Sh

Ra

b

a

ARRA

KCCCS

1

vpcaaNorcBetttTnahog

Sf

k

0d

Materials Chemistry and Physics 125 (2011) 784–790

Contents lists available at ScienceDirect

Materials Chemistry and Physics

journa l homepage: www.e lsev ier .com/ locate /matchemphys

ynthesis and characterization of PVAm/SBA-15 as a novel organic–inorganicybrid basic catalyst

oozbeh Javad Kalbasia,b,∗, Majid Kolahdoozana,b, Mahsa Rezaeia,b

Department of Chemistry, Islamic Azad University, Shahreza Branch, 311-86145, Shahreza, Isfahan, IranRazi Chemistry Research Center, Islamic Azad University, Shahreza Branch, Shahreza, Isfahan, Iran

r t i c l e i n f o

rticle history:eceived 23 March 2010

a b s t r a c t

Composite polyvinyl amine/SBA-15 (PVAm/SBA-15) in various amounts of SBA-15 were prepared andcharacterized. The physical and chemical properties of PVAm/SBA-15 were investigated using FT-IR,

eceived in revised form 11 June 2010ccepted 23 September 2010

eywords:omposite materialshemical synthesis

XRD, BET, SEM and TGA techniques. The catalytic performance of each material was determined forthe Knoevenagel condensation reaction between carbonyl compounds and ethyl cyanoacetate in thepresence of ethanol as solvent. The effects of reaction temperature, solvent and the amounts of catalystas well as recyclability of the catalyst were investigated. The catalyst used for this synthetically usefultransformation showed a considerable degree of reusability besides being very active.

hemical techniquesurface properties

. Introduction

The Knoevenagel condensation reaction is well known for itsast potential for the synthesis of �,�-unsaturated carbonyl com-ounds from active methylene and carbonyl compounds. Theatalysts traditionally used are ammonia, primary or secondarymines and their salts [1]. In recent years, a wide range of cat-lysts, such as TiCl4 [2], MgO [3], ZnCl2 [4] NbCl5 [5], MgF2 [6]a2CaP2O7 [7] chitosan [8], ionic liquids containing imidazole [9]r guanidinium group [10], have been employed to catalyze thiseaction with each affording variable yields of �,�-unsaturatedarbonyl compounds in solution or under solvent-free conditions.ut there were a lot of disadvantages to these new catalysts. Forxample, when using the Lewis acidic catalysts, TiCl4 and ZnCl2,he reaction conditions should be free from water. In addition,hese catalysts are not stable and cannot be re-used because ofhe water produced from the Knoevenagel reaction itself [11,12].he past decade has seen significant advances in the synthesis ofew periodical mesoporous and crystalline microporous materi-

ls [13]. Recently, the design and preparation of organic–inorganicybrid catalysts based on these materials have gained great degreef interest [14]. They are becoming as important as the hetero-eneous catalysts particularly for the synthesis of fine-chemicals

∗ Corresponding authors at: Department of Chemistry, Islamic Azad University,hahreza Branch, 311-86145, Shahreza, Isfahan, Iran. Tel.: +98 321 3292072;ax: +98 321 3293095.

E-mail addresses: rkalbasi@iaush.ac.ir, rkalbasi@gmail.com (R.J. Kalbasi),olahdoozan@iaush.ac.ir (M. Kolahdoozan).

254-0584/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.matchemphys.2010.09.058

© 2010 Elsevier B.V. All rights reserved.

in liquid phase at lower temperatures. Additionally, the heteroge-neous catalysis is obviously advantageous in the light of the catalystrecovery and eco-benignity. However, solid-based catalysis, par-ticularly on microporous and mesoporous materials [15], is stillless investigated than the corresponding acid catalysis. Examples ofsolid base-catalyzed C–C bond forming reactions, such as Knoeve-nagel condensation [16–18], aldol condensation [19], and Michaeladdition [20], have been well documented [21].

The hybrid materials could be obtained by the combin-ing organic polymers with inorganic materials [22]. Theseorganic–inorganic hybrid materials could be prepared by vari-ous methods, depending on what kind of interaction is employedbetween organic polymers and inorganic elements or on howorganic moieties are introduced to the inorganic phases. Utiliza-tion of physical interaction or covalent bonds between the twophases are examples of effective methods of obtaining hybridmaterials. An in situ polymerization, which is the simultaneouspolymerization of both organic monomer and inorganic precursor,is another important method for preparation of composite mate-rials without physical or chemical interaction. Inorganic–organichybridization for surface functionalization of mesoporous silicawith organic groups is important for practical applications in catal-ysis and adsorption owing to the inert nature of the amorphoussilica surface [23]. Surface modification by polymers is found tobe one of the most effective methods, as the surface properties

that can be widely changed by a variety of functional polymers.Functional polymers are macromolecules to which chemicallyfunctional groups are attached; they have the potential advan-tages of small molecules with the same functional groups. Probablythe most important advantage in using a composite functionalized

R.J. Kalbasi et al. / Materials Chemistry and Physics 125 (2011) 784–790 785

H2C CH

C O THF

SBA-15H2O

SBA-15nbenzoyl peroxide

Ca(OCl)2SBA-15CH2 CH

C On

CH2 CH

NH2n

ation

pwopa4paTpbm[

sSiia

2

2

t

2

K4Bpa1

r6at

2

2

l(tbwra

2

bta(t1

2

if

NH2 NH2

Scheme 1. Prepar

olymer as a reagent or a catalyst is the simplification of productork-up, its separation and isolation with high reactivity. On the

ther hand, supports show an important role in the activity of com-osites. Some of the best supports with a wide surface and catalyticctivity are SBA-15 and MCM-41. Mesoporous silicas, such as MCM-1 and SBA-15, are solid materials, composed of a honeycomb-likeorous structure with hundreds of empty channels (mesopores)ble to absorb/encapsulate relatively large amounts of molecules.he unique properties, such as high surface area (>900 m2/g), largeore volume (>0.9 cm3/g), tunable pore size with a narrow distri-ution (2–10 nm), and good chemical and thermal stability of theseaterials make them potentially suitable for various applications

24].In this research, we have focused our attention on the synthe-

is and characterization of polyvinyl amine (PVAm) supported byBA-15 and the application of this composite as a basic catalystn organic synthesis. The basic properties of this new polymericnorganic catalyst were tested for Knoevenagel condensation ofromatic aldehydes with ethyl cyanoacetate in ethanol.

. Experimental

.1. General information

All chemicals were obtained from Sigma–Aldrich, Merck and used without fur-her purification.

.2. Instruments and characterization

The catalyst was characterized by: X-ray diffraction (Bruker D8ADVANCE,Cu� radiation), FT-IR spectroscopy (Nicolet 400D in KBr matrix in the range of000–400 cm−1), BET specific surface areas and BJH pore size distribution (SeriesEL SORP 18, at 77 K), thermal analyzer TGA (Setaram Labsys TG (STA) in a tem-erature range of 30–700 ◦C and heating rate of 10 ◦C min−1 in N2 atmosphere)nd SEM (Philips, XL30, SE detector). The products were identified by 1H NMR and3C NMR spectra (Bruker DRX-500 Avance spectrometer at 500.13 and 125.47 MHz,espectively), GC (Agilent 6820 equipped with a FID detector) and GC-MS (Agilent890). The melting points were measured on an electro-thermal 9100 apparatusnd reported without correction. The melting points compared satisfactorily withhose reported in the literature.

.3. Catalyst synthesis

.3.1. Synthesis of SBA-15Mesoporous silica SBA-15 was prepared by a novel method described in the

iterature [25]. Pluronic P123 (2 g) was dissolved at room temperature in H3PO4

4.16 mL, 85%) and deionized water (75.37 mL), then TEOS (4.58 mL) was added tohe solution and synthesis carried out by stirring at 35 ◦C for 24 h in sealed teflonreakers and subsequently placed at 100 ◦C for 24 h. Then, the solution was filtered,ashed with deionized water, and finally dried at 95 ◦C for 12 h in air. Template

emoval was performed by calcination in air using two successive steps; first heatingt 250 ◦C for 3 h and then at 550 ◦C for 4 h.

.3.2. Preparation of polyacryl amide/SBA-15SBA-15 (0.5 g) and acryl amide (0.25 g) in THF (7 mL) were placed in a round

ottom flask. Benzoyl peroxide (0.025 g) was added and the mixture was heatedo 70–75 ◦C for 5 h while stirring. The solvent was removed and the mixture driedt 60 ◦C overnight under vacuum to gain 0.7 g of white powder of polyacryl amidePAA)/SBA-15 composite. The FT-IR spectrum of the polymer composite showedhe characteristic absorption of amide (N–H) at 1436 cm−1 and SBA-15 (Si–O) at

−1

080 cm .

.3.3. Preparation of polyvinyl amine/SBA-15PAA/SBA-15 (0.1 g), H2O (15 mL), Ca(OCl)2 (0.4 g) and stirring bar were placed

nto a round bottom flask. The stirrer was started and the mixture was refluxedor 6 h. It was then filtered, washed with water, n-hexane and finally dried at

of PVAm/SBA-15.

60 ◦C overnight under vacuum to yield the yellow polyvinyl amine (PVAm)/SBA-15 composite. The weight of the yellow product was 0.89 g. The FT-IR spectrum ofthe PVAm/SBA-15 composite showed the characteristic absorption of (N–H) aminogroup at 1434 cm−1and SBA-15 (Si–O) at 1080 cm−1 respectively The amine contentof PVAm/SBA-15 composite was estimated by back-titration using NaOH. 5 mL ofHCl (0.2 N) was added to 0.05 g of this composite and stirred for 30 min. The catalystwas removed and washed successively with deionized water. The excess amountof HCl was titrated with NaOH (0.1 N) in the presence of phenolphthalein as anindicator. The amine content of catalysts was 13.80 mequiv. g−1.

2.4. General procedure for Knoevenagel condensation

In a typical procedure, a mixture of benzaldehyde (2 mmol), ethyl cyanoacetate(2 mmol) and modified PVAm/SBA-15 (0.12 g) in ethanol (10 mL) was placed in around bottom flask. The suspension was stirred at 78 ◦C for 2 h. Completion of thereaction was monitored by TLC, using n-hexane/THF (16:4) as eluent. For the reac-tion work-up, the mixture was cooled to 10 ◦C, for solidification of the product. Thecatalyst was removed by filtration and washed with hot ethanol. The solvent wasevaporated and a pure product was obtained. The product was identified using 1HNMR, 13C NMR, GC–Mass and FT-IR spectroscopy techniques. Quantitative analyseswere conducted with an Agilent 6820 GC equipped with a FID detector. An Isolatedyield was obtained by using column chromatography, in addition to GC yield. Decanewas added as an internal standard for GC analysis. The catalyst was recovered andre-used in the reaction of ethyl cyanoacetate with benzaldehyde four times. In addi-tion, the selectivity (100% to �,�-unsaturated carbonyl compounds), and yield (90%),did not change with the re-used catalyst.

3. Results and discussion

3.1. Reaction processes used in order to prepare catalystPVAm/SBA-15

PAA/SBA-15 composite was obtained by polymerization of acry-lamide in the presence of SBA-15 using benzoyl peroxide asan initiator. Hoffmann degradation on PAA/SBA-15 was done byCa(OCl)2 in order to prepare PVAm/SBA-15 composite. The aminecontents of this composite was determind using acid–base titra-tion method. The preparation procedure of PVAm/SBA-15 is givenin Scheme 1.

3.2. Characterization of the catalyst

Fig. 1 shows the FT-IR spectra of mesoporous silica SBA-15,PVAm and PVAm/SBA-15. The characteristic band at 1080 cm−1

is due to the Si–O stretching in Si–O–Si structure, which is seenin Fig. 1a and c. In the FT-IR spectrum of PVAm/SBA-15 (Fig. 1c),the new band at 1436 cm−1 is the bending vibration absorptionof the N–H bond. In the FT-IR spectrum of PVAm/SBA-15 (Fig. 1c),the peak at 3450 cm−1 is stronger than FT-IR spectrum of SBA-15(Fig. 1a), shown due to the stretching vibration of the N–H groups.Moreover, the presence of peaks at around 2800–3000 cm−1 corre-sponds to the aliphatic C–H stretching in PVAm/SBA-15. These arein accordance with the spectrum of PVAm (Fig. 1b).

The appearance of the above bands shows that PVAm wasattached to the surface of SBA-15 and the PVAm/SBA-15 compositewas obtained.

The power of the XRD pattern of mesoporous silica SBA-15 and

PVAm/SBA-15 is shown in Fig. 2. Typically, the low angle diffractionpattern shows evidence of three reflections at 2� values of 0.5–3◦,including one strong peak (1 0 0) and two weak peaks (1 1 0) and(2 0 0), corresponding to a highly ordered hexagonal mesoporoussilica framework [24]. The PVAm/SBA-15 sample showed the same

786 R.J. Kalbasi et al. / Materials Chemistry and Physics 125 (2011) 784–790

F1

pwisTts

F1

ig. 1. FT-IR spectra of (a) mesoporous silica SBA-15, (b) PVAm and (c) PVAm/SBA-5.

attern, indicating that the long-range order of the SBA-15 frame-ork was well retained after the immobilization. However, the

ntensity of the characteristic reflection peaks of the PVAm/SBA-15

ample is found to be reduced, indicating loss of long-range order.his may be attributed to the symmetry destroyed by the hybridiza-ion of SBA-15, which was also found in the ordered mesoporousilica loading with guest matter. Furthermore, the prominent peak

ig. 2. The powder XRD pattern of (a) mesoporous silica SBA-15 and (b) PVAm/SBA-5.

Fig. 3. The N2 adsorption-desorption isotherm of (a) pure SBA-15 and (b)PVAm/SBA-15.

(1 0 0) of PVAm/SBA-15 sample shifts to lower angles comparedwith mesoporous silica SBA-15.

The N2 adsorption–desorption isotherms of pure SBA-15 andPVAm/SBA-15 samples are shown in Fig. 3. The isotherms are sim-ilar to Type IV isotherm with H1-type hysteresis loops at highrelative pressure according to the IUPAC classification, characteris-tic of mesoporous materials with highly uniform size distributions.From the two branches of adsorption–desorption isotherms, thepresence of a sharp adsorption step in the P/P0 region from 0.6 to0.8 and a hysteresis loop at the relative pressure P/P0 > 0.7 showsthat the materials process a well defined array of regular meso-porous. The specific area and the pore size have been calculatedusing Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda(BJH) methods, respectively. The structure data of all these meso-porous materials (BET surface area, total pore volume, and pore size,etc.) were summarized in Table 1. It is clear that calcined SBA-15 hasa high BET surface area (1430 m2/g), a large pore volume (1.9 cm3/g)and a pore size (9.9 nm), indicative of its potential application as ahost in organic materials. After hybridization with PVAm throughin situ polymerization, PVAm/SBA-15 exhibits a smaller specificarea, pore size and pore volume in comparison with those of pureSBA-15, which might be due to the presence of polymer on the sur-face of the SBA-15. Although these textural properties are smallerthan those found for mesoporous silica SBA-15, PVAm/SBA-15 stillhas mesoporous form and does not block the pores of the SBA-15, hence suitable to function as a basic catalyst for Knoevenagel

condensation.

Fig. 4 gives the scanning electron microscopy (SEM) pho-tographs of SBA-15 and PVAm/SBA-15. It is obvious that beforehybridization, the surface of SBA-15 is somewhat coarse and irreg-ular, whereas after hybridization, the surface of SBA-15 becomes

Table 1Porosity data of mesoporous silica SBA-15 and PVAm/SBA-15 samples.

Sample BET surfacearea (m2 g−1)

VP (cm3 g−1) DP (nm)

Mesoporous silica SBA-15 1430 1.90 9.90PVAm/SBA-15 856 1.08 8.81

R.J. Kalbasi et al. / Materials Chemistry and Physics 125 (2011) 784–790 787

graph

sP

NacP(tol

Fig. 4. Scanning electron microscopy (SEM) photo

mooth. These results show that surfaces of SBA-15 are filled withVAm.

Fig. 5 shows the TGA curves of PVAm and PVAm/SBA-15 under2 atmosphere. The weight loss (around 34%, w/w) of PVAm beginst 150 ◦C because of the thermo-degradation of PVAm polymerhains and the degradation ends at 550 ◦C (Fig. 5a); whereas for theVAm/SBA-15 sample we can see two separate weight loss steps

Fig. 5b). The first (around 2%, w/w) step appearing at tempera-ure <150 ◦C corresponding to loss of water (i.e., adsorbed watern the inner and outer surfaces of SBA-15). The second weightoss (about 475–600 ◦C) amounts to around 6% (w/w) which is

Fig. 5. TGA curves of (a) PVAm/SBA-15 and (b) PVAm.

s of (a and b) SBA-15 and (c and d) PVAm/SBA-15.

related to the degradation of the polymer. Compared to the PVAmcurve, the weight loss of PVAm/SBA-15 is mild, and indicates thatPVAm/SBA-15 is more thermo-stable than PVAm. Therefore, afterhybridization, the thermal stability is enhanced greatly and this isvery important for the catalyst application.

3.3. Catalytic activity

The Knoevenagel condensation of benzaldehyde with ethylcyanoacetate was chosen as a model reaction to test the catalyticactivity of the PVAm/SBA-15. Thus, the effect of different param-eters on Knoevenagel condensation of benzaldehyde with ethylcyanoacetate was investigated and the results were found to beas follows:

The sensitivity of a heterogeneously catalyzed reaction to dif-ferent solvents can usually be of extreme importance, dependingon the nature of the catalyst-supported material. The Knoevenagelcondensation using silica supported catalysts had a very limitedrange of effective solvents, the Knoevenagel condensation of ben-zaldehyde with ethyl cyanoacetate was performed in differentnon polar and polar solvents such as tetrahydrofuran, toluene,

dichloromethane, cyclohexane, dioxane, ethanol, n-hexane, ace-tonitrile and water (Table 2). As can be seen from Table 2, thereaction was performed with a high yield while increasing thepolarity of the solvent. In addition, protic solvents are more

Table 2Effect of solvent on Knoevenagel condensation.a

Yieldb (%) Solvent

90 Ethanol75 Water60 Methanol37 Acetonitrile10 DichloromethaneNR TolueneNR Tetrahydrofuran

a Reaction conditions: benzaldehyde (2 mmol), ethyl cyanoacetate (2 mmol),PVAm/SBA-15 (0.12 g), solvent (10 mL), time (2 h), reflux.

b GC yield.

788 R.J. Kalbasi et al. / Materials Chemistry and Physics 125 (2011) 784–790

eitapie

vf

etstr

rrttsfoePc

Table 3Effect of SBA-15 amount on catalytic activity of composite PVAm/SBA-15.a

Amount of SBA-15/AA (g/g) Yield (%)b

0/0.25 800.25/0.25 780.5/0.25 901.0/0.25 610.5/0 NR

a Reaction conditions: benzaldehyde (2 mmol), ethyl cyanoacetate (2 mmol), cat-alyst (0.12 g), ethanol (10 mL), Time (2 h), reflux.

b GC yield.

Table 4Effect of catalyst amount on Knoevenagel condensation.a

Yieldb (%) Amount of catalyst (g)

50 0.0666 0.0885 0.1090 0.1290 0.14

Fig. 6. Effect of temperature on the catalytic Knoevenagel condensation.

ffective than aprotic solvents. This behavior is attributed to thenfluence of the solvent on the transition state and to a change inhe capacity of the catalyst for proton transfer: when polar reagentsre involved, the transition-state complex is better solvated byolar solvents and the partition of the reactants at the solid–liquid

nterface is higher, decreasing the activation free enthalpy andnhancing the reaction rate.

The best result was obtained when ethanol was used as sol-ent, therefore, this environmentally friendly solvent was chosenor other reactions.

The reaction was also carried out at different temperatures inthanol. The reaction was performed at 25 ◦C, 40 ◦C, 60 ◦C and refluxemperature (78 ◦C). Then yield of the reaction was compared. Fig. 6hows an increase in yield with a rise in temperature; consequently,he reflux condition was found to be the best temperature for thiseaction.

In order to study the effect of the amount of SBA-15 for prepa-ation of composite PVAm/SBA-15, different catalysts with variousatios of SBA-15 to PVAm were prepared. The catalytic activity wasested with these catalysts (Table 3). One of the greatest advan-ages of this catalyst is that it is easy to use it due to its powderytructure. PVAm is adhesive and this makes it hard to separate

rom the vessel but after being mixed with SBA-15 and the makingf PVAm/SBA-15 composite, it becomes powdery which is a formasy to use and to recycle. Also a comparative reaction by usingVAm and PVAm/SBA-15 shows that PVAm/SBA-15 is more effi-ient, because of completion of the reaction in a shorter time. As the

C

O

H2C

CN

CO2Et

PVAm/SBA-1

Ethanol Refl+

Ar H

,

Scheme 2. Knoevenagel condensatio

NO2

HC

NO2

CH3C

O

O H2C

CN

CO2Et

PVAm/SB

Ethanol, R+

1mmol

1mmol

1mmol

Scheme 3. Chemoselectivity of t

a Reaction conditions: benzaldehyde (2 mmol), ethyl cyanoacetate (2 mmol),ethanol (10 mL), time (2 h), reflux.

b GC yield.

amount of SBA-15 increased, the yield increased too. These resultsare due to the large surface area of PVAm/SBA-15 in comparisonwith PVAm. When the amount of SBA-15 increased, the polymericmaterial was ordered in the surface of catalyst. So the functionalgroup of the polymer is free and more effective. But if the amountof SBA-15 is increased considerably, the ratio of the polymer func-tional group to the catalyst weight is decreased and as a result theyield is decreased too. When SBA-15 was used as the catalyst, thereaction did not occur considerably, so the existence of polymericmaterial in this composite plays a critical role in the efficiency ofthis base catalyst. The best ratio of SBA-15 to acryl amide was foundto be 2 (w/w) of these components.

A possible adsorption mode for PVAm/silica is a lone pair inter-

action between the nitrogen atom (NH2) and the hydroxyl protonson the silica surface or a less specific Van der Waals interactionbetween the aliphatic polymer chain backbone and the silica sur-face [26]. Hence the amount of SBA-15 influenced the interaction

5

uxAr

CN

CO2Et

+ H2O

n catalyzed by PVAm/SBA-15.

NO2

CN

EtO2C

A-15

eflux

96 %

+ H2O

he catalyst PVAm/SBA-15.

R.J. Kalbasi et al. / Materials Chemistry and Physics 125 (2011) 784–790 789

Table 5Knoevenagel condensation reaction of aromatic aldehydes and ethyl cyanoacetate catalyzed by PVAm/SBA-15.a

Entry Substrate Product Time (min) Yieldb (%) mp (◦C) Ref.

Found Reported

1 CHOCH

C COOEt

CN

120 90 49–51 50 [6]

2CHO

H3C

CH

C COOEt

CNH3C

30 80 82–85 Not reported [31]

3CHO

OH

CH

C COOEt

CNOH

90 70 172–174 173–175 [27]

4 CHOH3COCH

C COOEt

CN

H3CO25 80 81–82 80 [6]

5

CHO

Cl

CH

C COOEt

CNCl

60 94 52–54 53–54 [28]

6 CHOO2NCH

C COOEt

CN

O2N60 96 165 169 [6]

7O

CHOO C

H

CCN

COOEt

30 95 85–87 89–91 [29]

8

N CHO N CH

C

COOEt

CN30 90 92–94 95–96 [30]

(10 m

baaectot

eowtcb

a Reaction conditions: substrate (2 mmol), ethyl cyanoacetate (2 mmol), ethanolb GC yield.

etween PVAm and SBA-15 and could increase or decrease themount of active sites on the catalyst. To prove this idea, themount of basic sites of the catalyst was determined for differ-nt SBA-15/PVAm ratios in the composite. The amine contents ofatalysts were found to be 14.00, 13.80 and 12.60 mequiv. g−1 forhe amounts of SBA-15 0.25, 0.50 and 1.00 g, respectively. It can bebserved that with increasing the amount of SBA-15 to PVAm ratio,he amount of basic site decreases.

The effect of the amount of the catalyst was determined for Kno-venagel reaction. It can be seen that with an increase in the amount

f catalyst from 0.06 g to 0.12 g, a considerable increase in the yieldas observed from 50% to 90% (Table 4). It can be seen from this

able that a higher amount of catalyst (0.14 g) had no any appre-iable effect on the yield. Thus, the quantity of 0.12 g was found toe the best weight of composite PVAm/SBA-15 for the condensa-

L), catalyst (0.12 g), reflux.

tion of benzaldehyde (2 mmol) with ethyl cyanoacetate (2 mmol)in ethanol (10 mL) at reflux temperature.

The study was then extended to the Knoevenagel conden-sation of several aromatic and hetero-aromatic aldehydes withethyl cyanoacetate using this basic catalyst (Scheme 2). All thereactions occurred giving �,�-unsaturated carbonyl compoundswith 100% selectivity. Reactions were carried out in ethanol atreflux temperature at different times. The results are listed inTable 5. As expected for nucleophilic addition reactions, aro-matic aldehydes with electron-withdrawing groups such as chloro

(–Cl) and nitro (–NO2) moieties were more reactive and thereactions were completed in a short time (entries 5 and 6).Also reasonably good yields were observed for the reaction ofaldehydes containing electron-donating groups such as methyl(–CH3), hydroxyl (–OH) and methoxy (–OCH3) (entries 2–4). Alde-

7 istry

h2y

rewIop

mae(v4hn

4

oiTaorimr1itrpueimfwt

[[[[[[

[[

[

[

[

[[[[

[

[

[[[

[[

90 R.J. Kalbasi et al. / Materials Chem

yde derivatives of pyridine and furan, such as furfural and-pyridine carbaldehyde (entries 7 and 8) providing very goodields.

Reusability of the catalyst was tested by carrying out repeateduns of the reaction on the same batch of the catalyst. Afterach cycle the catalyst was filtered, washed with acetone andater and dried at 60 ◦C and then re-used for successive cycles.

t is evident that the catalyst worked well several times with-ut any modification and significant loss of activity/selectivityerformance.

In order to examine the chemoselectivity of the presentethod, equimolar mixtures of ketone (4-nitro acetophenone)

nd aldehyde (4-nitro benzaldehyde) were allowed to react withthyl cyanoacetate in the presence of PVAm/SBA-15 compositeScheme 3). Under these condition, 4-nitro benzaldehyde was con-erted to the corresponding �,�-unsaturated compounds while-nitro acetophenone remained intact. Hence this catalyst showedigh chemoselectivity between aldehyde and ketone in Knoeve-agel condensation.

. Conclusion

Here the synthesis of PVAm/SBA-15 by in situ polymerizationf acryl amide in the presence of SBA-15 and the subsequent mod-fication of the resulting polymers functional groups is reported.he large surface area of SBA-15 causes this novel compound toct as an efficient basic catalyst. The basic activity of this novelrganic–inorganic hybrid was tested for Knoevenagel condensationeaction in ethanol. Green media for this reaction, catalyst reusabil-ty and simple work-up are the main advantages of this polymer

aterial supported on an inorganic surface. Also the comparativeeaction using PVAm and PVAm/SBA-15 shows that PVAm/SBA-5 is more efficient, thanks to the completion of the reaction

n a shorter time. Also by, using PVAm, the yield decreased andhe reaction was carried out over a long period of time. Theseesults are due to the large surface area of PVAm/SBA-15 in com-arison with PVAm. It should be noted that when SBA-15 wassed as catalyst, the reaction did not proceed significantly. Thexistence of both organic and inorganic phases in this compos-

te has critical effects on the catalyst activity. The merit of this

ethodology is that it is simple, fast, mild, and efficient. There-ore we believe that the new synthetic method reported hereould greatly contribute to a process which is safe environmen-

ally.

and Physics 125 (2011) 784–790

Acknowledgements

The support from Islamic Azad University, Shahreza Branch(IAUSH) Research Council and Center of Excellence in Chemistryis gratefully acknowledged.

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13C NMR. White crystal, mp: 82–85 ◦C; IR (KBr, cm−1): 3022, 2982, 2908, 2218,1728, 1609, 1450, 1232, 1087, 796, 745, 683; 1H NMR (500 MHz, CDCl3): ı(ppm) = 8.25 (s, 1H), 7.85 (d, J = 7.2 Hz, 2H), 7.81 (s, 1H), 7.41 (m, 2H), 4.42 (q,2H), 2.45 (s, 3H), 1.43 (t, 3H); 13C NMR (125 MHz, CDCl3): ı (ppm) = 163.03(C O, ester), 155.69, 139.56, 134.64, 132.12, 131.91, 129.59, 128.66, 115.97,103.12, 77.70, 77.45, 77.19, 63.11, 21.71, 14.59.