Three-component coupling reactions in ionic liquids: A facile synthesis of α-aminonitriles

Article abstract of DOI:10.1039/b208844b

Aryl imines, derived in situ from aldehydes and amines, smoothly undergo addition with trimethylsilyl cyanide in 1-butyl-3-methyl-imidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquids under mild and neutral reaction conditions to afford the corresponding α-aminonitriles in excellent yields. The ionic liquids can be recycled in five to six runs without any apparent loss of activity.

Full text of DOI:10.1039/b208844b

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Three-component coupling reactions in ionic liquids: a facile synthesis
of a-aminonitriles
Jhillu S. Yadav,* Basi. V. S. Reddy, B. Eshwaraiah, Mende. Srinivas and P. Vishnumurthy
Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500 007,
India. E-mail: yadav@iict.ap.nic.in; Fax: 91-40-7160512
L e t t e r
Received (in Montpellier, France) 9th September 2002, Accepted 10th December 2002
First published as an Advance Article on the web 14th January 2003
Aryl imines, derived in situ from aldehydes and amines, smoothly
undergo addition with trimethylsilyl cyanide in 1-butyl-3-methyl-
imidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium
hexafluorophosphate ionic liquids under mild and neutral reac-
tion conditions to afford the corresponding a-aminonitriles in
excellent yields. The ionic liquids can be recycled in five to six
runs without any apparent loss of activity.
of ionic liquids as promoters for the synthesis of a-amino-
nitriles in a one-pot procedure.
Results and discussion
In view of the emerging importance of ionic liquids as novel
reaction media, herein, we wish to report the use of ionic
liquids as efficient promoters for the three-component coupling
reactions of aldehydes, amines and trimethylsilyl cyanide to
produce a-aminonitriles (Scheme 1).
The treatment of benzaldehyde and aniline with TMSCN in
-butyl-3-methylimidazolium tetrafluoroborate [bmim]BF
4
Introduction
1
a-Aminonitriles are very useful precursors for the synthesis of
ionic medium afforded the corresponding 2-anilino-2-phenyl-
acetonitrile in 90% yield. Similarly, a variety of aldehydes were
coupled with a range of amines and trimethylsilyl cyanide in a
one-pot operation by using this procedure to produce a-ami-
nonitriles in 85–93% yields. These three-component coupling
reactions proceeded efficiently at ambient temperature with
high selectivity. In all cases, no cyanohydrin trimethylsilyl
ethers (an adduct between an aldehyde and trimethylsilyl cya-
nide) are obtained under these reaction conditions. This is due
to the rapid formation and activation of the imines by ionic
liquids. The reactions are clean and highly selective affording
exclusively a-aminonitriles in high yields in a short time. This
method is equally effective with aldehydes bearing electron-
withdrawing substituents in the aromatic ring. Furthermore,
acid sensitive aldehydes such as furfuraldehyde and cinnamal-
dehyde worked well without any decomposition or polymer-
ization under these reaction conditions. This method does not
require any acidic promoters or activators to promote the reac-
tion. The reaction conditions are neither acidic nor basic and
are mild enough to perform these reactions in the presence
of either acid or base sensitive substrates. Enolizable aldehydes
such as 2-phenylacetaldehyde and decanal also produced the
corresponding a-aminonitriles in high yields. In this reaction,
the activity of the ionic liquid was strongly influenced by the
nature of the anion. The reactions of various aldehydes and
amines with trimethylsilyl cyanide were carried out in hydro-
philic [bmim]BF and hydrophobic [bmim]PF ionic liquids.
1
2
a-amino acids, and many nitrogen containing heterocycles
such as imidazoles and thiadiazoles, etc. The Strecker reaction
is one of the most efficient and straightforward synthetic meth-
3
ods for the synthesis of a-aminonitriles. The classical Strecker
reaction is generally carried out with alkaline cyanides in aqu-
eous solution. Subsequently, several modifications of the
Strecker reaction have been reported using a variety of cyanat-
ing agents such as a-trimethylsiloxynitriles, diethyl phosphor-
4
ocyanidate under various reaction conditions. Trimethylsilyl
cyanide is a safe and more effective cyanide anion source for
the nucleophilic addition reactions of imines under mild condi-
tions. Recently, one-pot procedures have also been developed
5
for the synthesis of a-aminonitriles from carbonyl compounds,
amines and trimethylsilyl cyanide or tributyltin cyanide using
6
lanthanide triflates as novel catalysts. However, many of
these methods involve the use of strongly acidic conditions
and extended reaction times and also require tedious aqueous
work-up leading to the generation of a large amount of
toxic waste. Thus, there is still scope to develop a simple
and practical method for the cyanation of imines under mild
conditions.
One of the prime principles of green chemistry is to develop
an alternative reaction medium, which is the basis for the
development of many cleaner chemical technologies. In parti-
cular, ionic liquids have recently gained recognition as possible
environmentally safe and alternative solvents to conventional
organic solvents. Ionic liquids, especially those based on the
4
6
Among these ionic liquids, [bmim]BF was found to be super-
4
ior in terms of conversion and selectivity. The advantage of the
1
-N-alkyl-3-methylimidazolium cation, have shown great pro-
7
mise as novel reaction media for various catalytic processes.
Due to the great potential of room temperature ionic liquids
as environmentally benign media for catalytic processes, much
attention has been currently focused on organic reactions pro-
use of ionic liquids as promoters for this transformation is that
these ionic liquids are easily recovered and recycled in subse-
quent runs. Since the products were weakly soluble in the ionic
8
moted by ionic liquids. The unique property of ionic liquids is
that they have essentially no vapor pressure, which makes
them optimal replacements for volatile organic solvents tradi-
tionally used as industrial solvents. Because of distinct advan-
tages of ionic liquids, they can make a great contribution to
green chemistry. However, there are no examples on the use
Scheme 1
4
62
New J. Chem., 2003, 27, 462–465
DOI: 10.1039/b208844b
This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2003

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Table 1 Room temperature ionic liquids promoted synthesis of a-amino nitriles
[
bmim]BF
4
[bmim]PF
6
b
b
Entry
Aldehyde
Amine
Time/h
Yield (%)
Time/h
Yield (%)
a)
b)
c)
d)
e)
C
6
H
5
CHO
4-MeOC
3-PhOC
4-ClC
CHO
C
6
C
6
C
6
C
6
C
6
H
5
H
5
H
5
H
5
H
4
NH
NH
NH
NH
2
2
2
2
5.0
5.0
5.0
5.5
4.5
(92)
(90)
(92)
(89)
(91)
6.0
6.5
7.5
8.0
7.5
(87)
(85)
(87)
(83)
(85)
6
H
4
CHO
CHO
CHO
6
H
4
6
H
4
C
6
H
5
2 2
CH NH
f)
6
2-EtOC H
4
CHO
6.0
(93)
8.5
(82)
g)
h)
i)
C
6
H
5
CHO
4-NO
4-FC
2-MeC
NH
2-ClC
3-MeOC
6
H
4
NH
2
5.0
9.5
6.0
6.5
(91)
(85)
(88)
(85)
7.0
9.0
7.0
8.0
(85)
(75)
(82)
(80)
2
C
6
H
4
CHO
CHO
CHO
C
6
H
5
2
6
H
4
6
H
4
NH
2 2
CH NH
2
j)
C
6
H
5
6
H
3
k)
C
6
H
5
CH
2
NH
2
4.5
(90)
6.0
(83)
l)
5.5
6.0
5.0
(92)
(88)
(87)
(89)
6.5
8.0
7.5
9.5
(85)
(79)
(82)
(77)
m)
n)
C
6
C
6
C
6
H
5
H
5
H
5
NH
NH
NH
2
2
2
o)
6.5
a
1
b
All products were characterized by H NMR, IR and mass spectroscopy. Isolated and unoptimized yields after purification.
phase, they were easily separated by simple extraction with
ether. The rest of the ionic liquid was thoroughly washed with
ether and dried at 80 C under reduced pressure and reused
combined with ease of recovery and reuse of this novel reaction
medium is expected to contribute to the development of clean
and environmentally friendly processes for the synthesis of a-
aminonitriles of synthetic importance. The use of ionic liquids
as promoters for this transformation avoids the use of moisture
sensitive reagents and heavy metal Lewis acids.
ꢀ
four to six times without any loss of activity. The products
were of the same purity as in the first run and no decrease in
yields was observed in runs carried out using recovered ionic
liquid. 1-Butyl-3-methylimidazolium methylsulfate [bmim]-
SO CH was also equally as effective as [bmim]BF ionic liquid
4
3
4
for this conversion. In further reactions, the efficiency of
various quaternary ammonium salts was tested. These three-
component coupling reactions were not successful in other
molten salts such as n-tetrabutylammonium chloride (n-Bu4-
NCl) or 1-n-butyl-3-methylimidazolium chloride [bmim]Cl.
This clearly indicates that both cation and anion play an
important role as the solvent as well as promoter for this trans-
formation. Furthermore, we have performed the reactions in
Experimental
[Bmim]BF , [bmim]SO CH and [bmim]PF6 ionic liquids
4
4
3
were prepared according to the procedures reported in the
9
literature.
Melting points were recorded on Buchi R-535 apparatus and
are uncorrected. IR spectra were recorded on a Perkin-Elmer
FT-IR 240-c spectrophotometer using KBr optics. H-NMR
1
organic solvents such as CH
3
CN and CHCl
3
to compare the
spectra were recorded on Gemini-200 spectrometer in CDCl3
using TMS as internal standard. Mass spectra were recorded on
a Finnigan MAT 1020 mass spectrometer operating at 70 eV.
CHN analyses were recorded on a Vario EL analyzer.
efficiency of ionic liquids. In these solvents, the reactions took
longer (8–22 h) and also the products were obtained in low
to moderate yields (35–57%). In contrast to organic solvents,
enhanced reaction rates, improved yields and high selectivity
are the features obtained in ionic liquids. For example, the
treatment of benzaldehyde and aniline with trimethylsilyl
General procedure
4
cyanide in [bmim]BF ionic liquid for 5.0 h afforded the corre-
A mixture of aldehyde (1 mmol), amine (1 mmol), and tri-
methylsilyl cyanide (1.2 mmol) in 1-butyl-3-methylimidazo-
lium tetrafluoroborate or 1-butyl-3-methylimidazolium
methylsulfate or 1-butyl-3-methylimidazolium hexafluorophos-
phate (1 mL) was stirred at ambient temperature for an
appropriate time (Table 1). After completion of the reaction,
as indicated by TLC, the reaction mixture was washed with
diethyl ether (3 ꢁ 10 mL). The combined ether extracts were
concentrated in vacuo and the resulting product was directly
charged on small silica gel column and eluted with a mixture
of ethyl acetate:n-hexane (1:9) to afford pure a-aminonitrile.
The rest of the viscous ionic liquid was further washed with
sponding a-aminonitrile in 92% yield. This is due to the rapid
formation and activation of imines in ionic media. However,
the same reaction in refluxing chloroform after 8.0 h gave
the desired product in 57% yield along with cyanohydrin tri-
methylsilyl ether (an adduct between aldehyde and TMSCN).
These results clearly show the efficiency of ionic liquids for
this conversion. The scope and generality of this process is illu-
strated with respect to various aldehydes and amines and the
results are presented in Table 1.
ꢀ
ether and dried at 80 C under reduced pressure to retain its
activity in subsequent runs. Spectral data for selected products:
Conclusion
ꢀ
In summary, we have demonstrated a simple, convenient and
practical method for the synthesis of a-aminonitriles through
a one-pot three-component coupling of aldehydes, amines and
trimethylsilyl cyanide using ionic liquids as novel promoters.
The simple experimental and product isolation procedures
3a: Solid, m.p. 73–74 C, IR (KBr): n 3369, 3021, 2954, 2236,
1603, 1505, 1464, 1313, 1142, 995, 751. H NMR (CDCl3):
1
d 4.05 (d, 1H, J ¼ 8.1 Hz), 5.40 (d, 1H, J ¼ 8.1 Hz), 6.75 (d,
2H, J ¼ 8.0 Hz), 6.90 (t, 1H, J ¼ 7.8 Hz), 7.25 (t, 2H,
1
3
J ¼ 7.8 Hz), 7.40–7.50 (m, 3H), 7.60–7.70 (m, 2H).
New J. Chem., 2003, 27, 462–465
C
463

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NMR (proton decoupled, CDCl
3
): d 50.7, 114.8, 118.9, 120.6,
3j: Liquid, IR (KBr): n 3400, 2941, 2890, 2241, 1616, 1527,
+
27.8, 129.7, 130.0, 130.2, 134.5, 145.4. EIMS: m/z: 208 M ,
1
1
1
8
1471, 1283, 1160, 1045, 789. H NMR (CDCl ): d 1.85 (brs,
3
80, 116, 91, 77, 51. Anal. Calcd. for C14 (208.26): C,
H
12
N
2
NH), 3.80 (s, 3H), 3.95 (AB q, 2H, J ¼ 13.0 Hz), 4.70 (d,
0.74; H, 5.81; N, 13.45. Found: C, 80.73; H, 5.84; N, 13.47%.
ꢀ
1H, J ¼ 8.0 Hz), 6.80–6.95 (m, 3H), 7.25 (t, 1H, J ¼ 7.9
+
Hz), 7.30–7.55 (m, 4H). EIMS:m/z: 252 M , 225, 122, 91,
3
b: Solid, m.p. 94–95 C, IR (KBr): n 3383, 3053, 2932, 2245,
601, 1502, 1454, 1298, 1118, 1041, 925, 764. H NMR
1
1
16 2
77, 51. Anal. Calcd. for C16H N O (252.31): C, 76.17; H,
(
1
CDCl
H, J ¼ 8.1 Hz), 6.75 (d, 2H, J ¼ 8.0 Hz), 6.80 (t, 1H,
3
): d 3.80 (s, 3H), 3.90 (d, 1H, J ¼ 8.1 Hz), 5.30 (d,
6.39; N, 11.10. Found: C, 76.19; H, 6.41; N, 11.13%.
3k: Viscous liquid, IR (KBr): n 3398, 2927, 2860, 2230, 1609,
1
1530, 1495, 1275, 1159, 1054, 787. H NMR (CDCl
J ¼ 7.9 Hz), 6.90 (d, 2H, J ¼ 8.0 Hz), 7.25 (t, 2H, J ¼ 7.9
3
): d 1.45
+
Hz), 7.50 (d, 2H, J ¼ 8.0 Hz). EIMS: m/z: 238 M , 211,
(d, 3H, J ¼ 6.9 Hz), 3.10–3.20 (m, 1H), 3.58–3.60 (m, 1H),
1
(
5
14 2
81, 167, 141, 104, 77, 51, 40. Anal. Calcd. for C15H N O
3.80 (d, 1H, J ¼ 13.0 Hz), 4.05 (d, 1H, J ¼ 13.0 Hz), 7.20–
+
7.45 (m, 10H). EIMS: m/z: 250 M , 223, 145, 105, 91, 77,
238.28): C, 75.61; H, 5.92; N, 11.76. Found: C, 75.63; H,
.95; N, 11.79%.
18 2
51. Anal. Calcd. for C17H N (250.34): C, 81.56; H, 7.25;
ꢀ
3
c: Solid, m.p. 64–65 C, IR (KBr): n 3424, 2924, 2854, 2231,
N, 11.19. Found: C, 81.59; H, 7.27; N, 11.21%.
3l: Liquid, IR (KBr): n 3406, 2921, 2854, 2220, 1695, 1573,
1
1
4
603, 1514, 1460, 1270, 1153, 1034, 798. H NMR (CDCl ): d
3
1
1460, 1217, 1148, 1012, 938, 759. H NMR (CDCl
.02 (d, 1H, J ¼ 8.0 Hz), 5.38 (d, 1H, J ¼ 8.0 Hz), 6.78 (d, 2H,
3
): d 2.10
(brs, NH), 3.90 (s, 2H), 4.75 (s, 1H), 6.20–6.35 (m, 4H),
J ¼ 7.9 Hz), 6.90 (t, 1H, J ¼ 7.8 Hz), 7.05–7.65 (m, 11H).
+
EIMS: m/z: 300 M , 273, 210, 181, 167, 141, 104, 77, 51. Anal.
+
7.35–7.40 (m, 2H). EIMS: m/z: 202 M , 150, 125, 111, 95,
Calcd. for C H N O (300.34): C, 79.98; H, 5.37; N, 9.33.
2
81, 69, 57, 43. Anal. Calcd. for C H N O (202.21): C,
11 10
0
16
2
2
2
Found: C, 80.01; H, 5.39; N, 9.35%.
ꢀ
65.34; H, 4.98; N, 13.85. Found: C, 65.36; H, 4.98; N, 13.86%.
ꢀ
3
600, 1515, 1457, 1272, 1161, 1098, 791. H NMR (CDCl
d: Solid, m.p. 109–112 C, IR (KBr): n 3405, 2927, 2239,
3m: Solid, m.p. 99–100 C, IR (KBr): n 3400, 2967, 2895,
2235, 1601, 1535, 1482, 1280, 1180, 1055, 791. H NMR
1
1
1
3
):
d 4.05 (d, 1H, J ¼ 8.1 Hz), 5.39 (d, 1H, J ¼ 8.1 Hz), 6.75 (d,
(CDCl ): d 1.60 (d, 3H, J ¼ 6.9 Hz), 3.20–3.37 (m, 1H),
3
2
H, J ¼ 8.0 Hz), 6.90 (t, 1H, J ¼ 7.9 Hz), 7.15 (t, 2H,
3.45–3.55 (m, 1H), 4.30–4.45 (m, 1H)), 6.65 (d, 2H, J ¼ 8.0
J ¼ 7.9 Hz), 7.40 (d, 2H, J ¼ 8.0 Hz), 7.60 (d, 2H, J ¼ 8.0
Hz), 6.85 (t, 1H, J ¼ 7.9 Hz), 7.20–7.45 (m, 7H). EIMS: m/z:
+
Hz). EIMS: m/z: 242 M , 213, 149, 114, 91, 73, 59. Anal.
+
236 M , 209, 131, 105, 77, 51. Anal. Calcd. for C16
H
16
N
2
Calcd. for C H ClN (242.70): C, 69.28; H, 4.57; Cl, 14.61;
2
(236.31): C, 81.32; H, 6.82; N, 11.85. Found: C, 81.33; H,
6.85; N, 11.87%.
1
4
11
N, 11.54. Found: C, 69.30; H, 4.59; Cl, 14.60; N, 11.55%.
e: Colorless oil, IR (KBr): n 3409, 2924, 2234, 1648, 1514,
ꢀ
3
401, 1108, 1028, 919, 825, 751. H NMR (CDCl
3n: Solid, m.p. 117–119 C, IR (KBr): n 3350, 2929, 2233,
1
1
1603, 1505, 1461, 1275, 1030, 976, 897, 746. H NMR (CDCl
1
3
): d 1.80
3
):
(
(
6
brs, NH), 3.95 (AB q, 2H, J ¼ 13.5 Hz), 4.70 (s, 1H), 6.78
d 3.80 (d, 1H, J ¼ 8.1 Hz), 5.05 (m, 1H), 6.30 (dd, 1H, J ¼ 6.9,
17.3 Hz), 6.78 (d, 1H, J ¼ 8.0 Hz), 6.90 (t, 1H, J ¼ 7.9 Hz),
7.08 (dd, 1H, J ¼ 1.7, 17.3 Hz), 7.25–7.45 (m, 8H). EIMS:
d, 1H, J ¼ 8.0 Hz), 7.15 (t, 1H, J ¼ 7.8 Hz), 7.25–7.40 (m,
1
3
H), 7.49–7.51 (m, 2H). C NMR (proton decoupled, CDCl ):
3
+
d 51.7, 53.8, 119.2, 128.1, 128.9, 129.1, 129.5, 130.0, 135.2,
1
m/z: 234 M , 206, 128, 115, 77, 51. Anal. Calcd. for
+
38.5. EIMS: m/z: 222 M , 195, 141, 131, 116, 106, 91, 77,
C H N (234.30): C, 82.02; H, 6.02; N, 11.96. Found: C,
14
1
6
2
5
1. Anal. Calcd. for C15 (222.28): C, 81.05; H, 6.35;
H
14
N
2
82.01; H, 6.04; N, 11.98%.
3o: Liquid, IR (KBr): n 3405, 2925, 2854, 2235, 1600, 1505,
N, 12.60. Found: C, 81.07; H, 6.37; N, 12.61%.
f: Liquid, IR (KBr): n 34481, 2981, 2895, 2225, 1638, 1598,
1
1463, 1279, 1160, 1030, 791. H NMR (CDCl
3
494, 1248, 1118, 1043, 923, 754. H NMR (CDCl
3
): d 0.90 (t, 3H,
1
1
3
): d 1.37 (t,
J ¼ 6.8 Hz), 1.20–1.40 (m, 12H), 1.50–1.65 (m, 2H), 1.80–1.90
(m, 2H), 3.80 (brs, NH), 4.05–4.15 (m, 1H), 6.60 (d, 2H,
J ¼ 8.0 Hz), 6.80 (t, 1H, J ¼ 7.9 Hz), 7.20 (t, 2H, J ¼ 7.9
3
H, J ¼ 6.9 Hz), 3.90 (AB q, 2H, J ¼ 13.5 Hz), 4.15 (q, 2H,
J ¼ 6.9 Hz), 4.80 (s, 1H), 6.30 (m, 1H), 6.87 (d, 1H, J ¼ 8.0
+
Hz), 7.0 (t, 1H, J ¼ 7.8 Hz), 7.30–7.45 (m, 4H). EIMS: m/z:
Hz). EIMS: m/z: 258 M , 185, 155, 135, 121, 77,51. Anal.
+
56 M , 227, 198, 173, 146, 120, 104, 95, 80, 52. Anal. Calcd.
2
26 2
Calcd. for C17H N (258.40): C, 79.02; H, 10.14; N, 10.84.
for C15
H
16
N
2
O
C, 70.31; H, 6.30; N, 10.95%.
2
(256.30): C, 70.29; H, 6.29; N, 10.93. Found:
Found: C, 79.04; H, 10.17; N, 10.86%.
ꢀ
3
g: Solid, m.p. 72–73 C, IR (KBr): n 3365, 2935, 2857, 2237,
1
1
3
6
1
3
605, 1517, 1461, 1275, 1035, 791. H NMR (CDCl ): d 2.20 (s,
Acknowledgements
H), 3.38 (brd, 1H, NH, J ¼ 8.1 Hz), 5.45 (d, J ¼ 8.1 Hz),
.80 (t, 2H, J ¼ 7.9 Hz), 7.10 (d, 1H, J ¼ 8.0 Hz), 7.20 (d,
H, J ¼ 7.9 Hz), 7.40–7.50 (m, 3H), 7.50 (d, 2H, J ¼ 8.0
BVSR thanks CSIR, New Delhi, for the award of fellowships.
1
3
Hz). C NMR (proton decoupled, CDCl ): d 17.8, 50.7,
3
1
1
9
12.2, 118.9, 120.4, 124.1, 127.7, 127.9, 129.8, 130.0, 131.3,
34.7, 143.4. EIMS: m/z: 222 M , 194, 155, 141, 116, 106,
+
References
1, 73, 65, 45. Anal. Calcd. for C H N (222.28): C, 81.05;
1
5
14
2
1
2
Y. M. Shafran, V. A. Bakulev and V. S. Mokrushin, Russ. Chem.
Rev., 1989, 58, 148.
(a) L. M. Weinstock, P. Davis, B. Handelsman and R. Tull, J. Org.
Chem., 1967, 32, 2823; (b) W. L. Matier, D. A. Owens, W. T.
Comer, D. Deitchman, H. C. Ferguson, R. J. Seidehamel and
J. R. Young, J. Med. Chem., 1973, 16, 901.
H, 6.35; N, 12.60. Found: C, 81.03; H, 6. 36; N, 12.63%.
h: Viscous liquid, IR (KBr): n 3421, 2920, 2859, 2235, 1600,
3
1
1
3
515, 1458, 1271, 1157, 1039, 791. H NMR (CDCl ): d 4.05
(
d, 1H, J ¼ 8.0 Hz), 5.35 (d, 1H, J ¼ 8.0 Hz), 6.80 (d, 2H,
J ¼ 8.0 Hz), 6.90 (t, 1H, J ¼ 7.9 Hz), 7.20 (t, 2H, J ¼ 7.9
Hz), 7.67 (d, 2H, J ¼ 8.1 Hz), 8.10 (d, 2H, J ¼ 8.1 Hz). EIMS:
3
4
A. Strecker, Ann. Chem. Pharm., 1850, 75, 27.
(a) K. Mai and G. Patil, Tetrahedron Lett., 1984, 25, 4583; (b) S.
Harusawa, Y. Hamada and T. Shioiri, Tetrahedron Lett., 1979,
+
m/z: 253 M , 227, 152, 181, 167, 136, 123, 91,77, 51. Anal.
Calcd. for C H N O (253.25): C, 66.40; H, 4.38; N, 16.59.
2
1
4
11
3
2
0, 4663.
Found: C, 66.42; H, 4.39; N, 16.61%.
ꢀ
5
(a) T. K. Chakraborty, G. V. Reddy and K. A. Hussain, Tetra-
hedron Lett., 1991, 32, 7597; (b) J. P. Leblanc and H. W. Gibson,
Tetrahedron Lett., 1992, 33, 6295; (c) A. Heydari, P. Fatemi and
A. A. Alizadeh, Tetrahedron Lett., 1998, 39, 3049.
(a) S. Kobayashi, H. Ishitani and M. Ueno, Synlett, 1997, 115;
(b) S. Kobayashi, T. Busujima and S. Nagayama, Chem. Commun.,
3
i: Solid, m.p. 95–97 C, IR (KBr): n 3410, 2931, 2230, 1610,
1
1
3
520, 1461, 1269, 1051, 790. H NMR (CDCl ): d 4.65 (d, 1H,
J ¼ 8.1 Hz), 5.45 (d, 1H, J ¼ 8.1 Hz), 6.90–6.95 (m, 2H), 7.15–
+
.35 (m, 4H), 7.58–7.65 (m, 2H). EIMS: m/z: 260 M , 234,
6
7
7
1
6
35, 100, 75. Anal. Calcd. for C H ClFN (260.69): C,
1
4
10
2
1
998, 981.
4.50; H, 3.87; Cl, 13.60; F, 7.29; N, 10.75. Found: C, 64.51;
Recent reviews on ionic liquids: (a) T. Welton, Chem. Rev., 1999,
99, 2071; (b) P. Wasserscheid and W. Keim, Angew. Chem., Int.
H, 3.89; Cl, 13.62; F, 7.31; N, 10.73%.
4
64
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View Article Online
Ed., 2000, 39, 3772; (c) Catalytic reactions in ionic liquids: R.
Sheldon, Chem. Commun., 2001, 2399.
(a) Brønsted acidic ionic liquids as dual solvent and catalysts:
A. C. Cole, J. L. Jensen, I. Ntai, K. L. T. Tran, K. J. Weaver,
D. C. Forbes and J. H. Davis, Jr., J. Am. Chem. Soc., 2002, 124,
9
Preparation of ionic liquids: (a) S. Park and R. J. Kazlauskas,
J. Org. Chem., 2001, 66, 8395; (b) P. Bonhote, A. P. Dias, N.
Papageorgiou, K. Kalyanasundaram and M. Gratzel, Inorg.
Chem., 1996, 35, 1168.
8
5962; (b) J. Peng and Y. Deng, Tetrahedron Lett., 2001, 42, 5917.
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