Star-like polyionic heterogeneous nanocatalyst as a highly active catalyst for promotion of Baylis-Hillman reaction in [bmim]Cl

Article abstract of DOI:10.1007/s13738-015-0694-9

The use of star-like polyionic Lewis base heterogeneous nanocatalyst for the Baylis-Hillman reaction of benzyl- and methylacrylates with aryl aldehydes has been investigated. The corresponding Baylis-Hillman adducts are obtained in good to high yields in

Full text of DOI:10.1007/s13738-015-0694-9

J IRAN CHEM SOC
DOI 10.1007/s13738-015-0694-9
ORIGINAL PAPER
Star‑like polyionic heterogeneous nanocatalyst as a highly active
catalyst for promotion of Baylis–Hillman reaction in [bmim]Cl
1
1
1
Hassan Valizadeh · Ashkan Shomali · Saeideh Noorshargh
Received: 22 March 2015 / Accepted: 30 June 2015
©
Iranian Chemical Society 2015
Abstract The use of star-like polyionic Lewis base het-
erogeneous nanocatalyst for the Baylis–Hillman reaction of
benzyl- and methylacrylates with aryl aldehydes has been
investigated. The corresponding Baylis–Hillman adducts
are obtained in good to high yields in one-pot procedure
at room temperature in 5.5–8 h. The catalyst can be eas-
ily recovered with excellent purity by filtration and can be
reused directly without any change in its catalytic activity.
PPh Me, which are difficult to isolate from the reaction
solution and reuse, have been used as the promoters in the
2
Baylis–Hillman reaction [10, 11]. Using of recyclable cata-
lyst has become the key factor for a chemical reaction to
be an economical, safe, environmentally benign, resource-
and energy-saving process [12]. It is very clear that if we
can design and synthesize a recyclable Lewis base as a
promoter for the Baylis–Hillman reaction, this would be
accomplished in a perfect atom-economic way.
Keywords Baylis–Hillman reaction · Star-like polyionic
compound · Heterogeneous nanocatalyst
Room temperature ionic liquids (ILs) have attracted
much attention in organic chemistry as reaction solvents
and catalysts (for reviews, see [13–15]), due to their low
volatility and many other advantages. Great rate accelera-
tions or good selectivity have been reported in the presence
of ILs [16]. However, in some cases, product and catalyst
isolation can be difficult in ILs [17]. Noting that Baylis–
Hillman reaction was accelerated in the presence of ILs
[18], we speculated that the Lewis base-tethered polyionic
compound can catalyze this reaction. Very recently, we
synthesized nitrite-functionalized star-like polyionic het-
erogeneous nanocatalyst and used as a nitrosonium source
and catalyst for the synthesis of azo dyes under solvent-free
conditions [19]. In this study, we synthesized Lewis base-
tethered star-like polyionic compound and investigated its
effect on Baylis–Hillman reactions of benzyl- and methyl
acrylates with aryl aldehydes in [bmim]Cl at room temper-
ature (Scheme 1).
Introduction
Baylis–Hillman reaction is one of the many important car-
bon–carbon bond-forming reactions which have been used
for the synthesis of natural products and biologically active
compounds [1–4]. Densely functionalized carbon skeleton
synthesis from the simple readily available α, β-unsaturated
carbonyl compounds and aldehydes in the presence of a
Lewis base catalyst is one of the significances of this trans-
formation. Despite great developments in this reaction,
including development of a catalytic, asymmetric version
and aza-Baylis–Hillman reactions, the need for alterna-
tive methods for the preparation of these novel synthesis
is still of great interest [5–9]. In general, small Lewis base
molecules, such as DABCO, DMAP, DBU, PPh , PBu or
3
3
Experimental
*
Hassan Valizadeh
hvalizadeh2@yahoo.com; h-valizadeh@azaruniv.edu
Materials and instrumentation
1
Organic Chemistry Research Lab, Department of Chemistry,
Faculty of Sciences, Azarbaijan Shahid Madani University,
PO Box 53714-161, Tabriz, Iran
All reagents were purchased from Merck Company
and used without further purification. Infrared spectra
1
3

J IRAN CHEM SOC
Scheme 1 Star-like polyionic
Lewis base heterogeneous
nanocatalyst for promotion of
Baylis–Hillman reaction
were recorded in KBr and determined on a Perkin Elmer
7 with 1,4-dichlorobutane and then with N,N,N′,N′-
tetramethylethylenediamine were carried out to produce
the desired star-like polyionic Lewis base heterogeneous
nanocatalyst 11. At the end of the reaction, the mixture was
stirred vigorously in acetonitrile at 40 °C for 3 h and then
centrifuged to provide the crude catalyst 11. FT-IR (KBr,
cm ): 3442 (Si–OH), 2958 (C–H), 1638 (O–H), 1486
(C–H), 1093 (asymmetric Si–O), 957 (asymmetric Si–OH),
800 (symmetric Si–O); EDX: Calcd.: N/C (%w) = 0.241;
Found (%): C, 9.47; N, 2.33; O, 46.49; Si, 40.43; Cl, 1.27.
N/C (%w) = 0.246; Anal. Calcd. Found (%): C, 17.76; N,
4.37; H, 4.24. N/C (%w) = 0.246.
1
13
FT-IR spectrometer. H-NMR and C-NMR spectra were
recorded on a Bruker Avance AC-300 MHz using CDCl3
as the deuterated solvent and TMS as the internal stand-
ard. The morphology of the catalyst was studied by field
emission scanning electron microscopy (FESEM; Hitachi,
model S-4160), and the structure of the catalyst was con-
firmed by energy-dispersive X-ray analysis (EDX; Tescan;
model MIRA3FEG-SEM) and elemental analysis (CHNS;
Euro EA; model EA2000).
−1
Synthesis of silica nanoparticles
Ammonia solution 25 % (750 µL, 10 mmol) and water
General procedure for the Baylis–Hillman adducts
using star‑like polyionic catalyst 11
(
1.98 mL) were added into a 250 mL round-bottom flask
containing absolute methanol (100 mL). The solution was
stirred for 10 min at room temperature. While stirring of
the solution, tetraethoxysilane (11 ml, 50 mmol) was added
dropwise. The final solution was stirred continuously for 3
days at ambient temperature. The particle size was exam-
ined under scanning electron microscopy. FT-IR (KBr,
Benzaldehyde derivative (10 mmol) and benzylacrylate
(10 mmol) or methylacrylate (10 mmol) were added to a
vessel containing [bmim]Cl (3 mL). Then, catalyst 11 was
added and the mixture was stirred at room temperature for
the times as shown in Table 3. After completion of the reac-
tion, the products were isolated and purified by column
chromatography using ethyl acetate/n-hexane as eluent.
−1
cm ): 3456 (Si–OH), 1639, 1097 (SiO–H), 803 (Si–OH).
Synthesis of star‑like polyionic Lewis base nanocatalyst
3
-Chloropropyltrimethoxysilane (1.82 ml, 10 mmol)
was reacted with N,N,N′,N′-tetramethylethylenediamine
1.94 ml, 13 mmol) in acetonitrile (5 mL) for 3 days at
0 °C to provide the ionic liquid 6. After completion of
Spectroscopic and analytical data
(
8
Benzyl 2‑(hydroxy(4‑nitrophenyl)methyl)acrylate (3a)
−1
the reaction, acetonitrile was evaporated and unreacted
diamine was extracted using dichloromethane, and the
crude ionic liquid 6 was achieved. Then, ionic liquid 6 was
immobilized on the freshly prepared nanosilica by stirring
FT-IR (KBr, cm ): 3480, 2986, 1719, 1629, 1606, 1520,
1
1348, 1245. H NMR (CDCl , 300 MHz) δ 8.15 (d,
3
J = 8.6 Hz, 2H), 7.49 (d, J = 8.6 Hz, 2H), 7.24-7.12 (m,
5H), 6.54 (s, 1H), 5.89 (s, 1H), 5.59 (s, 1H), 5.11 (s, 2H),
°
13
of these two compounds in acetonitrile at 60 C for 3 days
3.37 (br s, 1H). C NMR (CDCl , 75 MHz) δ 165.61,
3
to produce the ionic liquid-immobilized nanosilica 7. As
shown in Scheme 1, successive reactions of compound
148.67, 147.31, 141.16, 135.11, 128.51, 128.40, 128.10,
127.37, 127.22, 123.46, 72.22, 66.77. Anal. Calc. for
1
3

J IRAN CHEM SOC
C H NO : C 65; H 4.79; N 4.47 %. Found: C 64.88; H
Benzyl 2‑((4‑formylphenyl)(hydroxy)methyl)acrylate
(3f)
1
7
15
5
4
.65; N 4.59 %.
−
1
Benzyl 2‑((4‑cyanophenyl)(hydroxy)methyl)acrylate
3b)
FT-IR (KBr, cm ): 3461, 2962, 17, 1632, 1608, 1262.
1
(
H NMR (CDCl , 300 MHz) δ 10.00 (s, 1H), 7.85 (d,
3
J = 8 Hz, 2H), 7.55 (d, J = 8 Hz, 2H), 7.34 (m, 3H), 7.27
−
1
FT-IR (KBr, cm ): 3479, 2993, 2231, 1714, 1633, 1608,
(m, 2H), 6.44 (s, 1H), 5.89 (s, 1H), 5.64 (s, 1H), 5.16 (s,
1
13
1
2
245. H NMR (CDCl , 300 MHz) δ 7.60 (d, J = 8.3 Hz,
2H), 3.1 (s, 1H). C NMR (CDCl , 75 MHz) δ 165.719,
3
3
H), 7.48 (d, J = 8.3 Hz, 2H), 7.37–7.27 (m, 5H), 6.45
146.58, 141.05, 135.14, 132.24, 128.54, 128.23, 127.42,
127.25, 118.74, 111.55, 72.85, 66.96. Anal. Calc. for
C H O : C 72.97; H 5.40 %. Found: C 72.99; H 5.39 %.
(
1
s, 1H), 5.89 (s, 1H), 5.60 (s, 1H), 5.17 (s, 2H), 3.23 (s,
1
3
H). C NMR (CDCl , 75 MHz) δ 160.87, 148.72, 142.54,
3
18 16
4
1
31.66, 128.71, 127.59, 119.48, 113.92, 73.73, 53.83. Anal.
Calc. for C H NO : C 73.72; H 5.11; N 4.77 %. Found: C
Benzyl 2‑(hydroxy(phenyl)methyl)acrylate (3g)
1
8
15
3
7
3.24; H 5.16; N 4.58 %.
−1
1
FT-IR (KBr, cm ): 3453, 2950, 1719, 1632, 1439. H
Benzyl 2‑(hydroxy(4‑(trifluoromethyl)phenyl)methyl)
acrylate (3c)
NMR (CDCl , 300 MHz) δ 7.23-7.41 (m, 5H), 7.22-7.09
3
(m, 5H), 6.54 (s, 1H), 5.89 (s, 1H), 5.62 (s, 1H), 5.17 (s,
1
3
2
H), 3.31 (br s, 1H). C NMR (CDCl , 75 MHz) δ 150.24,
3
−1
1
FT-IR (KBr, cm ): 3461, 2961, 1714, 1620, 1261. H
140.15, 137.13, 132.13, 123.42, 119.21, 116.71, 114.21,
112.23, 109.13, 101.59, 55.22, 46.78. Anal. Calc. for
C H O : C 76.69; H 6.01 %. Found: C 76.61; H 6.04 %.
NMR (CDCl , 300 MHz) δ 7.61 (d, J = 8.4 Hz, 2H),
3
7
5
.51 (d, J = 8.4 Hz, 2H), 7.35-7.25 (m, 5H), 6.45 (s, 1H),
1
7
16
3
13
.89 (s, 1H), 5.62 (s, 1H), 5.17 (s, 2H), 3.13 (s, 1H).
C
NMR (CDCl , 75 MHz) δ 188.23, 171.76, 155.62, 141.52,
Methyl 2‑(hydroxy(4‑nitrophenyl)methyl)acrylate (3h)
3
1
36.56, 129.60, 125.49, 123.28, 113.82, 72.63, 58.26. Anal.
−
1
Calc. for C H F O : C 64.29; H 4.46 %. Found: C 64.28;
H 4.39 %.
FT-IR (KBr, cm ): 3423, 2960, 1718, 1609, 1525, 1348,
1
8
15
3
3
1
1263. H NMR (CDCl , 300 MHz) δ 8.30 (d, J = 8.1 Hz,
3
2
H), 8.20 (d, J = 8.1 Hz, 2H), 6.76 (s, 1H), 5.78 (s, 1H),
13
Benzyl 2‑(hydroxy(3‑nitrophenyl)methyl)acrylate (3d)
5.90 (s, 1H), 3.98 (s, 3H), 3.13 (s, 1H). C NMR (CDCl ,
3
7
5 MHz) δ 188.23, 171.76, 155.62, 141.52, 136.56, 129.60,
−
1
13
FT-IR (KBr, cm ): 3489, 2961, 1714, 1631, 1531, 1351,
125.49, 123.28, 113.82, 72.63, 58.26. C NMR (CDCl3,
75 MHz) δ 173.13, 154.27, 150.21, 139.18, 130.14, 121.25,
120.34, 72.79, 49.14. Anal. Calc. for C H NO : C 55.69;
1
1
265. H NMR (CDCl , 300 MHz) δ 8.25 (s, 1H), 8.15 (d,
3
J = 7.9 Hz, 1H), 7.73 (d, J = 7.9 Hz, 1H), 7.51 (t, 1H),
1
1
11
4
7
5
1
1
.36–7.27 (m, 5H), 6.48 (s, 1H), 5.95 (s, 1H), 5.66 (s, 1H),
H 4.64; N 5.90 %. Found: C 55.68; H 4.61; N 5.89 %.
1
3
.17 (s, 2H), 3.23 (s, 1H). C NMR (CDCl , 75 MHz) δ
65.67, 148.32, 143.55, 141.00, 135.11, 132.65, 128.63,
28.52, 128.22, 127.53, 122.78, 121.60, 72.65, 67.00. Anal.
3
Methyl 2‑((4‑cyanophenyl)(hydroxy)methyl)acrylate
(3i)
Calc. for C H NO : C 65; H 4.79; N 4.47 %. Found: C
1
7
15
5
−
1
6
4.98; H 4.76; N 4.48 %.
FT-IR (KBr, cm ): 3465, 2986, 2235, 1716, 1629, 1619,
1
1
252. H NMR (CDCl , 300 MHz) δ 7.59 (d, J = 8.2 Hz,
3
Benzyl 2‑(hydroxy(2‑nitrophenyl)methyl)acrylate (3e)
2H), 7.45 (d, J = 8.2 Hz, 2H), 6.44 (s, 1H), 5.89 (s, 1H),
1
3
5
.62 (s, 1H), 3.57 (s, 3H), 3.23 (br s, 1H). C NMR
−1
FT-IR (KBr, cm ): 3437, 2964, 1715, 1634, 1610, 1528,
(CDCl , 75 MHz) δ 167.77, 146.62, 141.44, 130.23,
126.81, 125.39, 117.38, 111.82, 71.62, 50.63. Anal. Calc.
for C H NO : C 66.36; H 5.07; N 6.45 %. Found: C
3
1
1
350, 1247. H NMR (CDCl , 300 MHz) δ 7.95 (d,
3
J = 8.1 Hz, 1H), 7.82 (d, J = 8.1 Hz, 1H), 7.65 (t, 1H), 7.44
1
2
11
3
(
t, 1H), 7.35–7.10 (m, 5H), 6.45 (s, 1H), 6.22 (s, 1H), 5.80
66.34; H 5.11; N 6.46 %.
(
s, 1H), 5.22 (d, J = 12.1 Hz, 1H), 5.11 (d, J = 12.1 Hz,
1
3
1
1
1
H), 3.43 (s, 1H). C NMR (CDCl , 75 MHz) δ 165.71,
Methyl 2‑(hydroxy(3‑nitrophenyl)methyl)acrylate (3j)
3
40.56, 136.12, 135.32, 133.55, 128.89, 128.74, 128.58,
28.34, 128.09, 126.93, 124.67, 67.77, 66.85. Anal. Calc.
−1
FT-IR (KBr, cm ): 3479, 2959, 1717, 1630, 1528, 1341,
1
for C H NO : C 65; H 4.79; N 4.47 %. Found: C 64.99;
1258. H NMR (CDCl , 300 MHz) δ 8.27 (s, 1H), 8.16 (d,
1
7
15
5
3
H 4.79; N 4.48 %.
J = 8.4 Hz, 1H), 7.76 (d, J = 8.4 Hz, 1H), 7.54 (t, 1H),
1
3

J IRAN CHEM SOC
Scheme 2 Synthesis of
star-like polyionic Lewis base
catalyst
6
.43 (s, 1H), 5.92 (s, 1H), 5.65 (s, 1H), 3.76 (s, 3H), 3.31
Methyl 2‑(hydroxy(4‑(trifluoromethyl)phenyl)methyl)
acrylate (3m)
1
3
(
s, 1H). C NMR (CDCl , 75 MHz) δ 172.14, 149.31,
3
1
7
42.28, 137.23, 131.18, 130.26, 122.71, 120.61, 119.52,
2.51, 49.32. Anal. Calc. for C H NO : C 55.69; H 4.64;
−1
1
FT-IR (KBr, cm ): 3465, 2958, 1718, 1616, 1259. H
1
1
11
4
N, 5.90 %. Found: C 5567; H 4.48; N 5.91 %.
NMR (CDCl , 300 MHz) δ 7.71 (d, J = 8.3 Hz, 2H),
3
7
.53 (d, J = 8.3 Hz, 2H), 6.45 (s, 1H), 5.77 (s, 1H), 5.69
13
Methyl 2‑((4‑formylphenyl)(hydroxy)methyl)acrylate
(s, 1H), 5.36 (s, 1H), 3.60 (s, 3H), 3.14 (br s, 1H).
C
(
3k)
NMR (CDCl , 75 MHz) δ 187.29, 170.88, 156.74, 140.63,
3
1
36.47, 128.68, 114.76, 71.68, 56.46. Anal. Calc. for
−
1
FT-IR (KBr, cm ): 3436, 2963, 1744, 1705, 1630, 1608,
1
C H FO : C 55.38; H 4.23 %. Found: C 55.34; H 4.28 %.
1
2
11
3
1
247. H NMR (CDCl , 300 MHz) δ 10.02 (s, 1H), 7.89
3
(
d, J = 8.1 Hz, 2H), 7.55 (d, J = 8.1 Hz, 2H), 6.39 (s, 1H),
5
1
1
.87 (s, 1H), 5.63 (s, 1H), 5.65 (s, 1H), 3.76 (s, 3H), 3.24 (s,
Results and discussion
1
3
H). C NMR (CDCl , 75 MHz) δ 175.23, 160.66, 142.42,
3
40.38, 131.28, 130.33, 119.23, 114.62, 71.51, 52.46. Anal.
Star-like polyionic Lewis base catalyst 11 was prepared
via several successive steps in acetonitrile in good yield
(Scheme 2). At first, (3-chloropropyl)-trimethoxysilane was
reacted with N,N N′,N′-tetramethylethylenediamine at 80 °C
for 3 days to afford the ionic liquid 6. Then, immobiliza-
tion of ionic liquid 6 on freshly prepared nanosilica was car-
ried out according to the literature [20] and led to the ionic
liquid immobilized nanosilica 7. As shown in Scheme 2,
increasing the length of the ionic chain of compound 7 was
achieved via the four subsequent reactions with 1,4-dichlo-
robutane and N,N,N′,N′-tetramethylethylenediamine to
provide the Lewis base-tethered star-like polyionic nano-
catalyst 11. The structure of the catalyst was confirmed by
FT-IR spectrometry, FE-SEM, EDX and CHNS analysis.
Calc. for C H O : C 65.45; H 5.45 %. Found: C 65.47; H
1
2
12
4
5
.45 %.
Methyl 2‑(hydroxy(2‑nitrophenyl)methyl)acrylate (3 l)
−1
FT-IR (KBr, cm ): 3433, 2965, 1719, 1631, 1609, 1530,
1
1
375, 1261. H NMR (CDCl , 300 MHz) δ 7.93 (d,
3
J = 8.3 Hz, 1H), 7.86 (d, J = 8.3 Hz, 1H), 7.59 (t, 1H),
7
3
1
6
.48 (t, 1H), 6.49 (s, 1H), 6.28 (s, 1H), 5.83 (s, 1H), 3.72 (s,
1
3
H), 3.14 (br s, 1H). C NMR (CDCl , 75 MHz) δ 163.32,
3
44.15, 143.13, 132.24, 127.32, 120.41, 117.13, 113.34,
3.42, 50.59. Anal. Calc. for C H NO : C 55.69; H 4.64;
1
1
11
4
N 5.90 %. Found: C 55.67; H 4.64; N 5.87 %.
1
3

J IRAN CHEM SOC
Fig. 1 a FE-SEM image of
nanosilica. b FE-SEM image
of polyionic immobilized
nanosilica. c FT-IR spectra of
nanosilica and polyionic immo-
bilized nanosilica
Fig. 2 a EDX analysis of ionic immobilized nanosilica 7. b EDX analysis of polyionic immobilized nanosilica 11
Immobilization was confirmed by FE-SEM image and
FT-IR spectrometry of the product. Particle sizes in FE-
SEM images of nanosilica and the ionic liquid-immobi-
lized nanosilica were 30 and 60 nm, respectively (Fig. 1a,
b). The signal at 1488 cm in the FT-IR spectrum of poly-
ionic-immobilized nanosilica was related to the C–H bond
and this signal was absent in the FT-IR spectrum of nano-
silica (Fig. 1c). The existence of elements C, N, Si, Cl and
O in polyionic immobilized nanosilica was confirmed and
analyzed by EDX and CHNS analysis (Fig. 2). Measuring
of N:C ratio in compounds 7, 9 and 11 by CHNS analy-
sis showed that this ratio was decreased by the growth of
the polyionic chain. Immobilization of the polyionic com-
pound on nanosilica was also confirmed by comparison
of N:C ratio in two structures. Comparison of theoretical
N:C ratio (0.259) with the elemental analyzed experimental
−
1
1
3

J IRAN CHEM SOC
Table 1 Different conditions for the synthesis of product 3g
Catalyst number Reaction time (h) Yield (%)a
Entry Solvent
temperature. The model reaction proceeded smoothly
to give a 75 % yield of 3g after 7 h under these condi-
tions. By varying the amount of catalyst 11 with respect
to benzaldehyde, we also obtained the optimum amount
of catalyst. It was found that the yield of the product
increased with the catalyst varying from 0.05 to 0.10
ratios. The yield was not increased when more amount
of catalyst was employed.
Under the optimized reaction conditions, we exam-
ined the recovery of catalyst 11. When the reaction was
completed, the catalyst was very simply recovered by
washing all the soluble organic materials, reactants and
products by ethyl acetate as eluent. The catalyst could
be obtained with high recovery >90 % in each cycle.
Meanwhile, high yield of 68–72 % of the model reac-
tion could be obtained, mediated by the recovered cata-
lyst within three cycles. It showed that catalyst 11 could
be well recycled without remarkable loss of reaction
activity.
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
CHCl3
6
6
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
7
15
10
20
15
29
26
38
40
35
52
55
2
CHCl3
2
CH Cl2
7
CH Cl2
7
CHCl3
9
CH Cl2
9
2
CHCl3
11
11
7
CH Cl2
2
CH CN
3
0
1
2
3
4
5
6
CH CN
9
3
CH CN
11
3
[bmim]Cl
[bmim]Cl
[bmim]Cl
[bmim]Cl
–
–
6
7
9
–
48
65
75
[bmim]Cl 11
Isolated yield
The generality of this promising reaction was evalu-
ated by employing a variety of benzaldehyde deriva-
tives with (phenyl or methyl) acrylate. The correspond-
ing results are shown in Table 2. As seen in Table 2, the
reaction proceeded smoothly to afford the correspond-
ing adducts in good to excellent yields for aromatic
aldehydes bearing electron-withdrawing substituents.
Benzaldehydes containing electron-donating groups,
such as 4-OMe, 2-OMe and 4-Me did not react under
optimized conditions. We examined this procedure on a
20 mmol scale and found that they underwent a smooth
transformation to the related Baylis–Hillman adducts
in good yields, suggesting that the present procedure
is amenable to scale-up. The reaction of terephthala-
ldehyde with benzyl- and methyl acrylate was exam-
ined and found that only one aldehyde group of tere-
phthalaldehyde reacted in this procedure. The products
a
ratio (0.258) of product 7 also confirmed the structure of
this compound. Also, comparison of theoretical N:C ratio
(
(
0.241) with the elemental analyzed experimental ratio
0.246) of immobilized catalyst 11 also confirmed the
structure of this compound. As it was cleared from ele-
mental analysis data, the N:C ratio was more decreased by
growth of ionic chain [19].
We first carried out a model reaction involving ben-
zaldehyde, benzyl acrylate and a Lewis base catalyst 7,
9
or 11 (Scheme 2) to optimize reaction conditions. As
shown in Table 1, different conditions were examined
for optimization of the model reaction. The reaction
was examined in ionic liquid 6 as a reaction medium
and Lewis base catalyst. On monitoring of the reac-
tion by TLC, no significant progress in the reaction was
observed after 7 h at 80 °C (Table 1; entry 13). This pro-
cess was also examined in the presence of compounds
1
13
were characterized by H-NMR and C-NMR spectra
and CHNS analysis. The comparison of their yields
and reaction times with the reported value is shown in
Table 3.
7
, 9 or 11 as heterogeneous Lewis base nanocatalysts
in acetonitrile at 80 °C. The yield obtained in the pres-
ence of these catalysts was much higher than it was in
the absence of the catalyst. These reactions gave prod-
uct 3g of 35, 52 and 60 %, respectively, after 7 h (based
on benzaldehyde). This shows that the performance of
catalyst 11 was better than catalysts 7 or 9. In addi-
tion, the length of ionic chain had a pronounced effect
on the yield. The yield was not increased at higher tem-
peratures and in other organic solvents (Table 1; entries
Conclusion
In summary, a kind of star-like polyionic Lewis base
heterogeneous nanocatalyst could effectively accelerate
the Baylis–Hillman reaction of aromatic aldehydes with
(methyl or phenyl) acrylate. The catalyst could be easily
recovered for reuse. Application of this catalyst for other
reactions is under investigation and will be reported in due
course.
1
–11). Excellent yields were obtained when employing
catalyst 11 in [bmim]Cl as the reaction medium at room
1
3

J IRAN CHEM SOC
Table 2 Baylis–Hillman
reaction using star-like
polyionic nanocatalyst
Product
number
Entry
1
R
1
R
2
Product
CH
2
Ph
Ph
Ph
4-NO
2
3a
3b
3c
2
3
CH
2
2
4-CN
CH
4-CF
3
4
5
6
CH
CH
CH
2
Ph
2
Ph
2
Ph
3-NO
2-NO
2
2
3d
3e
3f
4-CHO
7
8
CH
2
Ph
H
3g
3h
Me
Me
4-NO
2
9
4-CN
3i
1
3

J IRAN CHEM SOC
Table 2 continued
Product
number
Entry
Acrylate
Me
Benzaldehyde
Product
1
1
1
0
1
2
3-NO
2
3j
3k
3l
Me
Me
4-CHO
2-NO
2
1
3
Me
4-CF
3
3m
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1
2
3
.
.
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Found Reported Found Reported
2
1
2
3
4
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6
7
8
9
1
1
1
1
3a
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10
96
87
89
89
90
78
75
90
88
87
72
85
83
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–
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8
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a
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1
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Acknowledgments The partial financial assistance from the
Research Vice Chancellor of Azarbaijan Shahid Madani University is
gratefully acknowledged.
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