Palladium anchored on amine-functionalized K10 as an efficient, heterogeneous and reusable catalyst for carbonylative Sonogashira reaction

Article abstract of DOI:10.1016/j.apcata.2015.09.019

The present work describes the immobilization of palladium chloride (II) on the amine functionalized K10 support and its application toward the carbonylative Sonogashira reactions. The various catalyst characterization techniques revealed the successful grafting of APTES moiety on the K10 clay surface through covalent bonding and Pd with the NH₂ groups of APTES@K10 through co-ordinate bonding. The immobilized catalyst was successively applied for copper and phosphine free carbonylative Sonogashira reaction of aryl and hetero aryl iodides with terminal alkynes. To our delight, the electron withdrawing aryl halides can be efficiently utilized as an electrophiles giving higher selectivity toward carbonylated products. Moreover, dibenzoylmethane which is a potential synthetic intermediate in organic transformation has been also synthesized using this protocol. Recovery of catalyst by simple filtration and its reuse up to four consecutive cycles ensure the robustness of present catalytic protocol.

Full text of DOI:10.1016/j.apcata.2015.09.019

Applied Catalysis A: General 506 (2015) 237–245
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Palladium anchored on amine-functionalized K10 as an efficient,
heterogeneous and reusable catalyst for carbonylative Sonogashira
reaction
Sujit P. Chavana, G.Bishwa Bidita Varadwajb, Kulamani Paridab,∗
,
Bhalchandra M. Bhanagea,∗
a Department of Chemistry, Institute of Chemical Technology, N. Parekh Marg, Matunga, Mumbai 400 019, Maharashtra, India
b Centre for Nano Science and Nano Technology, ITER, SOA University, Jagamohan Nagar, Bhubaneswar 751 030, Odisha, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 21 July 2015
Received in revised form 9 September 2015
Accepted 14 September 2015
Available online 21 September 2015
The present work describes the immobilization of palladium chloride (II) on the amine functionalized
K10 support and its application toward the carbonylative Sonogashira reactions. The various catalyst
characterization techniques revealed the successful grafting of APTES moiety on the K10 clay surface
through covalent bonding and Pd with the NH2 groups of APTES@K10 through co-ordinate bonding. The
immobilized catalyst was successively applied for copper and phosphine free carbonylative Sonogashira
reaction of aryl and hetero aryl iodides with terminal alkynes. To our delight, the electron withdrawing
aryl halides can be efficiently utilized as an electrophiles giving higher selectivity toward carbonylated
products. Moreover, dibenzoylmethane which is a potential synthetic intermediate in organic transfor-
mation has been also synthesized using this protocol. Recovery of catalyst by simple filtration and its
reuse up to four consecutive cycles ensure the robustness of present catalytic protocol.
Keywords:
Alkynyl ketones
Carbonylative Sonogashira reaction
Heterogeneous catalysis
Dibenzoylmethane
Pd(II)APTES@K10
© 2015 Elsevier B.V. All rights reserved.
1. Introduction
become an impressive tool for the synthesis of value added chem-
icals in academic laboratories as well as in industrial processes [7].
Alkynyl ketones are key structural motifs in organic synthesis
as they provide an easy access to various natural products and
heterocycles [1]. Moreover, presence of alkynyl ketones in vari-
ous biological active molecules [2] attracts an organic chemist to
develop various strategies for its synthesis. Conventionally, alkynyl
ketones were prepared by the coupling of acid chlorides with
alkynyl organometallic reagents such as copper, cadmium, lithium,
silicon, sodium, silver, tin and zinc [3]. Furthermore, the transi-
tion metal catalyzed cross coupling of acid chlorides with terminal
alkynes is a common route toward alkynyl ketones [4]. Recently,
transition metal free Lewis acid catalyzed reaction of alkynyltrifluo-
roborate salts with acid chloride has been reported for the synthesis
of alkynyl ketones [5]. Tang et al. have reported the synthe-
sis of alkynyl ketones using Pd(OAc)2/bis[(2-diphenylphosphino)
phenyl] ether catalyst and tert-butyl isocyanide as a carbonylating
reagent [6]. The carbonylative reactions by using simple, inexpen-
sive and readily available carbon monoxide gas as C1 source has
Moreover, among the different carbonylation reactions; carbony-
lation of alkynes with various elecrophiles and nucleophiles has
been a prime method for the synthesis of valuable chemicals [7,8].
In 1981, Kobayashi and Tanaka firstly reported the carbonylation of
terminal alkynes with aryl halides in the presence of palladium cat-
alyst, which is now referred as a carbonylative Sonogashira reaction
for the synthesis of alkynyl ketones [9]. Being its great importance,
promising development has been put forward and the scope of this
reaction has also extended for the synthesis of various heterocycles
[10].
In last decade various homogenous catalytic protocols were
developed for the carbonylative Sonogashira reactions. Ahmed
and Mori has reported palladium catalyzed Carbonylative cou-
pling of phenylacetylene with 4-methoxy-1-iodobenzene using
2 equiv. of 0.5 M aqueous ammonia [11]. Aqueous version of
carbonylative Sonogashira reaction has been reported by Yang
et al. using PdCl2/PPh3 catalytic system [12]. Beller and co-
workers developed copper free [(Cinnamyl)PdCl]2/BuPAd2 and
[(Cinnamyl)PdCl]2/Xantphos catalytic systems for the carbonyla-
tive Sonogashira of aryl bromides and aryl triflates respectively
[13]. The same group carried out interesting piece of work,
where they have developed cascade methodology for carbonylative
∗
Corresponding authors. Fax: +91 223361 1020.
E-mail addresses: bm.bhanage@gmail.com, bm.bhanage@ictmumbai.edu.in
(B.M. Bhanage).
http://dx.doi.org/10.1016/j.apcata.2015.09.019
0926-860X/© 2015 Elsevier B.V. All rights reserved.

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S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
vent. The resulting suspension was stirred at room temperature for
2 h. Then the suspension was transferred into a Teflon bottle and
hydrothermally aged at 100 ◦C for another 10 h. The solid product
was filtered; washed three times with deionized water and dried
subsequently in a vacuum oven at 80 ◦C for 8 h.
2.2.2. Synthesis of Pd(II) supported organofunctionalized
montmorillonite [Pd(II)APTES@K10]
Pd(II) loaded organofunctionalized montmorillonite was pre-
pared by impregnating 1.0 g of APTES@K10 support with 25 mL
aqueous solution of PdCl2 (0.1 mmol) by an incipient wetness
impregnation method followed by drying in air for about 24 h.
Then the solid residue was grinded. The orange coloured powder
obtained is designated as Pd(II)APTES@K10.
Scheme 1. Scope for Pd(II)APTES@K10 catalyzed carbonylative Sonogashira reac-
tions.
Sonogashira reactions of aryl amines using Pd(OAc)2/tri(2-furyl)
phosphine along with t-BuONO via diazotization of aryl amines
[14]. Carbonylative Sonogashira reaction has been well explored by
using various homogeneous palladium catalysts along with various
phosphine ligands, copper salts and ammonia. However, with these
homogeneous catalytic processes, the recovery and reutilization of
the expensive metal catalysts is a difficult task which affects over-
all process economy. In this context, some homogeneous recyclable
and heterogeneous catalytic system have also been developed [15].
However, they suffer from one or more drawbacks such as long
reaction time, difficulties in catalyst-product separation, high tem-
perature and pressure requirement. Hence, it is highly desirable to
develop a simple, efficient and recyclable heterogeneous catalytic
system for the carbonylative Sonogashira reaction which can work
under milder reaction conditions.
Now days, the immobilization of metal catalyst on proper sup-
port is a key area of interest in heterogeneous catalysis. It is a
worthy process of introducing aminofunctional silanes onto the
surface of the solid support in order to improve the adhesion
between the metal and the support. Moreover, literature study
also reveals the importance of covalent immobilization of organosi-
lane on clay minerals. So, promoted by the above considerations as
well as our experience on organosilane functionalized K10 mont-
morillonite as an efficient support for heterogeneous catalysis and
in continuation of our research for carbonylation reactions [16],
herein we have developed a simple and efficient copper free proto-
col for the carbonylative Sonogashira reaction using heterogeneous
Pd(II)APTES@K10 as a catalyst. The present catalytic system is also
found to be applicable for the carbonylative Sonogashira reaction
of aryl diiodides and also for the synthesis of dibenzoylmethane
(Scheme 1).
2.2.3. Characterization techniques
N2 adsorption–desorption analysis was carried out at liquid N2
temperature (−196 ◦C) by an ASAP 2020 (Micromeritics) instru-
ment. Before analyses, all the samples were degassed at 300 ◦C and
10−6 Torr pressure for 5 h to evacuate the physically adsorbed mois-
ture. The X-ray diffraction (XRD) patterns were measured in the
2␪ range of 10–-80◦ at a rate of 2◦/min in steps of 0.01◦ (Rigaku
Miniflex set at 30 kV and 15 mA) using Cu K␣ radiation. Solid state
13C and 29Si CP MAS NMR spectra were acquired on an AV300
NMR spectrometer. The FTIR spectra of the samples were recorded
using Varian 800-FTIR in KBr matrix in the range of 4000–400 cm−1
.
Transmission electron microscopy (TEM) images were acquired
using a microscope (FEI, TECNAI G2 20, TWIN) operating at 200 kV.
The X-ray photoelectron spectroscopy (XPS) analysis was per-
formed on a KRATOS apparatus with Mg, Al and Cu K␣ as X-ray
sources. FE-SEM was performed with a ZEISS 55 microscope.
2.3. General experimental procedure for carbonylative synthesis
of alkynyl ketones
To a 100 mL autoclave, aryl iodide (1 mmol), alkyne (1.15 mmol),
Pd(II)APTES@K10 (0.03 g), Et3N (2 mmol) and solvent (10 mL) were
added. The autoclave was closed, flushed two times with carbon
monoxide, pressurized with 4 atm of CO, and heated at 80 ◦C for
7 h. After the completion of the reaction, the reactor was cooled to
room temperature, and the remaining CO gas was carefully vented,
and the reactor was opened. The reactor vessel was thoroughly
washed with ethyl acetate (3 × 10 mL) to remove any trace of prod-
uct and catalyst if present. The catalyst was filtered, and the filtrate
washed with brine (2 × 10 mL), dried over anhydous Na2SO4, and
the solvent evaporated under vacuum. Purification of residue was
carried out by column chromatography (silica gel, 120–200 mesh,
petroleum ether/ethyl acetate) to afford the desired product.
2. Experimental
2.1. Materials and methods
2.4. General experimental procedure for carbonylative
Sonogashira reaction of biaryl iodide
Reagents and anhydrous solvents were used as it is obtained
from commercial vendors. All reactions were performed in
a 100 mL autoclave. The reaction process was monitored by
gas chromatography on Perkin Elmer Clarus 400 GC equipped
with flame ionization detector with a capillary column (Elite-
1, 30 m × 0.32 mm × 0.25 ␮m). Products were purified by column
chromatography on silica gel (120–200) mesh.
To
a 100 mL autoclave, biaryl iodide (0.5 mmol), alkyne
(1.15 mmol), Pd(II)APTES@K10 (0.03 g), Et3N (2 mmol) and DME
(10 mL) were added. The autoclave was closed, flushed two times
with carbon monoxide, pressurized with 4 atm of CO, and heated at
80 ◦C for 8 h. After the completion of the reaction, the reactor was
cooled to room temperature, and the remaining CO gas was care-
fully vented, and the reactor was opened. The reactor vessel was
thoroughly washed with ethyl acetate (3 × 10 mL) to remove any
traces of product and catalyst if present. The catalyst was filtered,
and the filtrate washed with brine (2 × 10 mL), dried over anhy-
drous Na2SO4, filtered and the solvent evaporated under vacuum.
Purification of the residue was carried out by column chromatog-
2.2. Preparation and characterization of the catalyst.
2.2.1. Synthesis of amine functionalized montmorillonite
(APTES@K10)
1 g K10 montmorillonite (K10) was added to 15 mL of a solution
of 3-amino propyl triethoxysilane (2.32 mmol) using water as sol-

S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
239
Fig. 2. FTIR spectra of (a) K10 (b) APTES@K10 (c) Pd(II)APTES@K10.
Fig. 1. XRD patterns of (a) K10, (b) APTES@K10, (c) Pd(II)APTES@K10.
raphy (silica gel, 120–200 mesh, petroleum ether/ethyl acetate) to
afford the desired product.
2.5. General experimental procedure for carbonylative synthesis
of dibenzoylmethane
To a 100 mL autoclave, aryl iodide (1 mmol), alkyne (1.15 mmol),
Pd(II)APTES@K10 (0.03 g), Et3N (2 mmol) and DMF:H2O (9:1 mL)
were added. The autoclave was closed, flushed two times with car-
bon monoxide, pressurized with 4 atm of CO, and heated at 80 ◦C for
8 h. After the completion of the reaction, the reactor was cooled to
room temperature, and the remaining CO gas was carefully vented,
and the reactor was opened. The reactor vessel was thoroughly
washed with ethyl acetate (3 × 10 mL) to remove any traces of prod-
uct and catalyst if present. The catalyst was filtered, and the filtrate
washed with brine (2 × 10 mL), dried over anhydrous Na2SO4, fil-
tered and the solvent evaporated under vacuum. Purification of
the residue was carried out by column chromatography (silica gel,
120–200 mesh, petroleum ether/ethyl acetate) to afford the desired
product.
Fig. 3. N2 adsorption–desorption isotherms of (a) K10, (b) APTES@K10, (c)
Pd(II)APTES@K10.
The FTIR study of samples shows typical peaks for montmoril-
lonite. The peaks at 3594, 1034, 3416 and 1636 cm−1 is assigned
2.6. Catalyst reusability
for Al
and H
O
O
H stretching, Si
H bending vibrations respectively (Fig. 2). In case of
O Si stretching, H O H stretching
The reusability of the catayst was studied for the synthesis
1,3-diphenylprop-2-yn-1-one using the above mentioned proce-
dure(2.3). After the completion of reaction the catalyst was filtered.
The filtered catalyst was washed with distilled water (3 × 5 mL)
and methanol (3 × 5 mL) to remove all traces of product or reac-
tant present. Finaly the catalyst was dried under vacuum and used
in the next cycle.
APTES@K10, the weak bands at 2941 cm−1 and 2879 cm−1 cor-
respond to the asymmetric and symmetric CH2 stretch [17]. The
observation of N H bending vibration at around 690 cm−1 and NH2
symmetric bending vibration at 1536 cm−1 confirms the presence
of amide moieties. These results show the presence of APTES moi-
ety on clay surface. However, its attachment to the clay surface can
only be confirmed from NMR spectroscopy. The Pd(II)APTES@K10
sample shows similar characteristic peaks of APTES@K10.
3. Results and discussion
N2 adsorption–desorption isotherms of K10 (a), APTES@K10
(b), Pd(II)APTES@K10 (c) are shown in Fig. 3, both the
APTES@K10 and Pd(II)APTES@K10 display a typical type-IV N2
adsorption–desorption isotherm similar to that of neat K10 indi-
cating the preservation of the mesoporous structure after grafting
NH2 groups and even after Pd deposition. Though, all the isotherms
belong to type-IV category, a clear decrease in the N2 uptake
capacity can be visualized from Fig. 3. Therefore, some structural
parameters based on the BET and BJH methods were calculated
from the N2 adsorption–desorption isotherms (Table 1). These data
3.1. Characterization of catalyst
The XRD patterns of K10 (a), APTES@K10 (b) and
Pd(II)APTES@K10 (c) are shown in Fig. 1. In all the samples,
all of the observed peaks are also consistent with the parent clay,
indicating that the existence of APTES and Pd on the K10 does not
affect the primary structure of the acid activated parent mont-
morillonite (K10). The hkl and two dimensional hk reflections for
montmorillonite remained unaffected in case of Pd(II)APTES@K10.

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S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
Table 1
are very close to the typical values of Pd(II) species [19]. The sam-
Textural properties of the prepared materials.
ple has photoelectron peaks corresponding to only Pd(II) species.
The lack of any peak at 335 eV indicates that no Pd(0) nanoparti-
cles formed during the preparation of Pd(II)APTES@K10. To further
confirm the chemical bonding of Pd(II) species with the NH2 groups
of APTES@K10, Fig. 5(b) shows the N 1s spectrum of the Pd(II)
APTES@K10. Usually the N1s peak is observed at nearly 400 eV.
However, the binding energies of N 1s observed at 401.3 eV in case
of Pd(II)APTES@K10, demonstrates the strong interaction between
Pd and -NH2 groups, which occurred because of the donation of lone
pair of electrons from N atom, thereby catching the Pd metal more
easily forming co-ordination bond with it [20]. This is beneficial to
the enhanced catalytic activity of Pd(II)APTES@K10. XPS spectra of
reused catalyst shows the insitu fornation of active catalytic species
i.e. Pd(0)APTES@K10 [Fig. 5(c)].
Sample
Surface area (m2/g)
Pore volume (cm3/g)
MMT
APTES@MMT
Pd(II)APTES@MMT
241.41
147.15
134.41
0.41
0.29
0.21
FESEM images of K10, APTES@K10 and Pd(II)APTES@K10 are
shown in Fig. 6. The neat K10 possesses a layered morphology con-
sisting of broken plates. After functionalization with APTES and
Pd loading the layered morphology of the parent K10 retained
intact. This is in accordance with the XRD and N2 adsorption-
desorption analysis results. The corresponding EDAX image of
Pd(II)APTES@K10 confirms the presence of Pd along with the native
elements of APTES functionalized clay like Si, Al, and O.
TEM images also support the preservation of platy structure of
K10 even after functionalization with APTES and subsequent metal
loading (Fig. 7).
Fig. 4. 29Si CP MAS NMR spectrum of APTES@K10.
The immobilized catalyst Pd(II)APTES@K10 was applied for the
carbonylative Sonogashira reaction. The reaction of iodobenzene
with phenyl acetylene in presence of CO was chosen as model reac-
tion and the effect of various reaction parameters such as catalyst
loading, solvent, base, temperature, time and CO pressure were
thoroughly examined (Tables 2 and 3).
clearly suggest the decrease in surface area and pore volume on
grafting of APTES moiety and Pd loading. This decrease could be
ascribed to the space occupied by the organosilane moieties along
with the Pd loading on the clay surface. However, a clear deci-
sive remark cannot be given regarding the functionalization and
Pd immobilization from this study.
Initially we have studied the effect of catalyst loading ranging
from 0.02 g to 0.04 g and it was observed that increasing catalyst
loading from 0.02 g to 0.03 g showed an increase in the yield of
1,3-diphenylprop-2-yn-1-one (3a) (Table 2, entries 1–2). Further
increase in catalyst loading has no profound effect on the yield of
desired product 3a (Table 2, entry 3).
Next, we have investigated the effect of various inorganic and
organic bases on the model reaction. It was found that inorganic
bases such as Na2CO3 and K2CO3 provided 3a in moderate yield
whereas NaOAc gave 3a in 40% yield and 1,2-diphenylethyne prod-
uct in 35% yield (Table 3, entries 1–3). Furthermore, significant
improvement in the yield of 3a was observed when triethyl amine
was used as a base, while other bulky organic bases such as DBU,
DABCO, DIEA gave poor to moderate yields of 3a (Table 3, entries
4–7). The role of solvents has enormous effect on the catalytic
activity. Therefore, we have examined the effect of various polar
and nonpolar solvents on carbonylative Sonogashira reaction using
To check the grafting of APTES moiety on K10 surface, the
APTES@K10 was subjected to 29Si CP MAS NMR spectroscopy
(Fig. 4). Usually, the solid state 29Si CP MAS NMR spectra of
acid activated montmorillonite shows 29Si NMR shifts assigned
as Q4(0Al), Q3(0Al), Q3(1Al) and Q4(1Al) Si atoms with respec-
tive co-ordination Si(OSi)4, Si(OSi)3(OH), Si(OSi)2(OAl)OH, and
Si(OSi)3(OAl) in the clay framework [18]. However, in addi-
tion to those characteristic peaks two additional T3 and T2
peaks were observed at about −60.09 and −53.05 ppm in case
of Pd(II)APTES@K10 (Fig. 4). The two Tn peaks where Tn
=
[RSi(OEt)n(OSi)3-n], confirms the successful grafting of APTES moi-
ety on clay surface.
X-ray photoelectron spectroscopy (XPS) analysis provides the
information about the chemical environment and elemental oxi-
dation state of the catalyst. Fig. 5(a) shows the Pd 3d X-ray
photoelectron spectrum of Pd(II)APTES@K10. The binding energies
of Pd(II) 3d5/2 and 3d3/2 are 337.9 and 342.0 eV respectively, which
Table 2
Effect of catalyst loading on carbonylative Sonogaghira reaction.a
Entry
Catalyst loading (g)
TON
Yield%b
1
2
0.02
0.03
0.04
0.04
250
250
192
160
50
75
77
64
3
4c
a
Reaction conditions: 1a (1 mmol), 2a (1.15 mmol), Pd(II)APTES@K10, CO (4 atm), Na2CO3 (2 mmol) in 10 mL DMF for 7 h.
GC yield.
Reaction time 5 h.
b
c

S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
241
Fig. 5. (a) Pd 3d X-ray photoelectron spectrum of Pd(II)APTES@K10, (b) N 1s X-ray photoelectron spectrum of the Pd(II) APTES@ K10. (c) Pd 3d X-ray photoelectron spectrum
of catalyst after 4th recycle.
Fig. 6. FESEM images of (a) K10, (b) APTES@K10, (c) Pd(II)APTES@K10, (d) EDAX spectrum Pd(II)APTES@K10.
NEt3 as a base (Table 3, entries 8–12). It was observed that DME
provided excellent yield of 3a (Table 3, entry 11). On evaluating
the effect of temperature toward the desired reaction, we observed
that on increasing the temperature from 70 ◦C to 80 ◦C resulted in
an increase in the yield of 3a, while on increasing the temperature
further led to the decrease in the yield of 3a due to the formation of

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S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
Fig. 7. TEM image of (a) K10, (b) Pd(II)APTES@K10, (c) Catalyst after 4th recycle.
Table 3
Optimization of reaction parameter.a
Entry
Base
Solvent
Temperature (◦C)
Time (h)
TON
Yield (%)b
Effect of base
1
2
3
4
5
6
7
Na2CO3
K2CO3
NaOAc
NEt3
DBU
DABCO
DIEA
DMF
DMF
DMF
DMF
DMF
DMF
DMF
80
80
80
80
80
80
80
7
7
7
7
7
7
7
250
266
133
300
116
200
283
75
80
40
90
35
60
85
Effect of solvent
Scheme 2. The double carbonylative Sonogashira reaction of aryl diiodides.
8
9
NEt3 Toluene
NEt3
80
80
80
80
80
7
7
7
7
7
100
200
240
313
183
30
60
72
94
55
THF
10
11
12
NEt3Dioxane
NEt3
NEt3
DME
ACN
Effect of temperature
13
14
NEt3
NEt3
DME
DME
70
90
7
7
260
290
78
87
Effect of time
Scheme 3. The carbonylative synthesis of dibenzoylmethane
15
16
NEt3
NEt3
DME
DME
80
80
5
8
213
313
64
94
tive Sonogashira reaction of 1-iodonaphthalene with 2a furnished
corresponding alkynyl ketone 3i in 85 % yield (Table 4, entry 9). Fur-
thermore, the reactions of hetero aryl halides like 2-iodopyridine
and 4-iodo-1H-pyrazole with 2a provided respective products 3j
and 3k in good yields (Table 4, entries 10 and 11). We also stud-
ied the reaction of 1a with various aryl and alkyl acetylenes for the
carbonylative Sonogashira coupling providing the corresponding
products in excellent yields (Table 4, entries 12–15). Subsequently,
the reaction of 1b with 2b also furnished the respective product
1,3-di-p-tolylprop-2-yn-1-one (3p) in 90% yield (Table 4, entry 16).
The double carbonylative Sonogashira reaction of 1,4-
diiodobenzene with phenyl acetylene were also tested and
give good yield of dialkynyl ketones along with noncarbonylative
product (Scheme 2).
a
Reaction conditions: 1a (1 mmol), 2a (1.15 mmol), Pd(II)APTES@K10 (0.03 g), CO
(4 atm), Base (2 mmol), Solvent (10 mL), 7 h.
dimerised product of 2a (Table 3, entries 13–14). The effects of time
and CO pressure were also investigated (Table 3, entries 15–16) and
the optimum time and pressure was used for further studies.
Using this optimized reaction parameters the scope and limita-
tions of developed protocol was evaluated (Table 4). The reaction
of 2a with aryl iodide bearing electron donating groups (-CH3,
-OCH3) provided corresponding products 3c and 3d in excel-
lent yields (Table 4, entries 3 and 4). Whereas, the reaction
of 2a with ortho-substituted aryl iodides provided correspond-
ing products 3b and 3e in moderate yields, which might be
due to steric hindrance (Table 4, entries 2 and 5). Literature
study reveals that carbonylative Sonogashira reaction of electron-
withdrawing aryl halides is still a challenging one, as they furnish
mixture of carbonylative as well as noncarbonylative coupling
products with maximum selectivity toward noncarbonylative
product [11,12,14]. To our delight, when we have studied the
aryl iodide bearing electron withdrawing groups such as -NO2, -
CN for carbonylative Sonogashira reaction, carbonylative coupling
products 3f and 3 g were obtained in excellent yields (Table 4,
entries 6 and 7). Notably, 1-fluoro-3-iodobenzene (1 h) gave
corresponding carbonylative coupling product 1-(3-fluorophenyl)-
3-phenylprop-2-yn-1-one (3 h) in 88% yield without formation
of noncarbonylative product (Table 4, entry 8). The carbonyla-
Dibenzoylmethane which is potential synthetic intermediate in
organic transformation has also been synthesized by using this
methodology [21]. However, the present methodology was inca-
pable to synthesize the substituted dibenzoylmethanes (Scheme 3).
3.2. Catalyst reusability
Reusability of heterogeneous catalyst is an important aspect to
ensure robustness of any catalytic protocol. So, we have tested the
reusability of Pd(II)APTES@K10 catalyst for the carbonylative Sono-
gashira coupling reaction of 1a with 2a. The catalyst was found to be
reused for four consecutive cycles with excellent catalytic activity
and selectivity toward the formation of desired product 3a (Fig. 8).

S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
243
Table 4
Substrate study for carbonylative Sonogashira reactions.a
Entry
1
Aryl iodide
Acetylene
Product
TON
306
Yieldb[%]
92
75
2
2a
250
3
4
2a
2a
306
300
92
90
5
6
7
2a
2a
2a
206
260
266
62
78
80
8
9
2a
2a
293
283
88
85
10
11
2a
2a
250
200
75
60
12
13
1a
1a
300
306
90
92
14
1a
296
89

244
S.P. Chavan et al. / Applied Catalysis A: General 506 (2015) 237–245
Table 4 (Continued)
Entry
15
Aryl iodide
1a
Acetylene
Product
TON
283
Yieldb[%]
85
16
1b
2b
300
90
a
Reaction conditions: aryl iodide (1 mmol), acetylene (1.15 mmol), Pd(II)APTES@K10 (0.03 g), CO (4 atm), NEt3 (2 mmol) in 10 mL DME for 7 h.
Isolated yield.
b
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