Metal Sulfonate Polymers as Catalysts for the Heterogeneous Acylation of Aromatic Derivatives

Article abstract of DOI:10.1002/ejoc.201600266

A series of metal sulfonate salts attached to a poly(ether ether ketone) (PEEK) polymer were prepared by ultrasonic activation and then examined as heterogeneous catalysts in the Friedel–Crafts acylation of aromatic derivatives.

Full text of DOI:10.1002/ejoc.201600266

DOI: 10.1002/ejoc.201600266
Full Paper
Heterogeneous Catalysis
Metal Sulfonate Polymers as Catalysts for the Heterogeneous
Acylation of Aromatic Derivatives
Vincent Morizur,[a] Daphné Hector,[a] Sandra Olivero,[a] Jean Roger Desmurs,[b] and
Elisabet Duñach*[a]
Abstract: A series of metal sulfonate salts attached to a ultrasonic activation and then examined as heterogeneous cat-
poly(ether ether ketone) (PEEK) polymer were prepared by alysts in the Friedel–Crafts acylation of aromatic derivatives.
Results and Discussion
Introduction
1. Preparation of a Polymeric Sulfonic Acid Catalyst
The availability of active catalysts that are easy to recycle consti-
tutes an important challenge in the field of catalysis. In this
context, the development of heterogeneous catalysis is of great
importance, as this type of reaction system facilitates the sepa-
ration of the catalyst from the product by simple filtration.[1]
The commercially available polymer PEEK [poly(ether ether ket-
one), 1] was chosen for functionalization.[7] This polymer is
known for its high thermal and mechanical stability as well as
its chemical resistance.[8] In addition, there are many available
options for its functionalization to afford various controllable
functional groups on a relatively polar skeleton. Despite its sta-
bility, the carbonyl group of polymer 1 has been converted
into a thioacetal[9] and an imine.[10] The electrophilic aromatic
substitution of 1 has also been reported by using a chloro-
methyl derivative,[11] a sulfonic acid, or a sulfonyl chloride.[12]
However, these functionalization processes have involved poly-
mer reticulation, and to the best of our knowledge, no catalytic
processes using PEEK derivatives have been described in the
literature.
We are interested in catalysis by using protic and Lewis acids
that are supported on a polymer framework. In the area of het-
erogeneous protic and Lewis acid catalysis, porous materials
such as natural and synthetic zeolites or sulfonic perfluorinated
polymers such as Nafion have shown their efficiency and speci-
ficity in several catalytic processes.[2] Herein, we report the
preparation of new polymeric materials in the form of metal
salts and their use as catalysts in the Friedel–Crafts acylation of
aromatic derivatives.
The Friedel–Crafts acylation is an essential transformation for
the C–H functionalization of aromatic compounds and is highly
valued in the chemical industry for the preparation of interme-
diates for applications such as pharmaceuticals, paint additives,
flavors, plasticizers, and dyes.[3] Strong Lewis acids, mainly de-
We assembled a chlorosulfonation protocol that enabled the
preparation of chlorosulfonated polymer 2 in an almost quanti-
tative yield by controlling the reaction conditions and without
the need for reticulation (Scheme 1). This sulfonation occurred
exclusively at the diether aromatic unit, and its monofunctional-
ization was achieved in 97–100 % yield. The amount of di-
–
rived from metal sulfonates such as triflates (CF3SO3 ) and tri-
flimides [(CF3SO2)2N–], have previously shown their high cata-
lytic activity in these reactions.[4] Thus, we propose that func-
tionalized polymers grafted with sulfonic acid groups can be
used in the same sense. In related examples, adsorbed AlIII tri-
flate on polystyrene[5] and YbIII perfluoroctanesulfonate on Am-
berlyst A21[6] have been reported as efficient catalysts for acyl-
ation reactions.
1
chlorosulfonation could be quantified by H NMR analysis and
the integration of the signal at δ = 8.20 ppm, which corre-
sponds to the proton of the disulfonated aromatic unit. This
1
signal at δ = 8.20 ppm was absent from the H NMR spectrum
of polymer 2.
[a] Institut de Chimie de Nice UMR 7272, Université Nice Sophia Antipolis,
Faculté des Sciences,
Parc Valrose, 06108 Nice cedex 2, France
E-mail: dunach@unice.fr
http://icn.unice.fr
Scheme 1. Preparation of chlorosulfonated polymer 2 (DMF = N,N-dimethyl-
formamide).
[b] CDP-Innovation, G2C Business Center,
63 Rue Andre Bollier, 69307 Lyon, France
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejoc.201600266.
The hydrolysis of 2 in water at reflux allowed for the quanti-
tative preparation of the sulfonic acid polymer 3 as a yellow
powder (Scheme 2). Polymer 3 is insoluble in most organic sol-
Eur. J. Org. Chem. 0000, 0–0
1
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Scheme 2. Preparation of sulfonic acid polymer 3.
vents, and partially soluble in dimethyl sulfoxide (DMSO), eth-
anol, and water.
2. Preparation of Lewis Acid Polymer Catalysts
Polymer 3 was used for the preparation of a series of polymer
Scheme 4. Acylation of 1,3-dimethoxybenzene (5a).
metal salts, namely, those of In3+, Bi3+, Cu2+, Sm3+, and Gd3+
.
The salts were prepared by carrying out a redox reaction be-
tween sulfonic acid 3 and the corresponding metal with ultra-
sonic activation (35 kHz, 70 W, Sonometer UIP1000 hd Hiel-
sher)[13] in an aqueous solution (Scheme 3). The yields obtained
for the five polymers 4a–4e were almost quantitative, as indi-
cated in Table 1.
The amount of acylated product 6a was monitored by GC
analysis using dodecane as an internal standard. The kinetic
evolution of the reaction with the different polymeric catalysts
is illustrated in Figure 1.
Scheme 3. Ultrasonic (US) preparation of polymer metal salts.
Figure 1. Kinetic evolution of the acylation of 5a with polymers 3 and 4a–4e
(10 mol-%) in nitromethane at reflux [SPEEK = sulfonated poly(ether ether
ketone)].
Table 1. Preparation of polymeric metal salts by ultrasonic activation.
M0
Time [h]
Product
Yield [%]
Indium(III) and copper(II) derivatives 4a and 4c, respectively,
were determined to be the most active catalysts. A yield of
82 % for 6a was attained in only 10 min by using the InIII-based
polymer. Protic polymer 3 was less efficient and demonstrated
the similar low catalytic activity that was observed with the
BiIII-, SmIII-, and GdIII-based polymers (Figure 1).
In
Bi
Cu
Sm
Gd
12
18
18
12
14
In3+ (4a)
Bi3+ (4b)
Cu2+ (4c)
Sm3+ (4d)
Gd3+ (4e)
92
97
95
98
98
In the acylation of other aromatic compounds such as anis-
ole (5b) and 1,2-dimethoxybenzene (5c), the InIII-based catalyst
4a offered better results than those afforded by CuII polymer,
4c. These results are summarized in Table 2.
Thus, InIII-based polymer 4a was used as the catalyst for the
acylation of various other (hetero)aromatic substrates. The re-
sults are summarised in Table 3. For the series of activated com-
pounds that were examined, the yields of products 6a–6j were
generally good, in particular those produced by the anisole and
thiophene derivatives.
The functionalized polymers 4a–4e were insoluble in water,
and thus, they were isolated by filtration, rinsed with water,
and further dried under vacuum. These polymers were slightly
soluble in DMSO and insoluble in most organic solvents.
3. Acylation Reactions Catalysed by Polymer-Supported
Lewis Acids
Polymers 3 and 4a–4e were then examined as protic and Lewis
acid heterogeneous catalysts, respectively, of the Friedel–Crafts
The catalytic activity of this newly prepared catalyst was also
acylation reaction of aromatic derivatives 5. 1,3-Dimethoxy- compared to that of the corresponding metal tosylates
benzene (5a) was chosen as the model compound for these [M(OTs)n], mesylates [M(OMs)n], and triflates [M(OTf)n] under ho-
studies. The acylations were performed in nitromethane at re- mogeneous catalytic conditions.[14] Figure 2 shows the kinetic
flux with 10 mol-% of the catalyst (metal content) in the pres- evolution of the acylation of 1,3-dimethoxybenzene (5a) with
ence of acyl chloride as the acylating agent (Scheme 4).
different InIII catalytic systems.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
2
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Table 2. Comparison of the catalytic activity of polymers 4a and 4c.[a]
Table 3. Acylation of (hetero)aromatic derivatives catalyzed by 4a.[a]
[a] Reagents and conditions: in refluxing nitromethane, catalyst (metal based,
10 mol-%), and acyl chloride (2 equiv.). For details, see Supporting Informa-
tion.
Figure 2. Acylation of 1,3-dimethoxybenzene (5a) by different InIII sulfonate
salts under the conditions described in Table 2.
As expected, the most active catalyst was In(OTf)3, which
allowed for the quantitative acylation of 5a in less than 5 min.
In(OTf)3 was also slightly more active than the corresponding
polymer 4a. The kinetics of the acylation of 5a under In(OTs)3
catalysis and homogeneous conditions is comparable to that of
polymer 4a under heterogeneous conditions.
Next, the possibility to recycle the catalyst by simple filtra-
tion was examined for the reaction of polymer 4a and substrate
5a under the conditions reported in Table 2. Each run was ex-
amined after 10 min. After five catalytic cycles, there was no
significant loss in the catalytic activity of the polymer, and the
yields of 6a were maintained between 75 and 85 %. Finally, the
stability of the catalyst was also studied by thermogravimetric
[a] Reagents and conditions: in refluxing nitromethane, catalyst (metal-based,
10 mol-%), and acyl chloride (2 equiv.). For details, see Supporting Informa-
tion.
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
3
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
washed with water (2 × 10 mL) and dried under vacuum overnight
(1 × 10–2 mbar). The filtrate contained no metal residue.
analysis (TGA), which indicated a thermal stability of 4a of up
to 250 °C (see Supporting Information).
General Procedure for Acylation Reaction: To a Schlenk flask
were added dry nitromethane (20 mL), 1,3-dimethoxybenzene or
the aromatic derivative (2 mmol), the catalyst (metal- or proton-
based, 10 mol-%), and acetyl chloride (4 mmol). The resulting solu-
tion was heated at reflux, and the progress of the reaction was
followed by gas chromatography. Extraction with diethyl ether and
purification by column chromatography (AcOEt/Et2O, 90:10) af-
forded the corresponding product. The acylated derivatives are
known compounds, and the 1H and 13C NMR spectroscopic and MS
data were in agreement with the literature data.
Conclusions
Supported protic and Lewis acid catalysts were prepared by
starting from the commercially available aromatic PEEK poly-
mer. Its sulfonation allowed for the preparation of a protic sulf-
onic acid catalyst, which was further transformed into a series
of metal sulfonate salts by ultrasonic activation. These sup-
ported Lewis acids were obtained in almost quantitative yields.
The efficiency of these polymers as heterogeneous catalysts
was examined in the Friedel–Crafts acylation of activated aro-
matic compounds. These studies showed that InIII sulfonate
polymer 4a was the most active catalyst of the series. The cata-
lytic activity of this polymeric catalyst was also compared to
that of the corresponding nonpolymeric analogues. The InIII
polymer catalyst 4a could be recycled for use in five runs with-
out the loss of its catalytic activity.
Acknowledgments
The authors thank the Conseil Régional Paca, France for the
scholarship given to D. H. and V. M., and for the partial support
of the ANR French project ALEA, 2013.
Keywords: Synthetic methods · Polymers · Heterogeneous
catalysis · Acylation · Indium
[1] B. Clapham, T. S. Reger, K. D. Janda, Tetrahedron 2001, 57, 4637–4662.
[2] G. Sartori, R. Maggi, Chem. Rev. 2011, 111, 181–214.
[3] J.-R. Desmurs, S. Ratton, The Roots of Organic Development, Elsevier Sci-
ence B. V., Amsterdam, 1996.
[4] a) S. Antoniotti, S. Poulain-Martini, E. Duñach, Synlett 2010, 2973–2988;
b) M. Kawamura, D.-M. Cui, S. Shimada, Tetrahedron 2006, 62, 9201–9209;
c) S. Antoniotti, V. Dalla, E. Duñach, Angew. Chem. Int. Ed. 2010, 49, 7860–
7888; Angew. Chem. 2010, 122, 8032; d) J. R. Desmurs, M. Labrouillère,
C. Le Roux, H. Gaspard, A. Laporterie, J. Dubac, Tetrahedron Lett. 1997,
38, 8871–8874; e) S. Kobayashi, I. Komoto, J.-I. Matsuo, Adv. Synth. Catal.
2001, 343, 71–74; f) J. Ross, J. Xiao, Green Chem. 2002, 4, 129–133.
[5] K. P. Borujeni, A. R. Massah, React. Funct. Polym. 2006, 66, 1126–1131.
[6] W.-B. Yi, C. Cai, J. Fluorine Chem. 2008, 129, 524–528.
[7] a) W. H. Bonner Jr., US3065205, 1962; b) J. B. Rose, GB1414422A, 1975;
J. B. Rose, P. A. Staniland, EP1879A1, 1979.
[8] a) D. P. Jones, D. C. Leach, D. R. Moore, Polymer, 1985, 26, 1385–1393
(August 1985, conference issue); b) A. Jonas, R. Legras, Polymer 1991, 32,
2691–2706; c) S. D. Hudson, D. D. Davis, A. J. Lavinger, Macromolecules
1992, 25, 1759–1765.
Experimental Section
Preparation of 2: To a suspension of PEEK (1, 10.0 g, 34.7 mmol)
in dry CH2Cl2 (350 mL) was added chlorosulfonic acid (18.5 mL,
278 mmol). The resulting suspension was stirred at room tempera-
ture for 15 h. The supernatant was separated, and thionyl chloride
(76 mL, 1.04 mol) and dry N,N-dimethyformamide (11 mL,
174 mmol) were added to the remaining gel. The resulting red
slurry was stirred at room temperature for 2 h and then further
diluted by the slow addition of dry THF (200 mL). The upper layer
of the resulting two-phase system was separated and added drop-
wise to 2-propanol (500 mL) that was stirred. The resulting precipi-
tate was removed by filtration, washed with acetonitrile (2 ×
250 mL), and dried under vacuum to give polymer 2 (13.2 g,
34.1 mmol, 98 % yield) as a white solid. 1H NMR (200 MHz,
[D6]DMSO): δ = 7.94–7.68 (m, 4 H), 7.51 (d, J = 2.9 Hz, 1 H), 7.33–
6.92 (m, 6 H) ppm. IR: ν = 1654, 1597, 1473, 1375, 1257, 1217, 1159,
˜
927, 764 cm–1
.
[9] H. M. Colquhoun, F. P. V. Paoloni, M. G. B. Drew, P. Hodge, Chem. Commun.
2007, 3365–3367.
Preparation of 3: A stirred suspension of 2 (10.0 g, 25.9 mmol) in
water (250 mL) was heated at reflux for 15 h. The solution was
concentrated under vacuum, and the resulting solid was crushed,
washed with acetonitrile (2 × 500 mL), removed by filtration, and
dried under vacuum to give polymer 3 (9.5 g, 25.8 mmol, 99 %
yield) as a yellow solid. 1H NMR (200 MHz, [D6]DMSO): δ = 7.94–
7.66 (m, 4 H), 7.51 (d, J = 2.9 Hz, 1 H), 7.32–6.94 (m, 6 H) ppm. IR:
[10] I. Manolakis, P. Cross, H. M. Colquhoun, Macromolecules 2011, 44, 7864–
7867.
[11] X. Yan, G. He, X. Wu, J. Benziger, J. Membr. Sci. 2013, 429, 13–22.
[12] a) M. L. Di Vona, D. Marani, C. D'Ottavi, M. Trombetta, E. Traversa, I.
Beurroies, P. Knauth, S. Licoccia, Chem. Mater. 2006, 18, 69–75; b) X. Zhao,
Q. Zhang, L. Xue, Q. Shi, K. Tao, J. Appl. Polym. Sci. 2013, 130, 1058–1063;
c) S. Kaliaguine, S. D. Mikhailenko, K. P. Wang, P. Xing, G. Robertson, M.
Guiver, Catal. Today 2003, 82, 213–222; d) W. Zhang, V. Gogel, K. A. Fried-
rich, J. Kerres, J. Power Sources 2006, 155, 3–12.
[13] a) N. Legrave, A. Couhert, S. Olivero, J.-R. Desmurs, E. Duñach, Eur. J. Org.
Chem. 2012, 901–904; b) J. R. Desmurs, E. C. I. Duñach, S. Olivero, S.
Antoniotti, WO2012010752A1, 2012.
ν = 3371, 1638, 1596, 1471, 1220, 1159, 1023, 929, 859 cm–1
.
˜
General Procedure for Preparation of 4: Polymer 3 (368 g/mol,
2.7 mmol) was added to water (30 mL, 0.092 ), and the corre-
M
sponding metal (0.32 equiv. for a trivalent metal and 0.48 equiv. for
a divalent metal) was added to the solution. The mixture was placed
under ultrasonic activation (35 kHz, 70 W, Sonometer UIP1000 hd
Hielsher) at room temperature. Upon complete consumption
of the metal, the solution was filtered, and the precipitate was
[14] V. Morizur, J. Szafranek, D. Bonhomme, S. Olivero, J. R. Desmurs, E.
Duñach, Tetrahedron 2015, 71, 6813–6817.
Received: March 18, 2016
Published Online: ■
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
4
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Heterogeneous Catalysis
A series of metal sulfonate salts at-
tached to a poly(ether ether ketone)
(PEEK) polymer were prepared by ul-
trasonic activation and then examined
as heterogeneous catalysts in the
acylation of aromatic derivatives.
V. Morizur, D. Hector, S. Olivero,
J. R. Desmurs, E. Duñach* ............... 1–5
Metal Sulfonate Polymers as Cata-
lysts for the Heterogeneous Acyl-
ation of Aromatic Derivatives
DOI: 10.1002/ejoc.201600266
Eur. J. Org. Chem. 0000, 0–0
www.eurjoc.org
5
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim