Tetra-n-butylammonium hydroxide (TBAH)-catalyzed Knoevenagel condensation: A facile synthesis of α-cyanoacrylates, α-cyanoacrylonitriles, and α-cyanoacrylamides

Article abstract of DOI:10.1080/00397910500385258

Tetra-n-butylammonium hydroxide (TBAH) has been utilized as a novel and efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene compounds such as methyl- and ethylcyanoacetate, malononitrile, and cyanoacetamide to afford sub

Full text of DOI:10.1080/00397910500385258

This article was downloaded by: [North Carolina State University]
On: 17 July 2013, At: 23:17
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office:
Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International
Journal for Rapid Communication of
Synthetic Organic Chemistry
Publication details, including instructions for authors and subscription
information:
http://www.tandfonline.com/loi/lsyc20
Tetra‐n‐butylammonium Hydroxide
(TBAH)–Catalyzed Knoevenagel
Condensation: A Facile Synthesis of
α‐Cyanoacrylates, α‐Cyanoacrylonitriles, and
α‐Cyanoacrylamides
a
a
Saeed Balalaie & Morteza Bararjanian
a
Chemistry Department, K. N. Toosi University of Technology, Tehran, Iran
Published online: 19 Aug 2006.
To cite this article: Saeed Balalaie & Morteza Bararjanian (2006) Tetra‐n‐butylammonium Hydroxide
(TBAH)–Catalyzed Knoevenagel Condensation: A Facile Synthesis of α‐Cyanoacrylates, α‐Cyanoacrylonitriles,
and α‐Cyanoacrylamides, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 36:4, 533-539, DOI: 10.1080/00397910500385258
To link to this article: http://dx.doi.org/10.1080/00397910500385258
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”)
contained in the publications on our platform. However, Taylor & Francis, our agents, and our
licensors make no representations or warranties whatsoever as to the accuracy, completeness, or
suitability for any purpose of the Content. Any opinions and views expressed in this publication
are the opinions and views of the authors, and are not the views of or endorsed by Taylor &
Francis. The accuracy of the Content should not be relied upon and should be independently
verified with primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities
whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial
or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or
distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use
can be found at http://www.tandfonline.com/page/terms-and-conditions

w
Synthetic Communications , 36: 533–539, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910500385258
Tetra-n-butylammonium Hydroxide
TBAH)–Catalyzed Knoevenagel
(
Condensation: A Facile Synthesis of
a-Cyanoacrylates, a-Cyanoacrylonitriles,
and a-Cyanoacrylamides
Saeed Balalaie and Morteza Bararjanian
Chemistry Department, K. N. Toosi University of Technology,
Tehran, Iran
Abstract: Tetra-n-butylammonium hydroxide (TBAH) has been utilized as a novel and
efficient catalyst for the Knoevenagel condensation of aldehydes with acidic methylene
compounds such as methyl- and ethylcyanoacetate, malononitrile, and cyanoacetamide
to afford substituted olefins.
Keywords: Active methylene compounds, aldehydes, alkenes, Knoevenagel conden-
sation, microwave irradiation, tetra-n-butylammonium hydroxide
INTRODUCTION
The Knoevenagel condensation is an important carbon–carbon bond-forming
[
1]
reaction in organic synthesis. The Knoevenagel reaction has been widely
used in organic synthesis to prepare coumarins and their derivatives, which
are important intermediates in the synthesis of cosmetics, perfumes, and
[
2]
pharmaceuticals. The Knoevenagel reaction is generally carried out in the
presence of weak bases such as primary and secondary amines and their cor-
responding ammonium salts, potassium fluoride, or amino acids such as
[3]
glycine, b-alanine, and L-proline under homogeneous conditions. But
Received in India July 25, 2005
Address correspondence to Saeed Balalaie, Chemistry Department, K. N. Toosi
University of Technology, P.O. Box 15875-4416, Tehran, Iran. Fax: 0098-21-285
3650; E-mail: balalaie@yahoo.com and balalaie@kntu.ac.ir
5
33

5
34
S. Balalaie and M. Bararjanian
[
4]
there are only a few acidic catalysts that are known to promote this reaction.
[5]
[6]
Recently, using inorganic solid supports such as alumina, Al O -AlPO ,
3
2
4
[
7]
[8]
xonotlite/tert-butoxide, cation-exchanged zeolites, calcite or fluorite,
NP/KF, and also some basic solid catalysts under heterogeneous conditions
[9]
have been reported as suitable methods for the Knoevenagel condensation.
During the past decade, microwave-assisted reactions have received
much attention because of their simplicity in operation, enhanced reaction
rates, and greater selectivity. Meanwhile, solvent-free conditions under
[10]
microwave irradiation were used for the Knoevenagel condensation.
It was found that Knoevenagel condensation could be catalyzed in
[
11]
water.
catalyze Knoevenagel condensation.
It was recently reported that triphenylphosphate (TPP) can
[12]
All these improved procedures can overcome the drawback of the
classical methods. Some reported methods normally require prolonged
reaction time, high temperatures, and harmful organic solvents.
In this report, we highlight our findings on the tetra-n-butylammonium
hydroxide (TBAH)–catalyzed condensation of active methylene compounds
such as malononitrile, alkyl cyanoacetates, and cyanoacetamide with
aromatic and heteroaromatic aldehydes in water and in room temperature.
RESULTS AND DISCUSSION
TBAH has been used as a basic catalyst for a variety of organic transformations
[
such as arylation, Robinson annulation, intramolecular Horner–Emmons
13]
[14]
[
15]
[16]
[17]
closure,
1
dehydration,
2.5mol% solution in H O, which is an advantage for this reaction because
and formation of carbenes.
This reagent is a
2
the reaction could be carried out in aqueous phase, and it could also be used
as a charge transfer catalyst. The reaction of benzaldehyde with ethyl cyanoace-
tate in the presence of 12.5mol% TBAH in water resulted in the formation of
ethyl 2-cyano-3-phenyl-(E)-2-propenoate in 84% pure yield under microwave
irradiation. In all cases, the reaction proceeds smoothly with 12.5mol% of
TBAH in a mixture of EtOH–H O (1:1) at room temperature or under
2
microwave irradiation. TBAH acts as a strong base capable of deprotonating
the active methylene compounds with the consequent formation of a
carbanion. The reaction is highly stereoselective and affords a,b-ethylenic
compounds in excellent yields with an E-geometry (Scheme 1).
Scheme 1.

TBAH–Catalyzed Knoevenagel Condensation
535
Furthermore, the amount of TBAH was 0.1 equivalents in all of the room-
temperature reactions and 0.3 equivalents under microwave (MW) irradiation.
These ratios were optimized for all of the reactions. We had the Cannizzaro
by-products in higher ratios of TBAH. At room temperature and also under
MW condition, all of the reactions were carried out in a 1:1 mixture of
ethanol–H O. In addition, the use of TBAH as a catalyst helps to avoid the
2
environmentally unfavorable solvents as the reaction medium, because the
reactions proceeds smoothly in the mixture of environmentally friendly
solvents (ethanol and water). Microwave irradiation has been used as an
attractive synthetic tool to achieve enhanced rates and improved yields.
Potassium or natrium hydroxide cannot be used as the base for this reaction,
because the Cannizzaro products will be formed as by-products. Only by
using TBAH was no other by-product formed and alkene was the unique
product. Electron-deficient aldehydes gave relatively higher yields than
electron-rich counterparts. The absence of a carbonyl group of aldehydes in
1
the IR spectra and appearance of olefinic hydrogens in H NMR spectra at
the 7.3–8.3 ppm region are indicative of the reaction products. The tempera-
ture in the microwave was controlled by pulsed irradiation (1 min with 20-s
intervals).
In conclusion, TBAH was employed for the first time as a novel and
efficient catalyst for the preparation of olefin compounds through the
Knoevenagel condensation at room temperature and also under microwave
irradiation in a mixture of EtOH–H O (1:1). Mild reaction conditions, high
2
yields, high conversions, cleaner reaction profiles, operational simplicity
and readily available catalyst will make this method an efficient environmen-
tally friendly and attractive strategy for the preparations of olefins.
EXPERIMENTAL SECTION
¨
Melting points were recorded on a BUCHI B-545 melting-point apparatus and
are uncorrected. IR spectra were recorded on a FT-IR Perkin-Elmer spectrum
1
spectrophotometer using KBr disks. H NMR data were recorded on JEOL-
1
9
0 spectrometer in CDCl using TMS as the internal standard. A domestic
3
microwave oven (Moulinex 2735 A) at 2450 MHz (100% power correspond-
ing to 850 W) was used in all experiments.
General Procedure for the Preparation of a,b-Unsaturated
Compound at Room Temperature
A mixture of aldehyde (5 mmol), alkylcyanoacetate (6 mmol), and TBAH
(0.5 mmol) 12.5 mol% in a 60-mL mixture of solvents (EtOH–H O 1:1)
2
was stirred at room temperature for the required time to complete the
reaction (Table 1). Progress of the reaction was monitored by TLC. After

5
36
S. Balalaie and M. Bararjanian
Table 1. Synthesis of alkenes via Knoevenagel codensation at room temperature with
microwave irradation
Time
(min)
Yield
a
(%)
No.
R
X
Condition
a
b
c
d
e
f
C
C H
6
H
5
5
5
CN
MW
MW
MW
r.t
4
4
89
84
79
91
94
93
94
96
85
71
77
96
90
91
84
COOEt
COOMe
CN
6
C H
6
4
p-(Me
p-(Me
2
N)-C
N)-C
6
H
H
4
4
4
4
10
10
10
10
10
4
2
6
CONH
2
r.t
p-(Me N)-C H
2
COOEt
COOMe
CN
r.t
6
g
h
i
p-(Me
2
N)-C
6
H
r.t
p-OH-C
p-OH-C H
6
H
4
r.t
COOEt
COOEt
COOMe
CN
r.t
6
4
j
m-NO
m-NO
2
-C
-C
6
6
H
H
4
r.t
30
30
10
10
10
30
k
l
2
4
r.t
p-NO -C H
r.t
2
2
2
6
6
6
4
m
n
o
p-NO
p-NO
-C
-C
H
H
4
4
COOEt
COOMe
COOEt
r.t
r.t
2-Thienyl
r.t
a
In all cases, the yields are pure forms after purification.
completion of the reaction, the mixture was neutralized by the addition of
hydrochloric acid (2 M). The precipitate was filtered off and washed with
water. Further purification was done by recrystalization with EtOH.
General Procedure for the Preparation of a,b-Unsaturated
Compounds under Microwave Irradiation
A tall beaker containing a mixture of aldehyde (5 mmol), alkylcyanoacetate
(
(
6 mmol), and TBAH (1.5 mmol) 12.5 mol% in a 5-mL mixture of solvents
EtOH–H O 1:1) was placed in the microwave oven. The beaker was
2
covered with a watch glass and irradiated under microwave irradiation at
00% power (850 W) for 4 min in 1-min intervals (Table 1). The workup
1
procedure was the same as the previous procedure. Most of compounds are
known, and products were identified by spectral and melting-point comparison
with the authentic samples.
Selected Data for Compounds 3a–p
2
1
3
3
7
a: 1,1-dicyano-2-phenylethylene: mp 838C (lit:828C[6]); IR (KBr, cm
)
436, 2917, 2223, 1731; H-NMR (d, CDC13) 7.90 (s, 1H, H–C 55 C),
1
.50–8.15 (m, 5J, Ar)

TBAH–Catalyzed Knoevenagel Condensation
537
[
6]
3
(
b: Ethyl (E)-2-cyano-3-phenyl-2-propenoate: mp 478C (lit: 498C ); IR
KBr, cm ) 3033, 2953, 2225, 1729.
2
1
[
10a]
3
c: Methyl (E)-2-cyano-3-phenyl-2-propenoate: mp 878C (lit: 898C
);
IR (KBr, cm ) 3031, 2983, 2224, 1728; H-NMR (d CDCI ) 3.90 (s, 3H,
2
1
1
3
OMe), 7.70–8.15 (m, 5H, Ar), 8.25 (s, 1H, H–C 55 C).
3
2
d: 2(4-N,N-dimethylaminophenylmethylene) malononitrile: mp 1838C (lit:
[18] 21
008C ; IR (KBr, cm ) 2915, 2210, 1614, 1567.
3
e: 2-cyano-3-(N,N-dimethylaminophenyl)-2-propenamide: mp 1998C
[
18]
21
(lit:2008C ); IR (KBr, cm ) 3405, 3156, 2200, 1683, 1610, 1561.
3
1
1
f: Ethyl-(E)-2-cyano-3-(4-N,N-dimethylaminophenyl)-2-propenoate: mp
2
1
1
258C; IR (KBr, cm ) 2944, 2212, 1713, 1611, 1575; H-NMR (d, CDCl )
3
.40 (t, 3H, J ¼ 8 Hz, CH ), 3.10 (s, 6H, 2Nme), 4.30 (q, 2H, J ¼ 8 Hz,
2
OCH ), 6.70 (d, 2H, J ¼ 9 Hz, Ar), 7.90 (d, 2H, J ¼ 9 Hz, Ar), 8.10 (s, 1H,
2
55 CH).
3
1
3
g: Methyl (E)-2-cyano-3-(4-N, N-dimethylaminnophenly)-2-propenoate: mp
2
1
1
468C; IR (KBr, cm ) 2907, 2215, 1715, 1610, 1575; H-NMR (d, CDCl )
3
.10 (s, 6H, –Nme ), 3.90 (s, 3H, OMe), 6.70 (d, 2H, J ¼ 9 Hz, Ar). 7.90
2
(d, 2H, J ¼ 9 Hz, Ar), 8.20 (s, 1H, –CH).
[19]
3
IR (KBr, cm ) 3346, 2923, 2230, 1615, 1563; H-NMR (d CDCl3) 7.0
h: 2-(4-Hydroxphenylmethylene)malononitrile: mp 1908C (lit: 1888C );
21 1
(
d, 2H, J ¼ 9 Hz, Ar), 7.90 (d, 2H, J ¼ 9 Hz), 8.30 (s, 1H, –CH), 11.0 (brs,
1
H, OH).
3
i: Ethyl (E)-2-cyano-3(4-hydroxyphenyl)-2-propenoate: mp 1748C (lit:
[
20]
21
1
728C ); IR (KBr, cm 3293, 2981, 2229, 1715, 1519.
3
j: Ethyl (E)-2-cyano-4-(3-nitrophenly)-2-propenoate: mp 1398C; IR (KBr,
2
1
1
cm ) 3036, 2226, 1727, 1609, 1537, 1359; H-NMR (d CDCl3) 1.50
t, 3H, J ¼ 7.2 Hz, CH ), 4.40 (q, 2H, J ¼ 7.2 Hz, OCH ), 7.6–8.5 (m, 4H,
(
Ar), 8.7 (s, 1H, 55 CH).
3
2
3
k: Methyl (E)-2-cyano-4-(3-nitrophenyl)-2-propenoate: mp 1358C
[
10c]
21
); IR (KBr, cm ) 3080, 2226, 1720, 1609, 1536, 1359.
(lit:1358C
[
16]
3
(
l: 2-(4-nitrophenylmethylene)malononitrile: m.p. 1608C (lit: 1598C ); IR
21 1
KBr, cm ) 3110, 2231, 1604, 1521, 1344; H-NMR (d CDCl3) 7.88
s, 1H, H 22 C 55 C), 8.10 (d, 2H, J ¼ 7.2 Hz, Ar), 8.39 (d, 2H, J ¼ 7.2 Hz, Ar).
(
3
1
m: Ethyl (E)-2-cyano-3(4-nitrophenyl)-2-propenoate: mp 1698C (lit:
688C ); IR (KBr, cm ) 3096, 2211, 1721, 1593, 1514, 1347.
[6] 21
3
n: Methyl-(E)-2-Cyano-3(4-nitrophenyl)-2-propenoate: mp 1788C; IR (KBr,
2
1
1
cm ) 3119, 2847, 2225, 1731, 1613; H-NMR (d CDCl3) 4.0 (s, 3H, OMe),
.15 (d, 2H, J ¼ 9 Hz, Ar), 8.34 (s, 1H, H–C 55 C), 8.38 (d, 2H, J ¼ 9 Hz, Ar).
8

5
38
S. Balalaie and M. Bararjanian
3
o: Ethyl (E)-2-Cyano-3(2-thienyl)-2-propenoate: mp 105–1088C, IR (KBr,
2
1
1
cm ): 3085, 2215, 1715, 1600, 1460, H-NMR (d, CDCl3) 1.38 (t, 3H,
J ¼ 6.9 Hz, CH ) 4.38(q, 2H J ¼ 6.9 Hz, OCH ) 7.22–7.30 (dd, 1H, J ¼ 8.8,
3
2
3
.9 Hz, 1H), 7.78(d, 1H, J ¼ 4.4 Hz), 7.83(d, 1H, J ¼ 3.6 Hz), 8.3(s,1H, 55 CH).
ACKNOWLEDGMENTS
We are grateful to the Alexander von Humboldt foundation for the research
fellowship and financial support.
REFERENCES
1
2
. Jones, G. The Knovenagel condensation reaction. In Organic Reactions; Wiley:
New York, 1967; Vol. 15, p. 204.
. (a) Tietze, L.; Beifuos, V. Comprehensive Organic Synthesis; Trost, B. M.,
Fleming, I., Heathcock, C. H., Eds.; Pergamon: Oxford, 1991; Vol. 2;
Chapter 1.11, 341–392; (b) Bigi, F.; Chesini, L.; Maggi, R. R.; Sartori, G.
Montmorillonite KSF as an inorganic, water soluble, and reusable catalyst for
the Knoevenagel synthesis of coumarin-3-carboxylic acids. J. Org. Chem. 1999,
6
4, 1033; (c) Yu, N.; Aramini, J. M.; Germann, M. W.; Huang, Z. Tetrahedron
Lett. 2000, 41, 6993; (d) Balalaie, S.; Nemati, N. One-pot preparation of
coumarins by Knoevenagel condensation in solvent-free condition under
microwave irradiation. Heterocycl. Commun. 2001, 7, 67; (e) Su, C.;
Chen, Z. C.; Zheng, Q. G. Organic reactions in ionic liquids: Knoevenagel conden-
sation catalyzed by ethylenediammonium diacetate. Synthesis 2003, 555.
3
. (a) Allen, C. F. H.; Spangler, F. W. Org. Synth. Coll. 1955, III, 377;
(b) Sakthivel, K.; Notz, W.; Bui, T.; Barbas, C. F., III. Amino acid–catalyzed
direct asymmetric aldol reactions: A biomorganic approach to catalytic asym-
metric carbon–carbon bond forming reactions. J. Am. Chem. Soc. 2001, 123,
5
260; (c) Groger, H.; Wilken, J. The application of L-proline as an enzyme
mimic and further new asymmetric syntheses using small organic molecules as
chiral catalysts. Angew. Chem. Int. Ed. Engl. 2001, 40, 529; (d) Cardillo, G.;
Fabbroni, S.; Gentilucci, L.; Gianotti, M.; Tolomelli, A. A straightforward
method for the synthesis of alkylidene and arylidene malonates through proline-
catalyzed Knoevenagel condensation. Synth. Commun. 2003, 33, 1587.
4
. (a) Prajapati, D.; Lekhok, K. C.; Sandhu, J. S.; Ghosh, A. C. Lithium bromide as a
new catalyst for carbon–carbon bond formation in the solid state. J. Chem. Soc.
Perkin Trans. 1 1996, 959; (b) Rao, P. S.; Ratnam, R. V. Zinc chloride as a new
catalyst for Knoevenagel condensation. Tetrahedron Lett. 1991, 32, 5821;
(
c) Narsaiah, A. V.; Nagaiah, K. An efficient Knoevenagel condensation
.
catalyzed by LaCl3 7H2O in heteregenous medium. Synth. Commun. 2003, 33,
819.
3
5. Texier-Boullet, F.; Foucod, A. Knoevenagel condensation catalyzed by aluminium
oxide. Tetrahedron Lett. 1982, 23, 4927.
6. Cabello, J. A.; Campelo, J. M.; Garcia, A.; Luna, D.; Marians, J. M. Knoevenagel
4 2 3
condensation in the heterogenous phase using AlPO -Al O as a new catalyst.
J. Org. Chem. 1984, 49, 5195.

TBAH–Catalyzed Knoevenagel Condensation
539
7
. (a) Loupy, A. Solvent-free reactions. Top. Curr. Chem. 1999, 206, 153;
b) Laszlo, P. Catalysis of organic reactions by inorganic solids. Acc. Chem.
(
Res. 1986, 19, 121.
8
. (a) Rodriguez, I.; Iborra, S.; Corma, A.; Rey, F.; Jorda, J. L. MCM-14-quaternary
organic tetraalkylammonium hydroxide composites as strong and stable Bronsted
base catalysts. J. Chem. Soc., Chem. Commun. 1999, 593; (b) Wang, Q. L.; Ma, Y.;
Zuo, B. Knoevenagel condensation catalyzed by USY zeolite. Synth. Commun.
1
997, 27, 4107.
. (a) Kloetstra, K. R.; Bekkum, H. V. J. Chem. Soc., Chem. Commun. 1995, 1005;
b) Wada, S.; Suzuki, H. Calcite and fluoride as catalyst for the Knoevenagel con-
9
(
densation of malononitrile and methyl cyanoacetate under solvent-free conditions.
Tetrahedron Lett. 2003, 44, 399; (c) Sebti, S.; Smahi, A. V.; Solhy, A. Natural
phosphate doped with potassium fluoride and modified with sodium nitrate:
Efficient catalysts for the Knoevenagel condensation. Tetrahedron Lett. 2002,
43, 1813; (d) Inaki, Y.; Kajita, Y. H.; Ito, K.; Hattori, T. J. Chem. Soc., Chem.
Commun. 2001, 2358; (e) Siebenhaar, B.; Casagrande, B.; Studer, M.;
Blaser, H.-U. Can. J. Chem. 2001, 79, 566.
1
0. (a) Ayoubi, S. A.; Texier-Boullet, F.; Hamelin, J. Minute synthesis of electrophilic
alkenes under microwave irradiation. Synthesis 1994, 258; (b) Ayoubi, S. A.;
Texier-Boullet, F. Clay-mediated synthesis of gem-bis(alkoxycarbonyl)alkenes
under microwave irradiation. J. Chem. Res. Synop. 1995, 208; (c) Balalaie, S.;
Nemati, N. Ammonium acetate—basic alumina-catalyzed Knoevenagel conden-
sation under microwave irradiation and solvent-free condition. Synth. Commun.
2000, 30, 869 and references therein; (d) Loupy, A.; Petit, A.; Hamelin, J.;
Texier-Boullet, F.; Jacqualt, P.; Mathe, F. New solvent-free organic synthesis
using focused microwave. Synthesis 1998, 1213; (e) Varma, R. S. Solvent-free
reactions under microwave irradiations. Green Chem. 1999, 1, 43;
(
f) Kaupp, G.; Naimi-Jamal, M. R.; Schmeyers, J. Solvent-free Knoevenagel con-
densation and Michael addition in the solid state in the melt with quantitive yield.
Tetrahedron 2003, 59, 3753.
1
1. (a) Hangarge, R. V.; Sonwane, S. A.; Jarikote, D. V.; Shingare, M. S. Water-
mediated uncatalyzed facile synthesis of ylidenenitriles of 4-oxo-(4H)-1-benzo-
pyran-3-carbaldehyde. Green Chem. 2001, 3, 310; (b) Wang, S.; Ren, Z.;
Cao, W.; Tong, W. The Knoevenagel condensation of aromatic aldehydes with
malononitrile or ethyl cyanoacetate in the presence of CTMAB in water. Synth.
Commun. 2001, 31, 673; (c) Ren, Z.; Cao, W.; Tong, W.; Jing, X. Synth.
Commun. 2002, 32, 1947.
1
2. Yadav, J. S.; Reddy, B. S.; Basak, A. K.; Visali, B.; Narsaiah, A. V.; Nagaiah, K.
Phosphane-catalyzed Knoevenagel condensation: A facile synthesis of a-cyano-
acrylates and a-cyanoacrylonitriles. Eur. J. Org. Chem. 2004, 546.
3. Paquette, L. A. Encyclopedia of Reagents for Organic Synthesis. Wiley:
New York, 1995; Vol. 7, p. 4735.
1
1
1
1
1
1
4. Chen, E. Y. Synth. Commun. 1983, 13, 927.
5. Rao, Y. K.; Nagarajan, M. Tetrahedron Lett. 1988, 29, 107.
6. Ryback, G. U.S. Pat. 4,855,512, Chem. Abstr. 1989, 110, 134 878r.
7. Saa, J. M.; Cava, P. M. J. Org. Chem. 1977, 42, 347.
8. Obrador, E.; Castro, M.; Tamariz, J.; Zepeda, G.; Miranda, R.; Delgde, F.
Knoevenagel condensation in heterogenous phase catalyzed by IR irradiation
and tonsil actisil FF. Synth. Commun. 1998, 28, 4649.
1
2
9. Corson, B. B.; Stoughton, R. W. J. Am. Chem. Soc. 1928, 50, 2825.
0. Mitra, A. K.; De, N.; Karchaudhuri, A. Synth. Commun. 1999, 29, 2731.