Immobilization of 1,5,7-triazabicyclo[4.4.0]dec-5-ene on magnetic γ-Fe2O3 nanoparticles: A highly recyclable and efficient nanocatalyst for the synthesis of organic carbonates

Article abstract of DOI:10.1002/ejic.201301586

1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe₂O₃ nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. The catalyst is quantitatively recovered by an external magnet and can be reused for six cycles with almost consistent activity. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on magnetic γ-Fe₂O₃ nanoparticles as a magnetic nanocatalyst. The nanoparticle reagent was obtained with good loading levels and has been successfully used for the efficient and selective synthesis of organic carbonates by the direct condensation of alcohols and diethyl carbonate. Copyright

Full text of DOI:10.1002/ejic.201301586

FULL PAPER
DOI:10.1002/ejic.201301586
Immobilization of 1,5,7-Triazabicyclo[4.4.0]dec-5-ene on
Magnetic γ-Fe2O3 Nanoparticles: A Highly Recyclable
and Efficient Nanocatalyst for the Synthesis of Organic
Carbonates
Liqiang Wu*[a] and Shuanbao Tian[b]
Keywords: Heterogeneous catalysis / Iron / Nanoparticles / Immobilization / Transesterification / Carbonates
1,5,7-Triazabicyclo[4.4.0]dec-5-ene was immobilized on
magnetic γ-Fe2O3 nanoparticles as a magnetic nanocatalyst.
The nanoparticle reagent was obtained with good loading
levels and has been successfully used for the efficient and
selective synthesis of organic carbonates by the direct con-
densation of alcohols and diethyl carbonate. The catalyst is
quantitatively recovered by an external magnet and can be
reused for six cycles with almost consistent activity.
nanoparticles as heterogeneous catalysts have attracted a
great deal of attention owing to their interesting structures
and high catalytic activities. Furthermore, nanometer-sized
particles are easily dispersible in solution to form stable sus-
pensions.[16] In spite of these advantages, the tedious recycl-
ing of such small particles by expensive ultracentrifugation
has limited their application. To further address the issues
of recyclability and reusability, magnetic nanoparticles
(MNPs) have emerged as excellent supports that are amena-
ble to simple magnetic separation.[17] Moreover, magnetic
nanoparticles can be functionalized readily through appro-
priate surface modifications, and various functionalities can
be loaded.[18]
As a continuation of our interest in the development of
efficient and environmentally benign synthetic methodolo-
gies,[19] we report herein on the preparation of a new type
of magnetically separable γ-Fe2O3-immobilized 1,5,7-triaza-
bicyclo[4.4.0]dec-5-ene nanoparticles (MNPs-TBD) and
their application for the synthesis of organic carbonates
(Scheme 1).
Introduction
Organic carbonates are useful intermediates for the syn-
thesis of fine chemicals,[1] pharmaceuticals,[2] plasticizers,
synthetic lubricants,[3] monomers for organic glasses,[4] and
solvents.[5] They are also used as linkers and tagging moie-
ties in solid-phase chemistry.[6] The most common pro-
cedures for the synthesis of these compounds include the
reaction of phosgene with diols and the coupling of halo
compounds with alcohols and phenols.[7] As highly toxic
and harmful reagents, such as phosgene or haloformates,
are involved, most procedures for the synthesis of these
compounds are not environmentally acceptable. Recently,
symmetrical organic carbonates, especially dimethyl carb-
onate (DMC) and diethyl carbonate (DEC), have been syn-
thesized from CO2, epoxides, and alcohols[8] or synthesized
directly from CO2 and alcohols.[9] The synthesis of unsym-
metrical organic carbonates by transesterification with
alcohols has been successfully achieved by solid base cata-
lysts, such as MCM-41-TBD,[10] Mg/La metal oxide,[11]
CsF/α-Al2O3,[12] nanocrystalline MgO,[13] metal–organic
frameworks,[14] and Bu2SnMoO4.[15] However, the develop-
ment of highly efficient synthetic routes for the production
of unsymmetrical organic carbonates is an interesting topic.
With increasing environmental concerns, the develop-
ment of efficient and recoverable heterogeneous catalysts
has become an important research field. In this context,
[a] School of Pharmacy, Xinxiang Medical University,
East of JinSui Road of Xinxiang City, 453003 Henan Province,
P. R. China
E-mail: wliq870@163.com
http://www.xxmu.edu.cn/
[b] School of Basic Medical Sciences, Xinxiang Medical University,
Xinxiang 453003, P. R. China
Scheme 1. Synthesis of organic carbonates by using MNPs-TBD.
2080 © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2014, 2080–2087

www.eurjic.org
FULL PAPER
Scheme 2. Synthesis of MNPs-TBD.
Results and Discussion
γ-Fe2O3 nanoparticles were prepared through a chemical
coprecipitation method and were subsequently coated with
(3-chloropropyl)triethoxysilane to achieve 3-chloropropyl-
functionalized γ-Fe2O3. Ultimately, the reaction of this ma-
terial containing chlorine groups with 1,5,7-triazabi-
cyclo[4.4.0]dec-5-ene led to MNPs-TBD nanoparticles
(Scheme 2). The MNPs-TBD was characterized by FTIR
spectroscopy, energy-dispersive spectroscopy (EDS), scan-
ning electron microscopy (SEM), transmission electron mi-
croscopy (TEM), powder X-ray diffraction (XRD), vibrat-
ing sample magnetometery (VSM), thermogravimetric
analysis (TGA), and elemental analysis. The specific surface
areas of the powders were determined by use of the Bru- Figure 1. FTIR spectra of γ-Fe2O3 and MNPs-TBD.
nauer–Emmett–Teller (BET) method. Unfortunately, owing
to the magnetic properties of MNPs-TBD, it is impossible
to further characterize this material by solid-state NMR
spectroscopy.
Figure 1 shows the FTIR spectra of γ-Fe2O3 nanopar-
ticles and MNPs-TBD. The FTIR spectrum of γ-Fe2O3
nanoparticles exhibits two characteristic peaks at 561 and
636 cm–1 owing to the stretching vibrations of the Fe–O
bond in γ-Fe2O3. The FTIR spectrum of MNPs-TBD
shows Fe–O vibrations in the same vicinity. Compared with
the spectrum of the unfunctionalized γ-Fe2O3, the signifi-
cant features in the spectrum of MNPs-TBD were the peaks
at 2918 and 2846 (C–H stretching vibration), 1126 and 1001
Figure 2. EDS spectrum of MNPs-TBD.
(Si–O stretching vibrations), and 1628 and 1320 cm–1 (C=N
and C–N vibrations of the TBD ring, respectively). This
analysis, in combination with the microanalysis data (Fig-
ure 2), indicated the successful anchoring of the TBD
groups on the surface of γ-Fe2O3.
The XRD pattern of MNPs-TBD shows characteristic
peaks and relative intensities that match well with the cubic
structure of maghemite (JCPDS file No 39–1364). Diffrac-
tion peaks at 2θ ≈ 30.62, 35.92, 43.48, 54.00, 57.62, and
63.36, which correspond to the (220), (311), (400), (422),
(511), and (440) faces, are readily recognized from the XRD
pattern (Figure 3). The average crystallite size was calcu-
lated as 14.2 nm by using the Scherrer equation.
Bond formation between the nanoparticles and the cata-
lyst can be inferred from the TGA results. TGA was also
used to determine the percentage of organic functional
groups chemisorbed onto the surface of the magnetic nano-
Figure 3. XRD pattern of MNPs-TBD.
particles. The TGA curve of the MNPs-TBD shows the upon heating (Figure 4). The weight loss below 100 °C is
mass loss of the organic functional group as it decomposes due to the removal of physically adsorbed water molecules.
Eur. J. Inorg. Chem. 2014, 2080–2087
2081
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Organic groups have been reported to desorb at tempera-
tures above 250 °C. A weight loss of ca. 24.6% from 250–
760 °C results from the decomposition of the organic spacer
grafted to the MNPs surface. On the basis of these results,
the grafting of the TBD groups on the MNPs is verified.
Figure 4. TGA curve of MNPs-TBD.
The shape and surface morphology of the MNPs-TBD
were investigated by SEM and TEM. As shown in Figure 5,
the low-magnification SEM images shows small nanosized
grains with spherical and quasispherical morphology with
a narrow size distribution, which indicates the nanocrys-
talline nature of the γ-Fe2O3 nanoparticles. The presence
of some larger particles indicates aggregation or overlap of
smaller particles. The sizes of the MNPs-TBD particles
were further analyzed by TEM, and the results (Figure 6)
show that the nanoparticles have dimensions ranging from
10 to 20 nm. In the TEM images, the shapes are somewhat
rectangular, which is attributed to the presence of TBD
groups covalently attached to the γ-Fe2O3 surfaces.
Figure 6. TEM (top) and HR-TEM (bottom) images of MNPs-
TBD.
sufficiently high for magnetic separation. The strong mag-
netization of the nanoparticles was also revealed by simple
attraction with an external magnet.
Figure 5. SEM image of MNPs-TBD.
Superparamagnetic particles are beneficial for magnetic
separation, and the magnetic properties of γ-Fe2O3 and
MNPs-TBD were characterized by VSM. The room-tem-
perature magnetization curves of γ-Fe2O3 and MNPs-TBD
are shown in Figure 7. As expected, the bare γ-Fe2O3
showed the higher magnetic value (saturation magnetiza-
tion, Ms) of 61.2 emu/g, and the Ms value of MNPs-TBD
is lower because the nonmagnetic material (organic ligands)
Figure 7. Magnetic curves of MNPs-TBD and γ-Fe2O3.
The N2 adsorption–desorption isotherm provided a valu-
on the particle surface makes a larger percentage of the able tool for the study of the textural and structural proper-
mass of the particle nonmagnetic. However, this value is ties. The specific surfaces areas of the powders were deter-
Eur. J. Inorg. Chem. 2014, 2080–2087
2082
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
mined by use of the BET method. The BET results showed reaction temperature was also examined, and 125 °C was
that the average surface area of γ-Fe2O3 was 73.79 m2 g–1 the optimum temperature. Temperatures of less than 100 °C
and that of MNPs-TBD was 29.87 m2 g–1 (Figure 8). γ- led to significantly decreased yields of the desired product.
Fe2O3 had a much higher surface area than that of MNPs-
BETB. This seems logical as the successful anchoring of
TBD on the surface of MNPs decreases the surface area.
Table 1. Optimization of the reaction conditions for the synthesis
of benzyl ethyl carbonate.
Entry
Catalyst [mg]
T [°C]
Time [h]
Yield [%]
1
2
3
4
5
6
7
8
9
0
0
r.t.
48
20
10
10
10
10
10
10
10
0
trace
82
97
94
95
69
86
91
125
125
125
125
125
100
110
120
100
150
200
250
150
150
150
In an effort to understand the scope of the reaction, the
reactivity of a variety of alcohols, including alkyl, cyclic,
heterocyclic, aryl, and diols, with diethyl dicarbonate in the
presence of the best catalytic system was investigated
(Table 2). All of the substrates were selectively transformed
to the corresponding unsymmetrical carbonates in quanti-
tative yields; disubstituted symmetric carbonates were not
formed in the reactions. Notably, 1,2-diols led to the forma-
tion of cyclic carbonates (Table 2, Entries 13–15), whereas
cyclic products were not formed when the number of meth-
ylene groups between the alcohol functions increased. Thus,
2,5-hexanediol and 1,4-cyclohexanediol yielded the corre-
sponding biscarbonates as the sole reaction products
(Table 2, Entries 16 and 17).
A plausible mechanism could be represented by a typical
transesterification process; it is hypothesized that the pres-
ent transformation may have resulted from the catalytic cy-
cle depicted in Scheme 3. MNPs-TBD is sufficiently
nucleophilic to attack the carbonyl group of diethyl carb-
onate to afford the MNPs-TBD salt. Subsequent attack of
the alcohol on the activated carbonyl group of the MNPs-
TBD salt gives the product and restores the catalyst. This
step is particularly favored as the positive charge, delocal-
ized over the three nitrogen atoms, promotes the nucleo-
philic attack of the carbonyl by enhancing its electrophilic
character.
Figure 8. N2 adsorption–desorption isotherms of γ-Fe2O3 (top)
and MNPs-TBD (bottom).
The feasibility of repeated use of MNPs-TBD was also
Initially, we condensed benzyl alcohol (10 mmol) and di- investigated for the reaction of benzyl alcohol with diethyl
ethyl dicarbonate (165 mmol, 20 mL). They were stirred at dicarbonate. This catalyst demonstrated excellent recycl-
room temperature for 48 h in the absence of the catalyst, ability. The catalyst can be efficiently recovered easily and
and very poor yields were obtained (Table 1, Entry 1). To rapidly from the product by exposure to an external magnet
enhance the yield of the desired product, the temperature (Figure 9). To remove the residual product, the remaining
of the reaction was increased to 125 °C, and no appreciable magnetic nanoparticles were further washed with EtOH,
increment in the product yield was observed (Table 1, En- air-dried, and used directly for the next reaction without
try 2). Then, we repeated the reaction in the presence of further purification. The recycled catalyst was used for up
catalyst and also evaluated the amount of catalyst required to six runs with little loss of activity (Figure 10). After the
for this transformation; by using 100 mg/mmol of catalyst, catalyst was recycled, the nanocatalyst particle size and
we obtained 82% yield. The maximum yield of 97% was morphology have no significant changes, and the loading
obtained when the reaction was performed with 150 mg/ amount of the catalyst decreased to 0.652 mmol/g on the
mmol of the catalyst. Any further increase of catalyst load- basis of TEM and TGA results (Figure 11). However, the
ing does not affect the yield (Table 2, Entries 5 and 6). The activity of the catalyst showed no significant loss.
Eur. J. Inorg. Chem. 2014, 2080–2087
2083
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
Table 2. Preparation of unsymmetrical organic carbonates.
Scheme 3. A plausible mechanism for the reaction.
Figure 9. Left: reaction mixture containing MNPs-TBD. Right:
MNPs-TBD collected by using an external magnet after the reac-
tion.
Figure 10. Recycling experiments for the synthesis of benzyl ethyl
carbonate.
To demonstrate the merit of the present work, we com-
pared the results of the synthesis of benzyl ethyl carbonate
in the presence of various catalysts. Only 5% of the target
compound, benzyl ethyl carbonate, was obtained in the
presence of γ-Fe2O3 nanoparticles. When this reaction was
performed with inorganic bases such as Na2CO3 and
K2CO3, only trace amounts of the expected product were
obtained. In the presence of organic bases such as 1,4-di-
Eur. J. Inorg. Chem. 2014, 2080–2087
2084
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
ethyl carbonate is only produced in traces in the presence
of EtONa, which suggests that the ethoxide ion is not the
catalyst. However, by using a guanidinium salt such as
[TBD][Ac], benzyl ethyl carbonate was obtained in 56%
yield; therefore, the catalyst may be present in the reaction
mixture as N-carbethoxyguanidinium.
Conclusions
We have synthesized the first MNPs-TBD for use as a
magnetic heterogeneous basic nanocatalyst. The catalyst is
easily synthesized and can catalyze the synthesis of organic
carbonates with good-to-high yields under different condi-
tions. The characteristic aspects of this catalyst are its rapid,
simple, and efficient separation by an appropriate external
magnet; this minimizes the catalyst loss during separation,
and the catalyst is reusable several times with little loss of
activity. In addition, MNPs-TBD couples the advantages of
heterogeneous and homogeneous TBD-based systems,
which make it a promising material for industrial applica-
tions.
Experimental Section
General: Powder X-ray diffraction (XRD) patterns were recorded
by using a Cu-Kα radiation source with a Bruker D8 Advance pow-
der diffractometer. Scanning electron microscopy (SEM) studies
were conducted with an Inspect F50 scanning electron microscope.
Transmission electron microscopy (TEM) studies were performed
by using an FEI Tecnai G2 20 transmission electron microscope
at an accelerating voltage of 150 kV. Elemental compositions were
determined with a Hitachi S-4800 scanning electron microscope
equipped with an energy-dispersive X-ray analysis (EDAX) spec-
trometer (SEM-EDS). Magnetic measurements of particles were
performed by using a vibrating sample magnetometer (MPMS-XL-
7). N2 adsorption–desorption isotherms were measured by using a
NOVOE 4000/TriStar II 3020 instrument at liquid nitrogen tem-
perature (77 K). The specific surface areas were calculated from the
Figure 11. TEM image (top) and TGA curve (bottom) of recycled
MNPs-TBD.
azabicyclo[2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]-
undec-7-ene (DBU), and TBD, the product was obtained in
low yield. The best result was obtained by using MNPs- BET equation. Thermogravimetric analysis was performed under
nitrogen by using a DT-40 thermoanalyzer. IR spectra were deter-
mined with a FTS-40 infrared spectrometer. NMR spectra were
recorded with a Bruker AV-400 spectrometer at room temperature
with tetramethylsilane (TMS) as an internal standard; coupling
constants (J) were measured in Hz. Elemental analyses were per-
formed with a Vario-III elemental analyzer. Melting points were
determined with a XT-4 binocular microscope. All solvents used
were strictly dried according to standard operations and stored
over 4A molecular sieves. All other chemicals (AR grade) were ob-
tained from commercial resources and used without further purifi-
cation. All products were characterized by comparison of their
spectral and physical data with those previously reported. The reac-
tion progress was monitored by TLC.
TBD as the catalyst (Table 3). These results confirm that
the inorganic support can influence the catalyst efficiency.
As a strong base, the supported TBD is sufficiently nucleo-
philic to attack the carbonyl group of diethyl carbonate to
produce the guanidinium salt. Of course, an EtO– counter-
ion may be the actual basic catalyst, and some reactions
were performed to test this hypothesis. However, benzyl
Table 3. Synthesis of benzyl ethyl carbonate by using various cata-
lysts.
Entry
Catalyst
Time [h]
Yield [%]
1
2
3
4
5
6
7
8
9
nano γ-Fe2O3
Na2CO3
K2CO3
DABCO
DBU
TBD
EtONa
24
24
24
10
10
10
10
10
10
5
trace
trace
27
26
38
trace
56
97
Large-Scale Preparation of Magnetic γ-Fe2O3 Nanoparticles:
FeCl2·4H2O (9.25 mmol) and FeCl3·6H2O (15.8 mmol) were dis-
solved in deionized water (150 mL) under an Ar atmosphere at
room temperature. A NH4OH solution (25%, 50 mL) was then
added dropwise to the stirring mixture at room temperature to in-
crease the reaction pH to 11. The resulting black dispersion was
continuously stirred for 1 h at room temperature and then heated
to reflux for 1 h to yield a brown dispersion. The magnetic nano-
[TBD][Ac]
MNPs-TBD
Eur. J. Inorg. Chem. 2014, 2080–2087
2085
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
particles were then purified by a repeated centrifugation, decan-
tation, and redispersion cycle (three times). The as-synthesized
sample was heated to 200 °C at 2 °C/min and then kept in the fur-
nace for 3 h to give a reddish-brown powder.
NMR (100 MHz, CDCl3): δ = 155.0, 70.3, 64.5, 31.8, 29.5, 29.4,
28.6, 26.3, 22.3, 14.3, 14.0 ppm. C11H22O3 (202.29): calcd. C 65.31,
H 10.96; found C 65.33, H 11.02.
3g: 1H NMR (400 MHz, CDCl3): δ = 4.25–4.12 (m, 4 H), 1.74–
1.63 (m, 2 H), 1.46–1.27 (m, 17 H), 0.88 (t, J = 7.2 Hz, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 155.2, 70.9, 64.3, 32.0, 29.8,
29.7, 29.4, 29.3, 28.6, 26.2, 22.3, 14.4, 14.1 ppm. C13H26O3
(230.35): calcd. C 67.79, H 11.38; found C 67.86, H 11.29.
3h: 1H NMR (400 MHz, CDCl3): δ = 4.23–4.18 (m, 2 H), 3.88–
3.83 (m, 1 H), 1.82–1.76 (m, 2 H), 1.56–1.37 (m, 8 H), 1.33 (t, J =
7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 155.2, 80.3,
64.8, 32.9, 28.3, 22.3, 14.1 ppm. C9H16O3 (172.22): calcd. C 62.77,
H 9.36; found C 62.83, H 9.33.
3i: 1H NMR (400 MHz, CDCl3): δ = 4.60–4.12 (m, 3 H), 1.95–1.44
(m, 5 H), 1.35–1.06 (m, 12 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 155.3, 79.8, 64.7, 43.0, 28.4, 27.4, 25.9, 18.7, 14.2 ppm.
C11H20O3 (200.28): calcd. C 65.97, H 10.07; found C 65.88, H
10.01.
Preparation of MNPs-TBD: We prepared MNPs-TBD similarly to
the SiO2-TBD first prepared by Polo and co-workers.[20] A mixture
of γ-Fe2O3 (5.0 g) and (3-chloropropyl)triethoxysilane (5.0 mL,
42.5 mmol) were added to toluene (50 mL), and the mixture was
stirred at room temperature for 15 min and then heated to reflux
for 24 h. The mixture was cooled to room temperature, and the
products were sedimented with a magnet, washed successively with
dry toluene (50 mL), and then dried under reduced pressure at
100 °C for 8 h. The loading amount of the intermediate materials
functionalized with chloropropyl groups was determined to be
0.723 mmol/g by elemental analysis.
This material containing chlorine groups (5 g) was then was dis-
persed in dry toluene (50 mL) by sonication for 1 h, and a solution
of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (0.5 g) in toluene (20 mL) was
then added. The reaction mixture was heated to reflux under nitro-
gen gas for 1 d. After this time, the solid was collected by using a
permanent magnet, and it was washed with toluene (3ϫ 20 mL)
and dichloromethane (3ϫ 20 mL) and dried at room temperature
for 24 h. The loading amount of the catalyst was determined to be
0.705 mmol/g by elemental analysis and TGA.
3j: 1H NMR (400 MHz, CDCl3): δ = 4.53 (d, J = 7.0 Hz, 1 H),
4.22–4.15 (m, 2 H), 2.41 (d, J = 4.4 Hz, 1 H), 2.31–2.26 (m, 1 H),
1.75–1.40 (m, 5 H), 1.32 (t, J = 7.2 Hz, 3 H), 1.22–1.08 (m, 2 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 155.3, 80.4, 64.3, 43.3,
40.3, 36.8, 36.0, 30.8, 23.9, 14.2 ppm. C10H16O3 (184.23): calcd. C
65.19, H 8.75; found C 65.23, H 8.70.
General Procedure for the Synthesis of Unsymmetrical Organic
Carbonates with MNPs-TBD: A mixture of the alcohol (10 mmol),
diethyl dicarbonate (20 mL), and MNPs-TBD (150 mg) was stirred
at 125 °C for 3–10 h. After cooling to room temperature, MNPs-
BETB was collected at the side of the flask by using a small
magnet, and the residual diethyl dicarbonate were removed under
reduced pressure. The crude product was chromatographed on
silica gel with a mixture of hexane/ethyl acetate (80:20) as eluent.
3k: 1H NMR (400 MHz, CDCl3): δ = 4.25–3.76 (m, 7 H), 2.11–
1.86 (m, 3 H), 1.75–1.55 (m, 1 H), 1.30 (t, J = 7.2 Hz, 3 H), ppm.
13C NMR (100 MHz, CDCl3): δ = 155.1, 76.9, 69.8, 68.5, 64.3,
27.9, 25.8, 14.3 ppm. C8H14O4 (174.20): calcd. C 55.16, H 8.10;
found C 55.11, H 8.07.
1
3l: H NMR (400 MHz, CDCl3): δ = 4.51 (td, J = 4.4, 11.4 Hz, 1
H), 4.23–4.17 (m, 2 H), 2.10–2.05 (m, 1 H), 1.99–1.92 (m, 1 H),
1.82–0.86 (m, 19 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 155.2,
79.3, 64.7, 46.8, 39.4, 33.6, 28.7, 25.6, 22.4, 21.3, 20.9, 14.1 ppm.
C13H24O3 (228.33): calcd. C 68.38, H 10.59; found C 68.43, H
10.55.
1
3a: H NMR (400 MHz, CDCl3): δ = 7.39–7.30 (m, 5 H), 5.22 (s,
2 H), 4.22–4.18 (m, 2 H), 1.33 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 155.4, 136.3, 129.0, 128.6, 128.1, 70.3, 64.5,
14.5 ppm. C10H12O3 (180.20): calcd. C 66.65, H 6.71; found C
66.58, H 6.75.
1
3m: H NMR (400 MHz, CDCl3): δ = 7.44–7.23 (m, 5 H), 5.65 (t,
1
J = 8.0 Hz, 1 H), 4.81 (t, J = 8.0 Hz, 1 H), 4.33 (t, J = 8.0 Hz, 1
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 155.1, 135.9, 129.5,
128.9, 126.7, 71.4 ppm. C9H8O3 (164.16): calcd. C 65.85, H 4.91;
found C 65.92, H 4.88.
3b: H NMR (400 MHz, CDCl3): δ = 7.38–7.28 (m, 5 H), 5.36 (q,
J = 7.0 Hz, 1 H), 4.23–4.19 (m, 2 H), 1.59 (t, J = 7.0 Hz, 3 H),
1.33 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
155.3, 136.8, 128.9, 128.5, 127.6, 72.0, 64.3, 21.5, 14.1 ppm.
C11H14O3 (194.23): calcd. C 68.02, H 7.27; found C 67.97, H 7.32.
1
3n: H NMR (400 MHz, CDCl3): δ = 4.81–4.64 (m, 1 H), 4.50 (t,
1
J = 8.0 Hz, 1 H), 4.12 (dd, J = 7.2, 8.0 Hz, 1 H), 2.02–1.22 (m, 6
H), 0.97 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 155.6, 76.9, 69.2, 33.7, 26.5, 22.8, 14.2 ppm. C7H12O3 (144.17):
calcd. C 58.32, H 8.39; found C 58.36, H 8.32.
3c: H NMR (400 MHz, CDCl3): δ = 7.37–7.26 (m, 4 H), 5.60 (q,
J = 7.0 Hz, 1 H), 4.38–4.17 (m, 2 H), 1.58 (t, J = 7.0 Hz, 3 H),
1.33 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
154.9, 140.1, 134.6, 128.9, 128.0, 75.6, 64.4, 22.3, 14.2 ppm.
C11H13ClO3 (228.67): calcd. C 57.78, H 5.73; found C 57.84, H
5.75.
1
3o: H NMR (400 MHz, CDCl3): δ = 7.50–7.39 (m, 4 H), 5.64 (t,
J = 8.0 Hz, 1 H), 4.79 (dd, J = 7.6, 8.4 Hz, 1 H), 4.62 (s, 2 H), 4.36
(t, J = 7.6, 8.4 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
156.8, 139.1, 136.4, 130.4, 126.4, 78.3, 69.8, 43.7 ppm. C10H9BrO3
(257.08): calcd. C 46.72, H 3.53; found C 46.77, H 3.49.
3p: 1H NMR (400 MHz, CDCl3): δ = 4.85–4.69 (m, 2 H), 4.22–
4.17 (m, 4 H), 1.81–1.56 (m, 4 H), 1.33 (t, J = 7.0 Hz, 6 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 154.9, 75.1, 74.5, 63.9, 32.0,
31.5, 20.2, 19.8, 14.3 ppm. C16H22O6 (310.35): calcd. C 54.95, H
8.45; found C 55.02, H 8.42.
1
3d: H NMR (400 MHz, CDCl3): δ = 7.36–7.27 (m, 5 H), 4.38 (t,
J = 7.2 Hz, 2 H), 4.25–4.18 (m, 2 H), 2.98 (t, J = 7.2 Hz, 2 H),
1.31 (t, J = 7.0 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
155.0, 138.6, 128.9, 128.0, 126.9, 74.8, 64.2, 33.8, 14.2 ppm.
C11H14O3 (194.23): calcd. C 68.02, H 7.27; found C 68.07, H 7.25.
1
3e: H NMR (400 MHz, CDCl3): δ = 7.36–7.23 (m, 5 H), 6.59 (d,
J = 15.6 Hz, 1 H), 6.33 (dt, J = 5.7, 15.6 Hz, 1 H), 4.38 (t, J =
5.7 Hz, 2 H), 4.23–4.18 (m, 2 H), 1.31 (t, J = 7.0 Hz, 3 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 155.2, 135.9, 132.3, 128.7, 128.2,
126.9, 124.5, 72.9, 64.4, 14.2 ppm. C12H14O3 (206.24): calcd. C
69.88, H 6.84; found C 70.02, H 6.79.
3q: 1H NMR (400 MHz, CDCl3): δ = 4.78–4.65 (m, 2 H), 4.22–
4.18 (m, 4 H), 2.11–1.56 (m, 8 H), 1.33 (t, J = 7.0 Hz, 6 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 154.7, 74.7, 73.8, 63.9, 63.7,
3f: 1H NMR (400 MHz, CDCl3): δ = 4.22–4.11 (m, 4 H), 1.73–1.65 27.7. 27.4, 14.3 ppm. C12H20O6 (260.29): calcd. C 55.37, H 7.74;
(m, 2 H), 1.44–1.26 (m, 13 H), 0.87 (t, J = 7.2 Hz, 3 H) ppm. 13C
found C 55.42, H 7.69.
Eur. J. Inorg. Chem. 2014, 2080–2087
2086
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
[12] B. Veldurthy, J. M. Clacens, F. Figueras, Eur. J. Org. Chem.
2005, 1972–1976.
Acknowledgments
[13] M. L. Kantam, U. Pal, B. Sreedhar, B. M. Choudary, Adv.
Synth. Catal. 2007, 349, 1671–1675.
[14] Y.-X. Zhou, S.-G. Liang, J.-L. Song, T.-B. Wu, S.-Q Hu, H.-Z.
Liu, B.-X. Han, Acta Phys.-Chim. Sin. 2010, 26, 939–945.
[15] J. L. Song, B. B. Zhang, T. B. Wu, G. Y. Yang, B. X. Han,
Green Chem. 2011, 13, 922–927.
The authors are pleased to acknowledge financial support from the
Scientific Research Fund of Xinxiang Medical University (grant
number 2013QN130).
[16] V. Polshettiwar, R. S. Varma, Green Chem. 2010, 12, 743–754.
[17] a) S. Shylesh, V. Schunemann, W. R. Thiel, Angew. Chem. Int.
Ed. 2010, 49, 3428–3459; Angew. Chem. 2010, 122, 3504; b)
Y. H. Zhu, L. P. Stubbs, F. Ho, R. Z. Liu, C. P. Ship, J. A. Mag-
uire, N. S. Hosmane, ChemCatChem 2010, 2, 365–374; c) T. Q.
Zeng, W. W. Chen, C. M. Cirtiu, A. Moores, G. H. Song, C. J.
Li, Green Chem. 2010, 12, 570–573.
[18] a) A. Megia-Fernandez, M. Ortega-Munoz, J. Lopez-Jaramillo,
F. Hernandez-Mateo, F. Santoyo-Gonzalez, Adv. Synth. Catal.
2010, 352, 3306–3320; b) B. G. Wang, B. C. Ma, Q. O. Wang,
W. Wang, Adv. Synth. Catal. 2010, 352, 2923–2928; c) H. Fir-
ouzabadi, N. Iranpoor, M. Gholinejad, J. Hoseini, Adv. Synth.
Catal. 2011, 353, 125–132; d) A. J. Amali, R. K. Rana, Green
Chem. 2009, 11, 1781–1786; e) R. L. Oliveira, P. K. Kiyohara,
L. M. Rossi, Green Chem. 2010, 12, 144–149; f) R. Luque, A.
Fihri, H. Zhu, J. M. Basset, Chem. Rev. 2011, 111, 3036–3075;
g) S. E. García-Garrido, J. Francos, V. Cadierno, J. M. Basset,
V. Polshettiwar, ChemSusChem 2011, 4, 104–111.
[1]
[2]
Y. Ono, Appl. Catal. A 1997, 155, 133–166.
J. P. Parrish, R. N. Salvatore, K. W. Jung, Tetrahedron 2000, 56,
8207–8237.
S. Gryglewicz, F. A. Oko, G. Gryglewicz, Ind. Eng. Chem. Res.
2003, 42, 5007–5010.
K. Takamatsu, T. Matsushita, JP 2003277327, 2003.
F. Mizia, F. Rivetti, US 20020056468, 2002.
[3]
[4]
[5]
[6] B. Sauerbrei, V. Jungmann, H. Waldmann, Angew. Chem. Int.
Ed. 1998, 37, 1143–1146; Angew. Chem. 1998, 110, 1187.
[7] a) G. Bertolini, G. Pavich, B. Vergani, J. Org. Chem. 1998, 63,
6031–6034; b) A. R. Choppin, J. W. Rogers, J. Am. Chem. Soc.
1948, 70, 2967.
[8] a) Y. Kishimoto, I. Ogawa, Ind. Eng. Chem. Res. 2004, 43,
8155–8162; b) B. M. Bhanage, S. I. Fujita, Y. Ikushima, K. To-
rii, M. Arai, Green Chem. 2003, 5, 71–75; c) J.-S. Tian, C.-X.
Miao, J.-Q. Wang, F. Cai, Y. Du, Y. Zhao, L.-N. He, Green
Chem. 2007, 9, 566–571.
[9] S. Fujita, B. M. Bhanage, Y. Ikushima, M. Arai, Green Chem.
2001, 3, 87–91.
[10] S. Carloni, D. E. De Vos, P. A. Jacobs, R. Maggi, G. Sartori,
R. Sartorio, J. Catal. 2002, 205, 199–204.
[11] B. Veldurthy, F. Figueras, Chem. Commun. 2004, 734–735.
[19] L. Q. Wu, Z. K. Yin, Eur. J. Inorg. Chem. 2013, 6156–6163.
[20] A. P. Polo, V. R. S. Quiteria, A. C. Canos, H. G. Gomez, R. J.
Marin, EP 2036884, 2009.
Received: December 18, 2013
Published Online: March 11, 2014
Eur. J. Inorg. Chem. 2014, 2080–2087
2087
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim