Heterogeneous amine catalyst grafted on amorphous silica: An effective organocatalyst for microwave-promoted Michael reaction of 1,3-dicarbonyl compounds in water

Article abstract of DOI:10.1246/cl.2006.926

Michael addition of a 1,3-dicarbonyl compound to an α,β- unsaturated carbonyl compound was effectively catalyzed by heterogeneous N,N-diethylaminopropylated silica gel (NDEAP) in water under microwave heating. The reaction condition was mild, practical, a

Full text of DOI:10.1246/cl.2006.926

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Chemistry Letters Vol.35, No.8 (2006)
Heterogeneous Amine Catalyst Grafted on Amorphous Silica: An Effective Organocatalyst
for Microwave-promoted Michael Reaction of 1,3-Dicarbonyl Compounds in Water
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Hisahiro Hagiwara, Sachiyo Inotsume, Masakazu Fukushima, Takashi Hoshi, and Toshio Suzuki
Graduate School of Science and Technology, Niigata University, 8050, 2-Nocho, Ikarashi, Niigata 950-2181
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2
Faculty of Engineering, Niigata University, 8050, 2-Nocho, Ikarashi, Niigata 950-2181
(Received June 9, 2006; CL-060666; E-mail: hagiwara@gs.niigata-u.ac.jp)
Michael addition of a 1,3-dicarbonyl compound to an ꢀ,ꢁ-
unsaturated carbonyl compound was effectively catalyzed by
heterogeneous N,N-diethylaminopropylated silica gel (NDEAP)
in water under microwave heating. The reaction condition was
mild, practical, and environmentally benign. The sustainable
nature of the catalyst was exemplified by re-use up to 5 times.
Development of a sustainable and environmentally benign
process is of prime interest in production of organic com-
1
pounds, in which a catalytic reaction in environmentally benign
reaction media is desired for such purpose. A heterogeneous cat-
alyst is better than a homogeneous catalyst due to its easy recov-
ery and recycle-use. An organomolecular catalyst is superior to
an organometallic catalyst, due to flexible design, availability in-
dependent of natural resource, and avoidance of pollution caused
by use of heavy metal. One drawback of the organomolecular
catalyst is its instability, which might be solved by supporting
the organocatalytic moiety on solid surface such as silica gel.
From such standpoint, we recently disclosed 1,2- or 1,4-nu-
cleophilic reactions of carbonyl compounds in environmentally
friendly media such as an ionic liquid, super-critical carbon di-
Scheme 1. Microwave-promoted Michael addition catalyzed
by amine grafted on silica.
a
Table 1. Investigation of effective catalyst
Yield/%b
Entry
Catalyst
Amount (equiv.)
1
2
3
4
5
6
7
8
—
Silica gel
NAP
NMAP
NEDAP
NDEAP
NDEAP
NDEAP
—
—
17
11
55
48
29
72
72
50
0.1
0.1
0.1
0.1
0.05
0.01
2
f
oxide or water, employing propylamine grafted on silica gel.
The reaction conditions were mild enough to apply to substrates
2
having acid- or base-sensitive substituents.
aThe reaction was carried out with ethyl 2-oxocyclopentane-
carboxylate (1) and 3-buten-2-one (2) (1.5 equiv.) and the
catalyst (0.05 equiv.) in water under microwave (500-W) ir-
radiation for 2 min. The temperature was ramped from room
As a part of our ongoing program directed toward the devel-
opment of green organic reactions, we investigated 1,4-addition
of a 1,3-dicarbonyl compound to an ꢀ,ꢁ-unsaturated carbonyl
3
compound in water catalyzed by amine grafted on silica gel
ꢀ
temperature to 100 C, which was monitored by a radiation
thermometer. After the reaction, the product was triturated
as a heterogeneous organomolecular catalyst. Water has many
advantages from its ability to accelerate a bimolecular reaction
due to high cohesive energy density and dielectric constant, safe-
b
with ethyl acetate. Yields are for isolated pure products
based on 2-oxocyclopentanecarboxylate (1).
4
ty based on non-flammability and non-toxicity, and economy.
Since the reaction is carried out in a tri-phasic system due to
low solubility of organic substrates, we focused on internal heat-
heterogeneous amine catalysts investigated, N,N-diethylamino-
f
2
propylated silica gel (NDEAP) provided the best result
(Table 1, Entries 6 and 7).
5
ing by microwave irradiation, in which water is advantageous
due to relatively high loss factor (tan ꢂ) for efficient heating.5a
Although there are several attempts for Michael reaction em-
ploying a polymer-bound organomolecular catalyst, there is
no precedent to our knowledge of reaction catalyzed by a hetero-
An examination on the effect of the solvent is compiled in
Table 2. In THF or xylene, a large amount of substrate 1 was re-
covered (Table 2, Entry 2 or 4), though the reaction proceeded
6
Table 2. Effect of solventa
geneous organomolecular catalyst grafted on silica gel, except
7
1,4-addition of nitroalkane.
The optimum catalyst was examined at first employing the
Entry
Solvent
Yield/%
1
2
—
THF
33
2
reaction of ethyl 2-oxocyclopentanecarboxylate (1) and 3-but-
en-2-one (2) (Scheme 1 and Table 1) in water under microwave
heating by a multimode 500-W domestic oven. The temperature
3
4
5
PEG
Xylene
H2O
0
7
72
ꢀ
was ramped for 2 min from room temperature to 100 C, which
was monitored by a radiation thermometer. Without a catalyst,
the reaction resulted in recovery of 1 (Table 1, Entry 1). Addition
of silica gel also gave the same result (Table 1, Entry 2). Among
a
The reaction was carried out in the same manner as
in Table 1.
Copyright Ó 2006 The Chemical Society of Japan

Chemistry Letters Vol.35, No.8 (2006)
927
In summary, we have developed a new protocol for Michael
addition of 1,3-dicarbonyl compounds catalyzed by a clean cat-
alyst (NDEAP) in a clean medium (water) under clean activation
8
(
microwave heating). The catalyst was effectively recycled.
The present reaction is mild, practical, environmentally benign,
and sustainable, which would be useful for large-scale prepara-
tion.
This work was partially supported by Grant-in-Aid for
Scientific Research on Priority Areas (No. 17035031 for H.
H.) from The Ministry of Education, Culture, Sports, Science
and Technology (MEXT).
References and Notes
1
P. T. Anastas, J. C. Warner, Green Chemistry: Theory and Practice,
Oxford University Press, 1998.
a) K. Isobe, T. Hoshi, T. Suzuki, H. Hagiwara, Mol. Diversity 2005,
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, 317. b) H. Hagiwara, J. Hamaya, T. Hoshi, C. Yokoyama, Tetra-
hedron Lett. 2005, 46, 393. c) M. Fukushima, S. Endou, T. Hoshi,
T. Suzuki, H. Hagiwara, Tetrahedron Lett. 2005, 46, 3287. d) H.
Hagiwara, A. Koseki, K. Isobe, K. Shimizu, T. Hoshi, T. Suzuki,
Synlett 2004, 2188. e) K. Shimizu, H. Suzuki, T. Kodama, H.
Hagiwara, Y. Kitayama, Stud. Surf. Sci. Catal. 2003, 145, 145.
f) J. Hamaya, T. Suzuki, T. Hoshi, K. Shimizu, Y. Kitayama, H.
Hagiwara, Synlett 2003, 873. g) K. Shimizu, E. Hayashi, T.
Inokuchi, T. Kodama, H. Hagiwara, Y. Kitayama, Tetrahedron Lett.
Figure 1. Michael additions with various Michael donors and
acceptors catalyzed by 0.1 equiv. of NDEAP.
without solvent (Table 2, Entry 1). The reaction in polyethylene-
glycol (PEG) having higher tan ꢂ than that of water, resulted in
decomposition and did not recover 1 probably due to overheat-
ing (Table 2, Entry 3). Among solvents investigated, water
was the best medium for the present reaction (Table 2, Entry 5).
The optimized reaction condition (Table 1, Entry 7) was ap-
plied to a variety of Michael donors. Different from the prelimi-
nary experiments in Tables 1 and 2, the power of microwave ir-
radiation was reduced to 100-W in order to prevent overheating.
2
002, 43, 9073. h) H. Hagiwara, S. Tsuji, T. Okabe, T. Hoshi, T.
Suzuki, H. Suzuki, K. Shimizu, Y. Kitayama, Green Chem. 2002,
4, 461. i) K. Shimizu, H. Suzuki, E. Hayashi, T. Kodama, Y.
Tsuchiya, H. Hagiwara, Y. Kitayama, Chem. Commun. 2002, 1068.
a) E. Keller, B. L. Feringa, Tetrahedron Lett. 1996, 37, 1879. b) H.
Kotsuki, K. Arimura, Tetrahedron Lett. 1997, 38, 7583. c) Y. Mori,
K. Kakumoto, K. Manabe, S. Kobayashi, Tetrahedron Lett. 2000,
3
4
ꢀ
The reaction temperature was ramped to 80 C quickly and
4
1, 3107.
maintained at the temperature until termination of the reaction.
Actually, the yield was improved from 72 (Table 1, Entries 6
and 7) to 92% (Table 3, Entry 1). Satisfactory Michael additions
with a variety of cyclic and acyclic 1,3-dicarbonyl compounds
are compiled in Figure 1. Microwave heating is superior to con-
ventional heating in an oil bath as shown in the reaction with
methyl acrylate (Figure 1).
After the reaction, the product was triturated with ethyl ace-
tate and the suspension of NDEAP in water could be easily recy-
cled at least four times as shown in Table 3. A certain amount of
decrease (Table 3, Entry 4) of the catalytic activity was retrieved
after washing the NDEAP with dilute aqueous sodium carbonate
a) C.-J. Li, Chem. Rev. 2005, 105, 3095. b) E. K. Wilson, Chem.
Eng. News 2005, No. 30, 49. c) U. M. Lindstrom, Chem. Rev.
2
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J. Oda, Bull. Chem. Soc. Jpn. 1987, 60, 4121. c) R. Alvarez,
M. A. Hourdin, C. Cave, J. d’Angelo, P. Chaminade, Tetrahedron
Lett. 1999, 40, 7091. d) D. Bensa, T. Constantieux, J. Rodriguez,
Synthesis 2004, 923.
5
6
(
Table 3, Entry 5). The end-capped NDEAP as trimethylsiloxide
showed similar reactivity and recyclability as non-end-capped
NDEAP.
7
8
R. Ballini, G. Bosica, D. Livi, A. Palmieri, R. Maggi, G. Sartori, Tet-
rahedron Lett. 2003, 44, 2271.
Typical experimental procedure in practical scale: A commercial
microwave oven was modified to install magnetic stirring unit at
the bottom and a pipe vertically through the top to insert a glass
condenser. A stirred suspension of ethyl 2-cyclopentanecarboxylate
(1) (3.124 g, 20 mmol), 3-buten-2-one (2) (1.65 mL, 30 mmol), and
NDEAP (766 mg, 1 mmol) in water (20 mL) was irradiated 100-W
microwave for 2 min with vigorous stirring. The reaction tempera-
Table 3. Recycle use of NDEAPa
Entry
Recycle
Yield/%
1
2
3
4
0
1
2
3
4
92
78
74
51
76
ꢀ
ture was ramped from room temperature to 70 C and maintained
at the temperature, which was monitored by a radiation thermome-
ter. After being cooled to room temperature, the product was
triturated with ethyl acetate. Evaporation of the solvent followed
b
5
a
The reaction was carried out in a similar manner as
in Table 1 except NDEAP loading (0.1 equiv.) under
microwave irradiation at 100-W for 10 min, when the
temperature was ramped from room temperature to
ꢀ
by Kugelrohr distillation (120 C, 1.0 mmHg) and column chroma-
tography (eluent: ethyl acetate:hexane = 1:1) of the forerun provid-
ed product 3 (3.596 g, 79%, 92% BRSM) along with recovered start-
ing material 1 (437 mg, 14%).
ꢀ
b
7
0 C. NDEAP was washed with Na2CO3.
Published on the web (Advance View) July 15, 2006; doi:10.1246/cl.2006.926