Fe3+-exchanged fluorotetrasilicic mica as an active and reusable catalyst for Michael reaction

Article abstract of DOI:10.1016/j.tetlet.2003.08.048

Fe³⁺-exchanged fluorotetrasilicic mica acts as a highly effective and reusable catalyst for the solventless Michael reaction of β-ketoesters with vinyl ketones under mild condition. The immobilized catalyst shows higher activity than homogeneou

Full text of DOI:10.1016/j.tetlet.2003.08.048

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 7421–7424
3+
Fe -exchanged fluorotetrasilicic mica as an active and reusable
catalyst for Michael reaction
a,
b
a
b
b
Ken-ichi Shimizu, * Masato Miyagi, Toshiki Kan-no, Tatsuya Kodama and Yoshie Kitayama
a
Graduate School of Science and Technology, Niigata University, Ikarashi-2, Niigata 950-2181, Japan
b
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Niigata University, Ikarashi-2, Niigata 950-2181,
Japan
Received 8 July 2003; accepted 11 August 2003
3+
Abstract—Fe -exchanged fluorotetrasilicic mica acts as a highly effective and reusable catalyst for the solventless Michael
reaction of b-ketoesters with vinyl ketones under mild condition. The immobilized catalyst shows higher activity than
3+
homogeneous Fe catalysts, FeCl ·6H O and Fe(NO ) ·9H O.
3
2
3 3
2
©
2003 Elsevier Ltd. All rights reserved.
5
b
The Michael reaction is among the most useful CꢀC
bond forming reaction and has wide applications in the
synthesis of fine chemicals. Although base catalysis of
the Michael reaction is commonly known as a very
of Yb(OTf) during the work-up procedure. The use
3
of clays as catalyst supports has received considerable
attention because of their ability to immobilize reactive
metal ions in the interlayer by the strong electrostatic
interaction. In this paper, we have developed Fe -
exchanged clay (Fe-clay) as a recyclable and highly
efficient heterogeneous catalyst for the Michael reaction
of b-ketoesters with vinyl ketones. The catalytic behav-
ior as well as the recycling characteristics of Fe-clay is
presented to exemplify the effectiveness of this catalytic
system.
1
6
3+
efficient and high-yielding process, the strongly basic
conditions is often a limiting factor since they can lead
to a number of side and subsequent reactions such as
ester solvolysis. Recently, Lewis acids, such as transi-
tion metal or lanthanide complexes, have been devel-
oped as chemoselective and active catalysts for the
Michael reaction under neutral and mild reaction con-
2
–5
ditions. Christoffers reported that FeCl ·6H O cata-
3
2
3+
lyzes the solventless Michael reaction of 1,3-dicarbonyl
compounds with enones at room temperature with
Fe -catalysts dispersed on various inorganic supports
were prepared as follows. FeCl ·6H O supported on
silica gel and Al O (Fe-SiO and Fe-Al O ) were pre-
7
3
2
3
excellent yields and selectivity. Regarding industrial
2 3 2 2 3
applications, however, homogeneous catalyst is gener-
ally connected with the problems of catalyst-product
separation and wasted inorganics which are too difficult
to reuse. To overcome these problems, immobilization
pared by mixing the supports with aqueous solution of
FeCl ·6H O, followed by a complete removal of the
3
2
3+
solvent at 353 K. Fe-clay samples and Fe -exchanged
NaY zeolite (Fe-NaY) were prepared by exchanging the
supports with aqueous solution of FeCl ·6H O at 298
4
of Lewis acid catalysts on polymer or inorganic
3
2
5
supports have been attempted. However, the activity
K for 3 h, followed by centrifuging and washing with
deionized water, and by drying in vacuo at 298 K.
of the recycled polymer supported catalyst for the
Michael reaction was considerably decreased because of
3+
Fe -exchanged fluorotetrasilicic mica from aqueous
solution of Fe(NO ) ·9H O was also prepared and
4b
a significant metal leaching. Yb(OTf) supported on
3
3 3
2
silica gel was shown to be a convenient catalyst for
Michael reaction, although the activity of recovered
catalyst was considerably reduced due to complexation
named as Fe-mica-N.
3+
Various Fe catalysts were first tested in the model
reaction of 1 with methyl vinyl ketone (MVK) 2 (Table
1
). The reaction was carried out by stirring the reaction
Keywords: Michael reaction; fluorotetrasilicic mica; Fe3+-exchanged
clay.
mixture containing b-ketoester 1 (5 mmol), MVK (6
3+
mmol) and Fe catalysts (0.05 mmol of Fe) at room
temperature in air (in the presence of moisture). The
solid catalysts were used without any pre-treatment.
*
Corresponding author. Tel.: +81-25-262-6777; fax +81-25-262-7010;
e-mail: kshimizu@eng.niigata-u.ac.jp
0
040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2003.08.048

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K. Shimizu et al. / Tetrahedron Letters 44 (2003) 7421–7424
Table 1. Michael reaction of b-ketoester 1 with MVK
Entry
Catalysts
Yield/%a
Fe leaching/%
b
b
b
b
1
2
3
4
5
6
7
8
Fe-mica
Fe-mica-N
Fe-mont
Fe-SiO2
97, 99 , 99 , 99
91
0.19
0.21
0.52
33
16
8.3
–
b
b
93, 99 , 99 , 99
99
c
Fe-Al O
13
23
2
3
c
Fe-NaY
FeCl ·6H O
99
99
3
2
Fe(NO ) ·9H O
–
3
3
2
a
Isolated yields.
b
c
Yields in the first, second, third and fourth repeated reuses of the same catalyst.
Yields determined by H NMR using internal standard method.
1
After stirring for 20 h, ethyl acetate (5 mL) was added
to the reaction mixture, and the solid catalyst was
removed by a centrifugation. Fe-clay catalysts (Fe-
mica, Fe-mica-N and Fe-mont) gave high yields com-
parable to FeCl ·6H O (a homogeneous catalyst); full
3
2
conversion of 1 and almost quantitative yield of the
product 3 were observed. As reported by Christoffers
3
for FeCl ·6H O catalyst, no side products were
3
2
1
detected by TLC, GC and H NMR analyses. It should
be noted that, for Fe-clay catalysts, evaporation after
the centrifugation directly gave a Michael adduct 3.
ICP analysis of filtrate after the reaction (Table 1)
shows that metal leaching of clay supported catalysts
was significantly low. A possible contribution of homo-
geneous catalysis was excluded as the following experi-
ment. When the Fe-mica catalyst was removed at an
early stage of the reaction (t=30 min, 40% yield), the
reaction did not proceed further, confirming that the
observed catalysis of Fe-mica is truly heterogeneous in
Figure 1. Plot of GC yield versus time for the Michael
reaction of b-ketoester 1 with MVK 2 by various catalysts;
(
ꢀ) Fe-mica, (2) Fe-mica-N, (ꢁ) Fe-mont, (ꢂ)
FeCl ·6H O, (") Fe(NO ) ·9H O.
3
2
3 3
2
3+
mica-supported Fe catalysts showed higher activity
than corresponding homogeneous catalysts. Fe-mica
was the most effective among the catalyst tested, and
the reaction proceeded smoothly to give a quantitative
yield after 6 h. It is noteworthy that the initial rate of
product formation by Fe-mica-N was about 20 times
8
nature. After the first run, reusability of the Fe-mica
and Fe-mont catalysts was tested. The catalyst can be
easily separated from the reaction mixture by a simple
centrifugation and can be recycled at least three times
keeping almost quantitative yield without any reactiva-
tion-treatment. The Fe-mica catalyst is also effective in
the presence of solvent (diethyl ether, 1 mL); Michael
adduct (94%) was obtained for the reaction of 1 and
MVK with 1 mol% of the catalyst.
10
higher than that by Fe(NO ) ·9H O. XRD analysis
3
3
2
showed that the interlayer distance can be expanded to
1
1
3+
8
.4±0.5 A
,
during the reaction, indicating that Fe
cation in the interlayer is available as a catalyst. Hence,
3+
the enhancement of the activity by Fe -immobilization
in fluorotetrasilicic mica may be due to the use of the
interlayer for the reaction.
Although Fe-SiO gave a high yield, a large amount of
2
supported Fe (33%) was leached from the solid. This
indicates that the activity of Fe-SiO should be due to
homogeneous catalysis of the leached Fe in solution.
Several examples of Fe-mica catalyzed Michael reac-
tions are summarized in Table 2. Fe-mica was generally
very effective in the reaction of various Michael donors
with methyl vinyl ketone or ethyl vinyl ketone. After
stirring for 20 h at room temperature, Michael adducts
were obtained in high yields using only 1 mol% of the
catalyst without using solvent. Ester hydrolysis as a
side-reaction was negligible even for methyl ester (entry
2) in the presence of moisture. Use of ethyl 3-oxobu-
2
3
+
With Fe-Al O and Fe-NaY, poor yields and significant
2
3
3
+
Fe leaching were observed.
The profiles of the reaction were obtained by GC
9
analysis using 0.1 mol% of each catalyst. The results
for Fe-mica, Fe-mica-N, Fe-mont, FeCl ·6H O and
3
2
Fe(NO ) ·9H O are compared in Figure 1. Clearly, the
3
3
2

K. Shimizu et al. / Tetrahedron Letters 44 (2003) 7421–7424
7423
a
Table 2. Fe-mica catalyzed Michael reactions
a
b
c
Conditions are the same as in Table 1.
Isolated yields.
Yields determined by 1H NMR using internal standard method.
tanate as a Michael donor resulted in a moderate yields
41%). No Michael adduct was obtained for the reac-
2. (a) Nelson, J. H.; Howells, P. N.; DeLullo, G. C.; Lan-
den, G. L.; Henry, R. A. J. Org. Chem. 1980, 45, 1246;
(b) Keller, E.; Feringa, B. L. Tetrahedron Lett. 1996, 37,
1879; (c) Mori, Y.; Kakumoto, K.; Manabe, K.;
Kobayashi, S. Tetrahedron Lett. 2000, 41, 3107.
(
tion of diethyl malonate with MVK by Fe-mica (3
mol%). When acrylonitrile, ethyl acrylate, 2-cyclopen-
ten-1-one, 2-cyclohexen-1-one or 4-phenyl-3-buten-2-
one were used for the reaction with b-ketoester 1 by
Fe-mica (3 mol%), the Michael reaction did not
proceed.
3. (a) Christoffers, J. Eur. J. Org. Chem. 1998, 1259; (b)
Christoffers, J. Chem. Commun. 1997, 943.
4
. (a) Feri, C. P.; Chan, T. H. Synthesis 1982, 467; (b)
Mastrorilli, P.; Nobile, C. F.; Suranna, G. P. J. Mol.
Catal. A 1995, 103, 23.
3+
In conclusion, we have succeeded in developing Fe -
exchanged fluorotetrasilicic mica as a highly effective
heterogeneous catalyst for the Michael reactions of
b-ketoester with vinyl ketones. This novel catalyst pro-
vides a clean and convenient alternative for the Michael
reaction in view of the following advantages. The reac-
tion proceeds smoothly and selectively in the presence
of moisture under solventless condition, producing
Michael adducts in high yield at room temperature.
The catalyst is stable, reusable and a non-polluting
solid that offers easy handling and ready work-up.
5
. (a) Laszlo, P.; Montaufier, M.-T.; Randrimahefa, S. L.
Tetrahedron Lett. 1990, 31, 4867; (b) Kotsuki, H.;
Arimura, K. Tetrahedron Lett. 1997, 38, 7583.
6
. (a) Izumi, Y.; Onaka, M. Adv. Catal. 1992, 38, 244; (b)
Morikawa, Y. Adv. Catal. 1993, 39, 302; (c) Tateiwa, J.;
Nishimura, T.; Horiuchi, H.; Uemura, S. J. Chem. Soc.,
Perkin Trans. 1 1994, 3367; (d) Choudary, B. M.; Chow-
dari, N. S.; Kantam, M. L. Tetrahedron 2000, 56, 7291;
(
e) Ebitani, K.; Ide, M.; Mitsudome, T.; Mizugaki, T.;
Kiyotomi, K. Chem. Commun. 2002, 690.
7
. Following inorganic supports were used: Na-fluorotetra-
silicic mica (Na-mica) with ideal formula of
NaMg2.5Si O F (COOP Chemicals Co. Ltd., Somasif
References
4
10 2
1
. Bergman, E. D.; Ginshburg, D.; Pappo, R. Org. React.
ME-100), synthetic Na-montmorillonite (Na-mont)
[Kunimine Co. Ltd., Kunipia F, (Na0.13Mg0.08Ca0.01)-
1
959, 10, 179.

7
424
K. Shimizu et al. / Tetrahedron Letters 44 (2003) 7421–7424
3+
2+
(
Al1.44Mg0.32Fe 0.09Fe 0.02)(Si3.83Al0.17)O (OH) ·nH O],
using larger amount of the catalyst (1 mol%) after 20
10
2
2
SiO2 (JRC-SIO-8, a reference catalyst of the Catalysis
Society of Japan), Al O (JRC-ALO-8) and NaY zeolite
h. However, FeCl ·6H O showed higher reaction rate
3
2
than Fe(NO ) ·9H O using smaller amount of the cata-
2
3
3 3
2
(
JRC-Z-Y 5.6, SiO /Al O =5.6). ICP analysis showed
lyst (0.1 mol%).
2
2
3
that Fe contents of Fe-mica, Fe-mica-N, Fe-mont, Fe-
SiO , Fe-Al O and Fe-NaY are 2.3, 1.6, 1.4, 6.1, 4.8
11. From XRD analysis, the basal spacings (d001) of Fe-
mica and Fe-mica-N were estimated to be about
2
2
3
and 2.1 wt%, respectively.
. Sheldon, R. A.; Wallau, M.; Arends, I. W. C. E.;
Schuchardt, U. Acc. Chem. Res. 1998, 31, 485.
12.7 A, and these values were increased to 17.5±0.5
,
8
A when these catalysts were soaked with b-ketoester 1
,
or the reaction mixture containing 1 and MVK. This
9. Progress of the reaction was monitored by GC analysis
of aliquots using n-dodecane as internal standard.
indicates that the interlayer space of Fe-clay is
expanded during the Michael reaction, and hence Fe
3
+
1
0. As reported by Christoffers, the catalytic activity of
in the interlayer is available as a catalyst for the reac-
tion.
FeCl ·6H O was the same as that of Fe(NO ) ·9H O
3
2
3 3
2