Synthesis of ethyl α-cyanocinnamates catalyzed by Al2O3-OK solid base

Article abstract of DOI:10.1081/SCC-120016322

Condensation of ethyl cyanoacetate with aromatic aldehydes catalyzed by Al₂O₃-OK solid base in ethanol results ethyl α-cyanocinnamates in 80-99% yields.

Full text of DOI:10.1081/SCC-120016322

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Synthesis of Ethyl α-Cyanocinnamates Catalyzed by
Al O –OK Solid Base
Tong-Shou Jin , Jun-Jie Guo , Hui-Min Liu & Tong-Shuang Li
2
3
a
a
a
a
a
Department of Chemistry, College of Chemistry and Environmental Science, Hebei
University, Baoding, P.R. China
Published online: 17 Aug 2006.
To cite this article: Tong-Shou Jin , Jun-Jie Guo , Hui-Min Liu & Tong-Shuang Li (2003) Synthesis of Ethyl α-Cyanocinnamates
Catalyzed by Al O –OK Solid Base, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
2
3
Organic Chemistry, 33:5, 783-788, DOI: 10.1081/SCC-120016322
To link to this article: http://dx.doi.org/10.1081/SCC-120016322
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Õ
SYNTHETIC COMMUNICATIONS
Vol. 33, No. 5, pp. 783–788, 2003
Synthesis of Ethyl a-Cyanocinnamates Catalyzed
by Al O –OK Solid Base
2
3
Tong-Shou Jin,* Jun-Jie Guo,Hui-Min Liu,
and Tong-Shuang Li
Department of Chemistry, College of Chemistry and
Environmental Science, Hebei University,
Baoding, P.R. China
ABSTRACT
Condensation of ethyl cyanoacetate with aromatic aldehydes
catalyzed by Al O –OK solid base in ethanol results ethyl a-cyano-
cinnamates in 80–99% yields.
2
3
Ethyl a-cyanocinnamates are a class of important organic com-
pounds. For instance, ethyl a-cyano-m-nitrocinnamate is used as the
photosensitive composition and intermediate of plant growth regula-
[
1]
[2]
tor, ethyl a-cyanocinnamate with a alkoxy or hydroxy group in the
*
Correspondence: Tong-Shou Jin, Department of Chemistry, College of
Chemistry and Environmental Science, Hebei University, Baoding 071002,
P.R. China; E-mail: orgsyn@mail.hbu.edu.cn.
7
83
DOI: 10.1081/SCC-120016322
Copyright & 2003 by Marcel Dekker, Inc.
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com

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7
84
Jin et al.
benzene ring is used as part of ultraviolet filter composition for protecting
[
light-sensitive foods, wood-product, paper, dyes, fibers, plastics, etc.
3]
The usual catalyst for the preparation of ethyl a-cyanocinnamates are
ammonia and ammonium salts, primary and secondary amines and their
[
4]
[4,5]
[6]
salts.
Al O –AlPO , CdI2, ZnCl2, ZnO, and MgO have been reported.
Subsequently the use of pyridine.
[9]
TiCl4 and base,
[7]
[8]
[10]
2
3
4
However, each of the methods has its merit and some shortcomings.
Some of these methods are not entirely satisfactory due to drawbacks
such as long reaction time, low yields of the product, tedious workup,
harshness of the reaction conditions (Sch. 1).
[
11]
Al O –OK, a new type of solid base has been studied recently. It
2
3
has been widely used in the fields of alkylation, condensation and iso-
[
11]
merization under mild conditions.
Herein we demonstrated a facile
method for preparation of ethyl a-cyanocinnamates catalyzed by
Al O –OK solid base (Table 1).
FromTable 1 we found that electron donating groups such as –OH,
OCH , –OCH O–, –CH , and –N(CH ) in the aromatic ring can
2
3
–
3 2 3 3 2
undergo the desired transformation without much difficulty. (Entries 6,
, 8, 10 and 11). Electron withdrowing groups such as –Cl, –NO in the
7
2
aromatic ring increased the activity of aldehydes, so the condensation
reaction can be carried out in relatively shorter time. For instance, pre-
paration of the phenyl derivates (Entry 1) was reported 62–86% yield in
[
7]
[9]
the presence of Al O –AlPO or ZnCl2 in 1–2 h. However, it obtained
2
3
4
98% yield catalyzed by Al O –OK solid base for 30 min in our experi-
2 3
ment. In the spectrum analysis of compound 3f, a weak NOE relationship
was observed between the benzylic methyl (ꢀ 2.50) and the vinyl (ꢀ 8.61)
protons, but no NOE was seen between ethyl and the aromatic protons.
These data suggest a configuration where the aryl and the cyano groups
are in the cis relationship.
In summary, we have shown that Al O –OK solid base is the
2
3
efficient catalyst for the condensation of aromatic aldehydes and ethyl
cyanoacetate in the refluxing temperature of ethanol, because of its
operational simplicity, short reaction time and high yields.
Al O -OK
ethanol/reflux
80-99 %
2
3
ArCHO + NCCH CO Et
ArCH C(CN)CO Et
2
2
2
1
2
3
Scheme 1.

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Ethyl a-Cyanocinnamates
785
Table 1. Synthesis of ethyl a-cyanocinnamates catalyzed by Al O –OK solid
2
3
base.
ꢀ
M.p. ( C)
a
Reaction
time (min)
Yields
(%)
Entry
Aldehydes
Found Reported
[
12]
1
2
3
30
30
35
98
99
95
48–50
49–51
[
[
12]
171–172
133–135
172–173
134–136
13]
[
8]
4
5
40
35
98
97
89–91
90
[
14]
101–103
101–102
6
30
96
52–54
7
8
9
50
55
45
95
97
97
169–170
79–81
[
[
15]
12]
106–108
106–108
111–112
1
0
100
95
110–111
11
12
13
14
35
35
40
25
98
96
80
90
94–95
124–125
115–116
90–91
[
12]
124–126
[
116
8]
[
16]
91–92
a
Yields refer to isolated products.
EXPERIMENTAL
The catalyst was prepared as follows: 26 g KNO and 74 g Al O
3
3
2
were crushed in a mortar, then added appropriate deionized water
which can be absorbed by Al O . After ground, the mixture was dried
2
3
ꢀ
ꢀ
at 110 C for 1 h, and then activated at 600 C for 3 h. When the loading of
KNO is above the threshold, only about 7% of KNO can be dispersed
through the interaction with Al O support and decomposed in a mild
3
3
2
3
pretreatment such as evacuation at room temperature, while a lot of
undispersed KNO located in the pores of Al O forms a new phase
such as K [Al(NO )] . Both the residual KNO and K [Al(NO )] decom-
3
2
3
2
3
5
3
2
3 5

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Jin et al.
ꢀ
pose during evacuation at 600 C, and potassiumions migrate fromthe
inner to the external surface of Al O during the evacuation process.
Consequently, several layers of basic materials such as K O overlap on
2
3
2
the Al O result in some superbasic sites with a basic strength (H-) of 27.0.
2
3
The catalyst could be reused by dealt out simply.
Liquid aldehyde was purified by distillation prior to use. Melting
point was uncorrected. Infrared spectra was recorded on a Bio-Rad
FTS-40 spectrometer (KBr). Proton NMR spectra was determined in
D-chloroformsolution on a FT-NMR Bruker 300 (300 MHz), and
reported in ꢀ ppmusing tetramethylsilane as the standard. Mass spectra
was measured on a VG-7070E spectrometer (EI, 70 eV).
General Procedure for the Condensation of Ethyl
Cyanoacetate and Aldehydes
A mixture of aldehyde 1 (10 mmol), ethyl cyanoacetate 2 (1.36 g
2 mmol), 10 mL absolute ethanol (dried with Mg), Al O –OK solid
1
2 3
base (150 mg), was added to a 50 mL flask. It was stirred with a magnetic
stirrer and refluxed for appropriate time as indicated in Table 1. The
reaction was monitored by TLC. The crude product was washed with
5% aqueous alcohol, which give a good purity. The catalyst could be
reused five times for the synthesis of compound 3d without significant
decrease in reactivity.
Spectral data of some compounds are as follows.
3
f: IR (neat) 3100–2850, 2210, 1710, 1650, 1600, 1450, 1260, 1200,
ꢁ1 1
1
100 cm ; H NMR (CDCl ) ꢀ 8.61 (1H, s, CH¼), 8.17 (1H, d, Ph-H,
3
J ¼ 7.7), 7.47–7.29 (3H, m, Ph-H), 4.40 (2H, q, J ¼ 7.1, OCH CH ), 2.5
2 3
(
(
3H, s, CH -Ph), 1.41 (3H, t, J ¼ 7.1, OCH CH ); EIMS m/z 215
3
2
3
þ
M , 100), 200 (28), 187 (42), 170 (78), 142 (32), 115 (63), 89 (20), 65 (25).
g: IR (KBr) 3450–3180, 3070–2900, 2230, 1710, 1590, 1510, 1440,
3
ꢁ
370, 1260, 1200, 1185, 1100 cm ; H NMR (CDCl ) ꢀ 10.50 (1H, s,
3
1 1
1
OH), 8.19 (1H, s, CH¼), 7.92 (2H, d, J ¼ 8.13, Ph-H), 6.99 (2H, d,
J ¼ 8.13, Ph-H), 4.39 (2H, q, J ¼ 7.31, OCH CH ), 1.40 (3H, t,
2
3
þ
J ¼ 7.31, OCH CH ); EIMS m/z 217 (M , 100), 189 (50), 172 (98), 144
2
3
(
45), 117 (25), 89 (45), 63 (8).
h: IR (neat) 3100–2800, 2210, 1705, 1600, 1505, 1260, 1170 cm
H NMR (CDCl ) ꢀ 8.21 (1H, s, CH¼), 7.95 (2H, d, J ¼ 8.4, Ph-H),
ꢁ1
3
;
1
3
6
.96 (2H, d, J ¼ 8.4, Ph-H), 4.40 (2H, q, J ¼ 7.4, OCH CH ), 3.91 (3H,
þ
3 2 3
2
3
s, OCH ), 1.40 (3H, t, J ¼ 7.4, OCH CH ); EIMS m/z 231 (M , 45), 200
(
3), 170 (89), 143 (90), 115 (100), 89 (10), 70 (7), 65 (9).

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Ethyl a-Cyanocinnamates
787
3
k: IR (neat) 3100–2850, 2220, 1710, 1600, 1460, 1370, 1270, 1200,
ꢁ1 1
1
100 cm ; H NMR (CDCl ) ꢀ 8.21 (1H, s, CH¼), 7.91 (2H, d, J ¼ 8.14,
3
Ph-H), 7.31 (2H, d, J ¼ 8.14, Ph-H), 4.38 (2H, q, J ¼ 7.06, OCH CH ),
2 3
2
(
.43 (3H, s, CH -Ar), 1.40 (3H, t, J ¼ 7.06, OCH CH ); EIMS m/z 215
3
2
3
þ
M , 100), 200 (28), 187 (42), 170 (78), 142 (32), 115 (63), 89 (20), 65 (25).
ACKNOWLEDGMENTS
The project was supported by National Natural Science Foundation
of China (29872011 and 29572039), Educational Ministry of China,
Educational Department of Hebei Province (990104), and Science and
Technology Commission of Hebei Province.
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Received in Japan November 20, 2001