Facile and efficient preparation of nitriles through FeCl4–IL–SiO2-catalyzed direct oxidation of alcohols with hydrogen peroxide

Article abstract of DOI:10.1007/s13738-016-0974-z

Abstract: A series of silica-supported functionalized ionic liquids catalysts have been prepared and tested in the oxidative conversion of alcohols to nitriles with H₂O₂ as the oxidant. The features of this heterogeneous reaction system were studied by tuning various reaction parameters including catalyst selection, amount of the catalyst, and effect of solvents. Among the catalysts, FeCl₄–IL–SiO₂ exhibited the highest efficiency in direct oxidation of alcohols to nitriles under the optimized condition along with good recycle performance. Also, a possible catalytic mechanism is provided. Graphical abstract: [Figure not available: see fulltext.]

Full text of DOI:10.1007/s13738-016-0974-z

J IRAN CHEM SOC (2017) 14:233–243
DOI 10.1007/s13738-016-0974-z
ORIGINAL PAPER
Facile and efficient preparation of nitriles through FeCl4–
IL–SiO ‑catalyzed direct oxidation of alcohols with hydrogen
2
peroxide
Yu‑Lin Hu1,2 · Bing Tong Wang · Dong Fang1
1
Received: 2 April 2016 / Accepted: 9 September 2016 / Published online: 17 September 2016
©
Iranian Chemical Society 2016
Abstract A series of silica-supported functionalized ionic
liquids catalysts have been prepared and tested in the oxi-
dative conversion of alcohols to nitriles with H O as the
Keywords Supported ionic liquid · Silica gel · Oxidation
of alcohols · Nitriles · Heterogeneous catalysis
2
2
oxidant. The features of this heterogeneous reaction system
were studied by tuning various reaction parameters includ-
ing catalyst selection, amount of the catalyst, and effect
of solvents. Among the catalysts, FeCl –IL–SiO exhib-
ited the highest efficiency in direct oxidation of alcohols
to nitriles under the optimized condition along with good
recycle performance. Also, a possible catalytic mechanism
is provided.
Introduction
Nitriles are useful intermediates in organic synthesis for
the production of a variety of important substances such as
agrochemicals, pharmaceutical, polymers, and pigments [1,
2]. The usual methods for the nitriles synthesis comprise the
direct conversion of aldehydes, oxime ethers, thioamides,
carboxylic acids and their esters, dehydration of aldoximes
and amides, reduction of primary aliphatic nitro compounds,
and other methods [3–6]. However, these methods suffer
from the inherent problems of such as tedious workup pro-
cedures, lower yields, severe reaction conditions, and envi-
ronmental pollution. To overcome some of these economical
and environmental related problems, the direct conversion
of azides [7, 8], amines [9, 10], amides [11], oximes [12],
alcohols [13], and others [14–16] to nitriles has attracted
much attention in chemical industry in recent years, both
from economic and environmental standpoint. Among these
catalytic methods, the oxidative transformation of alco-
hols to nitriles could be a viable alternative and clean route
4
2
Graphical abstract
[13]. Moreover, this route will eliminate the additional step
involved in the preparation of imines, amides, and aldoxi-
mes. A number of catalytic oxidation processes based upon
the combination of transition metals or organocatalysts
using commercially available aqueous ammonia or its sur-
rogate have been developed for such a transformation [13,
*
Yu-Lin Hu
huyulin1982@163.com
1
College of Chemistry and Environmental Engineering,
Yancheng Teachers University, Yancheng 224002,
People’s Republic of China
17–23]. However, these procedures often require hazardous
reagents, harsh reaction conditions, and non-commercially
available materials. Thus, the development of mild, effi-
cient, and environmentally friendly procedures for nitriles
synthesis is still a challenging task.
2
College of Materials and Chemical Engineering, China
Three Gorges University, Yichang 443002,
People’s Republic of China
1
3

2
34
J IRAN CHEM SOC (2017) 14:233–243
Ionic liquids (ILs) are well-known reaction media/cata-
lysts, which possess favorable properties such as very low
vapor pressure, wide liquid temperature range, good ionic
conductivity, and excellent electrochemical properties.
[
24–27]. Examples of their application in the direct conver-
sion of alcohols to nitriles were seldom reported [28]. In
spite of high catalytic activity of these ILs presented, they
suffered from some problems, such as partially ILs wasted
and difficulty to separate and recycle. A useful approach to
overcome these limitations is the development of supported
functional ionic liquid catalytic system [29–35]. The sup-
ported IL system dispersed onto a high surface area sup-
port. The homogeneous catalytic reactions of ILs could
transfer into the heterogeneous systems which provide
attractive features such as gaining high catalyst efficiency
by using only smaller amounts of ILs, high system stability,
facilitating the catalyst recovery, and high reusability [35].
Based on the above summarizations, we attempt to design a
type of functionalized ionic liquids supported on silica gel
with different functional anion groups. The prepared mate-
Scheme 1 Catalytic synthesis of nitriles by oxidative conversion of
alcohols
CDCl as the solvent with tetramethylsilane (TMS) as an
3
internal standard. GC analyses were performed on a Shi-
madzu-14B gas chromatography equipped with HP-1 capil-
lary column (30 m, 0.25 mm, 0.25 mm). Elemental analy-
sis was performed on a Vario EL III instrument (Elmentar
Analysensysteme GmbH, Germany).
rials, anion-IL–SiO , exhibited good thermal and chemical
2
stability and were utilized as a new heterogeneous solid
catalyst in the direct oxidation of alcohols to nitriles with
H O as a terminal oxidant under mild reaction conditions
2
2
(
Scheme 1). As well as this, the reusability of the supported
Preparation of the supported ILs
ionic liquid was also investigated.
The preparation processes were according to known
process [31–35] and shown in Scheme 2. (1) Silica
pretreatment and activation: Silica gel (60 g) was acti-
vated by standing in hydrochloric acid solution (10 %,
600 mL) for 12 h at room temperature and then washed
thoroughly with distilled water. The sample was then
dried at 60 °C for 24 h. (2) Preparation of 1: A mixture
of imidazole (13.6 g, 0.2 mol), (3-chloropropyl) trieth-
oxysilane (48.2 g, 0.2 mol), and toluene (350 mL) was
added into a 1-L round flask connected to a reflux con-
denser, and the mixture was refluxed for 22 h under a
nitrogen atmosphere. Then, triethylamine (20.2 g,
0.2 mol) was added dropwise to the resulted mixture
at 50 °C and stirred for another 2 h under reflux con-
ditions. After the reaction, the slurry was filtrated and
the filter cake was washed with toluene (3 × 20 mL).
The combined toluene solution was removed under
reduced pressure to afford 1-(3-(triethoxysilyl)propyl)-
1H-imidazole 1 as a viscous liquid. (3) Preparation of
2: A mixture of 1 (27.2 g, 0.1 mol), (3-chloropropyl)
triethoxysilane (24.1 g, 0.1 mol), and toluene (80 mL)
Experimental
Apparatus and reagents
All the chemicals were from commercial sources without
any pretreatment. All reagents were of analytical grade.
Fourier transform infrared spectroscopy (FT-IR) spectra
were obtained on a Nicolet Nexus 470 Fourier transform
infrared spectrometer, using KBr pellets at room tempera-
ture. The powder X-ray diffraction (XRD) analysis was car-
ried out on a Rigaku Ultima IV diffractometer with high-
intensity Cu Ka radiation. Energy-dispersive X-ray analysis
(
EDX) was used to conduct the elemental analysis of the
supporting IL. Scanning electron microscopy studies were
conducted on a JSM-7500F scanning electron microscope
(
SEM). Thermogravimetric analysis (TGA) was carried out
by a Netzsch Thermoanalyzer STA 449 with a heating rate
of 10 °C/min under a nitrogen atmosphere. NMR spectra
were recorded on a Bruker 500-MHz spectrometer using
1
3

J IRAN CHEM SOC (2017) 14:233–243
235
Scheme 2 Preparation of the supporting ILs
was stirred vigorously in a 250-mL round flask under
a nitrogen atmosphere. After 12-h stirring under reflux
conditions, the solvent was evaporated under reduced
pressure to give intermediate 2 as a viscous white liquid.
24 h under reflux conditions. Then, the sample was fil-
trated and washed with dichloromethane (3 × 20 mL).
The as-prepared material was dried under vacuum at
80 °C to afford the supported ionic liquid FeCl –IL–
4
(
4) Preparation of 3: A mixture of 2 (25.8 g, 0.05 mol),
SiO (6, yellow powder) or CuCl –IL–SiO (7, yellow–
2
3
2
activated silica (40 g), and toluene (250 mL) was stirred
vigorously in a 500-mL round flask under a nitrogen
atmosphere. After 24-h stirring under reflux conditions,
the mixture was filtrated and washed with dichlorometh-
ane (3 × 20 mL), and dried under vacuum at 60 °C to
green powder).
General procedure for the catalytic oxidation
In a typical experiment, alcohol (10 mmol), aqueous
·
afford the supported ionic liquid Cl–IL–SiO 3 as a
NH H O (30 mmol), FeCl –IL–SiO (0.5 g), and CH CN
2
3
2
4
2
3
white powder. (5) Preparation of 4 and 5: 9.0 g Cl–IL–
(10 mL) were added to a round-bottomed flask. Then,
aqueous 30 % H O (21 mmol) was gradually added into
SiO was dispersed throughout 100 mL dichloromethane
2
2
2
and treated with 0.66 g NaBF or 1.1 g KPF ; then, the
the reactor at room temperature. The obtained mixture was
stirred at 30 °C for appropriate time (Table 4). The reaction
was monitored by TLC and GC. After completion of the
reaction, the catalyst was recovered by filtration. Evapora-
tion of the solvent under reduced pressure gave the crude
product. Further purification was achieved by flash column
chromatography on a silica gel (petroleum ether/ethyl ace-
tate, 5:1) to give the desired product. Fresh substrates were
then recharged to the recovered catalyst and then recycled
under identical reaction conditions.
4
6
mixture was refluxed for 24 h under nitrogen condition.
After cooled down to room temperature, the solid was
isolated by filtration and washed with dichloromethane/
distilled water (3 × 20 mL). The resulting material was
dried under vacuum at 80 °C to give the supported ionic
liquid BF –IL–SiO (4, gray powder) or PF –IL–SiO
4
2
6
2
(
5, yellow powder). (6) Preparation of 6 and 7: 10.0 g
Cl–IL–SiO was dispersed in 100 mL acetonitrile and
2
stirred vigorously with 3.0 g FeCl or 2.0 g CuCl for
3
2
1
3

2
36
J IRAN CHEM SOC (2017) 14:233–243
Spectroscopic data for selected products
4
‑Methoxybenzonitrile (Table 4, entry 3)
1
H NMR: δ = 2.78 (s, 3H, CH ), 7.21 (m, 2H, Ar–H), 7.56
3
(
m, 2H, Ar–H) ppm; Anal. Calcd for C H NO: C, 72.13;
8
7
H, 5.27; N, 10.48; O, 12.01. Found: C, 72.16; H, 5.30; N,
1
0.52; O, 12.02.
2
,4,6‑Trimethylbenzonitrile (Table 4, entry 4)
1
H NMR: δ = 2.31 (s, 3H, CH ), 2.43 (s, 6H, 2CH ), 7.16
3
3
(
m, 2H, Ar–H) ppm; Anal. Calcd for C H N: C, 82.68; H,
10 11
7
.61; N, 9.63. Found: C, 82.72; H, 7.64; N, 9.65.
4
‑Nitrobenzonitrile (Table 4, entry 6)
Fig. 1 FT-IR spectra of intermediate 1 (t1), intermediate 2 (t2), Cl–
IL–SiO2 (t3), BF4–IL–SiO2 (a), PF6–IL–SiO2 (b), FeCl4–IL–SiO2 (c),
and CuCl –IL–SiO (d)
1
H NMR: δ = 7.82 (m, 2H, Ar–H), 8.34 (m, 2H, Ar–H)
3
2
ppm; Anal. Calcd for C H N O : C, 56.73; H, 2.69; N,
7
4
2
2
1
2
8.88; O, 21.57. Found: C, 56.76; H, 2.72; N, 18.91; O,
1.60.
The surface morphology and chemical composition of the
supported ILs were studied by SEM (Fig. 2) and EDX (Fig. 3).
Figure 2f is the SEM image of silica gel, which is made up
of block structures with a size of several micrometers. Fig-
ure 2a–d is the SEM images of the supported ILs, BF4–
IL–SiO (Fig. 2a), PF –IL–SiO (Fig. 2b), FeCl –IL–SiO
Cinnamonitrile (Table 4, entry 10)
1
H NMR: δ = 5.84 (d, 1H, CH), 7.36 (d, 1H, CH), 7.41–
7
.52 (m, 5H, Ar–H) ppm; Anal. Calcd for C H N: C, 83.65;
9 7
2
6
2
4
2
H, 5.42; N, 10.81. Found: C, 83.69; H, 5.46; N, 10.84.
(Fig. 2c), and CuCl –IL–SiO (Fig. 2d); it clearly shows all
3 2
the supported IL particles were well defined and had distinct
size owing to the immobilization of the IL. The particle size
of the supported IL is smaller to that of silica gel, which dem-
onstrates that the particles of silica gel had a good mechanical
stability during the immobilization step. The change in the par-
ent structure of the silica to well-defined particles in supported
IL indicated that functionalized ILs had been immobilized on
the surface of the silica particles. The chemical composition of
the supported ILs was investigated by energy-dispersive X-ray
spectroscopy (EDX) (Fig. 3), which showed the presence of
the expected elements in its structure. X-ray diffraction analy-
sis (XRD) pattern of intermediates 2 and the supported ionic
liquids was studied in a domain of 5°–90° (Fig. 4). As shown
in Fig. 4, all of the catalysts had obvious characteristic peak at
2θ ≈ 22.8°, which was attributed to the amorphous nature of
Results and discussion
The structure of the supported ionic liquids was character-
ized by FT-IR, XRD, TG, EDX, and SEM analysis. The
FT-IR spectra of intermediates 1, 2, and the supported
ionic liquids are presented in Fig. 1. As shown in the fig-
ure, all ionic liquids exhibit absorptions at about 1072 and
−1
9
65 cm , which correspond to the stretching vibration
of Si–O–Si. Characteristic peaks at the positions of about
−
1
1
465, 1530, and 1650 cm correspond to C–H bending
vibrations, C=C, and C=N stretching vibrations of the
imidazolium ring, indicating that imidazole was success-
fully grafted on the surface of silica gel [36]. For a and b,
absorptions in the B–F (1045 cm ) and P–F (865 cm )
bands are observed, indicating the interaction between het-
−
1
−1
the SiO support [36]. The absence of obvious characteristic
2
peaks of anions of ILs in the XRD patterns suggests that these
anions units are well dispersed on the surface and in the chan-
eropoly acid anions and the SiO –IL support. The charac-
teristic peak at the position of 798 cm was attributed to
2
−
1
nels of the SiO ‐IL supports.
2
−1
the C–Cl (Fig. 1t3). Also, the peaks observed at 725 cm
The stability of intermediates 1, 2 and the supported ILs,
Cl–IL–SiO , BF –IL–SiO , PF –IL–SiO , FeCl –IL–SiO ,
−
1
(
Fig. 1c) and 570 cm (Fig. 1d) related to vibrational
2
4
2
6
2
4
2
modes of FeCl and CuCl , respectively.
and CuCl –IL–SiO , was determined by thermogravimetric
4
3
3
2
1
3

J IRAN CHEM SOC (2017) 14:233–243
237
Fig. 2 SEM images of BF –IL–SiO (a), PF –IL–SiO (b), FeCl –IL–SiO (c), CuCl –IL–SiO (d), five times recycled FeCl –IL–SiO (e), and
4
2
6
2
4
2
3
2
4
2
silica gel (f)
Fig. 3 EDX images of BF –IL–SiO (a), PF –IL–SiO (b), FeCl –IL–SiO (c), and CuCl –IL–SiO (d)
4
2
6
2
4
2
3
2
1
3

2
38
J IRAN CHEM SOC (2017) 14:233–243
Fig. 5 TG curves for intermediate 1 (t1), intermediate 2 (t2), Cl–IL–▸
SiO (t3), BF –IL–SiO (a), PF –IL–SiO (b), FeCl –IL–SiO (c),
2
4
2
6
2
4
2
and CuCl –IL–SiO (d)
3
2
The effect of various solvents on the yield of product
is given in Table 2. The reaction does not progress effec-
tively in toluene (Table 2, entry 3). The reaction in water,
toluene, dichloromethane, DMF, acetonitrile as well as sol-
vent-free conditions resulted in 53–78 % yield of product
(
Table 2, entries 1–6). The results show that CH CN is a
3
better solvent than the other solvents tested (Table 2, entry
). To investigate the effect of catalyst concentration, sys-
6
tematic studies were carried out in the presence of various
amounts of the catalyst in CH CN, affording benzonitrile
3
in 78–90 % isolated yields, respectively (Table 2, entries
2
, 7–9). Thus, the best yield is obtained in the presence of
just 0.5 g of FeCl –IL–SiO (Table 2, entry 9). The use of a
greater amount of catalyst does not improve the result to an
appreciable extent (Table 2, entry 10).
Fig. 4 Wide-angle XRD patterns of intermediate 2 (t2), Cl–IL–SiO2
t3), BF –IL–SiO2 (a), PF –IL–SiO (b), FeCl –IL–SiO (c), and
4
2
(
4
6
2
4
2
CuCl –IL–SiO (d)
3
2
The FeCl –IL–SiO was a heterogeneous catalyst, and it
4
2
can be easily recovered by filtration after the reaction. The
recovered catalyst was used again for the oxidative con-
version of benzyl alcohol to benzonitrile with H O under
analysis, and the TG analysis results are shown in Fig. 5.
In the TG curve, the observed weight loss was associated
with the loss of the organic components attached to the sur-
face, and the sample showed a total weight loss of ~76.4 %
2
2
the same reaction conditions, and the results are shown in
Fig. 6. As shown in Fig. 6, the catalytic activity decreases
slightly during the consecutive five runs, suggesting that
the catalyst could be typically recovered and reused for
subsequent reactions with no remarkable loss of activ-
ity. The recovered catalyst after five runs had no obvious
change in the morphology and size (Fig. 2e), referring to
the SEM image in comparison with fresh catalyst (Fig. 2c).
Furthermore, XRD result of the reused FeCl –IL–SiO
(Fig. 5t1), ~65.8 (Fig. 5t2), ~48.5 (Fig. 5t3), ~21.8 %
(Fig. 5a), 22.7 % (Fig. 5b), ~47.4 % (Fig. 5c), ~14.5 %
(Fig. 5d) on heating to 800 °C, respectively. The slight
weight loss before 260 °C is assignable to the desorption of
adsorbed water, suggesting a considerably high thermal sta-
bility up to 260 °C. The drastic weight loss in the tempera-
ture range 260–580 °C is attributed to the decomposition of
the organic moiety. From the curve depicted, one can see that
the supported ILs are thermally stable below about 260 °C.
The catalytic activities of the supported ILs were tested
in the oxidative conversion of benzyl alcohol to benzoni-
trile with H O as an oxidant, and the results are summa-
4
2
after five runs showed that the crystallinity of the mate-
rial could be maintained during the course of the reaction
(Fig. 7). These results indicate that the catalyst was stable
and could endure this reaction’s conditions.
2
2
To show the merit of FeCl –IL–SiO in comparison with
rized in Table 1. The supported ILs, such as BF –IL–SiO ,
4
2
4
2
other reported catalysts, we compared the results of the
oxidative conversion of benzyl alcohol to benzonitrile with
the previous reported in the literature. The data presented
in Table 3 show the promising features of this protocol in
terms of reaction rate, product yield, low catalyst loading,
and catalyst reusability when compared to other methods.
This catalyst showed milder reaction conditions and good
yield compared to the other catalysts.
PF –IL–SiO , FeCl –IL–SiO , and CuCl –IL–SiO , were
6
2
4
2
3
2
tested as catalyst in the reaction (Table 1, entries 1–4), and
it was observed that FeCl –IL–SiO demonstrated the best
4
2
performance in terms of reaction rate and yield (Table 1,
entry 3). The corresponding controlled experiments were
conducted with bare ILs, such as [bmim][MnCl ], [bmim]
3
[
FeCl ], [bmim][CuCl ], and [bmim][AlCl ] as catalysts
4 3 4
under the same conditions (Table 1, entries 5–8), and it was
showed that the target benzonitrile was formed in low yield,
The excellent results of FeCl –IL–SiO suggest the
4
2
reaction has a particular reaction mechanism. On the
basis of previous reports [17, 18] and the experiment
result, taking the oxidative conversion of benzyl alcohol
to benzonitrile as an example, a possible mechanism is
especially when [bmim][AlCl ] was used. Thus, based on
4
the results obtained, the supported IL catalyst FeCl –IL–
4
SiO is more efficient than the individual component in this
2
reaction.
1
3

J IRAN CHEM SOC (2017) 14:233–243
239
1
3

2
40
J IRAN CHEM SOC (2017) 14:233–243
Table 1 Oxidative conversion of benzyl alcohol to benzonitrile with
H O over various catalysts
2
2
Entry
Catalyst
Time (h)
Yield (%)a
1
2
3
4
5
6
7
8
BF –IL–SiO
4
4
3
3
5
5
5
8
65
53
90
81
61
74
68
13
4
2
PF –IL–SiO
6
2
FeCl –IL–SiO
4
2
CuCl –IL–SiO
3
2
[bmim][MnCl3]
[bmim][FeCl4]
[bmim][CuCl3]
[bmim][AlCl4]
The reactions were carried out with benzyl alcohol (10 mmol), 30 %
·
H O (21 mmol), NH H O (30 mmol), catalyst (0.5 g), and CH CN
2
2
3
2
3
(
10 mL) at 30 °C
a
Isolated yield
Fig. 6 Repeated reactions in the presence of the recycled FeCl –IL–
4
SiO2
Table 2 Optimization of the reaction conditions for oxidative con-
version of benzyl alcohol to benzonitrile
Entry Solvent
Catalyst
Amount
g)
Time (h) Yield (%)a
(
1
2
3
4
Solvent-
free
FeCl –IL– 0.2
SiO2
4
4
4
4
70
54
41
68
4
Water
FeCl –IL– 0.2
4
SiO2
Toluene
FeCl –IL– 0.2
4
SiO2
Dichlo-
rometh-
ane
FeCl –IL– 0.2
4
SiO2
5
6
7
8
9
1
DMF
FeCl –IL– 0.2
SiO2
4
4
3
3
3
3
73
78
85
88
90
89
4
Acetonitrile IL–SO H– 0.2
3
SiO2
Acetonitrile FeCl –IL– 0.3
4
SiO2
Fig. 7 XRD patterns of the fresh and reused FeCl –IL–SiO
4
2
Acetonitrile FeCl –IL– 0.4
4
SiO2
Acetonitrile FeCl –IL– 0.5
4
imine 4 through nucleophilic addition and intermolecular
dehydration. 4 is then dehydrogenated by H O oxidation
SiO2
2
2
0
Acetonitrile FeCl –IL– 0.6
4
under FeCl –IL–SiO catalysis eliminates H O, resulting in
4
2
2
SiO2
the energetically favorable product benzonitrile.
The reactions were carried out with benzyl alcohol (10 mmol), 30 %
Having established optimum conditions, a series of
nitriles were synthesized by reacting various phenyl hydra-
·
H O (21 mmol), NH H O (30 mmol), catalyst (FeCl –IL–SiO ), and
2
2
3
2
4
2
solvent (10 mL) at 30 °C
·
zines with H O /NH H O in order to show the broad scope
a
2
2
3
2
Isolated yield
and generality of this method (Table 4). It is clear that vari-
ous types of benzylic, allylic, and heterocyclic alcohols have
been successfully oxidized to the corresponding nitriles
in good to high yields (Table 4, entries 1–10), whereas
the aliphatic alcohols were less reactive, and the reactions
proposed (Scheme 3). At first, the substrate benzyl alcohol
is activated and oxidated by FeCl –IL–SiO to form benza-
4
2
ldehyde 1 which reacts with ammonia rapidly to produce
1
3

J IRAN CHEM SOC (2017) 14:233–243
241
Table 3 Comparison of the results obtained from the synthesis of benzonitrile in the presence of FeCl –IL–SiO with those obtained using other
4
2
catalysts
Entry
Catalyst
Conditions
Time (h)
Yield (%)a
References
1
2
3
4
5
6
CuI/bpy/TEMPO
PhI(OAc)2
O (1 atm), NH , CH CN, 55 °C
24
7
87
82
85
80
89
90
[17]
2
3
3
TEMPO, CH CN/H O, NH OAc, 25 °C
[18]
3
2
4
·
Cu(NO ) /TEMPO
O (1 atm), DMSO, NH H O, 80 °C
24
3
[19]
3
2
2
3
2
Cu(ClO ) ·6H O
DDQ, dichlorethen, TMSN 60 °C
[20]
4
2
2
3,
PS–BHA–Cu
O (1 atm), NH HCO , CH CN, K PO , 115 °C
16
3
[21]
2
4
2
3
3
4
·
FeCl –IL–SiO
H O , CH CN, NH H O, 30 °C
This work
4
2
2
2
3
3
2
a
Isolated yield
Scheme 3 Possible mechanism
for the oxidation of benzyl
alcohol to benzonitrile
proceeded slowly, and even under more drastic reaction
conditions, the reactions were still incomplete (Table 4,
entries 11 and 12). In addition, electron-rich aromatic alco-
hols afforded a higher yield than the electron-deficient aro-
matic alcohols, and it was observed that electron-donating
groups on the phenyl ring of aromatic alcohols favored the
formation of the corresponding products in excellent yields
(Table 4, entries 2–4). In contrast, electron-withdrawing
groups associated with aromatic alcohols slightly decreased
the reactivity of the substrate (Table 4, entries 5 and 6).
1
3

2
42
J IRAN CHEM SOC (2017) 14:233–243
Table 4 Oxidative conversion
of various alcohols to nitriles
Yield (%)a
Entry
1
Substrate
Product
Time (h)
3
References
[17]
90
2
3
3
3
92
94
[18]
[18]
4
5
3
4
93
83
[36]
[19]
6
7
4
3
81
89
[20]
[18]
8
9
3
3
87
91
[19]
[36]
1
0
3
85
[36]
1
3

J IRAN CHEM SOC (2017) 14:233–243
243
Table 4 continued
Yield (%)a
Entry
Substrate
Product
Time (h)
8
References
[36]
1
1
76b
1
2
8
72b
[36]
Unless otherwise noted, the reactions were carried out with alcohol (10 mmol), 30 % H O (21 mmol),
2
2
·
NH H O (30 mmol), FeCl –IL–SiO (0.5 g), and CH CN (10 mL) at 30 °C
3
2
4
2
3
a
Isolated yield
b
The reaction was carried out at 50 °C
1
1
1
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