Zeolite-based copper catalyst for decarboxylative coupling of alkynyl carboxylic acids with aryl iodides

Article abstract of DOI:10.1016/j.catcom.2017.05.025

A series of nanoporous aluminosilicate materials (zeolite FAU(Y), LTA(A), and mesoporous Al-SBA-15) was prepared to investigate their catalytic performances in decarboxylative coupling reactions of alkynyl carboxylic acids with aryl iodides. The aluminosilicate frameworks were used for binding Cu(II) ions without coordination by organic ligands. Effects of pore size and Cu(II) content of the aluminosilicates on the catalytic activity and product yield were investigated by varying the solvent, base, and functional groups in the reactants. This catalytic system provided high yields and good selectivity for the desired diaryl alkynes. In addition, the Cu(II)-exchanged zeolite Y catalyst which is NaCuY(0.11) exhibited high recyclability, showing no significant change in catalytic performance after six repetitions.

Full text of DOI:10.1016/j.catcom.2017.05.025

Accepted Manuscript
Zeolite-based copper catalyst for decarboxylative coupling of
alkynyl carboxylic acids with aryl iodides
Jaerim Park, Dasom Jung, Han-Sung Kim, Kyungsu Na, Sunwoo
Lee
PII:
S1566-7367(17)30226-1
doi: 10.1016/j.catcom.2017.05.025
CATCOM 5061
DOI:
Reference:
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Catalysis Communications
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Revised date:
Accepted date:
10 April 2017
19 May 2017
26 May 2017
Please cite this article as: Jaerim Park, Dasom Jung, Han-Sung Kim, Kyungsu Na, Sunwoo
Lee , Zeolite-based copper catalyst for decarboxylative coupling of alkynyl carboxylic
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ACCEPTED MANUSCRIPT
Zeolite-Based Copper Catalyst for Decarboxylative Coupling of Alkynyl Carboxylic
Acids with Aryl Iodides
Jaerim Park, Dasom Jung, Han-Sung Kim, Kyungsu Na,* and Sunwoo Lee*
Department of Chemistry, Chonnam National University, Gwangju, 61186, Republic of Korea
*
Corresponding authors. Tel.: +82-62-530-3385; Fax: +82-62-530-3389.
E-mail address: kyungsu_na@chonnam.ac.kr (K. Na): sunwoo@chonnam.ac.kr (S. Lee)
Keywords
Zeolite; copper; decarboxylative coupling; aryl iodide; recyclable.

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Abstract
A series of nanoporous aluminosilicate materials (zeolite FAU(Y), LTA(A), and mesoporous
Al-SBA-15) was prepared to investigate their catalytic performances in decarboxylative
coupling reactions of alkynyl carboxylic acids with aryl iodides. The aluminosilicate
frameworks were used for binding Cu(II) ions without coordination by organic ligands.
Effects of pore size and Cu(II) content of the aluminosilicates on the catalytic activity and
product yield were investigated by varying the solvent, base, and functional groups in the
reactants. This catalytic system provided high yields and good selectivity for the desired
diaryl alkynes. In addition, the Cu(II)-exchanged zeolite Y catalyst which is NaCuY(0.11)
exhibited high recyclability, showing no significant change in catalytic performance after six
repetitions.

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1
. Introduction
Transition-metal-catalyzed cross coupling is one of the most useful tools in organic
synthesis and has been widely used to form carbon-carbon and carbon-heteroatom bonds [1-
]. In most cases, homogeneous catalytic systems have been employed, wherein catalytic
3
activity is highly dependent on the nature of the ligand [4-5]. Although homogeneous
catalysts have several advantages like easy control of reactivity and selectivity, some
drawbacks include poor separation and reusability. To address these issues, a number of
alternative methods have been developed. For example, the immobilization of nanoparticle
metal catalyst onto insoluble supports like carbon nanotube and graphene and the
employment of covalent bonds between the metal and polymer support are the most popular
methods [6-12]. However, these methods also have drawbacks including difficult control of
the catalyst concentration on the support surface, thermal instability, and catalyst leaching.
As supports for the immobilization of catalysts, zeolites have also been employed, which
are microporous materials in a crystalline aluminosilicate framework. Micropores are defined
as nanopores of sizes between 0 and 2 nm. According to the size and shape of the micropores,
more than 200 different framework types of zeolites have been reported so far [13-15]. The
micropores of the zeolites of a particular type are very uniform in size and shape, which
enables selective accommodation of guest species, including molecules and metal clusters,
inside the micropores. In addition, the presence of aluminum atoms in the aluminosilicate
framework induces negative charges on the zeolite surface, which requires counter cations as
charge compensators. Metal cations, as well as cationic molecules, can be used as counter
cations, which can be easily exchanged with other cations via simple ion exchange.
2
Sonogashira cross coupling is the most popular method to date for bonding sp - and sp-
carbons, wherein aryl halides and terminal alkynes react in the presence of a Pd/Cu catalyst

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and an amine base [16-18]. This methodology has been widely used in the pharmaceutical
and materials chemistry industries, particularly for the synthesis of electro-active materials
[19]. However, a common component of these reactions is acetylene, which is cumbersome
to handle, produces toxic wastes, and is highly expensive. To address these issues, we first
reported the decarboxylative coupling reaction with alkynyl carboxylic acid and aryl halides
using Pd catalyst in 2008 [20-22]. Since then, the decarboxylative coupling reactions using a
variety of coupling partners such as C–H-activated azoles, aryl boronic acids, aryl siloxanes,
etc. have been developed. Cu- or Ni-catalyzed decarboxylative coupling reactions have also
been reported that were conducted in a homogeneous catalytic system [23-27]. Pd
nanoparticles bound to a carbon nanotube catalyzed the decarboxylative coupling reaction to
provide diaryl alkynes in good yields [28]. An immobilized copper catalyst, however, has
never been reported for use in decarboxylative coupling reactions. In our experiment, our
copper catalyst was immobilized on zeolite, which has the unique property of being able to
function as a catalyst as well as a support for catalytically active species. For example, when
transition metal cations are exchanged onto the zeolite framework, the zeolites can exhibit
catalytic function of the transition metals, while retaining intrinsic zeolite features such as
size/shape selectivity of the micropores [29-31]. Therefore, it is expected that the zeolite
framework can act as the ligand coordinating with transition metal cations, and the zeolite
micropores build a confined reaction space that can distinguish reactant, transition state, and
product according to their size and geometry during the catalytic reaction.
Herein, we report the preparation of zeolite-based copper catalyst and its application in
decarboxylative coupling reactions.
2
. Results and Discussion.
2
.1. Preparation of zeolites
Zeolites with Cu(II) counter cations were prepared to investigate their catalytic activity and

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selectivity in decarboxylative coupling reactions. A series of nanoporous aluminosilicates
with different pore sizes, including zeolite A having LTA topology (Ø = 0.45 nm), zeolite Y
having FAU topology (Ø = 0.67 nm), and ordered mesoporous silica Al-SBA-15 (Ø = 10 nm),
were prepared and used as supports for cations (Table 1 and also see Fig. S1 in
Supplementary Information for Ar or N2 sorption isotherms and their corresponding pore size
distributions). The effects of pore size of the support, type and amounts of cations, and
reaction conditions like nature of substrates, solvent, and type of bases, on the catalytic
activity and selectivity are investigated in detail.
Table 1. Zeolite-based Cu catalysts and their textural properties.
b
c
d
SBET
(
VT
Dp
Cu content
(mmol/g)
Catalyst
Support
2
3
Si/Al Cu/Al
-
m /g)
(cm /g) (nm)
NaY
642
553
527
535
342
574
0.51
-
a
a
NaCuY(0.08)
NaCuY(0.11)
0.45
0.67
0.41
0.08
2.5
0.483
0.725
0.725
0.416
0.725
FAU(Y)
LTA
0.11
a
HCuY(0.11)
0.39
0.11
a
NaCuA(0.03)
0.31
0.81
0.45
10
1
5
0.03
0.22
a
NaCuOMS(0.22) Al-SBA-15
a
Numbers in parentheses are the ratio of Cu/Al, determined by ICP-AES.
b
SBET, total surface area calculated by using Brunauer-Emmett-Teller (BET) theory.
c
VT, total pore volume calculated by Barrett-Joyner-Halenda (BJH) theory.
d
Dp, average pore diameter calculated by Horvath-Kawazoe (HK) for micropore analysis of
zeolite-based catalysts, and BJH method for Al-SBA-15.
To make the zeolites, silica and alumina precursors were mixed in an aqueous NaOH
solution. For the synthesis of zeolite FAU(Y), two synthesis gels are prepared: a seed gel and
a feedstock gel, in separate polypropylene bottles. For the preparation of seed gel, sodium

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aluminate (Sigma Aldrich, 53 wt% Na2O, 42.5 wt% Al2O3) as an alumina precursor was
mixed with aqueous NaOH and stirred until dissolution. Subsequently, water glass (Daejung,
2
9 wt% SiO2, 9.5 wt% Na2O in H2O) as a silica precursor was added to obtain a final seed gel
composition of 0.53 Na2O:0.05 Al2O3:0.5 SiO2:9 H2O. For the preparation of feedstock gel,
sodium aluminate was mixed with aqueous NaOH and stirred until dissolution. Subsequently,
water glass was added to obtain a final feedstock gel composition of 4.09 Na2O:0.95
Al2O3:9.5 SiO2:171 H2O. The resultant seed and feedstock gels were aged further at room
temperature for 1 day under stirring. Then, the seed gel was added to the feedstock gel at
once and the resultant gel was shaken vigorously in order to mix homogeneously. After
additional aging at room temperature for 5 h under stirring, the gel was hydrothermally aged
for 12 h in a polypropylene bottle in an oven at 100 °C under static condition. During this
time, white solid precipitate was gradually formed at the bottom of the polypropylene bottle,
which was collected by filtration with funnel filter, washed with deionized water to remove
chemical residues dissolved in water, and dried in an oven at 120 °C. The resultant zeolite is
+
designated as NaY, or Na -exchanged FAU(Y) zeolite.
For the synthesis of zeolite LTA, sodium aluminate was mixed with aqueous NaOH and
stirred until dissolution in a polypropylene bottle. Separately, sodium metasilicate (Sigma
Aldrich, 45.5 wt% SiO2) as a silica precursor was mixed with aqueous NaOH and stirred until
dissolution. The two solutions were mixed together and shaken vigorously for a final gel
composition of 3.165 Na2O:1 Al2O3:1.926 SiO2:128 H2O. The resultant thick gel was
transferred from the polypropylene bottle to a Teflon-lined stainless steel autoclave for
hydrothermal treatment in an oven at 100 °C under tumbling condition. After 4 h treatment,
white solid precipitate was collected by the aforementioned procedure. The resultant zeolite is
+
designated as NaA, or Na -exchanged LTA zeolite.
To incorporate of Cu(II) ions into the aluminosilicate frameworks of zeolites, desired

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amounts of aqueous solutions of Cu(NO3)2 (0.01 M) was mixed with 1.0 g of each
synthesized zeolite. After stirring at room temperature for 17 h in a polypropylene bottle, the
zeolites were collected by filtration, washed with deionized water, and dried in an oven at
1
20 °C. The oxidation states of Cu ions in the catalyst were analyzed by X-ray photoelectron
spectroscopy (XPS) as summarized in Fig. S2 (see Supplementary Information for
experimental details of XPS and their brief discussion). It is widely known that the Cu ions in
the zeolite can possess both +2 and +1 oxidation states, among which +2 is accepted as the
most probable oxidation state. Similarly, Cu ions in all the catalysts prepared in this work
possessed +2 oxidation state as the main portion. Therefore, for simplicity, nomenclature of
Cu(II) is used in the catalyst name hereafter. The nomenclatures of the resultant Cu(II) ion-
exchanged zeolites are summarized in Table 1, and were used as catalysts.
2
.2. Preparation of ordered mesoporous silica (OMS)
To synthesize ordered mesoporous silica, SBA-15, 4 g of Pluronic triblock copolymer (P123,
HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H, Sigma Aldrich, Mn ≈ 5,800) was
dissolved in 144 mL of water containing 7.9 g of HCl (Daejung, 35%), which was stirred at
3
5 °C until P123 was fully dissolved and the solution turned clear. Into this solution, 8.6 g of
tetraethylorthosilicate (TEOS, Sigma Aldrich, 98%) was added and stirred for 1 day at 35 °C.
The final solution was hydrothermally treated for 1 day in a polypropylene bottle in an oven
at 100 °C under static condition. The white solid precipitate formed at the bottom of the
polypropylene bottle was collected by filtration with funnel filter, washed with 1 vol% HCl in
ethanol to remove chemical residues dissolved in water, and dried in an oven at 120 °C. The
resultant powder sample was calcined at 550 °C for 4 h in air in order to remove the organic
species (i.e. P123), and the final sample was designated SBA-15. Thereafter, SBA-15 was
aluminated using AlCl3 (TCI, 98%) as an aluminum precursor. In a typical synthesis, 1 g of

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SBA-15 was mixed with 20 mL of EtOH in a round-bottomed flask, then 0.44 g of AlCl3 was
added into this solution under stirring. After stirring at room temperature for 1 h, EtOH was
removed by evaporation using a rotary evaporator, and the resultant solid powder was
collected and dried in an oven, and calcined at 550 °C for 4 h in air. The resultant sample was
designated as Al-SBA-15, with a Si/Al ratio of 5:1.
For the incorporation of Cu(II) ions to Al-SBA-15, 1 g of Al-SBA-15 was mixed with 300
mL of NaCl solution (0.1 M) in a polypropylene bottle, stirred for 2 h at room temperature,
and the residue was collected by filtration, washed with deionized water, and dried in an oven
+
at 120 °C. The resultant Na -exchanged Al-SBA-15 was further ion-exchanged with 0.01 M
Cu(NO3)2 aqueous solution following the same ion-exchange procedure described above. The
resultant Cu(II)-exchanged Al-SBA-15 catalyst was also analyzed with XPS, which
confirmed that most of Cu possesses +2 as oxidation number (see Fig. S2 in Supplementary
Information for experimental details of XPS and their brief discussion). The resultant Cu(II)-
exchanged Al-SBA-15 was designated NaCuOMS(0.22) (Table 1).
2
.3. Catalyst Characterization
Powder X-ray diffraction (XRD) patterns were used to analyze the crystallinity of the solid
precipitates obtained above and to determine the zeolite framework structures. The XRD
patterns were obtained using a Rigaku Multiflex diffractometer equipped with a CuKα
radiation (λ = 0.1541 nm) at 40 kV and 30 mA. Scanning electron micrography (SEM)
images were taken with a Hitachi SU-70 instrument, and transmission electron micrography
(TEM) images were taken with a JEOL JEM-2100F instrument with an accelerating voltage
of 200 kV. The amounts of Si, Al, and Cu in the prepared catalysts were determined by
inductively coupled plasma-atomic emission spectroscopy (ICP-AES).
Figure 1 shows XRD patterns of the catalysts prepared in this work. The low-angle XRD

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pattern of NaCuOMS(0.22) showed (100), (110), and (200) reflections, typical of
hexagonally ordered mesoporous structure with p6mm symmetry[32]. The wide-angle XRD
patterns showed five zeolite samples: NaY, NaCuY(0.08), NaCuY(0.11), HCuY(0.11), and
NaCuA(0.03). The first four samples showed XRD patterns corresponding to FAU topology,
and the last sample demonstrated LTA topology. As compared to XRD pattern of NaY, Cu(II)-
containing zeolites Y showed slightly less intensive XRD peaks upon ion-exchange of Cu(II),
probably due to the slight collapse of zeolite framework during the ion-exchange process.
Nevertheless, the crystallinity of the Cu(II)-exchanged zeolites produced results expected for
FAU topology. Similarly, the XRD pattern of NaCuA(0.03) was typical for LTA topology.
Figure 2 shows SEM images of NaY and NaCuY(0.11), indicating no significant differences
in morphology and crystallinity for the zeolite Y catalysts was observed upon ion exchange.
Figure 1. X-ray diffraction (XRD) patterns of each catalyst. The low angle XRD pattern of
NaCuOMS(0.22) and high angle XRD patterns of NaY, NaCuY(0.08), NaCuY(0.11),
HCuY(0.11), NaCuA(0.03) and NaCuOMS(0.22) are shown here.

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Figure 2. Scanning electron micrograph images of (A) NaY and (B) NaCuY(0.11).
2
.4. CatalyticActivity of decarboxylative coupling reactions
To evaluate these zeolite-based copper catalysts, iodobenzene (1a) and phenyl propiolic
acid (2) were chosen as standard substrates in the decarboxylative coupling reactions. The
results are summarized in Table 2. To compare with the homogeneous copper catalyst, CuI
was tested as a catalyst in this coupling reaction. We obtained very low product when the
reaction was conducted with CuI in the absence of ligand (entry 1). The non-zeolite-based
copper catalyst NaCuOMS(0.22) did not provide the desired product despite containing
copper (entry 2). Among zeolite-based copper catalysts having similar pore sizes,
NaCuY(0.11) showed higher yield of product than other catalysts (entries 3–5). The higher
catalytic activity of NaCuY(0.11) in entry 4 than HCuY(0.11) in entry 5 might be attributed
to the reaction between base additives in the reaction mixture with acid sites on HCuY(0.11).
+
Since there should be acid sites on the H -containing zeolite (i.e., HCuY(0.11)), these acid
sites may react with acid additives and hence lower the catalytic activity. NaCuA(0.03),
which has a smaller pore size, showed a relatively low product yield (entry 6). When NaY,
which has no copper source in the zeolite, was employed, neither 3a nor 4a were formed

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(
entry 7). This result supported that copper catalytic sites were located inside the zeolite pores.
With this active catalyst NaCuY(0.11), the effect of base was studied. The reaction with
Na2CO3 provided the desired product 3a and the homocoupled product 4a with 89% and 5%
yields, respectively (entry 8). K3PO3 as a base did not give satisfactory results (entry 9).
While Cs2CO3, which performed well as a base in homogeneous Pd-catalyzed
decarboxylative coupling reactions, gave poor yield in our experiments, DBU produced good
yield (entries 10 and 11). Use of other solvents like DMF, toluene, and 1,2-dichlorobenzene
instead of DMSO provided poor yield or no product (entries 12–14). When phenyl acetylene
was employed instead of phenylpropiolic acid, the desired product 3a was formed with 76%
yields (entry 15). However, the reaction with propoiolic acid and iodobenzene did not provide
any coupled product (entry 16). To expand this methodology, we attempted to employ
bromobenzene as a coupling partner, however, no decarboxylative coupled product was found
(
entry 16). Based on these results, the optimized condition for the decarboxylative coupling
reaction is as follows: aryl iodide (1.0 equiv), phenyl propiolic acid (1.0 equiv), NaCuY(0.11)
10 mol% Cu) and Na2CO3 (1.5 equiv) reacted in DMSO at 100 °C for 12 h. The results
(
demonstrated that NaCuY(0.11), which is the Cu(II)-exchanged zeolite Y with average
micropore size of 0.67 nm, showed the best catalytic performances, i.e. high catalytic activity
with high yield for the desired products toward the coupling reaction with various substrates.
Alternatively, NaCuA, which is Cu(II)-exchanged zeolite A having small micropore size
(~0.45 nm) and NaCuOMS(0.22), which is the Cu(II)-exchanged mesoporous aluminosilicate
(Al-SBA-15) with average mesopore size of 10 nm, exhibited low or almost negligible
catalytic activity. Thus, the better catalytic performances of NaCuY(0.11) might be attributed
to the fact that the kinetic diameters of most of the reactants studied herein and the expected
products are matched well with the micropore cavity size of zeolite Y than of other catalysts.
Although kinetic sizes of molecules shown in this work are difficult to determine exactly,

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their cross-sectional diameters can be estimated from the kinetic diameter of phenyl ring (ca.
0
.59 nm) that is contained in all molecules [33]. Among all the catalysts, NaCuY(0.11)
catalyst possesses micropore of 0.67 nm that is very close to the diameter of phenyl ring.
Such tight fit of the reactant molecules inside the micropore cavity of zeolite Y can enhance
collision frequency, which might be one of the reasons for the enhancement of catalytic
activity as compared to other catalysts.
Table 2. Optimized conditions for the zeolite-based copper catalyst in decarboxylative
a
coupling reactions.
Yield (%)
Entry
Catalyst
Base
Solvent
3
13
0
a
4a
12
0
6
11
8
4
0
2
7
3
5
6
1
1
2
3
4
5
6
7
8
9
CuI
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Na2CO3
K3PO4
Cs2CO3
DBU
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMF
NaCuOMS(0.22)
NaCuY(0.08)
NaCuY(0.11)
HCuY(0.11)
NaCuA(0.03)
NaY
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
27
63
42
15
0
89
33
5
1
0
1
1
85
6
0
1
1
1
2
3
4
Na2CO3
Na2CO3
Na2CO3
toluene
1,2-Cl2C6H4
0
0
1
1
1
5
6
7
NaCuY(0.11)
NaCuY(0.11)
NaCuY(0.11)
Na2CO3
Na2CO3
Na2CO3
DMSO
DMSO
DMSO
73
0
0
6
0
0
a
Reaction conditions : 1a (0.3 mmol), 2a (0.3 mmol) and base (0.45 mmol) reacted in solvent
1.5 mL) at 100 °C for 12 h.
Determined by gas chromatography with internal standard.
propiolic acid was employed i
(
b

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c
Phenyl acetylene was employed instead of 2a.
Bromobenzene was employed instead of 1a.
d
To check a leaching out tendency of Cu into reaction mixture, ICP-AES (inductively coupled
plasma atomic emission spectroscopy) was conducted on the reaction solution. When the
reaction was completed, the insoluble portion was removed and the remaining solution was
reused as a catalyst and examined by ICP-AES. When the coupling reaction carried out in the
remaining soulition, no product was formed. And ICP-AES value showed that the
concentration of Cu ion in solution is below the detection limit of instrument. These results
supported that the leaching out amount was estimated not to exceed hundreds ppb
concentration.
Under optimized conditions, a variety of aryl iodides were employed as coupling partner in
the decarboxylative coupling reaction with phenyl propiolic acid; the results are summarized
in Table 3. 2- and 4-Iodotoluenes afforded the desired products 3b and 3c with 91% and 95%
yields, respectively (entries 1 and 2). 4-Iodoanisole afforded 3d with 76% yield, which is
slightly lower than others (entry 3). 1-Chloro- and 1-fluoro-4-iodobenzenes were converted to
3
e and 3f with 97% and 90% yields, respectively. No coupling occurred at the C–Cl and C–F
bonds (entries 4 and 5). 1-Iodonapthalene also gave the desired product with good yield
entry 6). Aryl iodides bearing electron withdrawing groups such as nitrile, acetyl, and nitro
(
groups afforded the corresponding diaryl alkynes 3h, 3i, and 3j with 91%, 89%, and 95%
yields, respectively (entries 7–9). When substituted aryl propiolic acids were allowed to react
with iodobenzene, the corresponding desired products were formed with good yields (entries
1
0 – 13). We found that the selectivities in the formation of diarylalkyne and diaryldiyne
were higher in the aryl iodides bearing electron-withdrawing groups than those bearing

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electron-donating groups. In addition, a zeolite-based copper catalyst showed good activity
and selectivity in decarboxylative coupling reactions with a variety of aryl iodides.
Table 3. Catalytic activity of zeolite-based copper catalyst in decarboxylative coupling
a
reactions
1
2
Yield
c
Entry
1
Ar I
Ar
Product
Select.
b
(%)
Ph
3b
91
10.2:1
2
3
4
5
Ph
Ph
Ph
Ph
3c
3d
3e
3f
95
76
97
90
11.7:1
8.5:1
14.5:1
12.5:1
6
Ph
3g
92
14.3:1
7
8
9
Ph
Ph
Ph
3h
3i
91
89
34.3:1
25:1
3j
3c
3d
3e
95
92
91
92
58.5:1
42.1:1
10:1
1
0
Ph-I
Ph-I
Ph-I
11
1
2
12.7:1

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1
3
Ph-I
3f
92
22:1
a
Reaction conditions : 1 (0.3 mmol), 2 (0.3 mmol), NaCuY(0.11) (12 mg), and Na2CO3 (0.45
mmol) reacted in DMSO (1.0 mL) at 100 °C for 12 h.
b
Isolated yield
c
The ratio of 3 and 4a
2
.5. Experimental procedure of decarboxylative couplings
Phenylpropiolic acid (43.8 mg, 0.3 mmol), iodobenzene (61.2 mg, 0.3 mmol), Na2CO3 (47.6
mg, 0.45 mmol), NaCuY (12 mg, 0.03 mmol) were added to a vial under DMSO (1.0 mL).
The resulting mixture was heated to 100 ℃ for 12 h under vigorous stirring. After complete
reaction, the reaction mixture was treated with water and extracted with EtOAc. The organic
layer was dried under MgSO4 and concentrated by using vacuum evaporation. The crude
mixture was purified by column chromatography.
2
.6. Recyclability of NaCuY(0.11)
Next, the potential recyclability of NaCuY(0.11) was investigated in the model
decarboxylative coupling reaction between phenyl propiolic acid and iodobenzene. The
reaction was conducted in DMSO at 100 °C for 12 h. After cooling to 25 °C, the organic
phases were extracted with ethyl acetate and the yield was determined by gas
chromatography with an internal standard. The precipitated NaCuY(0.11) was washed with
ethyl acetate and water, and then transferred to a new reaction vial containing fresh starting
reagents. As shown in Figure 3, this process was repeated six times with high product yields
in all cases.

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Figure 3. Recyclability of NaCuY(0.11) in the decarboxylative coupling reaction with Na
3
. Conclusion
We demonstrated that the aluminosilicate framework of zeolite Y is very useful for binding
Cu(II) cations in an organic-free environment, which can be used as a recyclable
heterogeneous catalyst for decarboxylative coupling reactions with aryl iodides. The Cu(II)-
exchanged zeolite Y showed high catalytic activity and high yield of the desired product,
which might be attributed to the good fit of reactant and product inside the micropores
wherein the reaction takes place. A variety of aryl iodides afforded the desired products with
good yields under this catalytic system. In addition, catalytic activity and product selectivity
were sustained without any significant change over six rounds of reaction. Therefore, zeolite-
based copper catalysts seem promising as catalytic systems over homogeneous catalysts due
to the reusability and economic preparations.
Acknowledgments
This research was supported by the National Research Foundation of Korea (NRF) grant

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funded by the Korean government (MSIP) (NRF-2015R1A4A1041036).
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Graphical Abstract

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Highlights
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
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A zeolite-based copper catalyst is a readily prepared and inexpensive system.
This catalytic system is ligand-free with a reusable heterogeneous catalyst.
This catalytic system shows good yields in decarboxylative coupling reaction.