTUNGTRENNUNG
ACHTUNGTRENNUNG
plied in the Heck reactions of olefins and aromatic halides.
The Henry (or nitroaldol) reaction, catalysed by organic and
inorganic bases, is also a convenient method for direct
carbon–carbon bond formation to give bifunctional b-hy-
droxynitroalkanes.[8] The products are useful intermediates
in the preparation of nitroalkenes, a-nitroketones and b-
aminoalcohol derivatives, such as ephedrine and norephe-
drine.[9] Herein, the Henry reaction of nitromethane and ar-
omatic or aliphatic aldehydes catalysed by [18-C-6K][OH] is
reported. The Knoevenagel condensation, which is also a
very useful reaction and has been widely employed for
carbon–carbon bond formation in organic synthesis,[10] is
usually catalysed by a base. We found that the CECIL [18-
C-6K][OH] showed an excellent catalytic efficiency in the
Knoevenagel condensation of aromatic aldehydes and malo-
nonitrile. Oxidation reactions are among the most important
transformations in synthetic chemistry and are an important
tool for the introduction and modification of functional
groups.[11] We report our investigation on the oxidation of
5Na][OH], [18-C-6K]
CECILs [18-C-6K]3A[PO4], [18-C-6K]
[H2PO4] containing phosphorous anion were used in Heck
reactions as additives. And the CECIL [18-C-6K][BrO3] was
applied to the oxidation of aromatic alcohols. All these ILs
dissolve well in strong polar solvents, such as water, metha-
nol, ethanol, acetone and acetonitrile; we chose methanol as
the reaction media in our investigations.
The Michael addition is traditionally catalysed by strong
bases.[12] ILs have recently been used as catalysts and sol-
vents in Michael additions.[13] The complexation of a potassi-
um or sodium cation to a crown ether increases the radius
of the cation, which decreases the electrostatic interactions
between ion pairs and, consequently, enhances the basicity/
nucleophilicity of the anion in [15-C-5Na][OH] and [18-C-
6K][OH]. Alkaline CECIL of [15-C-5Na][OH] was used to
catalyse the Michael/aza-Michael addition of carbon, sulfur
and nitrogen nucleophiles and olefins under mild conditions,
generating branched carbonyl compounds in high yields
G
ACHTUNGTRENN[UNG OAc]. The
E
CHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
aromatic alcohols by using [18-C-6K]
and solvent.
ACHTUNGRTEN[NNUG BrO3] as both oxidant
À
À
(Scheme 1, Table 2). We emphasise that the C S and C N
Results and Discussion
With the understanding of interaction of the ion pairs, we
dissolved the crown ether and relevant inorganic/organic
salt or inorganic base in water to generate our desired
CECIL. The obtained CECILs have high purity, shown by
sharp melting points (Table 1). They have good stabilities
measured by TG-DTA. All of the CECILs synthesised are
solids at room temperature, except [15-C-5Na][OH], and
they range from colourless to orange. It can be seen that
almost all of the products prepared with [18]crown-6 are
white solids (Table 1, entries 1–4, 6, 8–11, 13, 17), whereas
the products prepared with [15]crown-5 have different col-
ours (Table 1, entries 5, 7, 12, 15). CECILs prepared from
bromide, chlorate, bromate and iodate have melting points
higher than 1008C, whereas small anion CECILs possess
melting points lower than 1008C. The formation of [18-C-
6K][X] and [15-C-5Na][X] is a simple reaction carried out
by mixing the correct molar ratio of crown ether and rele-
vant salts in water, followed by evaporation and, finally, de-
siccation under vacuum. If we define CECILs as molten
salts at temperatures lower than 2008C, all 17 CECILs are
consistent with the new concept. The CECILs obtained are
thermally stable up to 150–2208C, a little lower than the
thermal stability of imidazolium cation ILs. The decomposi-
tion of CECILs might be attributed to damage of their li-
gands. Impurities in ILs can affect their melting point and
reduce their catalytic abilities.
Scheme 1. Michael addition of nucleophiles to a, b-unsaturated carbonyl
compounds.
bond-forming reactions catalysed by [15-C-5Na][OH] can be
achieved within 30 min at 258C (Table 2, entries 1, 3–8, 13–
18). In particular, the Michael addition of butanethiol to
chalcone can be completed within 5 min in the presence of
[15-C-5Na][OH] (Table 2, entry 1) or [18-C-6K][OH]
(Table 2, entry 2) to generate the product in 98% yield,
which are much more efficient than the traditional IL 1-
pentyl-3-methylimidazolium bromide ([pmIm][Br]) (Table 2,
entry 2).[13a] For the Michael addition of piperidine to
methyl acrylate (Table 2, entry 15), better results were ob-
tained when catalysed by [15-C-5Na][OH] or [15-C-5Na]-
A
ACHTUNGTRENNUNG[OAc]
AHCTUNGTRENNUNG
À
formation of C C bond was a much slower process, by
À
reason that the C H bond of the nucleophile is harder to
activate (Table 2, entries 21–24). When the olefin was acryl-
amide, the reaction gave low yields for the conjugation of
an amide (Table 2, entries 12, 20). When imidazole was used
as the nucleophile a similar phenomenon was observed
(Table 2, entry 19).
The reaction of chalcone and butanethiol was chosen as a
model reaction to investigate the recycling of [15-C-5Na]
[OH]. The recycling results showed that the catalyst did not
lose its activity after five cycles (Table 2, entry 1). For inves-
tigation of the solvent effect on catalyst [15-C-5Na][OH],
The electrostatic interactions between cations and anions
are reduced in CECILs relative to their precursors, thus, we
speculate that the anions of CECILs would have stronger
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Crown Ether Complex Cation Ionic Liquids
FULL PAPER
Table 2. Michael addition catalysed by [15-C-5Na][OH].[a]
Table 2. (Continued)
Entry Olefin
Entry Olefin
Nucleo-
phile
Product
t
A
Yield
Nucleo-
phile
Product
t
A
Yield
[min] [%][b]
[min] [%][b]
98.0
96.2[c]
97.0[c]
98.0[c]
96.5[c]
97.5[d]
95.0[e]
24
480
90.0[i]
1
BuSH
5
[a] Reaction conditions: olefin (1 mmol), nucleophile (1.3 mmol), catalyst [15-
C-5Na][OH]·H2O (0.1 mmol), CH3OH (1 mL), T=258C. [b] Isolated yield.
[c] Recycled catalyst used. [d] [18-C-6K][OH] (0.1 mmol) was used as cata-
5
60
2
3
BuSH
BuSH
lyst. [e] See reference [13a]. [f] [15-C-5Na]ACTHUNRGTNEUNG[OAc] (0.1 mmol) was used. [g] See
reference [13h]. [h] Chalcone (0.2 mmol), CECIL (0.25 g), neat. [i] T=508C,
the amount of [15-C-5Na][OH] 0.5 mmol.
20
99.0
4
5
BuSH
BuSH
20
30
85.0
87.4
the reaction of chalcone and nitromethane was chosen as a
model reaction. Surprisingly, the reaction time was reduced
from 210 to 140 min when [15-C-5Na][OH] was used as sol-
vent and catalyst and the yield was enhanced from 55.3 to
82%. This phenomenon was evidence of the positive sol-
vent effect of the novel CECILs (Table 2, entry 22).
6
7
8
BuSH
BuSH
BuSH
25
25
30
99.0
99.0
87.3
We know that Michael addition is usually carried out
under strong base catalysis to avoid side reactions. Strange-
ly, our weaker base catalysts [18-C-6K]
ACHTUNGTREN[NUNG OAc] or [15-C-
9
10
11
12
42
55
99.7
94.1
86.2
41.3
5Na][OAc] also gave high yields without any byproducts
AHCTUNGTRENNUNG
under mild conditions (Table 3). These phenomena were
consistent with our understandings of the enhancements of
the basicity/nucleophilicity of the anion of CECILs.
115
360
Table 3. Michael addition catalysed by [18-C-6K]ACTHNUTRGNEUNG
[OAc].[a]
Type
Olefin
Nucleophile
t
Yield
[%][b]
AHCTUNGTERG[NNUN min]
13
14
20
83.0
83.0
99.0
97.0[c]
95.0
92.0
À
C S
chalcone
butanethiol
30
À
20
C C
chalcone
ethyl acrylate
malononitrile
piperidine
60
20
À
C N
20
20
90
99.0
[a] Reaction conditions: olefin (1 mmol), nucleophile (1.3 mmol), catalyst
[18-C-6K][OAc]·2.5H2O (0.1 mmol), CH3OH (1 mL), T=258C. [b] Isolat-
ed yield. [c] [15-C-5Na][OAc]·H2O (0.1 mmol) was used as catalyst.
95.0[f]
92.0[g]
15
16
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
20
84.7
To extend the scope of application of the CECILs, [18-C-
6K][OH] and [15-C-5Na][OH] were used as catalysts in the
Henry reaction of aldehydes and nitromethane (Table 4).
Both aliphatic and aromatic aldehydes, with either elec-
tron-withdrawing or electron-donating groups give good
yields. Generally, the aromatic aldehydes bearing electron-
withdrawing groups revealed higher reaction rates than
those with electron-donating groups (Table 4, entries 9–21
versus 1–8). The reactions of highly active aliphatic alde-
hydes and nitromethane were carried out at À158C and
gave good yields (Table 4, entries 24 and 25). The CECIL
catalyst was much more efficient for aliphatic aldehydes
compared with 1-ethyl-3-methylimidazolium chloride
([EMIM][Cl]),[8d] 1,1,3,3-tetramethyl guanidine lactate
17
18
19
20
20
20
96.0
71.0
10.3
20
21
30
30
trace
64.3
210
140
55.3
82.3[h]
81.3[c]
82.5[c]
22
23
([TMG]ACHTUNGTRNEUNG
[Lac])[8e] and 1-pentyl-3-methylimidazolium bro-
300
36.5
mide -Mg-Al hydrotalcites ([bmIm]BF4-Mg-Al HT) cata-
lysts.[8g] The scope of the reaction was extended to include
furfural and cinnamaldehyde (Table 4, entries 22, 23).
Chem. Eur. J. 2011, 17, 8731 – 8738
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8733

H. Jing et al.
Table 4. Henry reaction catalysed by [18-C-6K][OH].[a]
Table 5. Knoevenagel condensation catalysed by [18-C-6K][OH].[a]
Entry
R
t
Yield
[%][b]
AHCTUNGTERG[NNUN min]
Entry
R
t [min]
Yield [%][b]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15[c]
16[c]
17[c]
18[c]
19[d]
20
21
22
23
24[e]
25[e]
Ph
120
40
240
25
240
240
240
120
30
30
120
40
15
10
10
10
10
10
10
20
10
180
60
71.9
95.3
52.5
99.0
84.1
50.9
72.5
68.2
97.4
99.5
69.8
78.1
96.0
98.4
97.2
96.9
97.0
96.0
98.0
78.1
85.9
99.5
30.0
56.9
63.5
1
2
3
4
H
30
30
20
20
25
26
61.2
85.0
86.8
91.7
93.9
95.0[c]
2-CH3OC6H4
4-CH3OC6H4
2,5-(CH3O)2C6H3
2-CH3C6H4
3-CH3C6H4
4-CH3C6H4
3,4-(CH3)2C6H3
2-ClC6H4
3-ClC6H4
4-ClC6H4
2,4-ClC6H3
2-BrC6H4
2-NO2C6H4
2-NO2C6H4
2-NO2C6H4
2-NO2C6H4
2-NO2C6H4
2-NO2C6H4
3-NO2C6H4
4-NO2C6H4
2-furyl
2-Br
4-Cl
2,4-Cl
5
2-OCH3
[a] Reaction conditions: aromatic aldehyde (1 mmol), malononitrile
(1.3 mmol), catalyst [18-C-6K][OH] (30 mol%), CH3OH (1 mL), T=
258C. [b] Isolated yield. [c] [15-C-5Na][OH] (30 mol%) was used as cata-
lyst.
Scheme 2. Heck reaction in the presence of PdCl /
K2CO3.
2 ACHTUNGTERNNUG[18-C-6K]3ACHTUNGTRENNUNG[PO4]/
(E)-cinnamal
amyl
nonyl
170
170
used (Table 6<xtabr6, entries 11–14). When bromobenzene
was used as the substrate, the reaction required a higher
temperature (1408C) (Table 6<xtabr6, entries 15–18).
When chlorobenzene was used, the reaction cannot occur
under the same condition as bromobenzene because of the
relatively strong carbon–halogen bond. However, electron-
withdrawing groups can activate the carbon–halogen bond,
for example, 4-nitrochlorobenzene underwent reaction at
1408C (Table 6, entries 7–10) and 4-nitrobromobenzene re-
acted under the more mild conditions of 1108C (Table 6, en-
tries 1, 4–6). Otherwise, electron-donating group can deacti-
vate the carbon–halogen bond, for example, 4-bromome-
thoxybenzene underwent reaction at 1408C with lower
yields (Table 6, entries 19–22). In general, PdCl2/K2CO3/
CECIL in DMF can efficiently initiate the Heck coupling
reaction. The reaction of 1-bromo-4-nitrobenzene and sty-
rene can also be achieved without CECIL (Table 6, entry 2)
or in toluene (Table 6, entry 3), which suggests that both the
CECIL and DMF could act as ligands in the Heck reaction.
Considering the solvent effect of CECILs, we chose [18-C-
[a] Reaction conditions: aldehyde (4 mmol), nitromethane (10 mmol),
catalyst [18-C-6K][OH] (20 mol%), CH3OH (1 mL), RT. [b] Isolated
yield. [c] Recycled [18-C-6K][OH] used. [d] [15-C-5Na][OH]·H2O
(20 mol%) was used as catalyst. [e] T=À158C.
The reaction of 2-nitrobenzaldehyde and nitromethane
under optimised reaction conditions was chosen as model to
examine the recyclability of catalyst [18-C-6K][OH]. We
found that the catalyst can be reused at least five times with-
out significant loss of activity (Table 4, entries 14–18).
We have introduced the CECIL [18-C-6K][OH] with re-
markable effect on Michael additions and Henry reactions.
As a part of this program we now report the excellent cata-
lytic efficiency of [18-C-6K][OH] for Knoevenagel conden-
sation of aromatic aldehydes and malononitrile. The results
are shown in Table 5. Both the aromatic aldehydes with
electron-withdrawing (Table 5, entries 2–4) or electron-do-
nating groups (Table 5, entry 5) generated the respective
products in good yields; however, for unsubstituted benzal-
dehyde the reaction rate is comparatively slow (Table 5,
entry 1).
6K]ACTHUNRTGNEUNG[OAc] as both solvent and ligand in the Heck reaction
of bromobenzene and styrene. Excitingly, when the reaction
temperature was reduced from 140 to 1108C, the reaction
was complete within 70 min and gave 89.2% yield (Table 6,
entry 15). Finally, it is worth noting that this catalytic system
is totally insensitive to oxygen and moisture.
The oxidation of alcohols to their corresponding carbonyl
compounds is of significant importance in organic chemistry,
both for fundamental research and industrial manufactur-
ing.[14] It is known that bromates are commercially available,
inexpensive, stable solids and potential candidates for the
oxidation of organic compounds.[15] Accordingly, the CECIL
To further extend the scope of application of CECILs, the
CECILs of [18-C-6K]
6K][H2PO4] were applied in the Heck reaction as additives
(Table 6, entry 1). The best additive of [18-C-6K]3A[PO4] was
then chosen for further investigations in the Heck reaction
of olefins with aryl halides in the presence of PdCl2 and
K2CO3 in DMF (Scheme 2). From the results in Table 6, it
can be seen that the reaction can take place under mild con-
ditions (1108C) when the active aryl halide iodobenzene is
3ACHTUNGTREN[UNG PO4], [18-C-6K]2ACHTUNGTREN[NUGN HPO4] and [18-C-
ACHTUNGTRENNUNG
G
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Chem. Eur. J. 2011, 17, 8731 – 8738

Crown Ether Complex Cation Ionic Liquids
FULL PAPER
Table 6. Heck reaction of olefins and aromatic halides.[a]
[18-C-6K]
higher melting point of 1158C. A mixture of benzohydrol
and [18-C-6K][BrO3] was stirred at 1158C in a preheated oil
ACHTUNGRTENUN[NG BrO3] was synthesised as an oxidant, despite its
Entry
Aryl halide
Olefin
t
T
[8C]
Yield[b]
[%]
[min]
AHCTUNGTRENNUNG
95.0
bath and a conversion of 52.1% was achieved after 120 min
Scheme 3. When benzyl alcohol was used as the substrate a
70.0% yield of benzaldehyde was obtained after 100 min.
Most importantly, the oxidation reaction is carried out
1
120
110
90.0[c]
91.2[d]
2
3
150
150
36
110
110
110
110
110
140
140
140
140
73.5[e]
71.2[f]
80.3
97.1
96.7
43.0
27.0
30.5
–
under neutral conditions and [18-C-6K]
dant and solvent for this reaction.
ACHTUNGRTEN[NGNU BrO3] is both oxi-
4
5
60
Scheme 3. Oxidation of aromatic alcohols.
6
60
Conclusion
7
105
217
217
300
We have discovered a novel type of ionic liquid that consists
of a crown ether chelated alkali metal cation and various
anions, formed by a simple mixing of the correct molar ratio
of crown ether with the relevant salts in water, followed by
evaporation and vacuum drying to get the pure crown ether
complex cation ionic liquids (CECILs) without any byprod-
ucts. These CECILs have shown supreme abilities in organic
reactions, exemplified by application in Heck reactions, Mi-
chael additions, Henry reactions, Knoevenagel condensa-
tions and oxidation reactions. Their excellent catalytic activi-
ties might be attributed to enhancement of the basicity of
the CECIL anion, along with reduction of the electrostatic
interaction between the cation and anion. As with tradition-
al ILs, our new CECILs show a clear solvent effect in vari-
ous organic reactions. With this novel protocol in hand, fur-
ther discoveries on the applications of CECILs are under-
way in our laboratory.
8
9
10
11
12
13
14
15
16
17
18
300
60
110
110
110
110
70.7
98.7
78.2
84.0
12
81
300
70
140
110
68.0
89.2[g]
75
32
140
140
140
86.3
72.0
trace
Experimental Section
200
Materials and methods: All reagents were obtained from commercial
sources and used without further purification. 1H and 13C NMR spectra
were recorded on a Varian 300 spectrometer, with TMS as an internal
reference (CDCl3: dH =7.26 ppm, dC =77 ppm; D2O: dH =4.80 ppm).
Chemical shifts (d) are given in parts per million (ppm) and coupling
constants (J) are given in Hertz (Hz). Multiplicity is indicated by one or
more of the following: s (singlet); d (doublet); t (triplet); q (quartet); m
(multiplet); br (broad). Thermogravimetric differential thermal analysis
(TG-DTA) was carried out on a STA 449 C instrument (Netzsch, Germa-
ny). HRMS (ESI) was carried out on a Bruker APEX II mass spectrome-
ter with glycerol as the matrix. Elemental analyses were carried out on
Carioel elemental analyser.
19
20
21
22
115
120
96
140
140
140
140
84.0
21.0
59.1
trace
110
[a] Reaction conditions: Aryl halide (2 mmol), olefin (2.5 mmol), PdCl2
(2 mol%), additive [18-C-6K]3A[PO4]·0.5H2O (4 mol%), K2CO3 (3 mmol,
2 equiv), DMF (2 mL). [b] Isolated yield. [c] [18-C-6K]2A[HPO4]·0.5H2O
(4 mol%) was used as additive. [d] [18-C-6K][H2PO4]·2H2O (4 mol%)
was used as additive. [e] No CECIL. [f] Toluene (2 mL). [g] Bromo-
benzene (1 mmol), [18-C-6K][OAc] (1 g), neat.
General procedure for the synthesis of CECILs: The organic, inorganic
potassium or sodium salt (10 mmol) was mixed with [18]crown-6
(10 mmol, 2.6432 g) or [15]crown-5 (10 mmol, 2.2026 g) in water (15 mL).
After stirring at RT for 12 h, the excess water was evaporated under re-
duced pressure. The residue was vacuum dried to generate the desired
CECIL in 100% yield. To obtain the pure CECILs, the substrates must
be weighed accurately.
CTHUNGTRENNUNG
CTHUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Chem. Eur. J. 2011, 17, 8731 – 8738
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
8735

H. Jing et al.
A
E
tion of the reaction, monitored by TLC, the mixture was added to water
(15 mL) and extracted with diethyl ether (3ꢁ10 mL). The combined or-
ganic layers were dried over anhydrous Na2SO4 and evaporated. The
products were purified by flash column chromatography, if necessary.
3.63 ppm (s, 72H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.9 ppm;
elemental analysis calcd (%): C 47.04, H 8.00; found: C 47.15, H 8.19.
ACHTUNGTRENNUNG[18-C-6K]2ACHTUNGTRENNUNG
[HPO4]·1/2H2O: 1H NMR(300 MHz, D2O, 25 8C, TMS): d=
3.65 ppm (s, 48H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.7 ppm;
Catalyst recycling procedure: A mixture of chalcone (1 mmol), butane-
thiol (1.3 mmol) and [15-C-5Na][OH] (10 mol%) were stirred for 5 min
at 258C. After completion of the reaction, the mixture was added to
water (10 mL) and extracted with diethyl ether (3ꢁ10 mL). The com-
bined organic layers were concentrated under reduced pressure to give
the desired product. The aqueous phase was evaporated and dried under
vacuum to recover the catalyst.
elemental analysis calcd (%): C 46.81, H 8.02; found: C 46.86, H 7.95.
ACHTUNGTRENNUNG[18-C-6K]ACHTUNGTRENNUNG
[H2PO4]·2H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
3.62 ppm (s, 24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.9 ppm;
elemental analysis calcd (%): C 33.02, H 6.93; found: C 33.10, H 6.64.
ACHTUNGTRENNUNG[18-C-6K]ACHTUNGTRENNUNG
[OAc]·2.5H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
3.65 (s, 24H), 1.88 ppm (s, 3H); 13C NMR (75 MHz, D2O, 25 8C, TMS):
d=180.9, 68.9, 23.4 ppm; elemental analysis calcd (%): C 41.26, H 7.92;
found: C 41.48, H 7.64.
3-(Butylthio)-1, 3-diphenylpropan-1-one: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=7.91 (d, J
7.5 Hz, 1H), 7.43 (t, J(H,H)=9.0, 7.5 Hz, 4H), 7.30 (t, J
7.8 Hz, 2H), 7.18 (q, J(H,H)=7.2, 6.9, 7.5 Hz, 1H), 4.56 (t, J
7.2 Hz, 1H), 3.53 (d, J(H,H)=6.9 Hz, 2H), 2.25–2.42 (m, 2H), 1.43–1.62
ACHTUGTNREN(UNG H,H)=6.9 Hz, 2H), 7.54 (t, JCAHTUNGTRENNNUG
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG[15-C-5Na]ACHTUNGTRENNUNG
[OAc]·H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.72
A
ACHTUNGTRENNUNG
(s, 20H), 1.93 ppm (s, 3H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=
AHCTUNGTRENNUNG
180.9, 69.7, 23.4 ppm; elemental analysis calcd (%): C 45.00, H 7.87;
found: C 44.81, H 7.48.
(m, 2H), 1.24–1.37 (m, 2H), 0.83 ppm (t, JACTHNUTRGNEUNG(H,H)=6.9, 7.8 Hz, 3H);
13C NMR (75 MHz, CDCl3, 258C, TMS): d=196.9, 142.2, 136.7, 133.2,
A
128.6, 128.5, 128.1, 127.8, 127.1, 45.4, 44.2, 31.2, 31.1, 21.9, 13.6 ppm.
Ethyl 3-(piperidin-1-yl)propanoate: 1H NMR (300 MHz, CDCl3, 258C,
24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.7 ppm; elemental
analysis calcd (%): C 39.44, H 6.62, N 3.83; found: C 39.05, H 6.54, N
3.66.
TMS): d=4.10 (q, J
8.1 Hz, 2H), 2.46 (t, J
4H), 1.40 (m, 2H) 1.23 ppm (t, JAHCNUTGTRENNUNG
G
ACHTUNGTRENUN(NG H,H)=5.7,
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG[18-C-6K]2ACHTUNGTRENNUNG
[CO3]: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.66 ppm
(s, 48H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=168.1, 69.6 ppm; ele-
(75 MHz, CDCl3, 258C, TMS): d=172.7, 60.3, 54.2, 54.2, 32.2, 25.9, 24.2,
14.2 ppm.
2-(3-Oxo-1,3-diphenyl-propyl)malononitrile: 1H NMR (300 MHz, CDCl3,
mental analysis calcd (%): C 47.50, H 7.79; found: C 47.69, H 7.89.
ACHTUNGTRENNUNG[18-C-6K]ACHTUNGTRENNUNG
[HCO3]·1/2H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
3.65 ppm (s, 24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=161.2,
69.9 ppm; elemental analysis calcd (%): C 41.81, H 7.02; found: C 41.78,
H 6.91.
258C, TMS): d=7.96 (d, J
ACHUTGTNRENNUG(H,H)=7.2 Hz, 2H), 7.62 (t, JACHTUNGTNER(NUGN H,H)=7.5,
7.8 Hz, 1H), 7.49 (t, J(H,H)=7.8, 6.9 Hz, 2H), 7.43 (m, 5H), 4.63 (d, J-
AHCTUNGTRENNUNG
AHCTUNGTREG(NNNU H,H)=5.1 Hz, 1H), 3.93–3.99 (m, 1H), 3.63–3.69 ppm (m, 2H);
ACHTUNGTRENNUNG
[18-C-6K][OH]: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.62 ppm (s,
13C NMR (75 MHz, CDCl3, 258C, TMS): d=196.6, 136.4, 135.6, 134.1,
24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.6 ppm; elemental
129.2, 129.1, 128.8, 128.0, 127.9, 111.9, 111.7, 41.0, 39.9, 28.7 ppm.
analysis calcd (%): C 44.98, H 7.86; found: C 44.81, H 7.77.
General procedure for the Henry reaction: A mixture of aromatic alde-
hyde (4 mmol), nitromethane (10 mmol), [18-C-6K][OH] (20 mol%) and
CH3OH (1 mL) were stirred for 1–6 h at RT. After completion of the re-
action, monitored by TLC, the mixture was added to water (10 mL) and
extracted with diethyl ether (3ꢁ10 mL). The combined organic layers
were dried over anhydrous Na2SO4, filtered and concentrated under
vacuum to give the desired product, which was then purified by flash
column chromatography (petroleum ether/ethyl acetate).
ACHTUNGTRENNUNG
[15-C-5Na][OH]·H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
3.66 ppm (s, 20H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.8 ppm;
elemental analysis calcd (%): C 43.16, H 8.33; found: C 43.04, H 8.35.
ACHTUNGTRENNUNG
[15-C-5Na][Br]: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.65 ppm (s,
20H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.7 ppm; elemental
analysis calcd (%): C 37.17, H 6.24; found: C 37.27, H 6.29.
1
G
(s, 24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.6 ppm; elemental
Catalyst recycling procedure: After completion of the reaction between
2-nitrobenzaldehyde (4 mmol) and nitromethane (10 mmol) catalysed by
[18-C-6K][OH] (20 mol%) at RT, the mixture was added to water
(10 mL) and extracted with diethyl ether (3ꢁ10 mL). The combined or-
ganic layers were collected and concentrated to give the target product.
The aqueous phase was evaporated and then the residue was dried under
vacuum to recover [18-C-6K][OH] for the next cycle.
analysis calcd (%): C 35.91, H 6.53; found: C 35.58, H 6.25.
ACHTUNGTRENNUNG[15-C-5Na]2ACHTUNGTRENNUNG
[C2O4]·2H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
3.72 ppm (s, 40H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=173.1,
69.9 ppm; elemental analysis calcd (%): C 43.28, H 7.26; found: C 43.03,
H 7.15.
ACHTUNGTRENNUNG[18-C-6K]ACHTUNGTRENNUNG
[BrO3]: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.65 ppm
2-Nitro-1-phenylethanol: 1H NMR (300 MHz, CDCl3, 258C, TMS): d=
(s, 24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.6 ppm; elemental
7.38 (m, 5H), 5.44 (dd, JACTHNUTRGNE(NUG H,H)=9.3, 3.3 Hz, 1H), 4.47–4.64 (m, 2H),
analysis calcd (%): C 33.42, H 5.61; found: C 33.48, H 5.33.
2.93 ppm (br, 1H); 13C NMR (75 MHz, CDCl3, 258C, TMS): d=138.1,
ACHTUNGTRENNUNG[15-C-5Na]ACHTUNGTRENNUNG
[IO3]·1/2H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=
129.0, 128.9, 125.9, 81.2, 70.9 ppm.
(E)-1-Nitro-4-phenylbut-3-en-2-ol: 1H NMR (300 MHz, CDCl3, 258C,
3.68 (s, 20H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.7 ppm; ele-
mental analysis calcd (%): C 28.12, H 4.96; found: C 28.15, H 4.99.
TMS): d=7.24–7.39 (m, 5H), 6.75 (dd, J
(dd, J(H,H)=15.9, 6.3 Hz, 1H), 5.01 (m, 1H), 4.6 (d, J
2H,), 2.91 ppm (d, J
(H,H)=4.2 Hz, 1H); 13C NMR (75 MHz, CDCl3,
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG[18-C-6K]ACHTUNGTRENNUNG
[ClO3]: 1H NMR (300 MHz, D2O, 25 8C, TMS): d=3.64 ppm (s,
A
ACHTUNGTRENNUNG
24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=69.8 ppm; elemental
AHCTUNGTRENNUNG
analysis calcd (%): C 37.26, H 6.25; found: C 36.97, H 6.05.
[18-C-6K][biphthalate]·1.5H2O: 1H NMR (300 MHz, D2O, 25 8C, TMS):
ACHTUNGTRENNUNG
258C, TMS): d=135.4, 133.5, 128.7, 128.4, 126.6, 124.9, 79.8, 69.5 ppm.
1-(Furan-2-yl)-2-nitroethanol: 1H NMR (300 MHz, CDCl3, 258C, TMS):
d=7.73 (q, JACHTUNGTRENNUNG(H,H)=6.0, 3.6 Hz, 2H), 7.54 (q, JCAHTUNGTRENN(UGN H,H)=6.0, 3.6 Hz, 2H),
d=7.40 (d, JACTHNUTRGENN(GU H,H)=6.9 Hz, 1H), 6.38 (m, 2H), 5.45 ppm (dd, JACHTUNGTRENNUNG(H,H)=
3.60 ppm (s, 24H); 13C NMR (75 MHz, D2O, 25 8C, TMS): d=174.0,
133.9, 131.0, 129.2, 69.8 ppm; elemental analysis calcd (%): C 48.47, H
6.51; found: C 48.28, H 6.18.
9.0, 3.6 Hz, 1H), 4.68–4.81 (m, 2H), 3.29 ppm (br, 1H); 13C NMR
(75 MHz, CDCl3, 258C, TMS): d=150.8, 143.1, 110.6, 108.1, 78.4,
64.7 ppm.
ACHTUNGTRENNUNG
General procedure for the Knoevenagel condensation: A mixture of al-
dehyde (1 mmol), malononitrile (1.3 mmol), [18-C-6K][OH] (30 mol%)
and CH3OH (1 mL) were stirred at 258C until the reaction was complete
(TLC). The mixture was extracted with ethyl acetate (3ꢁ10 mL). The
combined organic layers were dried over Na2SO4 and concentrated under
vacuum. The product was purified by flash column chromatography (pe-
troleum ether/ethyl acetate).
ACHTUNGTRENNUNG
243.1200.
General procedure for the Michael addition:
(2 mmol), nucleophile (2.6 mmol) and [15-C-5Na][OH] or [18-C-6K]-
ACHTUNGTRENNUNG[OAc] (10 mol%) was stirred at 258C in CH3OH (1 mL). After comple-
A mixture of olefin
8736
www.chemeurj.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 8731 – 8738

Crown Ether Complex Cation Ionic Liquids
FULL PAPER
2-Benzylidenemalononitrile: 1H NMR (300 MHz, CDCl3, 258C, TMS):
Acknowledgements
d=7.91 (d, J
N
ACHTUNGTRENUN(NG H,H)=7.8,
6.9 Hz, 1H), 7.55 ppm (t, JAHCTNUGTRENNNUG
CDCl3, 258C, TMS): d=159.9, 134.6, 130.9, 130.7, 129.6, 113.7, 112.5,
83.1 ppm.
We are grateful for the financial support of the National Natural Science
Foundation of China (NSFC 20973086).
2-(4-Chlorobenzylidene)-malononitrile: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=7.85 (d, J
ACHTUNGTRENN(UNG H,H)=7.2 Hz, 2H), 7.74 (s, 1H), 7.52 ppm
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168–171.
(dd, J
ACHTUNGTRENNUNG
d=158.2, 141.1, 131.8, 130.0, 129.3, 113.4, 112.3, 84.0 ppm.
2-(2-Bromobenzylidene)malononitrile: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=8.22 (s, 1H), 8.12 (dd, J
ACHTUNGTNER(NUNG H,H)=6.9, 2.7 Hz, 1H), 7.74
(dd,
JACHTUNGTRENNUNG
(H,H)=7.5, 2.1 Hz, 1H), 7.42–7.53 ppm (m, 2H); 13C NMR
(75 MHz, CDCl3, 258C, TMS): d=158.7, 134.9, 134.0, 130.7, 129.8, 128.3,
126.4, 113.1, 111.7, 86.0 ppm.
2-(2-Methoxybenzylidene)malononitrile: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=8.30 (s, 1H), 8.18 (dd, J
(H,H)=8.1, 7.5 Hz, 1H), 7.08 (t, J(H,H)=7.5 Hz, 1H), 6.99 (d, J-
ACHTUNGTRENNUNG
(H,H)=8.4 Hz, 1H), 3.93 ppm (s, 3H); 13C NMR (75 MHz, CDCl3, 258C,
ACHTUNGTNER(NUNG H,H)=7.8, 1.2 Hz, 1H), 7.58 (t,
J
A
ACHTUNGTRENNUNG
TMS): d=158.9, 154.4, 136.5, 128.8, 121.1, 120.1, 114.3, 112.9, 111.5, 81.3,
55.9 ppm.
2-(2,4-Dichlorobenzylidene)malononitrile: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=8.18 (s, 1H), 8.14 (d, J
ACHTUNGTNER(NUNG H,H)=8.7 Hz, 1H), 7.57 (d, J-
N
JACHTUNGTRENNUNG
(H,H)=5.7 Hz, 1H); 13C NMR
(75 MHz, CDCl3, 258C, TMS): d=154.5, 141.0, 137.1, 130.7, 130.1, 128.3,
127.4, 113.0, 111.7, 86.0 ppm.
General procedure for the Heck Reaction: [18-C-6K]3ACTHNUTRGNEG[NU PO4]·0.5H2O
(0.08 g, 4 mol%), K2CO3 (0.414 g, 3 mmol) and PdCl2 (0.0035 g, 2 mol%)
was added sequentially to a mixture of aryl halide (2 mmol) and olefin
(2.5 mmol) in DMF (2 mL). The mixture was stirred and heated at 110 or
1408C (see Table 6<xtabr6). After completion of the reaction, moni-
tored by TLC, the mixture was added to water (15 mL) and extracted
with diethyl ether (3ꢁ10 mL). The combined organic layers were dried
over anhydrous Na2SO4, filtered and concentrated under vacuum to give
the desired product, which was then purified by flash column chromatog-
raphy (petroleum ether/ethyl acetate).
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Cruciani, P. Ioan, D. Spinelli, R. Spisani, J. Med. Chem. 2005, 48,
2445–2456.
(E)-1-Phenyl-2-(4-nitrophenyl)-ethylene: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=8.22 (d, JACTHNGUTREN(NNUG H,H)=9.0 Hz, 2H), 7.63 (d, JACHTGNUTRENNUNG
2H), 7.55 (d, JACHTUNGTRENNUNG(H,H)=7.5 Hz, 2H), 7.36 (m, 4H), 7.14 ppm (d, JACHTNUGTRENNUNG
16.5 Hz, 1H); 13C NMR (75 MHz, CDCl3, 258C, TMS): d=146.7, 143.8,
136.1, 133.2, 128.9, 128.8, 127.0, 126.8, 126.2, 124.1 ppm.
(E)-1, 2-Diphenyl-ethylene: 1H NMR (300 MHz, CDCl3, 258C, TMS):
d=7.50 (d, J
ACHTUNGTRENNUNG(H,H)=7.8 Hz, 2H), 7.34 (t, JACHTUNGTNER(NUGN H,H)=6.6, 7.5 Hz, 2H), 7.24
(t, J
ACHTUNGTRENNUNG
CDCl3, 258C, TMS): d=137.2, 128.6, 128.6, 127.6, 126.5 ppm.
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346, 1533–1552; b) R. B. Bedford, C. S. J. Cazin, D. Holder, Coord.
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(E)-Methyl cinnamate: H NMR (300 MHz, CDCl3, 258C, TMS): d=7.71
(d, J
JACHTUNGTRENNUNG
ACHTUNGTRENNUNG(H,H)=16.2 Hz, 2H), 7.50–7.53 (m, 2H), 7.36–7.38 (m, 3H), 6.44 (d,
(H,H)=15.9 Hz, 1H), 3.79 ppm (s, 3H); 13C NMR (75 MHz, CDCl3,
258C, TMS): d=167.3, 144.8, 134.2, 130.2, 128.8, 128.0, 117.7, 51.6 ppm.
(E)-Methyl 3-(4-nitrophenyl)-2-propenoate: 1H NMR (300 MHz, CDCl3,
258C, TMS): d=8.25 (d, JACTHUNTGRNENUG(H,H)=8.7 Hz, 2H), 7.70 (d, JACHTUTGNREN(NUGN H,H)=17.7 Hz,
1H), 7.67 (d, JACHTUNGTRENNUNG(H,H)=7.8 Hz, 2H), 6.57 ppm (d, JACHTUNGTRNE(NUGN H,H)=15.9 Hz, 1H),
3.84 ppm (s, 3H); 13C NMR (75 MHz, CDCl3, 258C, TMS): d=166.5,
148.5, 141.9, 140.4, 128.6, 124.2, 122.0, 52.1 ppm.
General procedure for the oxidation reaction: An oven-dried round-
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acetate (3ꢁ10 mL). The combined organic layers were dried over anhy-
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Received: January 12, 2011
Published online: June 15, 2011
8738
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Chem. Eur. J. 2011, 17, 8731 – 8738