3D-network porous polymer based on calix[4]resorcinarenes as an efficient phase transfer catalyst in regioselective conversion of epoxides to azidohydrins

Article abstract of DOI:10.1016/j.catcom.2012.09.006

The present study, for the first time, describes the application of 3D-network polymer based on calix[4]resorcinarene, as an efficient heterogeneous and phase transfer catalyst for regioselective azidolysis of epoxides. The surface morphology and the stru

Full text of DOI:10.1016/j.catcom.2012.09.006

Catalysis Communications 29 (2012) 1–5
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
3D-network porous polymer based on calix[4]resorcinarenes as an efficient phase
transfer catalyst in regioselective conversion of epoxides to azidohydrins
⁎
Arash Mouradzadegun , Ali Reza Kiasat, Pegah Kazemian Fard
Chemistry Department, Faculty of Science, Shahid Chamran University, Ahvaz 61357-4-3169, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 July 2012
Received in revised form 30 August 2012
Accepted 4 September 2012
Available online 11 September 2012
The present study, for the first time, describes the application of 3D‐network polymer based on calix[4]
resorcinarene, as an efficient heterogeneous and phase transfer catalyst for regioselective azidolysis of epox-
ides. The surface morphology and the structure of this polymer were investigated by atomic force microscopy
(AFM). This method offers several advantages including clean reactions, ease of work-up and reusability of
the catalyst.
© 2012 Elsevier B.V. All rights reserved.
Keywords:
Calix[4]resorcinarenes
Network polymer
Azidohydrins
AFM
1. Introduction
regioselective azidolysis of epoxides to produce azido alcohols is
reported. These products are an important class of organic compounds
There has been an intense interest in the synthesis and design of su-
pramolecular structures due to their great applications such as catalyst,
promoter and nanovessel to direct reactivity, regioselectivity and
chemoselectivity of organic reactions [1–5]. In this respect, the proper-
ties of various macrocyclic molecules have been extensively studied in
the past decade. Special attention has been focused on calix[4]
resorcinarenes because of both facile preparation and derivatization.
Up to now, many applications of calix[4]resorcinarenes have been suc-
cessfully achieved in photo resist materials, optical chemosensors, med-
icine and biomimetic, as well as in the development of chemical sensors
and biosensors [6–9]. The modification of these structures can be
achieved either via substitutions on the aromatic ring, the phenol hy-
droxyl groups or the lower rim to increase their potential for forming
multifunctional compounds. Recently, resorcinarenes were immobilized
in the phase of three dimensional network polymers to realize their
unique properties in which obtained by porosity containing both hydro-
philic and hydrophobic layers in their structure [10,11]. Such unique
characteristics are generally unavailable in other porous materials. This
new generation of nonporous organic polymer presents interesting
and specific applications and some reports have appeared recently in
this area [12–16]. However, to the best of our knowledge, there is no re-
port on the use of these 3D‐polymers as heterogeneous and phase trans-
fer catalyst in synthetic reactions. In the present study, according to the
mentioned approach and in continuation of our previous studies [17,18],
the use of network porous polymer based on calix[4]resorcinaren in the
which are applied as precursors in the syntheses of vicinal amino alco-
hols, carbohydrates, nucleosides, lactames and oxazolines [18]. There-
fore, these high value transformations lead to the recent emphasis on
the development of reliable methods for their preparation. Hence, it
seems that there is an increasing demand for introducing the environ-
mentally benign and attractive alternatives besides offering economical
advantages to current synthetic protocols.
2. Experiment
2.1. General
Resorcinol was purchased from Merck. Required Epoxides and other
chemicals were purchased from Fluka and Merck in high purity. All of the
azidohydrines compounds were prepared by our procedure, and their
spectroscopic and physical data were compared with those of authentic
samples. IR spectra were recorded on a Shimadzo 450 spectrophotome-
ter. NMR spectra were recorded in CDCl3 on a Bruker Advanced DPX
400 MHz spectrophotometer using TMS as internal standard. The purity
determination of the products and the reaction monitoring were accom-
plished by TLC on silica gel polygram SILG/UV 254 plates.
2.2. General procedure for the synthesis of network polymer
Compound Ι (see Ι in Scheme 1) was obtained by the condensation
of resorcinol with acetaldehyde [19]. Briefly, for synthesis of network
polymer, compound Ι (10 mmol) was dissolved in an aqueous
⁎
Corresponding author. Tel./fax: +98 611 3331746.
E-mail address: arash_m@scu.ac.ir (A. Mouradzadegun).
1566-7367/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2012.09.006

2
A. Mouradzadegun et al. / Catalysis Communications 29 (2012) 1–5
Scheme 1. Synthesis of 3D‐network polymer based on calix[4]resorcinarene.
solution containing NaOH (40 mmol), finally, formaldehyde (40 mmol)
was added [10].
polymer was filtered off and the filtrate was extracted with ether. The
extract was washed with water, dried (CaCl2) and evaporated in vacu-
um to give azidohydrines in 83–89% isolated yields. For styrene oxide,
further purification was achieved by preparative TLC or by silica gel col-
umn chromatography.
2.3. Reactions of epoxides with NaN3 catalyzed by network polymer
Network polymer (0.1 g) was added to a mixture of the epoxide
(1.0 mmol) and NaN3 (3 mmol) in water (5 cm3). The reaction mixture
was magnetically stirred at 80 °C as much as the time shown in Table 2.
After complete consumption of starting material as judged by TLC
(using n-hexane:ethyl acetate (5:1) as eluent), the insoluble network
3. Results and discussion
Firstly, the target polymeric catalyst was prepared based on
tetramethylcalix[4]resorcinarene under the assumption that the special
Fig. 1. (a) AFM images (1 μ×1 μ) of network polymer and (b) AFM surface plot of network polymer.

A. Mouradzadegun et al. / Catalysis Communications 29 (2012) 1–5
3
Fig. 2. Section analyses of network polymer.
porosity (both hydrophilic and hydrophobic) could provide efficient
catalytic role for the regioselective synthesis of azidohydrines.
Calix[4]resorcinarenes Ι was prepared according to literature pro-
cedures, starting from resorcinol and acetaldehyde [19]. Subsequent-
ly, the considered polymer which is depicted in part ΙΙ in Scheme 1
was produced by resol polycondensation of Ι with formaldehyde
according to Scheme 1. Note that the 3D-structure of the polymer is
disregarded in Scheme 1.
The obtained FT-IR absorption spectra of the polymer are in agree-
ment with previous reports [10]. In order to gain insight into the sur-
face pores, atomic force microscopy (AFM) was utilized. All of the
AFM scans were taken in ambient air in tapping mode, which is
ideal for this kind of polymers [20]. Phase data were utilized to sup-
plement the height data because they provide clearer and higher con-
trast image of structural features. Representative 1 μ×1 μ AFM height
and phase image suggest a series of pores which have average surface
diameter of 300 nm (Fig. 1a). Note that more details could be
obtained from 3D height plot (Fig. 1b) and the analysis of height
along a linear path (Fig. 2).
size of pores network polymer is in agreement with the AFM data. It
was implied that the network polymer has ability for playing a role
of catalyst for the inclusion of an organic guest in surface pores.
The XRD patterns of the prepared network polymer and methylcalix
[4]resorcinarene are depicted in Fig. 4(a,b). It seems that to the intense
and sharp diffraction peaks of C-methylcalix [4]resorcinarene, it
exhibited a high degree of crystallinity and this may be attributed to
the hydrogen bonding between the resorcinarene units (Fig. 4a). As it
can be seen in this figure, most of the peaks in the XRD patterns of the
methylcalix[4]resorcinarene samples can be completely indexed with
Resorcinol in the standard card (JCPDS No. 00-038-1969). It can be ob-
served that when the methylcalix[4]resorcinarene is incorporated into
a polymer system crystalline peaks are still exhibited but the intensity
In the latter case, peak-to-valley measurements showed a very
good performance of surface morphology. On the whole, AFM re-
vealed that the 3D-network polymer ΙΙ exhibited a porous surface
that has the ability for the inclusion of an organic guest.
In this study, scanning electron microscope (SEM Seron AIS-2100)
was used to observe the morphology porosity of the polymer scaffold.
The image of the network polymer are presented in Fig. 3. In this
image, one can observe that more porous structure with meshwork
was obtained for network polymer. SEM confirmed that the average
Fig. 3. SEM image of porous network polymer.
Fig. 4. XRD pattern of a) calix[4]resorcinarene and b) network polymer.

4
A. Mouradzadegun et al. / Catalysis Communications 29 (2012) 1–5
Table 1
Reaction of various epoxides with sodium azide in the presence of the representative catalyst in water.a
b
Entry
1
Substrate
Product(s)
Time (h)
1.5
Yield %
89
2
1.5
85 (96:4)c
3
4
1.5
85
87
2.10
5
6
7
2.20
1.45
1.20
1.40
85
87
83
84
8
a
Products were identified by compares of their physical and spectral data with those of authentic samples.
Isolated yields.
According to GC analysis.
b
c
of the peaks decreases and a broad spectrum appears. In other words,
crystalline nature but broad spectrum shows that its composition con-
sists predominantly of an amorphous phase.
Following the above discussion, the synthetic utility of this network
polymer was explored by examining the reaction of epoxides to sodium
azide for preparation of azidohydrines in water. Examination of the
the amorphous nature of the polymer increases and almost the fine‐
disrupts crystals of the methylcalix[4]resorcinarene were existed
(Fig. 4b). Some distinct peaks were observed for the network polymer
which indicated that the network polymer molecules have the semi

A. Mouradzadegun et al. / Catalysis Communications 29 (2012) 1–5
5
Table 2
Comparison of azidolysis of styrene oxide with different catalysts.
4. Conclusion
In conclusion, the network polymer was introduced to be a highly
efficient polymeric phase transfer catalyst for regioselective ring
opening of epoxides to azidohydrins by azide anion. It played a spe-
cial role as a heterogeneous and phase transfer catalyst for such reac-
tions. Further studies are currently underway to investigate these
predictions.
Moreover, the reaction offers several advantages including mild
reaction conditions, high conversions, greater regioselectivity, clean
reaction profiles, and high isolated yields which make it a useful
and attractive process for the synthesis of azidohydrines.
.No
Catalyst/reagent
Reaction time (h)
Yield %
Ref
a
1
2
3
4
5
6
7
Network Polymer
LiClO4/NaN3
SiO2-OPEG (300)
NaN3/CeCl3
TMSN3/β-Cyclodex
Zr(OTf)2/TMGAb
Polymeric PTCc/Na
1.5
5
1
3
5
85 (96:4)
92 (82/18)
80 (95/5)
89 (89/11)
45
[21]
[18]
[22]
[23]
[24]
[25]
42
6
67 (74/26)
95 (91/9)
a
Present method.
b
c
TMGA: 1,1,3,3-tetramethylguanidinium azide.
Polymeric PTC: poly[N-(2-aminoethyl)acrylamido]-trimethyl ammonium iodide.
catalytic activity of network polymer indicated that the use of 3 equiv of
NaN3 in the presence network polymer (0.1 g) in water at 80 °C is the
best condition for the conversion of epoxides to the azidohydrins
(Table 1).
Acknowledgments
We are grateful to the Research Council of Shahid Chamran Uni-
versity for the financial support.
To ascertain the scope and limitation of the present reaction, dif-
ferent types of oxiranes carrying activated and deactivated groups
were cleanly, easily, and efficiently converted to the corresponding
azidohydrines (Table 1). The structure of all the products were settled
from their analytical and spectral (IR, NMR) data and by direct com-
parison with authentic samples.
Appendix A. Supplementary data
Supplementary data to this article can be found online at http://
dx.doi.org/10.1016/j.catcom.2012.09.006.
Except for the reaction of styrene oxide (Table 1, Entry 2), which
produces 2-azido-2 phenylalcohol (III) as major product and trace
amount of other regioisomer 2-azido-1-phenylalcohol (IV), the reac-
tion of other epoxides was found to be highly regioselective and only
azidohydrin (IV) was obtained. Also in the case of cyclic epoxide,
trans product was obtained. The promoting effect of polymer catalyst
was definitely confirmed by the reaction of styrene oxide to sodium
azide under similar reaction conditions, without adding catalyst or
in the presence of the initial Resorcinaren TLC analysis of the reaction
mixture did not show completion of the reaction after 8 h. It was
noted that 3D-network polymer did not suffer from extensive me-
chanical degradation and can be easy filtered, washed with water
and methanol and dried for 2 h at 80 °C under vacuum. It could be
reused for three times again.
References
[1] L. Barr, S.F. Lincoln, C.J. Easton, Supramolecular Chemistry 17 (2005) 547.
[2] Y. Nishioka, T. Yamaguchi, M. Yoshizawa, M. Fujita, Journal of the American
Chemical Society 129 (2007) 7000.
[3] T.S. Koblenz, J. Wassenaar, J.N.H. Reek, Chemical Society Reviews 37 (2008) 247.
[4] M. Roger, Y. Dalcanale, E. Dalcanale, Journal of the American Chemical Society 131
(2009) 2452.
[5] D.M. Vriezema, M.C. Aragons, J.A.W. Elemans, J.L.M. Cornelissen, A.E. Rowan,
R.J.M. Nolte, Chemical Reviews 105 (2005) 1445.
[6] T. Nakayama, D. Takhashi, K. Takeshi, Journal of Photopolymer Science and Tech-
nology 12 (1999) 347.
[7] O.H. Aba, K. Haga, M. Ueda, O. Morikawa, H. Konishi, Chemistry of Materials 11
(1999) 427.
[8] T.W. Bell, N.M. Hext, Chemical Society Reviews 33 (2004) 589.
[9] V.K. Jain, S.G. Pillai, H.S. Gupte, Journal of the Iranian Chemical Society 5 (2008)
646.
Obviously, in these reactions and in the present polymer, styrene
oxide underwent cleavage with sodium azide with preferential attack
at the benzylic position to give the corresponding azidohydrines,
while 2-alkyl epoxides gave the products just formed by cleavage at
the terminal position. These observations demonstrated that in the
former case, the product was generated through the formation of a
stabilized benzylic cation during the reaction and in the second
case; they were formed by predominant attack of the azide ion on
the less hindered carbon of the epoxide. It is presumable that,
owing to the hydrophobic external porous of 3D-polymer, the inclu-
sion complex formed with the epoxide in the porous and via hydro-
gen bonding of the epoxide oxygen to the outer OH of the network
polymer then bare azide anion transfer and react with immobilized
epoxide. Therefore, the high selectivity and shorter reaction time
which were not possible with the earlier methods could be explained
by this inclusion complex formation of epoxide with 3D-network.
The advantage of using polymer as a catalyst for the synthesis of
azidohydrins using sodium azide is shown by comparing our results
with those previously reported in the literature (Table 2).
[10] H. Altshuler, E. Ostapova, O. Fedyaeva, L. Sapozhnikova, O. Altshuler, Macromo-
lecular Symposia 181 (2002) 1.
[11] G.N. Al'tshuler, E.V. Ostapova, Russian Journal of Physical Chemistry 83 (2009)
1032.
[12] H. Altshuler, L. Sapozhnikova, E. Ostapova, Solvent Extraction and Ion Exchange
20 (2002) 263.
[13] G.N. Al'tshuler, L.A. Sapozhnikova, N. Malyshenko, G. Shkurenko, E. Ostopova, B.
Tryasunov, H. Al'tshuler, International Journal of Hydrogen Energy 36 (2011)
1259.
[14] O.G. Al'tshuler, L.P. Abramova, L.A. Sapozhnikova, G.N. Al'Tshuler, Russian Journal
of Applied Chemistry 82 (2009) 391.
[15] O.H. Altshuler, N.V. Malyshenko, G.J. Shkurenko, H.N. Altshuler, Theoretical Foun-
dations of Chemical Engineering 43 (2009) 43.
[16] G.N. Al'tshuler, N.V. Malyshenko, G.Y. Shkurenko, O.G. Al'tshuler, Russian Journal
of Physical Chemistry A 82 (2008) 2202.
[17] A.R. Kiasat, M.F. Mehrjardi, Journal of the Iranian Chemical Society 6 (2009) 542.
[18] A.R. Kiasat, M. Zayadi, Catalysis Communications 9 (2008) 2063.
[19] M. Linda, J.A. Tunstad, T. Dalcanale, E. Dalcanale, A. Bryant, C. Sherman, R.C.
Helgeson, C.B. Knobler, D.J. Cram, Journal of Organic Chemistry 54 (1989) 1305.
[20] S. Magonov, D. Reneker, Review of Materials Science 27 (1997) 175.
[21] M. Chini, P. Crotti, F. Macchia, Tetrahedron Letters 31 (1990) 5641.
[22] G. Sabitha, R.S. Babu, M. Rajkumar, J.S. Yadav, Organic Letters 4 (2002) 343.
[23] A. Kamal, M. Arifuddin, M.V. Rao, Tetrahedron-Asymmetry 10 (1999) 4261.
[24] P. Crotti, V.D. Bussolo, L. Favero, F. Macchia, M. Pineschi, Tetrahedron Letters 37
(1996) 1675.
The consideration of remarkable stabilities of porous polymer led
us to investigate in this way that a catalyst was easily recovered and
could be reused several times without loss of activity.
[25] B. Tamami, H. Mahdavi, Tetrahedron Letters 42 (2001) 8721.