Fe3O4@Propylsilane@Histidine[HSO4 -] magnetic nanocatalysts: Synthesis, characterization and catalytic application for highly efficient synthesis of xanthene derivatives

Article abstract of DOI:10.1002/aoc.4242

The surface of Fe₃O₄ magnetic nanoparticles (MNPs) was modified by chloropropylsilane and histidine. The imidazole group of prepared Fe₃O₄@Propylsilane@Histidine MNPs converted to imidazolium hydrogen sulfate gr

Full text of DOI:10.1002/aoc.4242

Received: 22 September 2017
DOI: 10.1002/aoc.4242
Revised: 22 November 2017
Accepted: 26 November 2017
F U L L P A P E R
‐
Fe O @Propylsilane@Histidine[HSO ] magnetic
3
4
4
nanocatalysts: Synthesis, characterization and catalytic
application for highly efficient synthesis of xanthene
derivatives
Seyyedeh Masoumeh Mousavifar | Hassan Kefayati
| Shahab Shariati
Department of Chemistry, Rasht Branch,
The surface of Fe O4 magnetic nanoparticles (MNPs) was modified by
Islamic Azad University, Rasht, Iran
3
chloropropylsilane and histidine. The imidazole group of prepared
Correspondence
Fe O @Propylsilane@Histidine MNPs converted to imidazolium hydrogen
3
4
Hassan Kefayati, Department of
Chemistry, Rasht Branch, Islamic Azad
University, Rasht, Iran.
sulfate group and Fe O ] as a novel environ-
3 4 4
@Propylsilane@Histidine [HSO ‐
mentally friendly ionic liquid/ magnetite nanoparticle was prepared, success-
fully. FT‐IR, XRD, SEM and TEM instruments was used to identifiy the
histidine ionic liquids/magnetite nanoparticles (HILMNPs). The catalytic
activity of synthesized HILMNPs was appraised for the synthesis of 9‐aryl‐1,8‐
dioxooctahydroxanthene and spiro[indoline‐3,9′‐xanthene]trione derivatives.
The activity of HILMNPs was much better than the other reported heteroge-
neous and homogeneous catalysts. Furthermore, the prepared catalyst could
be separated from the reaction mixture and reused four times without any
significant loss in its activity.
Email: kefayati@iaurasht.ac.ir;
haskefayati@gmail.com
KEYWORDS
3 4
9‐Aryl‐1,8‐dioxooctahydroxanthene, Fe O , histidine, magnetic nanoparticle, spiro[indoline‐3,9′‐
xanthene]trione
1
| INTRODUCTION
Among them, the use of iron oxide nanoparticles
Fe O ) has been noticed extremely due to their magnetic
(
3
4
Amino acids are the basic building blocks of proteins and
properties and several field applications as catalyst,
sensor, adsorbent and in drug delivery. Functionalized
iron oxide MNPs are an important category of functional
materials, which have been used as catalyst in organic
[1]
contribute in all major processes in organisms. Many
researchers have tried to design catalysts that match the
[2]
properties and performance of an enzyme. Histidine is
a common coordinating ligand in metallo proteins and
acts as an important and essential part of catalytic site in
certain enzymes. Furthermore, the linear and cyclic
peptides containing (S)‐histidine, as asymmetric organic
catalysts, have successfully been used for different impor-
[
12]
synthesis.
A practical method for green and efficient
organic transformation can be combination of iron oxide
nanoparticles with ionic liquids. This ionic liquid/nano-
particle catalytic system can increase the reaction rates
[
13]
than other classical organic synthesis.
[3]
tant asymmetric synthesis.
Xanthene derivatives are very important in medicinal
chemistry due to biological activity. They are also applied
Recently, modification of magnetic nanoparticles
MNPs) with a series of polymers and some small organic
compounds has been extensively investigated.
(
in pigments, dye components in laser technology and
[
4–11]
[14,15]
fluorescent for detection of biomolecules.
Among
Appl Organometal Chem. 2018;e4242.
wileyonlinelibrary.com/journal/aoc
Copyright © 2018 John Wiley & Sons, Ltd.
1 of 12
https://doi.org/10.1002/aoc.4242

2
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MOUSAVIFAR ET AL.
them, 9‐arylxanthene‐1,8‐diones is found in many of the
Oxford Instruments Field Emission Scanning Electron
Microscope. Elemental analysis was carried out on a
Thermo Finnigan Flash EA 1112 series instrument.
natural products and is used as multifunctional synthons
[16]
due to the pyran ring.
Various methods for the
synthesis of 9‐arylxanthene‐1,8‐diones are described in
the literature via condensation of aromatic aldehydes
and 1,3‐cyclic diketone using various catalysts such as
2
.2 | Preparation of
[17]
2– [18]
[19]
Fe O @Chloropropylsilane (Fe O @CPS)
magnetite nanoparticle
NaHSO ·SiO ,
sulfuric acid,
TiO /SO4
,
Dowex‐50 W,
silica
3
4
3 4
4
2
2
[20]
[21]
[22]
ZrOCl ·8H O,
InCl ·4H O,
SmCl3,
2
2
3
[25]
2
[
23]
3+
[24]
CaCl ,
Fe ‐montmorillonite,
FeCl3‐
2
Fe O magnetite nanoparticles (MNPs) were prepared as
our prior reports with a diameter smaller than 15 nm.
Fe O NPs were functionalized with chloropropyl groups
by adding prepared Fe O NPs (5 g) and 3‐chloropropyl
trimethoxysilane (CPS) (16 mmol, 3 mL) in dry toluene
3
4
[
26]
[27]
SiO ,
Alumina‐sulfuric acid
Also, synthesis of spiro[indoline‐3,9′‐xanthene]
and amberlyst‐15 cata-
[31]
2
[
28]
lyst.
3
4
trione derivatives in the presence of some catalyst such
3
4
[29]
[30]
as p‐TSA
and SBA‐15‐Pr–SO H
was reported.
3
However, despite the usefulness of these methods,
most of them have disadvantages such as harsh condi-
tions, low yield of products and long reaction time and
sometimes use of expensive, toxic and non‐reusable cata-
lyst. Thus, the use of an efficient separable and reusable
catalyst for the synthesis of the xanthene derivatives can
still be useful.
(
40 mL) into a round‐bottom flask. The mixture was
refluxed for 24 h. The obtained nanoparticles were
collected with a magnet (1.4 T) and washed with THF
(
2 × 10 mL) and then with distilled water (2 × 10 mL)
and finally dried at room temperature.
These considerations, according to our recent investi-
gation on the design of new synthetic methods by
2
.3 | Preparation of
‐
Fe O @Propylsilane@Histidine [HSO ]
3
4
4
[31]
[32]
‐
nanocatalysts
especially using ionic liquids
led us
(Fe O @PS@His[HSO ]) ionic liquid/
3 4 4
to develop a new, simple, and operating procedure
for the one‐pot synthesis of 9‐aryl‐1,8‐dioxo‐
octahydroxanthene and spiro[indoline‐3,9′‐xanthene]
trione derivatives. For this purpose, for the first time,
magnetite nanoparticles
The prepared Fe O @CPS (1 g) was suspended in 30 mL
3
4
dry toluene. Excess amounts of histidine (0.52 g,
.35 mmol) and triethylamine (0.47 mL, 3.35 mmol) were
3
Fe O4 magnetic nanoparticles were functionalized by
3
added to the mixture, and the mixture was stirred under
reflux conditions for 24 h. The resultant solid was
separated magnetically and then washed with toluene
histidine ionic liquid and then their performance as
effective, recoverable and stable catalysts for the conden-
sation reaction of dimedone and aromatic aldehydes or
isatin derivatives was investigated to afford biologically
active xanthenes.
(
2 × 10 mL), dichloromethane (2 × 10 mL), and a mixture
of methanol‐water (50:50, 2 × 10 mL) respectively, to
remove the unreacted residue of the histidine and finally
dried at 100 °C for 24 h.
2
2
| EXPERIMENTAL
Histidine ionic liquid/magnetite nanoparticles were
prepared by stirring of Fe O @PS@His (1 g) and 30 mL
3
4
.1 | Material and instruments
H SO (0.05 M) at room temperature for 24 h. The obtained
2
4
solid catalyst were filtered and washed (3 × 10 mL) with
ethanol and dried at 110 °C for 24 h.
All Chemical materials and solvents were purchased from
Merck. Melting points were determined using an Electro
Thermal IA 9100 apparatus. Bruker Advance DRX‐400
or DRX‐250 MHz instrument using TMS as internal stan-
dard was used for obtaining H and C NMR spectra.
Fourier transform infrared (FT‐IR) spectra were recorded
2.4 | General method for the synthesis of
‐aryl‐1,8‐dioxooctahydroxanthenes (3a‐h)
1
13
9
and spiro[indoline‐3,9'‐xanthene]trione
derivatives (5a‐e)
with potassium bromide pellets in the range of 400‐
1
4
000 cm‐ with a Shimadzu FT‐IR 8600 spectrophotome-
ter. Nanostructures were detected using a Philips Xpert
X‐ray powder diffraction (XRD) diffractometer (CuKα,
radiation, λ=0.154056), at a scanning speed of 2°/min
from 10° to 80° (2θ). Transmission electron microscopy
A mixture of an aromatic aldehyde or isatin derivatives
‐
(1 mmol), dimedone (2 mmol), Fe O @PS@ His[HSO ]
3
4
4
(0.08 g) and ethanol (8 mL) was refluxed. Upon comple-
tion of the reaction, as indicated by TLC, 5 mL ethanol
was added and the precipitate was dissolved at the hot
ethanol and magnetic nanocatalyst was separated with a
magnet (1.4 T). The crude products (3a‐h, 5a‐e) were
(TEM) measurements were carried out on a Zeiss‐
EM10C‐100 KV instrument. The scanning electron micro-
scope (SEM) images were visualized by a Sigma Zeiss,

MOUSAVIFAR ET AL.
3 of 12
obtained by cooling at room temperature and recrystal-
lized by ethanol.
33.5, 33.8, 41.6, 52.1, 116.9, 123.5, 133.8, 147.6, 154.2,
169.5, 198.7.
2
2
.5 | Spectroscopic data
2.5.5 | 9‐(4‐Bromophenyl)‐3,3,6,6‐
tetramethyl‐3,4,5,6,7,9‐hexahydro‐1H‐xan-
thene‐1,8(2H)‐dione (3e)
.5.1 | 3,3,6,6‐Tetramethyl‐9‐(3‐nitrophe-
nyl)‐3,4,5,6,7,9‐hexahydro‐1H‐xanthene‐
‐
1
1,8(2H)‐dione (3a)
mp: 238‐240 °C; IR (KBr) (v /cm ): 2952, 1660, 1625,
max
1
‐
1
1558, 1469, 1197; H NMR (400 MHz, CDCl
) δ (ppm):
3 H
mp: 170‐172 °C; IR (KBr) (v /cm ): 3055, 2960, 1662,
max
1
1.00 (s, 6H), 1.11 (s, 6H), 2.17 (d, J = 16.4 Hz, 2H), 2.25
1
623, 1523, 1469; H NMR (400 MH , CDCl ) δ (ppm):
Z 3 H
(
=
d, J = 16.4 Hz, 2H), 2.47 (s, 4H), 4.71 (s, 1H), 7.19 (d, J
8.2 Hz, 2H), 7.34 (d, J = 8.2 Hz, 2H); C NMR
0
.99 (s, 6H), 1.11 (s, 6H), 2.14 (d, J = 16.5 Hz, 2H), 2.24
13
(d, J = 16.5 Hz, 2H), 2.50 (s, 4H), 4.82 (s, 1H), 7.40 (t, J
(
100 MHz, CDCl ) δ (ppm): 27.4, 29.4, 31.5, 32.2, 40.8,
3 c
=
8.0, 1H), 7.76 (d, J = 7.6 Hz, 1H), 7.96 (d, J = 7.2 Hz,
13
50.7, 115.1, 120.2, 130.2, 131.1, 143.2, 162.5, 196.4.
1
2
1
H), 8.07 (s, 1H); C NMR (100 MH , CDCl ) δ (ppm):
Z 3 c
7.3, 29.2, 32.1, 32.2, 40.8, 50.6, 114.4, 121.6, 122.8, 128.8,
35.4, 146.4, 148.2, 163.1, 196.4.
2
.5.6 | 9‐(4‐Methoxyphenyl)‐3,3,6,6‐
tetramethyl‐3,4,5,6,7,9‐hexahydro‐1H‐xan-
thene‐1,8(2H)‐dione (3f)
2
.5.2 | 9‐(2,4‐Dichlorophenyl)‐3,3,6,6‐
tetramethyl‐3,4,5,6,7,9‐hexahydro‐1H‐xan-
thene‐1,8 (2H)dione (3b)
mp: 238‐241 °C; IR (KBr) (vmax/cm‐1): 3050, 2954, 1666,
1
1
622, 1558, 1510, 1460; H NMR (400 MHz, CDCl ) δ
3
H
‐
1
(ppm): 1.00 (s, 6H), 1.10 (s, 6H), 2.17 (d, J = 16.4 Hz,
2H), 2.24 (d, J = 16.4 Hz, 2H), 2.47 (s, 4H), 3.73 (s, 3H),
mp: 253‐255 °C; IR (KBr) (v /cm ): 3066, 2956, 1676,
max
1
1
1
4
621, 1552, 1465; H NMR (400 MHz, CDCl ) δ (ppm):
3 H
4
.70 (s, 1H), 6.76 (d, J = 8.4 Hz, 2H), 7.21 (d, J = 8.4 Hz,
.03 (s, 6H), 1.13 (s, 6H), 2.11‐2.21 (m, 4H), 2.42 (s, 4H),
13
1
3
2H); C NMR (100 MHz, CDCl ) δc (ppm): 27.3, 29.3,
3
.85 (s, 1H), 7.13‐7.45 (m, 3H); C NMR (100 MHz,
3
1
1.0, 32.2, 40.8, 50.8, 55.1, 113.4, 115.7, 129.3, 136.5,
58.0, 162.1, 196.6.
CDCl ) δ (ppm): 27.6, 29.6, 32.0, 32.4, 41.5, 51.2, 114.1,
26.7, 128.8, 131.5, 132.2, 133.8, 140.5, 164.5, 194.8.
3
c
1
2
3
.5.7 | 3,3,6,6‐Tetramethyl‐9‐phenyl‐
2
3
.5.3 | 3,3,6,6‐Tetramethyl‐9‐p‐tolyl‐
,4,5,6,7,9‐hexahydro‐1H‐xanthene‐1,8(2H)‐
,4,5,6,7,9‐hexahydro‐1H‐xanthene‐1,8(2H)‐
dione (3g)
dione (3c)
‐1
‐
1
mp: 203‐205 °C; IR (KBr) (vmax/cm ): 2962, 2928, 1592,
mp: 212‐214 °C; IR (KBr) (v /cm ): 2952, 1664, 1627,
max
1
1
1372, 1159, 1041, 842; H NMR (400 MHz, CDCl ) δ
1
558, 1512, 1461; H NMR (400 MHz, CDCl ) δ (ppm):
3 H
3
H
(
(
ppm): 1.15 (s, 6H), 1.26 (s, 6H), 2.26‐2.50 (m, 8H), 5.47
s, 1H), 7.04‐7.08 (d, J = 7.93 Hz, 2H), 7.12‐7.17 (m, 1H),
1
.01 (s, 6H), 1.11 (s, 6H), 2.17 (d, J = 12 Hz, 2H), 2.24
(d, J = 12 Hz, 2H), 2.25 (s, 3H), 2.48 (s, 4H), 4.73 (s,
13
7
2
1
.24‐7.28 (m, 2H); C NMR (100 MHz, CDCl ) δ (ppm):
8.2, 29.8, 32.3, 33.6, 46.4, 46.8, 116.5, 126.9, 127.5, 128.2,
38.3, 189.3, 190.6.
1
H), 7.03 (d, J = 7.7 Hz, 2H), 7.20 (d, J = 7.7 Hz, 2H);
C NMR (100 MHz, CDCl ) δ (ppm): 21.1, 27.5, 29.1,
3
c
1
3
3
c
3
1
1.4, 32.2, 40.8, 50.8, 115.7, 128.3, 128.8, 135.7, 141.3,
62.2, 196.5.
2
.5.8 | 9‐(2‐Chlorophenyl)‐3,3,6,6‐
2
.5.4 | 3,3,6,6‐Tetramethyl‐9‐(4‐nitrophe-
nyl)‐3,4,5,6,7,9‐hexahydro‐1H‐xanthene‐
,8(2H) dione (3d)
tetramethyl‐3,4,5,6,7,9‐hexahydro‐1H‐xan-
thene‐1,8(2H)‐dione (3h)
1
‐1
mp: 231‐233 °C; IR (KBr) (vmax/cm ): 3485, 1649, 1646,
1581; H NMR (400 MHz, CDCl ) δ (ppm): 1.08 (s, 6H),
1.15 (s, 6H), 2.27 (d, J = 16.2 Hz, 2H), 2.39 (d, J =
‐
1
1
mp: 220‐222 °C; IR (KBr) (v /cm ): 3055, 2960, 1662,
max
3
H
1
1
623, 1523, 1469; H NMR (400 MHz, CDCl ) δ (ppm):
3
H
0
.98 (s, 6H), 1.14 (s, 6H), 2.16 (d, J = 16.2 Hz, 2H), 2.24
16.2 Hz, 2H), 2.76 (s, 4H), 5.53 (s, 1H), 7.19‐7.52 (m,
13
(d, J = 16.2 Hz, 2H), 2.53 (t, J =17.5 Hz, 4H), 4.83
4H); C NMR (100 MHz, CDCl ) δc (ppm): 28.7, 29.5,
3
(
2
s, 1H), 7.38 (d, J = 8.1 Hz, 2H, 8.04 (2H, J = 8.1 Hz,
H); C NMR (100 MHz, CDCl ) δ (ppm): 27.8, 29.9,
3 c
33.2, 34.6, 42.4, 52.1, 118.1, 128.2, 130.2, 132.5, 133.3,
133.8, 140.8, 167.3, 198.2.
13

4
of 12
MOUSAVIFAR ET AL.
2
.5.9 | 1,3',3',6',6'‐Pentamethyl‐3',4',6',7'‐
tetrahydrospiro[indoline‐3,9'‐xanthene]‐
',2,8' (2'H, 5'H) –trione (5a)
DMSO, d
6
) δc (ppm): 11.8, 27.5, 28.1, 32.9, 36.0, 43.2,
46.4, 51.8, 108.8, 115.7, 122.8, 123.1, 128.6, 134.3, 145.4,
165.5, 178.0, 196.5.
1
‐
1
mp: >300 °C; IR (KBr) (vmax/cm ): 3054, 2910, 1720,
1
l700, 1599, 1475; H NMR (400 MHz, DMSO, d ) δ
(
6
H
2.5.13 | Benzyl‐3ˊ,3ˊ,6ˊ,6ˊ‐tetramethyl‐
ppm): 1.06 (s, 6H), 1.13 (s, 6H), 2.05 (d, J = 15.4 Hz,
H), 2.26 (d, J = 15.4 Hz, 2H), 2.44 (d, J = 15.6 Hz, 2H),
.54 (d, J = 15.4 Hz, 2H), 3.38 (s, 3H), 6.70‐7.18 (m, 4H);
C NMR (100 MHz, DMSO, d ) δc (ppm): 25.7, 27.8,
8.1, 33.9, 41.3, 45.5, 52.9, 108.5, 115.0, 122.8, 122.9,
29.0, 136.0, 142.2, 160.0, 172.6, 198.0.
3
ˊ,4ˊ,6ˊ,7ˊ‐tetrahydrospiro[indoline‐3,9ˊ‐xan-
2
2
thene]‐1ˊ,2,8ˊ(2ˊH,5ˊH)‐trione (5e)
13
mp: 255 °C; IR (KBr) (vmax/cm‐1): 3064, 2955, 1714,
6
1
1
673, 1605, 1478; H NMR (400 MHz, DMSO, d ) δ
6
H
2
1
(
ppm): 1.08 (s, 6H), 1.19 (s, 6H), 2.14 (d, J = 15.6 Hz,
2
2
H), 2.29 (d, J = 15.6 Hz, 2H), 2.46 (d, J = 15.8 Hz, 2H),
.59 (d, J = 15.8 Hz, 2H), 5.07 (br s, 2H), 6.46‐7.70 (m,
13
2
.5.10 | 1‐(2,4‐Dichlorobenzyl)‐3',3',6',6'‐
9H); C NMR (100 MHz, DMSO, d ) δc (ppm): 27.8,
6
tetramethyl‐3',4',6',7'‐
28.1, 31.0, 32.0, 41.6, 45.7, 51.9, 109.5, 110.5, 114.7, 122.8,
125.3, 129.3, 129.6, 129.9, 130.8, 132.2, 134.1, 146.3,
170.5, 199.4.
tetrahydrospiro[indoline‐3,9'‐xanthene] ‐
1
',2,8'(2'H,5'H)‐trione (5b)
‐1
Mp: 242‐244 °C; IR (KBr) (vmax/cm ):3095, 2956, 2885,
1
1
726, 1672, 1608, 1558, 1463; H NMR (400 MHz, DMSO,
3
| RESULTS AND DISCUSSION
.1 | Preparation of histidine ionic
d ) δ (ppm): 0.85 (s, 12H), 1.89 (d, 2H), 1.96 (d, 2H), 2.09
6
H
(
(
d, 2H), 2.21 (d, 2H), 4.96 (dd, J = 12.4, 2H), 6.73‐7.91
3
13
m,7H); C NMR (100 MHz, DMSO, d ) δc (ppm): 26.4,
6
liquids/magnetite nanoparticles
HILMNPs)
2
1
1
6
9.1, 31.6, 33.7, 50.4, 54.1, 59.5, 100.7, 101.4, 109.3, 110.9,
21.9, 123.3, 127.8, 128.4, 129,2, 129.7, 132.8, 144.8,
45.7, 169.4, 204.4. Anal. Calcd. for C H Cl NO : C,
(
Scheme 1 shows the sequence for preparation of
Fe O @PS@His[HSO ]. The bare MNPs were synthe-
31
29
2
4
‐
7.64; H, 5.31; N, 2.54; Found: C, 67.48; H, 5.20; N, 2.59.
3
4
4
sized by chemical coprecipitation method according to
[
31]
the literature.
For the preparation of chloropropylated
2
3
.5.11 | 1‐Benzoyl‐3',3',6',6'‐tetramethyl‐
',4',6',7'‐tetrahydrospiro[indoline‐3,9'‐xan-
functionalized Fe O , 3‐chloropropyltrimethoxysilane
was directly coated on the MNPs backbones.
3
4
thene]‐1',2, 8'(2'H,5'H)‐trione (5c)
To provide the desired HILMNPs, we evaluated
reaction of histidine with functionalized Fe O @CPS
‐
1
3
4
Mp: >300 °C; IR (KBr) (vmax/cm ):3105, 2956, 2883,
1
magnetic nanoparticles. According to the isoelectric struc-
tures of histidine in different pHs (Figure 1), the reaction
of Fe O @CPS with histidine was done in the presence of
1
726, 1689, 1680, 1604, 1473; H NMR (250 MHz, DMSO,
d6) δH (ppm): 0.92 (s, 6H), 1.00 (s, 6H), 2.00 (d, J =
3
4
1
2
5.0 Hz, 2H), 2.17 (d, J = 15.0 Hz, 2H), 2.50 (d, J = 17.5,
H), 2.62 (d, J = 17.5, 2H), 6.67‐7.04 (m, 4H), 7.34‐7.49
‐
triethylamine. Finally, Fe O @PS@His[HSO ] was pre-
3
4
4
13
pared by stirring of Fe O @PS@His and H SO .
3 4 2 4
(m, 5H); C NMR (62.5 MHz, DMSO, d ) δc (ppm):
6
2
1
1
6.5, 26.8, 28.6, 31.1, 42.2, 58.6, 100.1, 100.9, 108.0, 109.3,
11.2, 112.5, 119.8, 121.1, 121.5, 127.5, 133.1, 144.3,
67.0, 168.1, 194.1. Anal. Calcd. for C H NO : C, 75.13;
3
.2 | Characterization of the prepared
31
29
5
novel HILMNPs
H, 5.90; N, 2.83; Found: C, 74.81; H, 5.86; N, 2.89.
Characterization of the prepared novel HILMNPs was per-
formed by several physiochemical methods such as FT‐IR,
XRD, SEM, and TEM. Figure 2 shows the FT‐IR spectra of
the functionalized magnetic nanoparticles. For all synthe-
sized MNPs, the absorption band at 468 and 580 cm‐ is
related to the Fe‐O vibrations of the magnetite. The evi-
dences for the chloropropyl functionalized nanoparticles
2
3
.5.12 | Ethyl‐3ˊ,3ˊ,6ˊ,6ˊ‐tetramethyl‐
ˊ,4ˊ,6ˊ,7ˊ‐tetrahydrospiro[indoline‐3,9ˊ‐xan-
thene]‐1ˊ, 2,8ˊ(2ˊH,5ˊH)‐trione (5d)
1
mp: 203 °C; IR (KBr) (vmax/cm‐1): 3008, 2923, 1730,
1
1
708, 1615, 1468; H NMR (400 MHz, DMSO, d ) δ
6
H
‐
1
(
2
(
ppm): 1.03 (s, 6H), 1.15 (s, 6H), 1.45 (t, J = 6.8 Hz, 3H),
.07 (d, J = 15.9 Hz, 2H), 2.33 (d, J = 15.9 Hz, 2H), 2.43
d, J = 15.8 Hz, 4H), 2.57 (d, J = 15.8 Hz, 4H), 3.95 (q, J
were observed by the peak at 1037 cm for Si‐O stretching,
‐
1
and the peak about 1134 cm for Si‐C bond. Also, the peak
at 2925 cm‐ was assigned to CH stretching vibration of
1
2
13
=
6.8 Hz, 2H), 6.92‐7.25 (m, 4H); C NMR (100 MHz,
chloro propyl groups (Figure 2a,2b). The absorption bands

MOUSAVIFAR ET AL.
5 of 12
3 4 4
SCHEME 1 The reaction sequence for the synthesis of Fe O @PS@His[HSO
‐]
FIGURE 1 Structures of histidine in
different pHs
‐
1
around 3400 and 1620 cm are due to the stretching and
Furthermore, the C=C stretching frequencies of imidaz-
[33,34]
‐1
deforming vibrations of surface adsorbed water.
In the spectrum Fe O @PS@His (Figure 2c) asymmet-
ric and symmetric stretching frequencies of carboxylate
ole ring of histidine are observed at ∼1460‐1600 cm .
Also, the peak at ∼3400 cm‐ is related to OH stretching
that has an overlap with stretching of N‐H. These results
indicate that the Fe O @CPS nanoparticles were success-
1
3
4
‐
‐1
(
COO ) are observed at 1637 and 1415 cm , respectively.
3
4
fully attached to the histidine molecules. In the spectra of
‐
‐1
Fe O @PS@His[HSO ] a broad band at 2700‐3100 cm
3
4
4
‐
confirmed that COO group of histidine was transformed
to COOH at the final step. Two additional bands at about
190 and 1260 cm‐ were assigned to symmetric and
1
1
asymmetric stretching band of the O=S=O moieties
respectively, which confirms the successful replacement
of chloride by the sulfate ions (Figure 2d).
XRD patterns of the bare Fe O , Fe O @CPS and
3
4
3 4
Fe O @PS@His and their indices are shown in Figure 3.
3
4
FIGURE 3 XRD patterns of Fe
3 4 3 4
O (a), Fe O @CPS (b) and
FIGURE
2
FT‐IR spectra of Fe
3
O
4
(a) Fe
‐] (d)
3 4
O @CPS (b),
Fe O @PS@His (c). The characteristic diffraction peaks are shown
3
4
Fe @PS@His (c), Fe
3
O
4
3
O
4
@PS@His[HSO
4
by their indices

6
of 12
MOUSAVIFAR ET AL.
The MNP patterns have peaks at 2θ = 30.1°, 35.4°, 43.1°,
3.4°, 57.0° and 62.6°, that confirm the crystalline cubic
microspheres were obtained with a diameter of about
18 nm. Also, the Fe O @PS@His nanoparticles have
5
3
4
spinel structure which is quite same to the pure cubic
phase of magnetite and compatible with the standard of
approximately spherical shapes with a diameter of about
25 nm. All above results show the successful coating of
the magnetic Fe O @PS@His nanoparticles.
[35]
Fe O XRD pattern.
The same peaks in the XRD pat-
3
4
3 4
terns of the Fe O @CPS and Fe O @PS@His MNPs with
The magnetic properties of the Fe O
and
Fe O @PS@His are measured using vibrating sample mag-
3
4
3
4
3 4
Fe O nanoparticles, indicate the presence of magnetite in
3
4
3 4
the cave of synthesized nanoparticles and accuracy syn-
thesis of the Fe O @CPS and Fe O @PS@His MNPs
netometer (VSM) and the curves are shown in Figure 5.
The saturation magnetization of Fe O at 25 °C was
3
4
3
4
3 4
[33,34]
‐1
without any phase changes.
The morphology of Fe O , Fe O @CPS and
78 emu g while for the Fe O @PS@His MNPs was 40
3 4
‐1
emug . These value show the superparamagnetic property
of the synthesized MNPs that are sufficient for a magnetic
separation with a conventional magnet. The decrease in
the saturation magnetization of coated Fe O was related
3
4
3 4
Fe O @PS@His nano‐particles were also observed by
3
4
SEM and TEM. As shown in Figure 4, the TEM and
SEM images show that Fe O particles were spherical
3
4
3 4
with uniform size, and showed good dispersity. Also, the
TEM and SEM images show that a basically core–shell
structure (dark colored core for Fe O nanoparticles and
light‐colored shell for PS‐His) was obtained with spherical
morphology after being coated with propylsilane and
histidine.
to the existence of coating on the surface of Fe O core.
3 4
The thermal behavior of Fe O @PS@His was investi-
3
4
gated by thermogravimetric analysis (TGA). As shown in
Figure 6, the weight loss of 8.2% below 270 °C was related
to the loss of adsorbed water molecules. TGA results
showed other weight decreasing from 300 to 680 °C due
to the decomposition of the organic groups (about 38%).
Thus, the TGA curve confirmed the successful
3
4
Furthermore, it was found that the diameter of Fe O4
3
nanoparticles obtained was about 15 nm and Fe O @CPS
3
4
FIGURE 4 TEM images of Fe
3
O
4
(a), Fe
3
O
4
@CPS (b), Fe
3
O
4
@PS@His[HSO
‐] before reaction (g) Fe
4
‐] before reaction (c) Fe
@PS@His[HSO
4
3
O
4
@PS@His[HSO
‐] after reaction (h),
‐] after reaction (d)
4
and SEM images of Fe
respectively
3
O
4
(e), Fe
3
O
4
@CPS (f), Fe
3
O
4
@PS@His[HSO
4
3
O
4

MOUSAVIFAR ET AL.
7 of 12
an acid in organic solvents. It can be calculated by the
equation below:
À
Á
þ
s
H ¼ pKðIÞ þ log ½Iꢀ =½IH ꢀ
0
aq
s
Wherein, ‘I’ represents the indicator base (generally
+
substituted p‐nitro aniline), [IH ] and [I] are the molar
s
s
concentrations of indicator in the protonated and
unprotonated forms, respectively. The pK(I)aq values are
already known (for example the pK(I)aq value of p‐nitro
aniline is 0.99). As Lambert–Beer's law describes, this
concentration ratio can be determined by measuring the
concentration in our experiments, the maximal absorbance
of p‐nitro aniline was observed at 329 nm. The optical
absorbance of indicator in the presence of
‐
Fe O @PS@His[HSO ] nanoparticles was weak com-
3
4
4
pared to that without presence of nanoparticles in CCl4
(Figure 7). As summarized in Table 1, the data obtained
3 4
FIGURE 5 Magnetic hysteresis curves of the (a) Fe O ; (b)
@PS@His[HSO ‐
4
]
Fe
3
O
4
from these evaluations afford the value of H = 0.48 for
0
functionalization of magnetic nanoparticles. Also, the
DTA curve (Figure 6) showed two endothermic processes
related to the removal of adsorbed water (at about 270 °C)
and decomposition of organic group (at about 630 °C),
respectively.
acidic strength of the ionic liquid. UV–Vis absorbance of
the indicator base at the maximal absorption wavelength
(λmax) was measured before and after adding acidic sample.
3.3 | Determination of the ionic liquid
acidity
The determination of ionic liquids acidity is a relatively
new subject, and it is the important property relevant to
ionic liquids catalytic activity for acid‐catalyzed reactions.
Recently, evaluation of Brønsted acidity of some ionic
liquids was reported by determination of the Hammett
acidity functions using UV–Vis spectroscopy (Hammett
method). In this method, a basic indicator to trap the dis-
FIGURE 7 Absorption spectra of p‐nitroaniline (at λmax = 329 nm)
[36–38]
sociative proton was used.
The Hammett acidity
as indicator without presence of MNPs (A) and in the presence of
‐
function can effectively illustrate the acidity strength of
Fe
3
O
4
@PS@His[HSO
4
] nanoparticles in CCl
4
solvent (B)
FIGURE 6 TGA and DTA diagram of
@PS@His[HSO ‐
Fe O ]
3 4 4

8
of 12
MOUSAVIFAR ET AL.
0 3 4 4
TABLE 1 Computation of Hammete acidity function (H ) of Fe O @PS@His[HSO
‐]
+
Entry
catalyst
A
max
[I]%
[IH ]
H
0
1
‐
2.2167
0.5238
100
0
‐
2
Fe
3
O
4
@PS@His[HSO ‐
4
]
23.63
76.37
0.48
: 1.44 × 10 mol L‐1 solution (10 mL) of p‐nitro aniline (pKa(I)aq = 0.99) as the base indicator; cat-
−
4
The conditions adopted for UV–Vis measurements in CCl
4
‐
alyst: Fe
3
O
4
@PS@His[HSO
4
], 10 mg, 25 °C.
TABLE 2 Effect of various catalysts in synthesis of 3,3,6,6‐tetramethyl‐9‐(3‐nitrophenyl)‐3,4,5,6,7,9‐hexahydro‐1H‐xanthene‐1,8(2H)‐dione
Entry
catalyst
Amount of catalyst (g)
Time (min)
Yeild (%)
1
NO catalyst
‐
60
no product
2
3
4
5
6
Fe
3
Fe
3
Fe
3
Fe
3
Fe
3
O
4
O
4
O
4
O
4
O
4
0.06
0.06
0.06
0.08
0.1
60
30
10
5
no product
@PS@His
@PS@His[HSO ‐
@PS@His[HSO ‐
@PS@His[HSO ‐
30
87
95
93
4
]
]
]
4
4
5
Reaction conditions: Dimedone (2 mmol), 3‐nitrobenzaldehyde (1 mmol), and ethanol (8 mL), reflux
3.4 | Method development
HILMNPs gave the best yield (95%) at the least time
(
5 min) (Table 2, entry 5).
The efficiency of prepared MNPs as catalysts were
examined in the synthesis of xanthene derivatives
Then, we tested different solvents and solvent‐free
conditions for this reaction in the presence of HILMNPs
(0.08 g) (Table 3). It was found that EtOH was the best
choice for the reaction and the desired product was
obtained in good yield.
(Table 2, Scheme 2). In the primary stage of our study,
we evaluate the efficiency of Fe O , Fe O @PS@His,
3
4
3 4
‐
Fe O @PS@His[HSO ] MNPs as catalysts for the reac-
3
4
4
tion of dimedone (2 mmol) and 3‐nitrobenzaldehyde
1 mmol) (Table 2). The results show that, the reaction
in the absence of Fe O as catalyst and in the presence
After determination of optimum conditions, the per-
formance of the HILMNPs as catalyst for the synthesis
of other xanthene derivatives were evaluated by reaction
of dimedone and aromatic aldehydes or isatin derivatives.
In all studied cases, HILMNPs gave the corresponding
products 3a–h and 5a‐e in better yields, and shorter times
(
3
4
of it not obtained any products, even with prolonged
reaction times (60 min) (Table 2, entries 1‐2). Also, the
reaction was promoted by Fe O @PS@His, but the yields
3
4
[
17–30]
were not so high until 30 min (Table 2, entries 3).
in comparison to previously reported
(Table 4).
‐
However, Fe O @PS@His[HSO ] (HILMNPs) obtained
A probable mechanism for the synthesis of the
products 3 and 5 using HILMNPs as catalyst is shown in
scheme 3. It seems, the imidazole cationic or anionic
3
4
4
product much better than the other catalysts. The amount
of HILMNPs was examined and we found that 0.08 g
TABLE 3 Effect of various solvents in synthesis of 3,3,6,6‐
tetramethyl‐9‐(3‐nitrophenyl)‐3,4,5,6,7,9‐hexahydro‐1H‐xanthene‐
1,8(2H)‐dione
Entry
Solvent
EtOH
CH CN
Condition
Time (min)
Yield (%)
1
Reflux
5
95
2
3
4
5
6
3
Reflux
100 °C
Reflux
Reflux
100 °C
5
5
82
87
64
55
20
DMF
CHCl
3
10
20
30
2
H O
Free
Reaction conditions: Dimedone (2 mmol), 3‐nitrobenzaldehyde (1 mmol) and
‐
SCHEME 2 Synthesis of xanthene derivatives
Fe
3
O
4
@PS@His[HSO
4
] (0.08 g)

MOUSAVIFAR ET AL.
9 of 12
TABLE 4 Synthesis of spiro[indoline‐3,9′‐xanthene]triones and 9‐aryl‐1,8‐dioxooctahydro xanthenes
Products
Structures
Time (min)
Yield (%)
Mp (°C)
Mp [lit]
(25)
3
a
5
95
170‐172
171‐173
(
17)
3
b
5
10
5
96
89
94
253‐255
212‐214
221‐223
251‐253
(25)
3
3
c
212‐214
(
25)
d
225–226
(
26)
3
3
e
f
5
91
90
238‐240
238‐241
240–241
242–245
(25)
10
(
25)
3
3
g
5
7
92
91
203‐205
231–233
203–205
(25)
h
230‐232
(30)
5
5
a
b
60
45
88
90
>300
>300
242‐244
‐
(Continues)

10 of 12
MOUSAVIFAR ET AL.
TABLE 4 (Continued)
Products Structures
Time (min)
Yield (%)
Mp (°C)
Mp [lit]
5
c
60
80
>300
‐
(
29)
5
d
e
50
60
88
86
203
255
201
258
(29)
5
Reaction conditions: Dimedone (2 mmol), aromatic aldehyde or isatin derivatives (1 mmol), catalyst (0.08 g) and ethanol (8 mL), reflux
SCHEME 3 Probable mechanism for
the synthesis of spiro[indoline‐3,9′‐
xanthene]triones and 9‐aryl‐1,8‐
dioxooctahydroxanthenes catalyzed by
HILMNPs

MOUSAVIFAR ET AL.
11 of 12
TABLE 5 Isolated yield of 3a over reuse of magnetic catalysts
ORCID
3 4 4
Fe O ]
@PS@His[HSO ‐
Catalyst
Run
Hassan Kefayati http://orcid.org/0000-0002-0818-054X
1
2
5
3
5
4
5
Time
Yield
5
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ACKNOWLEDGMENT
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Financial support by Rasht Branch, Islamic Azad
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