P-Sulfonic acid calix[4]arene-functionalized alkyl-bridged organosilica in esterification reactions

Article abstract of DOI:10.1039/c6ra02908f

Two new p-sulfonic acid calix[4]arene- and p-sulfonic acid calix[6]arene-functionalized organosilica have been synthesized using a sol-gel method and applied as heterogeneous catalysts in esterification reactions. The catalytic performance was evaluated using the esterification of carboxylic acids with ethanol, and good catalytic activity (i.e., 55-88%) was observed under the optimum reaction conditions. This study reports the first promising example of the successful employment of calix[n]arenes as a heterogeneous catalyst for catalytic esterification. The catalyst was easily separated by filtration and reused five times without any significant loss of activity.

Full text of DOI:10.1039/c6ra02908f

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: S. A. Fernandes, J.
V. de Assis, I. B. Braga, P. Abranches, A. G. Sathicq, G. Romanelli, A. G. Sato and O. M. Portilla Zuñiga, RSC
Adv., 2016, DOI: 10.1039/C6RA02908F.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Page 1 of 6
RSC Advances
View Article Online
DOI: 10.1039/C6RA02908F
Journal Name
RSCPublishing
ARTICLE
p-Sulfonic acid calix[4]arene-functionalized alkyl-
bridged organosilica in esterification reactions
Cite this: DOI: 10.1039/x0xx00000x
J. V. de Assis,a P. A. S. Abranches,a I. B. Braga,a O. M. P. Zuñiga,b A. G.
Sathicq,b G. P. Romanelli,b A. G. Satoa and S. A. Fernandesa,*
Received 00th January 2012,
Accepted 00th January 2012
Two new
pꢀsulfonic acid calix[4]areneꢀ and pꢀsulfonic acid calix[6]areneꢀfunctionalized
organosilica have been synthesized using the solꢀgel method and applied as heterogeneous
catalysts in esterification reactions. The catalytic performance was evaluated using the
esterification of carboxylic acids with ethanol, and good catalytic activity (i.e., 55ꢀ88%) was
observed under the optimum reaction conditions. This study reports the first promising
DOI: 10.1039/x0xx00000x
www.rsc.org/
example of successful employment of calix[n]arenes as a heterogeneous catalyst for
catalytic esterification. The catalyst was easily separated by filtration and reused five times
without any significant loss of activity.
Introduction
Esters are among the most important functional groups in
organic synthesis due to their usefulness.1 Esters have attracted
more attention due to their wide applications in polymers,
plastic
derivatives,
perfumes,
flavours,
chemicals,
pharmaceutical and agrochemicals intermediates, and
biodiesel.2
However, to develop an environmentally benign process and
simplify the existing processes associated with homogeneous
acid catalysts, substantial efforts have been focused on
exploring heterogeneous solid acid catalysts, which offer
significant advantages, such as easy recovery, little corrosion,
low toxicity and environmental safety.3 Recently, the
combination of the chemical properties of organoꢀsulfonic acid
catalysts and the physical properties of different nanomaterials
Fig. 1 Molecular structures of the two catalysts:
p
ꢀsulfonic acid
calix[4]arene (CX4SO3H) and
(CX6SO3H).
pꢀsulfonic acid calix[6]arene
Results and discussion
has been
a
subject of great interest in heterogeneous
catalysis.3a,4
To develop catalytic methodologies with easy recovery, little
corrosion, low toxicity and environmental safety for the
esterification of carboxylic acids, we designed an effective
In last two decades, research interest in calix[
n
]arene chemistry
has increased dramatically due to their applications in several
fields of chemistry related to supramolecular chemistry
including molecular recognition5, selfꢀassembling systems6,
mechanically interlocked molecules7, and nanoporous
materials8. The application of calix[
n]arenes as catalysts in
organic transformations has become very popular.9 In addition,
we have recently reported excellent results for the esterification
system using calix[
(Scheme 1).
n]arenes as a heterogeneous catalyst
Scheme 1 Synthesis of catalysts 1a and 1b
.
of carboxylic acids using
(CX4SO3H) or ꢀsulfonic acid calix[6]arene (CX6SO3H) as a
homogeneous catalyst (Fig. 1).10 In this study, we report novel
calix[ ]arenes catalysts with Brønsted acid and heterogeneous
pꢀsulfonic acid calix[4]arene
p
n
properties as well as results from esterification reactions to
synthesize carboxylic esters. To the best of our knowledge, this
is the first application of
heterogeneous catalysts in these esterification reactions.
pꢀsulfonic acid calix[n]arenes as
p
ꢀSulfonic acid calix[4]arene (CX4SO3H) and pꢀsulfonic acid
calix[6]arene (CX6SO3H) were synthesized in our laboratory
This journal is © The Royal Society of Chemistry 2013
J. Name., 2013, 00, 1-3 | 1

RSC Advances
Page 2 of 6
View Article Online
ARTICLE
Journal Name
DOI: 10.1039/C6RA02908F
(Scheme 1) according to previously reported protocols.11 For the initial investigation of the use of 1a and 1b as catalysts
Catalysts 1a and 1b were synthesized using a solꢀgel technique. for esterification, palmitic acid and ethanol were employed as
A mixture of CX4SO3H or CX6SO3H, water and a hydrochloric substrates under the optimal reaction conditions (i.e., catalyst
acid solution was added to tetraethyl orthosilicate. The mixture loading, time, and reuse of the catalyst). The results from the
was stirred for 5 h at room temperature. Then, the mixture was optimization of the catalyst concentration (2.0 mol %, 2.5 mol
allowed to stand for 3 days, and after breaking the formed % and 5 mol %) are listed in Table 1. The evaluation of three
hydrogel with a Teflon stick, the sample was dried in a vacuum concentrations of catalyst 1a indicated a slight increase in the
for one week at room temperature (Scheme 1 and Fig. 2). conversion of palmitic acid to ethyl palmitate (Table 1, entries
Catalysts 1a and 1b were characterized based on acidity and 1ꢀ3). For catalyst 1b, an increase in the catalyst concentration
XRD.
had a significant effect on the yield of ethyl palmitate (Table 1,
entries 4ꢀ6). The differences observed between the catalytic
activities of 1a and 1b may be due to the presence of water,
which is a byꢀproduct of the esterification reaction.
Table 1 Effect of the amount of catalyst 1a or 1b and time on the
conversion of ethyl palmitate.a
Fig. 2 Formation of the 1aꢀbased hydrogel induced by TEOS.
(a) 0 h, (b) 1 h, (c) 24 h, (d) 72 h, (e) 72 h, (f) after breaking the
formed hydrogel, and (g) hydrogel after washing and drying in
a vacuum.
Time (h)
Yield (%)b
Entry
Catalyst
Catalyst (mol %)
1
2
3
4
5
6
7
8
2
2.5
5
2
2.5
5
4
4
4
4
4
4
6
8
88
91
91
67
78
87
90
93
1a
1a
1a
1b
1b
1b
1a
1a
The ion exchange capacities of 1a were determined by acidꢀ
base titration and potentiometric titration. The acid capacity of
the sample (catalyst 15 %) was determined by titration with 5 x
10ꢀ3 M NaOH (aq).12 The result in terms of mmol H+/g for the
catalyst was 0.32 mmol H+/g catalyst. The strength of the acid
sites can be classified according to the following scale: E > 100
mV (very strong sites); 0 <E< 100 mV (strong sites); −100 <E<
0 mV (weak sites) and E < −100 mV (very weak sites).13 The
acid strength for 15% catalyst was 205 mV, indicating the
presence of very strong sites.
Typical XRD patterns of amorphous materials were observed
for the supported 1a samples in Fig. 3. The XRD pattern peaks
were obtained between 5° and 50°. The absence of crystalline
1a peaks in the XRD pattern of the supported samples cannot
be ruled out because they may be less than 40 Å in size, which
is beyond the detection limit of the XRD technique. The broad
Xꢀray diffraction patterns may indicate longꢀrange disordered
nature of the silica.
2
2
aReaction conditions: palmitic acid (100 mg) and ethanol (10 mL) was
performed at 80 °C. bAnalysed by GCꢀMS and 1H NMR.
As described by Fernandes et al. in 2014,
calix[ ]arenes catalytic activity is affected by increasing the
amount of water, and this effect was more pronounced for
pꢀsulfonic acid
n
p
ꢀ
sulfonic acid calix[6]arene.10a Therefore, catalyst 1a exhibited
the best conversion, and the concentration used for subsequent
studies was 2 mol %. The effect of time on the conversion of
palmitic acid to ethyl palmitate was also investigated (Table 1).
The conversion of ethyl palmitate increased slightly from 88%
to 90% and 93% with prolonged reaction times of 4 h, 6 h and 8
h (Table 1, entries 1, 7 and 8). Based on the conversion and
selectivity results, a reasonable reaction time is 4 h.
The catalytic activities of the heterogeneous catalysts (1a and
1b) were compared to those of the CX4SO3H and CX6SO3H
homogeneous catalysts (Table 2). The CX4SO3H and
CX6SO3H homogeneous catalysts exhibited catalytic activities
that were similar to that of 1a and higher than that of catalyst
1b (Table 2, entries 1ꢀ4). Similarly, both strong Brønsted acid
heterogeneous amberlyst 15 and H3PW12O40 exhibited a lower
activity than the 1a catalyst, and the ethyl palmitate yield did
not exceed 80% (Table 2, entries 5 and 6). The ethyl palmitate
yield in the catalystꢀfree or matrix (TEOS) reactions was lower
than 5% (Table 1, entries 7 and 8).
Fig. 3 XRD patterns of catalyst 1a
.
To determine if catalyst leaching occurred, an experiment using
the optimal reaction conditions was performed for only 1 h.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 3 of 6
Journal Name
RSC Advances
View Article Online
ARTICLE
DOI: 10.1039/C6RA02908F
Then, the mixture was cooled, catalyst 1a was removed by
filtration, and the conversion of palmitic acid was confirmed.
The mixture was heated again at 80 °C for 3 h but no
significant reaction progress was observed, demonstrating that
leaching did not occur.
100%
80%
60%
40%
20%
0%
88
88
88
87
86
Table 2 Effect of different catalysts on the conversion of palmitic
acid to ethyl palmitate.a
1
2
3
4
5
Cycle
Yield (%)c
Entry
Catalyst
Catalyst (mol%)
Fig. 4 Reuse of 1a catalyst for the esterification of palmitic acid
with ethanol.
1
2
3
4
5
6
7
8
2b
2b
2
2
2
2
2
2
88
67
91
89
79
67
< 5
< 5
1a
1b
CX4SO3H
CX6SO3H
Amberlyst 15
H3PW12O40
TEOS
Experimental
Chemicals and Reagents. All of the chemicals were obtained
from commercially available sources and used without further
purification. The reactions did not require anhydrous
conditions. The GCꢀMS analyses were carried out on a
Shimadzu GCꢀ2010 Plus gas chromatograph coupled with a MS
QP2010 Ultra Shimadzu mass spectrometer (Tokyo, Japan),
using a DB5 capillary column (30 m length, 0.25 mm id, 0.25
mm film thickness). The 1Hꢀ and 13CꢀNMR spectra were
recorded on a Varian Mercury spectrometer at 300 MHz and 75
MHz, respectively.
-
aReaction conditions: palmitic acid (100 mg); ethanol (10 mL) was
b
performed at 80 °C and time (4 h). Active phase (CX4SO3H or CX6SO3H).
cAnalysed by GCꢀMS and 1H NMR.
Once the optimal conditions for the formation of carboxylic esters
using 1a as the catalyst were determined, the scope of this protocol
was further investigated (Table 3). According to the data in Table 1,
good to high yields were obtained in the esterification reactions of
carboxylic acids in the presence of catalyst 1a. The carboxylic acids
(Table 3) were converted to esters in yields ranging from 55ꢀ88%
using catalyst 1a.
General procedure for the synthesis of calix[
n]arenes.
CX4SO3H and CX6SO3H were synthesized in our laboratory
according to previously published procedures. First,
butylcalix[4]arene and
using the Gutsche and Iqba method.11a Second,
butylcalix[4]arene or
p
ꢀ
ꢀ
tert
ꢀ
ꢀ
p
ꢀ
tertꢀbutylcalix[6]arene were prepared
p
tert
p
ꢀ
tertꢀbutylcalix[6]arene were dealkylated
by treatment with aluminium chloride in the presence of
toluene and phenol according to the method described by
Ungaro and coꢀworkers.11b The preparation of CX4SO3H and
CX6SO3H was carried out by treatment of calix[4]arene and
calix[6]arene with concentrated sulfuric acid (98% wt) (Shinkai
et al.).11c
Table 3 Esters yields obtained in esterification reactions catalysed by 1a.a
General procedure for the synthesis of 1a and 1b. 1a and 1b
were synthesized using a solꢀgel technique. A mixture of
CX4SO3H (0.600 g) or CX6SO3H (0.500 g), water (4.5 mL or
3.7 mL, respectively) and 1 mol Lꢀ1 hydrochloric acid (0.5 mL
or 0.4 mL, respectively) was added to tetraethyl orthosilicate
(12.50 mL or 10.40 mL, respectively). The mixture was stirred
for 5 h at room temperature. Then, the mixture was allowed to
stand for 3 days, and after breaking the formed hydrogel with a
Teflon stick, the sample was dried under vacuum for one week
at room temperature. The powder was washed with distilled
water (3 x 10 mL) and dried under vacuum.
Yield (%)b
Entry
Carboxylic acid
1
2
3
4
5
6
7
88
83
86
81
76
55
59
palmitic acid
acetic acid
butyric acid
caprylic acid
oleic acid
stearic acid
myristic acid
aReaction conditions: carboxylic acid (0.40 mmols); ethanol (10 mL) and 1a
b
(2 mol%) was performed at 80 °C and time (4 h). Analysed by GCꢀMS and
1H NMR.
Acidity in aqueous media
The acid capacity was determined by titration with 5 x 10ꢀ3
M
NaOH (aq).12 In a typical experiment, 30 mg of solid 1a was
added to 10 mL of deionized water. The resulting suspension
was allowed to equilibrate and the titrated by dropwise addition
of a 5 x 10ꢀ3 M NaOH solution using phenolphthalein (0.2 %)
as the pH indicator.
We also investigated the reuse of 1a in these reactions. After
completing the reaction, the catalyst was easily separated by
filtration, washed with dichloromethane and subsequently oven
dried at 80 °C for 2 h prior to use in a subsequent reaction
process. Once dried, the residue was used in successive
reactions, and the yields were monitored. 1a was successfully
used in five successive reactions without significant loss of
catalytic activity (Fig. 4).
Acidity in non-aqueous media
The catalyst acidity of 1a (50 mg, catalyst 15 %) was
determined by potentiometric titration of
a suspension
consisting of the solid catalyst in acetonitrile using a solution
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 3

RSC Advances
Page 4 of 6
VJieowuArrtnicalelONnlainme e
ARTICLE
DOI: 10.1039/C6RA02908F
containing
n
ꢀbutylamine in acetonitrile (0.025 N) in a Metrohm
1
J. Otera, Esterification: methods, reactions and applications, Wileyꢀ
VCH Verlag GmbH &Co. KGaA, Weinheim, 1st edn, 2003.
) A. C. Carmo, L. K. C. de Souza, C. E. F. de Costa, E.Longo, J. R.
Zamian and G. N. Rocha Filha, Fuel 2009, 88, 461; ( ) R. S. Thombal, A.
R. Jadhav and V. H. Jadhav, RSC Adv., 2015, , 12981 ( ) A. Orjuela, A.
794 Basic Titrino apparatus with a double junction electrode.13
2
(a
b
X-ray Diffraction
5
c
The crystallographic phase of supported 1a was analysed by ex
situ XRD. The XRD patterns were collected using a Rigaku
DMax 2500PC instrument that was operated at 40 kV and 150
mA with Cu Kα (λ=1.5406 Å) radiation. The data were
collected in a 2θ range from 5° to 50° with a 0.5° divergence
slit and a 0.3 mm receiving slit in fixed time mode with a 0.02°
J. Yanez, A. Santhanakrishnan, C. T. Lira and D. J. Miller, Chem. Eng. J.,
2012, 188, 98.
3
(a
) B. Karimi, H. M. Mirzaei, A. Mobarakia and H. Vali, Catal. Sci.
Technol., 2015, , 3624; ( ) C. Grondal, M. Jeanty and D. Enders, Nat.
Chem., 2010, , 167; ( ) X. Jie, Y. Shang, P. Hu and W. Su, Angew.
Chem., 2013, 125, 3718; ( ) J. B. Liu, L. Nie, H. Yan, L. H. Jiang, J.
Weng and G. Lu, Org. Biomol. Chem., 2013, 11, 8014; ( ) Y. Peng, L.
Luo, C. S. Yan, J. J. Zhang and Y. W. Wang, J. Org. Chem., 2013, 78
10960; ( ) C. K. Y. Lee, A. B. Holmes, S. V. Ley, I. F. McConvey, B. Alꢀ
Duri, G. A. Leeke, R. C. D. Santos and J. P. K. Seville, Chem. Commun.
2005, 2175; ( ) W. R. Reynolds, P. Plucinski and C. G. Frost, Catal. Sci.
Technol., 2014, , 948;( ) P. P. Giovannini, O. Bortolini, A. Cavazzini,
R. Greco, G. Fantin and A. Massi, Green Chem., 2014, 16, 3904; ( ) J.
Lim, S. S. Lee and J. Y. Ying, Chem. Commun., 2010, 46, 806; A; (
5
b
2
c
d
e
step size.
,
General procedure for the synthesis of esters. Carboxilic
acid (0.40 mmol.) and 2 mol% of the catalyst (CX4SO3H or
CX6SO3H, active phase) were combined with ethanol (10 mL)
in a 50 mL roundꢀbottom flask equipped with a stir bar. The
reaction was refluxed (80 °C) for the appropriate amount of
time (4 h). After completion of the reaction, the reaction
mixture was concentrated under vacuum to afford the crude
product, which was analysed by GCꢀMS.
f
,
g
4
h
i
j)
Gömann, J. A. Deverell, K. F. Munting, R. C. Jones, T. Rodemann, A. J.
Canty, J. A. Smith and R. M. Guijt, Tetrahedron, 2009, 65, 1450.
4
(
a
) I. K. Mbaraka and B. H. Shanks, J. Catal., 2005, 229, 365; (
K. Mbaraka and B. H. Shanks, J. Catal., 2006, 244, 78; ( ) L. Sherry and
J. A. Sullivan, Catal. Today, 2011, 175, 471; ( ) P. L. Dhepe, M. Ohashi,
S. Inagaki, M. Ichikawa and A. Fukuoka, Catal. Lett., 2005, 102, 163; (
b) I.
c
Conclusions
d
e
)
In conclusion, the results clearly demonstrate the possibility of
A. Karam, J. C. Alonso, T. I. Gerganova, P. Ferreira, N. Bion, J. Barrault
and F. Jérôme, Chem. Commun., 2009, 7000.
preparing new
pꢀsulfonic acid calix[4]arene heterogeneous
catalyst 1a with a high catalytic activity for the esterification of
carboxylic acids. The corresponding ester products were
obtained in good to high yield (55ꢀ88 %) with excellent
selectivity. Some of the other advantages of catalyst 1a include
easy product separation and purification, nonꢀcorrosive, and
low cost. In addition, the catalyst is considered to be ecoꢀ
friendly because it can be reused five times. The solid catalyst
is highly specific and active, and its stability under liquidꢀphase
reaction conditions indicates the potential for applications in a
continuous flow reactor, which would further decrease the cost
of ester production.
5
(a) P. A. S. Abranches, E. V. V. Varejão, C. M. da Silva, A. de
Fátima, T. F. F. Magalhães, D. L. da Silva, M. A. de ResendeꢀStoianoff,
S. Reis, C. S. Nascimento Jr, W. B. de Almeida, I. M. Figueiredo and S.
A. Fernandes, RSC Adv., 2015,
and S. A. Fernandes, Curr. Pharm. Des., 2013, 19, 6507; (
5
, 44317; (
b
) E. V. Varejão, A. de Fátima
) L. M.
c
Arantes, E. V. V. Varejão, K. J. PelizzaroꢀRocha, C. M. S. Cereda, E. de
Paula, M. P. Lourenço, H. A. Duarte and S. A. Fernandes, Chem. Biol.
Drug Des., 2014; 83, 550; (d) J. V. de Assis, M. G. Teixeira, C. G. P.
Soares, J. F. Lopes, G. S. L. Carvalho, M. C. S. Lourenço, M. V. de
Almeida, W. B. de Almeida and S. A. Fernandes, Eur. J. Pharm. Sci.,
2012, 47, 539; (e) D. L. da Silva, E. C. Tavares, L. S. Conegero, A. de
Fátima, R. A. Pilli and S. A. Fernandes, J. Incl. Phenom. Macrocycl.
Chem., 2011, 69, 149.
Acknowledgements
6
(
a
) X. Yao, X. Wang, T. Jiang, X. Ma, and H. Tian, Langmuir, 2015,
31, 13647; ( ) F. Rodler, B. Schade, C. M. Jaeger, S. Backes, F. Hampel,
C. Boettcher, T. Clark and A. Hirsch, J. Am. Chem. Soc., 2015, 137
The authors acknowledge the financial support from the
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
(CAPES), Fundação de Amparo à Pesquisa do Estado de Minas
b
,
3308; (
c) K. Kobayashi and M. Yamanaka, Chem. Soc. Rev., 2015, 44,
Gerais
(FAPEMIG),
and
Conselho
Nacional
de
449.
Desenvolvimento Científico e Tecnológico (CNPq). S.A.F. was
supported by CNPq research fellowships.
7
(
a
) J. Matthias, R. Yuliya, M. Olena, M. Thorsten, M. Ingo; D.
Gregor, M. Piotr E., G. Juergen, B. Volker and J. Andreas, Nat.
Nanotechnol., 2009, 4, 225; ( ) M. Zhang, X. Yan, F. Huang, Z. Niu and
H. W. Gibson Acc. Chem. Res., 2014, 47, 1995.
) R. De Zorzi, N. Guidolin, L. Randaccio, R. Purrello and S.
Geremia J. Am. Chem. Soc., 2009, 131, 2487; ( ) G. Brancatelli, R. De
b
Notes and references
8
(a
b
aGrupo de Química Supramolecular e Biomimética (GQSB),
Departamento de Química, CCE, Universidade Federal de
Viçosa, Viçosa, MG, Brazil, 36570ꢀ900.
Zorzi, N. Hickey, P. Siega, G. Zingone, and S. Geremia, Cryst. Growth
Des., 2012, 12, 5111.
9
Curr. Org. Chem., 2012, 16, 949; ( ) D. L. da Silva, B. S. Terra, M. R.
Lage, A. L. T. G. Ruiz, C. C. da Silva, J. E. de Carvalho, J. W. M.
Carneiro, F. T. Martins, S. A. Fernades and A. de Fátima Org. Biomol.
Chem., 2015, 13, 3280; (
C. A. Barbosa and S. A. Fernandes RSC Adv., 2014,
Simões, A. de Fátima, A. A. Sabino, F. J. T. de Aquino, D. L. da Silva, L.
(a
) J. B. Simões, D. L. da Silva, A. de Fátima and S. A. Fernandes
bCentro de Investigación y Desarrollo en Ciencias Aplicadas
b
‘‘Dr.
Jorge
J.
Ronco’’
(CINDECAꢀCCTꢀCONICET),
Universidad Nacional de La Plata, Calle 47 No 257, B1900AJK
La Plata, Argentina.
c
) J. B. Simões, A. de Fátima, A. A. Sabino, L.
, 18612; ( ) J. B.
*
Corresponding
author:
santonio@ufv.br
or
4
d
sefernandes@gmail.com; Fax: +55 31 3899 3065, Tel: +55 31
3899 3071.
C. A. Barbosa and S. A. Fernandes Org. Biomol. Chem., 2013, 11, 5069;
(
e
) D. L. da Silva, S. A. Fernandes, A. A. Sabino and A. de Fátima,
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/b000000x/
Tetrahedron Lett., 2011, 52, 6328; ( ) A. G. Sathicq, N. A. Liberto, S. A.
Fernandes and G. P. Romanelli, C. R. Chimie, 2015, 18, 374; (
Homden and C. Redshaw, Chem. Rev. 2008, 108, 5086.
10 (
f
g) D. M.
a
) R. Natalino, E. V. V. Varejão, M. J. da Silva, A. L. Cardoso and
, 1369; ( ) S. A. Fernandes,
S. A. Fernandes, Catal. Sci. Technol., 2014,
4
b
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 2012

Page 5 of 6
Journal Name
RSC Advances
View Article Online
ARTICLE
DOI: 10.1039/C6RA02908F
R. Natalino, M. J. da Silva and C. F. Lima, Catal. Commun., 2012, 26
127; (
N. Jham, Tetrahedron Lett., 2012, 53, 1630.
11 ( ) C. D. Gutsche and M. Iqbal, Org. Synth., 1990, 68, 234; (
,
c
) S. A. Fernandes, R. Natalino, P. A. R. Gazolla, M. J. da Silva, G.
a
b
) C. D.
Gutsche and L. G. Lin, Tetrahedron, 1986, 42, 1633; S. Shinkai, S. Mori,
T. Tsubaki, T. Sone and O. Manabe, Tetrahedron Lett., 1984, 25, 5315.
12 J. J. Martínez, E. Nope, H. Rojas, M. H. Brijaldo, F. Passos, G.
Romanelli, J. Mol. Catal. A: Chem. 2014, 392, 235.
13 S. G. Casuscelli, M. E. Crivello, C. F. Perez, G. Ghione, E. R.
Herrero, L. R. Pizzio, P. G. Vázquez, C. V. Cáceres, M. N. Blanco, Appl.
Catal. A: Gen. 2004, 274, 115.
This journal is © The Royal Society of Chemistry 2012
J. Name., 2012, 00, 1-3 | 5

RSC Advances
Page 6 of 6
View Article Online
DOI: 10.1039/C6RA02908F
p-Sulfonic acid calix[4]arene-functionalized alkyl-bridged organosilica
in esterification reactions
J. V. de Assis, P. A. S. Abranches, I. B. Braga, O. M. P. Zuñiga, A. G. Sathicq, G. P.
Romanelli, A. G. Sato and S. A. Fernandes