Microcrystalline Zinc Coordination Polymers as Single-site Heterogeneous Catalysts for the Selective Synthesis of Mono-oxazolines from Amino Alcohol and Dinitriles

Article abstract of DOI:10.1002/asia.201600434

In our effort to develop coordination polymers (CPs)-based single-site catalysts for the selective synthesis of mono-oxazolines, two Zn-based CPs, [{Zn₆(idbt)₄(phen)₄} ?3 H₂O]_n (1) and [{Zn₃

Full text of DOI:10.1002/asia.201600434

DOI: 10.1002/asia.201600434
Full Paper
Coordination Polymers
Microcrystalline Zinc Coordination Polymers as Single-site
Heterogeneous Catalysts for the Selective Synthesis of Mono-
oxazolines from Amino Alcohol and Dinitriles
Junning Wang+, Chao Huang+, Kuan Gao, Xiaolu Wang, Mengjia Liu, Haoran Ma, Jie Wu,*
and Hongwei Hou*[a]
Abstract: In our effort to develop coordination polymers
(CPs)-based single-site catalysts for the selective synthesis of
mono-oxazolines, two Zn-based CPs, [{Zn6(idbt)4(phen)4}
·3H2O]n (1) and [{Zn3(idbt)2(H2O)4}·2H2O]n (2) (H3idbt=
surfactant-mediated hydrothermal methods, and an investi-
gation is conducted to explore how different surfactants
affect their morphologies and particle sizes. Furthermore,
micro 1 and 2 have shown to be effective heterogeneous
catalysts for the reaction of amino alcohols and aromatic di-
nitriles, and exerted a significant influence on the selectivity
of the catalytic reactions, yielding mono-oxazolines as the
major reaction product.
5,5’-(1H-imidazole-4,5-diyl)-bis-(2H-tetrazole),
phen=1,10-
phenanthroline) have been synthesized. They exhibit two-di-
mensional structure and contain isolated and accessible cat-
alytically active sites, mimicking the site isolation of many
catalytic enzymes. Micro CPs 1 and 2 are obtained by using
Introduction
hibit particle dimensions in the tens to hundreds of microme-
ters range, endowing them higher catalytic efficiency.
Coordination polymers (CPs), including metal–organic frame-
works (MOFs), have recently emerged as promising new mate-
rials for gas storage,[1–3] sensing,[4,5] drug delivery,[6] light har-
vesting,[7,8] heterogeneous catalysis.[9] In particular, CPs have
been established as a highly tunable platform for developing
immobilized well-defined molecular catalysts, leading to a new
generation of solid catalysts with uniform catalytic sites for var-
ious reactions, such as aldol condensation,[10,11] CÀC bond for-
mations,[12,13] epoxidations,[14–16] oxidations,[17,18] cyclization,[19,20]
fixed-bed reactions,[21] and so forth. In comparison with other
immobilized systems, CPs have highly ordered crystalline struc-
tures, high catalyst loadings, more uniform and isolated cata-
lytic sites, thus eliminating multimolecular catalyst deactivation
pathways.[13] In addition, by scaling down the sizes of CPs into
microregime, the formed microscale CPs as heterogeneous cat-
alysts can usually exhibit unique and enhanced catalytic prop-
erties because they not only maintain the structural diversity
and physicochemical properties as bulk phase CPs but also ex-
On the other hand, oxazoline derivatives exhibit various
pharmaceutical activities, such as antidiabetic,[22] antihyperten-
sive,[23] antidepressant,[24] anticancer,[25] and so forth. The
tandem condensation–cyclodehydration reaction of amino al-
cohol and nitriles toward the synthesis of oxazoline derivatives
is one of the most efficient methods.[26–28] However, the reac-
tion of amino alcohols and dinitriles to selectively prepare
mono-oxazolines is still a considerable challenge, because it
usually affords a mixture of bis- and mono-oxazolines as co-
products in the reported catalytic systems.[28–33] As a research
program of our laboratory, we are interested in developing an
approach to obtain mono-oxazolines by the reactions of
amino alcohols and dinitriles, as there are possibilities to fur-
ther elaborate the remaining nitrile function, such as tetrazole,
carboxylic acid, and carboxylic acid derivatives. Encouraged by
the merits of CPs-based heterogeneous single-site catalysts,
we attempt to explore whether the CPs could selectively cata-
lyze such reactions.
In this work, with a rigid and conjugated clamp-like ligand
(H3idbt),
two
zinc-based
coordination
polymers
[a] J. Wang,+ C. Huang,+ K. Gao, X. Wang, M. Liu, H. Ma, Prof. J. Wu,
Prof. H. Hou
[{Zn6(idbt)4(phen)4}·3H2O]n (1) and [{Zn3(idbt)2(H2O)4}·2H2O]n (2)
have been synthesized. Furthermore, microscale CPs 1 and 2
were introduced with the addition of polyvinylpyrrolidone
(PVP-1300000), hexadecyltrimethylammonium bromide (CTAB),
and sodium dodecyl sulfate (SDS) as surfactants for high dis-
persion of the catalyst in solution and more effective utilization
of zinc catalytic sites. With the addition of micro CPs 1 (or 2)
as heterogeneous catalysts, mono-oxazolines as the major
product were achieved by reacting amino alcohols with dini-
College of Chemistry and Molecular Engineering
Zhengzhou University, Zhengzhou (China)
Fax: (+86)371-67761744
E-mail: wujie@zzu.edu.cn
houhongw@zzu.edu.cn
[+] These authors contributed equally to the work.
Supporting information and the ORCID identification number(s) for the au-
thor(s) of this article can be found under http://dx.doi.org/10.1002/
asia.201600434.
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triles, due to their distinct isolated and accessible catalytically
active sites. A mechanism for the catalytic reaction has been
proposed. The influence of surfactants on the morphologies
and particle sizes of CPs has been investigated.
Results and Discussion
Structure of [{Zn6(idbt)4(phen)4}·3H2O]n (1)
Single-crystal X-ray crystallography revealed that 1 crystallizes
in the monoclinic space group and shows a 2D gridding-like
structure containing an octanuclear ZnII secondary building
unit (SBU). Four imidazole groups of ligand H3idbt bridge two
Zn1 and two Zn3 to form a square-like tetranuclear ZnII macro-
cycle as inwall of the SBU by the repeat of -[-Zn1-imidazole-
Zn3-]- linkage, whereas two tetrazole groups of the ligand che-
late Zn2 on four sides of the square to form another tetranu-
clear block (Figure 1a). Zn2 ion adopts a tetrahedral geometry
and can be used as an isolated and accessible active site due
to its azimuth, configuration, and unsaturated metal center,
whereas Zn1 and Zn3 can be regarded as catalytically inactive
(Figure S1 in the SI). Eight symmetry-related ZnII atoms are
linked by four idbt3À groups to construct a [Zn8(idbt)3] SBU,
which is bridged together by Zn atoms to form a 2D infinite
gridding-like structure (Figure 1b).
Figure 2. (a) The coordination environment of the ZnII ions in 2 (Hydrogen
atoms and free water molecule are omitted for clarity), atoms labelled
white=carbon; black=zinc; gray(80%)=oxygen; gray(25%)= nitrogen;
(b) the 2D layer structure viewed along the a-axis direction.
Structure of [{Zn3(idbt)2(H2O)4}·2H2O]n (2)
Complex 2 exhibits a 2D ladder-like structure, which crystallizes
in the monoclinic system, space group P21/c. As shown in Fig-
ure 2a, the asymmetric unit of 2 consists three crystallographi-
cally independent ZnII ions, two idbt3À ligands, four coordinat-
ed water molecules, and two lattice water molecules, as con-
firmed by the charge balance and TGA (Figure S2 in the SI).
The Zn1 ion is surrounded by three nitrogen atoms from two
idbt3À ligands and one oxygen atom from one water molecule
to furnish a distorted tetrahedral geometry. Zn2 ion possesses
the typical five-coordinated trigonal bipyramid coordination
geometry. Zn1 and Zn2 are bridged by idbt3À ligands to form
a 2D layer containing grids running along the a-axis formed by
four Zn as vertexes and four idbt3À ligands as edges (Fig-
ure 2b). Zn3 stretches out from the layer and adopts distorted
trigonal bipyramid geometry by coordinating with two nitro-
gen atoms from one idbt3À ligands as well as three oxygen
atoms from three coordinated water molecules. The coordinat-
ed water molecules are good leaving groups, they may depart
during the catalytic process, leaving unsaturated zinc sites to
be exposed to dinitriles, which is beneficial for the catalytic
processes.
Dependence of surfactants on crystallite size and morpholo-
gy
CPs have many advantages to be a kind of heterogeneous cat-
alyst because of their large surface areas, isolated accessible
active sites, and flexible and diverse structures. For a heteroge-
neous catalyst, deliberately scaling down the size of the cata-
lyst and accessing a nanosized or microsized catalyst is an effi-
Figure 1. (a) View of the octanuclear in 1 (hydrogen atoms, free water mole-
cule, and phen are omitted for clarity); atoms labelled white=carbon;
black=zinc; gray(25%)=nitrogen. (b) View of 2D layer structure of 1 along
the a-axis (Zn atoms are shown in polyhedron).
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cient strategy to formulate materials with a high density of cat-
alytically active sites.[34–37] Herein, several surfactants, such as
PVP-1300000, CTAB, and SDS, were introduced individually
into the hydrothermal reaction to construct catalysts with re-
duced size.
Without surfactants, cuboid crystals of 1 with dimensions of
ꢀ0.3”0.1”0.1 mm3 were produced (Figure S3 in the SI). When
PVP-1300000 as a surfactant was added, the particle size of
crystalline 1 was reduced drastically with narrow diameter dis-
tributions of nearly 8 mm in length and 500 nm in width (Fig-
ure 3a). When CTAB was employed, the particle size could also
be scaled down to the micrometer regime, and the average
edge width of the resulting crystals is about 700 nm (Fig-
ure 3b). In addition, crystals with an average edge width of
600 nm are obtained with SDS, as shown in Figure 3c. Further-
more, with the addition of a surfactant (PVP, CTAB, or SDS) as
Figure 4. (a) Compared with different surfactants (PVP, CTAB, and SDS), ex-
perimental, and simulated PXRD patterns of complex 1; (b) compared with
different surfactants (PVP, CTAB, and SDS), experimental, and simulated
PXRD patterns of complex 2.
The concentration of the surfactants is another important
factor, which determines the particle size and morphology of
the product. The experiment was carried out under different
concentrations of PVP-1300000, CTAB, or SDS (0.015, 0.025,
0.05, 0.075, 0.10, 0.125 and 0.15 g). A higher concentration of
the reactant is considered to make ligands more likely to react
with metal ions and the nucleation rate is faster, forming the
smaller particles. Therefore, by increasing the concentration of
the surfactants, the particle size becomes smaller. When the
concentration of the surfactant was 0.15 g, the well-defined
crystalline morphologies and particle sizes distributions of
1 and 2 could be obtained. Higher concentrations led to the
formation of amorphous micro CPs rather than crystalline
micro CPs. In addition, other surfactants, such as polyethylene
glycol-20000, sodium dodecylbenzenesulfonate, and polyethy-
lene oxide, led to the formation of amorphous micro CPs
rather than crystalline micro CPs.
Figure 3. Scanning electron microscopy images of microcrystals: (a) micro-
crystals 1 with addition of PVP; (b) microcrystals 1 with addition of CTAB;
(c) microcrystals 1 with addition of SDS; (d) microcrystals 2 with addition of
PVP; (e) microcrystals 2 with addition of CTAB; (f) microcrystals 2 with addi-
tion of SDS.
template, microscale crystals of 2 could also be obtained
through hydrothermal syntheses (Figure 3d–f). Single crystals
of 2 with edge width of about 0.08 mm were synthesized with-
out surfactants (Figure S3b in the SI). In contrast, with the ad-
dition of a surfactant (PVP, CTAB, or SDS), micro crystals of 2
with an average edge width of 600 nm were obtained.
In addition, powder X-ray diffraction (PXRD) analysis demon-
strated that there is no significant change for the bulk phase
and microscale crystals with the simulated of 1 and 2, which
indicated the microscale crystals are crystalline and have the
same crystal structures as that of 1 and 2 (Figure 4). The surfac-
tants could be served as capping agents to restrict the particle
size, thus keeping the microcrystalline in micrometers along
the width.[38,39]
The catalytic capacity of micro CPs 1 and 2
Oxazolines are ubiquitous in natural products and have been
used for pharmaceutical drug discovery in recent years.[40–43]
However, the design and synthesis of effective catalysts to se-
lectively achieve mono-oxazolines from dinitriles still remains
a challenge. The phase purity of the microcrystalline samples
of 1–2 was determined by an excellent match between the mi-
crocrystalline and simulated PXRD patterns (Figure 4). To study
the potentials of micro CPs of 1–2 as heterogeneous catalysts
in the tandem condensation reaction of amino alcohols and di-
nitriles, their catalytic activities were initially evaluated with l-
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In addition, inductively coupled plasma mass spectrometric
(ICP-MS) analysis of the supernatant showed very little Zn
leaching (ꢀ1 ppm for 1 and ꢀ4 ppm for 2) after the catalytic
reactions. Next, we carried out a hot filtration experiment.
After 18 or 25% conversion of 4a in the presence of 1 or 2 in
1 h, the reaction mixture was passed through a sand core
funnel to remove the catalysts, and the supernatant was al-
lowed to stand for 11 h. It was found that the conversion of
the supernatant remained almost unchanged during the pro-
cess. Thus, these experiments unambiguously confirmed their
heterogeneity.
Table 1. Catalyzed synthesis of mono-oxazolines from 4 with l-amino alco-
hol.[a]
Entry Catalyst
4
Yield[%]
Yield[%]
of 5a–d[b] of 6a–d[b]
1
2
1
2
83
86
Trace
Trace
To probe whether catalysis occurs inside the cavity or on the
surface of the catalysts, a sterically demanding substrate bi-
phenyl-4,4’-dicarbonitrile (4d) was subjected to the catalytic
conditions. Consequently, a conversion of 47% and 60%
(Table 1, entries 7 and 8) with micro CPs 1 and 2 as catalysts,
respectively, was achieved. Because 4d is difficult to diffuse
into small cavities of 1 and 2, the active sites on the surface of
the catalysts are believed to catalyze the reaction.
3
4
1
2
80
84
Trace
Trace
We have also examined the catalytic activities of bulk crys-
tals 1 (ꢀ0.20”0.20”0.15 mm3) or 2 (ꢀ0.25”0.22”0.19 mm3)
for the cyclization reaction of 3 and 4a without grinding and
stirring to eliminate the possibility of catalytic activity resulting
from the surface metal sites of very tiny particles. Less than
40% yield was observed after 12 h, which was much lower
than the 83 and 86% yield obtained with microscale crystalline
1 and 2, respectively. The result indicates that the cyclization
reaction also occurs inside the framework at the same time be-
cause big crystals own too few surface metal sites to account
for the catalytic reaction. Furthermore, the experimental Bruna-
uer-Emmett-Teller (BET) surface area for the micro and bulk
crystals was 194 and 9.2428 m2 gÀ1, which clearly shows that
catalytic activities depend on the surface catalytic sites of parti-
cle sizes (Figure S4 in the SI). Therefore, these results provided
evidence that the catalysis reactions for 4a–c may take place
on the surface and inside of the crystals with single-site cataly-
sis.
5
6
1
2
68
72
Trace
Trace
7
8
1
2
47
60
Trace
Trace
[a] Reaction conditions: l-aminoalcohols (3.0 mmol), aromatic dinitriles
(1.0 mmol), catalyst (0.1 mmol), chlorobenzene (5 mL), 12 h. [b] Isolated
yield of the product after 12 h.
The catalysts for the synthesis of mono-oxazolines could be
evaluated from site-isolation. Due to their well-defined crystal-
line nature, a very valuable feature of CPs is that they can pro-
vide atomistically well-defined isolated active catalytic sites
with uniformly fixed azimuth and distance throughout the
solid, mimicking the site-isolation of many catalytic enzymes
assemblies in nature. These identical isolated active sites can
catalyze the reaction without synergistic interactions, selective-
ly achieving mono-oxazolines from dinitrile compounds. As for
1, Zn2 ions are isolated and have accessible active sites due to
their unsaturated metal center. As for 2, Zn3 ions are catalyti-
cally active sites. We speculate that one of the cyano groups is
activated by the Zn Lewis active sites. Because there are no
synergistic interactions in the active sites of 1 and 2, the reac-
tions lead to mono-oxazolines as the major products. Com-
bined with high site density onto the complexes, the single-
site isolation leads to high conversion. The mechanism for the
synthesis of mono-oxazolines catalyzed by the Zn-based CPs
had been proposed (Scheme 1). The dinitrile is first activated
by the catalyst to give I. Then, l-amino alcohol attacks I to
amino alcohol and dinitriles (4a–4c) as substrates in chloro-
benzene at reflux for 12 h (Table 1).
The results showed that both micro CPs 1 and 2 were effi-
cient heterogeneous catalysts for the reaction of l-amino alco-
hol with dinitriles, giving 5a–5c with moderate to high yields
(68–86%) along with trace of bis-oxazoline products. Amazing-
ly, mono-oxazolines were formed as the major products by
using micro CPs 1 and 2 as the heterogeneous catalysts. In
comparison, homogeneous catalyst ZnCl2, which is a commonly
used Lewis acid catalyst for the cyclization reaction, gave both
the mono-oxazoline and bis-oxazoline cyclization products
under the same reaction conditions (Table S1 in the SI). Only
under a series of harsh conditions, such as long reaction times
and water- and oxygen-free conditions, bis-oxazoline products
could be obtained with yields ranging from 51–61% in 72 h.[28]
When the same equivalent of H3idbt ligand (0.1 mmol) was
added under the same reaction conditions, no products could
be obtained. The catalytically active sites are believed to the
CPs 1 and 2
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Experimental Section
Materials and physical measurements
All reagents and solvents were commercially available and used
without any further purification, except for ligand H3idbt, which
was synthesized according to the literature.[45] Inductively coupled
plasma spectra (ICP) were performed on a Thermo ICAP 6500 DUO
spectrometer. The FTIR spectra were recorded in the region of
400–4000 cmÀ1 on a Bruker Tensor 27 spectrophotometer from KBr
pellets. Elemental analysis was performed on a FLASH EA 1112 ele-
mental analyzer. Powder X-ray diffraction (PXRD) patterns were re-
corded using CuKa1 radiation on a PANalytical X’Pert PRO diffrac-
tometer. Thermogravimetric analyses (TGA) were implemented on
a Netzsch STA 449C thermal analyzer and the samples were heated
at a rate of 108C minÀ1 under air atmosphere. A Hitachi TM-1000
field emission scanning electron microscopy (SEM) was used to
image the particles size and morphologies. The BET surface of crys-
tal was collected on Micromeritics ASAP 2420 Accelerated Surface
Area under ultrahigh vacuum in a clean system, with a diaphragm
and turbo pumping system. Ultrahigh-purity-grade (> 99.999%) N2
gas was applied in the adsorption measurements. The experimen-
Scheme 1. Proposed mechanism for the synthesis of mono-oxazolines cata-
lyzed by micro Zn-based CPs.
1
afford II. Cyclization of II gives the final product and releases
the catalyst for the next catalytic cycle.
tal temperature was maintained by liquid nitrogen (77 K). H and
13C NMR spectra were conducted on a Bruker Avance-400 spec-
trometers. High-resolution mass spectra (HRMS-ESI) were recorded
with a Micro Q-TOF mass spectrometer.
In addition, compared with the previous Lewis acid homoge-
neous catalyst for the cyclization reaction,[26,44] micro CPs 1–2
as heterogeneous catalysts could yield several principal advan-
tages, such as high selectivity, reusability, easy separation, and
environmental friendliness. Furthermore, we have also exam-
ined the recyclability and stability of 1–2 for the catalytic reac-
tion with 4a. In the recyclability experiments, catalysts 1–2
were readily recovered from the catalytic reaction by filtration,
and could be recycled and reused at least five times (Figure S5
in the SI). Moreover, the PXRD patterns of the microcrystallites
of 1–2 after the fifth catalytic reaction closely matched those
of single crystals of 1–2 and showed no signs of framework
collapse and decomposition, which indicates that the frame-
work could remain intact after at least five cycles (Figure S6 in
the SI).
Synthesis of [{Zn6(idbt)4(phen)4}·3 H2O]n (1)
A
mixture of ZnSO4 (0.016 g, 0.10 mmol), H3idbt (0.020 g,
0.10 mmol), and phen (0.020 g, 0.10 mmol) was dissolved in N,N’-
dimethylformamide (DMF, 5 mL)/H2O (3 mL) at room temperature.
The reaction mixture was heated at 1608C for 3 days in a 25 mL
Teflon-lined stainless-steel autoclave. Upon cooling of the reactor
to room temperature at a rate of 58C hÀ1, filtration of the reaction
mixture afforded colorless crystals. The products were filtered and
collected (yield ꢀ36% based on Zn). Anal. Calcd (%) for
C68H42N48O3Zn6: C, 41.42; H, 2.15; N, 34.10. Found: C, 41.88; H, 2.03;
N, 34.15. IR (KBr): n˜ =3444 (s), 3060 (w), 3020 (w), 1136 (m), 1104
(m), 1026 (m), 728 (vs), 672 (w) cmÀ1
.
Synthesis of microcrystalline 1 in the presence of PVP-
1300000
ZnSO4 (0.032 g, 0.20 mmol), H3idbt (0.040 g, 0.20 mmol), phen
(0.040 g, 0.20 mmol), and PVP-1300000 (0.15 g) were mixed in a so-
lution of DMF/H2O (5/3 mL) and stirred at room temperature for
0.5 h to obtain a uniform mixture. The reaction mixture was
heated at 1608C hÀ1 for 3 days in a 25 mL Teflon-lined stainless-
steel autoclave. The reactor was cooled to room temperature at
a rate of 58C hÀ1. The microcrystalline of 1 were isolated by centri-
fugation and washing with ethanol and water (yield ꢀ33% based
on Zn).
Conclusions
In conclusion, by using tetrazole-appended imidazole (H3idbt)
as a rigid and conjugated clamp-like ligand, two catalytically
active zinc(II)-based CPs were successfully obtained by the sol-
vothermal reactions with good yields. In addition, their micro-
crystallines were successfully produced by hydrothermal meth-
ods in the presence of PVP-1300000, CTAB or SDS as surfac-
tants. For both the micro CPs, as the surfactants concentration
increased, their crystallite sizes could be scaled down to the
micrometer regime. For the tandem condensation–cyclodehy-
dration reaction of the amino alcohol and dinitriles, micro CPs
1 and 2 showed good catalytic ability for the selective synthe-
sis of mono-oxazolines by virtue of their immobilizing well-de-
fined catalytic sites. Moreover, they could be easily recovered
by filtration and reused at least after five cycles without signifi-
cant loss of yield. This approach provided a new strategy for
the design of efficient heterogeneous catalysts for the selective
synthesis of mono-oxazolines.
Synthesis of microcrystalline 1 in the presence of CTAB
The procedure is similar to that of microcrystalline 1 prepared with
PVP-1300000, except that CTAB (0.15 g) was used instead of PVP-
1300000 (0.15 g). The products were isolated and collected (yield
ꢀ34% based on Zn).
Synthesis of microcrystalline 1 in the presence of SDS
The procedure is similar to that of microcrystalline 1 prepared with
PVP-1300000, except that SDS (0.15 g) was used instead of PVP-
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1300000 (0.15 g). The products were isolated and collected (yield
ꢀ30% based on Zn).
lysts were used for the 2nd run without further activation, and the
same processes were repeated for the next run.
Synthesis of [{Zn3(idbt)2(H2O)4}·2H2O]n (2)
Crystal data collection and refinement
A mixture of Zn(NO3)2 (0.019 g, 0.10 mmol) and H3idbt (0.010 g,
0.05 mmol) was dissolved in EtOH (4 mL) and NH3·H2O (4 mL) at
room temperature. The reaction mixture was heated at 1308C for
3 days in a 25 mL Teflon-lined stainless-steel autoclave. Upon cool-
ing of the reactor to room temperature at a rate of 58C hÀ1, filtra-
tion of the reaction mixture afforded colorless crystals. The prod-
ucts were filtered and collected (yield ꢀ45% based on Zn). Anal.
Calcd (%) for C10H14N20O6Zn3: C, 16.98; H, 2.00; N, 39.63. Found: C,
16.81; H, 2.10; N, 39.52. IR (KBr): n˜ =3337 (w), 3169 (w), 1559 (m),
The data of complex 1 was collected on a SuperNova diffractome-
ter with graphite monochromated CuKa radiation (l=1.54178 Š) at
293(2) K, whereas the data of complex 2 was collected on a Rigaku
Saturn 724 CCD diffractometer with MoKa radiation (l=0.71073 Š)
at 293(2) K. Absorption corrections were applied by using a numeri-
cal program. The data were modified for Lorentz and polarization
effects. The structures were determined by immediate methods
and refined with a full-matrix least-squares technique based on F2
with the SHELXL-97 crystallographic software package.[46] Hydrogen
atoms were placed at calculated positions and refined as riding
atoms with isotropic displacement parameters. Crystallographic
data and structure processing parameters for 1 and 2 are summar-
ized in Table S2 in the Supporting Information. Selected bond
lengths and bond angles of 1 and 2 are listed in Table S3 of the
Supporting Information. CCDC 1439274 (1), and 1439275 (2) con-
tain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre.
1272 (m), 1245 (m), 1131 (s), 992 (vs), 695 (s), 665 (vs) cmÀ1
.
Synthesis of microcrystalline 2 in the presence of PVP-
1300000
A mixture of Zn(NO3)2·6H2O (0.038 g, 0.20 mmol), H3idbt (0.020 g,
0.10 mmol), and PVP-1300000 (0.15 g) was added into a 25 mL
Teflon-lined stainless steel vessel. Then, 4 mL ethanol solution was
added. The reaction mixture was stirred at room temperature for
0.5 h. After that, 4 mL NH3·H2O was added and stirred at room tem-
perature for another 10 min. The reaction mixture was kept in
a 25 mL Teflon-lined stainless steel vessel at 1308C for 3 days. After
cooling, the reaction system was isolated by centrifuging and
washed with ethanol and water to remove the supernatant (yield
ꢀ42% based on Zn).
Acknowledgements
This work was funded by the National Natural Science Founda-
tion (Nos. 21201152; 21371155), Research Fund for the Doctor-
al Program of Higher Education of China (20124101110002),
and the Student Innovative Funded Projects of Zhengzhou
University (201510459049).
Synthesis of microcrystalline 2 in the presence of CTAB
The procedure is similar to that of microcrystalline 2 prepared with
PVP-1300000, except that CTAB (0.15 g) was used instead of PVP-
1300000 (0.15 g). The products were isolated and collected (yield
ꢀ44% based on Zn).
Keywords: heterogeneous catalysis
oxazolines · polymers · surfactants
·
microcrystallines
·
Synthesis of microcrystalline 2 in the presence of SDS
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Manuscript received: March 29, 2016
Accepted Article published: May 2, 2016
Final Article published: May 24, 2016
Chem. Asian J. 2016, 11, 1856 – 1862
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ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim