T. Hida et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 9 (2011)
961
Table 1. Effects of Support of Cs2CO3 on the Activity and
the Selectivity for the Michael Addition of Diethyl
Malonate to Methyl Acrylatea)
Table 2. Effects of Cesium Precursor and Calcination of
Cesium Salt Supported on Al2O3 on the Activity and
Selectivity for the Michael Addition of Diethyl Malonate
to Methyl Acrylatea)
Yield (Selectivity)b)/%
Conversion
Support
Yield (Selectivity)b)/%
/%
Calcination Conversion
3
4
/°C
/%
3
4
None
98
93
4
8
33
91
83 (87)
77 (83)
4 (100)
8 (100)
33 (99)
77 (85)
13 (13)
17 (10)
0 (0)
0 (0)
0.3 (1)
14 (15)
c)
Al2O3
MCM-41
SiO2
Charcoal
KFc)
Cs2CO3
®
95
93
75
35
94
0
79 (83)
77 (83)
68 (90)
35 (99)
73 (78)
®
16 (17)
16 (17)
7 (10)
0.3 (1)
21 (22)
®
450
700
c)
CsOAc
CsNO3
®
450
c)
®
a) Reaction conditions: 1: 1.0 mmol; 2: 1.2 mmol; catalyst
(loaded 30 wt % cesium on the support, and calcined at 450 °C
for 6 h): 100 mg; solvent: toluene 4 mL; temperature: 80 °C;
period: 6 h. b) Selectivities for 3 and 4 are shown in
parentheses. c) KF/Al2O3 (30 wt % KF on Al2O3).
450
700
8
76
8 (100)
68 (89)
0 (0)
8 (11)
a) Reaction conditions: 1: 1.0 mmol; 2: 1.2 mmol; catalyst:
30 wt % Cs/Al2O3 100 mg; solvent: toluene 4 mL; temperature:
80 °C; period: 6 h. b) Selectivities for 3 and 4 are shown in
parentheses. c) Dried at 40 °C.
acrylate (2; 1.2 mmol; Nakalai Tesque, Kyoto, Japan) in the
presence of the catalyst (100 mg) for 4 h at 80 °C using toluene
as solvent. The conversion and selectivity for diethyl [2-
(methoxycarbonyl)ethyl]malonate (3) and diethyl bis[2-
(methoxycarbonyl)ethyl]malonate (4) were determined on a
Shimadzu GC-18A Gas chromatograph equipped with a
TC-17 column (30 m © 0.25 mm © 0.25 ¯m, GL Science Inc.,
Tokyo, Japan). The chemical structures of 3 and 4 were
highest activities, had similar level activity to 30 wt % Cs2CO3/
Al2O3.12,13
Mesoporous arrays of MCM-41 were destroyed by
the loading of Cs2CO3 as shown in Figures S1 and S2 in
Supporting Information. Kloetstra et al. and Ernst et al.
described the decay of mesoporous arrays of MCM-41 by
cesium loading.25-27 Resulting catalysts were modestly active
for the Michael addition of 1 to 2 although high activities were
described for Knoevenagel reaction of benzaldehyde with ethyl
cyanoacetate or malononitrile,25,27 and for the Michael addition
of diethyl malonate (1) to neopentyl glycol diacrylate.26
Cs2CO3, itself, had high activity corresponding to 30 wt %
Cs2CO3/Al2O3. However, it was difficult to separate the
catalyst and product solution by filtration, because the solution
was colloidal after the reaction. Loading of Cs2CO3 on Al2O3 is
a promising way for the separation of the catalysts from the
products (see also recycling section).
Effects of Types of Cesium Salt. Table 2 shows typical
results of three types of cesium salts supported on Al2O3 for
the Michael addtion of 1 to 2. 30 wt % Cs2CO3/Al2O3 gave high
conversion of both of the samples dried at 40 °C and calcined at
450 °C. Catalytic activity of 30 wt % CsOAc/Al2O3 dried at
40 °C remained 35%, however the activity was enhanced after
the calcination at 450 °C. On the other hand, 30 wt % CsNO3/
Al2O3 has almost no activity using a sample dried at 40 °C. The
calcination of 30 wt % CsNO3/Al2O3 at 450 °C gave only low
activity, however reasonable activity appeared after the calci-
nation at 700 °C. These differences are due to the active species
formed by the calcination. Detailed discussion on the dif-
ferences will be given in the later sections. We adopted Cs2CO3
supported on Al2O3 after the calcination at 450 °C for further
studies of the Michael additions.
1
determined by H NMR spectroscopy on a Varian Inova 400
spectrometer after purification by column chromatography
using hexane/EtOAc (10/1) as an eluent. The products were
also confirmed on a Shimadzu GCMS-QP5000 Gas chromato-
graph-Mass spectrometer. The yield and selectivity of adducts
were calculated on the basis of the amount of donor 1
introduced and consumed, respectively. The Michael reactions
using other substrate were carried out in the same ways as the
reactions of 1 and 2.
Recycling of the Catalysts. Recycling of the used catalysts
was carried out after filtration of products and washing well
with toluene. Resulting catalyst was calcined at 450 °C for 6 h.
The reactions were carried out in the same conditions as the
first reaction.
Characterization of Catalysts. Powder X-ray diffraction
(XRD) was recorded on a Shimadzu XRD-6000 diffractometer
with Cu K¡ radiation (¡ = 1.5418 ¡). FT-IR spectra were
measured by KBr method using Nexus 470, Thermo Electron,
MA, USA. Thermogravimetric analysis (TGA) and differential
thermal analysis (DTA) were carried out on a Shimadzu
Thermogravimetric Analyzer DTG-50A with a temperature
¹1
programmed rate of 10 °C min in an air flow.
Results and Discussion
Effects of Support for Cs2CO3. Table 1 shows effects of
the support for Cs2CO3 on the Michael addition of 1 to 2.
Al2O3, itself, had no catalytic activity, however Cs2CO3
supported on Al2O3 appeared high activity for the reaction. 3
(monoadduct) was a principal product by the first step reaction
of 1 with 2, accompanying small amounts of 4 (diadduct) by
the second step reaction of 3 with 2. Charcoal gave moderately
activity, however silica supports, MCM-41 and silica gel, had
only low activities. 30 wt % KF/Al2O3, which has one of the
Effects of Reaction Temperature. Figure 1 shows effects
of reaction temperature on the Michael addition of 1 to 2 over
30 wt % Cs2CO3/Al2O3. The reaction occurred even at 25°C in
low conversion, and enhanced rapidly with an increase in the
temperature.
3 was an only product at low temperature, however the
formation of 4 was increased with the increase in the