Catalyzed preparation of ylidenemalononitriles and 3-cyanocoemarin in water

Article abstract of DOI:10.1081/SCC-200043214

As sodium hydroxide is used as catalyst, Knoevenagel condensation of malononitrile with aromatic aldehydes can take place at room temperature in water. 3-Cyanocoumarin was obtained by one-pot synthesis.

Full text of DOI:10.1081/SCC-200043214

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Catalyzed Preparation of
Ylidenemalononitriles and
3‐Cyanocoumarin in Water
Ming Zhang a & Ai‐Qin Zhang b
a Chemistry College , Jiangxi Normal University ,
Nanchang, Jiangxi, 330027, P. R. China
b Department of Environmental and Chemical
Engineering , Nanchang Institute of Aeronautical
Technology , Nanchang, Jiangxi, P. R. China
Published online: 10 Jan 2011.
To cite this article: Ming Zhang & Ai‐Qin Zhang (2004) Catalyzed Preparation of
Ylidenemalononitriles and 3‐Cyanocoumarin in Water, Synthetic Communications:
An International Journal for Rapid Communication of Synthetic Organic Chemistry,
34:24, 4531-4535, DOI: 10.1081/SCC-200043214
To link to this article: http://dx.doi.org/10.1081/SCC-200043214
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 24, pp. 4531–4535, 2004
Catalyzed Preparation of
Ylidenemalononitriles and
3-Cyanocoumarin in Water
2
Ming Zhang1, and Ai-Qin Zhang
*
1Chemistry College, Jiangxi Normal University,
Nanchang, Jiangxi, P. R. China
2Department of Environmental and Chemical Engineering,
Nanchang Institute of Aeronautical Technology,
Nanchang, Jiangxi, P. R. China
ABSTRACT
As sodium hydroxide is used as catalyst, Knoevenagel condensation of
malononitrile with aromatic aldehydes can take place at room tempera-
ture in water. 3-Cyanocoumarin was obtained by one-pot synthesis.
Key Words: Water phase; Catalyze; Knoevenagel condensation.
*
Correspondence: Ming Zhang, Chemistry College, Jiangxi Normal University,
Nanchang, Jiangxi 330027, P. R. China; E-mail: zmchem@sina.com.cn.
4531
DOI: 10.1081/SCC-200043214
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

4532
Zhang and Zhang
INTRODUCTION
Knoevenagel condensation is an important method for formation of
alkenes from carbonyl compounds. Malononitrile is a typical compound
with active methylene, often used to undergo Knoevenagel reaction with alde-
hydes. These reactions are usually carried out in organic solvents by treating
with basic catalysts, such as ammonium salt, primary and secondary amine,[1]
or solid basic catalyst.[2] Later, Lewis acid ZnCl2 was reported effective for
this kind of reaction.[3] In recent years, with application of microwave tech-
niques, Knoevenagel reactions can be carried out under catalysis of piper-
idine,[4] LiCl,[5] silica gel,[6] P2O5-piperidine,[7] ammonium acetate,[8]
ammonium acetate-basic alumina,[9] NaCl or NH4OAc/HOAc,[10] and urotro-
pine.[11] Over the last decade, water has drawn considerable attention as a
solvent in organic reactions, due to its cost-effective and nontoxic qualities.
It is generally considered that the 1,2-elimination of b-hydroxyl intermediate
is inhibited by protic solvent and the retro-Knoevenagel reaction can take
place in aqueous solution.[12] But it was reported that Knoevenagel reactions
can occur in water in the presence of CTMAB. This prompted us to reseach
this reaction in water further. We found that knoevenagel reaction of malono-
nitrile with aldehydes can be carried out in water at room terperature under
catalysis of basic reagent (NaOH, Et3N, CH3NH2) (Sch. 1).
RESULTS AND DISCUSSION
Condensation of malononitrile with benzaldehyde in water without cata-
lyst requires 16 hr. Basic catalysts can speed up the reaction greatly requiring
only 0.5 hour (Table 1).
We further investigated condensation of malononitrile with other aro-
matic aldehydes with choice of catalyst NaOH. Reactions of liquid aldehydes
(1a, 2a, 3a, 4a) require 0.5 h, but solid aldehydes (5a, 6a) need much longer
time, perhaps because the spreading speed of liquid is faster than that of solid.
Reaction rate of p-hydroxybenzaldehyde with malononitrile is related closely
to the amount of sodium hydroxide used. The rate is 20 hours when the molar
ratio of sodium hydroxide to malononitrile is 0.1, but can be shortened to 0.5 h
Scheme 1.

Preparation of Ylidenemalononitriles and 3-Cyanocoumarin in Water
4533
Table 1. Catalyst effect on the reaction.
Amount of catalyst
(mmol)
Time
(h)
Yield
(%)
Entry
Catalyst
1
2
3
4
—
0
1
1
1
16
91
91
91
90
NaOH
Et3N
CH3NH2
0.5
0.5
0.5
Note: Used amounts of malononitrile and benzaldehyde are both 10 mmol.
by increasing the molar ratio to 1.1, because solid-liquid, two-phase reactions
become liquid homogeneous reactions with increasing the amount of sodium
hydroxide (Table 2).
Condensation of o-hydroxybenzaldehyde with malononitrile in water
produce two substances: ylidenemalononitrile (8c) and sodium salt of 3-
cyanocoumarin (8d). (8c) is susceptible to heat and decomposes, and is not
convenient for isolation. After condensation, concentrated hydrochloric acid
Table 2. Condensation of malononitrile with aromatic aldehydes.
NaOH
(mmol)
Time
(h)
Yield
(%)
Entry
Ar
1
2
3
4
5
6
7
C6H52
o-Cl C6H42
1
1
0.5
0.5
0.5
0.5
21
91
92
92
91
95
91
91
p-CH3O C6H42
Furyl 2
p-(CH3)2N C6H42
p-HO C6H42
p-HO C6H42
1
1
1
1
11
20
0.5
Note: Used amounts of malononitrile and aldehyde are both 10 mmol.

4534
Zhang and Zhang
Scheme 2.
was added to the reaction mixture, then (8c) and (8d) were all converted to
3-cyanocoumarin (Sch. 2).
So 3-cyanocoumarin can be prepared by one-pot synthesis.
EXPERIMENTAL SECTION
Condensation of malononitrile with aldehydes: 25 mL distilled water,
10 mmol malononitrile, and specified amount of catalyst were stirred to be a
clear solution, then 10 mmol aromatic aldehyde was added and stirred at
room temperature for a specified period of time. The product (1c, 2c, 3c,
4c, 5c) was isolated by filtration. The product (6c, 7c) was isolated by filtration
after acidification of the reaction mixtures.
Synthesis of 3-cyanocoumarin: 25 mL distilled water, 10 mmol malono-
nitrile, 1 mmol NaOH, was stirred to be a clear solution, then 10 mmol
o-hydroxybenzaldehyde was added. After stirring at room temperature for
18 hours, 12.5 mL concentrated hydrochloric acid was added, then heated at
608C for 0.5 h. After cooling, 3-cyanocoumarin was obtained by filtration.
All the products gave m.p.s. and spectral data consistent with the reported
ones.[13–15]
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Preparation of Ylidenemalononitriles and 3-Cyanocoumarin in Water
4535
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Received in Japan May 10, 2004