Potassium exchanged layered zirconium phosphate as base catalyst in Knoevenagel condensation

Article abstract of DOI:10.1081/SCC-120002118

Potassium exchanged layered zirconium phosphate catalyzed Knoevenagel condensation of aldehydes and active methylene compounds gave the corresponding E configurated olefinic derivatives in solvent free conditions.

Full text of DOI:10.1081/SCC-120002118

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POTASSIUM EXCHANGED LAYERED ZIRCONIUM
PHOSPHATE AS BASE CATALYST IN KNOEVENAGEL
CONDENSATION
a
a
a
a
Massimo Curini , Francesco Epifano , Maria Carla Marcotullio , Ornelio Rosati
&
a
Andrè Tsadjout
a
Dipartimento di Chimica e Tecnologia del Farmaco, Sezione di Chimica Organica,
Facoltà di Farmacia, Università degli Studi, Via del Liceo, Perugia, I-06123, Italy
Published online: 16 Aug 2006.
To cite this article: Massimo Curini , Francesco Epifano , Maria Carla Marcotullio , Ornelio Rosati & Andr Tsadjout (2002)
POTASSIUM EXCHANGED LAYERED ZIRCONIUM PHOSPHATE AS BASE CATALYST IN KNOEVENAGEL CONDENSATION, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:3, 355-362
To link to this article: http://dx.doi.org/10.1081/SCC-120002118
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SYNTHETIC COMMUNICATIONS, 32(3), 355–362 (2002)
POTASSIUM EXCHANGED LAYERED
ZIRCONIUM PHOSPHATE AS BASE
CATALYST IN KNOEVENAGEL
CONDENSATION
Massimo Curini,* Francesco Epifano,
Maria Carla Marcotullio, Ornelio Rosati, and
Andre Tsadjout
`
Dipartimento di Chimica e Tecnologia del Farmaco,
Sezione di Chimica Organica, Facolta di Farmacia,
Universita degli Studi, Via del Liceo,
`
`
I-06123 Perugia, Italy
ABSTRACT
Potassium exchanged layered zirconium phosphate catalyzed
Knoevenagel condensation of aldehydes and active methylene
compounds gave the corresponding E configurated olefinic
derivatives in solvent free conditions.
In recent years, there has been increasing emphasis on the use of acidic
1
and basic solids in liquid phase organic synthesis.
There are many examples of achieving better yields, shorter reaction
times and even higher selectivities as a result of a reaction carried out with
heterogeneous catalysts under reaction conditions milder than those
employed in conventional homogeneous synthetic methods. In the last
*
Corresponding author.
3
55
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

ORDER
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3
56
CURINI ET AL.
2
years we reported that layered potassium exchanged zirconium phosphate
2
Zr(KPO ) is an excellent basic heterogeneous catalyst for Michael and
4
2
3
Henry reactions.
ꢁ
It is likely that the surface ꢀP-O group acts as a strong Bronsted base
capable of deprotonating the active methylene compound, with the conse-
quent formation of carboanion stabilized by potassium ion.
The Knoevenagel condensation has a wide application in the synthesis
4
5
6
of fine chemicals and is usually catalyzed by bases or acids in homoge-
neous liquid phase systems.
7
However, the use of heterogeneous catalysts (i.e. alumina, cadmium
8
9
10
11
12
13
iodide, sepiolite, zeolites, clays, hydrotalcites, and anionic resin )
has been reported. Recently the use of a N-bonded enolatorhenium(I) com-
1
plex, as a new solid phase Knoevenagel catalyst, has been described.
4
In continuation of our research to develop new methods for the
formation of carbon–carbon bonds using heterogeneous catalysts, we inves-
tigate the use of Zr(KPO ) in Knoevenagel condensations of aldehydes
4
2
with active methylene compounds, such as malononitrile, ethylcyanoacetate
and cyanoacetamide.
ꢂ
All the reactions (see experimental) were carried out at 60 C in
solvent-free conditions except the case of cyanoacetamide for which an
ꢂ
increase up to 100 C was necessary in order to obtain products in shorter
time and good yield.
In the presence of this catalyst, aliphatic and aromatic aldehydes react
with active methylene compounds in a short time and in solvent free con-
dition. It is important to note that in the case of a,b-unsaturated aldehydes
the reaction occurs without formation of the Michael-type addition adduct
(
Entry 5).
The reaction conditions and the corresponding yield of these three
active methylene species suggest their reactivity order is malono-
nitrile > ethylcyanoacetate > cyanoacetamide (e.g. Entries 1–6).
This solid base catalyst is a practical alternative to soluble bases in
Knoevenagel condensation with the following advantages: a) high catalytic
activity, b) solvent free conditions, c) mild reaction condition, d) simple
1
5
work up, e) recyclable nature of the catalyst and the preparation of

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ZIRCONIUM PHOSPHATE IN KNOEVENAGEL CONDENSATION
357
1
6
which does not require any particular skill. When ethylcyanoacetate and
cyanoacetamide were used as active methylene compounds the reaction
occured with the stereoselective formation of E configurated olefins. For
example in the case of the adduct obtained from 4-methoxybenzaldehyde
and ethylcyanoacetate (Entry 2) a small NOE effect was detected between
1
7
the olefinic proton and the methylene of the carboethoxy group.
Knoevenagel Condensation Reaction of Aldehydes with Malononitrile (a),
Ethylcyanoacetate (b) and Cyanoacetamide (c) Mediated by Zr(KPO
4 2
)

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3
58
CURINI ET AL.
In conclusion, the present communication offers a simple method for
the stereoselective preparation of olefins in good yield using Zr(KPO ) as
4
2
catalyst of Knoevenagel condensation of aldehydes and active methylene
compounds in solvent free conditions. The use of Zr(KPO ) is equally
4
2
effective or better than any reagent yet reported, therefore, the present
catalytic method should be useful in synthetic organic chemistry.
EXPERIMENTAL
1
H NMR spectra of CDCl solutions were recorded on a Bruker AC
3
200 spectrometer operating at 200.1 MHz in the Fourier transform mode.
GC analyses and MS spectra were carried out with an HP 5890 gaschro-
matograph (dimethyl silicon column 12.5 m) equipped with an HP 5971
Mass Selective Detector. Melting points were measured with Microthermal
apparatus and were uncorrected. Flash column chromatography was
performed on 0.040–0.063 mm (230–400 mesh ASTM) Merck silica gel.
Typical Procedure. A mixture of active methylene compound (1 mmol)
ꢂ
ꢂ
and Zr(KPO ) (50 mg) was stirred at 60 C under nitrogen (100 C in the
4
2
case of cyanoacetamide). After 15 min, aldehyde (1 mmol), was added and
the reaction mixture stirred for appropriate time (see table). The mixture
was then treated with dichloromethane (5 ml) and filtered. After evapora-
tion of solvent, the Knoevenagel adduct was purified by flash chromato-
graphy (hexane : EtOAc ¼ 10 : 1 Entries 1a,b–8a; CH Cl : EtOAc ¼ 8 : 2
2
2
Entries 1c–6c).
ꢂ
2-(Phenylmethylene)malononitrile (1a): white solid, mp. 102–103 C;
1
H-NMR d 7.4–7.6 (m, 3H, PhH), 7.66 (s, 1H, H-olefinic), 7.8–7.9 (m,
2H, PhH); MS m/z 156, 127, 103, 76. Calcd for C H N ; C, 77.91; H,
10 6 2
3
.92. Found: C, 77.92; H, 3.90.
Ethyl(E )-2-cyano-3-phenyl-2-propenoate(1b):whitesolid, mp. 54–55 C;
ꢂ
1
H-NMR d 8.22 (s, 1H: H-olefinic), 7.8–7.9 (m, 2H, PhH), 7.3–7.4 (m, 3H,
PhH), 4.25 (q, J ¼ 7 Hz, OCH CH ), 1.26 (t, J ¼ 7 Hz, 3H, OCH CH ). MS
2
3
2
3
m/z 203, 172, 128, 77. Anal. Calcd for C H NO ; C, 71.63; H, 5.51; N,
2
1
2
11
6
.96. Found: C, 71.61; H, 3.91; N, 6.97.
(
ꢂ
E )-2-Cyano-3-phenyl-2-propenamide (1c): white solid, mp. 82–84 C;
1
H-NMR d 6.7 (bs, 1H, NHCO), 6.9 (bs, 1H, NHCO), 7.4–7.5 (m, 3H,
PhH), 7.8 (m, 2H, PhH), 8.12 (s, 1H, H-olefinic); MS m/z 172, 155, 128,
1
02. Anal. Calcd for C H N O; C, 69.76; H, 4.68; N, 16.27. Found: C,
1
0
8
2
69.77; H, 4.67; N, 16.28.
2
-[(4-Methoxyphenyl)methylene]malononitrile (2a): yellow solid, mp.
ꢂ
1
1
12–114 C; H-NMR d 3.9 (s, 3H, OCH ), 6.9 (m, 2H, PhH), 7.6 (s, 1H,
3
H-olefinic), 7.9 (m, 2H, PhH). MS m/z 184, 169, 141, 114. Anal. Calcd

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ZIRCONIUM PHOSPHATE IN KNOEVENAGEL CONDENSATION
359
for C H N O; C, 71.73; H, 4.38; N, 15.21. Found: C, 71.71; H, 4.36;
1
1
8
2
N, 15.23.
Ethyl (E )-2-Cyano-3-(4-methoxyphenyl)-2-propenoate (2b): pale yellow
ꢂ
1
solid, mp. 87–88 C; H-NMR d 8.2 (s, 1H, H-olefinic), 8.0 (m, 2H, PhH),
7
1
.0 (m, 2H, PhH), 4.45 (q, J ¼ 7.1 Hz, 2H, OCH CH ), 3.9 (s, 3H, OCH ),
2
3
3
.41 (t, J ¼ 7.1 Hz, 3H, OCH CH ). MS m/z: 233, 186, 158, 89. Anal. Calcd
2 3
for C H NO ; C, 67.52 H, 5.67; N, 6.67. Found: C, 67.53; H, 5.68; N, 6.68.
1
3
13
3
(
E )-2-Cyano-3-(4-methoxyphenyl)-2-propenamide (2c): white solid,
ꢂ
1
mp. 210–212 C; H-NMR d 8.15 (s, 1H, PhH), 8.0 (m, 2H, PhH), 7.8 (bs,
H, NHCO), 7.5 (bs, 1H, NHCO), 7.1 (m, 2H, PhH), 3.87 (s, 3H, OCH3).
MS m/z 202, 187, 176, 107. Anal. Calcd for C H N O ; C, 65.34 H, 4.98;
1
1
1
10
2
2
N, 13.85. Found: C, 65.35; H, 4.96; N, 13.84.
-[4-(Dimethylamino)phenyl]methylenemalononitrile (3a): orange solid,
2
ꢂ
1
mp. 189–190 C; H-NMR d, 7.8 (m, 2H, PhH), 7.46 (s, 1H, H-olefinic),
.7 (m, 2H, PhH), 3.15 (s, 6H, N(CH ) ). MS m/z 198, 153, 126, 84. Anal.
Calcd for C H N ; C, 73.07; H, 5.62; N, 21.30. Found: C, 73.06; H, 5.61;
6
3
2
1
2
11
3
N, 21.31.
Ethyl (E)-2-Cyano-3-[4-(dimethylamino)phenyl]-2-propenoate (3b): yellow
ꢂ
1
solid, mp. 129–131 C; H-NMR d 8.1 (s, 1H, H-olefinic), 7.8–7.9 (m, 2H,
PhH), 6.6–6.7 (m, 2H, PhH), 4.33 (q, J ¼ 7 Hz, 2H, OCH CH ), 3.1 (s, 6H,
2
3
N(CH ) ), 1.37 (t, J ¼ 7 Hz, 3H, OCH CH ). MS m/z 244, 215, 199, 171.
3
2
2
3
Anal. Calcd for C H N O ; C, 68.83; H, 6.60; N, 11.47. Found: C, 68.84;
1
4
16
2
2
H, 6.62; N, 11.45.
E)-2-Cyano-3-[4-(dimethylamino)phenyl]-2-propenamide (3c): pale yellow
(
ꢂ
1
solid, mp. 213–214 C; H-NMR d 8.11 (s, 1H, H-olefinic), 7.9 (m, 2H, PhH),
.9 (bs, 1H, NHCO), 6.8 (bs, 1H, NHCO), 6.7 (m, 2H, PhH), 3.10 (s, 6H,
N(CH ) ). MS m/z 217, 148, 60. Anal. Calcd for C H N O; C, 66.96; H,
6
3
2
12 13
3
6
.09; N, 19.52. Found: C, 66.98; H, 6.10; N, 19.51.
-[(2-Methylphenyl)methylene]malononitrile (4a): white solid, mp.
05–106 C; H-NMR d 8.11 (s, 1H, H-olefinic), 8.09 (d, J ¼ 7.2 Hz, 1H,
2
ꢂ
1
1
PhH), 7.6–7.3 (m, 3H, PhH), 2.45 (s, 3H, CH ). MS m/z 168, 141, 114.
3
Anal. Calcd for C H N ; C, 78.55; H, 4.79; N, 16.66. Found: C, 78.54;
2
1
1
8
H, 4.77; N, 16.67.
Ethyl (2E,4E )-2-Cyano-5-phenyl-2,4-pentadienoate (4b): white solid,
ꢂ
1
mp. 56–57 C; H-NMR d 8.60 (s, 1H, H-olefinic), 8.16 (d, J ¼ 7.3 Hz, 1H,
PhH), 7.5–7.3 (m, 3H, PhH), 4.39 (q, J ¼ 6.3 Hz, 2H, OCH CH ), 2.47
2
3
(
1
s, 3H, CH ), 1.42 (t, J ¼ 6.3 Hz, 3H, OCH CH ). MS m/z 215, 170, 143,
3
2
3
15. Anal. Calcd for C H NO ; C, 72.54; H, 6.09; N, 6.51. Found:
13 13 2
C, 72.56; H, 6.08; N, 6.53.
2Z,4E )-2-Cyano-5-phenyl-2,4-pentadienamide (4c): white solid, mp.
(
ꢂ
1
1
55–158 C; H-NMR d 8.68 (s, 1H, H-olefinic), 8.06 (d, J ¼ 7.7 Hz, 1H,
PhH), 7.5–7.3 (m, 3H, PhH), 6.3 (bs, 1H, NH ), 5.8 (bs, 1H, NH ), 2.49
a
b

ORDER
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3
60
CURINI ET AL.
(
s, 3H, CH ). Ms m/z 186, 171, 143, 115. Anal. Calcd for C H N O; C,
3
11 10
2
70.95; H, 5.41; N, 15.04. Found: C, 70.96; H, 5.43; N, 5.40.
2
-[(E )-3-Phenyl-2-propenylidene]malononitrile (5a): orange solid, mp.
ꢂ
1
1
14–115 C; H-NMR d, 8.3 (d, J ¼ 10 Hz, 1H, H-olefinic) 7.8 (m, 2H,
PhH), 7.63 (d, J ¼ 14.1 Hz, 1H, H-olefinic), 7.4–7.5 (m, 3H, PhH), 7.25
dd, J ¼ 10, 14.1 Hz, 1H, H-olefinic). MS m/z 182, 153, 115, 63. Anal.
Calcd for C H N ; C, 79.98; H, 4.47; N, 15.54. Found: C, 79.97; H, 4.48;
(
1
2
8
2
N, 15.55.
Ethyl (2E,4E )-2-Cyano-5-phenyl-2,4-pentadienoate (5b): yellow solid,
ꢂ
1
mp. 109–110 C; H-NMR d 7.9 (m, 1H, H-olefinic), 7.5 (m, 2H, PhH),
.3 (m, 3H, PhH), 7.2 (m, 2H, H-olefinics), 4.25 (q, J ¼ 7.1 Hz, 3H,
7
OCH CH ), 1.3 (t, J ¼ 7.1 Hz, 3H, OCH CH ). MS m/z 227, 199, 171,
2
3
2
3
154, 127. Anal. Calcd for C H NO ; C, 73.99; H, 5.77; N, 6.16. Found:
C, 73.97; H, 5.78; N, 6.18.
14 13 2
(
2Z,4E )-2-Cyano-5-phenyl-2,4-pentadienamide (5c): yellow solid, mp.
ꢂ
1
1
35–137 C; H-NMR d, 7.91 (d, 1H: H-olefinic), 7.4 (m, 2H, PhH), 7.0–7.3
(
m, 5H, olefinic þ PhH), 6.2 (bs, 1H, NHCO), 6.0 (bs, 1H, NHCO). MS m/z
198, 170, 154, 117. Anal. Calcd for C H N O; C, 72.71; H, 5.08; N, 14.13.
Found: C, 72.70; H, 5.06; N, 14.12.
12 10 2
1
2
-(Cyclohexylmethylene)malononitrile (6a): yellow oil; H-NMR d,
.08 (d, J ¼ 10 Hz, 1H, H-olefinic) 2.6 (m, 1H, -CH-), 1.6–1.8 (m, 4H,
CH -), 1.1–1.4 (m, 6H, -CH -). MS m/z 160, 145, 132, 118, 105. Anal.
7
-
2
2
Calcd for C H N ; C, 74,97; H, 7.55; N, 17.48. Found: C, 74.99; H,
1
0
12
2
7.56; N, 17.46.
Ethyl (E )-2-Cyano-3-cyclohexyl-2-propenoate (6b): colorless oil;
H-NMR d 7.46 (d, J ¼ 9.8 Hz, 1H, H-olefinic), 4.3 (q, J ¼ 7 Hz, 2H,
1
OCH CH ), 2.7 (m, 1H, -CH-), 1.8 (m, 4H, -CH -), 1.33 (t, J ¼ 7 Hz, 3H,
2
3
2
OCH CH ), 1.2–1.4 (m, 6H, -CH -). MS m/z 207, 179, 161, 134, 126.
2
3
2
Anal. Calcd for C H NO ; C, 69.54; H, 8.27; N, 6.76. Found: C, 69.55;
1
2
17
2
H, 8.29; N, 6.74.
E )-2-Cyano-3-cyclohexyl-2-propenamide (6c): white solid, mp. 103–
(
ꢂ
1
1
05 C; H-NMR, 7.55 (d, J ¼ 9.8 Hz, 1H, H-olefinic) d, 6.1 (bs, 1H,
NHCO), 5.8 (bs, 1H, NHCO), 2.7 (m, 1H, -CH-), 1.7–1.9 (m, 4H, -CH -),
2
1.2–1.4 (m, 6H, -CH -). MS m/z 178, 161, 134, 121. Anal. Calcd for
C H N O; C, 67.39; H, 7.92; N, 15.72. Found: C, 67.40; H, 7,94; N, 15.71.
2
1
0
14
2
1
2-(10-Undecenylidene)malononitrile (7a): colorless oil; H-NMR d 7.32
(
t, J ¼ 7.9 Hz, 1H, H-1), 5.8 (m, 1H, H-10), 5.1–4.5 (m, 2H, H-11), 2.59 (q,
J ¼ 7.9 Hz, 2H, H-2), 2.0 (m, 2H, H-9), 1.6 (m, 2H, H-3), 1.5–1.2 (m, 10H,
H-4,5,6,7,8). MS m/z 216, 201, 187, 173. Anal. Calcd for C H N ; C, 77.73;
1
4
20
2
H, 9.32; N, 12.95. Found: C, 77.71; H, 9.31; N, 12.97.
1
Ethyl (2E )-2-Cyano-2,12-tridecadienoate (7b): colorless oil; H-NMR
d 7.66 (t, J ¼ 7.9 Hz, 1H, H-1), 5.8 (m, 1H, H-10), 5.1–4.3 (m, 2H, H-11),

ORDER
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ZIRCONIUM PHOSPHATE IN KNOEVENAGEL CONDENSATION
361
4
2
.32 (q, J ¼ 6.8 Hz, 2H, OCH CH ), 2.57 (q, J ¼ 7.9 Hz, 2H, H-2), 2.0 (m,
2
3
H, H-9), 1.6 (m, 2H, H-3), 1.5–1.1 (m, 13H, H-4,5,6,7,8 and OCH CH ).
2
3
MS m/z 263, 248, 234, 190, 148. Anal. Calcd for C H NO ; C, 72.97; H,
25
1
6
2
9
.57; N, 5.32. Found: C, 72.96; H, 9.55; N, 5.34.
-Hexylidenemalononitrile (8a): colorless oil; H-NMR d 7.38 (t,
J ¼ 8.4 Hz, 1H, H-1), 2.63(q, J ¼ 8.4 Hz, 1H, H-2), 1.6 (m, 2H, H-3),
.4 (m, 4H, H-4,5), 0.9 (m, 3H, -CH ). MS m/z 148, 133, 119, 94. Anal.
1
2
1
3
Calcd for C H N ; C, 72.94; H, 8.16; N, 18.90. Found: C, 72.93; H, 8.14;
9
12
2
N, 18.92.
1
Ethyl (E )-2-Cyano-2-octenoate (8b): colorless oil; H-NMR d 7.68 (t,
J ¼ 7.9 Hz, H-1), 4.35 (q, J ¼ 6.3 Hz, 2H, OCH CH ), 2.58 (q, J ¼ 7.9, 2H,
2
3
H-2), 1.6 (m, 2H, H-3), 1.5–1.3 (m, H-4,5 and OCH CH ), 1.0 (m, 3H,
2
3
-
CH ). MS m/z 195, 166, 141, 126, 113. Anal. Calcd for C H NO ; C,
3
11 17
2
67.66; H, 8.78; N, 7.17. Found: C, 67.68; H, 8.79; N, 7.15.
ACKNOWLEDGMENT
This work was supported by M.U.R.S.T. ‘‘Progetto Chimica dei
Composti Organici di Interesse Biologico’’, and the C.N.R. (Rome) is grate-
fully acknowledged. We thank Prof. U. Costantino for helpfull discussions.
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2. Climent, M.J.; Corma, A.; Iborra, S. J. Catal. 1995, 151, 60; Tichit, D.;
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Bartolini, D.; Garrone, E. ibid 1995, 151, 50; Corma, A.; Fornes, V.;
Martin-Aranda, R.M.; Rey, F. ibid 1942, 134, 58; Kantam, M.L.;
Choudary, B.M.; Reddy, Ch.V.; Rao, K.K.; Figueras, F. Chem.
Commun. 1988, 1033.
1
1
3. Richardhein, W.; Melvin, J. J. Org. Chem. 1961, 26, 4874.
4. Simpan, J.; Rathbone, D.L.; Billington, D.C. Tetrahedron Lett. 1999,
40, 7031.
1
5. The process 1a has been repeated five times, through the catalyst
ꢂ
washed with dichloromethane and dried at 180 C, with the following
yields: 90, 91, 89, 90 and 88%.
1
1
6. For the preparation of catalyst see Refs 2 and 3.
7. Sang-Yun, K.; Pan-Suk, K.; Tae-Woo, K. Synth. Commun. 1997,
27, 533.
Received in the USA March 19, 2001

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