908
N.H. Khan et al. / Catalysis Communications 11 (2010) 907–912
Calc. for C14H15NO3 C 68.56, H 6.16, N 5.71 found C 68.63, H 6.21, N
5.68 ppm.
2.2.8. 2-Ethoxycarbonyl-2-hydroxy-3,3-dimethylbutanenitrile (2k)
1H NMR δ=1.12 (s, 9H), 1.35 (t, J=7, 3H), 4.25–4.31 (m, 2H),
4.92 (s, 1H) ppm. 13C NMR δ=14.12, 25.10, 34.89, 65.37, 73.19,
115.96, 153.93 ppm. Anal. Calc. for C9H15NO3 C 58.36, H 8.16, N 7.56
found C 58.40, H 8.23, N 7.49.
2.2.9. 2-Ethoxycarbonyl-2-hydroxy-4-methylpentanenitrile (2l)
1H NMR δ=0.99 (d, J=5.5, 6H), 1.34 (t, J=7, 3H), 1.80–1.91 (m,
3H), 4.25–4.30 (m, 2H), 5.23 (t, J=7.5, 1H) ppm. 13C NMR δ=14.11,
22.03, 22.15, 24.36, 40.85, 63.47, 65.37, 116.76, 153.62 ppm. Anal. Calc.
for C9H15NO3 C 58.36, H 8.16, N 7.56 found C 58.31, H 8.18, N 7.52.
Fig. 1. Structure of various ionic liquids.
ethylcyanoformate (1.2 mmol, 0.098 ml) was added through a
syringe over a period of 5 min and the resulting reaction mass was
further stirred for 2 h. The progress of the reaction was monitored
by TLC. After the completion of the reaction, the product was
extracted with n-hexane (3×2 ml) and purified by column chro-
matography (hexane:ethylacetate 90:10). The recovered ionic
liquid was kept under vacuum for 8 h to remove volatiles and
stored in a desiccator for its reuse in subsequent catalytic runs.
Characterization data of some of the representative compounds
are discussed below.
3. Result and discussion
A series of ionic liquids (IL 1–9) (Fig. 1) based on N-methyl N′-
alkyl imidazole having different alkyl chain lengths and counter ions
was explored for their usefulness in cyanoethoxycarbonylation of
benzaldehyde as a model substrate at room temperature and the
results are presented in Table 1. Ionic liquids viz., 1-ethyl-3-methyl
imidazolium bromide (IL 1), 1-dodecyl-3-methyl imidazolium bro-
mide (IL 5) and 1-butyl-3-methyl imidazolium chloride (IL 6) were
solid at room temperature; hence dry dichloromethane was used as
co-solvent for carrying out cyanoethoxycarbonylation of benzalde-
hyde. These ILs in combination with dichloromethane gave 2-
ethoxycarbonyl-2-hydroxy-2-phenyl-acetonitrile in excellent yields
(80–98%) in 4–12 h (entries 1, 5 and 6). Room temperature ILs viz., IL
2 and IL 3 bearing C4 and C5 alkyl chain length with Br− as counter
ion (entries 2, 3) do not require the use of co-solvent to give the
desired product in excellent yield (∼98%) in 4 and 2 h respectively.
Liquid IL with C7 alkyl chain (IL 4) though gave high product yield
(86%) but took 12 h reaction time (entry 4). These results led us to
explore the role of counter anion with the ILs having alkyl chain C4
and C5 where desired products were obtained in excellent yields.
Besides, the results achieved with Cl− as counter ion (entries 6 and 7)
were as good as with Br− ion. Ironically, when PF−6 was used as
counter ion there was no product formation even after 24 h (entries 8,
9). Surprisingly in the absence of any of the above ILs (entry 11) or in
the presence of CH2Cl2 (a commonly preferred solvent for this system,
entry 12) there was no product formation in cyanoethoxycarbonylation
2.2.1. 2-Ethoxycarbonyl-2-hydroxy-2-phenyl-acetonitrile (2a)
Colorless liquid. 1H NMR δ=1.32 (t, J=7.5, 3H), 4.25–4.30 (m, 2H),
6.26 (s, 1H), 7.43–7.54 (m, 5H) ppm. 13C NMR 14.21, 65.73, 66.48,
115.93, 127.99, 129.38, 130.74, 131.37, 153.53 ppm.
2.2.2. 2-Ethoxycarbonyl-2-hydroxy-2-(2-methylphenyl)-acetonitrile
(2b)
1H NMR δ=1.33 (t, J=7.5, 3H), 2.44 (s, 3H), 4.25–4.31 (m, 2H),
6.38 (s, 1H), 7.23–7.37 (m, 3H), 7.55 (d, J=8, 1H) ppm. 13C NMR
δ=14.27, 19.06, 64.72, 65.75, 115.83, 126.93, 128.75, 129.55, 130.83,
131.48, 136.90, 153.61 ppm.
2.2.3. 2-Ethoxycarbonyl- 2-hydroxy-2-(4-methylphenyl)-acetonitrile
(2c)
1H NMR δ=1.33 (t, J=7, 3H), 2.38 (s, 3H), 4.28 (q, J=7, 2H), 6.22
(s, 1H), 7.24–7.26 (m, 2H), 7.42–7.43 (m, 2H) ppm. 13C NMR δ=14.32,
21.53, 66.48, 65.73, 116.10, 128.12, 130.10, 141.14, 153.65 ppm.
2.2.4. 2-Ethoxycarbonyl-2-hydroxy-2-(3-methylphenyl)-acetonitrile
(2d)
Table 1
1H NMR δ=1.33 (t, J=7, 3H), 2.38 (s, 3H), 4.24–4.30 (m, 2H), 6.22
(s, 1H), 7.26–7.34 (m, 4H) ppm. 13C NMR δ=14.24, 21.24, 65.70, 66.53,
116.02, 125.09, 128.57, 129.26, 131.26, 131.51, 139.40, 153.57 ppm.
Effect of carbon chain and counter ion on cyanoethoxycarbonylation of benzaldehyde.a
2.2.5. 2-Ethoxycarbonyl-2-hydroxy-2-(2-methoxylphenyl)-acetonitrile
(2e)
Entry
Ionic liquid
Time (h)
Conversion (%)b
1H NMR δ=1.32 (t, J=7, 3H), 3.86 (s, 3H), 4.26–4.29 (m, 2H), 6.58
(s, 1H), 6.94(d, J=8, 1H), 7.00–7.03 (m, 1H), 7.40–7.4(m, 1H), 7.55
(dd, J=2, 6, 1H) ppm. 13C NMR δ=14.28, 55.90, 61.85, 65.57, 111.25,
116.10, 119.60, 121.09, 128.09, 132.21, 153.66, 156.89 ppm.
1c
2
3
IL 1; [C2mim]+ Br−
IL 2; [C4mim]+ Br−
IL 3; [C5mim]+ Br
IL 4; [C7mim]+ Br−
IL 5; [C12mim]+ Br−
IL 6; [C4mim]+ Cl−
IL 7; [C5mim]+ Cl−
IL 8; [C4mim]+ PF−6
IL 9; [C5mim]+ PF−6
IL 3; [C5mim]+ Br−
–
4
4
2
93
98
N98
86
80
4
12
12
4
2.5
24
24
30
48
48
5c
6c
7
98
97
2.2.6. 2-Ethoxycarbonyl-2-hydroxy-2-(4-bromophenyl)-acetonitrile
(2h)
8
9
NR
NR
98
NR
NR
1H NMR δ=1.31 (t, J=7, 3H), 4.22–4.30 (m, 2H), 6.20 (s, 1H), 7.40
(d, J=8.5, 2H), 7.57 (d, J=8.5, 2H) ppm. 13C NMR δ=14.24, 65.78,
65.92, 115.52, 125.21, 129.60, 130.40, 132.63, 153.3 8 ppm.
10d
11
12e
–
a
0.5g ionic liquid (IL 1–9), benzaldehyde 63 μl, ethylcyanoformate 98 μl.
Conversion determined by GC Analysis SHIMADZU GC-14B, CHORMATO-PAK (2 m,
2.2.7. 2-Ethoxycarbonyl-2-hydroxy-3-methyl-4-phenyl-but-3-enonitrile
(2j)
b
4 mm) column.
1H NMR δ=1.37 (t, J=7, 3H), 2.06 (s, 3H), 4.31 (q, J=5, 2H), 5.79
(s, 1H), 6.85 (s, 1H), 7.29–7.39 (m, 5H) ppm. 13C NMR δ=13.68, 65.10,
69.73, 114.84, 127.53, 127.94, 128.56, 133.02, 134.72, 153.02 ppm. Anal.
c
Using 0.5 ml CH2Cl2.
10 mol% ionic liquid with respect to the benzaldehyde.
Reaction carried out in CH2Cl2 as a solvent (1 ml).
d
e