Three-component synthesis of pyrimidine and pyrimidinone derivatives in the presence of high-surface-area MgO, a highly effective heterogeneous base catalyst

Article abstract of DOI:10.1080/00397910802474982

Magnesium oxide (MgO) effectively catalyzes the three-component reaction of aldehydes, amidine systems, and malononitrile or ethyl cyanoacetate to form 4-amino-5-pyrimidine carbonitrile and pyrimidinone derivatives, respectively. The salient features of t

Full text of DOI:10.1080/00397910802474982

This article was downloaded by: [University of Calgary]
On: 21 September 2013, At: 19:47
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
Three-Component Synthesis of
Pyrimidine and Pyrimidinone
Derivatives in the Presence
of High-Surface-Area MgO, a
Highly Effective Heterogeneous
Base Catalyst
Hassan Sheibani a , Mohammad Seifi a & Ayoob
Bazgir b
a Department of Chemistry, Shahid Bahonar
University of Kerman, Kerman, Iran
b Department of Chemistry, Shahid Beheshti
University, Tehran, Iran
Published online: 25 Feb 2009.
To cite this article: Hassan Sheibani , Mohammad Seifi & Ayoob Bazgir (2009) Three-
Component Synthesis of Pyrimidine and Pyrimidinone Derivatives in the Presence of
High-Surface-Area MgO, a Highly Effective Heterogeneous Base Catalyst, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 39:6, 1055-1064, DOI: 10.1080/00397910802474982
To link to this article: http://dx.doi.org/10.1080/00397910802474982
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

Synthetic Communications1, 39: 1055–1064, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802474982
Three-Component Synthesis of Pyrimidine and
Pyrimidinone Derivatives in the Presence
of High-Surface-Area MgO, a Highly
Effective Heterogeneous Base Catalyst
Hassan Sheibani,1 Mohammad Seifi,1 and Ayoob Bazgir2
1Department of Chemistry, Shahid Bahonar University of Kerman,
Kerman, Iran
2Department of Chemistry, Shahid Beheshti University, Tehran, Iran
Abstract: Magnesium oxide (MgO) effectively catalyzes the three-component
reaction of aldehydes, amidine systems, and malononitrile or ethyl cyanoacetate
to form 4-amino-5-pyrimidine carbonitrile and pyrimidinone derivatives, respec-
tively. The salient features of this method include high conversions, short reaction
times, cleaner reaction profiles, and the use of inexpensive and readily available
catalyst.
Keywords: Amidines, 4-amino-5-pyrimidinecarbonitriles, magnesium oxide
(MgO), malononitrile, three-component reaction
INTRODUCTION
In recent years, pyrimidines and dihydropyrimidinones (DHPMs) have
occupied an important position in natural and synthetic organic chemis-
try, due mainly to their wide range of biological activities.[1] such as
antibacterial, antiviral, antihypertensive, and antitumor effects and their
effect as calcium channel blockers.[2] Moreover, some bioactive alkaloids
such as batzelladine B, containing the dihydropyrimidine unit, have been
Received August 27, 2008.
Address correspondence to Hassan Sheibani, Department of Chemistry,
Shahid Bahonar University of Kerman, Kerman 76169, Iran. E-mail: hsheibani@
mail.uk.ac.ir
1055

1056
H. Sheibani, M. Seifi, and A. Bazgir
isolated from marine sources and show anti-HIV activity.[3] The develop-
ment of efficient and environmentally acceptable synthetic methods is an
important task of modern chemistry. Conventional organic syntheses
are generally based on homogeneous catalysts. However, homogeneous
reactions suffer disadvantages in separation, regeneration, and so forth.
From the viewpoint of green chemistry, the use of heterogeneous cata-
lysts is desirable. The consequential advantages of heterogeneous
catalysts from the environmental and economic points of view are clearly
understandable, because these procedures allow money to be saved and
the production of waste material to be minimized.
In contrast to the extensive studies involving heterogeneous acid
catalysts, fewer efforts have been made to develop heterogeneous base
catalysts.[4] Several solid bases have been reported as being effective in
this respect, such as zeolites,[5] alkali metals supported on alumina
(Na=NaOH=g-Al2O3),[6] clay minerals,[7] hydrotalcites (HDT),[8] metal
oxides such as magnesium oxide (MgO), and mixed metal oxides, for
example magnesium–lanthanum mixed oxide.[9] Among these solid bases,
MgO recently has been studied the most.[10] MgO, obtained using a novel
but simple procedure, was systematically investigated as a heterogeneous
base catalyst for reactions taking place in the liquid phase, specifically the
Michael addition and the Knoevenagel condensation.[10] More recently,
we described the synthesis of 2-amino-5-pyrimidinecarbonitriles 4 based
on the three-component reaction of malononitrile 3 , aromatic aldehydes
1, and amidines 2 under thermal aqueous conditions and microwave
irradiation in the presence of sodium acetate.[11] As part of our research
program aimed at the preparation of nitrogen-containing hetero-
cycles,[12–14] we performed the synthesis of 4-amino-5-pyrimidinecarboni-
trile 4 and dihydro-5-pyrimidinonecarbonitrile 5 derivatives through a
three-component reaction in the presence of MgO as a highly effective
heterogeneous base catalyst.
RESULTS AND DISCUSSION
In the present protocol as exhibited in Scheme 1, the three-component
reaction of ethyl cyanoacetate, arylaldehydes, and amidines under
thermal aqueous conditions did not afford the dihydropyrimidinone-5-
carbonitrile derivatives 5, although these compounds were prepared in
the presence of MgO under reflux condition.
Xu and co-workers investigated the reaction of a high-surface-area
form of MgO as a catalyst for a number of different Michael additions
and Knoevenagel condensations, and it was found to be very active
and reusable.[10] We sought to develop a route that is simple to perform

Pyrimidine and Pyrimidinone Derivatives
1057
Scheme 1. Three component reactions of aldehydes, amidine systems, and
malonitrile or ethyl cyanoacetate in the presence of magnesium oxide (MgO).
and that allows reuse of the catalyst for a number of times. We tried to
focus on aqueous media, where the product would be precipitated out
from the reaction mixture when the reaction is completed. Yields are rela-
tively low when water was used as a solvent in comparison with an anhy-
drous solvent such as acetonitrile. The results are summarized in Table 1.
Because the three-component reaction of malononitrile or ethyl cya-
noacetate, aromatic aldehydes, and amidines involves both Knoevenagel
condensation and Michael addition, we have separately studied the
effect of catalytic activity of MgO on the Knoevenagel condensation of
malononitrile or ethyl cyanoacetate and aldehydes 1 to afford the
a-cyanocinnamonitrile 6a or ethyl-2-cyano-3-aryl-2-propenoate 6b deri-
vatives, respectively, and also the Michael addition of amidine systems
Table 1. Solvent effects on the synthesis of compounds
4a and 5a
Compound
Solvent
Time (min)
Yield (%)
4a
4a
4a
5a
5a
5a
EtOH=H2O
MeOH
MeCN
EtOH=H2O
MeOH
MeCN
30
25
20
50
45
40
72
78
85
76
79
82

1058
H. Sheibani, M. Seifi, and A. Bazgir
with compounds 6 in the same conditions. The catalyst plays a crucial
role in the success of the reaction in terms of the rate and the yields.
Our observations are recorded in Tables 2 and 3.
On basis of these results, we report a novel, three-component,
one-pot synthesis of functionalized 4-amino-5-pyrimidinecarbonitrile 4
and dihydro-5-pyrimidinonecarbonitrile 5 derivatives in the presence of
high-surface-area MgO, a highly effective heterogeneous base catalyst
in acetonitrile at reflux conditions. This is an efficient synthesis in opera-
tional simplicity and also gives the corresponding products in high yields
in a very short experimental time. The reaction conditions and results are
shown in Table 4.
Structures 4a–s were established on the basis of infrared (IR), which
showed the presence of a CN group at a region of 2235–2238 cmꢀ1 and
two sharp bands at 3500–3450 and 3390–3380 cmꢀ1, which are due to
1
the asymmetric and symmetric vibrations of NH2 group. The H and
13C NMR spectroscopic data were comparable with reported data.[11]
The structures of 5a–f were determined on the basis of their elemental
1
analyses, mass spectra, H and 13C NMR data, and IR spectral data.
The mechanism of the present reaction (Scheme 1) initially proceeds
by Knoevenagel condensation, as the catalyst possesses strong basic sites,
which promote the reaction by abstracting a proton from the active
methylene component. As a result, an alkene intermediate may form with
the aldehyde. This in turn reacts with amidines via Michael addition to
give the polyfunctionalized pyrimidine and dihydropyrimidinone deriva-
tives (Scheme 2).
Table 2. Knoevenagel condensation of aldehydes with malononitrile or ethyl
cyanoacetate catalyzed by MgO in CH3CN
Compound
Ar
C6H5
C6H5
4-ClC6H4
4-ClC6H4
X
Time (min) Yield (%) MP [Ref.] (ꢁC)
6a
6b
6c
6d
6e
6f
CN
5
10
5
94
90
96
91
98
92
82–83[15]
48–50[15]
158[16]
93[16]
CO2Et
CN
CO2Et
8
4
7
4-O2NC6H4 CN
4-O2NC6H4 CO2Et
160[17]
170[17]

Pyrimidine and Pyrimidinone Derivatives
1059
Table 3. Michael additions of 6 with amidines catalyzed by MgO in CH3CN
Compound
Ar
C6H5
C6H5
C6H5
4-ClC6H4
4-ClC6H4
4-ClC6H4
R
Time (min)
Yield (%)
4a
4b
5a
4h
4i
C6H5
NH2
C6H5
C6H5
NH2
C6H5
18
13
26
13
11
32
90
92
97
96
97
95
5b
CONCLUSION
In summary, an efficient heterogeneous strong base such as MgO catalyst
with high surface area is reported for the synthesis of 4-amino-5-pyrimi-
dinecarbonitrile and pyrimidinones derivatives in a three-component
reaction of aldehydes, amidin systems, and malononitrile or ethyl cya-
noacetate respectively. Advantages of the strategy include simple catalyst
preparation, mild reaction temperature, easy recovery, and reusability of
the catalyst with consistent activity and short reaction times.
EXPERIMENTAL
Melting points were determined on an Gallenkamp melting-point
apparatus and are uncorrected. IR spectra were measured on a Mattson
1000 Fourier transform infrared (FT-IR) spectrometer. 1H NMR and 13
C
NMR spectra were determined on a Bruker DRX-300 Avance spectro-
meter at 300.13 and 75.47 MHz, respectively. Mass spectra (MS) were
recorded on a Shimadzu QP 1100EX mass spectrometer operating at

1060
H. Sheibani, M. Seifi, and A. Bazgir
Table 4. Synthesis of 4a–s and 5a–f under thermal conditions without catalyst
and in the presence MgO as a highly effective heterogeneous base catalyst
Commercially
available
MgO
High-
surface-area
MgO
Thermal
conditions
Time Yield Time Yield Time Yield
(%)
Compound
Ar
C6H5
C6H5
4-MeC6H4
4-MeC6H4
4-MeOC6H4 Ph
R
(h)
(%)
(min) (%)
(min)
4a
4b
4c
4d
4e
4f
Ph
NH2
Ph
6
5
78
81
79
64
60
78
60
55
65
60
70
90
83
86
81
84
80
80
20
15
20
22
30
40
85
88
83
86
82
83
4
5
8
12
NH2
4-(Me)2N
C6H4
Ph
4g
Ph
6
46
70
65
30
70
4h
4i
4-ClC6H4
4-ClC6H4
4-BrC6H4
4-BrC6H4
4-FC6H4
4-FC6H4
3-FC6H4
3-FC6H4
3-FC6H4
4-CF3C6H4
4-CF3C6H4
4-CF3C6H4
C6H5
Ph
NH2
Ph
NH2
NH2
Ph
4
3
4
4
4
4
3
4
5
2
4
5
—
—
—
—
—
—
73
82
80
78
63
66
80
68
60
70
72
60
—
—
—
—
—
—
50
45
58
52
48
45
50
45
60
53
50
65
120
110
100
110
105
100
87
90
84
87
88
91
87
92
83
83
87
80
80
84
84
82
86
87
15
13
18
15
14
12
10
8
20
17
15
25
40
35
33
36
33
33
89
91
87
89
90
92
90
96
85
88
90
83
82
85
86
84
88
89
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
5a
5b
5c
5d
5e
5f
Ph
NH2
Me
Ph
NH2
Me
ph
ph
ph
ph
ph
4-ClC6H4
3-FC6H4
4-CF3C6H4
2,4-ClC6H3
4-NO2C6H4 ph
an ionization potential of 70 eV. Elemental analyses were performed
using a Heracus CHN-O-Rapid analyzer.
Preparation of High-Surface-Area MgO
A simple method for the preparation of MgO, a catalyst that exhibits high
activity for base-catalyzed reactions, is described.[10] The experimental

Pyrimidine and Pyrimidinone Derivatives
1061
Scheme 2. Mechanism for the formation of compounds 4 and 5.
results showed that an optimal calcination temperature in the range of
ꢁ
400–500 C gives poorly crystalline, high-surface-area MgO, which can
be regenerated by washing and then reused.[10] MgO can be recovered
and reused twice without loss of activity of the catalyst.
General Procedure for the Preparation of Pyrimidine and
Pyrimidinone Derivatives
A mixture of the aldehyde (2 mmol), amidines hydrochloride (2 mmol),
malononitrile or ethyl cyanoacetate (2 mmol), and MgO (0.25 g) in
CH3CN (5 mL) was refluxed with stirring for the time reported in
Table 1. The progress of the reaction was monitored by thin-layer
chromatography (TLC), and hexane=ethyl acetate was used as an eluent).
After completion of the reaction, the catalyst was separated from the
reaction mixture by centrifugation. The excess acetonitrile was removed
by evaporation and then was poured into ice-cold water; the
crude product was filtered, dried, and recrystallized from 96% ethanol.
Data
6-Oxo-2,4-diphenyl-1,6-dihydro-5-pyrimidinecarbonitrile (4a)
Yellow crystals; mp 105 ꢁC. IR (KBr, nmax=cmꢀ1): 3329 (NH), 2212 (CN),
1691 (C O), 1617 (C¼N), 1542, 1492 (C¼C); 1H NMR (300 MHz,
=
DMSO-d6): 9.62 (s, 1H, NH), 8.32–7.29 (m, 10 H, Ar). 13C NMR

1062
H. Sheibani, M. Seifi, and A. Bazgir
(75 MHz, DMSO-d6): 173.50, 168.29, 166.51, 138.96, 138.55, 130.72,
130.34, 129.40, 128.89, 128.66, 128.63, 120.88 (CN), 91.47 (C5). MS
(m=z): 273 (Mþ) (30), 245 (35), 170 (50), 142 (15), 120 (60), 104 (87),
77 (50), 53 (25). Anal. calcd. for C17H11N3O: C, 74.71; H, 4.06; N,
15.38%. Found: C, 74.37; H. 3.92; N; 15.05%.
4-(4-Chlorophenyl)-6-oxo-2phenyl-1,6dihydro-5-pyrimidine-
carbonitrile (4b)
Yellow crystals; mp 210–212 C. IR (KBr, nmax=cmꢀ1): 3478 (NH), 2212
ꢁ
(CN), 1690 (C¼O), 1617 (C¼N), 1542 (C¼C). 1H NMR (300 MHz,
DMSO-d6): 9.35 (s, 1H, NH); 8.31–7.33 (m, 9H, Ar). 13C NMR
(75MHz, DMSO-d6): 173.29, 167.00, 164.95, 138.82, 137.23, 135.16,
130.81, 130.61, 128.76, 128.60, 128.54, 120.12 (CN), 91.37 (C5). MS
(m=z): 307 (Mþ) (40), 272 (45), 145 (60), 104 (60), 77 (55), 51 (35). Anal.
calcd. for C17H10ClN3O: C, 66.35; H, 3.28; N, 13.65%. Found: C, 66.12;
H. 3.08; N; 13.31%.
4-(3-Fluorophenyl)-6-oxo-2-phenyl-1,6-dihydro-5-pyrimidine-
carbonitrile (4c)
White crystals; mp 105 ꢁC. IR (KBr, nmax=cmꢀ1): 3329 (NH), 2212 (CN),
1691 (C¼O), 1617 (C¼N), 1542, 1492 (C¼C). 1H NMR (300 MHz,
DMSO-d6): 9.35 (s, 1H, NH); 8.32–7.36 (m, 9H, Ar). 13C NMR
(75 MHz, DMSO-d6) 169.92, 166.81, 163.48, 162.30 (d, 1J
¼C–F
241.50 Hz), 140.27 (d, 3J¼C–F 7.50 Hz), 137.01, 131.48, 130.88 (d, 3J
¼C–F
21 Hz),
2
7.50 Hz), 128.76, 128.74, 125.03, 119.13 (CN), 117.58 (d, J
¼C–F
2
115.59 (d, J
22.50 Hz), 92.79 (C5). MS (m=z): 291 (Mþ) (60), 263
¼C–F
(65), 188 (90), 160 (25), 138 (20), 104 (75), 77 (80), 51 (35). Anal. calcd.
for C17H10FN3O: C, 70.10; H, 3.46; N, 14.43%. Found: C, 69.86; H,
3.22; N; 14.05%.
6-Oxo-2-phenyl-4-[4-trifluoromethyl)phenyl]-1,6-dihydro-
5-pyrimidinecarbonitrile (4d)
Yellow crystals; mp 125 ꢁC. IR (KBr, nmax=cmꢀ1): 3503 (NH), 2212 (CN),
1
1641(C¼O), 1592 (C¼N), 1567 (C¼C). H NMR (300 MHz, DMSO-d6)
9.55 (s, 1H, NH), 8.32–7.44 (m, 9H, Ar). 13C NMR (75 MHz, DMSO-d6):
172.72, 166.83, 165.04, 142.64, 139.06, 131.81 (q, 2J
22.50 Hz),
¼C–F
1
130.01, 129.58, 128.01 (q, JC-F 270.75 Hz, CF3), 125.86 (q, 3J
¼C–F
3.75 Hz), 120.04 (CN), 91.91 (C5). MS (m=z): 341 (Mþ) (60), 313 (65),

Pyrimidine and Pyrimidinone Derivatives
1063
238 (80), 221 (15), 194 (10), 172 (10), 145 (40), 104 (85), 77 (90), 51 (50).
Anal. calcd. for C18H10F3N3O: C, 63.35; H, 2.95; N, 12.31%. Found: C,
63.01; H. 2.90; N; 12.18%.
4-(2,4-Dichlorophenyl)-6-oxo-2-phenyl-1,6-dihydro-5-
pyrimidinecarbonitrile (4e)
Yellow crystals; mp 110ꢁC. IR (KBr, nmax= cmꢀ1): 3379 (NH), 2212 (CN),
1690 (C O), 1617 (C N), 1542, 1492 (C C). 1H NMR (300 MHz,
DMSO-d6): 9.37 (s, 1H, NH), 8.20–7.41 (m, 9H, Ar). 13C NMR
(75 MHz, DMSO-d6): 171.84, 167.26, 166.29, 138.94, 137.19, 134.59,
132.82, 132.13, 130.64, 129.51, 129.42, 128.78, 127.88, 119.15 (CN),
94.13 (C5). MS (m=z): 341 (Mþ) (90), 313 (75), 238 (85), 221 (60), 194
(25), 171 (20), 145 (65), 104 (80), 77 (90), 51 (40). Anal. calcd. for
C17H9Cl2N3O: C, 59.67; H, 2.65; N, 12.28%. Found: C, 59.35; H. 2.56;
N; 12.14%.
=
=
=
4-(4-Nitrophenyl)-6-oxo-2-phenyl-1,6-dihydro-5-
pyrimidinecarbonitrile (4f)
Brown crystals; mp 105 ꢁC. IR (KBr, nmax=cmꢀ1): 3379 (NH), 2212 (CN),
1
=
=
=
1680 (C O), 1592 (C N), 1517 (C C). H NMR (300 MHz, DMSO-d6):
9.52 (s, 1H, NH); 8.34–7.44 (m, 9H, Ar). 13C NMR (75 MHz, DMSO-d6):
172.53, 166.16, 165.03, 148.47, 144.81, 138.95, 130.74, 130.14, 128.54,
123.88, 120.04 (CN), 91.91 (C5). MS (m=z): 318 (Mþ) (10), 215 (10),
176 (15), 136 (70), 103 (7), 77 (75), 63 (90), 45 (40). Anal. calcd. for
C17H10N4O3: C, 64.15; H, 3.17; N, 17.60%. Found: C, 64.03; H. 3.02;
N; 17.45%.
ACKNOWLEDGMENTS
The authors express their appreciation to the Shahid Bahonar
University of Kerman Faculty Research Committee for its support of
this investigation.
REFERENCES
1. Dennis, R.; Romulo, F. S. C.; Sergio, A. A.; Marcelo, G. M. D.; Angelode,
F.; Ronaldo, A. P.; Luciana, K. K.; Marcia, A. A.; Joao Ernesto, C. Synth-
esis and differential antiproliferative activity of Biginelli compounds against

1064
H. Sheibani, M. Seifi, and A. Bazgir
cancer cell lines: Monastrol, oxo-monastrol, and oxygenated analogues.
Bioorg. Chem. 2006, 34, 173.
2. Kappe, C. O. Biologically active dihydropyrimidones of the Biginelli-type
a literature survey. Eur. J. Med. Chem. 2000, 35, 1043.
3. Patil, A. D.; Kumar, N. V.; Kokke, W. C.; Bean, M. F.; Freyer, A. J.; Brosse,
C. D.; Mai, S.; Trunch, A.; Faulkner, D. J.; Carte, B.; Breen, A. L.; Hertz-
berg, R. P.; Johnson, R. K.; Westley, J. W.; Pttos, B. C. M. Novel alkaloids
from the sponge batzella sp.: Inhibitors of HIV gpl2O-human CD4 binding.
J. Org. Chem. 1995, 60, 1182.
4. Hattori, H. Heterogeneous basic catalysis. Chem. Rev. 1995, 95, 537–558.
5. Corma, A.; Fornes, V.; Martin-Aranda, R. M.; Garcia, H. Zeolitas as base
catalysts, condensation of aldehydes with derivatives of malonic esters. J.
Appl. Catal. 1990, 59, 237.
6. Suzukamo, G.; Fukao, M.; Hibi, T.; Tanaka, K.; Chikaishi, K. In Proceedings of
the International Symposium on Acid–Base Catalysis. Sapporo, New York, 1988.
7. Corma, A.; Martin-Aranda, R. M. Application of solid base catalysts in the
preparation by condensation of kotones and malononitrile. Appl. Catal., A.
1993, 105, 271.
8. Corma, A.; Iborra, S.; Miquel, S.; Primo, J. Catalysts for the production
of fine chemicals and production of food emulsifiers, monoglycerides, by
glycerolysis of fats with solid base catalysts. J. Catal. 1998, 173, 315.
9. Veldurthy, B.; Clacens, J. M.; Figueras, F. Magnesium–Lanthanum mixed
metal oxide: A strong solid base for the Michael addition reaction. Adv.
Synth. Catal. 2005, 347, 767–771.
10. Xu, C.; Bartley, J. K.; Enache, D. I.; Knight, D. W.; Hutchings, G. J. High sur-
face area MgO as a highly effective heterogeneous base catalyst for michael addi-
tion and knoevenagel condensation reactions. Synthesis 2005, 10, 3468–3476.
11. Sheibani, H.; Saljoogi, A.; Bazgir, A. S. Three-component process for the
synthesis of 4-amino-5-pyrimidinecarbonitriles under thermal aqueous
conditions or microwave. Arkivoc 2008, 2, 115–123.
12. Sheibani, H.; Bernhardt, P. V.; Wentrup, C. Mesoionic 1,3-oxazinium olates:
Rearrangement to acylketenes and 3-azabicyclo[3.1.1]heptanetriones. J. Org.
Chem. 2005, 70, 5859–5861.
13. Sheibani, H.; Mosslemin, M. H.; Behzadi, S.; Islami, M. R.; Saidi, K. A
convenient one-pot synthesis of pyrano[3,2-c] quinolin-2,5(6H)-dione and
2H,5H-pyrano [3,2-c]chromene-2,5-dione derivatives. Synthesis 2006, 3, 435.
14. Sheibani, H.; Mosslemin, M. H.; Behzadi, S.; Islami, M. R.; Foroughi, H.;
Saidi, K. A simple and an efficient approach to the synthesis of a specific
tautomer of 1,3-thiazinones and 1,3-oxazinones. Arkivoc 2005, 15, 88–96.
15. Wang, S.; Ren, Z.; Cao, W.; Tong, W. The Knoevenagel condensation of
aromatic aldehydes with malononitrile of cyanoacetate in the presence
of CTMAB in water. Synth. Commun. 2001, 31, 673.
16. Rao, P. S.; Venkataratnam, R. V. Zinc chloride as a new catalyst for
Knoevenagel condensation. Tetrahedron Lett. 1991, 32, 5821.
17. Zabicky, J. The kinetics and mechanism of carbonyl–methylene condensation
reactions, Part XI: Stereochemistry of the products. J. Chem. Soc. 1961, 683–687.