Magnetic CoFe2O4 nanoparticle immobilized N-propyl diethylenetriamine sulfamic acid as an efficient and recyclable catalyst for the synthesis of amides via the Ritter reaction

Article abstract of DOI:10.1016/j.apcata.2014.06.006

A magnetic CoFe₂O₄ nanoparticle immobilized diamine-N-sulfamic acid (CoFe₂O₄@SiO₂-DASA) was synthesized and used as efficient heterogeneous catalyst for the synthesis of amides via the Ritter reaction under solvent-free conditions. The magnetic nanocatalyst could be readily recovered by applying an external magnet and recycled several times without considerable loss of its catalytic activity.

Full text of DOI:10.1016/j.apcata.2014.06.006

Applied Catalysis A: General 482 (2014) 258–265
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Magnetic CoFe2O4 nanoparticle immobilized N-propyl
diethylenetriamine sulfamic acid as an efficient and recyclable
catalyst for the synthesis of amides via the Ritter reaction
Xiao-Na Zhao, Hai-Chuan Hu, Fu-Jun Zhang, Zhan-Hui Zhang∗
College of Chemistry and Material Science, Hebei Normal University, Nanerhuan East Road, Shijiazhuang 050024, Hebei, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A magnetic CoFe2O4 nanoparticle immobilized diamine-N-sulfamic acid (CoFe2O4@SiO2–DASA) was syn-
thesized and used as efficient heterogeneous catalyst for the synthesis of amides via the Ritter reaction
under solvent-free conditions. The magnetic nanocatalyst could be readily recovered by applying an
external magnet and recycled several times without considerable loss of its catalytic activity.
© 2014 Elsevier B.V. All rights reserved.
Received 9 March 2014
Received in revised form 29 May 2014
Accepted 4 June 2014
Available online 12 June 2014
Keywords:
Magnetic nanoparticle
Sulfamic acid functionalized CoFe2O4
Ritter reaction
Amides
1. Introduction
the final product after the reaction is complete. Although there
are many reports on the preparation and applications of immo-
From the standpoint of environmentally benign organic synthe-
sis, the design of novel, highly active and reusable immobilized
catalysts has become a major area of research. Though various
materials such as inorganic solids, polymers, ionic liquids have been
explored as supports. Increasing attention has recently been paid to
the use of nanoparticles (NPs) as supports due to their remarkable
advantages such as small size, large specific surface area, high dis-
persion property, good catalytic activity and selectivity, and easy
modifiable surface by chemical methods [1]. In this sense, magnetic
nanoparticles (MNPs) are arguably the most extensively investi-
gated and emerged as appealing catalyst supports [2–15]. Their
magnetic character makes them be effective and easily separated
from the reaction system by applying an external magnetic field,
which eliminates the necessity of tedious filtration, centrifugation
or membrane separation steps. Among the various MNPs as the core
magnetic supports, cobalt ferrite is one of the most versatile mag-
netic materials as they have moderate saturation magnetization,
inexpensiveness, high chemical stability and mechanical strength
[16–18]. On the other hand, sulfonic acid catalysts have been widely
used in various industries; however, it is often difficult to separate
bilization of sulfonic acid [19–26], to the best of our knowledge,
no reports were devoted to the grafting of sulfuric acid on cobalt
ferrite.
The Ritter reaction is a very efficient and widely used method
for the formation of amides. It is applied to a wide range of
substrates and has become one of the most influential meth-
ods for the synthesis of natural products and pharmaceuticals
[27–29]. Although there are many catalytic systems reported for
this reaction [30–37], only a few heterogeneous catalysts have
been described, including sulfated tungstate [38], silica-bonded
N-propyl sulphamic acid (SBNPSA) [39], silica boron–sulfuric
acid nanoparticles (SBSANs) [40], HClO4–functionalized silica-
coated magnetic nanoparticles [␥-Fe2O3@SiO2–HClO4] [41], silica
sulfuric acid [42], alumina–methanesulfonic acid (AMA) [43],
and magnetite-supported sulfonic acid (nanocat-Fe–OSO3H) [44].
Therefore, the research on the development of novel, more efficient,
cheaper, and more easily recovered catalysts for the Ritter reaction
is a particularly hot issue.
These results in combination with our recent work on
the designing magnetic nanocatalysts and their application in
organic synthesis [45–52], let us to present a new type of
magnetic CoFe2O4 nanoparticle immobilized diamine-N-sulfamic
acid (CoFe2O4@SiO2–DASA) as
green and efficient synthesis of amides via the Ritter reaction
(Scheme 1).
a powerful catalyst for the
∗
Corresponding author. Tel.: +86 31180787431; fax: +86 31180787431.
E-mail address: zhanhui@126.com (Z.-H. Zhang).
http://dx.doi.org/10.1016/j.apcata.2014.06.006
0926-860X/© 2014 Elsevier B.V. All rights reserved.

X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
259
acid (2 mL) in dichloromethane (15 mL). The chlorosulfonic acid
solution was added drop-wise over a period of 30 min at 0 ◦C.
After the addition was complete, the mixture was shaken for 1 h
until all HCl was removed from reaction vessel. Then, the product
was separated by magnetic decantation and washed thrice with
EtOH to remove unattached substrates. Finally, the obtained
sulphamic acid-functionalized magnetic CoFe2O4 nanoparticles
(CoFe2O4@SiO2–DASA) were dried under vacuum at 60 ◦C for 24 h.
Scheme 1. Synthesis of amides via the Ritter reaction.
2. Experimental
2.1. General
X-ray power diffraction (XRD) analysis was carried out on a PAN-
2.3. General procedure for synthesis of amides
A
mixture of alcohol (1 mmol), nitrile (1 mmol),
CoFe2O4@SiO2–DASA (0.1 g) was heated at 80 ◦C under solvent-
free conditions. The reaction process was monitored by thin layer
chromatography (TLC). After completion of the reaction, the reac-
tion mixture was cooled to room temperature and ethyl acetate
(5 mL) was added. The catalyst was removed by using a magnet
and washed with ethyl acetate. The combined organic layers were
dried over anhydrous MgSO4, and the solvent was evaporated
under reduced pressure. The pure product was obtained by column
chromatography on silica gel using hexane/ethyl acetate as eluent.
alytical X’Pert Pro X-ray diffractometer. Surface morphology and
particle size were studied using a Hitachi S-4800 SEM instrument.
Transmission electron microscope (TEM) images was obtained
using Hitachi H-7650 microscope at 80 kV. Elemental composi-
tions were determined with a Hitachi S-4800 scanning electron
microscope equipped with an INCA 350 energy dispersive spec-
trometer (SEM–EDS) presenting a 133 eV resolution at 5.9 keV. The
ICP-MS analyses were carried out with an X series 2 spectrome-
ter. Melting points were determined using an X-4 apparatus and
are uncorrected. FT-IR spectra were obtained with potassium bro-
mide pellets or as liquid films on potassium bromide pellets in the
3. Some selected spectral data of the products
3.1. N-benzyl-acetamide (3a)
range 400–4000 cm−1 with a Bruker-TENSOR 27 spectrometer. 1
H
NMR (500 MHz) and 13C NMR (125 MHz) spectra were recorded on
a Bruker DRX-500 spectrometer using CDCl3 as the solvent with
TMS as internal standard. Elemental analyses were performed by
using a Vario EL III CHNOS elemental analyzer.
White solid, mp: 41–42 ◦C; IR (KBr): 3293, 1643, 1555, 750,
694 cm−1
;
1H NMR (CDCl3, 500 MHz) ı 2.03 (s, 3H), 4.44 (d,
J = 5.5 Hz, 2H), 5.72 (s, 1H), 7.28–7.29 (m, 3H), 7.33 (d, J = 7.0 Hz, 2H)
ppm; 13C NMR (CDCl3, 125 MHz) ı 23.3, 30.9, 43.8, 127.6, 127.9,
128.7, 138.2 ppm. Anal. Calcd for C9H11NO: C, 72.46; H, 7.43; N,
9.39. Found: C, 72.39; H, 7.40; N, 9.40; ESI–MS: m/z = 150 (M+1)+.
2.2. Preparation of magnetic CoFe2O4 nanoparticle immobilized
N-propyl diethylenetriamine sulfamic acid
(CoFe2O4@SiO2–PDTSA)
3.2. N-(2-methylbenzyl)-acetamide (3b)
CoFe2O4 nanoparticles were synthesized according to a pre-
viously reported procedure [43]. 2.70 g of FeCl3·6H2O and 1.19 g
of CoCl2·6H2O were dissolved in 50 mL deionized water. 25 mL
of NaOH (3 mol/L) solution was added under vigorous stirring.
The reaction mixture was then continually stirred under refluxing
condition for 1 h. The reaction mixture was cooled to room temper-
ature. The solid product was separated by an external magnet and
washed with ethanol, then dried under vacuum at 50 ◦C for 24 h.
Coating of a layer of silica on the surface of the CoFe2O4 NPs was
achieved by adding distilled water (80 mL) to purified CoFe2O4 NPs
(1 g) which were then heated for 1 h at 40 ◦C. Then concentrated
ammonia solution (1.5 mL) was added and the resulting mixture
was stirred at 40 ◦C for 30 min. Subsequently, tetraethyl orthosili-
cate (TEOS, 1.0 mL) was charged to the reaction vessel and the
mixture was continuously stirred for 24 h. After cooling the solution
to room temperature, the silica-coated NPs were collected using a
permanent magnet and washed three times with ethanol, diethyl
ether, then dried at 100 ◦C in a vacuum for 24 h.
White solid, mp: 72–73 ◦C; IR (KBr): 3295, 1640, 1549,
743 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.02 (s, 3H), 2.33 (s, 3H),
;
4.44 (d, J = 5.0 Hz, 2H), 5.54 (s, 1H), 7.18–7.23 (m, 4H) ppm; 13C NMR
(CDCl3, 125 MHz) ı 19.0, 23.2, 41.9, 126.2, 127.8, 128.6, 130.6, 135.8,
136.5, 169.8 ppm. Anal. Calcd for C10H13NO: C, 73.59; H, 8.03; N,
8.58. Found: C, 73.49; H, 8.09; N, 8.66; ESI–MS: m/z = 164 (M+1)+.
3.3. N-(4-methylbenzyl)-acetamide (3c)
White solid, mp: 108–109 ◦C; IR (KBr): 3289, 1647, 1555,
804 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.02 (s, 3H), 2.34 (s, 3H),
;
4.39 (d, J = 6.0 Hz, 2H), 5.67 (s, 1H), 7.15 (d, J = 8.0 Hz, 2H), 7.18 (d,
J = 8.0 Hz, 2H) ppm; 13C NMR (CDCl3, 125 MHz) ı 21.1, 23.3, 43.5,
127.9, 129.4, 135.2, 137.3, 169.8 ppm. Anal. Calcd for C10H13NO: C,
73.59; H, 8.03; N, 8.58. Found: C, 73.48; H, 8.15; N, 8.71; ESI–MS:
m/z = 164 (M+1)+.
For the preparation of diamino-functionalized NPs, the obtained
CoFe2O4@SiO2 (1 g) was added to the solution of N-(2-amino-
ethyl)-(3-aminopropyl)triethoxysilane (AEAPTS, 2 mmol) in dry
toluene (20 mL) and the mixture was refluxed for 20 h. The
diaminated-CoFe2O4@SiO2 were separated by a permanent mag-
net, washed with double-distilled water and anhydrous ethanol,
and dried at 100 ◦C for 5 h to give diamino-functionalized NPs
(CoFe2O4@SiO2–DA).
3.4. N-benzhydryl-acetamide (3d)
White solid, mp: 151–152 ◦C; IR (KBr): 3257, 3049, 1647,
1545 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.07 (s, 3H), 6.07 (s, 1H),
;
6.25 (d, J = 8.0 Hz, 1H), 7.22–7.35 (m, 10H) ppm; 13C NMR (CDCl3,
125 MHz) ı 23.3, 57.0, 127.5, 128.7, 141.6, 169.2 ppm. Anal. Calcd
for C15H15NO: C, 79.97; H, 6.71; N, 6.22. Found: C, 79.83; H, 6.69;
N, 6.17; ESI–MS: m/z = 226 (M+1)+.
N-propyl-ethylene-diamine sulfamic acid on CoFe2O4
(CoFe2O4@SiO2–DASA) was prepared by the reaction of
CoFe2O4@SiO2–DA and chlorosulfonic acid. Typically, a mixture
of CoFe2O4@SiO2–DA (0.5 g) was suspended in dichloromethane
(5 mL) in a 100 mL round bottom flask equipped with a gas outlet
tube and a dropping funnel containing a solution of chlorosulfonic
3.5. N-(1,1-dimethyl-2-phenyl-ethyl)-acetamide (3e)
White solid, mp: 82–83 ◦C; IR (KBr): 3330, 3025, 1673 cm−1 1H
;
NMR (CDCl3, 500 MHz) ı 1.33 (s, 6H), 1.91 (s, 3H), 3.05 (s, 2H), 5.03
(s, 1H), 7.13–7.30 (m, 5H) ppm; 13C NMR (CDCl3, 125 MHz) ı 24.6,

260
X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
27.4, 44.5, 54.0, 126.3, 128.0, 130.5, 138.1, 169.8 ppm. Anal. Calcd
for C12H17NO: C, 75.35; H, 8.96; N, 7.32. Found: C, 75.41; H, 8.87;
N, 7.23; ESI–MS: m/z = 192 (M+1)+.
3.12. N-benzhydryl-2,2-diphenyl-acetamide (3l)
White solid, mp: 202–204 ◦C; IR (KBr): 3254, 3055, 1649,
1543, 696 cm−1 1H NMR (CDCl3, 500 MHz) ı 4.99 (s, 1H), 6.19
;
(d, J = 8.5 Hz, 1H), 6.31 (d, J = 8.0 Hz, 1H), 7.10 (d, J = 7.0 Hz, 4H),
7.24–7.25 (m, 6H), 7.26–7.33 (m, 10H) ppm; 13C NMR (CDCl3,
125 MHz) ı 57.1, 59.1, 127.3, 127.4, 127.5, 128.6, 128.8, 128.9, 139.3,
141.4, 170.9 ppm. Anal. Calcd for C27H23NO: C, 85.91; H, 6.14; N,
3.71. Found: C, 85.79; H, 6.25; N, 3.63; ESI–MS: m/z = 378 (M+1)+.
3.6. N-trityl-acetamide (3f)
White solid, mp: 219–221 ◦C; IR (KBr): 3242, 3023, 1655,
1526 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.09 (s, 3H), 6.58 (s, 1H),
;
7.20–7.31 (m, 15H) ppm; 13C NMR (CDCl3, 125 MHz) ı 24.7, 70.6,
127.1, 128.0, 128.7, 144.7, 169.1 ppm. Anal. Calcd for C21H19NO: C,
83.69; H, 6.35; N, 4.65. Found: C, 83.78; H, 6.38; N, 4.78; ESI–MS:
m/z = 302 (M+1)+.
3.13. N-benzhydryl-1-naphthamide (3m)
White solid, mp: 161–163 ◦C; IR (KBr): 3295, 1636, 1528, 1495,
3.7. N-(3-phenyl-allyl)-acetamide (3g)
772, 694 cm−1 1H NMR (CDCl3, 500 MHz) ı 6.57–6.61 (m, 2H),
;
7.30–7.33 (m, 2H), 7.35–7.40 (m, 8H), 7.47 (t, J = 7.5 Hz, 1H),
7.53–7.54 (m, 2H), 7.67 (d, J = 7.0 Hz, 1H), 7.86–7.88 (m, 1H),
7.93 (d, J = 8.0 Hz, 1H), 8.30–8.31 (m, 1H) ppm; 13C NMR (CDCl3,
125 MHz) ı 57.4, 124.7, 124.9, 125.5, 126.5, 127.2, 127.5, 127.6,
128.3, 128.8, 130.3, 130.8, 133.7, 134.2, 141.5, 168.6 ppm. Anal.
Calcd for C15H14FNO: C, 85.43; H, 5.68; N, 4.15. Found: C, 85.56;
H, 5.71; N, 4.27; ESI–MS: m/z = 338 (M+1)+.
White solid, mp: 71–72 ◦C; IR (KBr): 3283, 3092, 1728, 1643,
964 cm−1; 1H NMR (CDCl3, 500 MHz) ı 2.03 (s, 3H), 4.04 (t, J = 6.0 Hz,
2H), 5.60 (s, 1H), 6.19 (dt, J = 16.0, 6.0 Hz, 1H), 6.53 (d, J = 16.0 Hz,
1H), 7.23 (d, J = 7.5 Hz, 1H), 7.31 (t, J = 7.5 Hz, 2H), 7.35 (d, J = 7.5 Hz,
2H) ppm; 13C NMR (CDCl3, 125 MHz) ı 23.3, 41.7, 125.5, 126.4,
127.8, 128.6, 132.3, 136.5, 169.9 ppm. Anal. Calcd for C11H13NO:
C, 75.40; H, 7.48; N, 7.99. Found: C, 75.41; H, 7.40; N, 8.00; ESI–MS:
m/z = 176 (M+1)+.
3.14. N-benzyl-2-(4-chloro-phenyl)-acetamide (3o)
3.8. N-benzhydryl-4-fluoro-benzamide (3h)
White solid, mp: 148–150 ◦C; IR (KBr): 3281, 1643, 1541, 1493,
1086, 743, 692 cm−1 1H NMR (CDCl3, 500 MHz) ı 3.58 (s, 2H), 4.42
;
White solid, mp: 217–218 ◦C; IR (KBr): 3295, 1641, 1503,
(d, J = 5.5 Hz, 2H), 5.66 (s, 1H), 7.21 (t, J = 6.5 Hz, 4H), 7.28 (s, 1H),
7.31 (d, J = 5.5 Hz, 2H), 7.32 (d, J = 6.0 Hz, 2H) ppm; 13C NMR (CDCl3,
125 MHz) ı 43.1, 43.7, 127.5, 127.6, 128.7, 129.2, 130.7, 133.2, 133.4,
138.0, 170.2 ppm. Anal. Calcd for C15H14ClNO: C, 69.36; H, 5.43; N,
5.39. Found: C, 69.33; H, 5.39; N, 5.40; ESI–MS: m/z = 261 (M+1)+.
696 cm−1 1H NMR (CDCl3, 500 MHz) ı 6.44 (d, J = 7.5 Hz, 1H), 6.62
;
(d, J = 7.5 Hz, 1H), 7.12 (t, J = 8.5 Hz, 2H), 7.29–7.31 (m, 6H), 7.35 (t,
J = 7.0 Hz, 4H), 7.82–7.85 (m, 2H) ppm; 13C NMR (CDCl3, 125 MHz)
2
ı 30.9, 115.7 (d, JCF = 21.8 Hz), 127.5, 127.7, 128.8, 129.4 (d,
3JCF = 8.9 Hz), 130.4 (d, 4JCF = 3.4 Hz), 141.3, 164.7 (d, 1JCF = 197.4 Hz),
165.9 ppm. Anal. Calcd for C20H16FNO: C, 78.67; H, 5.28; N, 4.59.
Found: C, 78.55; H, 5.30; N, 5.50; ESI–MS: m/z = 306 (M+1)+.
3.15. 2-(4-Chlorophenyl)-N-(2-methylbenzyl)acetamide (3p)
White solid, mp: 135–138 ◦C; IR (KBr): 3306, 1643, 1557, 1491,
1256, 1015, 804, 750 cm−1; 1H NMR (CDCl3, 500 MHz) ı 2.25 (s, 3H),
3.57 (s, 2H), 4.42 (d, J = 5.5 Hz, 2H), 5.49 (s, 1H), 7.12 (t, J = 7.0 Hz, 1H),
7.16 (d, J = 6.0 Hz, 2H), 7.19 (d, J = 7.0 Hz, 1H), 7.22 (d, J = 8.0 Hz, 2H),
7.32 (d, J = 8.0 Hz, 2H) ppm; 13C NMR (CDCl3, 125 MHz) ı 19.0, 42.0,
43.1, 126.2, 127.9, 128.3, 129.2, 130.6, 130.7, 133.2, 133.4, 135.5,
136.4, 170.0 ppm. Anal. Calcd for C16H16ClNO: C, 70.20; H, 5.89; N,
5.12. Found: C, 70.19; H, 5.77; N, 5.10; ESI–MS: m/z = 275 (M+1)+.
3.9. N-benzhydryl-2-(4-chloro-phenyl)-acetamide (3i)
White solid, mp: 175–177 ◦C; IR (KBr): 3325, 3026, 1632, 1530,
698 cm−1
;
1H NMR (CDCl3, 500 MHz) ı 3.61 (s, 2H), 5.97 (d,
J = 8.0 Hz, 1H), 6.24 (d, J = 8.0 Hz, 1H), 7.11 (d, J = 7.5 Hz, 4H), 7.22 (d,
J = 8.5 Hz, 2H), 7.25–7.33 (m, 8H) ppm; 13C NMR (CDCl3, 125 MHz)
ı 43.1, 57.0, 127.3, 127.6, 128.7, 129.1, 130.7, 133.2, 133.4, 141.2,
169.4 ppm. Anal. Calcd for C21H18ClNO: C, 75.11; H, 5.40; N, 4.17.
Found: C, 75.09; H, 5.41; N, 4.13; ESI–MS: m/z = 337 (M+1)+.
3.16. 2-(4-Chlorophenyl)-N-(4-methylbenzyl)acetamide (3q)
3.10. N-benzhydryl-4-bromo-benzamide (3j)
White solid, mp: 177–179 ◦C; IR (KBr): 3287, 1640, 1535,
White solid, mp: 211–212 ◦C; IR (KBr): 3360, 3318, 3177, 1643,
802 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.33 (s, 3H), 3.57 (s, 2H),
;
1526, 845 cm−1 1H NMR (CDCl3, 500 MHz) ı 6.43 (d, J = 7.5 Hz,
;
4.37 (d, J = 5.5 Hz, 2H), 5.61 (s, 1H), 7.09 (d, J = 8.0 Hz, 2H), 7.12 (d,
1H), 6.67 (d, J = 7.5 Hz, 1H), 7.28–7.35 (m, 8H), 7.56–7.60 (m, 3H),
7.68–7.70 (m, 3H) ppm; 13C NMR (CDCl3, 125 MHz) ı 57.6, 127.5,
127.7, 128.7, 128.8, 129.0, 131.9, 133.0, 141.2, 165.7 ppm. Anal.
Calcd for C20H16BrNO: C, 65.59; H, 4.40; N, 3.82. Found: C, 65.41;
H, 4.47; N, 3.89; ESI–MS: m/z = 367 (M+1)+.
J = 8.0 Hz, 2H), 7.21 (d, J = 8.5 Hz, 2H), 7.31 (d, J = 8.5 Hz, 2H) ppm; 13
C
NMR (CDCl3, 125 MHz) ı 21.1, 43.1, 43.5, 127.7, 129.1, 129.4, 130.7,
133.2, 133.3, 134.9, 137.3, 170.2 ppm. Anal. Calcd for C16H16ClNO:
C, 70.20; H, 5.89; N, 5.12. Found: C, 70.09; H, 5.79; N, 5.15; ESI–MS:
m/z = 275 (M+1)+.
3.11. N-benzhydryl-4-chloromethyl-benzamide (3k)
3.17. 2-(4-Chlorophenyl)-N-tritylacetamide (3r)
White solid, mp: 210–212 ◦C; IR (KBr): 3266, 1630, 1533, 1505,
698 cm−1
;
1H NMR (CDCl3, 500 MHz) ı 4.61 (s, 2H), 6.45 (d,
White solid, mp: 106–107 ◦C; IR (KBr): 3252, 1647, 1533, 1491,
J = 8.0 Hz, 1H), 6.66 (d, J = 7.5 Hz, 1H), 7.29–7.31 (m, 6H), 7.34–7.37
(m, 4H), 7.46 (d, J = 8.5 Hz, 2H), 7.82 (d, J = 8.5 Hz, 2H) ppm; 13C
NMR (CDCl3, 125 MHz) ı 45.4, 57.5, 127.4, 127.5, 127.7, 127.9,
128.8, 134.2, 141.1, 141.3, 165.9 ppm. Anal. Calcd for C21H18ClNO:
C, 75.11; H, 5.40; N, 4.17. Found: C, 75.10; H, 5.39; N, 4.15; ESI–MS:
m/z = 337 (M+1)+.
1089, 696 cm−1 1H NMR (CDCl3, 500 MHz) ı 3.59 (s, 2H), 6.52
;
(s, 1H), 7.08–7.10 (m, 6H), 7.20–7.26 (m, 11H), 7.32 (d, J = 8.0 Hz,
2H) ppm; 13C NMR (CDCl3, 125 MHz) ı 44.4, 70.5, 127.1, 128.0,
128.5, 129.2, 130.6, 133.3, 133.5, 144.4, 169.1 ppm. Anal. Calcd for
C
27H22ClNO: C, 78.73; H, 5.38; N, 3.40. Found: C, 78.70; H, 5.40; N,
4.37; ESI–MS: m/z = 413 (M+1)+.

X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
261
3.18. N-benzyl-4-chloromethyl-benzamide (3s)
White solid, mp: 142–145 ◦C; IR (KBr): 3316, 1641, 1551, 1452,
727, 687 cm−1 1H NMR (CDCl3, 500 MHz) ı 4.61 (s, 2H), 4.66 (d,
;
J = 6.0 Hz, 2H), 6.36 (s, 1H), 7.29–7.33 (m, 1H), 7.34–7.39 (m, 4H),
7.46 (d, J = 8.0 Hz, 2H), 7.79 (d, J = 8.0 Hz, 2H) ppm; 13C NMR (CDCl3,
125 MHz) ı 44.2, 45.4, 127.4, 127.7, 128.0, 128.8, 128.9, 134.4, 138.0,
140.9, 166.7 ppm. Anal. Calcd for C15H14ClNO: C, 69.36; H, 5.43; N,
5.39. Found: C, 69.46; H, 5.40; N, 5.37; ESI–MS: m/z = 413 (M+1)+.
3.19. 4-Chloromethyl-N-(2-methyl-benzyl)-benzamide (3t)
White solid, mp: 127–130 ◦C; IR (KBr): 3291, 1628, 1541, 1285,
760, 677 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.38 (s, 3H), 4.61 (s,
;
2H), 4.65 (d, J = 5.5 Hz, 2H), 6.19 (s, 1H), 7.21–7.24 (m, 3H), 4.65 (d,
J = 5.5 Hz, 2H), 7.30 (d, J = 7.0 Hz, 1H), 7.78 (d, J = 8.0 Hz, 2H) ppm;
13C NMR (CDCl3, 125 MHz) ı 19.1, 42.4, 45.4, 126.3, 127.4, 128.0,
128.8, 130.7, 134.3, 135.6, 136.7, 140.9, 166.6 ppm. Anal. Calcd for
Scheme 2. Synthesis of CoFe2O4@SiO2–DASA.
C
16H16ClNO: C, 70.20; H, 5.89; N, 5.12. Found: C, 70.25; H, 5.79; N,
6.22; N, 5.09. Found: C, 82.70; H, 6.10; N, 5.17; ESI–MS: m/z = 276
5.16; ESI–MS: m/z = 275 (M+1)+.
(M+1)+.
3.20. 4-Chloromethyl-N-(4-methyl-benzyl)-benzamide (3u)
3.24. N-bornyl-2-phenylacetamide (3z)
White solid, mp: 155–156 ◦C; IR (KBr): 3337, 1641, 1541,
White solid, mp: 141–142 ◦C; IR (KBr): 3335, 2957, 1630, 1528,
685 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.35 (s, 3H), 4.60 (s, 2H),
;
1287, 718 cm−1 1H NMR (CDCl3, 500 MHz) ı 0.88 (s, 3H), 0.92 (s,
;
4.61 (s, 2H), 6.35 (s, 1H), 7.17 (d, J = 8.0 Hz, 2H), 7.25 (d, J = 8.0 Hz, 2H),
7.45 (d, J = 8.0 Hz, 2H), 7.78 (d, J = 8.0 Hz, 2H) ppm; 13C NMR (CDCl3,
125 MHz) ı 21.1, 44.0, 45.4, 127.4, 128.0, 128.7, 129.5, 134.4, 135.0,
137.5, 140.9, 166.7 ppm. Anal. Calcd for C16H16ClNO: C, 70.20; H,
5.89; N, 5.12. Found: C, 70.11; H, 5.88; N, 5.18; ESI–MS: m/z = 275
(M+1)+.
3H), 1.01 (s, 3H), 1.19–1.24 (m, 1H), 1.35–1.40 (m, 1H), 1.59–1.81
(m, 4H), 1.95–1.99 (m, 1H), 4.09–4.14 (m, 1H), 6.05 (br s, 1H),
7.42–7.45 (m, 2H), 7.48–7.51 (m, 1H), 7.03–7.72 (m, 2H) ppm; 13
C
NMR (CDCl3, 125 MHz) ı 11.8, 20.3, 20.4, 27.1, 30.9, 35.9, 39.3, 45.0,
47.2, 48.8, 57.2, 126.7, 128.6, 131.3, 135.2, 166.7 ppm. Anal. Calcd
for C17H23NO: C, 79.33; H, 9.01; N, 5.44. Found: C, 79.35; H, 9.00;
N, 5.45; ESI–MS: m/z = 258 (M+1)+.
3.21. 4-Fluoro-N-(4-methyl-benzyl)-benzamide (3v)
3.25. 4-(Chloromethyl)-N-(1,7,7-trimethylbicyclo[2.2.1]heptan-
2-yl)benzamide
(3aa)
White solid, mp: 135–137 ◦C; IR (KBr): 3296, 2924, 1638, 1505,
1290, 1234, 850 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.35 (s, 3H),
;
4.59 (d, J = 5.5 Hz, 2H), 6.31 (s, 1H), 7.10 (d, J = 8.5 Hz, 2H), 7.17 (d,
J = 8.0 Hz, 2H), 7.24 (d, J = 8.0 Hz, 2H), 7.77–7.80 (m, 2H) ppm; 13C
NMR (CDCl3, 125 MHz) ı 21.1, 44.0, 115.6 (d, 2JCF = 21.8 Hz), 128.0,
129.3 (d, 3JCF = 8.9 Hz), 130.8 (d, 4JCF = 27.1 Hz), 135.0, 137.4, 164.7
(d, 1JCF = 250.6 Hz), 166.3 ppm. Anal. Calcd for C15H14FNO: C, 74.06;
H, 5.80; N, 5.76. Found: C, 74.00; H, 5.91; N, 5.77; ESI–MS: m/z = 244
(M+1)+.
Oil; IR (KBr): 3327, 2953, 2359, 1653, 1271, 714 cm−1 1H
;
NMR (CDCl3, 500 MHz) ı 0.90 (s, 3H), 0.93 (s, 3H), 1.03 (s, 3H),
1.21–1.26 (m, 1H), 1.36–1.41 (m, 1H), 1.61–1.84 (m, 4H), 1.96–2.00
(m, 1H), 4.10–4.15 (m, 1H), 4.63 (s, 2H), 6.08 (d, J = 8.0 Hz, 1H),
7.47 (d, J = 8.0 Hz, 2H), 7.72 (d, J = 8.0 Hz, 2H) ppm; 13C NMR (CDCl3,
125 MHz) ı 11.8, 20.3, 20.4, 27.0, 29.7, 35.9, 39.2, 45.0, 45.4, 47.2,
48.9, 57.2, 127.2, 128.8, 135.2, 140.6, 166.2 ppm. Anal. Calcd for
3.22. 4-Bromo-N-(4-methyl-benzyl)-benzamide (3w)
White solid, mp: 168–170 ◦C; IR (KBr): 3323, 1640, 1549, 847,
660 cm−1
;
1H NMR (CDCl3, 500 MHz) ı 2.38 (s, 3H), 4.62 (d,
J = 5.5 Hz, 2H), 6.32 (s, 1H), 7.20 (d, J = 8.0 Hz, 2H), 7.27 (d, J = 8.0 Hz,
2H), 7.59 (d, J = 8.5 Hz, 2H), 7.67 (d, J = 8.5 Hz, 2H) ppm; 13C NMR
(CDCl3, 125 MHz) ı 21.1, 44.1, 126.2, 128.0, 128.6, 129.2, 129.5,
131.8, 134.9, 137.6, 166.3 ppm. Anal. Calcd for C15H14FNO: C, 59.23;
H, 4.64; N, 4.60. Found: C, 59.22; H, 4.69; N, 4.67; ESI–MS: m/z = 305
(M+1)+.
3.23. Naphthalene-1-carboxylic acid 4-methyl-benzylamide (3x)
White solid, mp: 156–157 ◦C; IR (KBr): 3269, 1634, 1533, 1516,
1294, 775 cm−1 1H NMR (CDCl3, 500 MHz) ı 2.38 (s, 3H), 4.73 (d,
;
J = 5.5 Hz, 2H), 6.25 (s, 1H), 7.21 (d, J = 8.0 Hz, 2H), 7.33 (d, J = 8.0 Hz,
2H), 7.47 (t, J = 7.0 Hz, 1H), 7.54–7.60 (m, 2H), 7.65 (d, J = 7.0 Hz,
1H), 7.89 (d, J = 7.5 Hz, 1H), 7.94 (d, J = 8.5 Hz, 1H), 8.38 (d, J = 8.0 Hz,
1H) ppm; 13C NMR (CDCl3, 125 MHz) ı 21.1, 43.9, 124.7, 124.9,
125.5, 126.5, 127.2, 127.9, 128.3, 129.2, 129.5, 130.2, 130.7, 133.7,
135.1, 137.4, 169.3 ppm. Anal. Calcd for C15H14FNO: C, 82.88; H,
Fig. 1. XRD pattern of CoFe2O4@SiO2–DASA.

262
X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
Fig. 2. SEM images of CoFe2O4@SiO2–DASA: (left) “fresh” and (right) “recovered”.
C18H24ClNO: C, 70.69; H, 7.91; N, 4.58. Found: C, 70.70; H, 7.90; N,
4.60; ESI–MS: m/z = 306 (M+1)+.
4. Results and discussion
4.1. Synthesis and characterization of CoFe2O4@SiO2–DASA
The details of the supported catalyst preparation procedure
are presented in Scheme 2. The magnetic core CoFe2O4 has
been synthesized by a chemical co-precipitation technique using
FeCl3·6H2O and CoCl2·6H2O as precursors according to a previ-
ously reported procedure [43]. After being coated by a layer of
silica through a sol–gel process, particle surfaces were further
functionalized with commercially available (N-(2-aminoethyl)-
3-aminopropyl)tris-(2-ethoxy)silane (DTPS) through the siloxane
linkage. Finally, the reaction of amino groups with chlorosul-
fonic acid led to sulphamic acid-functionalized magnetic CoFe2O4
nanoparticles (CoFe2O4@SiO2–DASA). The content of sulfonic acid
was determined by acid–base titration as 3.98 mmol/g. Also, the pH
of this solid sulfamic acid (10%, w/v) was measured using pH meter.
At first 0.5 g solid sulfamic acid was dispersed in 5 mL distilled
water by ultrasonic bath for 1 h, then measured and found to be
approximately about 0.44.
Fig. 3. TEM images of CoFe2O4@SiO2–DASA.
4.1.1. XRD analysis
The Fe O stretching vibration near 581 cm−1, O H stretching
vibration near 3434 cm−1 and O H deformed vibration near
1625 cm−1 were observed for both in Fig. 4(a) and (b). The signifi-
cant features observed for Fig. 4(b) are the appearance of the peaks
The XRD pattern of the sample is shown in Fig. 1. As seen in Fig. 1,
CoFe2O4@SiO2–DASA displays seven characteristic peaks at the 2ꢀ
values of 18.6, 30.6, 36.0, 43.8, 54.2, 57.9 and 63.5, which could be
attributed for the (1 1 1), (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and
(4 4 0) reflections, respectively. The positions and relative intensi-
ties of all diffraction peaks matched well with those from the cubic
reverse spinel phase of CoFe2O4 (JCPDS 221086) [16], suggesting
that the surface modification of MNPs did not significantly affect the
phase composition of CoFe2O4. A weak broad band (2ꢀ = 21–23◦)
appeared in functionalized magnetic pattern which be assigned to
the amorphous silane formed around the magnetic cores.
at 1002 cm−1 (Si O stretching) and at 2874 cm−1
( CH2 stretch-
ing). Several peaks at 650, 1091, 1159, 3495 cm−1 can be attributed
4.1.2. TEM, SEM and EDX elemental analysis
The TEM and SEM images of the synthesized CoFe2O4@SiO2–
DASA are shown in Figs. 2 and 3. These images confirmed
the formation of single-phase CoFe2O4 nanoparticles, with
spherical morphology. The average nanoparticle diameter of
CoFe2O4@SiO2–DASA was estimated to be ca. 25–30 nm based on
the TEM image, which is also in accordance with the result calcu-
lated by the Scherrer formula. The presence of C, O, Fe, Co, Si and S
atoms was observed in the EDX spectrum (Fig. 4).
4.1.3. FT-IR analysis
Fig. 5 shows the Fourier transform infrared (FTIR) spectra of both
the unfunctionalized and functionalized magnetic nanoparticles.
Fig. 4. EDS spectrum of CoFe2O4@SiO2–DASA.

X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
263
Table 1
Screening of reaction conditions for the Ritter reactiona.
a
Entry
Catalyst (mg)
Temperature (◦C)
Time (h)
Yield (%)
1
2
3
4
5
6
7
8
9
10
No
10
10
10
10
10
10
5
80
25
40
60
80
90
100
80
80
80
6
4
4
4
4
4
4
4
4
4
Trace
Trace
56
73
90
90
90
70
4000
3500
3000
2500
2000
1500
1000
500
15
10
90
Wavenumbers(cm-1)
91b
a
Experimental conditions: diphenyl methanol (1 mmol), acetonitrile (1 mmol).
10 mmol Scale.
Fig. 5. IR spectra of CoFe2O4@SiO2 (a) and CoFe2O4@SiO2–DASA (b).
b
to the characteristic absorption of sulfonic acid groups. The peak
at 650 cm−1 was associated with the S O stretching vibration, and
the broad peak in the range of 3000–3600 cm−1 was originatedfrom
the stretching of O H bond in the sulfonic acid groups.
(Table 1, entry 5). To further improve the efficiency of the reac-
tion, the amount of catalyst and temperature were also examined.
However, none of them could produce a higher yield, even at higher
temperature.
We also examined the feasibility of the present method for
large-scale synthesis with diphenyl methanol with acetonitrile. The
reaction was found to proceed smoothly affording the desired prod-
uct in 91% yield within 4 h, almost similarly in all respects with
1 mmol scale (Table 1, entry 9).
After optimizing of the reaction conditions, a broad range of
structurally diverse alcohols and nitriles was further evaluated
and the results are depicted in Table 1. Initially, the reaction of
different alcohols with acetonitrile was studied. The results demon-
strated that benzylic, and secondary alcohols as well as tertiary
alcohol are all good substrates in this reaction, and the correspond-
ing amides are formed in good to excellent yields (Table 2, entries
4.2. Catalytic activity of CoFe2O4@SiO2–DASA
We have chosen the Ritter reaction as the model reaction to
evaluate the catalytic performance of CoFe2O4@SiO2–DASA, using
the coupling of diphenyl methanol with acetonitrile as the standard
reaction under solvent-free conditions. The results of these exper-
iments are summarized in Table 1. Only a trace amount of the
desired product was observed on TLC plate in the absence of
the catalyst after 6 h at 80 ◦C (Table 1, entry 1). To our delight,
the reaction could proceed smoothly in the presence of 10 mg
CoFe2O4@SiO2–DASA, resulting in a desired product in 90% yield
Table 2
Ritter reaction catalyzed by CoFe2O4@SiO2–DASAa.
Entry
Alcohol
Nitrile
Product
Time (h)
Yield (%)b
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
PhCH2OH
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
4-FC6H4CN
4-ClC6H4CH2CN
4-BrC6H4CN
4-ClCH2C6H4CN
Ph2CHCN
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
4
4
4
4
4
4
4
4
3
4
3
4
4
4
4
4
4
4
3
3
3
4
4
4
4
4
4
83
86
87
90
85
83
80
88
86
83
89
86
87
91
83
85
86
80
96
90
95
83
81
79
91
90
87
2-MeC6H4CH2OH
4-MeC6H4CH2OH
Ph2CHOH
PhCH2CMe2OH
Ph3COH
PhCH CHCH2OH
Ph2CHOH
Ph2CHOH
Ph2CHOH
Ph2CHOH
Ph2CHOH
Ph2CHOH
PhCH2OH
PhCH2OH
2-MeC6H4CH2OH
4-MeC6H4CH2OH
Ph3COH
1-Naphthonitrile
C6H5CN
4-ClC6H4CH2CN
4-ClC6H4CH2CN
4-ClC6H4CH2CN
4-ClC6H4CH2CN
4-ClCH2C6H4CN
4-ClCH2C6H4CN
4-ClCH2C6H4CN
4-FC6H4CN
4-BrC6H4CN
1-Naphthonitrile
C6H5CN
PhCH2OH
3s
3t
2-MeC6H4CH2OH
4-MeC6H4CH2OH
4-MeC6H4CH2OH
4-MeC6H4CH2OH
4-MeC6H4CH2OH
Cyclohexanol
Borneol
3u
3v
3w
3x
3y
3z
3aa
C6H5CN
4-ClCH2C6H4CN
Borneol
a
Reaction conditions: alcohol (1 mmol), nitrile (1 mmol), CoFe2O4@SiO2–DASA (0.27 g), 80 ◦C.
Isolated yield.
b

264
X.-N. Zhao et al. / Applied Catalysis A: General 482 (2014) 258–265
Table 3
Comparison of our results with previously reported methods.
Entry
Catalyst
Reaction conditions
Product
Time
Yield (%)
1
2
3
4
5
6
7
8
o-Benzenedisulfonimide (10 mol%)
2,4-Dinitrobenzenesulfonic acid (10 mol%)
FeCl3·6H2O (10 mol%)
Reflux
Reflux
5a
5a
5a
5a
5n
5a
5a
5a
5n
5n
5a
8 h
89 [31]
86 [32]
96 [34]
80 [36]
89 [37]
88 [38]
98 [39]
95 [41]
91 [42]
84 [44]
90 (this work)
15 h
0.5 h
5 h
2.5 h
6 h
15 min
5 h
8 h
H2O, 150 ◦
H2O, 110 ◦
C
C
I2 (20 mol%)
Ca(HSO4)2 (100 mol%)
Sulfated tungstate (20 wt%)
SBNPSA (0.1 g)
␥-Fe2O3@SiO2–HClO4 (0.1 g)
Silica sulfuric acid (20 mg)
Nanocat-Fe–OSO3H (0.1 g)
CoFe2O4@SiO2–DASA (0.1 g)
80 ◦
C
Solvent-free, 100 ◦
C
Solvent-free, 80 ◦
Solvent-free
C
9
10
11
Toluene, 90 ◦
C
Solvent-free, 90 ◦
Solvent-free, 80 ◦
C
C
4 h
4 h
100
of toxic or volatile solvents, higher yields, and facile recovery and
recyclability of the catalyst used.
90
80
70
60
50
40
30
20
10
0
Acknowledgment
0
We gratefully acknowledge that this research work was sup-
ported by the National Natural Science Foundation of China (Nos.
21272053 and 21072042).
1
2
3
4
5
6
Cycles
Fig. 6. Reusability of the catalyst.
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diamine-N-sulfamic acid catalyst and its application in Ritter reac-
tion between alcohols and nitriles. The method described herein
compares favorably with hitherto known methodologies, espe-
cially in terms of easy and green work-up procedures, absence

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